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ST6GalNAc-I, the sialyltransferase responsible for sialyl-Tn (sTn) synthesis, has been previously reported to be positively associated with cancer aggressiveness. Here we describe a novel sTn-dependent mechanism for chemotherapeutic resistance. We show that sTn protects cancer cells against chemotherapeutic-induced cell death by decreasing the interaction of cell surface glycan receptors with galectin-3 and increasing its intracellular accumulation. Moreover, exogenously added galectin-3 potentiated the chemotherapeutics-induced cytotoxicity in sTn non-expressing cells, while sTn overexpressing cells were protected. We also found that the expression of sTn was associated with a reduction in galectin-3-binding sites in human gastric samples tumors. ST6GalNAc-I knockdown restored galectin-3-binding sites on the cell surface and chemotherapeutics sensibility. Our results clearly demonstrate that an interruption of O-glycans extension caused by ST6GalNAc-I enzymatic activity leads to tumor cells resistance to chemotherapeutic drugs, highlighting the need for the development of novel strategies to target galectin-3 and/or ST6GalNAc-I.

Original publication




Journal article



Publication Date





83570 - 83587


chemotherapy resistance, galectin-3, gastric cancer, glycosylation, sialyl-Tn, Animals, Antigens, Tumor-Associated, Carbohydrate, Antineoplastic Agents, Cell Line, Tumor, Cell Proliferation, Cisplatin, Dose-Response Relationship, Drug, Drug Resistance, Neoplasm, Galectin 3, Glycosylation, Humans, Mice, Inbred BALB C, Mice, Nude, Protein Processing, Post-Translational, Protein Transport, RNA Interference, Sialyltransferases, Stomach Neoplasms, Time Factors, Transfection, Tumor Burden