Peroxynitrite modified DNA may be an antigenic trigger for antibodies in various cancers of gynecologic origin

This study aimed towards probing the role of peroxynitrite damaged human DNA (ONOO^–-DNA) in the induction of circulating antibodies in certain cancers of gynecologic origin. We have compared the binding specificity of DNA isolated from the lymphocytes of cancer patients with that of the experimentally modified DNA. Also, the induced anti-ONOO⁻-DNA antibodies have been used to probe oxidative damage in the DNA isolated from cancer patients. Human placental DNA was modified with peroxynitrite (ONOO⁻) and analyzed by ultraviolet (UV) and fluorescence spectroscopy, gel electrophoresis, thermal denaturation profile, etc. Antibodies against modified DNA were induced in experimental animals. Specific binding of the antibodies was evaluated by ELISA and band shift assay. 91 cancer patients were selected and grouped according to the type of cancer. Specific binding characteristics of circulating autoantibodies (IgG) were determined by competitive-inhibition ELISA, using different inhibitors. Maximum inhibition of antibody activity by ONOO⁻-DNA reflected specific recognition of modified epitopes by cancer IgG. This shows generation of neo-epitopes on DNA, upon modification with ONOO⁻, that are recognized by cancer IgG. Our results indicate epitope sharing between the DNA isolated from cancer patients and the in-vitro modified ONOO⁻-DNA. The possible role of nitrosative stress in the gynecologic oncology has been discussed.