Moreover, ablation of CD133 attenuated not only the capacity for defense against ROS, but also chemoresistance, in HCC through decreasing glutathione (GSH) levels in vitro. Sulfasalazine, a potent xCT inhibitor that plays an important role in maintaining GSH levels, impaired the ROS defense system and increased the therapeutic efficacy of anticancer therapies in CD133-positive HCC but not CD133-negative HCC in vivo and in vitro. The gene discussed is PROM1; the disease is hepatocellular carcinoma.