PGP and cancer: Considering the pivotal role of ABCB1, one of the key drug efflux pumps23,24, in MDR and the potential use of miRNA in MDR cancer therapy, we predicted candidate miRNAs that potentially bind to the 3′-UTR of human ABCB1 (P-gp) using the bioinformatics algorithms TargetScan and MicroCosm Targets in a previous study and identified the miRNAs that negatively regulated ABCB1 in hepatocarcinoma.25 The results of this previous study showed that miR-338-5p significantly inhibited P-gp expression and was another potential P-gp inhibitor (Figure S1).