title: Increased killing of prostate, breast, colon, and lung tumor cells by the combination of inactivators of O6-alkylguanine-DNA alkyltransferase and N,N'-bis(2-chloroethyl)-N-nitrosourea.
abstract: The ability of a number of compounds that act as inactivators of O6-alkylguanine-DNA alkyltransferase (AGT) to sensitize human tumor cell lines to the effects of N,N'-bis(2-chloroethyl)-N-nitrosourea (BCNU) were examined. The AGT inactivators tested included O6-benzylguanine (BG) and its 8-aza-, 8-bromo-, 8-methyl-, 8-oxo, and 8-amino-derivatives and O6-[p-(hydroxymethyl)benzyl]guanine. All of these compounds except the 8-amino-derivative were active in greatly increasing the killing of HT29 colon, Du145 prostate, MCF-7 breast and A549 lung tumor cells by BCNU. Their activities were comparable to those of BG. Two pyrimidines, 2,4-diamino-6-benzyloxy-5-nitrosopyrimidine and 2,4-diamino-6-benzyloxy-5-nitropyrimidine, were found to be considerably more potent than BG in enhancing BCNU-induced cell killing. The addition of a steroid group to the 9-position of BG forming either O6-benzyl-9-[3-oxo-4-androsten-17 beta-yloxycarbonyl)methyl]guanine or O6-benzyl-9-[3-oxo-5 alpha-androstan-17 beta-yloxycarbonyl)methyl]guanine also produced compounds effective in enhancing the cytotoxicity of BCNU when added at 10 microM. These results indicate that a range of potent compounds with potentially different pharmacokinetics is available to test the hypothesis that inactivation of AGT overcomes the resistance of many tumor cells to nitrosoureas.
mesh_terms: D018906:Antineoplastic Agents, Alkylating / Q000494:pharmacology*; D002330:Carmustine / Q000494:pharmacology*; D016923:Cell Death / Q000187:drug effects; D004351:Drug Resistance; D004359:Drug Therapy, Combination; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006147:Guanine / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000494:pharmacology; D006801:Humans; D008780:Methyltransferases / Q000037:antagonists & inhibitors*; D019853:O(6)-Methylguanine-DNA Methyltransferase; D014407:Tumor Cells, Cultured / Q000187:drug effects* / Q000378:metabolism
chemical_list: D018906:Antineoplastic Agents, Alkylating; D004791:Enzyme Inhibitors; C064976:O(6)-benzylguanine; D006147:Guanine; D008780:Methyltransferases; D019853:O(6)-Methylguanine-DNA Methyltransferase; D002330:Carmustine