Drug efflux transporters and vincristine
Abstract
The increased expression of drug transporters following cancer chemotherapy contributes to resistance. This may reflect transcriptional up-regulation and/or clonal selection. We assessed vincristine (VCR) transport in Caco2 cells utilizing an in vitro transwell system. Transporters evaluated included mdr1 (ABCB1), mrp1 (ABCC1), mrp2 (ABCC2) and mrp3 (ABCC3). VCR transport was quantified in the absence and presence of LY335979, a specific mdr1 inhibitor. Cytotoxicity tests were performed to further elucidate the role of drug transporters on VCR efficacy. Transporter mRNA expression was determined in three cell lines prior to and following VCR exposure and quantitated using real time RT-PCR. All values were normalized to GADPH. ^ VCR was actively transported in our transwell system. LY335979 partially inhibited VCR transport in Caco2 cells. Cytotoxicity was increased significantly in LS174T and Caco2 cells (both express MDR1) after LY335979 co-incubation, but not in A549 cells (minimal MDR1 expression). VCR (10 nM and 100 nM), a potential pregnane X receptor (PXR)/constitutive androstane receptor (CAR) ligand, caused significant 5-fold induction of mrp2 and 4-fold induction of mrp3 expression in LS 174T cells at 48hrs. Similar induction effects on mrp2 and mrp3 genes were also seen with VCR (10 nM, 48hrs treatment) in A549 cells and with VCR (10 and 100 nM treatment) in Caco2 cells. ^ In conclusion, VCR is a substrate for MDR1, and cellular transport is partially reduced following treatment with LY335979. In MDR1 over-expressing cell lines, inhibition of MDR1 may be an efficient way to overcome VCR resistance. VCR up regulated drug transporters, however, this effect may vary with exposure time, cell line and drug concentration. VCR effects on transcriptional regulation do not appear to be mediated through the PXR. ^
Degree
Ph.D.
Advisors
Major Professors: D. J. Murry, Purdue University, Kevin Sowinski, Purdue University.
Subject Area
Health Sciences, Pharmacology|Health Sciences, Oncology
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