Influence of the degree of DNA modification on the immunochemical determination of cisplatin-DNA adduct levels.

Two different enzyme-linked immunosorbent assays (ELISAs) are used for the sensitive determination of cisplatin-DNA adducts in, for example, blood cells of cisplatin-treated cancer patients. Poirier et al. determined the adducts in native DNA with an antiserum raised against highly modified cisplatin-DNA. Fichtinger-Schepman et al. assayed the various adducts after chromatography of enzymatically digested DNA samples, with antibodies raised against synthetic haptens mimicking the Pt-containing digestion products. In identical human samples analysed by both methods, 14- to 300-fold higher adduct levels were found with the Fichtinger-Schepman method. Adduct levels in organ samples of cisplatin-treated rats and mice allowed comparison of both ELISAs with independent Pt assays (atomic absorption spectroscopy, AAS). AAS data confirmed the results of the Fichtinger-Schepman assay, whereas ELISAs according to Poirier showed differences up to a factor of 1000. Analysis of cisplatin adducts in in vitro modified DNA revealed that the Poirier antibodies yield correct estimates with highly modified DNA, but fall short at low platination levels: no adducts could be detected in samples modified to a level similar to that found in blood cells from cisplatin-treated patients. The positive responses obtained with samples of such patients, who had been treated repeatedly, might be explained if cisplatin adducts are preferentially formed around persistent lesions from the previous treatments.