MDR1 C2005T polymorphism changes substrate specificity

Abstract

Purpose: The current study is to determine the alterations of efflux transport activity to Rh123 and sensitivity to anticancer agents mediated by a MDR1 C2005T polymorphism.

Methods: Expressions of mRNA and protein of MDR1 were measured by real-time PCR and immunoblotting, respectively, and localization of P-glycoprotein (P-gp) by confocal microscopy. Cell cytotoxicity and efflux transport activity were determined by MTT and Rh123 transepithelial permeability assay, respectively.

Results: MDR1 C2005T polymorphism did not affect the expression level of the MDR1 mRNA and protein and had no effect on the trafficking of P-gp to plasma membrane. A cytotoxicity study showed that MDR1wt and MDR1 (2005T) cells exhibited similar resistance, as measured by IC(50) values, to vinblastine (30.3 +/- 2.5 vs. 32.5 +/- 1.7 nM) and vincristine (104.1 +/- 1.9 vs. 110.3 +/- 3.5 nM). However, MDR1 (2005T) cells were less resistant to paclitaxel (28.2 +/- 2.1 vs. 91.8 +/- 3.5 nM; P < 0.05) and etoposide (119.7 +/- 6.5 vs. 546.8 +/- 9.5 nM; P < 0.05). The apparent transepithelial permeability ratios of Rh123 in MDR1 (wt) and MDR1 (2005T) cells were 2.12 +/- 0.46 and 3.64 +/- 0.78 (P < 0.05), respectively.

Conclusions: The MDR1 C2005T polymorphism alters the transepithelial permeability of a fluorescent substrate and sensitivity to select cytotoxic agents, which may influence drug disposition and the therapeutic efficacy of some P-gp substrates.