title: Involvement of the concentrative nucleoside transporter 3 and equilibrative nucleoside transporter 2 in the resistance of T-lymphoblastic cell lines to thiopurines.
abstract: Mechanisms of resistance to thiopurines, 6-mercaptopurine (6-MP) and 6-thioguanine (6-TG) were investigated in human leukemia cell lines. We developed two 6-MP- and 6-TG-resistant cell lines from the human T-lymphoblastic cell line (MOLT-4) by prolonged exposure to these drugs. The resistant cells were highly cross resistant to 6-MP and 6-TG, and exhibited marked reduction in cellular uptake of 6-MP (70% and 80%, respectively). No significant modification of the activities of hypoxanthine-guanine phosphoribosyl transferase, thiopurine methyltransferase or inosine monophosphate dehydrogenase was observed. Real-time PCR of concentrative nucleoside transporter 3 (CNT3) and equilibrative nucleoside transporter 2 (ENT2) of resistant cells showed substantial reductions in expression of messenger RNAs. Small interfering RNA designed to silence the CNT3 and ENT2 genes down-regulated the expression of these genes in leukemia cells. These decreases were accompanied by reduction of transport of 6-MP (47% and 21%, respectively) as well as its cytocidal effect (30% and 21%, respectively). Taken together these results show that CNT3 and ENT2 play a key role in the transport of 6-MP and 6-TG by leukemia cells. From a clinical point of view determination of CNT3 and ENT2 levels in leukemia cells may be useful in predicting the efficacy of thiopurine treatment.
authors.affiliation: Department of Oncology and Pathology, Cancer Center Karolinska, Karolinska Institute, Stockholm, Sweden.
authors.forename: Alan Kambiz
authors.initials: AK
authors.lastname: Fotoohi
authors.forename: Malin
authors.initials: M
authors.lastname: Lindqvist
authors.forename: Curt
authors.initials: C
authors.lastname: Peterson
authors.forename: Freidoun
authors.initials: F
authors.lastname: Albertioni
mesh_terms: D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology*; D001692:Biological Transport; D045744:Cell Line, Tumor; D019008:Drug Resistance, Neoplasm; D033721:Equilibrative Nucleoside Transporter 1 / Q000235:genetics; D033722:Equilibrative-Nucleoside Transporter 2 / Q000235:genetics* / Q000378:metabolism; D020868:Gene Silencing; D006801:Humans; D007041:Hypoxanthine Phosphoribosyltransferase / Q000378:metabolism; D007168:IMP Dehydrogenase / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000235:genetics* / Q000378:metabolism; D015122:Mercaptopurine / Q000378:metabolism / Q000494:pharmacology*; D008780:Methyltransferases / Q000378:metabolism; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma / Q000235:genetics* / Q000378:metabolism; D013601:T-Lymphocytes / Q000187:drug effects / Q000378:metabolism; D013866:Thioguanine / Q000378:metabolism / Q000494:pharmacology*
chemical_list: D000964:Antimetabolites, Antineoplastic; D033721:Equilibrative Nucleoside Transporter 1; D033722:Equilibrative-Nucleoside Transporter 2; D026901:Membrane Transport Proteins; C438649:SLC29A1 protein, human; C438654:SLC29A2 protein, human; C065171:cif nucleoside transporter; D015122:Mercaptopurine; D007168:IMP Dehydrogenase; D008780:Methyltransferases; C022745:thiopurine methyltransferase; D007041:Hypoxanthine Phosphoribosyltransferase; D013866:Thioguanine