Mucin expression in gastric cancer: reappraisal of its clinicopathologic and prognostic significance.
MATERIALS AND METHODS
Tumor Samples and Patient Population
We studied a cohort of 412 gastric cancer patients who underwent gastrectomy with lymph node dissection at Pusan National University Hospital between 2005 and 2007. The group comprised 286 men and 126 women with a mean age of 58.5 years (range, 42-75 years). Standard formalin-fixed, paraffin-embedded sections were obtained from the Department of Pathology, Pusan National University Hospital, and the National Biobank of Korea, Pusan National University Hospital. The study was approved by the institutional review board. None of the patients received preoperative radiotherapy and/or chemotherapy. We assessed the several clinicopathologic factors (tumor site, gross appearance and size, histologic classification [ie, intestinal or diffuse], and lymphovascular invasion) according to the Korean standardized pathology report for gastric cancer (14) and the Japanese classification of gastric carcinoma, 3rd English edition, (15) and made staging (depth of invasion, lymph node status) based on the American Joint Committee on Cancer Staging Manual, 7th edition. (16) The clinical outcome of each patient was followed from the date of surgery to the date of death or March 1, 2011. The follow-up period ranged from approximately 1 to 74 months (average, 46.0 months). Cases lost to follow-up or with death from any cause other than gastric cancer were censored for the analysis of survival rates.
Immunohistochemical Staining for Mucin Phenotypes
Sections were dewaxed and rehydrated according to the standard procedure and washed with phosphate-buffered saline. For immunohistochemical staining, sections were heated in a 600-W microwave oven twice for 5 minutes in 0.01 M citrate buffer (pH 6.0). Sections were immersed in 3% [H.sub.2][O.sub.2] to quench endogenous peroxidase activity, and unspecified binding was blocked in 5% normal goat serum (0.1% bovine serum albumin in phosphate-buffered saline). Immunohistochemical staining was performed using the avidin-biotin peroxidase complex method with amino-ethylcarbazole as a chromogen, using the Vectastain ABC elite kit (Vector Laboratories, Burlingame, California) according to the manufacturer's instructions. Sections were counterstained with Mayer hematoxylin solution. Immunohistochemical staining was carried out with monoclonal antibodies against the mucin antigen (Table 1).
MUC5AC and MUC6 are markers of gastric foveolar cells and antral/cardiac mucous glandular cells, respectively, and they reflect gastric phenotypes (Figure 1, A and B). MUC2 and CD10 exhibit the typical intestinal epithelial cell phenotype, decorating goblet cells and the brush border of intestinal absorptive epithelial cells, respectively (Figure 1, C and D). Adenocarcinomas with at least 10% reactivity for each mucin gene antibody were identified as positive as previously reported. (7,8,13) Mucin phenotypes were further subdivided into gastric (only gastric mucin positive) and gastric-predominant gastrointestinal phenotypes and intestinal (only intestinal mucin positive) and intestinal-predominant gastrointestinal phenotypes and null type based on the combination of predominant patterns of MUC5AC, MUC2, MUC6, and CD10 staining according to Tsukashita et al. (17) We defined gastric cancer with gastric mucin predominant type (GC-GP) as gastric type plus gastric-predominant gastrointestinal phenotypes (gastric type + gastric-predominant gastrointestinal type) and gastric cancer with intestinal mucin predominant type (GC-IP) as intestinal type plus intestinal-predominant gastrointestinal phenotypes (intestinal type + intestinal-predominant gastrointestinal type) for comparison based on the predominant mucin expression.
Clinicopathologic features were analyzed by Student t test, the [chi square] test, or Fisher exact test to test for differences among the mucin phenotypes. Cumulative survival plots were obtained using the Kaplan-Meier method, and significance was compared using the log-rank test. Prognostic factors were identified using the Cox regression stepwise method (proportional hazard model) adjusted for the patients' age, gender, tumor site, and morphologic type (intestinal versus diffuse). Statistical significance was set at P < .05. Statistical calculations were performed with SPSS version 10.0 for Windows software (SPSS Inc., Chicago, Illinois).
Clinicopathologic Significance of Mucin Expression in Gastric Cancer
Of the 412 specimens, 67.5% (278 of 412), 44.9% (185 of 412), 35.4% (146 of 412), and 20.6% (85 of 412) were positive for MUC5AC, MUC6, MUC2, and CD10, respectively (Figure 2, A through D). As shown in Table 2, 63.8% (262 of 412), 24.5% (102 of 412), and 11.7% (48 of 412) of gastric cancers were classified as having GC-GP, GC-IP, and null phenotypes, respectively, on the basis of the predominant pattern of mucin expression.
Mucin phenotype was significantly correlated with sex, size, depth of invasion, gross type, histologic type, and lymphovascular invasion. The men had more null phenotype than GC-GPs and GC-IPs (P = .004). The tumor size of GC-GPs was smaller (P = .04) than that of GC-IP and null phenotypes. Early gastric cancer (EGC; limited to the mucosa and submucosa) showed more GC-GPs than advanced gastric cancer (invasion into muscularis propria and beyond) (P = .01). Diffuse histologic type was more strongly associated with GC-GP than with GC-IP or null phenotypes (P = .02). In addition, the presence of lymphovascular emboli was more related to GC-IP and null phenotypes than to GC-GP phenotype (P = .001). Also, there was a tendency of more lymph node metastasis in the GC-IP and null phenotypes than the GC-GP phenotype (P = .09) (Table 2).
Survival of Gastric Cancer With Respect to Mucin Expression
In overall and advanced gastric cancers, the depth of invasion and nodal status were significantly associated with cumulative survival (P < .001) (Figures 3, A through C, and 4, A through C). Alternatively, there was no association between mucin phenotype and survival in the cases of overall gastric cancer (P= .41) or advanced cancers (P= .29).
In contrast, there was a significant correlation between mucin phenotype and survival in EGC (P= .02) (Figure 5, A through C). The GC-GPs showed longer survival rate than GC-IP (P = .01) and null phenotypes (P = .01) in EGC. Furthermore, MUC5AC-positive EGCs had a longer survival rate than MUC5AC-negative EGCs (P = .009) (Figure 6, A through C). The expression of MUC5AC was identified as an independent prognostic factor in EGC adjusted for age, sex, histologic classification, tumor location, depth of invasion, and lymph node metastasis in the Cox regression proportional hazard model (P = .045) (Table 3). Notably, there was no significant association between survival rate and the expression of other mucins (ie, MUC2, MUC6, CD10) or mucin phenotypes (data not shown).
The present study demonstrates that the expression of a gastric mucin phenotype (especially MUC5AC expression) is significantly associated with favorable outcome, and should be considered as a possible prognostic predictor in the gastric cancer, especially in the EGCs.
From the perspective of carcinogenesis, the mucin plays an important role in the development of neoplasm. Alterations in mucin expression or glycosylation of tumor cells control the local microenvironment, playing a role in invasion and metastasis of tumor cells. (4) In addition, mucins regulate the differentiation, proliferation, and tumor suppression of tumor cells. (4)
It has been reported that EGC exhibits a gastric mucin phenotype independently regarding the histologic type, whereas advanced gastric cancers have a higher tendency to express an intestinal phenotype. (18-20) In the present study, the gastric mucin phenotype was more commonly expressed in EGC whereas the intestinal phenotype was more common in advanced gastric cancer, which is concordant with previous reports. (18-20) In addition, Saito et al (21) revealed that small intestinal-type EGCs (<1 cm) commonly express gastric mucin but transform into more undifferentiated and intestinal phenotypes with progression. Taking into account previous reports and our study, we confirm that during the progression of gastric cancer, there is a frequent phenotypic switch, with a mucin intestinal phenotype being acquired in most gastric cancers.
The clinical and, particularly, the prognostic significance of the mucin immunophenotype of gastric cancers are debated (Table 4). Lee et al (6) reported that the mucin intestinal phenotype was associated with a significantly better prognosis. In contrast, Wakatsuki et al (7) found that the same immunophenotype was associated with a significantly worse prognosis and a higher rate of postoperative liver metastasis. Notably, many different antibodies have been used to evaluate mucin expression, as well as different cutoff values for the definition of mucin positivity, leading us to speculate that these differences are responsible for the inconsistent results.
Compared with previous findings, (5-13) no relationship was found in our study between survival and mucin phenotypes in overall gastric cancer or in the advanced cancer subgroup. Instead, there was a significant relationship solely in EGC; expression of a mucin gastric phenotype was associated with a longer survival rate in EGC. Furthermore, foveolar gastric mucin expression, for example MUC5AC, was also associated with longer survival. Concordant with other reports, depth of invasion and lymph node metastasis were noted as prognostic markers in our entire cohort and the advanced tumor subgroup. (16) However, in the EGCs of the present study, lymph node metastasis and depth of invasion (mucosa versus submucosa) were determined to be not predictive of outcome in EGC. Alternatively, retained MUC5AC expression was associated with extended survival in EGC, and this independently of the depth of invasion. It is noteworthy that in contrast to our results, Koseki et al (22) reported that in their experience, the expression of a gastric phenotype was associated with increased risk of lymph node metastasis among intestinal-type EGC. Yet, in contrast to these 2 reports and in agreement with our data, Wang et al (10) noted that in a series of 76 gastric cancers, MUC5AC expression was associated with a favorable prognosis. In addition, others have detected an increased number of genetic alterations in adenocarcinomas with an intestinal mucin phenotype compared with those with a gastric mucin phenotype. (23-24) For example, EGCs with an intestinal mucin phenotype have been shown to display more p53 and nuclear [beta]-catenin expression and undergo more frequent chromosomal alteration compared with those with a gastric mucin phenotype, suggesting a more aggressive behavior. And our findings suggest that MUC5AC expression can be used to predict outcomes in EGC. However, out study is not sufficient for ending conflicts about the relationship between the mucin phenotype and the gastric cancer prognosis. Because the reasons underlying these discrepancies are still undetermined, additional molecular and clinical studies are needed to sort out these results.
This study was supported by grant 0920050 from the National R&D Program for Cancer Control, Ministry for Health, Welfare and Family Affairs, Republic of Korea, and a clinical research grant from Pusan National University Hospital 2011.
Caption: Figure 1. Mucin expression in gastric mucosa. MUC5AC expression in gastric foveolar epithelial cells (A). MUC6 expression in antral mucous glands (B). MUC2 reactivity in goblet cells of intestinal metaplastic cells (C). CD10 positivity on the brush border of intestinal metaplastic cells (D) (original magnifications X200).
Caption: Figure 2. Mucin expression in gastric adenocarcinoma. MUC5AC-positive (A), MUC6-positive (B), MUC2-positive (C), and CD10-positive (D) gastric adenocarcinoma (original magnifications X200).
Caption: Figure 3. Overall survival rates for gastric cancer according to the depth of invasion in overall gastric cancer (A), early gastric cancer (B), and advanced gastric cancer (C). The survival rate was higher in early-stage gastric cancer. Abbreviations: M, mucosa; MP, muscularis propria; SE, serosa exposed; SM, submucosa; SS, subserosa.
Caption: Figure 4. Overall survival rates according to lymph node metastasis status for all gastric cancers (A), early gastric cancers (B), and advanced gastric cancers (C).
Caption: Figure 5. Overall survival rates for gastric cancer according to mucin phenotypes for all cancers (A), early gastric cancers (B), and advanced gastric cancers (C). The GC-GP phenotype showed longer survival rates compared with the GC-IP (P =.01) and null phenotypes (P = .01). Abbreviations: GC-IP, gastric cancer with intestinal mucin predominant; GC-GP, gastric cancer with gastric mucin predominant.
Caption: Figure 6. Overall survival rates for gastric cancer according to MUC5AC expression for all cancer (A), early gastric cancers (B), and advanced gastric cancers (C). MUC5AC(+) early gastric cancer demonstrated a longer survival rate than MUC5AC(-) lesions (P = .009).
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Dae Hwan Kim, MD, PhD; Nari Shin, MD; Gwang Ha Kim, MD, PhD; Geum Am Song, MD, PhD; Tae-Yong Jeon, MD, PhD; Dong-Heon Kim, MD, PhD; Gregory Y. Lauwers, MD; Do Youn Park, MD, PhD
Accepted for publication August 30, 2012.
From the Departments of Surgery (Drs D. H. Kim, Jeon, and D.-H. Kim), Pathology (Drs Shin and Park), and Internal Medicine (Drs G. H. Kim and Song), Pusan National University Hospital and Pusan National University School of Medicine and BioMedical Research Institute, Pusan National University Hospital, Busan, Korea; and the Department of Pathology, Massachusetts General Hospital and Harvard Medical School, Boston (Dr Lauwers).
The authors have no relevant financial interest in the products or companies described in this article.
Reprints: Do Youn Park, MD, PhD, Department of Pathology, Pusan National University Hospital and Pusan National University School of Medicine, 1-10 Ami-Dong, Seo-Gu, Busan 602-739, Korea (e-mail: firstname.lastname@example.org).
Table 1. Primary Antibodies Used in This Study (a) Primary Antibody (Clone) Dilution MUC2 (CLH2) 1:500 MUC5AC (CLH5) 1:500 MUC6 (Ccp58) 1:500 CD10 (56C6) 1:100 (a) All antibodies are from Novocastra Laboratories, Newcastle, United Kingdom. Table 2. Relationship Between Mucin Phenotypes With Clinicopathologic Characteristics in Gastric Cancers Mucin Phenotypes No. of Cases GC-GP GC-IP Age y 58.5 [+ or -] 11.3 59.4 [+ or -] 10.4 Sex Male 286 171 72 Female 126 91 30 Tumor size, cm 3.55 [+ or -] 0.15 4.21 [+ or -] 0.28 Location Upper/middle 219 143 55 Lower 193 120 46 Invasion depth M, SM 223 157 44 MP, SS, SE 189 106 57 Gross type Elevated/flat/ 283 189 65 depressed Excavated 129 74 36 Histologic type Intestinal + 251 147 71 mixed Diffuse 161 116 30 Perineural invasion Negative 278 182 65 Positive 134 81 36 Lymphovascular emboli Negative 259 183 53 Positive 153 80 49 Lymph node metastasis (a) Negative 244 164 57 Positive 168 99 44 Mucin Phenotypes Null P Age y 60.5 [+ or -] 13.3 .49 Sex Male 43 .004 Female 5 Tumor size, cm 4.32 [+ or -] 0.43 .04 Location Upper/middle 21 .38 Lower 27 Invasion depth M, SM 22 .01 MP, SS, SE 26 Gross type Elevated/flat/ 29 .16 depressed Excavated 19 Histologic type Intestinal + 33 .02 mixed Diffuse 15 Perineural invasion Negative 31 .61 Positive 17 Lymphovascular emboli Negative 24 .001 Positive 24 Lymph node metastasis (a) Negative 23 .09 Positive 25 Abbreviations: GC-GP, gastric cancer with gastric mucin predominant type; GC-IP, intestinal type early gastric cancer with intestinal mucin predominant type; M, mucosa; MP, muscularis propria; SE, serosa; SM, submucosa; SS, subserosa. (a) Compared between GC-GP versus GC-IP + null type. Table 3. Multivariate Survival Analysis With Cox Regression Model in Early Gastric Cancers Variable B SE Age ([less than or equal to] 59 -1.401 0.798 versus >59) Sex (male versus female) 0.652 0.788 Site (upper and middle versus 0.378 0.622 lower) Histologic type (intestinal versus 0.319 0.809 diffuse) Depth of invasion (mucosa versus -0.134 0.617 submucosa) Lymph node metastasis (positive -0.448 0.714 versus negative) MUC5AC (positive versus negative) 1.253 0.626 Variable HR (95% CI) P Age ([less than or equal to] 59 0.246 (0.052-1.177) .08 versus >59) Sex (male versus female) 1.920 (0.410-8.999) .41 Site (upper and middle versus 1.460 (0.431-4.945) .54 lower) Histologic type (intestinal versus 1.376 (0.282-6.713) .69 diffuse) Depth of invasion (mucosa versus 0.875 (0.261-2.929) .83 submucosa) Lymph node metastasis (positive 0.639 (0.158-2.590) .53 versus negative) MUC5AC (positive versus negative) 3.500 (0.026-11.937) .045 Abbreviations: CI, confidence interval; HR, hazard ratio. Table 4. Reported Datasets About Relationship Between Mucin Expression and Survival in Gastric Cancer Source, y No. Antibodies Positivity, % Present study 412 MUC5AC, MUC6, 10 MUC2, CD10 Toki et al, (5) 2010 95 MUC5AC, HGM, MUC6, 5 M-GGMC-1, MUC2, CD10 Lee et al, (6) 2009 106 HGM, Con A, MUC2, 5 MUC6 Wakatsuki et 97 MUC5AC, MUC6, 10 al, (7) 2008 MUC2, CD10 Lee et al, (8) 2007 150 MUC1, MUC5AC, MUC6, 10 MUC2, CD10 Wang et al, 76 MUC1, MUC5AC 5 (10) 2003 Pinto-de-Sousa et 94 MUC5AC, MUC6, 5 al, (12) 2002 MUC2, MUC1 Tajima et 136 HGM, MUC2, 10 al, (13) 2001 MUC6, CD10 Lee et al, (11) 2001 300 MUC5AC, MUC6, 20 MUC2, MUC1 Source, y Phenotypes Survival Present study GC-GP, GC-IP, null GC-GP and MUC5AC(+) has good survival in EGC Toki et al, (5) 2010 G, GI, I, U No correlation Lee et al, (6) 2009 G, GI, I, U I phenotype has good survival Wakatsuki et G, GI, I, U I phenotype has poor al, (7) 2008 survival Lee et al, (8) 2007 G, GI, I, U G, GI phenotype have poor survival Wang et al, N/A Muc1(+)/Muc5AC(-) has (10) 2003 poor survival Pinto-de-Sousa et N/A No correlation al, (12) 2002 Tajima et G, GI, I, U G phenotype has poor al, (13) 2001 survival Lee et al, (11) 2001 N/A Muc1(+) has poor survival Abbreviations: EGC, early gastric cancer; G, gastric mucin phenotype; GC-GP, gastric cancer with gastric mucin predominant type; GC-IP, intestinal type early gastric cancer with intestinal mucin predominant type; GI, gastric-intestinal mucin phenotype; HGM, human gastric mucin; I, intestinal mucin phenotype; N/A, not assessed; U, unclassified mucin phenotype.
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|Author:||Kim, Dae Hwan; Shin, Nari; Kim, Gwang Ha; Song, Geum Am; Jeon, Tae-Yong; Kim, Dong-Heon; Lauwers, Gr|
|Publication:||Archives of Pathology & Laboratory Medicine|
|Date:||Aug 1, 2013|
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