MRP1 not MDR1 gene expression is the predominant mechanism of acquired multidrug resistance in two prostate carcinoma cell lines

Abstract

Multidrug resistant prostate cancer cell lines DU 0.03 and PC 0.03 were established from the parental prostate cancer cell lines DU145 and PC-3 respectively by stepwise selection in doxorubicin (DOX) from 0.001 to 0.03 m mg/ml. As cells adapted to each concentration of DOX. the drug concentration was increased by 0.001 m mg/ml. The chemosensitivity of each line was determined by growth inhibition assay. The DU 0.03 and PC 0.03 lines exhibit a 5 ± 10-fold and 1.3 ± 2.8-fold increase in resistance to anthracyclines, vinblastine (VLB) and mitozantrone (Mito), respectively. Verapamil (5 m mM) partially reversed the resistance to the anthracycline and completely reversed the resistance to VLB and Mito. Drug kinetic studies measured by intracellular accumulation of 3 H-daunorubicin demonstrated a 3 fold decrease in the level of intracellular 3 H-daunorubicin in the PC 0.03 and DU 0.03 resistant lines compared with their respective parental line. This effect was partially reversed by 5 m mM verapamil. The expression of MDR1 and MRP genes was analysed by Northern blotting and RT-PCR. P-glycoprotein (Pgp) and MRP protein were tested by immunocytochemistry staining using the monoclonal antibodies J-SB1. C219 and MRK16 (Pgp) and MRPm6 and MRPr1 (MRP). Neither Northern blot analysis nor the more sensitive RT-PCR demonstrated detectable MDR1 transcripts in any of the prostate cancer cell lines and the three Pgp monoclonal antibodies failed to reveal expression of Pgp.A 2 ± 4-fold increase in MRP1 mRNA levels in the drug resistant DU 0.03 and PC 0.03 lines were demonstrated by both Northern blotting and RT-PCR consistent with the ®ndings observed after staining by the two speci®c monoclonal antibodies, MRPm6 and MRPr1. Southern blot analysis demonstrated a 2-fold increase in the MRP1 gene copy number in the PC 0.03 line but not in the DU 0.03 line, suggesting that the overexpression of the MRP gene was regulated at the level of transcription in the latter line. We conclude that MRP1 not MDR1 overexpression. contributes to acquired drug resistance in these two prostate cancer cell lines. Prostate Cancer and Prostatic Diseases (2000) 3, 66±75.

Drug Susceptibility Testing of Anaerobic Protozoa

“…The highly metronidazole-resistant laboratory line, F1623-M1, for which the MIC mode is Ͼ100 M metronidazole, was unable to grow aerobically, as documented for other resistant trichomonads (26 (35) and a twofold decrease in ferredoxin activity (23) in the metronidazole-resistant laboratory line WB-M3 may therefore be sufficient for clinical resistance. Similarly, a three-to fivefold increase in MRP activity renders tumor cells resistant to chemotherapy (46). The reason for using the mouse model for the assays (22) is the difficulty in establishing in vitro cultures of G. duodenalis, with the best success rates reporting around 50% of samples finally established in culture (38).…”

Phosphatidylinositol 3′-Kinase Activation Leads to Multidrug Resistance Protein-1 Expression and Subsequent Chemoresistance in Advanced Prostate Cancer Cells

“…Moreover, down-regulation of MRP-1 expression was able to render drug-resistant CaP cells susceptible to the chemotoxic activities of both doxorubicin and paclitaxel. Because MRP-1 is the primary drug pump found in advanced CaP (13), the findings presented herein should be instrumental in developing future strategies to down-regulate the expression and/or activity of this efflux pump, as well as increasing the effectiveness of antineoplastic compounds.…”

The 44-kDa Pim-1 Kinase Phosphorylates BCRP/ABCG2 and Thereby Promotes Its Multimerization and Drug-resistant Activity in Human Prostate Cancer Cells

“…Several biochemical mechanisms of drug resistance have been identified in prostate cancer cell lines, including alterations of glutathione metabolism, altered topoisomerase activity, and up-regulation of the transmembrane drug efflux pumps (14), and in particular ATP binding cassette (ABC) 3 transporter family members such as multidrug resistance protein-1(MDR1/Pgp/ABCB1) and multidrug resistance-associated protein-1(MRP1/ABCC1). Recently it has been reported that MRP1 but not MDR1 overexpression contributes to acquired drug resistance in two prostate cancer cell lines derived from PC3 and DU145 (14).…”

“…Several biochemical mechanisms of drug resistance have been identified in prostate cancer cell lines, including alterations of glutathione metabolism, altered topoisomerase activity, and up-regulation of the transmembrane drug efflux pumps (14), and in particular ATP binding cassette (ABC) 3 transporter family members such as multidrug resistance protein-1(MDR1/Pgp/ABCB1) and multidrug resistance-associated protein-1(MRP1/ABCC1). Recently it has been reported that MRP1 but not MDR1 overexpression contributes to acquired drug resistance in two prostate cancer cell lines derived from PC3 and DU145 (14). It has been shown that the presence of a half ABC transporter, breast cancer resistance protein BCRP/ABCG2, isolates the putative prostate stem cells from the prostate tissue microenvironment through constitutive efflux of androgen and protects the putative tumor stem cells from androgen deprivation, hypoxia, or adjuvant chemotherapy, and provides the nidus for recurrent prostate cancer (15).…”