Sialosyl‐Tn. A novel mucin antigen associated with prognosis in colorectal cancer patients

Colon cancers typically produce mucin. However, it is not known whether tumor mucin plays a biological role in cancer cell behavior. To address this issue, the expression of a mucin‐associated antigen, sialosyl‐Tn, was examined by immunohistochemical study in 128 primary colorectal carcinoma specimens from 137 patients who underwent curative surgical resection. Antigen expression was correlated with disease‐free and overall 5‐year survival. Sialosyl‐Tn antigen expression occurred in 112 (87.5%) tumors, and was independent of age, gender, tumor location, Dukes' stage, depth of invasion, degree of differentiation, and ploidy status. Survival at 5 years for patients with sialosyl‐Tn‐negative versus sialosyl‐Tn‐positive tumors was 100% versus 73% (P < 0.05) and disease‐free survival was 94% versus 73%, respectively (P = 0.12). Although more advanced Dukes' stage, deeper invasion, and aneuploidy were all associated with poorer overall 5‐year survival, antigen‐negative tumors within each of these groups had much better prognoses than antigen‐positive tumors. Multivariate regression analysis revealed that tumor ploidy (P < 0.001) and sialosyl‐Tn expression (P < 0.05) were the two variables of most importance for predicting both disease‐free and overall survival. The authors conclude that sialosyl‐Tn expression is an independent predictor of poor prognosis in colon cancer, and therefore suggest that qualitative mucin alterations may reflect important differences in the biological behavior of these neoplasms.