Use of Antibodies To Probe the Stereochemistry of Antitumor Platinum Drug Binding to Deoxyribonucleic Acid

A previously prepared antiserum elicited against DNA modified with cis-diamminedichloroplatinum(II) (cis-DDP) (Poirier et al., 1982) was found by a competitive enzyme-linked immunosorbent assay (ELISA) to show high specificity for cis-DDP bound to poly(dG)·poly(dC) but not to the alternating heterocopolymer poly[d(GC)]·poly[d(GC)]. Poor immunoreactivity was shown toward calf thymus DNA modified by a variety of antitumor-inactive platinum analogues including trans-DDP, trans-[Pt(NH₂CH₃)₂Cl₂], and [Pt-(dien)Cl]Cl whereas the antiserum exhibited good specificity for DNA modified by analogues having cis stereochemistry. Platinum complexes included in the latter category are [Pt-(en)Cl₂], cis-[Pt(NH₂CH₃)₂Cl₂], [Pt(CP)(DACH)], and cis-diammineplatinum α-pyridone blue. The ELISA immunoreactivity of cis-DDP-DNA treated with cyanide ion or thiourea after modification or with ethidium bromide during modification was also monitored. Taken together, the results of this study suggest that a primary three-dimensional structure recognized by the antibody is a bidentate adduct of cis-DDP in which two chloride ions have been replaced by two adjacent deoxyguanosines on the same DNA strand.