Use of a monoclonal antibody to detect DNA damage caused by the anticancer drug cis-diamminedichloroplatinum (II) in vivo and in vitro.

A monoclonal antibody, MAb62-5, was prepared and used to detect DNA damage due to the anticancer drug cis-diamminedichloroplatinum (II) (or cisplatin). ELISA competition indicated that the binding of MAb62-5 to cisplatin-DNA was competitively inhibited (50% control) by 210 nM of cisplatin bound to DNA, cisplatin/nucleotide (D/N) = 0.2. Using a DNA mobility shift assay, MAb62-5 binding activity was inhibited by 50% by approximately 50-fold molar excess of cisplatin-DNA adducts (D/N = 0.08), whereas there was less than 5% inhibition by UV-DNA adducts or mock-treated DNA. In addition, MAb62-5 showed a similar affinity to the cisplatin-DNA adducts as compared to an endogenous cisplatin-damaged DNA recognition protein. Using ELISA with this antibody, we have demonstrated a 2-fold enhancement in excision repair of cisplatin-DNA adducts in resistant HeLa cells. This is supported by the measurement of repair-associated DNA strand breaks using alkaline elution and host cell reactivation of transfected plasmid DNA carrying cisplatin damage. These findings also provide explanation for the complexicity of immunoassay in cells.