PGP and cancer: 39, 40 Additionally, many miRNAs were determined that could upregulate MDR1/ABCB1 gene expression leading to chemoresistance in cancer, such as miR‐21 and miR‐27a. 37 Therefore, miRNAs could become our research focus when we try to explore the mechanisms for overexpression of TET1 inducing a reduction of P‐gp expression.