DETECTION OF TN, SIALOSYL-TN AND T-ANTIGEN IN HEREDITARY NONPOLYPOSISCOLORECTAL-CANCER

The simple mucin-type carbohydrate antigens Tn, sialosyl-Tn, T and the 'cryptic' sialylated variant of the last represent the mucin core oli gosaccharide structures that are produced in the initial steps of the mucin biosynthetic pathway. Utilizing monoclonal antibodies anti-Tn an tigen (HB-Tn1), anti-sialosyl-Tn antigen (HB-STn1), anti-T antigen (HB -T1) and the biotinylated Amaranthus caudatus agglutinin (ACA), we hav e investigated the expression of the simple mucin-type carbohydrate an tigens in hereditary nonpolyposis colorectal cancer (HNPCC; 15 cases) compared with sporadic colorectal cancer (CRC; 60 cases) and normal co lonic mucosa (30 cases). A variable positivity of Tn, sialosyl-Tn, T a nd the cryptic sialylated form of this latter antigen was encountered in both HNPCC and sporadic CRC cases; in addition, in normal colonic m ucosa a constant reactivity was encountered only for Tn and the crypti c sialylated form of T, while negative results were always obtained fo r sialosyl-Tn and T antigens. Statistical analysis, performed using a Chi-square test, showed significantly lower (P = 0.037) expression of sialosyl-Tn and higher (P = 0.022) expression of T in HNPCC than in sp oradic CRC, suggesting a greater presence of beta 1,3 galactosyltransf erase activity in HNPCC than in sporadic CRC. We were unable to identi fy a peculiar phenotype for HNPCC with simultaneous evaluation of reac tivity for HB-Tn1, HB-STn1, HB-T1 and ACA; the biological significance of the preferential expression of T antigen in HNPCC remains to be in vestigated.