title: Identification of ROBO1 as a novel hepatocellular carcinoma antigen and a potential therapeutic and diagnostic target.
abstract: OBJECTIVE
  Hepatocellular carcinoma is the most common primary malignancy of the liver and accounts for as many as one million deaths annually worldwide. The present study was done to identify new transmembrane molecules for antibody therapy in hepatocellular carcinoma.
  
  
  METHODS
  Gene expression profiles of pooled total RNA from three tissues each of moderately differentiated and poorly differentiated hepatocellular carcinoma were compared with those of normal liver, noncancerous liver tissue in hepatocellular carcinoma patients, 30 normal tissue samples, and five fetal tissue samples. Target genes up-regulated specifically in hepatocellular carcinoma were validated by immunohistochemical analysis and complement-dependent cytotoxicity assay using monoclonal antibodies generated against target molecules.
  
  
  RESULTS
  The human homologue of the Drosophila Roundabout gene, axon guidance receptor homologue 1, ROBO1/DUTT1, a member of the immunoglobulin superfamily, was highly expressed in hepatocellular carcinoma, whereas it showed only a limited distribution in normal tissues. On immunohistochemical analysis using a newly generated anti-ROBO1 monoclonal antibody, positive signals were observed in 83 of 98 cases of hepatocellular carcinoma (84.7%). The mAb B2318C induced complement-dependent cytotoxicity in ROBO1-expressing cell lines and in the liver cancer cell line PLC/PRF/5. Strikingly, the ectodomain of ROBO1 was detected not only in the culture medium of liver cancer cell lines (PLC/PRF/5, HepG2, etc.) but also in sera from hepatocellular carcinoma patients (6 of 11).
  
  
  CONCLUSIONS
  This is the first report that ROBO1 is overexpressed in hepatocellular carcinoma and shed into serum in humans. These observations suggest that ROBO1 is a potential new serologic marker for hepatocellular carcinoma and may represent a new therapeutic target.
authors.affiliation: Genome Science Division, Research Center for Advanced Science and Technology, the University of Tokyo, Japan.
authors.forename: Hirotaka
authors.initials: H
authors.lastname: Ito
authors.forename: Shin-ichi
authors.initials: S
authors.lastname: Funahashi
authors.forename: Naoko
authors.initials: N
authors.lastname: Yamauchi
authors.forename: Junji
authors.initials: J
authors.lastname: Shibahara
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Midorikawa
authors.forename: Shigeto
authors.initials: S
authors.lastname: Kawai
authors.forename: Yasuko
authors.initials: Y
authors.lastname: Kinoshita
authors.forename: Akira
authors.initials: A
authors.lastname: Watanabe
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Hippo
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Ohtomo
authors.forename: Hiroko
authors.initials: H
authors.lastname: Iwanari
authors.forename: Atsushi
authors.initials: A
authors.lastname: Nakajima
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Makuuchi
authors.forename: Masashi
authors.initials: M
authors.lastname: Fukayama
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Hirata
authors.forename: Takao
authors.initials: T
authors.lastname: Hamakubo
authors.forename: Tatsuhiko
authors.initials: T
authors.lastname: Kodama
authors.forename: Masayuki
authors.initials: M
authors.lastname: Tsuchiya
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Aburatani
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D014408:Biomarkers, Tumor / Q000096:biosynthesis / Q000097:blood / Q000235:genetics; D019556:COS Cells; D006528:Carcinoma, Hepatocellular / Q000097:blood / Q000175:diagnosis / Q000235:genetics*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002522:Chlorocebus aethiops; D003601:Cytotoxicity Tests, Immunologic; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007150:Immunohistochemistry; D008113:Liver Neoplasms / Q000097:blood / Q000175:diagnosis / Q000235:genetics*; D009419:Nerve Tissue Proteins / Q000096:biosynthesis / Q000097:blood / Q000235:genetics*; D017434:Protein Structure, Tertiary; D012333:RNA, Messenger / Q000096:biosynthesis; D011971:Receptors, Immunologic / Q000096:biosynthesis / Q000097:blood / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D015854:Up-Regulation / Q000235:genetics; D000097905:Roundabout Proteins
chemical_list: D000911:Antibodies, Monoclonal; D014408:Biomarkers, Tumor; D009419:Nerve Tissue Proteins; D012333:RNA, Messenger; D011971:Receptors, Immunologic; D000097905:Roundabout Proteins