title: The utility of serum receptor-binding cancer antigen expressed on SiSo cells in gastrointestinal tract cancers.
abstract: BACKGROUND
  Receptor-binding cancer antigen expressed on SiSo cells (RCAS1) is a novel tumour marker that has been described in various kinds of cancer. The majority of observations include immunohistochemical studies; however, there are not enough data about the utility of this antigen as a serum tumour marker and its tumour specificity.
  
  
  OBJECTIVE
  To measure the serum levels of RCAS1 in patients with gastrointestinal (GI) tract cancers and compare them with other GI tract tumour markers.
  
  
  METHODS
  Sera collected from patients with GI cancers (14 esophagus, 32 gastric and 36 colon) and from healthy volunteers (30 individuals) were analyzed for RCAS1 and compared with carcinoembryonic antigen (CEA) and cancer antigen 19-9. The relationship between serum RCAS1, tumour stage and tumour grade was also evaluated.
  
  
  RESULTS
  Mean serum RCAS1 level was higher in patients with GI tract cancers compared with the control group (P=0.001). Among GI tract cancers, RCAS1 had lowest and highest sensitivity for esophagus and colon cancer diagnosis, respectively. Serum RCAS1 had a higher sensitivity for malignancy, except in the colon, and lower specificity in all groups compared with CEA. In comparison with cancer antigen 19-9, serum RCAS1 was more sensitive but less specific for all GI cancer groups. Mean serum RCAS1 levels were not statistically significant among histopathological tumour types (P>0.05). Although serum RCAS1 levels were significantly higher in cases with lymph node involvement compared with lymph node-negative cases (P=0.009), there was no difference between cases with and without serosal involvement, vascular invasion and distant metastasis; no correlation was found between tumour size and RCAS1 levels.
  
  
  CONCLUSIONS
  RCAS1 may be used and combined with CEA as a tumour marker in GI tract cancers.
authors.affiliation: Department of Gastroenterology, Ankara University Medical School, Ankara Education and Research Hospital, Turkey. scoban72@yahoo.com
authors.forename: Sahin
authors.initials: S
authors.lastname: Coban
authors.forename: Hasan
authors.initials: H
authors.lastname: Ozkan
authors.forename: Seyfettin
authors.initials: S
authors.lastname: Köklü
authors.forename: Osman
authors.initials: O
authors.lastname: Yüksel
authors.forename: Muhammed Cem
authors.initials: MC
authors.lastname: Koçkar
authors.forename: Tarik
authors.initials: T
authors.lastname: Akar
authors.forename: Necati
authors.initials: N
authors.lastname: Ormeci
mesh_terms: D000230:Adenocarcinoma / Q000276:immunology; D000328:Adult; D000368:Aged; D000951:Antigens, Neoplasm / Q000097:blood*; D014408:Biomarkers, Tumor / Q000097:blood*; D018395:CA-19-9 Antigen / Q000097:blood; D002272:Carcinoembryonic Antigen / Q000097:blood; D002294:Carcinoma, Squamous Cell / Q000276:immunology; D016022:Case-Control Studies; D003110:Colonic Neoplasms / Q000276:immunology; D004938:Esophageal Neoplasms / Q000276:immunology; D005260:Female; D005770:Gastrointestinal Neoplasms / Q000276:immunology* / Q000473:pathology; D006801:Humans; D008207:Lymphatic Metastasis; D008297:Male; D008875:Middle Aged; D009361:Neoplasm Invasiveness; D009367:Neoplasm Staging; D011237:Predictive Value of Tests; D012680:Sensitivity and Specificity; D013274:Stomach Neoplasms / Q000276:immunology
chemical_list: D000951:Antigens, Neoplasm; D014408:Biomarkers, Tumor; D018395:CA-19-9 Antigen; D002272:Carcinoembryonic Antigen; C120762:EBAG9 protein, human