title: Expression of RCAS1 in esophageal squamous cell carcinoma is associated with a poor prognosis.
abstract: BACKGROUND
  Receptor-binding cancer antigen expressed on SiSO cells (RCAS1) has been reported to act as a ligand for a receptor present on normal peripheral lymphocytes and to induce apoptotic cell death. We aimed to elucidate the significance of RCAS1 expression in human esophageal squamous cell carcinomas (ESCC).
  
  
  METHODS
  RCAS1 expression was examined immunohistochemically in surgically resected esophageal carcinoma tissues from 114 patients. We also examined the relationships between RCAS1 expressions, the tumor Ki-67 indices (a marker of proliferation), and the number of CD8+ tumor-infiltrating lymphocytes (TILs).
  
  
  RESULTS
  RCAS1 immunoreactivity was detected in the membranes and cytoplasm of the tumor cells. Of the 114 esophageal carcinomas, 39 (34.2%) were strongly positive for RCAS1 immunostaining on the membranes of the cancer cells, 41 (36.0%) were weakly positive, and 34 (29.8%) were negative. A comparison of RCAS1 expression and clinicopathological characteristics in all 114 patients revealed significant associations between RCAS1 expression and lymph node status (P < 0.05), and pathologic stage (P < 0.05). The survival rates of patients with RCAS1-negative tumors were significantly higher than those of patients with both RCAS1-weak positive tumors and RCAS1-strong positive ones (log-rank P < 0.05). Multivariate analysis revealed that RCAS1 positivity was an independent prognostic factor (P < 0.05). The relationship between RCAS1 expression and the numbers of CD8+ T-cells in the primary tumors revealed that RCAS1-negative tumors tended to contain more of these cells than both RCAS1-weak positive tumors and RCAS1-strong positive ones (P = 0.2495).
  
  
  CONCLUSIONS
  RCAS1 may play a significant role in tumor progression via an immune escape mechanism; thus, RCAS1 expression could be used as a predictor of poor prognosis in patients with ESCC.
authors.affiliation: Department of General Surgical Science (Surgery I), Gunma University, Graduate School of Medicine, Maebashi, Gunma, Japan. hiroyuki@po.wind.ne.jp
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Kato
authors.forename: Masanobu
authors.initials: M
authors.lastname: Nakajima
authors.forename: Norihiro
authors.initials: N
authors.lastname: Masuda
authors.forename: Ahmad
authors.initials: A
authors.lastname: Faried
authors.forename: Makoto
authors.initials: M
authors.lastname: Sohda
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Fukai
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Miyazaki
authors.forename: Minoru
authors.initials: M
authors.lastname: Fukuchi
authors.forename: Katsuhiko
authors.initials: K
authors.lastname: Tsukada
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Kuwano
mesh_terms: D000328:Adult; D000368:Aged; D000951:Antigens, Neoplasm / Q000032:analysis / Q000096:biosynthesis*; D016827:CD8 Antigens / Q000276:immunology; D002294:Carcinoma, Squamous Cell / Q000378:metabolism* / Q000401:mortality / Q000556:secondary / Q000601:surgery; D004938:Esophageal Neoplasms / Q000378:metabolism* / Q000401:mortality / Q000473:pathology / Q000601:surgery; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D019394:Ki-67 Antigen / Q000276:immunology; D008207:Lymphatic Metastasis; D016246:Lymphocytes, Tumor-Infiltrating / Q000276:immunology; D008297:Male; D008875:Middle Aged; D009361:Neoplasm Invasiveness; D011379:Prognosis; D016016:Proportional Hazards Models; D015996:Survival Rate
chemical_list: D000951:Antigens, Neoplasm; D016827:CD8 Antigens; C120762:EBAG9 protein, human; D019394:Ki-67 Antigen