title: Gene-expression profiling reveals down-regulation of equilibrative nucleoside transporter 1 (ENT1) in Ara-C-resistant CCRF-CEM-derived cells.
abstract: We have investigated the mechanism of resistance of leukemia cells to Ara-C using an in-house cDNA microarray designed for the analysis of leukemia cells. We produced Ara-C-resistant cells from the CCRF-CEM (acute lymphoblastic leukemia) cell line and compared their gene-expression profile with that of wild-type cells. The adenosine deaminase (ADA) gene was highly up-regulated in Ara-C-resistant cells, while equilibrative nucleoside transporter 1 (ENT1) and several cell-cycle-related genes were down-regulated. Of all these genes, ENT1 seemed the most likely to be relevant to Ara-C resistance. To investigate the role of ENT1 in Ara-C-resistant cells, we transfected the cells with the gene. ENT1-transfected Ara-C-resistant cells resembled wild-type CCRF-CEM cells more closely than untransfected Ara-C-resistant cells in terms of growth rate, Ara-C-uptake characteristics, and ADA expression levels. The down-regulation of the ENT1 gene is expected to result in nucleotide deficiency in addition to blockage of Ara-C influx. Accordingly, Ara-C-resistant cells showed low growth rates, which were restored by transfection with ENT1. These low growth rates were also correlated with the phosphorylation level of cell-cycle checkpoint kinase 2. In this study we identified down-regulation of ENT1 as the factor responsible for Ara-C resistance, and this knowledge may be used to devise a clinical regimen that will overcome the resistance.
authors.affiliation: Discovery Research Laboratories, Nippon Shinyaku Co., Ltd, 3-14-1 Sakura, Tsukuba, Ibaraki 305-0003, Japan. k.takagaki@nippon-shinyaku.co.jp
authors.forename: Kazuchika
authors.initials: K
authors.lastname: Takagaki
authors.forename: Susumu
authors.initials: S
authors.lastname: Katsuma
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Kaminishi
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Horio
authors.forename: Shinichiro
authors.initials: S
authors.lastname: Nakagawa
authors.forename: Teruo
authors.initials: T
authors.lastname: Tanaka
authors.forename: Tadaaki
authors.initials: T
authors.lastname: Ohgi
authors.forename: Junichi
authors.initials: J
authors.lastname: Yano
mesh_terms: D000243:Adenosine Deaminase / Q000235:genetics / Q000378:metabolism; D053148:Caspase 3; D020169:Caspases / Q000187:drug effects / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000378:metabolism; D002454:Cell Differentiation / Q000187:drug effects; D045744:Cell Line, Tumor; D002469:Cell Separation / Q000379:methods; D003561:Cytarabine / Q000494:pharmacology*; D015536:Down-Regulation; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D033721:Equilibrative Nucleoside Transporter 1 / Q000235:genetics* / Q000378:metabolism*; D020869:Gene Expression Profiling; D006801:Humans; D007938:Leukemia / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D013997:Time Factors
chemical_list: D018797:Cell Cycle Proteins; D033721:Equilibrative Nucleoside Transporter 1; D003561:Cytarabine; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases; D000243:Adenosine Deaminase