McGuire J J, Mini E, Hsieh P, Bertino J R
Cancer Res. 1985 Dec;45(12 Pt 1):6395-400.
The synthesis of methotrexate (MTX) polyglutamates has been investigated in a human leukemia cell line, CCRF-CEM. An increase in either the extracellular MTX concentration (0.1-10 microM) or exposure time (4-24 h) allowed a greater accumulation of polyglutamate derivatives. The species which predominated (di-, tri-, or tetraglutamate) was also time and concentration dependent. Derivatives up to the pentaglutamate were readily detectable, with hexaglutamate present under some conditions. Polyglutamate derivatives were preferentially retained when the cells were transferred to drug-free medium. MTX itself rapidly exited the cells under these conditions. In the absence of extracellular MTX, the performed intracellular MTX polyglutamates continued to be elongated. Accumulation of MTX polyglutamates, particularly triglutamate and longer species, positively correlated with cytotoxicity to CCRF-CEM cells as measured by a clonogenic assay. Investigation of the methotrexate-fluorouracil interaction revealed no effect of 5-fluorouracil on MTX polyglutamate accumulation under various conditions where widely different degrees of cytotoxicity were found. The synergy observed when MTX precedes fluorouracil treatment is therefore not an effect on MTX polyglutamylation. MTX polyglutamates may, however, play an indirect role in this synergy.
已在人白血病细胞系CCRF-CEM中研究了甲氨蝶呤（MTX）多聚谷氨酸盐的合成。细胞外MTX浓度（0.1 - 10 microM）或暴露时间（4 - 24小时）的增加都能使多聚谷氨酸衍生物有更多积累。占主导的种类（二聚、三聚或四聚谷氨酸）也与时间和浓度有关。直至五聚谷氨酸的衍生物都易于检测到，在某些条件下还存在六聚谷氨酸。当细胞转移至无药培养基时，多聚谷氨酸衍生物会被优先保留。在此条件下，MTX本身会迅速从细胞中排出。在没有细胞外MTX的情况下，已形成的细胞内MTX多聚谷氨酸盐会继续延长。通过克隆形成试验测定，MTX多聚谷氨酸盐的积累，尤其是三聚谷氨酸及更长链的种类，与对CCRF-CEM细胞的细胞毒性呈正相关。对甲氨蝶呤 - 氟尿嘧啶相互作用的研究表明，在发现细胞毒性程度差异很大的各种条件下，5 - 氟尿嘧啶对MTX多聚谷氨酸盐的积累没有影响。因此，MTX先于氟尿嘧啶治疗时观察到的协同作用并非对MTX多聚谷氨酰化的影响。然而，MTX多聚谷氨酸盐可能在这种协同作用中发挥间接作用。
