Platinum drug-DNA interactions in human tissues measured by cisplatin-DNA enzyme-linked immunosorbent assay and atomic absorbance spectroscopy

Abstract

Studies of platinum drug-DNA adduct formation in tissues of cancer patients have involved both atomic absorbance spectroscopy (AAS), which measures total DNA-bound platinum, and anti-cisplatin-DNA enzyme-linked immunosorbent assay (ELISA), which detects a fraction of the AAS-measurable adduct. These studies were designed to explore mechanisms of drug-DNA interactions, to make correlations with clinical outcome, and possibly to validate DNA adduct measurements for use in occupational and environmental biomonitoring. The results, determined by both ELISA and AAS, demonstrate that cisplatin and its analog carboplatin bind to DNA in many human organs, including kidney, brain, peripheral nerve, and bone marrow, which are sites for drug toxicity. Platinum was also observed bound to ovarian tumor DNA. The adducts were highly persistent, being measurable in tissues obtained at autopsy up to 15 months after the last administration of platinum chemotherapy. A comparison of blood cell DNA adduct levels, determined by ELISA, and the clinical response of 139 patients with ovarian, testicular, colon, or breast cancer demonstrated a strong correlation between failure to form DNA adducts and failure of therapy. Conversely, patients who formed high levels of DNA adduct were most likely to respond favorably. A similar correlation was not observed for adducts determined by AAS; that is, the average total DNA-bound platinum levels were the same for patients who did not respond to therapy and for patients who had any kind of response. Thus, in this study, human blood cell DNA adducts measured by ELISA correlate with tumor remission, while those measured by AAS do not.