title: GAD1 is a biomarker for benign and malignant prostatic tissue.
abstract: OBJECTIVE
  Tissue-specific markers are useful for identification of tumour type in advanced cancers of unknown origin. This study investigated the expression of glutamate decarboxylase 1 (GAD1) in prostate and control tissue compared with the established prostate-specific markers prostate-specific antigen (PSA) and prostate-specific membrane antigen (PSMA).
  
  
  METHODS
  A tissue microarray was constructed of 36 prostate adenocarcinomas, eight benign prostate samples and benign and malignant control tissues from urinary bladder, lung and rectum. Immunohistochemistry for GAD1, PSA and PSMA was performed. The products of staining intensity and extent were analysed. The GAD1 antibody was validated by Western blot. Real-time polymerase chain reaction (RT-PCR) was performed on malignant and benign samples from each tissue type.
  
  
  RESULTS
  GAD1 and PSA immunostains were significantly stronger in malignant and benign prostatic tissue than in controls. PSMA was stronger in prostate cancer than in urothelial and rectal cancer but had a lower specificity than GAD1 and PSA. GAD1 expression decreased with increasing Gleason score. RT-PCR confirmed the presence of mRNA for GAD1, PSA and PSMA in prostate samples.
  
  
  CONCLUSIONS
  GAD1 is expressed in benign and malignant prostatic tissue and may serve as a highly prostate-specific tissue biomarker.
authors.affiliation: Department of Oncology and Pathology, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Sara Jonmarker
authors.initials: SJ
authors.lastname: Jaraj
authors.forename: Martin
authors.initials: M
authors.lastname: Augsten
authors.forename: Lars
authors.initials: L
authors.lastname: Häggarth
authors.forename: Kenneth
authors.initials: K
authors.lastname: Wester
authors.forename: Fredrik
authors.initials: F
authors.lastname: Pontén
authors.forename: Arne
authors.initials: A
authors.lastname: Ostman
authors.forename: Lars
authors.initials: L
authors.lastname: Egevad
mesh_terms: D000368:Aged; D000954:Antigens, Surface / Q000378:metabolism; D015415:Biomarkers / Q000378:metabolism; D014408:Biomarkers, Tumor / Q000378:metabolism*; D001706:Biopsy; D016022:Case-Control Studies; D043425:Glutamate Carboxypeptidase II / Q000378:metabolism; D005968:Glutamate Decarboxylase / Q000378:metabolism*; D006801:Humans; D008168:Lung / Q000378:metabolism / Q000473:pathology; D008297:Male; D008875:Middle Aged; D011467:Prostate / Q000378:metabolism* / Q000473:pathology; D017430:Prostate-Specific Antigen / Q000378:metabolism; D011471:Prostatic Neoplasms / Q000378:metabolism* / Q000473:pathology; D012007:Rectum / Q000378:metabolism / Q000473:pathology; D012680:Sensitivity and Specificity; D001743:Urinary Bladder / Q000378:metabolism / Q000473:pathology
chemical_list: D000954:Antigens, Surface; D015415:Biomarkers; D014408:Biomarkers, Tumor; C473848:FOLH1 protein, human; D043425:Glutamate Carboxypeptidase II; D017430:Prostate-Specific Antigen; D005968:Glutamate Decarboxylase; C402565:glutamate decarboxylase 1