Comparison of Darinaparsin and Arsenic Trioxide effect on HI-LAPC-4, human prostatic cancer cell line

Darinaparsin (DPS) is an arsenic cytotoxin with a more favorable toxicity profile than the established anti-leukemic drug, arsenic trioxide (ATO). Here we report effects of DPS on a variety of solid tumor cell lines under normoxia as well as hypoxia, the latter an important characteristic of the tumor microenvironment. Using MTT and clonogenic assays, we demonstrated that DPS had potent cytotoxic activities under both normoxia and hypoxia, with IC50??s ~ 2- to 3-fold lower than ATO. Xenograft studies using tumor cell lines as well as patient-derived tumor tissues implanted under the renal capsule in mice confirmed the anti-tumor activity of DPS in vivo. DPS was also a more potent radiosensitizer under hypoxia than ATO in vitro, and sensitized solid tumors to radiation in vivo at doses that had no systemic toxicities. Interestingly, in contrast to previous reports of DPS effects on leukemic cells under normoxia, DPS-induced killing of hypoxic solid tumor cells was not dependent on ROS generation and oxidative damage. Instead, cDNA microarray analysis suggested that DPS inhibited oncogene- (such as RAS and MYC) associated gene expression. In fact, compared to normal mouse embryonic fibroblasts (MEFs), oncogene (RAS/E1A) transformed MEFs were markedly more sensitive to DPS-induced apoptosis under both normoxia and hypoxia. Altogether, these results demonstrate that DPS has significant and preferential cytotoxicity against solid tumor as compared with normal cells, and is an effective radiosensitizer. Since DPS is in early clinical development as a single agent, these findings have near term translational potential. time_series_design