CD133+ cells in hepatocellular carcinoma (HCC) exhibit cancer stem cell (CSC)-like properties as well as resistance to chemotherapeutic agents and ionizing radiation; however, their function remains unknown. In this study, we tried to define new target and compound for enhancement of chemotherapy efficiency in HCC through elucidation of mechanism of CD133-induced chemoresistance.
Here, we show that CD133+ HCC cells exhibit strong resistance to reactive oxygen species (ROS) via persistent maintenance of the ROS-induced increase in xCT expression that upregulates glutathione (GSH) levels, and thereby play a central role in resistance to liver cancer therapy.
ROS are generally known to act as mediators of apoptosis induced by various anti-cancer drugs. We found that increased CD133 expression enhanced the capacity for ROS defense by enhancing cellular GSH levels, and ablation of CD133 attenuated not only the capacity for defense against ROS, but also chemoresistance, in HCC. Sulfasalazine, a potent xCT inhibitor, impaired the ROS defense system and increased the therapeutic efficacy of anticancer therapies in CD133+ HCC but not CD133−HCC in vivo and in vitro. Furthermore, we found that CD133 sustained the ROS stress-induced increase in the expression of xCT, a cystine/glutamate transporter that plays an important role in maintaining GSH levels, and thereby in preventing cell death via anticancer therapies. These results strongly indicate functional roles for CD133 in ROS defense and in evading anticancer therapies in HCC, and suggest that sulfasalazine, administered in combination with conventional chemotherapy, might be an effective treatment for CD133-targeted liver cancer therapy.
Citation Format: Haengran Seo. CD133 attenuates ROS accumulation via a steady increase in the expression of the cystine/glutamate transporter xCT: Consequence on chemoresistance in hepatocellular carcinoma. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1719.