ROS-mediated genotoxic stress is involved in NaAsO2-induced cell cycle arrest, stemness enhancement and chemoresistance of prostate cancer cells in a p53-independent manner

Abstract

Several epidemiological studies reported that chronic arsenic exposure increased risk of prostate cancer. This study aimed to investigate whether chronic NaAsO2 exposure elevates stemness and chemoresistance in prostate cancer cells. DU145 (wild-type p53) and PC-3 (p53-null) cells were exposed to NaAsO2 (2 μmol/L) for 30 generations. IC50s to docetaxel and cisplatin were increased in NaAsO2-exposed DU145 and PC-3 cells. The number of tumor spheres was elevated in NaAsO2-exposed DU145 and PC-3 cells. Nanog, SOX-2 and ALDH1A1, three markers of cancer stemness, were upregulated in NaAsO2-exposed PC-3 spheres. Moreover, NaAsO2-exposed DU145 and PC-3 cells were arrested in G2/M phase. Histone H2AX phosphorylation on Ser139, an indicator for DNA double-strand break, was upregulated in NaAsO2-exposed DU145 and PC-3 cells. ATM phosphorylation on Ser1981, a key sensor of genotoxic stress, was rapidly elevated in NaAsO2-exposed DU145 cells. Phosphor-p53, a downstream molecule of ATM signaling, and p21, a direct target of p53, were upregulated in NaAsO2-exposed DU145 cells. Unexpectedly, p21 was also elevated in NaAsO2-exposed p53-null PC-3 cells. Antioxidant NAC alleviated NaAsO2-induced ATM phosphorylation, cell cycle arrest, and subsequent stemness enhancement and chemoresistance in both DU145 and PC-3 cells. These results suggest that ROS-mediated genotoxic stress is involved in NaAsO2-induced cell cycle arrest, stemness enhancement and chemoresistance of prostate cancer cells in a p53-independent manner.