title: Functional ABCG2 is overexpressed on primary CML CD34+ cells and is inhibited by imatinib mesylate.
abstract: Imatinib mesylate (IM) therapy for chronic myeloid leukemia (CML) has transformed the treatment of this disease. However, the vast majority of patients, despite major responses, still harbor Philadelphia chromosome-positive (Ph(+)) cells. We have described a population of primitive Ph(+) cells that are insensitive to IM and may be a source of IM resistance. Cell line studies have suggested that the drug transporter ABCG2 may be a mediator of IM resistance, however there is considerable debate about whether IM is an ABCG2 substrate or inhibitor. We demonstrate here that primitive CML CD34(+) cells aberrantly overexpress functional ABCG2 but that cotreatment with IM and an ABCG2 inhibitor does not potentiate the effect of IM. We definitively show that IM is an inhibitor of, but not a substrate for, ABCG2 and that, therefore, ABCG2 does not modulate intracellular concentrations of IM in this clinically relevant cell population.
authors.affiliation: Division of Cancer Science & Molecular Pathology, University of Glasgow, UK.
authors.forename: Niove E
authors.initials: NE
authors.lastname: Jordanides
authors.forename: Heather G
authors.initials: HG
authors.lastname: Jorgensen
authors.forename: Tessa L
authors.initials: TL
authors.lastname: Holyoake
authors.forename: Joanne C
authors.initials: JC
authors.lastname: Mountford
mesh_terms: D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters / Q000096:biosynthesis*; D018952:Antigens, CD34; D001549:Benzamides; D045744:Cell Line, Tumor; D019008:Drug Resistance, Neoplasm / Q000187:drug effects; D005260:Female; D015973:Gene Expression Regulation, Leukemic / Q000187:drug effects; D006801:Humans; D000068877:Imatinib Mesylate; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive / Q000188:drug therapy / Q000378:metabolism*; D008297:Male; D009363:Neoplasm Proteins / Q000096:biosynthesis*; D010879:Piperazines / Q000494:pharmacology* / Q000627:therapeutic use; D047428:Protein Kinase Inhibitors / Q000494:pharmacology* / Q000627:therapeutic use; D011743:Pyrimidines / Q000494:pharmacology* / Q000627:therapeutic use
chemical_list: C116614:ABCG2 protein, human; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters; D018952:Antigens, CD34; D001549:Benzamides; D009363:Neoplasm Proteins; D010879:Piperazines; D047428:Protein Kinase Inhibitors; D011743:Pyrimidines; D000068877:Imatinib Mesylate