title: Cytotoxicity, uptake, polyglutamate formation, and antileukemic effects of 8-deaza analogues of methotrexate and aminopterin in mice.
abstract: 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.
mesh_terms: D000630:Aminopterin / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D002470:Cell Survival / Q000187:drug effects; D005260:Female; D005493:Folic Acid Antagonists / Q000494:pharmacology*; D006801:Humans; D006900:Hydroxylation; D007942:Leukemia, Experimental / Q000188:drug therapy*; D008727:Methotrexate / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D051379:Mice; D008815:Mice, Inbred Strains; D010455:Peptides / Q000378:metabolism*; D011099:Polyglutamic Acid / Q000378:metabolism*; D011817:Rabbits; D013762:Tetrahydrofolate Dehydrogenase / Q000032:analysis
chemical_list: D000970:Antineoplastic Agents; D005493:Folic Acid Antagonists; D010455:Peptides; D011099:Polyglutamic Acid; D013762:Tetrahydrofolate Dehydrogenase; D000630:Aminopterin; D008727:Methotrexate