Erba E, Sen S, Sessa C, Vikhanskaya F L, D'Incalci M
Istituto di Ricerche Farmacologiche Mario Negri, Milan, Italy.
Br J Cancer. 1994 Feb;69(2):205-11. doi: 10.1038/bjc.1994.40.
Inhibition of clonogenic potential by the glycinamideribonucleosyl transformylase inhibitor 5,10-dideazatetrahydrofolic acid (DDATHF, Lometrexol) was evaluated in vitro in a human ovarian carcinoma cell line, SW626. Drug-induced inhibition of clonogenic potential is a function of the dose and time of exposure and is independent of the formation of DNA single-strand breaks or de novo synthesis of protein. Simultaneous treatment with 100 microM hypoxanthine completely prevented the inhibition of clonogenic potential caused by 0.5 microM DDATHF. DDATHF blocked cells in the early-middle S-phases of the cell cycle, and there was a corresponding marked reduction in the rate of DNA synthesis after drug withdrawal. The cytotoxic potential of DDATHF was modulated by the folic acid concentration present in the medium. In a medium containing 0.22 microM folic acid, DDATHF cytotoxicity was at least 100 times that in a regular medium containing 2.22 microM folic acid, levels which, however, are about 100 times those found in human plasma. DDATHF cytotoxicity differed moderately when folic acid concentrations varied between 0.22 and 0 microM, suggesting that folic acid does not necessarily antagonise DDATHF anti-tumour activity. Folinic acid at a concentration as low as 0.1 microM can completely rescue cells when given simultaneously with 0.5 microM DDATHF. When folinic acid was given 24 h after DDATHF, a reversal of cytotoxicity was observed at 0.5 and 1 microM, but to a much lesser extent than simultaneous treatment. When folinic acid was added after 48 or 72 h of DDATHF washout, even at a high concentration and for a long time, no reduction in DDATHF cytotoxicity was found. In conclusion, the study highlights the modulation of DDATHF cytotoxicity by folic acid or by folinic acid and provides further rationale for in vivo clinical investigation with these combinations.
在人卵巢癌细胞系SW626中对甘氨酰胺核糖基转甲酰基酶抑制剂5,10 - 二去氮四氢叶酸（DDATHF，洛美曲索）抑制克隆形成潜力进行了体外评估。药物诱导的克隆形成潜力抑制是暴露剂量和时间的函数，且与DNA单链断裂的形成或蛋白质的从头合成无关。用100微摩尔次黄嘌呤同时处理可完全防止0.5微摩尔DDATHF引起的克隆形成潜力抑制。DDATHF使细胞阻滞在细胞周期的早中期S期，撤药后DNA合成速率相应显著降低。DDATHF的细胞毒性潜力受培养基中叶酸浓度调节。在含有0.22微摩尔叶酸的培养基中，DDATHF的细胞毒性至少是含有2.22微摩尔叶酸的常规培养基中的100倍，然而，这些水平约为人血浆中叶酸水平的100倍。当叶酸浓度在0.22和0微摩尔之间变化时，DDATHF的细胞毒性有适度差异，表明叶酸不一定拮抗DDATHF的抗肿瘤活性。当与0.5微摩尔DDATHF同时给予时，低至0.1微摩尔浓度的亚叶酸可完全挽救细胞。当在DDATHF给药24小时后给予亚叶酸时，在0.5和1微摩尔浓度下观察到细胞毒性逆转，但程度远小于同时处理。当在DDATHF洗脱48或72小时后添加亚叶酸时，即使浓度高且时间长，也未发现DDATHF细胞毒性降低。总之，该研究突出了叶酸或亚叶酸对DDATHF细胞毒性的调节作用，并为这些联合用药的体内临床研究提供了进一步的理论依据。
