title: Mucin 21 in esophageal squamous epithelia and carcinomas: analysis with glycoform-specific monoclonal antibodies.
abstract: Monoclonal antibodies (mAbs) against mucin 21 (MUC21), a human counterpart of mouse epiglycanin/Muc21, were prepared using human embryonic kidney 293 cells transfected with MUC21 as the immunogen. The specificity of these mAbs was examined by flow cytometry, immunoprecipitation and western blotting focusing on the differential glycosylation of MUC21 expressed in variant Chinese hamster ovary (CHO) cells (ldlD cells and Lec2 cells) and CHO-K1 cells. One of these mAbs, heM21D, bound to both the unmodified core polypeptide of MUC21 and MUC21 attached with N-acetylgalactosamine (Tn-MUC21). Six antibodies, including mAb heM21C, bound to MUC21 with Tn, T or sialyl-T epitopes but not the unmodified core polypeptide of MUC21. Esophageal squamous carcinomas and adjacent squamous epithelia were immunohistochemically examined for the binding of these mAbs. MUC21 was expressed in esophageal squamous epithelial cells, and its O-glycan extended forms were observed in the luminal portions of squamous epithelia. As revealed by the binding of mAb heM21D and the absence of reactivity with mAb heM21C, esophageal squamous carcinoma cells produce MUC21 without the attachment of O-glycans. This is the first report to show that there is a change in the glycoform of MUC21 that can be used to differentiate between squamous epithelia and squamous carcinoma of the esophagus. Thus, these antibodies represent a useful tool to characterize squamous epithelial differentiation and carcinogenesis.
authors.affiliation: Laboratory of Cancer Biology and Molecular Immunology, Graduate School of Pharmaceutical Sciences,  The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033,  Japan.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Tian
authors.forename: Kaori
authors.initials: K
authors.lastname: Denda-Nagai
authors.forename: Mika
authors.initials: M
authors.lastname: Kamata-Sakurai
authors.forename: Shoji
authors.initials: S
authors.lastname: Nakamori
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Tsukui
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Itoh
authors.forename: Kyoko
authors.initials: K
authors.lastname: Okada
authors.forename: Yuri
authors.initials: Y
authors.lastname: Yi
authors.forename: Tatsuro
authors.initials: T
authors.lastname: Irimura
mesh_terms: D000116:Acetylgalactosamine / Q000737:chemistry; D000818:Animals; D000911:Antibodies, Monoclonal / Q000096:biosynthesis / Q000276:immunology; D016466:CHO Cells; D002240:Carbohydrate Sequence; D002294:Carcinoma, Squamous Cell / Q000175:diagnosis* / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D006224:Cricetinae; D004847:Epithelial Cells / Q000737:chemistry / Q000166:cytology; D000939:Epitopes / Q000032:analysis* / Q000276:immunology; D004938:Esophageal Neoplasms / Q000175:diagnosis* / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D004947:Esophagus / Q000737:chemistry / Q000166:cytology; D005434:Flow Cytometry; D015870:Gene Expression; D006031:Glycosylation; D057809:HEK293 Cells; D006801:Humans; D008562:Membrane Glycoproteins / Q000737:chemistry* / Q000235:genetics / Q000276:immunology; D008969:Molecular Sequence Data; D009077:Mucins / Q000737:chemistry* / Q000235:genetics / Q000276:immunology; D014162:Transfection
chemical_list: D000911:Antibodies, Monoclonal; D000939:Epitopes; C527666:MUC21 protein, human; D008562:Membrane Glycoproteins; D009077:Mucins; D000116:Acetylgalactosamine