Identification of tumor antigens that elicit a humoral immune response in breast cancer patients' sera by serological proteome analysis (SERPA)

In this study we applied a serological proteomics-based approach (SERPA) to identify tumor antigens that commonly induce a humoral immune response in patients with infiltrating ductal breast carcinomas. Sera obtained at the time of diagnosis from 40 patients with invasive breast cancer and 42 healthy controls were screened individually for the presence of IgG antibodies to MCF-7 cell line proteins. Immunoreactive proteins were isolated and subsequently identified by MALDI-TOF mass spectrometry. We identified 26 proteins that reacted with antibodies in the sera from breast cancer patients. Among these antigens, a significantly higher frequency occurs against the molecular chaperone HSP60, the tumor suppressor prohibitin, β-tubulin, the haptoglobin-related protein and peroxiredoxin-2. Immunoreactivity to hnRNPK, Mn-SOD and F1-ATPase was also clearly detected in the patients group, whereas scarcely in control sera. By contrast, two other antigens identified as cytokeratins 8 and 18, as well as, F1-actin were found to elicit humoral immune responses in both control and breast cancer patients' sera. The immunoproteomic approach implemented here offers a powerful tool for determining novel tumor antigens that elicit a humoral immune response in patients with invasive breast cancer. These antigens and/or their related circulating antibodies may display clinical usefulness as potential diagnostic markers and provide a means for a better understanding of the molecular mechanisms underlying breast cancer development.