Mini E, Mazzei T, Coronnello M, Criscuoli L, Gualtieri M, Periti P, Bertino J R
Biochem Pharmacol. 1987 Sep 15;36(18):2905-11. doi: 10.1016/0006-2952(87)90201-2.
The growth inhibitory effects of 5-fluorouracil (FUra) or 5-fluoro-2'-deoxyuridine (FdUrd) combined with 5-methyltetrahydrofolate (5-CH3-H4PteGlu) were determined, as a function of time, dose, and sequence of exposure, on human T-lymphoblast leukemia cells, CCRF-CEM. Synergistic inhibitory effects on cell growth were obtained when exponentially growing CCRF-CEM cells were exposed to 5-CH3-H4PteGlu (1-100 microM) for 4 hr and to FUra (250 microM) or FdUrd (0.5 microM) during the last 2 hr. Synergism was dependent on 5-CH3-H4PteGlu dose (100 greater than 10 greater than 1 microM) and did not occur at 0.1 microM. No clear dependence of synergism on sequence was observed with FUra and 5-CH3-H4PteGlu combinations (5-CH3-H4PteGlu----FUra,5-CH3-H4PteGlu + FUra, or FUra----5-CH3-H4PteGlu). With 5-CH3-H4PteGlu and FdUrd combinations, synergism was dependent on sequence of exposure (5-CH3-H4PteGlu + FdUrd, 5-CH3-H4PteGlu----FdUrd were synergistic, but FdUrd----5-CH3-H4PteGlu was not). Thymidine (0.1 microM), added after drug treatment, substantially rescued CCRF-CEM cells from 5-CH3-H4PteGlu----FUra cytotoxicity. L-methionine (1500 mg/l) completely protected CCRF-CEM cells from enhanced cytotoxicity of the combination, 5-CH3-H4PteGlu-FdUrd. The results are consistent with the hypothesis that the mechanism by which 5-CH3-H4PteGlu potentiates fluoropyrimidine cytotoxicity is the enhancement of complex formation between thymidylate synthase and 5-fluorodeoxyuridylate, as a consequence of an increase of intracellular levels of 5,10-methylenetetrahydrofolate generated from 5-CH3-H4PteGlu. Also, enhanced stability of the complex in the presence of high levels of this folate coenzyme may contribute to the synergism observed. These data provide a rationale basis for further trials of folate coenzymes and fluoropyrimidine combinations in the clinic.
研究了5-氟尿嘧啶（FUra）或5-氟-2'-脱氧尿苷（FdUrd）与5-甲基四氢叶酸（5-CH3-H4PteGlu）联合使用时，其生长抑制作用随时间、剂量和暴露顺序的变化情况，作用对象为人T淋巴细胞白血病细胞CCRF-CEM。当处于指数生长期的CCRF-CEM细胞先暴露于5-CH3-H4PteGlu（1 - 100 microM）4小时，然后在最后2小时暴露于FUra（250 microM）或FdUrd（0.5 microM）时，可获得对细胞生长的协同抑制作用。协同作用取决于5-CH3-H4PteGlu的剂量（100 microM > 10 microM > 1 microM），在0.1 microM时不发生。对于FUra和5-CH3-H4PteGlu的组合（5-CH3-H4PteGlu→FUra、5-CH3-H4PteGlu + FUra或FUra→5-CH3-H4PteGlu），未观察到协同作用对暴露顺序有明显依赖性。对于5-CH3-H4PteGlu和FdUrd的组合，协同作用取决于暴露顺序（5-CH3-H4PteGlu + FdUrd、5-CH3-H4PteGlu→FdUrd具有协同作用，但FdUrd→5-CH3-H4PteGlu则没有）。药物处理后添加胸苷（0.1 microM）可使CCRF-CEM细胞基本免受5-CH3-H4PteGlu→FUra的细胞毒性作用。L-蛋氨酸（1500 mg/l）可完全保护CCRF-CEM细胞免受5-CH3-H4PteGlu - FdUrd组合增强的细胞毒性作用。这些结果与以下假设一致，即5-CH3-H4PteGlu增强氟嘧啶细胞毒性的机制是由于5-CH3-H4PteGlu产生的细胞内5,10-亚甲基四氢叶酸水平增加，从而增强了胸苷酸合成酶与5-氟脱氧尿苷酸之间的复合物形成。此外，在高水平这种叶酸辅酶存在下复合物稳定性的增强可能也有助于观察到的协同作用。这些数据为临床上进一步试验叶酸辅酶与氟嘧啶组合提供了理论依据。
