Chinese herbal medicines as reversal agents for P-glycoprotein-mediated multidrug resistance in tumors

Multidrug resistance (MDR) is the major reason for failure of human cancer chemotherapy. One of the main underlying mechanisms of MDR is the over-expression of P-glycoprotein (P-gp), an ATP-dependent membrane transporter protein encoded by MDR1 gene. P-gp extrudes a spectrum of anticancer drugs from cancer cells and decreases effective intracellular drug concentrations, therefore leads to drug tolerance of cancer cells. P-gp modulators restore chemosensitivity of cancer cells through inhibiting transport function or cellular expression of P-gp. Chinese medicines have been used for treatment of cancer for thousand years. This review provides a brief introduction of Chinese medicines that exhibited activity in reversing P-gp-mediated MDR in cancers.