Autoantibody to tumor antigen, alpha 2-HS glycoprotein: A novel biomarker of breast cancer
Authors: Jae Kyo Yi, Jong Wook Chang, Wonshik Han, Jong Won Lee, Myeong-Hee Yu, Dong-Young Noh
Journal: Clinical Cancer Research (2008)

B9    Introduction:  The identification of tumor antigens that elicit antibody responses may have an advance in cancer screening, diagnosis, and establishing prognosis. Up to the present, autoimmunity in breast cancer has mainly been investigated with general, limited sources of tumor antigens. Using urinary proteins as new sources of potential tumor antigens, we sought to identify a serum biomarker for breast cancer screening and diagnosis. Immunoreactivity of sera from the breast cancer patients and healthy donors was analyzed to detect the presence of cancer-specific autoantibodies.   Methods:  Two-dimensional electrophoresis (2DE) was performed for screening autoimmunogenic tumor antigens in the urine of breast cancer patients. The separated proteins were incubated with pooled sera from the breast cancer patients and the healthy donors. Differentially reactive spots were identified by MALDI-TOF/TOF. Alpha2-HS glycoprotein was selected among the candidates of the reactive spots due to showing the strongest different reactivity. Independent test sets of peripheral blood were obtained from 81 women diagnosed with breast cancer before surgery and 73 female donors without evidence of any malignancy. The expression of specific serum autoantibody was analyzed using Western blot.   Results:  By 2DE and 2D-immunoblotting, we detected thirteen candidate spots which show strong reactivity with pooled sera from breast cancer patients or control sera. The thirteen spots were identified by MALDI-TOF/TOF mass spectrometry. Among them, 3 spots were identified as the same protein, alpha 2-HS glycoprotein (AHSG). To confirm whether breast cancer patient sera contained autoantibody to AHSG, purified AHSG was probed with pooled sera from 10 healthy controls or 10 breast cancer patients. We found that the combined patient sera used above was able to detect as little as 125 ng of AHSG whereas the control sera could not detect even 1 μg of the protein by Western blot analysis. In individual Western blot analysis, AHSG autoantibody was detected in 64 out of 81 breast cancer patients (79.1%), and in seven out of 73 controls (9.6%). The sensitivity of this test in breast cancer patients was 79.0%. Specificity, accuracy, and positive predictive value were 90.4%, 84.4%, and 90.1%, respectively.   Conclusion:  Our findings indicate that AHSG in breast cancer induces a humoral immune response and suggest that its autoantibody can be a potential biomarker for clinical serological screening of breast cancer.      References  1) Caron M, Choquet-Kastylevsky G, Joubert-Caron R. Cancer immunomics using autoantibody signatures for biomarker discovery. Mol Cell Proteomics 2007;6:1115-22.  2) Hu S, Loo JA, Wong DT. Human body fluid proteome analysis. Proteomics 2006;6: 6326-53.     Grant support: This work was supported by a grant from the Functional Proteomics Research Center of the 21st Century Frontier Research Program funded by the Korean Ministry of Science and Technology, Republic of Korea (FPR05C3 - 100).