Formulation Comprising Arsenic Trioxide and Dimercaprol Enhances Radiosensitivity of Pancreatic Cancer Xenografts

OBJECTIVE: To investigate the efficacy of a formula comprising arsenic trioxide and dimercaprol (BAL-ATO) as a radiosensitizing agent in model mice with pancreatic cancer xenografts. METHODS: Female BALB/c nude mice bearing SW1990 human pancreatic cancer xenografts were divided into four treatment arms, including control, radiotherapy (RT), BAL-ATO, and RT + BAL-ATO groups. Survival and tumor volume were analyzed. We also assessed apoptosis in tumor samples by live imaging and detected hypoxia by confocal laser microscope observation. We further investigated the mechanisms of BAL-ATO action in RT by detecting affected proteins by western blot and immunohistochemistry assays. RESULTS: Median survival was significantly longer in the RT + BAL-ATO group (64.5 days) compared with the control (49.5 days), RT (39 days), and BAL-ATO (48 days) groups (P < 0.001). RT + BAL-ATO inhibited the growth of tumors in mice by 73% compared with the control group, which was significantly higher than the rate of inhibition following RT alone (59%) (P < 0.01). Further analysis showed an improved microenvironment in terms of hypoxia in tumors treated with BAL-ATO alone or RT + BAL-ATO. Expression of signaling molecules associated with pancreatic cancer stem cells, including CD24, CD44, ALDH1A1, Gli-1, and Nestin, was detected in tumors treated with BAL-ATO alone or in combination with RT. CONCLUSION: These data suggest that BAL-ATO function as a radiosensitizer in mice with pancreatic cancer xenografts, via mechanisms involving hypoxia reduction and inhibition of signaling pathways associated with pancreatic cancer stem cells. BAL-ATO may thus be a promising radiosensitizing agent in patients with pancreatic cancer.