Despite the complexity of MDR, over-expression of P-glycoprotein (P-gp) has been recognized as a major mechanism, which causes a reduction in the accumulation of drugs in cancer cells by increasing ‘active efflux’ and decreasing influx, thereby preventing tumor cells from being killed by drugs (Persidis, 1999; Gottesman et al., 2002; Joshi et al., 2017). This evidence concerns the gene PGP and cancer.