PGP and hepatocellular carcinoma: We also found that expression of stemness markers, such as NANOG, SOX2, OCT4, and KLF4, and drug-resistance markers, such as P-GP, ABCG2, ABCC1, ALDH1A1, and ABCB5, was decreased upon GPR50 knockdown (Figures 2E and 2G; Figure S1), suggesting that GPR50 has oncogenic ability and regulates HCC progression.