Study On The Reversal Of Multidrug Resistance Effect And Molecular Mechanism Of R-verapamil

Objective To investigate the reversal effect of R-verapamil, one opt isomerizes of Verapamil, on multidrug resistance in ADRianycin (ADR) -resistant MCF-7 and HL-60 cell lines. Methods MCF-7 and HL-60 cells were cultivated with ADR of increasing concentration to obtain their ADR-resistant variants, MCF-7/ADR and HL-60/ADR. Chiral selective agent S-(+)-BNP was synthesized to split verapamil and obtain R-verapamil. The ability of R-verapamil to potentiate ADR cytotoxicity in vitro was evaluated in MCF-7 and HL-60 cells, and ADR resistant cells by MTT method. And the reversal activity in vivo was evaluated by tumor-bearing nude mice. The safty of the drug was evaluated by acute toxicity test on mice. ADR accumulation in vitro was determined with flow cytometery, and the drug resistance gene was determined with RT-PCR. Result Two MDR cell strains MCF-7/ADR and HL-60/ADR were cultivated and were 23.5 times and 7.34 times more resistant to ADR in comparison with sensitive cell strains. We syntheize chiral selective agent S-(+)-BNP to spilt Verapamil for preparation of R-verapamil, and define the structure and fineness with optical totation, NMR, elemental analysis. According to the MTT assay, R-verapamil potentiate ADR cytotoxicity in vitro at the concentration as low as 0.5-5ug/ml in MCF-7/ADR cells and 2-12ug/ml in HL-60/ADR cells. In comparison with the control, coadministration of ADR with low dose of R-verapamil could relieve weight loss and inhibit tumorous growth in tumor-bearing nude mice. Intragastric administration of R-verapamil to KUNMING mice had higher LD₅₀ (857.36mg·kg^-1) than that of Verapamil (134.38mg·kg^-1). Flow cytometery results proved that 0-2.5ug/ml or 0-4ug/ml R-verapamil could obviously increase ADR accumulation, meanwhile RT-PCR proved that R-verapamil could inhibit expression of MDR1 and GST and upregulate TOPO II expression. Conclusion It is worthwhile to explore the therapeutic potential of R-verapamil as a novel multidrug resistance reversal reagentin the therapy of malignant tumor.