Background: The sialyl-Tn (sTn) antigen is a mucin-associated carbohydrate antigen expressed by numerous human carcinomas, and is also claimed to be a prognostic factor in colorectal cancer. But the associations between sTn and colorectal cancer remain elusive and controversial. Here, we investigated the expression profile of sTn antigen in a series of human colorectal tissue samples including normal colon, colorectal adenomas, and colorectal carcinomas (CRCs), with an aim to analyzing whether sTn plays a role in the progression and development of Chinese patients with CRCs.
Methods: Immunohistochemical staining of sTn antigen was performed in formalin-fixed, paraffin-embedded colonic sections from 4 healthy controls, 44 patients with colorectal adenomas, and 186 patients with primary CRCs.
Results: No sTn antigen was detected in normal colonic tissues. There were 41 of 44 patients with colorectal adenomas (93.2%), and 141 of 186 patients with CRCs (75.8%) found to express sTn antigen. The patterns of sTn localization were different in adenomas and carcinomas of colonic tissues. Colorectal adenomas showed predominant supranuclear distribution of sTn antigen, while carcinomas revealed apical membrane, mucin droplet and diffuse cytoplasmic localization. Notably, sTn was significantly associated with the degree of differentiation (P = 0.006) and perineural invasion (P = 0.041) of the tumors, but was independent of age, gender, tumor location, depth of penetration, status of lymph nodes, lymphovascular invasion and TNM stage.
Conclusions: These results indicate that sTn may play a role in initiating colorectal carcinogenesis and promoting tumor progression. Determination of sTn expression and localization may assist in evaluating malignant status of colorectal lesions.
Keywords: colorectal adenoma; colorectal carcinoma; expression pattern; sTn antigen.