Characterization of chromatin modified with reactive oxygen species: Recognition by autoantibodies in cancer

Objectives To study the binding of chromatin modified with reactive oxygen species (ROS) with circulating autoantibodies present in cancer patients. Design and methods Chromatin isolated from goat liver was modified by superoxide radical plus singlet oxygen and hydroxyl radicals. Sera from 47 patients with various types of cancers were tested for binding to native and modified chromatin by direct binding and competition ELISA. Results Maximum modification of thymine (54%) was found in case of chromatin modified with hydroxyl radical whereas by the combined action of singlet oxygen and superoxide anion radical, guanine was modified most (72%). Autoantibodies in cancer sera recognized modified chromatin in preference to native chromatin. Band shift assay with affinity-purified IgG from sera of cancer patients reiterated the results obtained with serum samples. Conclusion Greater recognition of ROS-modified chromatin with the autoantibodies in cancer sera is indicative of reactive-oxygen-species-induced chromatin damage in cancer patients.