Role of thymidylate synthetase activity in development of methotrexate cytotoxicity.
Role of thymidylate synthetase activity in development of methotrexate cytotoxicity.
复制标题
胸苷酸合成酶活性在甲氨蝶呤细胞毒性发展中的作用。
DOI：
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发表时间：
1979
影响因子：
11.1
通讯作者：
James T. Grace
中科院分区：
文献类型：
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作者：
Richard G. Moran;Mary MULKINSt;Charles HEIDELBERGERt;James T. Grace
甲氨蝶呤（MTX）抑制小鼠或人白血病细胞在培养中的生长被部分阻止胸苷（dThd）或次黄嘌呤。5-氟-2 '-脱氧尿苷（FdUrd）也降低了MTX在低浓度5-甲酰四氢叶酸（柠檬酸因子）和足够的外源性dThd存在下的生长抑制效力，以支持胸苷酸核苷酸的合成通过补救机制。此外，在存在FdUrd和dThd的情况下，比单独存在dThd或不存在两种核苷的情况下，食柠檬酸因子诱导的MTX逆转的效率高几个数量级。同样，FdUrd（3 μ M）和dThd（5.6 μ M）的存在完全阻止了0.3 mM MTX对补充有微摩尔浓度的食柠檬酸因子的培养基中的L1210细胞的致死性。我们认为dThd、次黄嘌呤和FdUrd对MTX细胞毒性作用的保护作用具有共同的生化机制-即通过直接[FdUrd;抑制胸苷酸合成酶（胸苷酸合成酶; 5，10-亚甲基四氢叶酸：dUMP C-甲基转移酶，EC 2.1.1.45）]或间接（dThd和次黄嘌呤;腺苷酸对核糖核苷酸还原酶和脱氧胞苷酸脱氨酶的反馈抑制）作用抑制胸苷酸的从头合成。由于从头胸苷酸合成而导致的还原叶酸损失速率的降低将允许耐受更高程度的二氢叶酸还原酶抑制而不损害细胞。
Methotrexate (MTX) inhibition of the growth of mouse or human leukemia cells in culture was partially prevented by either thymidine (dThd) or hypoxanthine. 5-Fluoro-2'-deoxyuridine (FdUrd) also decreased the growth-inhibitory potency of MTX in the presence of small concentrations of 5-formyltetrahydrofolate (citrovorum factor) and sufficient exogenous dThd to support the synthesis of thymidylate nucleotides by salvage mechanisms. In addition, citrovorum factor-induced reversal of MTX was several orders of magnitude more efficient in the presence of both FdUrd and dThd than in the presence of dThd alone or in the absence of both nucleosides. Likewise, the presence of FdUrd (3 microM) and dThd (5.6 microM) completely prevented the lethality of 0.3 mM MTX to L1210 cells in culture medium supplemented with micromolar concentrations of citrovorum factor. We propose that this protection against the cytotoxic effects of MTX by dThd, hypoxanthine, and FdUrd have a common biochemical mechanism--namely, inhibition of the de novo synthesis of thymidylate by either a direct [FdUrd; inhibition of thymidylate synthetase (thymidylate synthase; 5,10-methylenetetrahydrofolate:dUMP C-methyl-transferase, EC 2.1.1.45)] or indirect (dThd and hypoxanthine; feedback inhibition by anabolites on ribonucleotide reductase and deoxycytidylate deaminase) effect. The resultant decreased rate of loss of reduced folates due to de novo thymidylate synthesis would allow a higher degree of inhibition of dihydrofolate reductase to be endured without damage to the cell.