title: Inhibition of human O6-alkylguanine-DNA alkyltransferase and potentiation of the cytotoxicity of chloroethylnitrosourea by 4(6)-(benzyloxy)-2,6(4)-diamino-5-(nitro or nitroso)pyrimidine derivatives and analogues.
abstract: A series of 4(6)-(benzyloxy)-2,6(4)-diamino-5-(nitro or nitroso)pyrimidine derivatives and analogues of which 4(6)-benzyloxy groups were replaced with a (2-, 3-, or 4-fluorobenzyl)oxy or (2-, 3-, or 4-pyridylmethyl)oxy group, was synthesized. The abilities of these compounds to inhibit human O6-alkylguanine-DNA alkyltransferase (AGAT) in vitro and to potentiate the cytotoxicity of 1-[(4-amino-2-methyl-5-pyrimidinyl)methyl]-3-(2-chloroethyl) -3-nitrosourea (ACNU) toward HeLa S3 cells were evaluated. 2,4-Diamino-6-[(2-fluorobenzyl)oxy]-5-nitropyrimidine (3) and 2,4-diamino-5-nitro-6-(2-pyridylmethoxy)pyrimidine (6), whose ortho positions of the 6-substituent are modified, were much weaker in terms of these abilities than the corresponding meta- or para-modified compounds. These results are consistent with those of our previous study using a series of O6-benzylguanine derivatives. All 5-nitrosopyrimidine derivatives examined exerted both stronger AGAT-inhibition and ACNU-enhancement abilities than the corresponding 5-nitro derivatives. Among a variety of compounds that we have examined to date, 2,4-diamino-6-[(4-fluorobenzyl)oxy]-5-nitrosopyrimidine (10) exhibited the strongest ability to inhibit AGAT, and its magnitude was 2.5 and 50 times those of 4-(benzyloxy)-2,6-diamino-5-nitrosopyrimidine (9) and O6-benzylguanine (1), respectively. A strong positive correlation was observed between the ability to inhibit AGAT and to potentiate the cytotoxicity of ACNU. This strongly indicates that 4(6)-(benzyloxy)pyrimidine derivatives and their analogues potentiate ACNU cytotoxicity by inhibiting AGAT activity. To characterize the reactivity of test compounds, alkyl-transfer reactions were also carried out using the biomimetic alkyl-transfer system.
authors.affiliation: Faculty of Pharmaceutical Sciences, Nagoya City University, Japan.
authors.forename: I
authors.initials: I
authors.lastname: Terashima
authors.forename: K
authors.initials: K
authors.lastname: Kohda
mesh_terms: D002470:Cell Survival / Q000187:drug effects*; D003001:Cloning, Molecular; D004357:Drug Synergism; D004791:Enzyme Inhibitors / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D005038:Ethylnitrosourea / Q000031:analogs & derivatives* / Q000633:toxicity; D006367:HeLa Cells; D006801:Humans; D007202:Indicators and Reagents; D007700:Kinetics; D019853:O(6)-Methylguanine-DNA Methyltransferase / Q000037:antagonists & inhibitors*; D011743:Pyrimidines / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors; D013329:Structure-Activity Relationship
chemical_list: C110781:4-(benzyloxy)-2,6-diamino-5-nitropyrimidine; D004791:Enzyme Inhibitors; D007202:Indicators and Reagents; D011743:Pyrimidines; D011994:Recombinant Proteins; C017139:1-(2-chloroethyl)-1-nitrosourea; D019853:O(6)-Methylguanine-DNA Methyltransferase; D005038:Ethylnitrosourea