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Mechanisms of Invasion in Head and Neck Cancer.

The ability of tumors to invade into surrounding tissues is a "hallmark of cancer" (1) and is arguably the property that most greatly affects morbidity and mortality. The head and neck region is very complex, with a dense organization of fascial planes, bony and cartilaginous scaffolding, and abundant neurovascular structures. On one hand, this complex anatomy poses several barriers for an invasive tumor to overcome. However, these structures, when breached, can provide insidious pathways for cancer cells to travel, cause damage, and evade treatment. From a clinical perspective, levels of invasion affect prognosis and are, therefore, considered both in the current cancer staging system and in the decision-making process for determining treatment.

THE CLINICAL RELEVANCE OF INVASION

Head and neck squamous cell carcinoma (HNSCC) is an epithelial cancer, arising from the mucosa of the upper aerodigestive tract. Therefore, an invasive cancer, by definition, must first invade the basement membrane of the native epithelium. This property is achieved during the process of carcinogenesis when multiple genetic insults are accumulated, and in turn, the acquisition of invasive capabilities allows invasion through the basement membrane. This primary event of invasion differentiates carcinoma in situ from invasive carcinoma. In oral tongue cancer, when this layer of connective tissue is breached, the invading tumor encounters the underlying tongue musculature. Depth of invasion for these tumors is directly associated with patient outcome, and when the depth of invasion approaches 2 to 4 mm, the rate of lymph node metastasis increases greatly, and prognosis worsens. (2-4) Therefore, elective neck dissection is recommended for oral tongue cancers with a depth of invasion of more than 2 to 4 mm, even when no clinical evidence of lymph node spread exists. A modified staging system has been developed that integrates depth of invasion into the T category of the currently accepted American Joint Committee on Cancer TNM staging. (3,5) Depth of invasion was significantly associated with disease-specific survival in oral squamous cell carcinoma (OSCC). (3)

In addition to depth of invasion, analysis of histologic parameters in resected tumors has indicated that invasion of tumor cells into the normal host tissue can predict patient outcome. The invasive front of an invading tumor is an important indicator of patient prognosis. (2,6-10) Bryne et al (10) developed an invasive-front grading system for tumors, which incorporates 4 parameters: (1) the pattern of invasion, (2) the degree of keratinization, (3) nuclear polymorphism, and (4) host response (inflammatory cell infiltration). (9) The scores for each parameter were combined to yield a total malignancy score for the whole tumor. The worst part of the tumor (most invasive) was used for the assessment. A higher malignancy score meant a poorer prognosis. Sandu et al (2) used the invasive-front grading system described by Bryne et al (10) and found that patients with a higher invasive-front grading system score had significantly lower diseasefree survival. Brandwein-Gensler et al (6) found the histologic parameter--the pattern of invasion--to predict patient outcome in patients with OSCC as part of their risk assessment model. (8) The worst pattern of invasion was significantly associated with overall survival, as well as local recurrence. (6,8) Li et al (7) demonstrated that this risk model predicted local recurrence and disease-specific survival in an independent study for patients with low-stage OSCC.

Bone and cartilage are ensheathed in a dense layer of connective tissue. Therefore, the mandible has a natural barrier to tumor invasion. If a mandible cancer is able to breach the mandibular periosteum and invade the bony cortex, the relatively uninhibited spread of tumor in the bone marrow space can lead to extensive involvement and ill-defined tumor margins with poor prognosis. (11-14) The presence of mandibular invasion places a tumor in an advanced primary stage (T4a) and an overall stage (IV) according to the American Joint Committee on Cancer staging system. (11) Similar to invasion of OSCCs into surrounding normal tissue, the histologic pattern of invasion by OSCC into bone can also be assessed and correlated with outcome. Invasion into bone displaying a broad pushing front and a sharp interface between tumor and bone is categorized as an erosive pattern. Projections of tumor cells along an irregular front with residual bone islands within the tumor are categorized as an infiltrative pattern. (11-14) A retrospective study of patients with mandibular invasion by OSCC found that patients with an infiltrative pattern of invasion into the bone had a 4-fold increased risk of death with disease compared with patients who displayed an erosive pattern of invasion. (13) The infiltrative pattern of invasion into bone tissue is associated with more-aggressive tumor behavior, increased likelihood of positive margins, recurrence, death with disease, and shorter disease-free survival. (11-13) Tumors with mandibular spread are generally treated aggressively, most often with segmental mandible resection, followed by postoperative radiation or chemoradiation. Similarly, the laryngeal cartilage poses a barrier to tumor spread. A cancer of the larynx that exhibits frank cartilage destruction is deemed a T4/stage IV cancer by American Joint Committee on Cancer criteria. If extensive cartilage invasion is present, often an organ-sparing approach with chemoradiation is not feasible, and laryngectomy with postoperative adjuvant therapy is the treatment of choice.

Another feature that HNSCC can exhibit is a propensity for invasion into neural structures. The head and neck region is populated by a rich network of innervation. The hypoglossal nerve extensively innervates the fine musculature of the tongue, whereas the lingual nerve provides a network for tongue sensation and carries distal fibers from the chorda tympani to provide special sensory taste fibers. The mandible carries the V3 branch of the trigeminal nerve, which innervates the teeth and transits to the mental foramen and provides sensation to the buccal mucosa of the lower lip and the skin of the chin. Similarly, the pharynx and larynx are innervated by vagus nerve fibers and branches of the glossopharyngeal nerve. When tumor cells invade the perineurium and nerve sheaths, the cranial nerves can essentially provide a direct route of spread toward the base of the skull and intracranial extension. This is particularly evident for adenoid cystic carcinoma of the salivary gland, which has a very high affinity for perineural spread. In addition, HNSCC commonly exhibits perineural invasion, and this feature has been cited as a harbinger for an increased rate of locoregional recurrence and poor outcome.

Brandwein-Gensler et al (6) found that perineural invasion (PNI) of small and large nerves was associated with reduced overall survival, and PNI of large nerves was specifically associated with local recurrence. To independently assess another set of OSCC cases, de Matos et al (15) applied the same criteria (6,8) and found a significant, positive correlation between PNI and the pattern of invasion, as well as between the pattern of invasion and tumor thickness, or depth of invasion. (3) High levels of nerve growth factor have been correlated with PNI and worse survival. (16) When perineural spread is identified after surgical resection, this feature can influence the decision to administer postoperative adjuvant treatment. Clinicians have evaluated PNI as an indicator in patients with early stage (I and II) OSCC tumors to determine treatment strategies, but PNI and lymphovascular invasion were not significant risk factors for disease-free or overall survival. (17)

The clinical significance of invasive properties is not limited to local disease. In regional lymph node metastases, invasion outside of the lymph node capsule is associated with poor outcome. (18,19) Two large, randomized clinical trials demonstrated that extracapsular spread of lymph node disease, identified after surgical resection, is an indication for maximized treatment with postoperative radiation and concurrent cisplatin. (20)

The strategies that cancer cells use to achieve all the invasive properties highlighted above likely require genetic and molecular alterations that are highly complex. The details of how these cancers acquire the ability to invade normal, organized, anatomic structures are being revealed. An improved understanding of the molecular events that lead to these invasive phenotypes may provide insight that could improve both prognostication and treatment. The following sections summarize

what is known about the mechanisms of invasion of the head and neck by cancer cells.

CELL SURFACE RECEPTORS INFLUENCE INVASIVE BEHAVIOR IN HNSCC

The best-characterized receptor for stimulation of HNSCC invasion is the epidermal growth factor receptor (EGFR; Figure 1). (21-26) Epidermal growth factor (EGF) is present in saliva at concentrations of about 1 ng/mL. (27-29) These concentrations (30,31) or higher (32-39) are able to stimulate migration and invasion in oral carcinoma lines in vitro, as well as in vivo. (40) Other EGFR ligands besides EGF have been shown to stimulate invasion, including transforming growth factor [alpha] (TGF[alpha]), betacellulin, heparin-binding EGF-like growth factor (HB-EGF), and amphiregulin (AREG). (32) Conversely, inhibition of the EGFR blocks invasion in response to EGF. (32,37,41-43) Intriguingly, EGFR also mediates invasion induced by some other receptors, notably G protein-coupled receptors (GPCRs) (44) for lysophosphatidic acid (LPA), (45,46) bradykinin, prostaglandin E2, (47) and gastrin-releasing peptide. (48) In some cases, the mechanism of crossactivation of EGFR by GPCRs has been identified as the release of EGFR ligands. The EGFR ligands are initially produced as cell-surface transmembrane proteins, (49) which can then be released from their transmembrane tethers by members of a disintegrin and metalloproteinase (ADAM) family of proteases. (50) The ADAM17 mediates the stimulated release of TGF[alpha] by bradykinin and prostaglandin E2. (47) Gastrin-releasing peptide stimulates the release of both AREG and TGF[alpha]. (48) In the case of gastrin-releasing peptide,

EGFR ligand release involves a pathway in which Src activates phosphatidylinositol 3-kinase (PI3K), leading to phosphoinositide-dependent kinase 1 activation and phosphorylation of ADAM17. (51) Estrogen-receptor activation can also trigger EGFR ligand release. (30) In addition, autocrine release of AREG, HB-EGF, betacellulin, and TGF[alpha] occur during serum starvation, (48,52-55) indicating that autocrine stimulation of EGFR can contribute to basal invasion capability.

A number of other receptors that can regulate HNSCC invasion have been identified. Other GPCRs that stimulate invasion with extracellular signal-regulated kinase (ERK) and matrix metalloproteinase 9 (MMP-9) activation include chemokine (C-X-C motif) receptors CXCR1 and CXCR2 (56,57) and CXCR4. (58,59) Interleukin (IL) 6 receptors can activate the ERK and c-JUN N-terminal kinase pathways. (60,61) Toll-like receptors have also been shown to stimulate invasion with activation of the nuclear factor of k light chain polypeptide gene enhancer in B cells (NF-[kappa]B) pathway. (62,63) The NF-[kappa]B signaling can synergize with the ERK/activator protein 1 (AP-1) pathways to stimulate invasion. (64,65) Wingless-type MMTV integration site family member 5B (WNT5B) knockdown suppresses MMP-10 production and invasion indicating that the WNT signaling pathways can also contribute to invasion. (66,67)

Transforming growth factor [beta] (TGF[beta]) can be produced by tumor-associated fibroblasts (68) and induce NF-[kappa]B activation (69) and SMAD-dependent MMP production, (70) as well as epithelial to mesenchymal transition (EMT) factors, such as Snail and Slug. (71-76) Invasion is stimulated by hypoxia in a Notch-dependent fashion. (77) Inhibition of Notch can also suppress MMP production. (78)

SIGNALING PATHWAYS INVOLVED IN HNSCC INVASION

Several signaling pathways have been shown to be important for invasion of HNSCC. Inhibition of ERK results in reduced invasion. (37,41,79) An important ERK target is AP-1, (80) which can increase transcription of MMPs, such as MMP-9. (79,81,82) The PI3K activity is also important for invasion. (37,79,83,84) Inhibition of PI3K also results in reduced MMP-9 expression. (37,79) Additional contributions of PI3K to invasion can occur through AKT stimulating Slug and Snail expression to enhance EMT (85,86) or through phosphorylation of ezrin (87) and yes-associated protein. (88) Phospholipase C [gamma]1 is important in EGFR-induced invasion in some cases, (79,89) potentially in a complex with c-Src. (35) The Src family members can contribute to invasion either through enhanced release of receptor ligands as described above or through stimulation of invadopod formation, which is described in more detail below. (48,55,90-94) A number of HNSCC cell lines have constitutively high levels of Rac1 activity, and inhibition of Rac activity results in reduced invasion capability. (95) In most cases, the increased Rac1 activity correlated with increased tyrosine phosphorylation of the Rac GEF Vav2 induced by EGFR, but an alternative pathway used Ras activation. The role of the Janus kinase (JAK)-signal transducer and activator of transcription (STAT) pathway in HNSCC invasion is complex. STAT3 is important for ligand-independent invasion induced by the EGFR vIII isoform, (96) but JAK2-STAT5a signaling is important for erythropoietin (EPO)-induced invasion but not EGF-induced invasion. (96) STAT3 activity may generally enhance invasion capability through suppression of phosphatase and tensin homolog (PTEN) (97) and E-cadherin. (98)

PROTEASES IMPLICATED IN HNSCC INVASION

A key distinction between migration and invasion is the ability to degrade extracellular matrix (ECM) barriers in the latter activity. Thus, expression of proteases, especially MMPs, is important for HNSCC invasion in many cases. (99) The most commonly identified MMP has been MMP-9. Its activity is increased by EGFR (32,37,42,54,100-102) and integrins, (75) and its inhibition reduces invasion. (81,103,104) In addition, MMP-9 can degrade type IV collagen, (105-107) a key constituent of the basement membrane, and thus has the potential for an important role in enabling HNSCC cells to become frankly invasive. Analysis of OSCC cases by immunohistochemistry revealed that expression of MMPs corresponded to areas with loss of type IV collagen [alpha] chain. The enzymatic activity of MMPs was assessed by zymography and was enhanced in higher-grade OSCC and along the advancing tumor front. (108) MMP-9 is used as a marker of invasive OSCC in many studies, and the extent of its expression is related to the infiltration pattern of squamous cell carcinoma at the invasive front. (109) In vitro invasion assays that use Matrigel, which is derived from basement membranes, often show a dependence on MMP-9 activity. However, MMP-9 can cleave other proteins exposed to the extracellular milieu as well, activating ligands such as TGF[beta] and chemokines as well as cleaving cell surface receptors. (110) In addition, MMP-9 may be involved in cleavage of E-cadherin, resulting in reduced cell-cell adhesion and increased invasion. (37)

MMP-2 is another MMP that has been implicated in HNSCC invasion. (103,104) Although MMP-2 and MMP-9 are secreted MMPs, the transmembrane protease membranetype 1 MMP (MT1-MMP) also has a significant role. MT1-MMP, together with the tissue inhibitor of metalloproteinases 2, (111,112) is important in the activation of secreted proteases, such as MMP-2, (113) and suppression of MT1-MMP reduces overall matrix degradation activity (114) and invasion. (43) Another protein that enhances protease activity and is important for invasion is ECM metalloprotease inducer (EMMPRIN). (100,115-117) Although the mechanism is unclear, EMMPRIN homophilic binding induces the expression of a number of proteases, including MMPs, cathepsin B, and urokinase plasminogen activator receptor (uPAR). (100,115,117,118) Other proteases that have been shown to contribute to HNSCC invasion include MMP-10, (66) MMP-13, (80) matriptase, (119) fibroblast activation protein, (120) and uPA/ uPAR, (117,121-124) as well as the glycosidase heparanase. (125)

THE ROLES OF ADHESION IN HNSCC INVASION

Cell-cell adhesion mediated by E-cadherin generally inhibits invasion. (26,126) Induction of cell-cell junctions can inhibit invasion. (127) Reduction in E-cadherin expression can occur through methylation of the promoter, and demethylating agents, which reverse this, can enhance invasion. (128) Inhibition of the E-cadherin function also enhances invasion. (129) However, the inhibitory effect of E-cadherin may be overcome by expression of other invasion-inducing proteins. (130,131) Desmosomes are another cell-cell adhesion structure, which can suppress invasion. (132) However, over-expression of certain adhesion proteins, such as claudin 1 (133) and desmoglein 3, (134) can enhance invasion.

Although degradation of the ECM, especially the basement membrane, is a key property of invasive tumors, interaction with the ECM is also important for invasion and prognosis. (135-138) Knockdown of the integrin [beta]1 using short interfering RNA (siRNA) can reduce MMP-2 activity and invasive capability, (139) mimicking the ability of miR-124, which has been shown to target integrin [beta]1 and reduce invasion. (140) The integrin [[alpha].sub.v][beta]6 is upregulated in wound healing, and inhibition of integrin [[alpha].sub.v][beta]6 also inhibits invasion. (141-143) Integrin [[alpha].sub.v][beta]6 is important to inducing protease expression. (142,144) Conversely, expression of specific ECM proteins, such as collagen I, (145) collagen XVI, (146,147) or laminin, (148) can enhance invasion. Binding of integrins to these matrix molecules triggers a signaling cascade, including integrin-linked kinase (ILK), (149) talin, (92,150) focal adhesion kinase (FAK), (151-153) and Src family members, (90,154) which then link to the MAP kinase and PI3 kinase pathways for stimulation of MMPs. (82,145,149,154) It is unclear why both growth factor signaling and adhesion signaling are needed for invasion--the connection between adhesion and growth factor signaling in invadopod formation is an active area of investigation. (155-159)

MicroRNAs THAT REGULATE HNSCC INVASION

MicroRNAs (miRNAs) are a class of gene-expression regulators that often have altered expression in various human cancers, including HNSCC. (160-165) The MiRNAs have emerged as having key roles in diverse cellular processes, including cancer cell proliferation, migration, invasion, and metastasis. (160,161,166,167) Dicer, a key enzyme involved in siRNA and miRNA function, was reduced in expression in tongue squamous cell carcinoma lines, and reduction of Dicer led to increased cell proliferation and invasion. (168) Consistent with these observations, most miRNAs that affect invasion in HNSCC are inhibitory (see Table 1).

The targets of the miRNAs identified thus far can be categorized according to the various functions involved in invasion. Many miRNAs target proteins associated with signal transduction, including ligands, receptors, and intracellular regulators. MiR-126 down-regulates protein levels of ligands epidermal growth factorlike domain 7 (EGFL7), vascular endothelial growth factor (VEGF), and basic fibroblast growth factor (FGF2). (169) Dickkopf 2 (DKK2), a target of miR-21, promotes cell invasion by antagonizing Wnt/[beta]-catenin signaling. (170) MiR-99a is a metastasis suppressor in OSCC by regulating expression of the insulin-like growth factor 1 receptor (IGF1R). (171) The regulation of neurofibromin 1 (NF1) by miR-193b impaired cell migration and invasion via inhibiting ERK1/2 phosphorylation. (172) MiR-155 promotes the migration and invasion of laryngeal squamous cell carcinoma. Knockdown of miR-155 in laryngeal squamous cell carcinoma cells suppressed invasion by negatively regulating suppressor of cytokine signaling 1 (SOCS1), which allowed increased STAT3 signaling. (173) HNSCC cells overexpressing miR-107 had reduced cell invasion in vitro and tumor growth in vivo resulting from the targeting of protein kinase C epsilon (PRKCE). (174)

Many adhesion proteins are also targets of miRNAs. Laminin, beta 3 (LAMB3), a component of laminin-332 in the ECM, is targeted by miR-218. (175) The miR-29s (miR-29a, miR-29b, and miR-29c) target another component of laminin-322, laminin, gamma 2 (LAMC2). (148) The miR-29s also target adhesion molecule integrin, alpha 6 (ITGA6). (148) In addition, miR-29a was found to upregulate the ECM protease MMP2. (176) ADAM10, another protease, is a target of miR-140-5p. (177) There is also a significant group of miRNAs whose targets are associated with cell protrusions and the cytoskeleton, including transgelin 2 (TAGLN2), targeted by miR-1, (178) moesin (MSN), and actin-related protein 2/3 complex, subunit 5 (ARPC5), targeted by miR-133a, (179,180) and podoplanin (PDPN) targeted by miR-363. (181) The cytoskeleton proteins ras homology family member C (RHOC) and Rho-associated, coiled-coil containing protein kinase (ROCK2) are targeted by miR-138, which also targets the EMT-associated protein vimentin (VIM). (184,185) Other miRNA targets associated with EMT for general gene expression are twist basic helix-loop-helix transcription factor 1 (TWIST1) and forkhead box C1 (FOXC1), targeted by miR-181a and miR-639. (186,187)

Transcription factors that may regulate genes associated with motility and invasion are also targets of miRNAs. MiR-29b suppresses specificity protein 1 (SP1) expression, which impairs OSCC invasion via reduced Akt activation. (188) MiR-375 targets metadherin (MTDH) (189-193) and miR-504 targets forkhead box P1 (FOXPl), (194) also important for invasion. Finally, there is a small group of targets whose direct function in invasion are unclear, such as programmed cell death 4 (PDCD4), (195) targeted by miR-21, BCL2 binding component 3 (BBC3), (196) and mitochondrial superoxide dismutase 2 (SOD2), (197) targeted by miR-222.

INVADOPODIA AS MEDIATORS OF HNSCC INVASION

Invadopodia (Figure 2) are specialized, actin-rich structures that mediate ECM proteolysis and are thought to have a key role in cell invasion. (198-201) An important component and marker of invadopodia is cortactin. The HNSCC cells that have band 11q13 amplification and subsequently overexpress cortactin have elevated binding and activity of Arp2/3 complex together with increased HNSCC cell motility and invasion. (202) The EGFR inhibitor, gefitinib, impairs motility in HNSCC cells with the degree of inhibition positively correlated with the level of cortactin in the cells. (202) High levels of cortactin reduce EGFR down-regulation and extend ERK activation. (203) Cortactin is important for both invadopodium assembly and ECM degradation. (204) Cortactin was shown to promote MMP-2 and MMP-9 secretion, as well as the cell surface levels of MT1-MMP in invadopodia of HNSCC cells. (204) Figure 3 shows an example of an in vitro assay to assess invadopodial matrix degradation, with cortactin and tyrosine kinase substrate with 5 SH3 domains (Tks5) as markers for invadopodia.

Src is an important regulator of invadopodium formation and activity. Saracatinib, an Src inhibitor, inhibited Src activation and phosphorylation of FAK, p130 Crk-associated substrate and cortactin in HNSCC cells along with reduction of invadopodia formation, ECM degradation, and MMP-9 secretion. (91) Intriguingly, although constitutively active Src induces invadopodium formation, wild-type Src expression is also needed in HNSCC cells for invadopodium-associated matrix degradation. (205) Abelson (Abl) kinase activity diminishes invadopodial ECM degradation in HNSCC cells: The inhibition of Abl and Arg by imatinib, an Abl family inhibitor, led to EGFR activation through increased HB-EGF production and shedding, and because of increased EGFR signaling, Src and ERK activity induced tyrosine and serine phosphorylation of cortactin. (55) These findings differ from a proposed model of EGFR-invadopodia signaling in breast cancer where elevated EGFR signaling induces Src activation, which subsequently leads to activation of Abl/Arg and tyrosine phosphorylation of cortactin by Abl/Arg. (206) In addition to the EGFR, (207) TGF[beta] receptor 1 can induce invadopodium formation through stimulation of insulinlike growth factor II messenger RNA (mRNA) binding protein 3 and podoplanin, both of which are important for invadopodium formation, ECM degradation, and MMP-9 activity. (73,208)

PI3K activity also regulates the formation and activity of invadopodia. (209,210) In breast cancer cell lines, PI3K signaling induces formation of invadopodia, and specifically, the p100[alpha] catalytic subunit of PI3K was responsible for the effect. (210) In HNSCC cells, the mechanism of PI3K signaling differs from the breast cancer model. (209) LY294002, a PI3K inhibitor, suppressed invadopodia numbers and ECM degradation, as well as focal adhesion numbers and size. Stimulation of invadopodia by PI3K may be due in part to production of PI(3,4)[P.sub.2] (phosphatidylinositol [3,4]-bisphosphate) from PIP3 (phosphatidylinositol [3,4,5]-trisphosphate) through the action of SH2-containing inositol 5'-phosphatase. (209) Expression levels of formin homology domain protein 1 (FHOD1), an actin nucleating protein, are dependent on PI3K. (211) Silencing FHOD1 reduced cell migration, invasion, invadopodium formation, and invadopodium-mediated ECM degradation. (211) Protein kinase C [alpha] (PKC-[alpha]) can provide feedback negative regulation of cells with mutant PI3K, although in cells with wild-type PI3K, PKC-[alpha] appears to stimulate invadopodium formation. (209)

Adhesion signaling is also important for invadopodium formation and maturation. Adhesion rings form around invadopodia and are recruited after invadopodium formation. (114) Integrin activity and ILK are needed for adhesion ring formation, MT1-MMP accumulation in invadopodia, and invadopodia-associated ECM degradation. (114) Although MT1-MMP is necessary for ECM degradation, it is not necessary for adhesion ring formation. Invadopodia are key docking sites for multivesicular endosomes containing smaller, secreted vesicles, termed exosomes. Invadopodia are also secretion sites for exosomes, (212) which promote invadopodia formation, enable the exocytosis of MT1-MMP at invadopodia, and stimulate invadopodia-associated matrix degradation. (212)

EPITHELIAL TO MESENCHYMAL TRANSITION AND CANCER STEM CELLS IN HNSCC INVASION

Epithelial to mesenchymal transition is a highly regulated process in which epithelial cells acquire a mesenchymal morphology through coordinated changes in gene and protein expression that lead to decreased cell adhesion and cell polarity, resulting in a more-invasive phenotype. (26,213-219) Common protein indicators of EMT are decreased expression of E-cadherin, and increased expression of N-cadherin and vimentin. The expression of these genes is controlled by transcription factors, including Snail, the zinc finger family of transcription factors (ZEB), and Twist. There are also changes in cellular proteins, such as integrins and [alpha]-smooth muscle actin, as well as ECM proteins, such as collagen, laminin, and fibronectin. (149,213-216,220-223) The HNSCC cells that undergo EMT have been shown to be more invasive.* The loss of E-cadherin associated with EMT is an indicator of poor prognosis in HNSCC. (26)

Epithelial to mesenchymal transition can induce the generation of a subpopulation of cells, called cancer stem cells, which have the potential for tumor initiation. (225,226) Cancer stem cells exhibit the properties of self-renewal, potential to behave as tumor progenitor cells, and the ability to differentiate. (223,225-227) Cancer stem cells are slow-dividing and therefore often more resistant to chemotherapy. (225-227) Cancer stem cells are found in invasive fronts, and in many tumors are near the blood vessels. (217,223,225-227) Epithelial to mesenchymal transition can generate cells within tumors that have stemlike properties. (216,219,223,228) In head and neck cancer, Twist, a regulator of EMT, was found to induce expression of Bmi-1, a regulator of sternness. (219,228) Twist and Bmi-1 can act together to repress expression of E-cadherin and p16INK4a. Higher expression of Twist and Bmi-1 has been correlated with lower E-cadherin and p16INK4a and is associated with poor prognosis. (219)

There are many common molecules and pathways involved in invasion, EMT, and stemness. TGF[beta] regulates transcription of EMT transcription factors via SMADs. (229) CD44, a cell surface glycoprotein that binds hyaluronic acid, is involved in cell-cell crosstalk, cell adhesion, and migration and interacts with c-Met and EGFR. (227,230) Epidermal growth factor can induce EMT in HNSCC cell lines through PI3K/ Akt signaling. (223) Expression of Bmi-1, aldehyde dehydrogenase, and CD44 also increases with EGF treatment, indicating an acquisition of stemlike properties. Notch signaling can induce EMT under hypoxic conditions, with increased expression of Notch pathway molecules and Snail, decreased expression of E-cadherin, and an increase in invasiveness. (77) In addition to inducing EMT and increased invasiveness, Snail has also been shown to induce stem-like properties in OSCC. (224) Adhesion-related signaling molecules that are important for EMT and invasion include ILK (149) and FAK. (152) For proteases, MT1-MMP has been shown to induce EMT and stemlike properties in OSCC, as well as invasion, in parallel with increased levels of Twist and ZEB. (221) However, there may be subtypes of cancer stem cells, which differ in their invasive ability. (231)

One aspect of invasion that needs more examination in HNSCC is collective invasion, in which cell-cell contacts may be maintained during invasion. Three-dimensional reconstructions of the invasive front of 14 oral tongue SCCs revealed that most invasive tumor cells are in multicellular structures of variable size, (232) suggesting the presence of cell-cell contacts. There is an ongoing debate regarding the relative importance of single cell and collective invasion for patient prognosis. One possibility is that a partial EMT could maintain cell-cell contacts but stimulate invasive properties sufficient to generate a more aggressive tumor that results in a worse prognosis. (233)

TUMOR MICROENVIRONMENT AND INVASION

Cancer-associated fibroblasts are the major stromal cells present in the microenvironment of HNSCC, and they tend to be myofibroblasts showing increased expression of [alpha]-smooth muscle actin. (234-237) Myofibroblasts and cancer-associated fibroblasts have been shown to enhance HNSCC invasion in vitro in a variety of assays. (238-247) Treatments that can enhance the ability of fibroblasts to stimulate tumor cell invasion include irradiation (182) and reactive oxygen species, (183,248,249) as well as lifestyle-correlated factors, such as cigarette smoke (250) and areca nut extract. (251) Fibroblasts have been shown to stimulate tumor cell invasion through secretion of a number of factors, including chemokine (CC motif) ligand 2 (CCL2), (183,252) CCL7, (253) stromal cell-derived factor-1 (SDF-1), (254) TGF[beta], (73,248,249,255,256) IL-33, (257) MMP-2, (145,249-251,258,259) EGFR ligands, (260) and hepatocyte growth factor (HGF). (254,261-265) Cancer-associated fibroblasts can also produce ECM molecules that enhance invasion, such as thrombospondin 1266 and fibronectin. (267) The mechanism of stimulation of tumor cell invasion by cancer-associated fibroblasts can include induction of EMT. (245,268)

In several studies, a paracrine interaction between tumor cells and fibroblasts has been shown to stimulate invasion. For example, CCL2 from fibroblasts can stimulate invasion and reactive oxygen species production by tumor cells, which, in turn, stimulates fibroblast senescence and CCL2 production from the fibroblasts. (183) Galectin production by tumor cells can also stimulate CCL2 production from fibroblasts. (252) Interleukin 1 from OSCC stimulates CCL7, HGF, and TGF[beta] production by fibroblasts, (73,253,265) whereas endothelin stimulates ADAM17-mediated release of EGFR ligands. (246,260) Interestingly, there is a report of TGF[beta] from tumor cells inducing HGF production by fibroblasts as well. (264)

Other features of the tumor microenvironment have also been identified as stimulating HNSCC invasion, although not as thoroughly as cancer-associated fibroblasts. The perivascular niche has been associated with cancer stem cells and invasion. (227) Endothelial cells can secrete EGF to induce EMT and invasion. (223) Tumor-associated endothelial cells have been shown to stimulate invasion of HNSCC cells in vitro through the secretion of IL-8269 and CXCL1. (270) These chemokines are produced and secreted upon stimulation of endothelial cells by VEGF via BCL2 upregulation. (269,271) Macrophages have been shown to stimulate Axl-mediated invasion (272) and perineural invasion through production of glial cell-derived neurotrophic factor (GDNF). (273) However, macrophages did not enhance invasion in response to EGF in an in vivo invasion assay. (40) Hypoxia in the tumor microenvironment can induce Notch and EMT factors, such as Slug and Snail, to increase invasion. (77,274) In addition, MMP-9 can be induced by hypoxia to enhance invasion in a [Na.sup.+]/[H.sup.+] exchanger 1-dependent fashion. (275) Hypoxia-inducible factor 2a leads to EGFR activation, (276) whereas hypoxia-inducible factor 1a increases integrin [alpha]5 and fibronectin (277) in invasion. Of concern for treatments using EPO to mitigate chemotherapy side effects, hypoxia can induce the EPO receptor in tumor cells, enabling EPO to stimulate tumor cell invasion. (278)

GENOMIC CHANGES IN INVASION-ASSOCIATED GENES

DNA changes, such as mutations and copy number variations (CNVs) at the genomic level have been implicated in cancer progression. (279) Higher numbers of CNVs in the genome are associated with the development of cancer, and more CNVs are accumulated with tumor progression. (279) In HNSCC, disease-specific survival and recurrence can be predicted by CNVs. (280) We used HNSCC TCGA (The Cancer Genome Atlas, National Cancer Institute Center for Bioinformatics, Bethesda, Maryland) data downloaded from the UCSC Cancer Genomics Browser (University of California, Santa Cruz) to evaluate the genes discussed in this review. (281) The 25 genes with the greatest CNVs or number of mutations in HNSCC discussed here are presented in Table 2. PIK3CA is highest in copy number increase and second in mutations, with EGFR and RACI also being high in both mutations and copy number increases, emphasizing the potential importance of these genes in HNSCC.

CONCLUSIONS

Studies of invasion have identified a number of possible applications in the treatment of HNSCC. The most straightforward approach is to develop specific inhibitors targeted to molecules that are identified as being important in invasion. In particular, proteases, such as MMP-2, MMP9, and MT1-MMP, are commonly identified as being important for invasion and, thus, could be targeted for therapeutic development. However, there has been extensive development of broad-spectrum MMP inhibitors with very limited success. (282) Inhibition of the beneficial roles of MMPs resulted in unacceptable side effects, (283) and thus, there is now caution in considering therapeutics targeting MMPs, with the assumption that such treatments likely need to be brief to avoid side effects caused by longer-term treatments. (284) A possible use for brief treatments could be in counteracting the effects of radiation. Radiation has been found to induce migration and invasion, (285) and treatment with invasion inhibitors during radiation therapy could potentially enhance its efficacy. (286,287) Inhibitors targeting EGFR, (288) [Na.sup.+]/[H.sup.+] exchanger 1,275 Src, (91) and microtubules (289) can inhibit invasion at concentrations that are not toxic to cells and could be useful in counteracting radiation-induced spread.

For longer-term treatments, potentially lower-toxicity compounds for inhibiting invasion have been identified whose targets are unknown. These include extracts from herbs, green tea, and other natural sources. (41,101,290-300) Such compounds could constrain further tumor spread and extend patient survival without directly killing tumor cells. Limiting tumor spread could develop additional benefits because of the consequences of keeping tumor cells clustered together. As noted above, there is an intimate relationship between invasion, EMT, and stem cell properties. It is possible that by inhibiting invasion of HNSCC cells, there is partial reversion of EMT and loss of stemness, which could result in greater sensitivity to cytotoxic treatments. Compounds have been identified that, on their own, inhibit invasion and EMT without affecting viability, (292) but then sensitize HNSCC cells to cisplatin. (292,301) Identification of invasion inhibitors that can enhance sensitivity to chemoradiation while suppressing the spread of tumor cells would provide a valuable addition to the therapy options for patients with head and neck cancer.

Please Note: Illustration(s) are not available due to copyright restrictions.

References

(1.) Hanahan D, Weinberg RA. Hallmarks of cancer: the next generation. Cell. 2011; 144(5):646-674. doi:10.1016/j.cell.2011.02.013.

(2.) Sandu K, Nisa L, Monnier P, Simon C, Andrejevic-Blant S, Bron L. Clinicobiological progression and prognosis of oral squamous cell carcinoma in relation to the tumor invasive front: impact on prognosis. Acta Otolaryngol. 2014; 134(4):416-424. doi:10.3109/00016489.2013.849818.

(3.) Ebrahimi A, Gil Z, Amit M, et al; International Consortium for Outcome Research (ICOR) in Head and Neck Cancer. Primary tumor staging for oral cancer and a proposed modification incorporating depth of invasion: an international multicenter retrospective study. JAMA Otolaryngol Head Neck Surg. 2014; 140(12):1138-1148. doi:10.1001/jamaoto.2014.1548.

(4.) Spiro RH, Huvos AG, Wong GY, Spiro JD, Gnecco CA, Strong EW. Predictive value of tumor thickness in squamous carcinoma confined to the tongue and floor of the mouth. Am J Surg. 1986; 152(4):345-350.

(5.) Edge S, Byrd DR, Compton CC, Fritz AG, Greene FL, Trotti A, eds. AJCC Cancer Staging Manual. 7th ed. New York, NY: Springer; 2010.

(6.) Brandwein-Gensler M, Teixeira MS, Lewis CM, et al. Oral squamous cell carcinoma: histologic risk assessment, but not margin status, is strongly predictive of local disease-free and overall survival. Am J Surg Pathol. 2005; 29(2):167-178.

(7.) Li Y, Bai S, Carroll W, et al. Validation of the risk model: high-risk classification and tumor pattern of invasion predict outcome for patients with low-stage oral cavity squamous cell carcinoma. Head Neck Pathol. 2013; 7(3): 211-223. doi:10.1007/s12105-012-0412-1.

(8.) Brandwein-Gensler M, Smith RV, Wang B, et al. Validation of the histologic risk model in a new cohort of patients with head and neck squamous cell carcinoma. Am J Surg Pathol. 2010; 34(5):676-688. doi:10.1097/PAS. 0b013e3181d95c37.

(9.) Bryne M. Is the invasive front of an oral carcinoma the most important area for prognostication? Oral Dis. 1998; 4(2):70-77.

(10.) Bryne M, Boysen M, Alfsen CG, et al. The invasive front of carcinomas: the most important area for tumour prognosis? Anticancer Res. 1998; 18(6B): 4757-4764.

(11.) Jimi E, Shin M, Furuta H, Tada Y, Kusukawa J. The RANKL/RANK system as a therapeutic target for bone invasion by oral squamous cell carcinoma (Review). Int J Oncol. 2013; 42(3):803-809. doi:10.3892/ijo.2013.1794.

(12.) Jimi E, Furuta H, Matsuo K, Tominaga K, Takahashi T, Nakanishi O. The cellular and molecular mechanisms of bone invasion by oral squamous cell carcinoma. Oral Dis. 2011; 17(5):462-468. doi:10.1111/j.1601-0825.2010. 01781.x.

(13.) Wong RJ, Keel SB, Glynn RJ, Varvares MA. Histological pattern of mandibular invasion by oral squamous cell carcinoma. Laryngoscope. 2000; 110(1):65-72. doi:10.1097/00005537-200001000-00013.

(14.) Quan J, Johnson NW, Zhou G, Parsons PG, Boyle GM, Gao J. Potential molecular targets for inhibiting bone invasion by oral squamous cell carcinoma: a review of mechanisms. Cancer Metastasis Rev. 2012; 31(1-2):209-219. doi:10. 1007/s10555-011-9335-7.

(15.) de Matos FR, de Araujo Lima EdN, Queiroz LMG, da Silveira EJD. Analysis of inflammatory infiltrate, perineural invasion, and risk score can indicate concurrent metastasis in squamous cell carcinoma of the tongue. J Oral Maxillofac Surg. 2012; 70(7):1703-1710. doi:10.1016/j.joms.2011.08.023.

(16.) Shen WR, Wang YP, Chang JY, Yu SY, Chen HM, Chiang CP. Perineural invasion and expression of nerve growth factor can predict the progression and prognosis of oral tongue squamous cell carcinoma. J Oral Pathol Med. 2014; 43(4):258-264.

(17.) Chen TC, Wang CP, Ko JY, et al. The impact of perineural invasion and/or lymphovascular invasion on the survival of early-stage oral squamous cell carcinoma patients. Ann Surg Oncol. 2013; 20(7):2388-2395. doi:10.1245/ s10434-013-2870-4.

(18.) Bernier J, Domenge C, Ozsahin M, et al; European Organization for Research and Treatment of Cancer Trial 22931. Postoperative irradiation with or without concomitant chemotherapy for locally advanced head and neck cancer. N Engl J Med. 2004; 350(19):1945-1952. doi:10.1056/NEJMoa032641.

(19.) Cooper JS, Pajak TF, Forastiere AA, et al; Radiation Therapy Oncology Group 9501/Intergroup. Postoperative concurrent radiotherapy and chemotherapy for high-risk squamous-cell carcinoma of the head and neck. N Engl J Med. 2004; 350(19):1937-1944. doi:10.1056/NEJMoa032646.

(20.) Bernier J, Cooper JS, Pajak TF, et al. Defining risk levels in locally advanced head and neck cancers: a comparative analysis of concurrent postoperative radiation plus chemotherapy trials of the EORTC (#22931) and RTOG (# 9501). Head Neck. 2005; 27(10):843-850. doi:10.1002/hed.20279.

(21.) Silva SD, Alaoui-Jamali MA, Hier M, Soares FA, Graner E, Kowalski LP. Cooverexpression of ERBB1 and ERBB4 receptors predicts poor clinical outcome in pN+ oral squamous cell carcinoma with extranodal spread. Clin Exp Metastasis. 2014; 31(3):307-316. doi:10.1007/s10585-013-9629-y.

(22.) Kalyankrishna S, Grandis JR. Epidermal growth factor receptor biology in head and neck cancer. J Clin Oncol. 2006; 24(17):2666-2672. doi:10.1200/jco. 2005.04.8306.

(23.) Lim SC. Expression of c-erbB receptors, MMPs and VEGF in head and neck squamous cell carcinoma. Biomed Pharmacother. 2005; 59(suppl 2):S366-S369.

(24.) Rogers SJ, Harrington KJ, Rhys-Evans P, O-Charoenrat P, Eccles SA. Biological significance of c-erbB family oncogenes in head and neck cancer. Cancer Metastasis Rev. 2005; 24(1):47-69. doi:10.1007/s10555-005-5047-1.

(25.) Leemans CR, Braakhuis BJ, Brakenhoff RH. The molecular biology of head and neck cancer. Nat Rev Cancer. 2011; 11(1):9-22. doi:10.1038/nrc2982.

(26.) Pectasides E, Rampias T, Sasaki C, et al. Markers of epithelial to mesenchymal transition in association with survival in head and neck squamous cell carcinoma (HNSCC). PloS one. 2014; 9(4):e94273. doi:10.1371/journal. pone.0094273.

(27.) Thesleff I, Viinikka L, Saxen L, Lehtonen E, Perheentupa J. The parotid gland is the main source of human salivary epidermal growth factor. Life Sci. 1988; 43(1):13-18.

(28.) Dagogo-Jack S. Epidermal growth factor EGF in human saliva: effect of age, sex, race, pregnancy and sialogogue. Scand J Gastroenterol Suppl. 1986; 124:47-54.

(29.) Ino M, Ushiro K, Ino C, Yamashita T, Kumazawa T. Kinetics of epidermal growth factor in saliva. Acta Otolaryngol Suppl. 1993; 500:126-130.

(30.) Egloff AM, Rothstein ME, Seethala R, Siegfried JM, Grandis JR, Stabile LP. Cross-talk between estrogen receptor and epidermal growth factor receptor in head and neck squamous cell carcinoma. Clin Cancer Res. 2009; 15(21):6529-6540. doi:10.1158/1078-0432.ccr-09-0862.

(31.) Ohshima M, Sato M, Ishikawa M, Maeno M, Otsuka K. Physiologic levels of epidermal growth factor in saliva stimulate cell migration of an oral epithelial cell line, HO-1-N-1. Eur J Oral Sci. 2002; 110(2):130-136.

(32.) O-charoenrat P, Modjtahedi H, Rhys-Evans P, Court WJ, Box GM, Eccles SA. Epidermal growth factor-like ligands differentially up-regulate matrix metal-loproteinase 9 in head and neck squamous carcinoma cells. Cancer Res. 2000; 60(4):1121-1128.

(33.) Shiratsuchi T, Ishibashi H, Shirasuna K. Inhibition of epidermal growth factor-induced invasion by dexamethasone and AP-1 decoy in human squamous cell carcinoma cell lines. J Cell Physiol. 2002; 193(3):340-348. doi:10.1002/jcp. 10181.

(34.) Yeudall WA, Miyazaki H, Ensley JF, Cardinali M, Gutkind JS, Patel V. Uncoupling of epidermal growth factor-dependent proliferation and invasion in a model of squamous carcinoma progression. Oral Oncol. 2005; 41(7):698-708. doi:10.1016/j.oraloncology.2005.03.004.

(35.) Nozawa H, Howell G, Suzuki S, et al. Combined inhibition of PLCy-1 and c-Src abrogates epidermal growth factor receptor-mediated head and neck squamous cell carcinoma invasion. Clin Cancer Res. 2008; 14(13):4336-4344. doi:10.1158/1078-0432.CCR-07-4857.

(36.) Ohnishi Y, Lieger O, Attygalla M, Iizuka T, Kakudo K. Effects of epidermal growth factor on the invasion activity of the oral cancer cell lines HSC3 and SAS. Oral Oncol. 2008; 44(12):1155-1159. doi:10.1016/j.oraloncology.2008.02.015.

(37.) Zuo JH, Zhu W, Li MY, et al. Activation of EGFR promotes squamous carcinoma SCC10A cell migration and invasion via inducing EMT-like phenotype change and MMP-9-mediated degradation of E-cadherin. J Cell Biochem. 2011; 112(9):2508-2517. doi:10.1002/jcb.23175.

(38.) Lin MC, Huang MJ, Liu CH, Yang TL, Huang MC. GALNT2 enhances migration and invasion of oral squamous cell carcinoma by regulating EGFR glycosylation and activity. Oral Oncol. 2014; 50(5):478-484. doi:10.1016/j. oraloncology.2014.02.003.

(39.) Ohnishi Y, Watanabe M, Yasui H, Kakudo K. Effects of epidermal growth factor on the invasive activity and cytoskeleton of oral squamous cell carcinoma cell lines. Oncol Lett. 2014; 7(5):1439-1442. doi:10.3892/ol.2014.1946.

(40.) Smirnova T, Adomako A, Locker J, Van Rooijen N, Prystowsky MB, Segall JE. In vivo invasion of head and neck squamous cell carcinoma cells does not require macrophages. Am J Pathol. 2011; 178(6):2857-2865. doi:10.1016/j. ajpath.2011.02.030.

(41.) Sun Q, Prasad R, Rosenthal E, Katiyar SK. Grape seed proanthocyanidins inhibit the invasive potential of head and neck cutaneous squamous cell carcinoma cells by targeting EGFR expression and epithelial-to-mesenchymal transition. BMC Complement Altern Med. 2011; 11:134. doi:10.1186/ 1472-6882-11-134.

(42.) Lee EJ, Whang JH, Jeon NK, Kim J. The epidermal growth factor receptor tyrosine kinase inhibitor ZD1839 (Iressa) suppresses proliferation and invasion of human oral squamous carcinoma cells via p53 independent and MMP, uPAR dependent mechanism. Ann N Y Acad Sci. 2007; 1095:113-128. doi:10.1196/ annals.1397.015.

(43.) Oku N, Sasabe E, Ueta E, Yamamoto T, Osaki T. Tight junction protein claudin-1 enhances the invasive activity of oral squamous cell carcinoma cells by promoting cleavage of laminin-5 [gamma]2 chain via matrix metalloproteinase (MMP)-2 and membrane-type MMP-1. Cancer Res. 2006; 66(10):5251-5257. doi:10.1158/ 0008-5472.CAN-05-4478.

(44.) Liebmann C. EGF receptor activation by GPCRs: an universal pathway reveals different versions. Mol Cell Endocrinol. 2011; 331(2):222-231. doi:10. 1016/j.mce.2010.04.008.

(45.) Brusevold IJ, Tveteraas IH, Aasrum M, Odegard J, Sandnes DL, Christoffersen T. Role of LPAR3, PKC and EGFR in LPA-induced cell migration in oral squamous carcinoma cells. BMC Cancer. 2014; 14:432. doi:10.1186/ 1471-2407-14-432.

(46.) Gschwind A, Prenzel N, Ullrich A. Lysophosphatidic acid-induced squamous cell carcinoma cell proliferation and motility involves epidermal growth factor receptor signal transactivation. Cancer Res. 2002; 62(21):6329-6336.

(47.) Thomas SM, Bhola NE, Zhang Q, et al. Cross-talk between G protein-coupled receptor and epidermal growth factor receptor signaling pathways contributes to growth and invasion of head and neck squamous cell carcinoma. Cancer Res. 2006; 66(24):11831-11839. doi:10.1158/0008-5472.can-06-2876.

(48.) Zhang Q, Thomas SM, Xi S, et al. SRC family kinases mediate epidermal growth factor receptor ligand cleavage, proliferation, and invasion of head and neck cancer cells. Cancer Res. 2004; 64(17):6166-6173. doi:10.1158/ 0008-5472.can-04-0504.

(49.) Schneider MR, Wolf E. The epidermal growth factor receptor ligands at a glance. J Cell Physiol. 2009; 218(3):460-466. doi:10.1002/jcp.21635.

(50.) Kataoka H. EGFR ligands and their signaling scissors, ADAMs, as new molecular targets for anticancer treatments. J Dermatol Sci. 2009; 56(3):148-153. doi:10.1016/j.jdermsci.2009.10.002.

(51.) Zhang Q, Thomas SM, Lui VW, et al. Phosphorylation of TNF-[alpha] converting enzyme by gastrin-releasing peptide induces amphiregulin release and EGF receptor activation. Proc Natl Acad Sci U S A. 2006; 103(18):6901-6906. doi:10.1073/pnas.0509719103.

(52.) P OC, Rhys-Evans P, Eccles S. A synthetic matrix metalloproteinase inhibitor prevents squamous carcinoma cell proliferation by interfering with epidermal growth factor receptor autocrine loops. Int J Cancer. 2002; 100(5):527-533. doi:10.1002/ijc.10531.

(53.) Holz C, Niehr F, Boyko M, et al. Epithelial-mesenchymal-transition induced by EGFR activation interferes with cell migration and response to irradiation and cetuximab in head and neck cancer cells. Radiother Oncol. 2011; 101(1):158-164. doi:10.1016/j.radonc.2011.05.042.

(54.) Ohnishi Y, Inoue H, Furukawa M, Kakudo K, Nozaki M. Heparin-binding epidermal growth factor-like growth factor is a potent regulator of invasion activity in oral squamous cell carcinoma. Oncol Rep. 2012; 27(4):954-958. doi: 10.3892/or.2011.1616.

(55.) Hayes KE, Walk EL, Ammer AG, Kelley LC, Martin KH, Weed SA. Ableson kinases negatively regulate invadopodia function and invasion in head and neck squamous cell carcinoma by inhibiting an HB-EGF autocrine loop. Oncogene. 2013; 32(40):4766-4777. doi:10.1038/onc.2012.513.

(56.) Khurram SA, Bingle L, McCabe BM, Farthing PM, Whawell SA. The chemokine receptors CXCR1 and CXCR2 regulate oral cancer cell behaviour. J Oral Pathol Med. 2014; 43(9):667-674. doi:10.1111/jop.12191.

(57.) Qian Y, Wang Y, Li DS, et al. The chemokine receptor-CXCR2 plays a critical role in the invasion and metastases of oral squamous cell carcinoma in vitro and in vivo. J Oral Pathol Med. 2014; 43(9):658-666. doi:10.1111/jop. 12189.

(58.) Yu T, Wu Y, Helman JI, Wen Y, Wang C, Li L. CXCR4 promotes oral squamous cell carcinoma migration and invasion through inducing expression of MMP-9 and MMP-13 via the ERK signaling pathway. Mol Cancer Res. 2011; 9(2): 161-172. doi:10.1158/1541-7786.MCR-10-0386.

(59.) Watanabe H, Iwase M, Ohashi M, Nagumo M. Role of interleukin-8 secreted from human oral squamous cell carcinoma cell lines. Oral Oncol. 2002; 38(7):670-679.

(60.) Kanazawa T, Nishino H, Hasegawa M, et al. Interleukin-6 directly influences proliferation and invasion potential of head and neck cancer cells. Eur Arch Otorhinolaryngol. 2007; 264(7):815-821. doi:10.1007/s00405-007-0264-6.

(61.) Chuang JY, Huang YL, Yen WL, Chiang IP, Tsai MH, Tang CH. Syk/JNK/ AP-1 signaling pathway mediates interleukin-6-promoted cell migration in oral squamous cell carcinoma. Int J Mol Sci. 2014; 15(1):545-559. doi:10.3390/ ijms15010545.

(62.) Ren G, Hu J, Wang R, et al. Rapamycin inhibits Toll-like receptor 4-induced pro-oncogenic function in head and neck squamous cell carcinoma. Oncol Rep. 2014; 31(6):2804-2810. doi:10.3892/or.2014.3134.

(63.) Johnson J, Shi Z, Liu Y, Stack MS. Inhibitors of NF-[kappa]B reverse cellular invasion and target gene upregulation in an experimental model of aggressive oral squamous cell carcinoma. Oral Oncol. 2014; 50(5):468-477. doi:10.1016/j. oraloncology.2014.02.004.

(64.) Ruan M, Zhang Z, Li S, et al. Activation of Toll-like receptor-9 promotes cellular migration via up-regulating MMP-2 expression in oral squamous cell carcinoma. PloS One. 2014; 9(3):e92748. doi:10.1371/journal.pone.0092748.

(65.) Nottingham LK, Yan CH, Yang X, et al. Aberrant IKKa and IKKp cooperatively activate NF-[kappa]B and induce EGFR/AP1 signaling to promote survival and migration of head and neck cancer. Oncogene. 2014; 33(9):1135-1147. doi: 10.1038/onc.2013.49.

(66.) Deraz EM, Kudo Y, Yoshida M, et al. MMP-10/stromelysin-2 promotes invasion of head and neck cancer. PloS One. 2011; 6(10):e25438. doi:10.1371/ journal.pone.0025438.

(67.) Takeshita A, Iwai S, Morita Y, Niki-Yonekawa A, Hamada M, Yura Y. Wnt5b promotes the cell motility essential for metastasis of oral squamous cell carcinoma through active Cdc42 and Rho A. Int J Oncol. 2014; 44(1):59-68. doi: 10.3892/ijo.2013.2172.

(68.) Elahi M, Rakhshan V, Ghasemian NT, Moshref M. Prognostic value of transforming growth factor beta 1 [TGF-[beta]1] and matrix metalloproteinase 9 [MMP-9] in oral squamous cell carcinoma. Biomarkers. 2012; 17(1):21-27. doi: 10.3109/1354750X.2011.635804.

(69.) Freudlsperger C, Bian Y, Contag Wise S, et al. TGF-[beta] and NF-[kappa]B signal pathway cross-talk is mediated through TAK1 and SMAD7 in a subset of head and neck cancers. Oncogene. 2013; 32(12):1549-1559. doi:10.1038/onc.2012.171.

(70.) Leivonen SK, Ala-Aho R, Koli K, Grenman R, Peltonen J, Kahari VM. Activation of Smad signaling enhances collagenase-3 (MMP-13) expression and invasion of head and neck squamous carcinoma cells. Oncogene. 2006; 25(18): 2588-2600. doi:10.1038/sj.onc.1209291.

(71.) Sun L, Diamond ME, Ottaviano AJ, Joseph MJ, Ananthanarayan V, Munshi HG. Transforming growth factor-p1 promotes matrix metalloproteinase-9-mediated oral cancer invasion through snail expression. Mol Cancer Res. 2008; 6(1):10-20. doi:10.1158/1541-7786.MCR-07-0208.

(72.) Quan J, Elhousiny M, Johnson NW, Gao J. Transforming growth factor-beta1 treatment of oral cancer induces epithelial-mesenchymal transition and promotes bone invasion via enhanced activity of osteoclasts. Clin Exp Metastasis. 2013; 30(5):659-670. doi:10.1007/s10585-013-9570-0.

(73.) Hwang YS, Xianglan Z, Park KK, Chung WY. Functional invadopodia formation through stabilization of the PDPN transcript by IMP-3 and cancer-stromal crosstalk for PDPN expression. Carcinogenesis. 2012; 33(11):2135-2146. doi:10.1093/carcin/bgs258.

(74.) Munshi HG, Wu YI, Mukhopadhyay S, et al. Differential regulation of membrane type 1-matrix metalloproteinase activity by ERK 1/2- and p38 MAPK-modulated tissue inhibitor of metalloproteinases 2 expression controls transforming growth factor-[beta]1-induced pericellular collagenolysis. J Biol Chem. 2004; 279(37):39042-39050. doi:10.1074/jbc.M404958200.

(75.) Dang D, Yang Y, Li X, et al. Matrix metalloproteinases and TGF[beta]1 modulate oral tumor cell matrix. Biochem Biophys Res Comm. 2004; 316(3):937-942. doi:10.1016/j.bbrc.2004.02.143.

(76.) Takayama S, Hatori M, Kurihara Y, Kinugasa Y, Shirota T, Shintani S. Inhibition of TGF-[beta]1 suppresses motility and invasiveness of oral squamous cell carcinoma cell lines via modulation of integrins and down-regulation of matrix-metalloproteinases. Oncol Rep. 2009; 21(1):205-210.

(77.) Ishida T, Hijioka H, Kume K, Miyawaki A, Nakamura N. Notch signaling induces EMTin OSCC cell lines in a hypoxic environment. Oncol Lett. 2013; 6(5): 1201-1206. doi:10.3892/ol.2013.1549.

(78.) Yu B, Wei J, Qian X, Lei D, Ma Q, Liu Y. Notch1 signaling pathway participates in cancer invasion by regulating MMPs in lingual squamous cell carcinoma. Oncol Rep. 2012; 27(2):547-552. doi:10.3892/or.2011.1492.

(79.) O-charoenrat P, Wongkajornsilp A, Rhys-Evans PH, Eccles SA. Signaling pathways required for matrix metalloproteinase-9 induction by betacellulin in head-and-neck squamous carcinoma cells. Int J Cancer. 2004; 111(2):174-183. doi:10.1002/ijc.20228.

(80.) Chuang JY, Tsai CF, Chang SW, et al. Glial cell line-derived neurotrophic factor induces cell migration in human oral squamous cell carcinoma. Oral Oncol. 2013; 49(12):1103-1112. doi:10.1016/j.oraloncology.2013.08.009.

(81.) Nair RR, Avila H, Ma X, et al. A novel high-throughput screening system identifies a small molecule repressive for matrix metalloproteinase-9 expression. Mol Pharmacol. 2008; 73(3):919-929. doi:10.1124/mol.107.042606.

(82.) Bedal KB, Grassel S, Oefner PJ, Reinders J, Reichert TE, Bauer R. Collagen XVI induces expression of MMP9 via modulation of AP-1 transcription factors and facilitates invasion of oral squamous cell carcinoma. PloS One. 2014; 9(1): e86777. doi:10.1371/journal.pone.0086777.

(83.) Chen Y, Hou Q, Yan W, et al. PIK3CA is critical for the proliferation, invasiveness, and drug resistance of human tongue carcinoma cells. Oncol Res. 2011; 19(12):563-571.

(84.) Murugan AK, Hong NT, Fukui Y, Munirajan AK, Tsuchida N. Oncogenic mutations of the PIK3CA gene in head and neck squamous cell carcinomas. Int J Oncol. 2008; 32(1):101-111.

(85.) Okui G, Tobiume K, Rizqiawan A, et al. AKT primes snail-induced EMT concomitantly with the collective migration of squamous cell carcinoma cells. J Cell Biochem. 2013; 114(9):2039-2049. doi:10.1002/jcb.24545.

(86.) Hong KO, Kim JH, Hong JS, et al. Inhibition of Akt activity induces the mesenchymal-to-epithelial reverting transition with restoring E-cadherin expression in KB and KOSCC-25B oral squamous cell carcinoma cells. J Exp Clin Cancer Res. 2009; 28:28. doi:10.1186/1756-9966-28-28.

(87.) Wang Y, Lin Z, Sun L, et al. Akt/Ezrin Tyr353/NF-[kappa]B pathway regulates EGF-induced EMT and metastasis in tongue squamous cell carcinoma. Br J Cancer. 2014; 110(3):695-705. doi:10.1038/bjc.2013.770.

(88.) Ehsanian R, Brown M, Lu H, et al. YAP dysregulation by phosphorylation or [DELTA]Np63-mediated gene repression promotes proliferation, survival and migration in head and neck cancer subsets. Oncogene. 2010; 29(46):61606171. doi:10.1038/onc.2010.339.

(89.) Thomas SM, Coppelli FM, Wells A, et al. Epidermal growth factor receptor-stimulated activation of phospholipase Cy-1 promotes invasion of head and neck squamous cell carcinoma. Cancer Res. 2003; 63(17):5629-5635.

(90.) Johnson FM, Saigal B, Talpaz M, Donato NJ. Dasatinib (BMS-354825) tyrosine kinase inhibitor suppresses invasion and induces cell cycle arrest and apoptosis of head and neck squamous cell carcinoma and non-small cell lung cancer cells. Clin Cancer Res. 2005; 11(19, pt 1):6924-6932. doi:10.1158/ 1078-0432.ccr-05-0757.

(91.) Ammer AG, Kelley LC, Hayes KE, et al. Saracatinib impairs head and neck squamous cell carcinoma invasion by disrupting invadopodia function. J Cancer Sci Ther. 2009; 1(2):52-61. doi:10.4172/1948-5956.1000009.

(92.) Sansing HA, Sarkeshik A, Yates JR, et al. Integrin [alpha][beta]1, [alpha]v[beta], [alpha]6[beta] effectors p130Cas, Src and talin regulate carcinoma invasion and chemoresistance. Biochem Biophys Res Comm. 2011; 406(2):171-176. doi:10.1016/j.bbrc.2011. 01.109.

(93.) Zhang H, Su L, Muller S, et al. Restoration of caveolin-1 expression suppresses growth and metastasis of head and neck squamous cell carcinoma. Br J Cancer. 2008; 99(10):1684-1694. doi:10.1038/sj.bjc.6604735.

(94.) Wheeler SE, Morariu EM, Bednash JS, et al. Lyn kinase mediates cell motility and tumor growth in EGFRvIII-expressing head and neck cancer. Clin Cancer Res. 2012; 18(10):2850-2860. doi:10.1158/1078-0432.ccr-11-2486.

(95.) Patel V, Rosenfeldt HM, Lyons R, et al. Persistent activation of Rac1 in squamous carcinomas of the head and neck: evidence for an EGFR/Vav2 signaling axis involved in cell invasion. Carcinogenesis. 2007; 28(6):1145-1152. doi:10.1093/carcin/bgm008.

(96.) Wheeler SE, Suzuki S, Thomas SM, et al. Epidermal growth factor receptor variant III mediates head and neck cancer cell invasion via STAT3 activation. Oncogene. 2010; 29(37):5135-5145. doi:10.1038/onc.2009.279.

(97.) Zhou X, Ren Y, Liu A, et al. STAT3 inhibitor WP1066 attenuates miRNA-21 to suppress human oral squamous cell carcinoma growth in vitro and in vivo. Oncol Rep. 2014; 31(5):2173-2180. doi:10.3892/or.2014.3114.

(98.) Zhao Y, Zhang J, Xia H, et al. Stat3 is involved in the motility, metastasis and prognosis in lingual squamous cell carcinoma. Cell Biochem Funct. 2012; 30(4):340-346. doi:10.1002/cbf.2810.

(99.) Rosenthal EL, Matrisian LM. Matrix metalloproteases in head and neck cancer. Head Neck. 2006; 28(7):639-648. doi:10.1002/hed.20365.

(100.) Suzuki S, Ishikawa K. Combined inhibition of EMMPRIN and epidermal growth factor receptor prevents the growth and migration of head and neck squamous cell carcinoma cells. Int J Oncol. 2014; 44(3):912-917. doi:10.3892/ ijo.2013.2238.

(101.) Chen HJ, Lin CM, Lee CY, et al. Phenethyl isothiocyanate suppresses EGF-stimulated SAS human oral squamous carcinoma cell invasion by targeting EGF receptor signaling. Int J Oncol. 2013; 43(2):629-637. doi:10.3892/ijo.2013.1977.

(102.) O-charoenrat P, Rhys-Evans P, Modjtahedi H, Court W, Box G, Eccles S. Overexpression of epidermal growth factor receptor in human head and neck squamous carcinoma cell lines correlates with matrix metalloproteinase-9 expression and in vitro invasion. Int J Cancer. 2000; 86(3):307-317.

(103.) Mitra RS, Goto M, Lee JS, et al. Rap1GAP promotes invasion via induction of matrix metalloproteinase 9 secretion, which is associated with poor survival in low N-stage squamous cell carcinoma. Cancer Res. 2008; 68(10): 3959-3969. doi:10.1158/0008-5472.CAN-07-2755.

(104.) Van Tubergen EA, Banerjee R, Liu M, et al. Inactivation or loss of TTP promotes invasion in head and neck cancer via transcript stabilization and secretion of MMP9, MMP2, and IL-6. Clin Cancer Res. 2013; 19(5):1169-1179. doi:10.1158/1078-0432.CCR-12-2927.

(105.) Stetler-Stevenson WG. Type IV collagenases in tumor invasion and metastasis. Cancer Metastasis Rev. 1990; 9(4):289-303.

(106.) Deryugina EI, Quigley JP. Matrix metalloproteinases and tumor metastasis. Cancer Metastasis Rev. 2006; 25(1):9-34. doi:10.1007/ s10555-006-7886-9.

(107.) Egeblad M, Werb Z. New functions for the matrix metalloproteinases in cancer progression. Nat Rev Cancer. 2002; 2(3):161-174. doi:10.1038/nrc745.

(108.) Tamamura R, Nagatsuka H, Siar CH, et al. Comparative analysis of basal lamina type IV collagen [alpha] chains, matrix metalloproteinases-2 and -9 expressions in oral dysplasia and invasive carcinoma. Acta Histochem. 2013; 115(2):113-119. doi:10.1016/j.acthis.2012.05.001.

(109.) Mohtasham N, Babakoohi S, Shiva A, et al. Immunohistochemical study of p53, Ki-67, MMP-2 and MMP-9 expression at invasive front of squamous cell and verrucous carcinoma in oral cavity. Pathol Res Pract. 2013; 209(2):110-114. doi:10.1016/j.prp.2012.11.002.

(110.) Bauvois B. New facets of matrix metalloproteinases MMP-2 and MMP-9 as cell surface transducers: outside-in signaling and relationship to tumor progression. Biochim Biophys Acta. 2012; 1825(1):29-36. doi:10.1016/j.bbcan. 2011.10.001.

(111.) Perez-Sayans Garcia M, Suarez-Penaranda JM, Gayoso-Diz P, Barros-Angueira F, Gandara-Rey JM, Garcia-Garcia A. Tissue inhibitor of metallo-proteinases in oral squamous cell carcinomas--a therapeutic target? Cancer Lett. 2012; 323(1):11-19. doi:10.1016/j.canlet.2012.03.040.

(112.) Singh RD, Haridas N, Patel JB, et al. Matrix metalloproteinases and their inhibitors: correlation with invasion and metastasis in oral cancer. Indian J Clin Biochem. 2010; 25(3):250-259. doi:10.1007/s12291-010-0060-8.

(113.) Munshi HG, Wu YI, Ariztia EV, Stack MS. Calcium regulation of matrix metalloproteinase-mediated migration in oral squamous cell carcinoma cells. J Biol Chem. 2002; 277(44):41480-41488. doi:10.1074/jbc.M207695200.

(114.) Branch KM, Hoshino D, Weaver AM. Adhesion rings surround invadopodia and promote maturation. Biol Open. 2012; 1(8):711-722. doi:10. 1242/bio.20121867.

(115.) Huang Z, Tan N, Guo W, et al. Overexpression of EMMPRIN isoform 2 is associated with head and neck cancer metastasis. PloS One. 2014; 9(4):e91596. doi:10.1371/journal.pone.0091596.

(116.) Sweeny L, Liu Z, Bush BD, Hartman Y, Zhou T, Rosenthal EL. CD147 and AGR2 expression promote cellular proliferation and metastasis of head and neck squamous cell carcinoma. Exp Cell Res. 2012; 318(14):1788-1798. doi:10.1016/ j.yexcr.2012.04.022.

(117.) Lescaille G, Menashi S, Cavelier-Balloy B, et al. EMMPRIN/CD147 up-regulates urokinase-type plasminogen activator: implications in oral tumor progression. BMC Cancer. 2012; 12:115. doi:10.1186/1471-2407-12-115.

(118.) Dang D, Atakilit A, Ramos DM. EMMPRIN modulates migration and deposition of TN-C in oral squamous carcinoma. Anticancer Res. 2008; 28(4B): 2049-2054.

(119.) Cheng MF, Huang MS, Lin CS, et al. Expression of matriptase correlates with tumour progression and clinical prognosis in oral squamous cell carcinoma. Histopathology. 2014; 65(1):24-34. doi:10.1111/his.12361.

(120.) Wang H, Wu Q, Liu Z, et al. Downregulation of FAP suppresses cell proliferation and metastasis through PTEN/PI3K/AKT and Ras-ERK signaling in oral squamous cell carcinoma. Cell Death Dis. 2014; 5:e1155. doi:10.1038/cddis. 2014.122.

(121.) Liang X, Yang X, Tang Y, et al. RNAi-mediated downregulation of urokinase plasminogen activator receptor inhibits proliferation, adhesion, migration and invasion in oral cancer cells. Oral Oncol. 2008; 44(12):1172-1180. doi:10.1016/j.oraloncology.2008.03.004.

(122.) Ghosh S, Johnson JJ, Sen R, et al. Functional relevance of urinary-type plasminogen activator receptor-[alpha]3[beta]1 integrin association in proteinase regulatory pathways. J Biol Chem. 2006; 2 81(19):13021-13029. doi:10.1074/jbc. M508526200.

(123.) Nozaki S, Endo Y, Nakahara H, et al. Inhibition of invasion and metastasis in oral cancer by targeting urokinase-type plasminogen activator receptor. Oral Oncol. 2005; 41(10):971-977. doi:10.1016/j.oraloncology.2005.05.013.

(124.) Albo D, Tuszynski GP. Thrombospondin-1 up-regulates tumor cell invasion through the urokinase plasminogen activator receptor in head and neck cancer cells. J Surg Res. 2004; 120(1):21-26. doi:10.1016/j.jss.2004.03.007.

(125.) Chen J, Zheng D, Shen J, et al. Heparanase is involved in the proliferation and invasion of nasopharyngeal carcinoma cells. Oncol Rep. 2013; 29(5):1888-1894. doi:10.3892/or.2013.2325.

(126.) Sasaya K, Sudo H, Maeda G, Kawashiri S, Imai K. Concomitant loss of p120-catenin and [beta]-catenin membrane expression and oral carcinoma progression with E-cadherin reduction. PloS One. 2013; 8(8):e69777. doi:10.1371/ journal.pone.0069777.

(127.) Munshi HG, Ghosh S, Mukhopadhyay S, et al. Proteinase suppression by E-cadherin-mediated cell-cell attachment in premalignant oral keratinocytes. J Biol Chem. 2002; 277(41):38159-38167. doi:10.1074/jbc.M202384200.

(128.) Nakayama S, Sasaki A, Mese H, Alcalde RE, Tsuji T, Matsumura T. The E-cadherin gene is silenced by CpG methylation in human oral squamous cell carcinomas. Int J Cancer. 2001; 93(5):667-673.

(129.) Doki Y, Shiozaki H, Tahara H, et al. Correlation between E-cadherin expression and invasiveness in vitro in a human esophageal cancer cell line. Cancer Res. 1993; 53(14):3421-3426.

(130.) Wang HC, Chiang WF, Huang HH, Shen YY, Chiang HC. Src-homology 2 domain-containing tyrosine phosphatase 2 promotes oral cancer invasion and metastasis. BMC Cancer. 2014; 14:442. doi:10.1186/1471-2407-14-442.

(131.) Margulis A, Zhang W, Alt-Holland A, Crawford HC, Fusenig NE, Garlick JA. E-cadherin suppression accelerates squamous cell carcinoma progression in three-dimensional, human tissue constructs. Cancer Res. 2005; 65(5):1783-1791. doi:10.1158/0008-5472.CAN-04-3399.

(132.) Sobolik-Delmaire T, Katafiasz D, Keim SA, Mahoney MG, Wahl JK III. Decreased plakophilin-1 expression promotes increased motility in head and neck squamous cell carcinoma cells. Cell Adhes Comm. 2007; 14(2-3):99-109. doi:10.1080/15419060701463082.

(133.) Dos Reis PP, Bharadwaj RR, Machado J, et al. Claudin 1 overexpression increases invasion and is associated with aggressive histological features in oral squamous cell carcinoma. Cancer. 2008; 113(11):3169-3180. doi:10.1002/cncr. 23934.

(134.) Chen YJ, Chang JT, Lee L, et al. DSG3 is overexpressed in head neck cancer and is a potential molecular target for inhibition of oncogenesis. Oncogene. 2007; 26(3):467-476. doi:10.1038/sj.onc.1209802.

(135.) Theocharis S, Klijanienko J, Giaginis C, Alexandrou P, Patsouris E, Sastre-Garau X. FAK and Src expression in mobile tongue squamous cell carcinoma: associations with clinicopathological parameters and patients survival. J Cancer Res Clin Oncol. 2012; 138(8):1369-1377. doi:10.1007/s00432-012-1215-1.

(136.) Zhao D, Tang XF, Yang K, Liu JY, Ma XR. Over-expression of integrinlinked kinase correlates with aberrant expression of Snail, E-cadherin and N-cadherin in oral squamous cell carcinoma: implications in tumor progression and metastasis. Clin Exp Metastasis. 2012; 29(8):957-969. doi:10.1007/ s10585-012-9485-1.

(137.) Kramer RH, Shen X, Zhou H. Tumor cell invasion and survival in head and neck cancer. Cancer Metastasis Rev. 2005; 24(1):35-45. doi:10.1007/ s10555-005-5046-2.

(138.) Thomas GJ, Nystrom ML, Marshall JF. [alpha]v[beta]6 integrin in wound healing and cancer of the oral cavity. J Oral Pathol Med. 2006; 35(1):1-10. doi:10.1111/j. 1600-0714.2005.00374.x.

(139.) Wang D, Muller S, Amin AR, et al. The pivotal role of integrin [beta]1 in metastasis of head and neck squamous cell carcinoma. Clin Cancer Res. 2012; 18(17):4589-4599. doi:10.1158/1078-0432.ccr-11-3127.

(140.) Hunt S, Jones AV, Hinsley EE, Whawell SA, Lambert DW. MicroRNA-124 suppresses oral squamous cell carcinoma motility by targeting ITGB1. FEBS Lett. 2011; 585(1):187-192. doi:10.1016/j.febslet.2010.11.038.

(141.) Xue H, Atakilit A, Zhu W, Li X, Ramos DM, Pytela R. Role of the avp6 integrin in human oral squamous cell carcinoma growth in vivo and in vitro. Biochem Biophys Res Comm. 2001; 288(3):610-618. doi:10.1006/bbrc.2001. 5813.

(142.) Morgan MR, Jazayeri M, Ramsay AG, et al. Psoriasin (S100A7) associates with integrin [beta]6 subunit and is required for [alpha]v[beta]6-dependent carcinoma cell invasion. Oncogene. 2011; 30(12):1422-1435. doi:10.1038/onc.2010.535.

(143.) Ramos DM, But M, Regezi J, et al. Expression of integrin [beta]6 enhances invasive behavior in oral squamous cell carcinoma. Matrix Biol. 2002; 21(3):297-307.

(144.) Scott KA, Arnott CH, Robinson SC, et al. TNF-[alpha] regulates epithelial expression of MMP-9 and integrin [alpha]v[beta]6 during tumour promotion: a role for TNF-[alpha] in keratinocyte migration? Oncogene. 2004; 23(41):6954-6966. doi:10.1038/sj. onc.1207915.

(145.) Koontongkaew S, Amornphimoltham P, Monthanpisut P, Saensuk T, Leelakriangsak M. Fibroblasts and extracellular matrix differently modulate MMP activation by primary and metastatic head and neck cancer cells. Med Oncol. 2012; 29(2):690-703. doi:10.1007/s12032-011-9871-6.

(146.) Ratzinger S, Grassel S, Dowejko A, Reichert TE, Bauer RJ. Induction of type XVI collagen expression facilitates proliferation of oral cancer cells. Matrix Biol. 2011; 30(2):118-125. doi:10.1016/j.matbio.2011.01.001.

(147.) Grassel S, Bauer RJ. Collagen XVI in health and disease. Matrix Biol. 2013; 32(2):64-73. doi:10.1016/j.matbio.2012.11.001.

(148.) Kinoshita T, Nohata N, Hanazawa T, et al. Tumour-suppressive microRNA-29s inhibit cancer cell migration and invasion by targeting laminin-integrin signalling in head and neck squamous cell carcinoma. Br J Cancer. 2013; 109(10): 2636-2645. doi:10.1038/bjc.2013.607.

(149.) Xing Y, Qi J, Deng S, Wang C, Zhang L, Chen J. Small interfering RNA targeting ILK inhibits metastasis in human tongue cancer cells through repression of epithelial-to-mesenchymal transition. Exp Cell Res. 2013; 319(13):2058-2072. doi:10.1016/j.yexcr.2013.05.014.

(150.) Lai MT, Hua CH, Tsai MH, et al. Talin-1 overexpression defines high risk for aggressive oral squamous cell carcinoma and promotes cancer metastasis. J Pathol. 2011; 224(3):367-376. doi:10.1002/path.2867.

(151.) Canel M, Secades P, Garzon-Arango M, et al. Involvement of focal adhesion kinase in cellular invasion of head and neck squamous cell carcinomas via regulation of MMP-2 expression. Br J Cancer. 2008; 98(7):1274-1284. doi:10. 1038/sj.bjc.6604286.

(152.) Xiao W, Jiang M, Li H, Li C, Su R, Huang K. Knockdown of FAK inhibits the invasion and metastasis of Tca8113 cells in vitro. Mol Med Rep. 2013; 8(2): 703-707. doi:10.3892/mmr.2013.1555.

(153.) Kurio N, Shimo T, Fukazawa T, et al. Anti-tumor effect of a novel FAK inhibitor TAE226 against human oral squamous cell carcinoma. Oral Oncol. 2012; 48(11):1159-11 70. doi:10.1016/j.oraloncology.2012.05.019.

(154.) Li X, Yang Y, Hu Y, et al. [[alpha].sub.v][[beta].sub.6]-Fyn signaling promotes oral cancer progression. J Biol Chem. 2003; 278(43):41646-41653. doi:10.1074/jbc. M306274200.

(155.) Hoshino D, Branch KM, Weaver AM. Signaling inputs to invadopodia and podosomes. J Cell Sci. 2013; 126(pt 14):2979-2989. doi:10.1242/jcs.079475.

(156.) Beaty BT, Condeelis J. Digging a little deeper: the stages of invadopodium formation and maturation [published online ahead of print July 21, 2014]. Eur J Cell Biol. 2014; 93(10-12):438-444. doi:10.1016/j.ejcb.2014.07.003.

(157.) Gould CM, Courtneidge SA. Regulation of invadopodia by the tumor microenvironment. Cell Adh Migr. 2014; 8(3):226-235.

(158.) Revach OY, Geiger B. The interplay between the proteolytic, invasive, and adhesive domains of invadopodia and their roles in cancer invasion. Cell Adh Migr. 2013; 8(3):215-225.

(159.) Boateng LR, Huttenlocher A. Spatiotemporal regulation of Src and its substrates at invadosomes. Eur J Cell Biol. 2012; 91(11-12):878-888. doi:10.1016/ j.ejcb.2012.06.003.

(160.) Farazi TA, Hoell JI, Morozov P, Tuschl T. MicroRNAs in human cancer. Adv Exp Med Biol. 2013; 774:1-20. doi:10.1007/978-94-007-5590-1_1.

(161.) Lee YS, Dutta A. MicroRNAs in cancer. Annu Rev Pathol. 2009; 4:199-227. doi:10.1146/annurev.pathol.4.110807.092222.

(162.) Nohata N, Hanazawa T, Kinoshita T, Okamoto Y, Seki N. MicroRNAs function as tumor suppressors or oncogenes: aberrant expression of microRNAs in head and neck squamous cell carcinoma. Auris Nasus Larynx. 2013; 40(2):143-149. doi:10.1016/j.anl.2012.07.001.

(163.) Janiszewska J, Szaumkessel M, Szyfter K. MicroRNAs are important players in head and neck carcinoma: a review. Crit Rev Oncol Hematol. 2013; 88(3):716-728. doi:10.1016/j.critrevonc.2013.07.012.

(164.) Chen D, Cabay RJ, Jin Y, et al. MicroRNA deregulations in head and neck squamous cell carcinomas. J Oral Maxillofac Res. 2013; 4(1):e2. doi:10.5037/ jomr.2013.4102.

(165.) John K, WuJ, Lee BW, Farah CS. MicroRNAs in head and neck cancer. Int J Dent. 2013; 2013:650218. doi:10.1155/2013/650218.

(166.) Cheng Q, Yi B, Wang A, Jiang X. Exploring and exploiting the fundamental role of microRNAs in tumor pathogenesis. Onco Targets Ther. 2013; 6:1675-1684. doi:10.2147/OTT.S52730.

(167.) Babu JM, Prathibha R, Jijith VS, Hariharan R, Pillai MR. A miR-centric view of head and neck cancers. Biochim Biophys Acta. 2011; 1816(1):67-72. doi: 10.1016/j.bbcan.2011.04.003.

(168.) Zeng S, Yang J, Zhao J, et al. Silencing Dicer expression enhances cellular proliferative and invasive capacities in human tongue squamous cell carcinoma. Oncol Rep. 2014; 31(2):867-873. doi:10.3892/or.2013.2903.

(169.) Yang X, Wu H, Ling T. Suppressive effect of microRNA-126 on oral squamous cell carcinoma in vitro. Mol Med Rep. 2014; 10(1):125-130. doi:10. 3892/mmr.2014.2171.

(170.) Kawakita A, Yanamoto S, Yamada SI, et al. MicroRNA-21 promotes oral cancer invasion via the Wnt/[beta]-catenin pathway by targeting DKK2 [published online ahead of print September 3, 2013]. Pathol Oncol Res. 2014; 20(2):253-261. doi:10.1007/s12253-013-9689-y.

(171.) Yen YC, Shiah SG, Chu HC, et al. Reciprocal regulation of microRNA-99a and insulin-like growth factor I receptor signaling in oral squamous cell carcinoma cells. Mol Cancer. 2014; 13:6. doi:10.1186/1476-4598-13-6.

(172.) Lenarduzzi M, Hui AB, Alajez NM, et al. MicroRNA-193b enhances tumor progression via down regulation of neurofibromin 1. PloS one. 2013; 8(1): e53765. doi:10.1371/journal.pone.0053765.

(173.) Zhao XD, Zhang W, Liang HJ, Ji WY. Overexpression of miR -155 promotes proliferation and invasion of human laryngeal squamous cell carcinoma via targeting SOCS1 and STAT3. PloS one. 2013; 8(2):e56395. doi: 10.1371/journal.pone.0056395.

(174.) Datta J, Smith A, Lang JC, et al. microRNA-107 functions as a candidate tumor-suppressor gene in head and neck squamous cell carcinoma by downregulation of protein kinase Cvarepsilon. Oncogene. 2012; 31(36):4045-4053. doi:10.1038/onc.2011.565.

(175.) Kinoshita T, Hanazawa T, Nohata N, et al. Tumor suppressive microRNA-218 inhibits cancer cell migration and invasion through targeting laminin332 in head and neck squamous cell carcinoma. Oncotarget. 2012; 3(11):1386-1400.

(176.) Lu L, Xue X, Lan J, et al. MicroRNA-29a upregulates MMP2 in oral squamous cell carcinoma to promote cancer invasion and anti-apoptosis. Biomed Pharmacother. 2014; 68(1):13-19. doi:10.1016/j.biopha.2013.10.005.

(177.) Kai Y, Peng W, Ling W, Jiebing H, Zhuan B. Reciprocal effects between microRNA-140-5p and ADAM10 suppress migration and invasion of human tongue cancer cells. Biochem Biophys Res Comm. 2014; 448(3):308-314. doi:10. 1016/j.bbrc.2014.02.032.

(178.) Nohata N, Sone Y, Hanazawa T, et al. miR-1 as a tumor suppressive microRNA targeting TAGLN2 in head and neck squamous cell carcinoma. Oncotarget. 2011; 2(1-2):29-42.

(179.) Kinoshita T, Nohata N, Fuse M, et al. Tumor suppressive microRNA-133a regulates novel targets: moesin contributes to cancer cell proliferation and invasion in head and neck squamous cell carcinoma. Biochem Biophys Res Comm. 2012; 418(2):378-383. doi:10.1016/j.bbrc.2012.01.030.

(180.) Kinoshita T, Nohata N, Watanabe-Takano H, et al. Actin-related protein 2/3 complex subunit 5 (ARPC5) contributes to cell migration and invasion and is directly regulated by tumor-suppressive microRNA-133a in head and neck squamous cell carcinoma. Int J Oncol. 2012; 40(6):1770-1778. doi:10.3892/ijo. 2012.1390.

(181.) Sun Q, Zhang J, Cao W, et al. Dysregulated miR-363 affects head and neck cancer invasion and metastasis by targeting podoplanin. Int J Biochem Cell Biol. 2013; 45(3):513-520. doi:10.1016/j.biocel.2012.12.004.

(182.) Kamochi N, Nakashima M, Aoki S, et al. Irradiated fibroblast-induced bystander effects on invasive growth of squamous cell carcinoma under cancer-stromal cell interaction. Cancer Sci. 2008; 99(12):2417-2427. doi:10.1111/j. 1349-7006.2008.00978.x.

(183.) Li X, Xu Q, Wu Y, et al. A CCL2/ROS autoregulation loop is critical for cancer-associated fibroblasts-enhanced tumor growth of oral squamous cell carcinoma. Carcinogenesis. 2014; 35(6):1362-1370. doi:10.1093/carcin/bgu046.

(184.) Islam M, Datta J, Lang JC, Teknos TN. Down regulation of RhoC by microRNA-138 results in de-activation of FAK, Src and Erk1/2 signaling pathway in head and neck squamous cell carcinoma. Oral Oncol. 2014; 50(5):448-456. doi:10.1016/j.oraloncology.2014.01.014.

(185.) Liu X, Wang C, Chen Z, et al. MicroRNA-138 suppresses epithelial-mesenchymal transition in squamous cell carcinoma cell lines. Biochem J. 2011; 440(1):23-31. doi:10.1042/BJ20111006.

(186.) Lin Z, Sun L, Chen W, et al. miR-639 regulates transforming growth factor beta-induced epithelial-mesenchymal transition in human tongue cancer cells by targeting FOXC1. Cancer Sci. 2014; 105(10):1288-1298. doi:10.1111/cas.12499.

(187.) Liu M, Wang J, Huang H, Hou J, Zhang B, Wang A. miR-181a-Twist1 pathway in the chemoresistance of tongue squamous cell carcinoma. Biochem Biophys Res Comm. 2013; 441(2):364-370. doi:10.1016/j.bbrc.2013.10.051.

(188.) Jia LF, Huang YP, Zheng YF, et al. miR-29b suppresses proliferation, migration, and invasion of tongue squamous cell carcinoma through PTEN-AKT signaling pathway by targeting Sp1 [published online ahead of print August 7, 2014]. Oral Oncol. 2014; 50(11):1062-1071. doi:10.1016/j.oraloncology.2014. 07.010.

(189.) Hui AB, Bruce JP, Alajez NM, et al. Significance of dysregulated metadherin and microRNA-375 in head and neck cancer. Clin Cancer Res. 2011; 17(24):7539-7550. doi:10.1158/1078-0432.CCR-11-2102.

(190.) Hui AB, Lenarduzzi M, Krushel T, et al. Comprehensive MicroRNA profiling for head and neck squamous cell carcinomas. Clin Cancer Res. 2010; 16(4):1129-1139. doi:10.1158/1078-0432.CCR-09-2166.

(191.) Nohata N, Hanazawa T, Kikkawa N, et al. Tumor suppressive microRNA-375 regulates oncogene AEG-1/MTDH in head and neck squamous cell carcinoma (HNSCC). J Hum Genet. 2011; 56(8):595-601. doi:10.1038/jhg. 2011.66.

(192.) Harris T, Jimenez L, Kawachi N, et al. Low-level expression of miR-375 correlates with poor outcome and metastasis while altering the invasive properties of head and neck squamous cell carcinomas. Am J Pathol. 2012; 180(3):917-928. doi:10.1016/j.ajpath.2011.12.004.

(193.) Chen Z, Jin Y, Yu D, et al. Down-regulation of the microRNA-99 family members in head and neck squamous cell carcinoma. Oral Oncol. 2012; 48(8): 686-691. doi:10.1016/j.oraloncology.2012.02.020.

(194.) Yang MH, Lin BR, Chang CH, et al. Connective tissue growth factor modulates oral squamous cell carcinoma invasion by activating a miR-504/FOXP1 signalling. Oncogene. 2012; 31(19):2401-2411. doi:10.1038/onc.2011.423.

(195.) Reis PP, Tomenson M, Cervigne NK, et al. Programmed cell death 4 loss increases tumor cell invasion and is regulated by miR-21 in oral squamous cell carcinoma. Mol Cancer. 2010; 9:238. doi:10.1186/1476-4598-9-238.

(196.) Jiang F, Zhao W, Zhou L, Zhang L, Liu Z, Yu D. miR-222 regulates the cell biological behavior of oral squamous cell carcinoma by targeting PUMA. Oncol Rep. 2014; 31(3):1255-1262. doi:10.3892/or.2014.2985.

(197.) Liu X, Yu J, Jiang L, et al. MicroRNA-222 regulates cell invasion by targeting matrix metalloproteinase 1 (MMP1) and manganese superoxide dismutase 2 (SOD2) in tongue squamous cell carcinoma cell lines. Cancer Genomics Proteomics. 2009; 6(3):131-139.

(198.) Parekh A, Weaver AM. Regulation of cancer invasiveness by the physical extracellular matrix environment. Cell Adh Migr. 2009; 3(3):288-292.

(199.) Bravo-Cordero JJ, Hodgson L, Condeelis J. Directed cell invasion and migration during metastasis. Curr Opin Cell Biol. 2012; 24(2):277-283. doi:10. 1016/j.ceb.2011.12.004.

(200.) Weaver AM. Invadopodia: specialized cell structures for cancer invasion. Clin Exp Metastasis. 2006; 23(2):97-105. doi:10.1007/s10585-006-9014-1.

(201.) Artym VV, Yamada KM, Mueller SC. ECM degradation assays for analyzing local cell invasion. Methods Mol Biol. 2009; 522:211-219. doi:10. 1007/978-1-59745-413-1_15.

(202.) Rothschild BL, Shim AH, Ammer AG, et al. Cortactin overexpression regulates actin-related protein 2/3 complex activity, motility, and invasion in carcinomas with chromosome 11q13 amplification. Cancer Res. 2006; 66(16): 8017-8025. doi:10.1158/0008-5472.CAN-05-4490.

(203.) Timpson P, Lynch DK, Schramek D, Walker F, Daly RJ. Cortactin overexpression inhibits ligand-induced down-regulation of the epidermal growth factor receptor. Cancer Res. 2005; 65(8):3273-3280. doi:10.1158/0008-5472. CAN-04-2118.

(204.) Clark ES, Whigham AS, Yarbrough WG, Weaver AM. Cortactin is an essential regulator of matrix metalloproteinase secretion and extracellular matrix degradation in invadopodia. Cancer Res. 2007; 67(9):4227-4235. doi:10.1158/ 0008-5472.CAN-06-3928.

(205.) Kelley LC, Ammer AG, Hayes KE, et al. Oncogenic Src requires a wild-type counterpart to regulate invadopodia maturation. J Cell Sci. 2010; 123(pt 22): 3923-3932. doi:10.1242/jcs.075200.

(206.) Mader CC, Oser M, Magalhaes MA, et al. An EGFR-Src-Arg-cortactin pathway mediates functional maturation of invadopodia and breast cancer cell invasion. Cancer Res. 2011; 71(5):1730-1741. doi:10.1158/0008-5472. CAN-10-1432.

(207.) Hwang YS, Park KK, Chung WY. Invadopodia formation in oral squamous cell carcinoma: the role of epidermal growth factor receptor signalling. Arch Oral Biol. 2012; 57(4):335-343. doi:10.1016/j.archoralbio.2011.08.019.

(208.) Hwang YS, Park KK, Cha IH, Kim J, Chung WY. Role of insulin-like growth factor-II mRNA-binding protein-3 in invadopodia formation and the growth of oral squamous cell carcinoma in athymic nude mice. Head Neck. 2012; 34(9): 1329-1339. doi:10.1002/hed.21929.

(209.) Hoshino D, Jourquin J, Emmons SW, et al. Network analysis of the focal adhesion to invadopodia transition identifies a PI3K-PKC[alpha] invasive signaling axis. Sci Signal. 2012; 5(241):ra66. doi:10.1126/scisignal.2002964.

(210.) Yamaguchi H, Yoshida S, Muroi E, et al. Phosphoinositide 3-kinase signaling pathway mediated by p110a regulates invadopodia formation. J Cell Biol. 2011; 193(7):1275-1288. doi:10.1083/jcb.201009126.

(211.) Gardberg M, Kaipio K, Lehtinen L, et al. FHOD1, aformin upregulated in epithelial-mesenchymal transition, participates in cancer cell migration and invasion. PloS One. 2013; 8(9):e74923. doi:10.1371/journal.pone.0074923.

(212.) Hoshino D, Kirkbride KC, Costello K, et al. Exosome secretion is enhanced by invadopodia and drives invasive behavior. Cell Rep. 2013; 5(5): 1159-1168. doi:10.1016/j.celrep.2013.10.050.

(213.) Scanlon CS, Van Tubergen EA, Inglehart RC, D'Silva NJ. Biomarkers of epithelial-mesenchymal transition in squamous cell carcinoma. J Dent Res. 2013; 92(2):114-121. doi:10.1177/0022034512467352.

(214.) Smith A, Teknos TN, Pan Q. Epithelial to mesenchymal transition in head and neck squamous cell carcinoma. Oral Oncol. 2013; 49(4):287-292. doi:10. 1016/j.oraloncology.2012.10.009.

(215.) Barrette K, Van Kelst S, Wouters J, et al. Epithelial-mesenchymal transition during invasion of cutaneous squamous cell carcinoma is paralleled by AKT activation. Br J Dermatol. 2014; 171(5):1014-1021. doi:10.1111/bjd.12967.

(216.) Mani SA, Guo W, Liao MJ, et al. The epithelial-mesenchymal transition generates cells with properties of stem cells. Cell. 2008; 133(4):704-715. doi:10. 1016/j.cell.2008.03.027.

(217.) Zhang Z, Filho MS, Nor JE. The biology of head and neck cancer stem cells. Oral Oncol. 2012; 48(1):1-9. doi:10.1016/j.oraloncology.2011.10.004.

(218.) Chang JY, Wright JM, Svoboda KK. Signal transduction pathways involved in epithelial-mesenchymal transition in oral cancer compared with other cancers. Cells Tissues Organs 2007; 185(1-3):40-47. doi:10.1159/000101301.

(219.) Yang MH, Hsu DS, Wang HW, et al. Bmi1 is essential in Twist1-induced epithelial-mesenchymal transition. Nat Cell Biol. 2010; 12(10):982-992. doi:10. 1038/ncb2099.

(220.) Yang N, Hui L, Wang Y, Yang H, Jiang X. SOX2 promotes the migration and invasion of laryngeal cancer cells by induction of MMP-2 via the PI3K/Akt/ mTOR pathway. Oncol Rep. 2014; 31(6):2651-2659. doi:10.3892/or.2014. 3120.

(221.) Yang CC, Zhu LF, Xu XH, Ning TY, Ye JH, Liu LK. Membrane type 1 matrix metalloproteinase induces an epithelial to mesenchymal transition and cancer stem cell-like properties in SCC9 cells. BMC Cancer. 2013; 13:171. doi:10.1186/ 1471-2407-13-171.

(222.) Higashikawa K, Yoneda S, Tobiume K, Taki M, Shigeishi H, Kamata N. Snail-induced down-regulation of DeltaNp63[alpha] acquires invasive phenotype of human squamous cell carcinoma. Cancer Res. 2007; 67(19):9207-9213. doi:10. 1158/0008-5472.CAN-07-0932.

(223.) Zhang Z, Dong Z, Lauxen IS, Filho MS, Nor JE. Endothelial cell-secreted EGF induces epithelial to mesenchymal transition and endows head and neck cancer cells with stem-like phenotype. Cancer Res. 2014; 74(10):2869-2881. doi: 10.1158/0008-5472.CAN-13-2032.

(224.) Zhu LF, Hu Y, Yang CC, et al. Snail overexpression induces an epithelial to mesenchymal transition and cancer stem cell-like properties in SCC9 cells. Lab Invest. 2012; 92(5):744-752. doi:10.1038/labinvest.2012.8.

(225.) Krishnamurthy S, Nor JE. Head and neck cancer stem cells. J Dent Res. 2012; 91(4):334-340. doi:10.1177/0022034511423393.

(226.) Krishnamurthy S, Dong Z, Vodopyanov D, et al. Endothelial cell-initiated signaling promotes the survival and self-renewal of cancer stem cells. Cancer Res. 2010; 70(23):9969-9978. doi:10.1158/0008-5472.CAN-10-1712.

(227.) Ritchie KE, Nor JE. Perivascular stem cell niche in head and neck cancer. Cancer letters. 2013; 338(1):41-46. doi:10.1016/j.canlet.2012.07.025.

(228.) Wu KJ, Yang MH. Epithelial-mesenchymal transition and cancer sternness: the Twist1-Bmi1 connection. Bioscience reports. 2011; 31(6):449-455. doi: 10.1042/BSR20100114.

(229.) Lamouille S, Connolly E, Smyth JW, Akhurst RJ, Derynck R. TGF-[beta]-induced activation of mTOR complex 2 drives epithelial-mesenchymal transition and cell invasion. J Cell Sci. 2012; 125(pt 5):1259-1273. doi:10.1242/jcs.095299.

(230.) Judd NP, Winkler AE, Murillo-Sauca O, et al. ERK1/2 regulation of CD44 modulates oral cancer aggressiveness. Cancer Res. 2012; 72(1):365-374. doi:10. 1158/0008-5472.CAN-11-1831.

(231.) Biddle A, Liang X, Gammon L, et al. Cancer stem cells in squamous cell carcinoma switch between two distinct phenotypes that are preferentially migratory or proliferative. Cancer Res. 2011; 71(15):5317-5326. doi:10.1158/ 0008-5472.CAN-11-1059.

(232.) Kudo T, Shimazu Y, Yagishita H, et al. Three-dimensional reconstruction of oral tongue squamous cell carcinoma at invasion front. Int J Dent. 2013; 2013: 482765. doi:10.1155/2013/482765.

(233.) Friedl P, Locker J, Sahai E, Segall JE. Classifying collective cancer cell invasion. Nat Cell Biol. 2012; 14(8):777-783. doi:10.1038/ncb2548.

(234.) Salo T, Vered M, Bello IO, et al. Insights into the role of components of the tumor microenvironment in oral carcinoma call for new therapeutic approaches. Exp Cell Res. 2014; 325(2):58-64. doi:10.1016/j.yexcr.2013.12.029.

(235.) Curry JM, Sprandio J, Cognetti D, et al. Tumor microenvironment in head and neck squamous cell carcinoma. Semin Oncol. 2014; 41(2):217-234. doi:10. 1053/j.seminoncol.2014.03.003.

(236.) Koontongkaew S. The tumor microenvironment contribution to development, growth, invasion and metastasis of head and neck squamous cell carcinomas. J Cancer. 2013; 4(1):66-83. doi:10.7150/jca.5112.

(237.) Rivera C, Venegas B. Histological and molecular aspects of oral squamous cell carcinoma (review). Oncol Lett. 2014; 8(1):7-11. doi:10.3892/ol. 2014.2103.

(238.) Wheeler SE, Shi H, Lin F, et al. Enhancement of head and neck squamous cell carcinoma proliferation, invasion, and metastasis by tumor-associated fibroblasts in preclinical models. Head Neck. 2014; 36(3):385-392. doi:10. 1002/hed.23312.

(239.) Matsumoto K, Horikoshi M, Rikimaru K, Enomoto S. A study of an in vitro model for invasion of oral squamous cell carcinoma. J Oral Pathol Med. 1989; 18(9):498-501.

(240.) Berndt A, Hyckel P, Konneker A, Katenkamp D, Kosmehl H. Oral squamous cell carcinoma invasion is associated with a laminin-5 matrix reorganization but independent of basement membrane and hemidesmosome formation. clues from an in vitro invasion model. Invasion Metastasis. 1997; 17(5):

251-258.

(241.) Satoh S, Toda S, Inokuchi A, Sugihara H. A new in vitro model for analyzing the biological behavior of well-differentiated squamous cell carcinoma. Pathol Res Pract. 2005; 201(1):27-35. doi:10.1016/j.prp.2004.09.015.

(242.) Nystrom ML, Thomas GJ, Stone M, Mackenzie IC, Hart IR, Marshall JF. Development of a quantitative method to analyse tumour cell invasion in organotypic culture. J Pathol. 2005; 205(4):468-475. doi:10.1002/path.1716.

(243.) Sobral LM, Bufalino A, Lopes MA, Graner E, Salo T, Coletta RD. Myofibroblasts in the stroma of oral cancer promote tumorigenesis via secretion of activin A. Oral Oncol. 2011; 47(9):840-846. doi:10.1016/j.oraloncology.2011. 06.011.

(244.) Berndt A, Buttner R, Guhne S, et al. Effects of activated fibroblasts on phenotype modulation, EGFR signalling and cell cycle regulation in OSCC cells. Exp Cell Res. 2014; 322(2):402-414. doi:10.1016/j.yexcr.2013.12.024.

(245.) Zhou B, Chen WL, Wang YY, et al. A role for cancer-associated fibroblasts in inducing the epithelial-to-mesenchymal transition in human tongue squamous cell carcinoma. J Oral Pathol Med. 2014; 43(8):585-592. doi:10.1111/jop.12172.

(246.) Hinsley EE, Kumar S, Hunter KD, Whawell SA, Lambert DW. Endothelin1 stimulates oral fibroblasts to promote oral cancer invasion. Life Sci. 2012; 91(13-14):557-561. doi:10.1016/j.lfs.2012.04.001.

(247.) Lengyel E, Gum R, Juarez J, et al. Induction of Mr 92,000 type IV collagenase expression in a squamous cell carcinoma cell line by fibroblasts. Cancer Res. 1995; 55(4):963-967.

(248.) Hassona Y, Cirillo N, Lim KP, et al. Progression of genotype-specific oral cancer leads to senescence of cancer-associated fibroblasts and is mediated by oxidative stress and TGF-[beta]. Carcinogenesis. 2013; 34(6):1286-1295. doi:10.1093/ carcin/bgt035.

(249.) Hassona Y, Cirillo N, Heesom K, Parkinson EK, Prime SS. Senescent cancer-associated fibroblasts secrete active MMP-2 that promotes keratinocyte dis-cohesion and invasion. Br J Cancer. 2014; 111(6):1230-1237. doi:10.1038/ bjc.2014.438.

(250.) Pal A, Melling G, Hinsley EE, et al. Cigarette smoke condensate promotes pro-tumourigenic stromal-epithelial interactions by suppressing miR-145. J Oral Pathol Med. 2013; 42(4):309-314. doi:10.1111/jop.12017.

(251.) Lu HH, Liu CJ, Liu TY, Kao SY, Lin SC, Chang KW. Areca-treated fibroblasts enhance tumorigenesis of oral epithelial cells. J Dent Res. 2008; 87(11):1069-1074.

(252.) Wu MH, Hong HC, Hong TM, Chiang WF, Jin YT, Chen YL. Targeting galectin-1 in carcinoma-associated fibroblasts inhibits oral squamous cell carcinoma metastasis by downregulating MCP-1/CCL2 expression. Clin Cancer Res. 2011; 17(6):1306-1316. doi:10.1158/1078-0432.CCR-10-1824.

(253.) Jung DW, Che ZM, Kim J, et al. Tumor-stromal crosstalk in invasion of oral squamous cell carcinoma: a pivotal roleofCCL7. Int J Cancer. 2010; 127(2):332-344. doi:10.1002/ijc.25060.

(254.) Daly AJ, McIlreavey L, Irwin CR. Regulation of HGF and SDF-1 expression by oral fibroblasts--implications for invasion of oral cancer. Oral Oncol. 2008; 44(7):646-651. doi:10.1016/j.oraloncology.2007.08.012.

(255.) Costea DE, Hills A, Osman AH, et al. Identification of two distinct carcinoma-associated fibroblast subtypes with differential tumor-promoting abilities in oral squamous cell carcinoma. Cancer Res. 2013; 73(13):3888-3901. doi:10.1158/0008-5472.CAN-12-4150.

(256.) Hwang YS, Park KK, Chung WY. Stromal transforming growth factor-[beta] 1 is crucial for reinforcing the invasive potential of low invasive cancer. Arch Oral Biol. 2014; 59(7):687-694. doi:10.1016/j.archoralbio.2014.03.017.

(257.) Chen SF, Nieh S, Jao SW, et al. The paracrine effect of cancer-associated fibroblast-induced interleukin-33 regulates the invasiveness of head and neck squamous cell carcinoma. J Pathol. 2013; 231(2):180-189. doi:10.1002/path. 4226.

(258.) Kurihara Y, Hatori M, Ando Y, et al. Inhibition of cyclooxygenase-2 suppresses the invasiveness of oral squamous cell carcinoma cell lines via downregulation of matrix metalloproteinase-2 production and activation. Clin Exp Metastasis. 2009; 26(5):425-432. doi:10.1007/s10585-009-9241-3.

(259.) Sobral LM, Zecchin KG, Nascimento de Aquino S, Lopes MA, Graner E, Coletta RD. Isolation and characterization of myofibroblast cell lines from oral squamous cell carcinoma. Oncol Rep. 2011; 25(4):1013-1020. doi:10.3892/or. 2011.1161.

(260.) Hinsley EE, Hunt S, Hunter KD, Whawell SA, Lambert DW. Endothelin-1 stimulates motility of head and neck squamous carcinoma cells by promoting stromal-epithelial interactions. Int J Cancer. 2012; 130(1):40-47. doi:10.1002/ijc. 25968.

(261.) Matsumoto K, Matsumoto K, Nakamura T, Kramer RH. Hepatocyte growth factor/scatter factor induces tyrosine phosphorylation of focal adhesion kinase (p125FAK) and promotes migration and invasion by oral squamous cell carcinoma cells. J Biol Chem. 1994; 269(50):31807-31813.

(262.) Knowles LM, Stabile LP, Egloff AM, et al. HGF and c-Met participate in paracrine tumorigenic pathways in head and neck squamous cell cancer. Clin Cancer Res. 2009; 15(11):3740-3750. doi:10.1158/1078-0432.CCR-08-3252.

(263.) Uchida D, Kawamata H, Omotehara F, et al. Role of HGF/c-met system in invasion and metastasis of oral squamous cell carcinoma cells in vitro and its clinical significance. Int J Cancer. 2001; 93(4):489-496.

(264.) Lewis MP, Lygoe KA, Nystrom ML, et al. Tumour-derived TGF-[beta]1 modulates myofibroblast differentiation and promotes HGF/SF-dependent invasion of squamous carcinoma cells. Br J Cancer. 2004; 90(4):822-832. doi:10. 1038/sj.bjc.6601611.

(265.) Hasina R, Matsumoto K, Matsumoto-Taniura N, Kato I, Sakuda M, Nakamura T. Autocrine and paracrine motility factors and their involvement in invasiveness in a human oral carcinoma cell line. Br J Cancer. 1999; 80(11):1708-1717. doi:10.1038/sj.bjc.6690587.

(266.) Hayashido Y, Nakashima M, Urabe K, et al. Role of stromal thrombospondin-1 in motility and proteolytic activity of oral squamous cell carcinoma cells. Int J Mol Med. 2003; 12(4):447-452.

(267.) Liu H, Chen B, Zardi L, Ramos DM. Soluble fibronectin promotes migration of oral squamous-cell carcinoma cells. Int J Cancer. 1998; 78(2):261-267.

(268.) Fu L, Zhang C, Zhang LY, et al. Wnt2 secreted by tumour fibroblasts promotes tumour progression in oesophageal cancer by activation of the Wnt/[beta]-catenin signalling pathway. Gut. 2011; 60(12):1635-1643. doi:10.1136/gut.2011. 241638.

(269.) Kumar P, Ning Y, Polverini PJ. Endothelial cells expressing Bcl-2 promotes tumor metastasis by enhancing tumor angiogenesis, blood vessel leakiness and tumor invasion. Lab Invest. 2008; 88(7):740-749. doi:10.1038/labinvest.2008.46.

(270.) Warner KA, Miyazawa M, Cordeiro MM, et al. Endothelial cells enhance tumor cell invasion through a crosstalk mediated by CXC chemokine signaling. Neoplasia. 2008; 10(2):131-139.

(271.) Kumar P, Miller AI, Polverini PJ. p38 MAPK mediates [gamma]-irradiation-induced endothelial cell apoptosis, and vascular endothelial growth factor protects endothelial cells through the phosphoinositide 3-kinase-Akt-Bcl-2 pathway. J Biol Chem. 2004; 279(41):43352-43360. doi:10.1074/jbc. M405777200.

(272.) Lee CH, Liu SY, Chou KC, et al. Tumor-associated macrophages promote oral cancer progression through activation of the Axl signaling pathway. Ann Surg Oncol. 2014; 21(3):1031-1037. doi:10.1245/s10434-013-3400-0.

(273.) Cavel O, Shomron O, Shabtay A, et al. Endoneurial macrophages induce perineural invasion of pancreatic cancer cells by secretion of GDNF and activation of RET tyrosine kinase receptor. Cancer Res. 2012; 72(22):5733-5743. doi:10.1158/0008-5472.CAN-12-0764.

(274.) Zhang J, Cheng Q, Zhou Y, Wang Y, Chen X. Slug is a key mediator of hypoxia induced cadherin switch in HNSCC: correlations with poor prognosis. Oral Oncol. 2013; 49(11):1043-1050. doi:10.1016/j.oraloncology.2013.08.003.

(275.) LvC, Yang X, Yu B, Ma Q, Liu B, Liu Y. Blocking the Na+/H+ exchanger 1 with cariporide (HOE642) reduces the hypoxia-induced invasion of human tongue squamous cell carcinoma. Int J Oral Maxillofac Surg. 2012; 41(10):1206-1210. doi:10.1016/j.ijom.2012.03.001.

(276.) Wang X, Schneider A. HIF-2a-mediated activation of the epidermal growth factor receptor potentiates head and neck cancer cell migration in response to hypoxia. Carcinogenesis. 2010; 31(7):1202-1210. doi:10.1093/ carcin/bgq078.

(277.) Ryu MH, Park HM, Chung J, Lee CH, Park HR. Hypoxia-inducible factor-1[alpha] mediates oral squamous cell carcinoma invasion via upregulation of [alpha]5 integrin and fibronectin. Biochem Biophys Res Comm. 2010; 393(1):11-15. doi: 10.1016/j.bbrc.2010.01.060.

(278.) Mohyeldin A, Lu H, Dalgard C, et al. Erythropoietin signaling promotes invasiveness of human head and neck squamous cell carcinoma. Neoplasia. 2005; 7(5):537-543.

(279.) Shlien A, Malkin D. Copy number variations and cancer. Genome Med. 2009; 1(6):62. doi:10.1186/gm62.

(280.) Chen Y, Chen C. DNA copy number variation and loss of heterozygosity in relation to recurrence of and survival from head and neck squamous cell carcinoma: a review. Head Neck. 2008; 30(10):1361-1383. doi:10.1002/hed.20861.

(281.) Goldman M, Craft B, Swatloski T, et al. The UCSC Cancer Genomics Browser: update 2015 [published online ahead of print November 11, 2014]. Nucleic Acids Res. 2014; 43(database issue):D812-7. doi:10.1093/nar/gku1073.

(282.) Coussens LM, Fingleton B, Matrisian LM. Matrix metalloproteinase inhibitors and cancer: trials and tribulations. Science. 2002; 295(5564):2387-2392. doi:10.1126/science.1067100.

(283.) Chien MH, Lin CW, Cheng CW, Wen YC, Yang SF. Matrix metalloproteinase-2 as a target for head and neck cancer therapy. Exp Opin Ther Targets. 2013; 17(2):203-216. doi:10.1517/14728222.2013.740012.

(284.) Dufour A, Overall CM. Missing the target: matrix metalloproteinase antitargets in inflammation and cancer. Trends Pharmacol Sci. 2013; 34(4):233-242. doi:10.1016/j.tips.2013.02.004.

(285.) Moncharmont C, Levy A, Guy JB, et al. Radiation-enhanced cell migration/invasion process: a review [published online ahead of print May 22, 2014]. Crit Rev Oncol Hematol. 2014; 92(2):133-143. doi:10.1016/j.critrevonc. 2014.05.006.

(286.) Pickhard AC, Margraf J, Knopf A, et al. Inhibition of radiation induced migration of human head and neck squamous cell carcinoma cells by blocking of

EGF receptor pathways. BMC Cancer. 2011; 11:388. doi:10.1186/ 1471-2407-11-388.

(287.) Beck C, Piontek G, Haug A, et al. The kallikrein-kinin-system in head and neck squamous cell carcinoma (HNSCC) and its role in tumour survival, invasion, migration and response to radiotherapy. Oral Oncol. 2012; 48(12):1208-1219. doi:10.1016/j.oraloncology.2012.06.001.

(288.) Yang C, Yan J, Yuan G, et al. Icotinib inhibits the invasion of Tca8113 cells via downregulation of nuclear factor kBmediated matrix metalloproteinase expression. Oncol Lett. 2014; 8(3):1295-1298. doi:10.3892/ol.2014.2311.

(289.) Kogashiwa Y, Sakurai H, Kimura T, Kohno N. Docetaxel suppresses invasiveness of head and neck cancer cells in vitro. Cancer Sci. 2010; 101(6): 1382-1386. doi:10.1111/j.1349-7006.2010.01540.x.

(290.) Lin CW, Chou YE, Chiou HL, et al. Pterostilbene suppresses oral cancer cell invasion by inhibiting MMP-2 expression [published online ahead of print August 9, 2014]. Exp Opin Ther Targets. 2014; 18(10):1109-1120. doi:10.1517/ 14728222.2014.947962:1-12.

(291.) Shen H, Zeng G, Tang G, et al. Antimetastatic effects of licochalcone A on oral cancer via regulating metastasis-associated proteases. Tumour Biol. 2014; 35(8):7467-7474. doi:10.1007/s13277-014-1985-y.

(292.) Wolf MA, Claudio PP. Benzyl isothiocyanate inhibits HNSCC cell migration and invasion, and sensitizes HNSCC cells to cisplatin. Nutr Cancer. 2014; 66(2):285-294. doi:10.1080/01635581.2014.868912.

(293.) Hwang YS, Park KK, Chung WY. Epigallocatechin-3 gallate inhibits cancer invasion by repressing functional invadopodia formation in oral squamous cell carcinoma. Eur J Pharmacol. 2013; 715(1-3):286-295. doi:10.1016/j.ejphar. 2013.05.008.

(294.) Chang YC, Chen PN, Chu SC, Lin CY, Kuo WH, Hsieh YS. Black tea polyphenols reverse epithelial-to-mesenchymal transition and suppress cancer invasion and proteases in human oral cancer cells. J Agric Food Chem. 2012; 60(34):8395-8403. doi:10.1021/jf302223g.

(295.) Ding Y, Yao H, Yao Y, Fai LY, Zhang Z. Protection of dietary polyphenols against oral cancer. Nutrients. 2013; 5(6):2173-2191. doi:10.3390/nu5062173.

(296.) Yang JS, Lin CW, Hsin CH, Hsieh MJ, Chang YC. Selaginellatamariscina attenuates metastasis via Akt pathways in oral cancer cells. PloS one. 2013; 8(6): e68035. doi:10.1371/journal.pone.0068035.

(297.) Chang WW, Hu FW, Yu CC, et al. Quercetin in elimination of tumor initiating stem-like and mesenchymal transformation property in head and neck cancer. Head Neck. 2013; 35(3):413-419. doi:10.1002/hed.22982.

(298.) Chien MH, Ying TH, Hsieh YS, et al. Dioscorea nipponica Makino inhibits migration and invasion of human oral cancer HSC-3 cells by transcriptional inhibition of matrix metalloproteinase-2 through modulation of CREB and AP-1 activity. Food Chem Toxicol. 2012; 50(3-4):558-566. doi:10. 1016/j.fct.2011.12.016.

(299.) Peng CY, Yang HW, Chu YH, et al. Caffeic acid phenethyl ester inhibits oral cancer cell metastasis by regulating matrix metalloproteinase-2 and the mitogen-activated protein kinase pathway. Evid Based Complement Alternat Med. 2012; 2012:732578. doi:10.1155/2012/732578.

(300.) Sun Q, Prasad R, Rosenthal E, Katiyar SK. Grape seed proanthocyanidins inhibit the invasiveness of human HNSCC cells by targeting EGFR and reversing the epithelial-to-mesenchymal transition. PloS one. 2012; 7(1):e31093. doi:10. 1371/journal.pone.0031093.

(301.) Lee TK, Poon RT, Wo JY, et al. Lupeol suppresses cisplatin-induced nuclear factor-[kappa]B activation in head and neck squamous cell carcinoma and inhibits local invasion and nodal metastasis in an orthotopic nude mouse model. Cancer Res. 2007; 67(18):8800-8809. doi:10.1158/0008-5472.CAN-07-0801.

(302.) Nohata N, Hanazawa T, Kikkawa N, et al. Caveolin-1 mediates tumor cell migration and invasion and its regulation by miR-133a in head and neck squamous cell carcinoma. Int J Oncol. 2011; 38(1):209-217.

(303.) Huang WC, Chan SH, Jang TH, et al. miRNA-491-5p and GIT1 serve as modulators and biomarkers for oral squamous cell carcinoma invasion and metastasis. Cancer Res. 2014; 74(3):751-764. doi:10.1158/0008-5472.CAN-13-1297.

(304.) Liu CJ, Shen WG, Peng SY, et al. miR-134 induces oncogenicity and metastasis in head and neck carcinoma through targeting WWOX gene. Int j

Cancer. 2014; 134(4):811-821. doi:10.1002/ijc.28358.

Lizandra Jimenez, MS; Sangeeta K. Jayakar, MS; Thomas J. Ow, MD, MS; Jeffrey E. Segall, PhD

Accepted for publication January 14, 201 5.

Published as an Early Online Release June 5, 201 5.

From the Departments of Pathology (Mss Jimenez and Jayakar, and Drs Ow and Segall) and Anatomy and Structural Biology (Mss Jimenez and Jayakar, and Dr Segall), Albert Einstein College of Medicine, Bronx, New York.

Mss Jimenez and Jayakar are co-first authors on this article.

The authors have no relevant financial interest in the products or companies described in this article.

Corresponding author: Lizandra Jimenez, MS, Department of Pathology, Albert Einstein College of Medicine, 1301 Morris Park Ave, Price Center Room 207, Bronx, NY 10461 (e-mail: lizandra. jimenez@phd.einstein.yu.edu).

Reprints: Jeffrey E. Segall, PhD, Department of Pathology, Albert Einstein College of Medicine, 1301 Morris Park Avenue, Price Center Room 201 Bronx, NY 10461 (e-mail: jeffrey.segall@einstein.yu.edu).

* References 57, 77, 152, 215, 217, 221-224.

Caption: Figure 1. Signaling pathways in head and neck squamous cell carcinoma invasion involving the epidermal growth factor receptor (EGFR). The EGFR, activated by EGFR ligands, can activate extracellular signal-regulated kinase (ERK)/activator protein 1 (AP-1), phosphatidylinositol 3-kinase (PI3K)/ protein kinase B (Akt), or Src activity, which all lead to increased invasion in head and neck cancer. The EGFR can be cross-activated by G-protein coupled receptors (GPCRs), whose downstream signaling leads to the release of EGFR ligands from their transmembrane precursors through activity by the members of a disintegrin and metalloproteinase (ADAM) family of proteases.

Caption: Figure 2. Proteins that contribute to invadopodium structure and function. Invadopodia are actin-rich structures that specialize in mediating the degradation of the extracellular matrix. Their formation can be induced by epidermal growth factor receptor (EGFR) signaling. The key components of the core structure are cortactin, tyrosine kinase substrate with 5 SH3 domains (Tks5), neural Wiskott-Aldrich syndrome protein (N-WASP), actinrelated protein 2/3 complex (Arp2/3), noncatalytic region of tyrosine kinase adaptor protein 1 and 2 (Nck-1,2), and cofilin. Adhesion rings, made up of adhesion proteins, such as integrins and integrin-linked kinases (ILKs), are important for the formation and stabilization of invadopodia. Proteases, such as matrix metalloproteinase 2 (MMP2) and matrix metalloproteinase 9 (MMP9), are secreted at invadopodia. Membrane type matrix metalloproteinase (MT1-MMP) can be transported by exosomes, which are secreted from multi-vesicular endosomes. Abbreviations: IQGAP, IQ motif containing GTPase activating protein; MVE, multivesicular endosome.

Caption: Figure 3. Invadopodial matrix degradation assay. UMSCC1 cells, a human oral cavity squamous cell carcinoma cell line, were plated onto an Alexa Fluor-405-labeled gelatin matrix (Life Technologies, Norwalk, Connecticut). After 4 hours, the cells were fixed and stained for cortactin and tyrosine kinase substrate with 5 SH3 domains (Tks5), 2 invadopodia markers. Representative images of the degraded fluorescent matrix (A), Tks5 (B), and cortactin (C), and the merged (cortactin, red; Tks5, green; matrix, blue) staining (D). The merged image shows colocalization of Tks5- and cortactinrich structures associated with degradation holes in the Alexa Fluor-405 matrix (original magnification X380 [A through D]).
Table 1. MicroRNAs (miRNAs) That Affect Invasion in Head and Neck
Squamous Cell Carcinoma

miRNA             Effect        Target
                  on Invasion

hsa-miR-1         Reduction     TAGLN2
hsa-miR-107       Reduction     PRKCE
hsa-miR-29a,b,c   Reduction     LAMC2, ITGA6,
                                  MMP-2, SP1
hsa-miR-99a       Reduction     IGF1R
hsa-miR-126       Reduction     EGFL7, VEGF, FGF2
hsa-miR-133a      Reduction     CAV1, MSN, ARPC5

hsa-miR-138       Reduction     RHOC, ROCK2,
                                  VIM, ZEB2
hsa-miR-140-5p    Reduction     ADAM10
hsa-miR-181a      Reduction     TWIST1
hsa-miR-218       Reduction     LAMB3
hsa-miR-363       Reduction     PDPN
hsa-miR-375       Reduction     MTDH

hsa-miR-491-5p    Reduction     GIT1
hsa-miR-639       Reduction     FOXC1
hsa-miR-21        Increase      DKK2, PDCD4

hsa-miR-134       Increase      WWOX
hsa-miR-155       Increase      SOCS1
hsa-miR-193b      Increase      NF1
hsa-miR-504       Increase      FOXP1
hsa-miR-222       Mixed         BBC3, SOD2

miRNA             Function

hsa-miR-1         Cytoskeleton
hsa-miR-107       Signaling
hsa-miR-29a,b,c   Adhesion, proteolysis,
                    gene expression
hsa-miR-99a       Signaling
hsa-miR-126       Signaling
hsa-miR-133a      Cytoskeleton

hsa-miR-138       Cytoskeleton, EMT

hsa-miR-140-5p    Proteolysis
hsa-miR-181a      EMT
hsa-miR-218       Adhesion
hsa-miR-363       Cytoskeleton
hsa-miR-375       Gene expression

hsa-miR-491-5p    Adhesion
hsa-miR-639       Gene expression, EMT
hsa-miR-21        Signaling, protein
                    synthesis
hsa-miR-134       Cell death
hsa-miR-155       Signaling
hsa-miR-193b      Signaling
hsa-miR-504       Gene expression
hsa-miR-222       Cell death/ROS

miRNA             Source, y

hsa-miR-1         Nohata et al, (178) 2011
hsa-miR-107       Datta et al, (174) 2012
hsa-miR-29a,b,c   Kinoshita et al, (148) 2013; Lu et al, (176)
                    2014; Jia et al, (188) 2014
hsa-miR-99a       Yen et al, (171) 2014
hsa-miR-126       Yang et al, (169) 2014
hsa-miR-133a      Kinoshita et al, (179) 2011; Kinoshita et al,
                    (180) 2012; Nohata et al, (302) 2011
hsa-miR-138       Islam et al, (184) 2014; Liu et al, (185) 2011

hsa-miR-140-5p    Kai et al, (177) 2014
hsa-miR-181a      Liu et al, (187) 2013
hsa-miR-218       Kinoshita et al, (175) 2012
hsa-miR-363       Sun et al, (181) 2013
hsa-miR-375       Hui et al, (189) 2011; Hui et al, (190) 2010;
                    Nohata et al, (191) 2011; Harris et al,
                    (192) 2011; Chen et al, (193) 2012
hsa-miR-491-5p    Huang et al, (303) 2014
hsa-miR-639       Lin et al, (186) 2014
hsa-miR-21        Zhou et al, (97) 2014; Kawakita et al, (170)
                    2013; Reis et al, (195) 2010
hsa-miR-134       Liu et al, (304) 2014
hsa-miR-155       Zhao et al, (173) 2013
hsa-miR-193b      Lenarduzzi et al, (172) 2013
hsa-miR-504       Yang et al, (194) 2012
hsa-miR-222       Jiang et al, (196) 2014; Liu et al, (197) 2009

Abbreviations: EMT, epithelial to mesenchymal transition; ROS,
reactive oxygen species.

Table 2. Ranking of the 25 Genes With the Greatest Number of
Mutations or Copy Number Variation (CNV) in Head and Neck
Squamous Cell Carcinoma

Rank             Mutations

        Gene        CNV      Mutations

1      CDKN2A    -0.77299       66
2      PIK3CA     0.919765      64
3      NOTCH1     0.166341      59
4      EGFR       0.485323      14
5      NOTCH3    -0.04892       14
6      NOTCH2    -0.03327       13
7      FN1       -0.20744       13
8      TLN1       0.009785      12
9      ITGB1     -0.18395       10
10     RAC1       0.373777       9
11     NF1        0.060665       9
12     ZEB2       0.050881       9
13     PIK3CG     0.23092        8
14     HGF        0.203523       8
15     ZEB1      -0.18591        8
16     TLR4       0.242661       7
17     ABL2       0.195695       7
18     IGF1R      0.023483       7
19     COL1A1     0.107632       6
20     ROCK2      0.099804       6
21     COL16A1   -0.03523        6
22     AXL       -0.04501        6
23     THBS1     -0.08023        6
24     EGF       -0.20548        6
25     PIK3R1    -0.34442        6

Rank               CNV

       Gene        CNV      Mutations

1      PIK3CA    0.919765      64
2      CLDN1     0.896282       0
3      PTK2      0.827789       4
4      MTDH      0.704501       2
5      PIK3CB    0.696673       5
6      SNAI2     0.614481       1
7      CTTN      0.571429       4
8      EGFR      0.485323      14
9      GDNF      0.401174       1
10     RAC1      0.373777       9
11     SRC       0.362035       1
12     TWIST1    0.358121       1
13     IGF2BP3   0.34638        1
14     SNAI1     0.320939       0
15     MMP-9     0.318982       0
16     PLCG1     0.313112       5
17     EPO       0.293542       2
18     WNT5B     0.25636        1
19     LPAR5     0.25636        0
20     TLR4      0.242661       7
21     ABL1      0.238748       0
22     LPAR1     0.236791       2
23     FOSL1     0.236791       0
24     PIK3CG    0.23092        8
25     VAV2      0.23092        1
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Author:Jimenez, Lizandra; Jayakar, Sangeeta K.; Ow, Thomas J.; Segall, Jeffrey E.
Publication:Archives of Pathology & Laboratory Medicine
Date:Nov 1, 2015
Words:17749
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