Due to the decreased ABCB1 transporter expression, cdk6-deficient KB-C2 cells achieved remarkable reversal of MDR, showing significant increase in sensitivity to ABCB1 substrates colchicine (Fig. 2D) and paclitaxel (Fig. 2E), demonstrating that CDK6 regulates cancer MDR mediated by ABCB1 specifically. Here, ABCB1 is linked to cancer.