Preferential recognition of peroxynitrite-modified human serum albumin by circulating autoantibodies in cancer.

Peroxynitrite is a potent oxidizing and nitrating agent and has in vivo existence. Several studies have shown the damaging role of this molecule in biological system. Human serum albumin (HSA), being most abundant plasma protein, is easily targeted by different oxidizing and nitrating agents. Free radicals increase the onset of different cancers as evident by several researchers. In the present study, structural perturbations in HSA by peroxynitrite were observed by MALDI-MS, DSC and DLS. Immunological studies showed enhanced binding of peroxynitrite-modified HSA with cancer autoantibodies, compared to the native protein. A decline in the antioxidant property of peroxynitrite-modified HSA was also observed. Therefore, we may conclude that peroxynitrite exposure results in structural alteration and hence generation of neo-epitopes in HSA molecule along with the decrease in its antioxidant property. The possible role of peroxynitrite-modified HSA in carcinogenesis has been discussed.