Objective: Tn antigen expression, indicative of aberrant O-glycosylation, is frequently observed in human colorectal cancer (CRC) and is proposed to play key roles in tumorigenesis and cancer progression. Tn antigen appears to produce global effects on O-glycosylation of proteins, particularly on mucins. However, the association between expression of Tn antigen and mucins in CRC remains unclear. Here, we investigated the expression profile of Tn antigen as well as MUC1, MUC2, and MUC4 in a series of human CRC tissues, with the aim of determining whether the Tn antigen has an influence on mucins in the development of CRC. Methods: Expression and localization of Tn antigen, MUC1, MUC2, and MUC4 were determined by multiplex immunohistochemical staining in formalin-fixed, paraffin-embedded colonic sections from Chinese patients with primary CRC. Results: The data show that 65 of 78 (83.3%) patients with CRC were found to express Tn antigen, which was most often stained in the apical cell membranes, mucin droplets, and cytoplasm of the cancer tissues. No Tn antigen was detected in normal colonic tissues. Correspondingly, there were altered patterns in the expression of mucins. Compared with normal colonic tissues that were absent of Tn staining, MUC1 and MUC4 showed an up-regulated and diffuse expression pattern in cancer tissues that expressed Tn antigen, whereas MUC2 expression was significantly decreased in Tn-positive cancer tissues. Conclusions: These results indicate that Tn antigen expression is closely associated with altered expression of mucins in human CRC. Tn antigen may promote development of CRC through affecting the associated mucins expression.
Keywords: O-glycosylation; Tn antigen; colorectal cancer; mucins.
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