ABSTRACT
Drug resistance is a major obstacle to successful cancer treatment. Therefore, it is essential to understand the molecular mechanisms underlying drug resistance to develop successful therapeutic strategies. α6ß4 integrin confers resistance to apoptosis and regulates the survival of cancer cells; however, it remains unclear whether α6ß4 integrin is directly involved in chemoresistance. Here, we show that α6ß4 integrin promotes doxorubicin resistance by decreasing caspase-3-mediated apoptosis. We found that the overexpression of α6ß4 integrin by the ß4 integrin gene rendered MDA-MB435S and Panc-1 cells more resistant to doxorubicin than control cells. The acquired resistance to doxorubicin by α6ß4 integrin expression was abolished by the deletion of the cytoplasmic signal domain in ß4 integrin. Similar results were found in MDA-MB435S and Panc-1 cells when N-glycan-defective ß4 integrin mutants were overexpressed or bisecting GlcNAc residues were increased on ß4 integrin by the co-expression of N-acetylglucosaminyltransferase III with ß4 integrin. The abrogation of α6ß4 integrin-mediated resistance to doxorubicin was accompanied by reduced cell viability and an increased caspase-3 activation. Taken together, our results clearly suggest that α6ß4 integrin signaling plays a key role in the doxorubicin resistance of cancer cells, and N-glycans on ß4 integrin are involved in the regulation of cancer cells.