Reversal by a Dihydropyridine Derivative of Non-P-Glycoprotein-Mediated Multidrug Resistance in Etoposide-Resistant Human Prostatic Cancer Cell Line

Abstract

Purpose We have isolated etoposide-resistant prostatic cancer cell lines, P/VP10 and P/VP20, to investigate the multidrug resistance (MDR) mechanism and to find MDR reversal agents. Materials and Methods We examined expression of MDR-related genes and screened reversal agents of MDR in P/VP20 cells. Results These cells demonstrated a non-P-glycoprotein (P-gp)-mediated MDR phenotype with overexpression of MDR-associated protein (MRP) mRNA due to MRP DNA amplification. A 1,4-dihydropyridine derivative, bis(4-pyridylmethyl)4-[2-(3-methyl-5,6- dihydro-1,4-dithiinyl)]-2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylate (NIK250), was found to overcome MDR in P/VP20 cells. Conclusions NIK250 might be useful in reversing MDR, which often develops during chemotherapy of advanced or hormone-resistant prostatic cancer.