Overexpression of phospholipase D suppresses taxotere-induced cell death in SNU 484 cells

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. Microtubules are important cytoskeletal components involved in many cellular events. Antimicrotuble agent, taxotere (docetaxel) has been known as an inhibitor of microtubule depolymerization, resulting in 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; originated from autoimmune deficiency fetal) 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. When PLD cDNA was transfected into SNU 484 cells, overexpression of PLD isozymes (PLD 1 and 2) resulted in inhibition of taxotere-induced apoptotic cell death, evidenced by showing a decreased degradation of chromosomal DNA and cell viability of over 80%. In addition, bcl-2 expression was up-regulated and taxotere-induced activation of caspase-3 was inhibited after transfection of PLDs. Taken together, these results suggest that PLD plays protective role against taxotere-induced cell death in SNU 484 cells through up-regulation of bcl-2 expression.