Increased susceptibility of H-Ras(G12V)-transformed human urothelial cells to the genotoxic effects of sodium arsenite.

Inorganic arsenite (iAs) is a human carcinogen. Numerous studies have shown that mutation-activated H-Ras is frequently observed in human urothelial carcinomas. The interaction between iAs, an environmental factor, and H-Ras, an oncogene, is not clear. In this study, we explored the genotoxic effects of iAs in human urothelial cells ectopically expressing H-Ras (G12V) an activated H-Ras oncogene. Our results showed that H-Ras(G12V)-transformed human urothelial cells (HUC-RAS) were more susceptible to arsenite-induced cell death, DNA damage, micronuclei formation and anchorage-independent growth than control cells (HUC-neo). Furthermore, iAs treatment induced higher intracellular levels of reactive oxygen species (ROS) in the HUC-RAS cells than in the HUC-neo cells. N-acetyl-L-cysteine could suppress the iAs-induced increases in ROS and genetic damage. We further demonstrated that the intracellular glutathione levels were significantly elevated by the iAs treatment of the HUC-neo cells, but that this effect was not observed in the HUC-RAS cells. The iAs treatment induced higher superoxide dismutase activity in the HUC-neo cells than in the HUC-RAS cells. Alternatively, catalase activity was higher in the HUC-RAS cells than in the HUC-neo cells, but this enzyme was significantly suppressed by iAs. Moreover, iAs activated the ERK and JNK signaling pathways, which are involved in iAs-induced ROS production and genetic damage. Taken together, our present results suggest that elevated catalase activity in H-Ras(G12V)-transformed cells is significantly suppressed by iAs via activation of ERK and JNK signaling pathways and hence attenuate the defense of the neoplastic transformed cells against iAs-induced oxidative injuries.