Involvement of the concentrative nucleoside transporter 3 and equilibrative nucleoside transporter 2 in the resistance of T-lymphoblastic cell lines to thiopurines.
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.
Fotoohi
Alan Kambiz
AK
Department of Oncology and Pathology, Cancer Center Karolinska, Karolinska Institute, Stockholm, Sweden.
Lindqvist
Malin
M
Peterson
Curt
C
Albertioni
Freidoun
F
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*
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