The interaction of DNA-targeted 9-aminoacridine-4-carboxamide platinum complexes with DNA in intact human cells

As part of an ongoing drug development programme, this paper describes the sequence specificity and time course of DNA adduct formation for a series of novel DNA-targeted analogues of cis-diaminedichloroplatinum(II) (cisplatin) (9-aminoacridine-4-carboxamide Pt complexes) in intact HeLa cells. The sequence specificity of DNA damage caused by cisplatin and analogues in human (HeLa) cells was studied using Taq DNA polymerase and a linear amplification/polymerase stop assay. Primer extension is inhibited by a Pt-DNA adduct, and hence the sites of these lesions can be analysed on DNA sequencing gels. The repetitive alphoid DNA sequence was used as the target DNA in human cells. The 9-aminoacridine-4-carboxamide Pt complexes exhibited a markedly different sequence specificity relative to cisplatin and other analogues. The sequence specificity of the 9-aminoacridine-4-carboxamide Pt complexes is shifted away from a preference for runs of guanines. The 9-aminoacridine-4-carboxamide Pt complexes have an enhanced preference for GA dinucleotides. This is the first occasion that an altered DNA sequence specificity has been demonstrated for a cisplatin analogue in human cells. A time course of DNA damage revealed that the DNA-targeted Pt complexes, consisting of four 9-aminoacridine-4-carboxamide Pt complexes and one acridine-4-carboxamide Pt complex, damaged DNA more rapidly compared to cisplatin and non-targeted analogues. A comparison of the time taken to reach half the maximum relative intensity indicated that the DNA-targeted Pt complexes reacted approximately 4-fold faster than cisplatin and the non-targeted analogues.