Waxman S, Schreiber C, Waxman S
Chemotherapy. 1982;28(5):402-9. doi: 10.1159/000238129.
Crude X-methyl folate and two purified fractions (purified X-methyl folate and 9-methyl folate) were evaluated as possible folic acid antagonists. Antifolate activity was measured by the deoxyuridine suppression assay, direct measurement of dihydrofolate reductase and morphological changes characteristic of folate deficiency. Cytotoxicity was evaluated by cell growth curves. These drugs were studied in freshly obtained human normal evaluated by cell growth curves. These drugs were studied in freshly obtained human normal bone marrow and leukemia cells as well as in three established cell lines HL-60 (human promyelocytic leukemia), CEM (human T lymphocytes), and L1210 (murine lymphoid leukemia). Purified X-methyl folate and 9-methyl folate at concentrations up to 2X10(-5) M failed to induce cell toxicity or inhibit deoxyuridine suppression of 3H-thymidine into DNA. Dihydrofolate reductase was not inhibited by 9-methyl folate but was partially inhibited by purified X-methyl folate. Crude X-methyl folate (2X10(-1) M) is a weak folate antagonist as compared to methotrexate since it requires a 1,000-fold higher concentration to inhibit cell growth and dihydrofolate reductase activity. In addition, the crude X-methyl folate contains a folate-like fraction since it will correct the abnormal deoxyuridine suppression in folate-depleted cells. None of the drugs tested were able to induce myeloid differentiation in the HL-60 cells. The data suggest that 9-methyl folate would not be active as a folate antagonist antitumor agent and that purified and crude X-methyl folate in large concentrations will inhibit folate metabolism. Additional studies are needed to remove the folate-like activity in the crude material in order to further establish the antitumor effects of the crude X-methyl folate.
粗制X-甲基叶酸盐和两个纯化组分（纯化的X-甲基叶酸盐和9-甲基叶酸盐）被评估为可能的叶酸拮抗剂。通过脱氧尿苷抑制试验、二氢叶酸还原酶的直接测定以及叶酸缺乏特征性的形态学变化来测量抗叶酸活性。通过细胞生长曲线评估细胞毒性。在新鲜获取的人正常骨髓和白血病细胞以及三种已建立的细胞系HL-60（人早幼粒细胞白血病）、CEM（人T淋巴细胞）和L1210（鼠类淋巴白血病）中对这些药物进行了研究。浓度高达2×10⁻⁵ M的纯化X-甲基叶酸盐和9-甲基叶酸盐未能诱导细胞毒性或抑制脱氧尿苷对³H-胸苷掺入DNA的抑制作用。9-甲基叶酸盐不抑制二氢叶酸还原酶，但纯化的X-甲基叶酸盐可部分抑制该酶。与甲氨蝶呤相比，粗制X-甲基叶酸盐（2×10⁻¹ M）是一种弱叶酸拮抗剂，因为它需要高1000倍的浓度才能抑制细胞生长和二氢叶酸还原酶活性。此外，粗制X-甲基叶酸盐含有一种叶酸样组分，因为它能纠正叶酸缺乏细胞中异常的脱氧尿苷抑制作用。所测试的药物均不能诱导HL-60细胞发生髓系分化。数据表明，9-甲基叶酸盐作为叶酸拮抗剂抗肿瘤药物无活性，高浓度的纯化和粗制X-甲基叶酸盐会抑制叶酸代谢。需要进一步研究去除粗制品中的叶酸样活性，以便进一步确定粗制X-甲基叶酸盐的抗肿瘤作用。
