Hydroxyl Radical Damaged Thymidine-5'-Monophophate Presents Unique Epitopes for Cancer Antibodies

Reactive oxygen species (ROS) plays an important role in carcinogenesis and hydroxyl radical ( . OH) contrib- utes to the structural changes in DNA that characterize the cancer like phenotype. The role of hydroxyl radical ( . OH) dam- aged thymidine 5'-monophosphate (TMP) in cancer patients has been investigated in the present study. TMP was conju- gated to bovine serum albumin (BSA), and then TMP-BSA conjugate was modified by hydroxyl radicals. Cancer patients (n = 99) were screened by direct binding ELISA for the detection of antibodies against native and ROS-modified conju- gates and the results were compared with healthy age-matched controls (n = 29). High degree of specific binding by can- cer serum antibodies towards ROS modified TMP-BSA conjugate, in comparison to unmodified conjugate (p<0.05) was observed. Healthy individuals showed negligible binding with either antigen. Competitive inhibition ELISA reiterates the direct binding results. Protein-A affinity purified IgG from cancer patients further substantiated the enhanced recognition towards modified conjugate as compared to unmodified conjugate. The present study clearly shows the perturbation in TMP-BSA conjugate by hydroxyl radical presenting unique neo-epitopes on TMP that might from one of the factors in antigen driven induction of antibodies in cancer patients.