ABCB1 and hepatocellular carcinoma: MicroRNAs regulate drug resistance in HCC; for example, the downregulation of miR-122 upregulates ABCB1, ABCF2, and PKM2 and increases resistance against doxorubicin [60], whereas the downregulation of miR-340 activates Nrf2 and enhances resistance against cisplatin [61].