In cancer, mucins are aberrantly O-glycosylated and consequently, they express tumor-associated antigens such as the Tn determinant (α-GalNAc-O-Ser/Thr). They also exhibit a different pattern of expression as compared to normal tissues. In particular, MUC6, which is normally expressed only in gastric tissues, has been detected in intestinal, pulmonary, colorectal and breast carcinomas. Recently, we have shown that the MCF7 breast cancer cell line expresses MUC6-Tn glycoproteins in vivo. Cancer-associated mucins show antigenic differences from normal mucins and, as such, they may be used as potential targets for immunotherapy. In order to develop anti-cancer vaccines based on the Tn antigen, we prepared several MUC6-Tn glycoconjugates. To this end, we performed the GalNAc enzymatic transfer to two recombinant MUC6 proteins expressed in E. coli by using UDP-Nacetylgalactosamine: polypeptide N-acetylgalactosaminyltransferases (ppGalNAc-Ts), which catalyze in vivo the Tn antigen synthesis. We used either a mixture of ppGalNAc-Ts from MCF7 breast cancer cell extracts or a recombinant ppGalNAc-T1. In both cases, we achieved the synthesis of MUC6-Tn glycoconjugates at a semi-preparative scale (mg amounts). These glycoproteins displayed a high leve
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