Sokoloski J A, Beardsley G P, Sartorelli A C
Department of Pharmacology, Yale University School of Medicine, New Haven, CT 06510-8066.
Cancer Commun. 1989;1(3):199-207.
The classic inhibitor of dihydrofolate reductase (DHFR), methotrexate (MTX), has been shown to be an effective inducer of the differentiation of HL-60 promyelocytic leukemia cells (Bodner A.J. et al.; J. Natl. Cancer Inst. 67:1025-1030; 1981). We have obtained evidence that induction of the differentiation of these cells by MTX, as well as by other folic acid antagonists, is the result of the effects of these agents on purine and thymine nucleotide biosynthesis. Thymidine (10 microM) completely blocked both the cytotoxicity and induction of differentiation produced by the specific inhibitor of thymidylate synthase (TS), N10-propargyl-5,8-dideazafolic acid (CB-3717). Thymidine also blocked the acute cytotoxicity caused by MTX and trimetrexate (TMQ); the induction of differentiation and the loss of proliferative capacity, however, were only partially prevented by thymidine. Hypoxanthine (100 microM), which completely restored antifolate-depleted purine nucleotide levels, had no effect on either the cytotoxicity or the induction of maturation produced by these agents. The growth inhibitory effects and the induction of differentiation caused by dideazatetrahydrofolic acid (DDATHF), which acts on de novo purine nucleotide biosynthesis rather than on DHFR or TS, was completely prevented by hypoxanthine. Hypoxanthine also completely prevented the inhibition of cellular replication and induction of differentiation by MTX and TMQ when combined with thymidine. The findings suggest that the depletion of intracellular thymine nucleotide levels by the antifolates, MTX, TMQ, and CB-3717 is the primary event involved in the maturation of HL-60 leukemia cells produced by these agents and that maturation occurs concomitantly with a high level of cytotoxicity.(ABSTRACT TRUNCATED AT 250 WORDS)
二氢叶酸还原酶（DHFR）的经典抑制剂甲氨蝶呤（MTX）已被证明是HL-60早幼粒细胞白血病细胞分化的有效诱导剂（博德纳A.J.等人；《国家癌症研究所杂志》67:1025 - 1030；1981年）。我们已获得证据表明，MTX以及其他叶酸拮抗剂诱导这些细胞分化是这些药物对嘌呤和胸腺嘧啶核苷酸生物合成产生作用的结果。胸苷（10微摩尔）完全阻断了胸苷酸合成酶（TS）的特异性抑制剂N10 - 炔丙基 - 5,8 - 二氮杂叶酸（CB - 3717）产生的细胞毒性和分化诱导作用。胸苷还阻断了MTX和三甲曲沙（TMQ）引起的急性细胞毒性；然而，胸苷仅部分阻止了分化诱导和增殖能力的丧失。次黄嘌呤（100微摩尔）可完全恢复抗叶酸剂耗尽的嘌呤核苷酸水平，但对这些药物产生的细胞毒性或成熟诱导均无影响。二氮杂四氢叶酸（DDATHF）作用于嘌呤核苷酸的从头合成而非DHFR或TS，其产生的生长抑制作用和分化诱导作用被次黄嘌呤完全阻止。当与胸苷联合使用时，次黄嘌呤也完全阻止了MTX和TMQ对细胞复制的抑制及分化诱导。这些发现表明，抗叶酸剂MTX、TMQ和CB - 3717使细胞内胸腺嘧啶核苷酸水平耗竭是这些药物导致HL - 60白血病细胞成熟的主要事件，且成熟与高水平的细胞毒性同时发生。（摘要截选至250字）
