P1-01-16: Detecting a Breast Carcinoma-Deriving B-Cell Response: An Immunoproteomics Biomarker Approach.
Authors: Keller K , Boehm DU , Grus FH , Koelbl H 
Published: June 2012

Background: Noninvasive biomarkers for the early detection of breast cancer are crucial due to the fact that the relapse risk of breast cancer is rising with the time point of its detection. Currently, none of the reported molecular biomarkers is established for the clinical use as a diagnostic tool. Previous proteomics-based studies showed the immunogenicity of breast carcinoma and the following B-cell mediated immune response. As a result, several autoantibodies against tumor proteins were detected in the sera of breast cancer patients. However, these putative biomarkers are still lacking of clinically reliable specificity and sensitivity, even of better discrimination of cancer patients when combining different biomarkers. The search for a new antibody biomarker signature remains very important as a potential cancer detection tool. For further investigations we analyzed the antibody pattern in serum samples of diseased patients and healthy controls after incubation with whole protein extract from a native carcinoma and identified the putative tumor-specific immunoreactive antigens.

Materials and methods: For our de novo profiling of tumor antigens we used a protein extract from a primary invasive ductal carcinoma. Sera from 20 women, of which 19 were diagnosed with breast carcinoma and one with DCIS (CA), and 20 sera from age-matched healthy donors (CTRL) were obtained and pooled separately. For an optimal separation of tumor antigens a two-dimensional sodium dodecylsulfate gel electrophoresis (2D SDS-PAGE) was applied. Following immunoblots with each serum pool were performed and the immunospecific reactions visualized with a horseradish peroxidase-conjugated anti-IgG antibody. The relevant tumor antigens were identified via Matrix-Assisted Laser Desorption Ionization Time of Flight Mass Spectrometry (MALDI TOF-TOF MS).

Results: After the incubation of each serum pool with tumor antigens we obtained different extensive antibody profiles, whereas the visualized immunoreactive components varied in the signal intensity. We identified over 10 tumor antigens which reacted with the corresponding autoantibodies in CA or CTRL approach, showing again the complexity of immune response. Besides of already described breast carcinoma related antigens like alpha enolase, which showed immune reaction also with the healthy serum pool, we identified several potential antigens of interest like peroxiredoxin 6 which showed a strong immune response only after the incubation with cancer sera.

Discussion: In our study we visualized a complex immune response pattern showing the autoantibody profiles in cancer and healthy sera against tumor-deriving antigens. Also some of identified breast carcinoma antigens were already described; other novel breast carcinoma-related antigens were detected too. Our next step in the intriguing search for cancer antibody biomarkers is the individual screening of sera to confirm the specificity of the tumor-deriving B-cell responses and the validation of these results by using an independent study population.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P1-01-16.