Effect of phospholipase D1 activity on apoptosis induced by taxotere in stomach cancer cell lines (SNU 484)

Abstract

Phospholipase D (PLD) plays an important role as an effector in a variety of physiological processes that reveal it to be a member of the signal transducing phospholipases. Recently, PLD has been known to play a protective role against apoptosis, acting as survival factor, suggesting that PLD activation may attribute to gain anticancer drug resistance in cancer cells. Microtubles are important cytoskeletal components involved in many cellular events. Antimicrotuble agent, taxotere (docetaxel) has been known to induce apoptosis in cancer cells. In this study, we examined the role of PLD activity in taxotere-induced apoptosis in stomach cell lines; normal stomach cells (NSC) and poorly differentiated stomach cancer cells (SNU 484). Treatment of stomach cells with taxotere resulted in induction of apoptosis in these cells, which is accompanied by the activation of PLD. Taxotere induced apoptosis in SNU 484 cells was more prominent than NSC. After 48 hours treatment with 10 μM taxotere, cell viability decreased to below 40% in SNU 484 cells whereas more than 70% of NSC was remained viable. This taxotere-induced apoptosis was enhanced when PLD was selectively inhibited by pretreating the cells with 1-butanol. Basal expression level of PLD1, but not of PLD2, in NSC was about 2 times higher than that of SNU 484 cells. When PLD1 cDNA was transfected into SNU 484 cells, overexpression of PLD1 resulted in inhibition of taxotere-induced apoptotic cell death. In addition, bcl-2 expression was up-regulated and inhibited taxotere-induced cleavage and activation of caspase-3. Taken together, these results suggest that PLD1 plays protective role against taxotere-induced cell death in SNU 484 cells.