engleski

Overexpression of alphaVbeta3 integrin protects human laryngeal carcinoma cell line from cisplatin-induced apoptosis

Drug resistance of tumor cells is the major obstacle for successful treatment of cancer patients. Different molecular mechanisms have been recognized as the cause of resistance: reduced drug accumulation, increased drug inactivation, increased ability to repair and/or tolerate DNA lesions, altered activity of nuclear enzymes and inhibition of apoptosis. Recently a novel mechanism of multidrug resistance has been identified that is based on integrin-mediated adhesion to extracellular matrix. As a model for determination of the role of alphavbeta3 integrin in drug resistance, we used alphavbeta3 integrin negative human laryngeal carcinoma cell line (HEp2), and three HEp2-derived cell clones with graded expression of alphavbeta3 integrin. We showed that alphavbeta3 integrin expression protects cells from cisplatin induced apoptosis. Using western blot analysis we determined increased expression of Bcl-2 protein in HEp-alphavbeta3 integrin expressing cells in comparison to HEp2 cells. In addition, we found increased level of glutathione (GSH) in HEp2-alphavbeta3 integrin expressing cells as compared to HEp2 cells. However, there was no significant difference in the extent of platination between HEp2 cells and HEp2-alphavbeta3 integrin expressing cells. Pre-treatment of HEp2-alphavbeta3 integrin expressing cells, with specific inhibitor of glutathione synthesis, buthionine sulfoximine (BSO), decreased level of GSH and abrogated integrin-mediated cisplatin-resistance to the level observed for HEp2 cells. However, the BSO treatment did not influence the expression of Bcl-2. To determine the involvement of Bcl-2 in resistance we established several clones from HEp2 with increased expression of Bcl-2. Increased expressions of Bcl-2 did not conferee cisplatin resistance nor induce increased level of GSH. Therefore, our results suggest that alphavbeta3 integrin mediated cisplatin resistance in HEp2 cells is dependent on increased GSH level, which contributes to cell survival by mechanisms independent of cisplatin inactivation or inhibition of DNA adduct formation. Since the up-regulation of alphavbeta3 integrin has been found in cisplatin-resistant cells, obtained by repeated cisplatin treatment of HEp2 cells, this phenomenon may be one of the mechanisms of resistance development.

integrin ; drug resistance

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