Characterization of the adducts produced in
DNA by the
cancer chemotherapeutic
drug cis-diamminedichloroplatinum(II) and a radiolabeled analogue, [3H]-
cis-dichloro(ethylenediamine)platinum(II) ([3H]-cis-
DEP) was recently reported [Eastman, A. (1983) Biochemistry 22, 3927]. Both drugs reacted at identical sites in
DNA, most of which produced intrastrand cross-links.
DNA-interstrand cross-links, which represent less than 1% of total platination, have now been characterized.
DNA containing interstrand cross-links was enriched for on the basis of its renaturability after boiling. This
DNA was digested to
deoxyribonucleosides, and the adducts were separated by high-pressure liquid chromatography. A cross-link between two deoxyguanosines was observed to be the most prominent adduct. It is proposed that the major sequence in which this cross-link occurs is 5'-CG-3'.
DNA that was incubated with [3H]-cis-
DEP for 1 h showed low levels of interstrand cross-links. After removal of unreacted
drug, their frequency increased significantly over 6 h with a maximum occurring at about 12 h. A similar phenomenon was seen in the case of intrastrand cross-links that contained
adenine, in particular when the cross-link was between the terminal bases in an ANG trinucleotide sequence (N is any
nucleotide). The primary site of reaction is at
guanine, with a slow subsequent cross-link to the
adenine. A model is presented that is consistent with the observation that
adenine is always at the 5' terminus of these adducts. The proportion of adducts at ANG sequences also increased at elevated temperatures. This is discussed with regard to potential significance during
hyperthermia treatment of patients.(ABSTRACT TRUNCATED AT 250 WORDS)