PGP and cancer: There are mainly four molecular mechanisms of drug resistance to cancer treatment17, 18: (a) glutathione that could efflux drugs out of tumor cells; (b) p53 mutation suppresses apoptosis; (c) multiple drug resistance proteins, consist of MRP1, LRP, P‐gp, generally over‐expressed in drug resistance cells and these proteins restrain drug from entering the cell interior; and (d) tumor microenvironment alters.