title: A novel human multidrug resistance gene MDR1 variant G571A (G191R) modulates cancer drug resistance and efflux transport.
abstract: The human multidrug resistance gene MDR1 encodes a membrane-bound transporter P-glycoprotein (Pgp) that confers the drug resistance of cancer cells by mediating an ATP-dependent drug efflux transport. We and others have reported a number of functionally significant MDR1 variants, including G1199A and G1199T, that modulate cancer drug resistance and intracellular levels of antivirals. In this report, we describe a novel G571A variant of MDR1 detected in 6.4% of leukemia patients. Because this nucleotide modification gives rise to an amino acid change from Gly to Arg at the 191 amino acid position of Pgp, we have developed and characterized the functional affect of the G571A variant in stable, recombinant cells. Using six chemotherapeutic drugs, doxorubicin HCl, daunorubicin HCl, vinblastine sulfate, vincristine sulfate, taxanes (paclitaxel), and epipodophyllotoxin (etoposide, VP-16), we found that the MDR1(571A) variant selectively reduced the degree of Pgp-mediated resistance in drug-dependent manner. Although there was a minimal effect on doxorubicin and daunorubicin, the MDR1-dependent resistance on vinblastine, vincristine, paclitaxel, and etoposide was reduced by approximately 5-fold. The increased drug sensitivity in MDR1(571A), compared with MDR1(wt), paralleled the intracellular drug levels. These data suggest that individuals with this novel MDR1 variant, the 571A genotype, may be more sensitive to the specific anticancer drugs that are Pgp substrates.
authors: Department of Pharmaceutics, University of Washington, Seattle, WA 98195-7610, USA.
authors: Ziping
authors: Z
authors: Yang
authors: Daniel
authors: D
authors: Wu
authors: Tot
authors: T
authors: Bui
authors: Rodney J Y
authors: RJ
authors: Ho
mesh_terms: D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000502:physiology; D000166:Acridines / Q000494:pharmacology; D000368:Aged; D000369:Aged, 80 and over; D001692:Biological Transport; D002478:Cells, Cultured; D004317:Doxorubicin / Q000378:metabolism; D019008:Drug Resistance, Neoplasm; D005838:Genotype; D006239:Haplotypes; D006801:Humans; D007938:Leukemia / Q000188:drug therapy / Q000235:genetics*; D008875:Middle Aged; D017239:Paclitaxel / Q000378:metabolism; D020641:Polymorphism, Single Nucleotide; D044005:Tetrahydroisoquinolines / Q000494:pharmacology; D014747:Vinblastine / Q000378:metabolism
chemical_list: C513055:ABCB1 protein, human; D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000166:Acridines; D044005:Tetrahydroisoquinolines; D014747:Vinblastine; D004317:Doxorubicin; C083501:Elacridar; D017239:Paclitaxel