title: Expression of a tumor-associated antigen, RCAS1, in canine mammary tumors.
abstract: Receptor-binding cancer antigen expressed on SiSo cells (RCAS1), one of novel cancer cell-surface antigens, is strongly expressed in invasive cancers. RCAS1 inhibits the in vitro growth of lymphocytes such as T cells and natural killer (NK) cells, and induces apoptotic cell death. We investigated the expression of RCAS1 in canine mammary tumor cell lines and tumor cells by immunohistochemistry, and also in situ deoxyribonucleic acid (DNA) fragmentation in tumor-infiltrating lymphocytes (TILs) by the terminal deoxynucleotidyl transferase mediated deoxyuridine triphosphate nick end labeling (TUNEL) method. All canine mammary tumor cell lines expressed RCAS1 at both the messenger ribonucleic acid (mRNA) and protein level. Immunohistochemically, RCAS1 was negative in 100% of normal mammary glands, but was expressed in 100% of malignant tumors examined. In most malignant mammary tumors, RCAS1 was localized in the cytoplasm with no polarity of expression. In benign mammary tumors, it was detected on the luminal surface of the tumor cell. RCAS1 expression or localization was significantly correlated with malignancy. In situ DNA fragmentation of CD3-positive TILs was observed in RCAS1-expressing tumors. RCAS1-expressing tumors, indicating a possible induction of apoptotic cell death in TILs through RCAS1 expression. These observations suggest that RCAS1 probably plays an important role in tumor progression and escape from immune surveillance in canine mammary tumors.
authors.affiliation: Department of Veterinary Surgery, Faculty of Agriculture, Yamaguchi University, Japan.
authors.forename: Yasuhiko
authors.initials: Y
authors.lastname: Okamura
authors.forename: Tomoya
authors.initials: T
authors.lastname: Haraguchi
authors.forename: Masahiro
authors.initials: M
authors.lastname: Morimoto
authors.forename: Masaru
authors.initials: M
authors.lastname: Okuda
authors.forename: Satoshi
authors.initials: S
authors.lastname: Une
authors.forename: Munekazu
authors.initials: M
authors.lastname: Nakaichi
authors.forename: Yasuho
authors.initials: Y
authors.lastname: Taura
mesh_terms: D000818:Animals; D000951:Antigens, Neoplasm / Q000235:genetics*; D017209:Apoptosis; D017252:CD3 Complex; D016764:Cell Polarity; D017931:DNA Primers / Q000737:chemistry; D004285:Dogs; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007150:Immunohistochemistry / Q000662:veterinary; D007157:Immunologic Surveillance; D020287:In Situ Nick-End Labeling / Q000662:veterinary; D016246:Lymphocytes, Tumor-Infiltrating / Q000473:pathology; D015674:Mammary Neoplasms, Animal / Q000235:genetics* / Q000473:pathology; D008856:Microscopy, Fluorescence / Q000662:veterinary; D012333:RNA, Messenger / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000662:veterinary; D013601:T-Lymphocytes / Q000473:pathology; D014407:Tumor Cells, Cultured
chemical_list: D000951:Antigens, Neoplasm; D017252:CD3 Complex; D017931:DNA Primers; C120762:EBAG9 protein, human; D012333:RNA, Messenger