Background:

LY335979 is a selective inhibitor of P-Gp with IC50 value of 1.2 nM [1, 2].

P-gp (P-glycoprotein) is a member of ATP-binding cassette (ABC) transporters and plays a pivotal role in pumping many foreign substances out of cells. It has been reported that abnormal expression of P-Gp is correlated with the multidrug resistance of tumor cells [3].

LY335979 is a potent P-Gp inhibitor and has a different selectivity with the reported P-Gp inhibitor cyclosporin A or verapamil. In drug-resistant cell line HL60/VCR with highly expression of P-Gp, LY335979 exhibited highly restore ability of P-Gp than cyclosporin A or verapamil and the IC 50 value of 1.2 nM [1]. When tested with a panel of cell lines over-expressed P-Gp (CEM/VLB100, MCF-7/ADR, 2780AD, P388/ADR, and UCLA-P3.003VLB), administration of LY335979 reversed the cells resistance to Vinblastine, Doxorubicin, Btoposide and Taxol by inhibiting P-Gp activity [2].

In female nude mice model with UCLA-P3.003VLB MDR tumor cells subcutaneous xenograft, pre-treated with LY335979 (30mg/kg) restored tumor cells sensitivity to Taxol (20 mg/kg) which combination markedly suppressed solid tumor growth compared with control group [2].

参考文献:
1.? Green, L.J., P. Marder, and C.A. Slapak, Modulation by LY335979 of P-glycoprotein function in multidrug-resistant cell lines and human natural killer cells. Biochem Pharmacol, 2001. 61(11): p. 1393-9.
2.? Dantzig, A.H., et al., Reversal of P-glycoprotein-mediated multidrug resistance by a potent cyclopropyldibenzosuberane modulator, LY335979. Cancer Res, 1996. 56(18): p. 4171-9.
3.?? Hu, T., et al., Reversal of P-glycoprotein (P-gp) mediated multidrug resistance in colon cancer cells by cryptotanshinone and dihydrotanshinone of Salvia miltiorrhiza. Phytomedicine, 2014. 21(11): p. 1264-72.