Adhesion of ST6Gal I-mediated human colon cancer cells to fibronectin contributes to cell survival by integrin beta1-mediated paxillin and AKT activation.

We have recently demonstrated that ionizing radiation (IR) of cells increased the expression of beta-galactoside alpha-(2,6)-sialyltransferase (ST6Gal I) and the level of glycoprotein sialylation, especially for the key adhesion molecule integrin beta1. In addition, ST6Gal I-mediated sialylation of integrin beta1 contributed to cell adhesion-mediated radioresistance in colon cancer cells. In this study, we examined IR-induced cell adhesion to the extracellular matrix and evaluated the role of integrin beta1-associated downstream signaling molecules, such as paxillin and AKT. IR exposure and ST6Gal I overexpression increased adhesion of SW480 colon cancer cells to fibronectin and contributed to cell survival through the activation of paxillin and AKT. In contrast, knockdown of ST6Gal I or paxillin reduced the level of radiation-induced cell adhesion and increased the level of cell death. These results suggest that integrin beta1 sialylation may play a critical role in promoting adhesion of cancer cells by integrin beta1-mediated paxillin and AKT activation.