Several 8-substituted O6-benzylguanines, 2- and/or 8-substituted 6-(benzyloxy)purines, substituted 6(4)-(benzyloxy)pyrimidines, and a 6-(benzyloxy)-s-triazine were tested for their ability to inactivate the human DNA repair protein, O6-alkylguanine-DNA alkyltransferase (AGT, alkyltransferase). Two types of compounds were identified as being significantly more effective than O6-benzylguanine (the prototype low molecular weight inactivator) at inactivating AGT in human HT29 colon tumor cell extracts. These were 8-substituted O6-benzylguanines bearing electron-withdrawing groups at the 8-position (e.g. 8-aza-O6-benzylguanine and O6-benzyl-8- bromoguanine) and 5-substituted 2,4-diamino-6-(benzyloxy)pyrimidines bearing electron- withdrawing groups at the 5-position (e.g. 2,4-diamino-6-(benzyloxy)-5-nitroso- and 2,4-diamino- 6-(benzyloxy)-5-nitropyrimidine). The latter derivatives were also more effective than O6- benzylguanine at inactivating AGT in intact HT29 colon tumor cells. Provided these types of purines and pyrimidines do not exhibit undesirable toxicity, they may be superior to O6-benzylguanine as chemotherapeutic adjuvants for enhancing the effectiveness of antitumor drugs for which the mechanism of action involves modification of the Opposition of DNA guanine residues.
All Science Journal Classification (ASJC) codes
- Molecular Medicine
- Drug Discovery