Since our results indicated that BCRP/ABCG2-mediated drug efflux reduced the anti-tumor activity of sorafenib in HCC cells (Figures 1 and 2), we next addressed whether combination with BCRP/ABCG2 inhibitors is a potential strategy to increase the sensitivity of HCC cells to sorafenib. The gene discussed is ABCG2; the disease is hepatocellular carcinoma.