title: Identification of a mimotope for circulating anti-cytokeratin 8/18 antibody             and its usage for the diagnosis of breast cancer.
abstract: A novel circulating tumor-associated autoantibody, K94, obtained from a hepatocellular carcinoma (HCC) mouse model was characterized. The target antigen of K94 autoantibody was expressed in various tumor cell lines including liver cancer, and its secretion was detectable using MCF-7 breast carcinoma cells. Proteomic analysis revealed that the protein bands reactive to K94 included cytokeratin (CK) 8 and 18, which are known to be related to tumorigenesis and form a heterotypic complex with each other. However, K94 showed no activity toward CK8 or CK18 separately. The epitope of the K94 antibody was only presented by a complex between CK8 and CK18, which was confirmed by analysis using recombinant CK8 and CK18 proteins. To formulate an assay for anti-CK8/18 complex autoantibody, a mimotope peptide reactive to K94 was selected from loop-constrained heptapeptide (-CX7C-) display phage library, of which sequence was CISPDAHSC (K94p1). A mimotope enzyme-linked immunosorbent assay (ELISA) using phage-displayed K94p1 peptide as a coating antigen was able to discriminate breast cancer (n=30) patients from normal subjects (n=30) with a sensitivity of 50% and a specificity of 82.61%. CA15.3 was detected at very low levels in the same breast cancer subjects and did not discriminate breast cancer patients from normal subjects, although it is a conventional biomarker of breast cancer. These results suggest that a mimotope ELISA composed of K94p1 peptide may be useful for the diagnosis of breast cancer.
authors.affiliation: Korea Research Institute of Bioscience and Biotechnology, Daejeon, Republic of Korea.
authors.forename: Chang-Kyu
authors.initials: CK
authors.lastname: Heo
authors.forename: Hai-Min
authors.initials: HM
authors.lastname: Hwang
authors.forename: Ah
authors.initials: A
authors.lastname: Ruem
authors.forename: Dae-Yeul
authors.initials: DY
authors.lastname: Yu
authors.forename: Ju Yeon
authors.initials: JY
authors.lastname: Lee
authors.forename: Jong Shin
authors.initials: JS
authors.lastname: Yoo
authors.forename: In Gyu
authors.initials: IG
authors.lastname: Kim
authors.forename: Hyang Sook
authors.initials: HS
authors.lastname: Yoo
authors.forename: Sejeong
authors.initials: S
authors.lastname: Oh
authors.forename: Jeong Heon
authors.initials: JH
authors.lastname: Ko
authors.forename: Eun-Wie
authors.initials: EW
authors.lastname: Cho
mesh_terms: D000818:Animals; D001323:Autoantibodies / Q000097:blood*; D040761:Biomimetic Materials; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000097:blood / Q000175:diagnosis* / Q000276:immunology; D018270:Carcinoma, Ductal, Breast / Q000097:blood / Q000175:diagnosis* / Q000276:immunology; D004797:Enzyme-Linked Immunosorbent Assay; D000939:Epitopes / Q000276:immunology; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D053538:Keratin-18 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000276:immunology*; D053533:Keratin-8 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000276:immunology*; D051379:Mice; D008856:Microscopy, Fluorescence; D009367:Neoplasm Staging; D019151:Peptide Library; D010456:Peptides, Cyclic / Q000276:immunology*; D012333:RNA, Messenger / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014407:Tumor Cells, Cultured
chemical_list: D001323:Autoantibodies; D000939:Epitopes; D053538:Keratin-18; D053533:Keratin-8; D019151:Peptide Library; D010456:Peptides, Cyclic; D012333:RNA, Messenger; D034741:RNA, Small Interfering