K-RAS transformation in prostate epithelial cell overcomes H 2O 2-induced apoptosis via upregulation of gamma-glutamyltransferase-2

Abstract

The anti-apoptotic oncogene K-RAS is hypothesized to increase the antioxidant status of cells, thereby protecting them from generation of reactive oxygen species (ROS). Therefore, we examined whether K-RAS overcomes hydrogen peroxide (H 2O 2)-mediated apoptosis in the human fetal prostate epithelial cell 267B1. In this study, we found that treatment of 267B1 cells with H 2O 2 resulted in significant reduction of cell growth, which was associated with cytochrome-c release and caspase-3 activation. However, mutated K-RAS transformation (268B1/K-RAS) rendered 267B1 cells reduction of the resistance to H 2O 2-induced apoptosis through suppression of ROS generation. In addition, we analyzed profiling of gene expression in K-RAS transformation and found that gamma-glutamyltransferase 2 (GGT2) most highly expressed. Transient knockdown of K-RAS resulted in a significant downregulation of GGT gene expression. We also revealed that expression of GGT2 gene is closely regulated by the ERK signal pathway in 267B1/K-RAS cells. In addition, the anti-apoptotic effect of mutated K-RAS was attenuated by treatment with GGT2 RNA interference through inhibition of ROS generation, suggesting that mutated K-RAS mediates resistance to H 2O 2-induced apoptosis through GGT2 activation. These results importantly provide mechanistic insights on the anti-apoptotic activity of mutated K-RAS.