Cellular elimination of 2',2'-difluorodeoxycytidine 5'-triphosphate: a mechanism of self-potentiation.
Cellular elimination of 2',2'-difluorodeoxycytidine 5'-triphosphate: a mechanism of self-potentiation.
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发表时间：
1992-02
期刊：
影响因子：
11.2
通讯作者：
Volker Heinemann;YÂ ¡-ZhengXu;S. Chubb;Alina Sen;L. Hertel;G. B. Grindey;W. Plunkett
中科院分区：
文献类型：
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作者：
Volker Heinemann;YÂ ¡-ZhengXu;S. Chubb;Alina Sen;L. Hertel;G. B. Grindey;W. Plunkett
2',2'-二氟脱氧胞苷 (dFdC, Gemcitabine) 是一种脱氧胞苷类似物，磷酸化为 5'-二磷酸和 5'-三磷酸 (dFdCTP) 后，可诱导 DNA 合成抑制和细胞死亡。我们检查了细胞 dFdCTP 的消除动力学值，发现它们依赖于将 CCRF-CEM 细胞与 dFdC 一起孵育并冲洗到无药物培养基中后的细胞浓度。当药物在低细胞 dFdCTP 水平（低于 50 µM）下被洗出时，dFdCTP 消除呈线性（t1/2 = 3.3 h），但在细胞内 dFdCTP 水平高于 100 µM 时变为双相。尽管所有浓度下的初始消除率相似，但在较高浓度下，最终消除率随着细胞 dFdCTP 浓度的增加而增加，在 300 microM 时几乎完全抑制 dFdCTP 消除。在低细胞 dFdCTP 浓度下，脱氨产物 2',2'-二氟脱氧尿苷是主要的细胞外分解代谢物，而在高 dFdCTP 浓度下，dFdC 是主要的排泄产物。 dCMP 脱氨酶抑制剂 3,4,5,6-四氢脱氧尿苷将低 dFdCTP 水平下的单相 dFdCTP 降解转化为双相过程，而脱氧胞苷脱氨酶抑制剂 3,4,5,6-四氢尿苷对 dFdCTP 消除没有影响。原位测定表明，全细胞中 dCMP 脱氨酶活性受到抑制，这种作用与 dCTP:dTTP 值降低相关。此外，dFdCTP 还能抑制部分纯化的 dCMP 脱氨酶，50% 抑制浓度为 0.46 mM。我们得出结论，dFdC 诱导的 dCMP 脱氨酶抑制导致 dFdCTP 分解代谢减少，从而导致浓度依赖性消除动力学。该作用构成了 dFdC 活性的自我增强。
2',2'-Difluorodeoxycytidine (dFdC, Gemcitabine) is a deoxycytidine analogue which, after phosphorylation to the 5'-di- and 5'-triphosphate (dFdCTP), induces inhibition of DNA synthesis and cell death. We examined the values for elimination kinetics of cellular dFdCTP and found they were dependent on cellular concentration after incubation of CCRF-CEM cells with dFdC and washing into drug-free medium. When the drug was washed out at low cellular dFdCTP levels (less than 50 microM), dFdCTP elimination was linear (t1/2 = 3.3 h), but it became biphasic at intracellular dFdCTP levels greater than 100 microM. Although the initial elimination rate was similar at all concentrations, at higher concentrations the terminal elimination rate increased with increasing cellular dFdCTP concentration, with a nearly complete inhibition of dFdCTP elimination at 300 microM. The deamination product 2',2'-difluorodeoxyuridine was the predominant extracellular catabolite at low cellular dFdCTP concentrations, whereas at high dFdCTP concentrations dFdC was the major excretion product. The dCMP deaminase inhibitor 3,4,5,6-tetrahydrodeoxyuridine transformed the monophasic dFdCTP degradation seen at low dFdCTP levels into a biphasic process, whereas the deoxycytidine deaminase inhibitor 3,4,5,6-tetrahydrouridine had no effect on dFdCTP elimination. An in situ assay indicated that dCMP deaminase activity was inhibited in whole cells, an action that was associated with a decreased dCTP:dTTP value. In addition, dFdCTP inhibited partially purified dCMP deaminase with a 50% inhibitory concentration of 0.46 mM. We conclude that dFdC-induced inhibition of dCMP deaminase resulted in a decrease of dFdCTP catabolism, contributing to the concentration-dependent elimination kinetics. This action constitutes a self-potentiation of dFdC activity.