Role of thymidine kinase and thymidylate synthetase in the cytostatic, antimetabolic, and antitumor effects of the carbocyclic analogue of 5-nitro-2'-deoxyuridine. A comparison with 5-nitro-2'-deoxyuridine.
The carbocyclic analogue of 5-nitro-2'-deoxyuridine (NO2dUrd), in which the sugar moiety is replaced by a cyclopentane ring and which was designated C-NO2dUrd, has been evaluated for its cytostatic, antimetabolic, and antitumor properties. The following findings are noted. C-NO2dUrd is about 500- to 2000-fold less inhibitory to tumor cell proliferation in vitro than NO2dUrd. Phosphorolysis of C-NO2dUrd by rabbit liver extracts was not observed under conditions where NO2dUrd was readily converted to 5-nitrouracil (NO2Ura). Also, C-NO2dUrd is converted to its 5'-monophosphate (C-NO2dUMP) by dThd kinase nearly as efficiently as the true nucleoside NO2dUrd. This metabolic conversion is necessary for the inhibitory effect of C-NO2dUrd on tumor cell proliferation in cell culture. The principal target enzyme for the cytostatic action of C-NO2dUrd is 2'-deoxythymidylate (dTMP) synthetase. C-NO2dUMP, the active metabolite of C-NO2dUrd, has a much lower affinity for dTMP synthetase than does NO2dUMP. This is the first demonstration of the interaction of a carbocyclic pyrimidine nucleotide analogue with dTMP synthetase. Neither NO2dUrd nor C-NO2dUrd exerts any significant antitumor activity in mice bearing L1210 or P388 leukemia; for NO2dUrd, this failure may be related to a rapid degradation to its inactive metabolite, NO2Ura; for C-NO2dUrd, it is most likely due to a decreased affinity of C-NO2dUMP for its target enzyme, dTMP synthetase.
D000818:Animals; D000963:Antimetabolites / Q000494:pharmacology*; D000970:Antineoplastic Agents / Q000494:pharmacology*; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D003857:Deoxyuridine / Q000031:analogs & derivatives* / Q000494:pharmacology; D006801:Humans; D008780:Methyltransferases / Q000037:antagonists & inhibitors*; D051379:Mice; D051381:Rats; D013937:Thymidine Kinase / Q000037:antagonists & inhibitors*; D013939:Thymidine Phosphorylase / Q000037:antagonists & inhibitors; D013940:Thymidylate Synthase / Q000037:antagonists & inhibitors*; D014498:Uracil / Q000031:analogs & derivatives* / Q000494:pharmacology
D000963:Antimetabolites; D000970:Antineoplastic Agents; C045263:N(1)-cyclopentyl-5-nitropyrimidine-2,4-dione; C016012:5-nitro-2'-deoxyuridine; D014498:Uracil; D008780:Methyltransferases; D013940:Thymidylate Synthase; D013939:Thymidine Phosphorylase; D013937:Thymidine Kinase; D003857:Deoxyuridine