Kuehl M, Brixner D I, Broom A D, Avery T L, Blakley R L
Department of Biochemical and Clinical Pharmacology, St. Jude Children's Research Hospital, Memphis, Tennessee 38101.
Cancer Res. 1988 Mar 15;48(6):1481-8.
In contrast to methotrexate (MTX) and aminopterin (AMT), the 8-deaza analogues of these antifolates are not substrates for rabbit liver aldehyde oxidase. Since they are not converted to 7-hydroxy derivatives, they have been investigated with regard to their cytotoxicity for CCRF-CEM cells, transport into these cells, and conversion to polyglutamate forms. For this purpose 3H-labeled analogues were synthesized. The drug concentrations of the analogues required to inhibit cell growth by 50% are significantly lower than for the parent compounds particularly for a short exposure of cells to the drug. Vmax and Km for unidirectional influx do not differ greatly among the four drugs, but amounts of uptake over 1 h are markedly different and increase in the order MTX less than 8-deazaMTX less than AMT less than 8-deazaAMT. During 1 h of uptake a much greater proportion of the 8-deaza analogues is converted to polyglutamate forms than in the case of parent drugs. Only 52% of MTX is converted to polyglutamates, whereas in the case of the other three compounds the conversion is greater than or equal to 90%. However, MTX is relatively efficient in adding two glutamate residues, whereas the other drugs predominantly accumulate as forms with only one additional glutamate (+Glu1). During 1 h of efflux the drugs without additional glutamates decrease to low concentrations and there is also a major loss of +Glu1 form, but there is also an increase in longer chain forms, especially in the case of MTX. The net result is a still greater disparity in total intracellular levels of the four drugs after the period of efflux. MTX has much lower toxicity in mice in vivo than the other three compounds, 8-deazaAMT being the most toxic. At the maximum tolerated dose MTX produced a considerably greater increase in life span for mice bearing P388 than any of the other drugs, and a somewhat greater increase for mice bearing L1210. Thus the 8-deaza analogues do not offer a therapeutic advantage over MTX against leukemias in the mouse, primarily due to their much greater toxicity.
与甲氨蝶呤（MTX）和氨基蝶呤（AMT）不同，这些抗叶酸药物的8-脱氮类似物不是兔肝醛氧化酶的底物。由于它们不会转化为7-羟基衍生物，因此已对其对CCRF-CEM细胞的细胞毒性、进入这些细胞的转运以及转化为多聚谷氨酸形式进行了研究。为此合成了3H标记的类似物。抑制细胞生长50%所需的类似物药物浓度明显低于母体化合物，特别是在细胞短期接触药物的情况下。四种药物的单向流入的Vmax和Km差异不大，但1小时内的摄取量明显不同，且按MTX＜8-脱氮MTX＜AMT＜8-脱氮AMT的顺序增加。在摄取1小时期间，8-脱氮类似物转化为多聚谷氨酸形式的比例比母体药物的情况要大得多。只有52%的MTX转化为多聚谷氨酸，而其他三种化合物的转化率大于或等于90%。然而，MTX在添加两个谷氨酸残基方面相对有效，而其他药物主要以仅添加一个额外谷氨酸（+Glu1）的形式积累。在流出1小时期间，没有额外谷氨酸的药物浓度降至低水平，+Glu1形式也有大量损失，但长链形式也有所增加，尤其是MTX的情况。净结果是在流出期后四种药物的细胞内总水平差异更大。MTX在小鼠体内的毒性比其他三种化合物低得多，8-脱氮AMT毒性最大。在最大耐受剂量下，MTX使携带P388的小鼠寿命延长的幅度比任何其他药物都大得多，对携带L1210的小鼠寿命延长幅度也稍大一些。因此，8-脱氮类似物在对抗小鼠白血病方面并不比MTX具有治疗优势，主要是因为它们的毒性大得多。
