Cytotoxicity, metabolism, and mechanisms of action of 2',2'-difluorodeoxyguanosine in Chinese hamster ovary cells.

作者：Varsha Gandhi, Shin Mineishi, Ping Huang, A J Chapman, Yang Yu, F. Chen, Billie Nowak, Sherri Chubb, Larry W. Hertel, William Plunkett · 发表于：PubMed · 年份：1995 · 被引用次数：41 · 研究领域：Biochemical and Molecular Research、Chronic Lymphocytic Leukemia Research、Immunodeficiency and Autoimmune Disorders

The emerging clinical success of gemcitabine (2',2'-difluorodeoxycytidine) stimulated interest in the synthesis and evaluation of purine congeners. The cytotoxicity, metabolism, and mechanisms of action of the lead candidate, 2',2'-difluorodeoxyguanosine (dFdGuo), were studied in Chinese hamster ovary cells. Unlike the natural nucleoside deoxyguanosine (dGuo), dFdGuo was not a substrate for purine nucleoside phosphorylase. Wild-type Chinese hamster ovary cells and a mutant line deficient in deoxycytidine (dCyd) kinase were similarly affected by dFdGuo (50% inhibitory concentration, 7.5 and 6.5 microM, respectively), suggesting that unlike gemcitabine, dCyd kinase was not responsible for activation of dFdGuo. This was further confirmed by separation of nucleoside kinases (adenosine kinase, dGuo kinase, and dCyd kinase) of Chinese hamster ovary cells on DEAE-cellulose column chromatography. The kinase activity that phosphorylated dGuo also converted dFdGuo to its monophosphate, suggesting that dGuo kinase activated dFdGuo. Consistent with this result, coincubation with dGuo spared the dFdGuo-mediated toxicity; however, addition of up to 10 mM dCyd did not reverse the toxicity of dFdGuo. Intracellularly, dFdGuo was phosphorylated to its mono-, di-, and triphosphates; dFdGuo triphosphate (dFdGTP) was the major metabolite and accumulated to 45 microM after a 6-h incubation with 30 microM dFdGuo. The elimination of dFdGTP was monophasic with a t1/2 of about 6 h. Deoxynucleotides we...