earticle

영어

In many cases of cancers, aberrantly expressed or modified tumor-associated antigens leads to the formation of tumor-associated autoantibodies. Recent studies have demonstrated that autoantibodies are appropriate to serve as biomarkers for the early detection of cancers, if autoantibodies and their target antigens are well characterized. In previous studies, we established a B cell hybridoma pool derived from hepatitis B virus X (HBx) transgenic mouse, a hepatocellular carcinoma model mouse, and characterized autoantibodies from B cell hybridoma and their specific target antigens using purified autoantibodies. In this study, XE278 autoantibody, one of them, was purified and characterized. Flow cytometric analysis revealed that target antigen of XE278 autoantibody is highly expressed in various cancer cell lines as compared to normal ones, especially in breast cancer cell lines. Its target antigen, with molecular weight of 55 kDa, was identified by immunoprecipitation and MS-based proteomic methods as cytokeratin 8 (CK8), an intermediate filament protein which is expressed in epithelial and carcinoma cells and correlated with increased invasiveness of tumor. Moreover, two specific mimotopes (XE278-p1 and XE278-p2) against XE278 autoantibody were screened from the cyclic random hepta-peptide phage libraries, which can be used as baits for capturing target autoantibodies. Using XE278-p2-display M13 phage as coating antigen in enzyme-linked immunosorbent assay (ELISA), we could distinguish breast cancer patients from normal subjects. Furthermore, the combination assay using XE278-p2 and K94-p1, another specific mimotope against K94 autoantibody which targets CK8/18 complex, improved the specificity and sensitivity of diagnosis to discriminate cancer patients from normal ones. These results indicate that anti-CK8 autoantibody is induced in breast cancer patients and the detection of anti-CK8 autoantibody can be used for the diagnosis of breast cancer.