DNA minor groove targeted alkylating agents based on bisbenzimidazole carriers: synthesis, cytotoxicity and sequence-specificity of DNA alkylation.

摘要: A series of bisbenzimidazoles bearing a variety alkylating agents [ortho- and meta-mustards, imidazolebis(hydroxymethyl), imidazolebis(methylcarbamate) pyrrolebis(hydroxymethyl)], appended by propyl linker chain, were prepared investigated for sequence-specificity DNA alkylation their cytotoxicity. Previous work has shown that, para-aniline mustards, is optimal Alkaline cleavage assays using different labelled oligonucleotides showed that the preferred sequences adenine 5'-TTTANANAANN 5'-ATTANANAANN (underlined bases show drug sites), with AT-rich required on both 5' 3' sides alkylated adenine. The aniline mustards little variation in pattern similar efficiencies cross-link formation despite changes orientation positioning mustard, suggesting some flexibility. imidazole- pyrrolebis(hydroxymethyl) alkylators no strand following base treatment, indicating guanine or N3 N7 adducts formed. Using PCR-based polymerase stop assay, these PCR blocks at 5'-C*G sites (the * nucleotide indicates blocked site), particularly 5'-TAC*GA 5'-AGC*GGA, 5'-AGCC*GGT sequences, caused 2-NH2 lesions opposite strand. Only (more reactive) imidazolebis(methylcarbamoyl) demonstrated interstrand cross-linking ability. All bifunctional large (approximately 100-fold) increases cytotoxicity over chlorambucil, corresponding monofunctional being 20- to 60-fold less cytotoxic. These results suggest provides sufficient flexibility achieve delivery alkylator favoured (adenine N3) minor groove, regardless its exact geometry respect bisbenzimidazole carrier. 'targeted' bis(hydroxymethyl)pyrrole- imidazole analogues very patterns 'untargeted' compounds, evidence additional selectivity imposed this AT-preferring