title: LNCaP produces both putative zymogen and inactive, free form of prostate-specific antigen.
abstract: BACKGROUND
  Our objective was to investigate the presence of prostate specific antigen (PSA) and alpha-1-antichymotrypsin (ACT) mRNA and protein in prostate cancer cell lines, and the complexing characteristics of expressed PSA.
  
  
  METHODS
  RT-PCR, immunohistochemistry, and Western blots were employed. Trypsin treatment of PSA was performed to establish the possible presence of an activatable form of PSA.
  
  
  RESULTS
  ACT mRNA and protein were detected in LNCaP, PC-3, and DU 145 by RT-PCR and by immunohistochemistry, respectively. Only LNCaP cells were positive for PSA mRNA and protein. LNCaP expressed approximately 30% active PSA, approximately 40% putative zymogen form of PSA, and approximately 30% stably inactive PSA.
  
  
  CONCLUSIONS
  We have shown that the majority of PSA expressed by LNCaP cells is present in free, noncomplexed forms in the conditioned media. A portion (40%) can be activated by trypsin, while the rest is stably inactive PSA. LNCaP cells may serve as a source of the "unreactive" PSA present in prostate cancer patients' serum.
authors.affiliation: Department of Urology, School of Medicine, University of Washington, Seattle 98195, USA. ecorey@u.washington.edu
authors.forename: E
authors.initials: E
authors.lastname: Corey
authors.forename: L G
authors.initials: LG
authors.lastname: Brown
authors.forename: M J
authors.initials: MJ
authors.lastname: Corey
authors.forename: K R
authors.initials: KR
authors.lastname: Buhler
authors.forename: R L
authors.initials: RL
authors.lastname: Vessella
mesh_terms: D014408:Biomarkers, Tumor / Q000032:analysis*; D015153:Blotting, Western; D017931:DNA Primers; D004792:Enzyme Precursors / Q000032:analysis*; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D010455:Peptides / Q000032:analysis*; D016133:Polymerase Chain Reaction / Q000379:methods; D017430:Prostate-Specific Antigen / Q000032:analysis* / Q000235:genetics; D011471:Prostatic Neoplasms / Q000201:enzymology* / Q000276:immunology*; D029584:Prostatic Secretory Proteins; D012333:RNA, Messenger / Q000032:analysis; D012334:RNA, Neoplasm / Q000032:analysis; D012194:RNA-Directed DNA Polymerase; D014407:Tumor Cells, Cultured; D000514:alpha 1-Antichymotrypsin / Q000032:analysis* / Q000235:genetics
chemical_list: D014408:Biomarkers, Tumor; D017931:DNA Primers; D004792:Enzyme Precursors; D010455:Peptides; D029584:Prostatic Secretory Proteins; D012333:RNA, Messenger; D012334:RNA, Neoplasm; D000514:alpha 1-Antichymotrypsin; C043076:beta-microseminoprotein; D012194:RNA-Directed DNA Polymerase; D017430:Prostate-Specific Antigen