Bcl-2 and Bcl-x_L are important for the induction of paclitaxel resistance in human hepatocellular carcinoma cells

In this study we have investigated the mechanism underlying resistance to the chemotherapeutic drug paclitaxel in tumors of hepatocellular carcinoma (HCC) patients. Treatment with paclitaxel led to potent inhibition of growth of Hep3B hepatoma cells, but did not affect the growth properties of SNU-368 and SNU-398 cell lines that were established from primary HCC tumors. The growth inhibitory effect induced by paclitaxel correlated with levels of intracellular p21 and resulted in cell cycle arrest at the G2/M phase. However, paclitaxel treatment did not alter intracellular p53 levels. Instead, SNU-398 cells express high levels of the anti-apoptotic Bcl-2 and Bcl-x_L proteins and the level of Bcl-x_L could be further induced upon paclitaxel treatment. In contrast, Hep3B cells express pro-apoptotic members of the Bcl family and fail to induce Bcl-x_L upon paclitaxel treatment. Therefore, these results strongly suggest that Bcl-2 and Bcl-x_L play an important role in mediating resistance to paclitaxel.