Incremento en el numero de celulas positivas para IL-2, receptor de IL-2 e IL-10 en lesiones premalignas del cervix.
Cancer of the cervix is a disease characterized by a long lead-time, with precancerous lesions gradually progressing through recognizable stages before developing into invasive disease. The term "cervical intraepithelial neoplasia" (CIN) was introduced by Richart (1) and implied the concept that a precursor lesion to squamous cell carcinoma represented a single, continuous disease process and makes clear the pre-invasive nature of lesions. The CIN nomenclature divides cervical cancer precursors into CIN 1, CIN 2 and CIN 3, corresponding to mild, moderate and severe dysplasia/carcinoma in situ (2). Cytokine production by T cells is a reliable measure of the quality of cell-mediated immunity (3). The local Th1 and Th2 immune response in tissues could be involved in the progression of cervical neoplasia from mild to severe status. The aim of this study was: 1) to assess the cellular expression of cytokines Th1 (Interleukin-2: IL-2) and Th2 (Interleukin-10: IL-10) in CIN 1, CIN 2 and CIN 3 lesions, normal tissues adjacent to the lesions and normal cervical tissues, and 2) to determine its association with the cellular expression of IL-2 receptor (IL-2R), cytokine serum concentration and human papillomavirus (HPV) infection.
MATERIAL AND METHODS
We evaluated 109 exocervix samples spanning the spectrum from normal cervical tissue to high-grade squamous intraepithelial lesions. Samples were obtained from women who visited the gynecological out-patient clinic of The Manuel Noriega-Trigo Hospital, National Health Clinic "La Victoria" and private practice. Patients were informed about the study procedures and their consents were obtained before enrollment in the investigation, following the ethical committee guidelines of each hospital, the Committee of Bioethical and Biosecurity of FONACIT (Caracas, Venezuela) and the Committee of Bioethical of Medical School (Universidad del Zulia, Maracaibo, Venezuela). Each patient had a personal interview including gynecological and obstetric history and underwent a gynecological examination, Papsmear and a colposcopic examination of exocervix. Sexually active, no pregnant patients with cervix lesions and without immunosuppressant treatment or treatment for HPV were included in this study. Colposcopic examinations were performed under a standard protocol included conventional visual assessment, application of 5% acetic acid, identification of the squamo-columnar junction and transformation zone and recognition of suspected CIN lesions for direct cervical biopsies. A direct biopsy was taken when a colposcopic abnormality was found (n = 50). Biopsies were also taken in normal cervix at least 1cm from the colposcopic lesion (n = 50). Samples from 9 healthy individuals with normal cervix were taken as controls. All specimens were fixed in 10% buffered formalin, embedded in paraffin for 6 [micron]m sections, stained with hematoxilin-eosin and analyzed following Richart's terminoly (1). Colposcopic cervical samples were also included in OCT compound (Tissue Tek, Miles Inc. Diagnostics Division, Kankakee, IL, USA), frozen in dried ice and acetone and kept at -70[degrees]C until use.
The frozen sections (4 [micro]m) from control and patients tissues were fixed with cold acetone and then reacted with a mouse monoclonal anti- human IL-2 receptor or with a rat monoclonal anti-human IL-10 or rat monoclonal anti-human IL-2 antibodies (Pharmigen, Torreyana Rd. San Diego, CA, USA). Mouse and rat immunoglobulins were detected on tissues with FITC-conjugated goat anti-mouse IgG and FITC-conjugated rabbit anti-rat IgG antibodies (Sigma Chemical Co. (St. Louis, MO, USA). Controls included sections subjected to monoclonal antibodies with the same isotype, but against non-relevant antigens as a primary antibodies. Samples were examined using an epifluorescence microscope (Zeiss, Axioskop, Gottingen, Germany).
Detection of HPV DNA in cervical specimens
Exfoliated epithelial cells from all individuals were obtained by cervical brushing and placed in transport medium, supplied with a specimen collection kit of PVHfast 2.0 (Pharma Gen S.A. Madrid, Spain) for the detection of HPV DNA. Cervical specimens are collected to test for HPV DNA through the use of a previously described PCR method that amplified a highly conserved segment (450 bp) of the L1 gene (4, 5). Restriction enzymes analysis was used to determine the HPV types. This kit detects 34 HPV types, including 13 high-risk types (types 16, 18, 31, 33, 35, 39, 45, 51, 52, 56, 58, 59, and 68) and 5 low-risk types (types 6, 11, 42, 43, and 44).
Detection of serum cytokines
All of the participants in the study were asked to provide a blood sample. Whole blood was obtained using a Vacutainer system and an empty vacuum-sealed blood tube without preservative.
Serum was separated by centrifugation, aliquoted and stored at -70[degrees]C until use. Human IL-2, IL-10 and soluble IL-2 receptors were quantified using a commercially available enzyme-linked immunosorbent assay (ELISA) kit (R & D Systems, Minneapolis MN, USA), according to the manufacture's protocol. The amount of cytokines was expressed as pg per milliliter.
Calculations and statistical analysis
Positive cells were counted in tissue areas observed at X 400. Results in the groups are shown as mean [+ or -] SEM. Comparisons between groups were done using the Mann-Whitney test and ANOVA. For correlations between two variables, Pearson's correlation was used. Two tailed p < 0.05 was interpreted as being statistically significant.
[FIGURE 1 OMITTED]
Cytokine positive cells in tissues
Histological analysis showed the following pathological categories: CIN 1 (n = 36), CIN 2 (n = 6), CIN 3 (n = 8). In general, increased numbers of IL-2, IL-10 or IL-2R positive cells were found in tissues from patients with CIN when compared to adjacent normal tissues and normal controls. This increment was observed in the different grades of CIN, however, in some instances non significant differences were observed (Figs. 1, 2 and 3). Cytokine-positive cells were observed in 84% of the patient's lesions and in 10% of controls (Table I). Apparently, normal tissues taken near the site of the lesion showed increased number of cytokine- positive cells when compared to normal control tissues (Figs. 1, 2 and 3). The number of cytokine-positive cells was associated to the severity of the cervical lesion; however, irregular expression was observed in tissues near the lesion (Fig. 4). The expression of IL-2 was correlated with the expression of IL-2R (p < 0.0001) and IL-10 (p < 0.0001). In addition, the expression of IL-10 was correlated with the expression of IL-2R (p < 0.0001) (Table II). Cytokine-positive cells were localized in epithelium and subepithelium and in some instances, clusters of positive cells were observed (Fig. 5).
[FIGURE 2 OMITTED]
Cytokine levels in serum Serum sIL-2R levels were found to be not significantly elevated in patients with CIN compared to normal levels. Levels of IL-2 and IL-10 were undetectable using ELISA (Table III).
Twenty percent of the patients were positive for HPV as shown by the detection of HPV DNA. Twenty one percent of all patients positive for tissue cytokines were also positive for HPV. Ninety percent of HPV-positive patients were positive for tissue cytokine expression (Table I). HPV/cytokine-positive patients were mainly CIN 1 and CIN 3 (Fig. 6).. There were not significant differences when tissue cytokine expression, was compared with positive or negative HPV-infection status (Fig. 7). In controls 33 % were HPV positive. Seven out of 10 samples from HPV-infected patients and 2 out of 3 from infected controls, were tested for HPV types. High-risk type infection was detected in patients (16.31) and low-risk type infection (6, 11) was detected in controls (Table IV).
[FIGURE 3 OMITTED]
Cytokine production is a reliable measure of the quality of cell-mediated immunity. Host factors are critical in regulating tumor growth and cytokines that modulate immunologic control may be of particular importance (3). The Th 1 cytokine inter leukin 2 is immunostimulatory and it is thus capable of limiting tumor growth (6). The Th 2 cytokine interleukin 10 is immunoinhibitory and it is capable of stimulating tumor growth (6). In the present study an increased number of cells positive for IL-2, IL-2R and IL-10 was showed in cervical samples from patients with different grades of CIN. The presence of those cells was associated with the severity of the cervical lesion, suggesting a role for IL-2 and IL-10 in the evolution of the dysplasia. A previous report has demonstrated a low density of IL2-positive cells in high-grade squamous intraepithelial lesions compared to normal tissues (7); conversely, increased number of IL-2-positive cells was found in CIN 3. This finding could be related to the increased expression of IL-10, a cytokine with IL-2-stimulatory effect (8). The presence of both cytokines in the dysplasia and the high correlation found between them are consistent with that explanation.
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The presence of IL-2 and IL-2R positive cells in the cervical microenvironment suggests the interaction of IL-2 with its receptor. This could promote nonspecific tumor killing by activated macrophages, lymphokine-activated killer cells (9) and tumor-infiltrating lymphocytes (10). Because of its stimulatory activity on a variety of immune cell types, IL-2 has been studied extensively in the augmentation of the innate immune response to malignant disease (11, 12). In addition, signal transduction pathways triggered in IL-2R-expressing solid tumors could be mediated by an alternative mechanism. Stem Cell Factor -activated c-Kit induces phosphorylation of the IL-2R beta chain in the absence of IL-2 in HPV-associated cervical cancer cells (13). Thus, the presence of increased numbers of IL-2R positive cells in cervical tissues during CIN could represent an important target for IL-2 and different stimuli produced in the uterine microenvironment.
Interleukin-10 is widely known as an immunosuppressive cytokine by virtue of its ability to inhibit macrophage-dependent antigen presentation, T-cell proliferation, and Th1 cytokine secretion (6). The increased expression of IL-10 in the different grades of CIN found in this study, could contribute to the immunodeviation, that could participate in the immunoescape of preneoplastic cervical keratinocytes, and represent an antagonistic activity compared to the effect of IL-2. Consistent with our results, it has been reported that the expression of IL-10 increased with the severity of the lesion to a maximal level in high-grade cervical squamous intraepithelial lesions (14). However, several studies have challenged the perception of IL-10 solely as an immunosuppressive cytokine. In this regard, it has been reported that IL-10 in combination with IL-2 was able to consistently increase the cytotoxic activity of human papillomavirus E7-specific CD8(+) cytotoxic T lymphocytes. In addition, IL-10 in combination with IL-2 after antigen stimulation, increased the intracellular expression of Th1 cytokines (i.e., IFN-gamma and IL-2) in CD8 positive T cells (8). IL-2 can also induce the production of IL-10 by human T cells (15). In addition, IL-10 increases the natural killer cell anticancer activity by enhancing the levels of cell activation/cytotoxicity-related genes (eg secretogranin, TIA-1, HMG-1, interferon-inducible genes) and the expression of cell migration-related genes (e.g. L-selectin, vascular endothelium growth factor receptor1, plasminogen activator, tissue; formyl peptide receptor, lipoxin A4 receptor) (16). IL-10 has also been shown to induce IL-2R[alpha] expression in inflammatory processes and viral infections (17). Taking together these data, it is possible to speculate that the increased levels of IL-2-positive cells, IL-2R positive cells and IL-10-positive cells and the high correlation between those cells in CIN could represent an IL-2/IL-2R - inducing effect of IL-10 and a mechanism to escape from an invasive cancer. The association of IL-2/IL-10 found in this study, probably is not going to be preserved in invasive carcinoma, since, low levels of IL-10 in invasive carcinoma compared with premalignant biopsies have been reported (18). An increased number of cytokine-positive cells in normal tissues adjacent to the lesions was also found, suggesting that the cytokine expression is a phenomenon not limited to the lesion, but it may be generalized in the cervical tissues. This could represent a chemotactic effect from the CIN on dendritic cells and leukocytes capable of producing these cytokine profiles (19-21).
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[FIGURE 6 OMITTED]
Lymphocytes are the main IL-2 producers, however in normal tissues, and several tumours, including stomach, renal and spinocellular cancer and squamous cell carcinomas of the head and neck, IL-2 seems to be present and stimulate cell proliferation (22, 23). Thus, the presence of some cytokine positive cells observed in this study could represent epithelial cells or other types of cells.
[FIGURE 7 OMITTED]
Human papillomavirus type 16 is a major factor in cervical carcinogenesis (24). Previously it has been reported an increased production of IL-10 and decreased production of IL-2 by peripheral blood mononuclear cells in women with CIN, associated with localized or extensively spread of HPV infection, and suggesting that a pronounced shift from Th 1 to Th 2 cytokine production is associated with extensive HPV infection (25). In general, a shift from a Th1 (IL-2) and gamma interferon (IFN-) to a Th2 (IL-4 and IL-10) cytokine profile is associated with poor prognosis for patients with HPV-associated cervical lesions (25). This study showed that patients were infected mainly by HPV type 16, however, the Th1 to Th2 shift at the tissue level was not found. This could be related to the fast that only 20% of individuals were positive for HPV and extensive HPV infection was not observed. This percentage agrees with prevalence studies showing that between 5% and 20% of the general population has HPV DNA detectable in cervical samples (26) and that in most cases, infection with HPV is transient and may or may not be associated with cervical abnormalities of low squamous intraepithelial lesions (27). The low frequency (20%) observed in the patients in our population agree with other studies which reported 9.9 to 12.5 % in the occidental Venezuelan population (28, 29). High frequency of HPV infection in controls (33%) was observed when compared to patients (20%), however, only low risk virus types were found, suggesting low risk to have CIN. The persistence of IL-2 positive cells found in these patients could have a beneficial effect limiting HPV-induced tumor growth. In this regard, local use of IL-2 has been successful in cervical condylomatosis therapy (30). IL-10 positive cells could also play a beneficial role in the progression of premalignant lesions during HPV infection, since elevated levels of IL-10 have been associated with the absence of cervical lesions among HPV-infected women (31). The cytokine profile and cytokine values were similar in HPV- infected and noninfected patients suggesting that virus infection does not alter the local cytokine production during the course of uterine premalignant lesions.
The tissue cytokine expression was not reflected at the serum level. IL-2 and IL-10 were not detectable in the serum using enzyme-linked immunosorbant assays. Only soluble receptor for IL-2 was detected, but no significant differences were observed when compared to the normal controls. This suggests that increased expression of cytokines in CIN was a local phenomenon and it is consistent with the association of excessive circulating levels of cytokines with invasive cancer (32). Thus, the serum cytokines values found in this study most likely are related to the conditions of the patients where noninvasive neoplasia is detected.
In conclusion, it has been reported the notion that the progression of cancer of the cervix is associated with a preferential constraint on the development of a Th 1 cellular mediated response, which is necessary to efficiently eliminate (pre)neoplastic cells. In our study premalignant lesions did not show a preferential Th1 or Th2 cytokine profile and elevated number of cells Th1 and Th2 positives were observed in the different grades of CIN. The presence of these cells were not associated either with increased serum profile of cytokines or HPV infection. This could represent a transitory stage with further locally reduced cellular Th1 immunity and invasive cervical carcinoma or, represent a cytokine combination with a potential anti-tumor effect. These data reinforce the need to perform further studies to determine changes on the local IL-2/IL10 profile in invasive cancer.
This manuscript was supported by FONACIT (Caracas, Venezuela). The authors thank Drs. Esther Rosenblum and David Munroe (Laboratory of Molecular Technology, NCI-Frederick, MD, USA) for their review of this manuscript.
Received: 10-01-2008. Accepted: 29-05-2008.
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Raimy Mindiola , Diana Callejas , Jose Nunez-Troconis , Mary Araujo , Mariela Delgado  y Jesus Mosquera .
 Laboratorio Regional de Referencia Virologica, Facultad de Medicina, Universidad del Zulia,  Departamento de Ginecologia y Obstetricia, Hospital Chiquinquira,  Departamento de Patologia, Hospital Chiquinquira e  Instituto de Investigaciones Clinicas "Dr. Americo Negrette", Facultad de Medicina, Universidad del Zulia. Maracaibo, Venezuela.
Corresponding author: Jesus A Mosquera. Apartado Postal 23. Maracaibo 4001-A. Zulia, Venezuela. Telephone number: 58-261-7597247. Fax number: 58-261-7597247. E mail: email@example.com
TABLE I TISSUE CYTOKINES AND HPV INFECTION IN SAMPLES FROM PATIENTS AND NORMAL CONTROLS Positive Controls Patients Relation % Relation % Cytokine/total * 1/9 11 42/50 84 HPV/total * 3/9 33 10/50 20 Cytokine/total HPV 1/3 33 9/10 90 HPV/total cytokine 1/1 100 9/42 21 * Total individual in controls or patients. TABLE II CORRELATION BETWEEN IL-2, IL-2R AND IL-10 EXPRESSIONS IN UTERINE TISSUES Pearson r P values IL-2 / IL-2R 0.713 P < 0.0001 IL-2 / IL-10 0.742 P < 0.0001 IL-10/ IL-2R 0.709 P < 0.0001 TABLE III CYTOKINE SERUM LEVELS IN NORMAL AND PATIENTS WITH PREMALIGNANT LESIONS OF UTERINE CERVIX Controls Patients IL-2 ND ND IL-2R 99.23 [+ or -] 43.86 * 160.37 [+ or -] 34.01 IL-10 ND ND * pg/mL; ND: not detectable. TABLE IV HPV TYPES AND PREMALIGNANT LESION DISTRIBUTION IN SAMPLES OF UTERINE CERVIX FROM NORMAL CONTROLS AND PATIENTS Controls Patients HPV/total individuals 3/9 10/50 Typification/total HPV 2/3 * 7/10 ** HPV types 6, 11 CIN 1 (n=2: 16, 31) CIN 2 (n=1: 16/11) CIN 3 (n=4: 16,16, 16, 16/31) * All samples were negative for tissue cytokine expression. ** All samples were positive for cytokine expression.