The Role Of Bim In Paclitaxel-Induced Apoptosis Of Gastric Adenocarcinoma Cells

Background & Objective:Gastric cancer is the leading cause of cancer death in our countries,the people's health were threatened severely.This is largely due to its unresponsiveness to conventional chemotherapeutic and biological reagents, which has been attributed to development of resistance to apoptosis.Paclitaxel have a broad spectrum of activity against various human cancers,Paclitaxel induce stabilization of microtubule formation, blockade of G2/M cell cycle transition , leading to subsequent cell death.Recently, the BH3-only proapoptotic protein Bim was released to microtubules via binding to the light chain of the dynein motor complex and to be critical for paclitaxel mediated cell death, suggesting that Bim may be an important mediator of cell death induced by antimicrotubule agents in solid tumors. Based on prior research, we inhibiting of Bim gene expression in apoptosis of gastic adenocarcinoma cells via siRNA technology. To better understand the mechanism(s) BH3-only protein in paclitaxel-induced apoptosis of gastric adenocarcinoma cells and the role of Bim, its illuminated the biological basis for resistance of gastric adenocarcinoma to microtubule-targeting agents and explore the effective approaches for overcoming resistance of cancer cells to apoptosis.Our department's researches found that paclitaxel induced apoptosis of gastric adenocarcinoma cells is associated with up-regulation and displaced of the BH3-only protein Bim. Method: SGC-7901 and BGC-823 gastric adenocarcinoma cells were treated with paclitaxel at varying doses for different time periods. The levels of apoptosis were quantitated using PI staing in flowcytometry. The role of caspases in paclitaxel-induced apoptosis was studied by using the pancaspase inhibitor, Z-VAD-fmk and Western blot. Paclitaxel-induced mitochondrial membrane potential changes were measured by PI staining in flowcytometry. The role of BH3-only protein was examined by Western blot analsysis in paclitaxel-induced apoptosis of gastric adenocarcinoma. Inhibition of Bim expression in apoptosis of gastric adenocarcinoma cells via siRNA technology. The expression levels of Bim after siRNA Bim were measured by Western blot. The role of Bim in paclitaxel-induced apoptosis of gastric adenocarcinoma was measured by PI staing in flowcytometry. Results: Paclitaxel induced apoptosis of gastric adenocarcinoma cells in a dose- and time-dependent manner. SGC-7901 cells appeared to be sensitive, whereas BGC-823 cells were relatively resistant to paclitaxel-induced apoptosis. Induction of apoptosis was largely dependent on caspases in that the pan caspase inhibitor Z-VAD-fmk inhibited apoptosis in both cell lines. Caspase-3,-9 was activated in paclitaxel-induced apoptosis. Paclitaxel-induced mitochondrial membrane potential reduced was measured by JC-1 staining. Paclitaxel-induced apoptosis was largely dependent on mitochondrial apoptotic pathway .Paclitaxel-induced up-regulated the BH3-only protein Bim, but down-regulated anti-apoptosis proteins Bcl-2 and Bcl-xl. Inhibition of Bim expression in apoptosis of gastric adenocarcinoma cells successfully via siRNA technology. In addition, inhibiting of Bim protects gastric cancer cells from paclitaxel-induced apoptosis. Conclusion: Paclitaxel kills gastric adenocarcinoma cells by induction of apoptosis. which is largely dependent on mitochondrial-mediated apoptosis pathway. Inhibiting of Bim protects gastric cancer cells from paclitaxel-induced apoptosis.