title: Spondin-2 (SPON2), a more prostate-cancer-specific diagnostic biomarker.
abstract: BACKGROUND
  Prostate-specific antigen (PSA) screening, although common, has recently been called into question. To find prostate cancer (PCa) diagnostic biomarkers that can make up for the defects of PSA, we compared the secretomes of several benign and PCa cell lines, selected candidate molecules, and then confirmed their clinical value.
  
  
  RESULTS
  We first identified extracellular proteins by two-dimensional gel electrophoresis (2-DE) coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS) identification. We then validated the secreted proteins on a cellular level, and finally determined whether they could be used as PCa diagnostic biomarkers using prostate tissue and serum specimens of Chinese volunteers by immunohistostaining and sandwich ELISA. We obtained credible extracellular protein 2-DE graphs of prostate cell lines. The 5 spots that showed superior repeatability were selected for LC-MS/MS analysis, which identified seven candidate molecules. One of the candidate molecules, spondin-2 (SPON2), was only expressed in the conditioned media (CM) of androgen receptor (AR) positive PCa cell lines. Using tissue microarray by immunohistostaining, we found SPON2 to be over-expressed in PCa. SPON2 staining was more intense in Gleason score sum 7-8 and in PCa patients with metastasis. By receiver operator characteristic (ROC) curve analysis, we found that the serum SPON2 level was elevated in PCa patients, showing sensitivity and specificity suitable for diagnostic use. We also found that SPON2 could be used to identify PCa patients with serum PSA levels no higher than 10 ng/ml from healthy elderly men.
  
  
  CONCLUSIONS
  SPON2 is a new serum and histological diagnostic biomarker for PCa. It can avoid some of the problems of PSA testing and was here found to offer relatively high sensitivity and specificity relative to PSA.
authors.affiliation: Department of Medical Molecular Biology, Beijing Institute of Biotechnology, Beijing, P. R. China.
authors.forename: Xiaolong
authors.initials: X
authors.lastname: Qian
authors.forename: Changling
authors.initials: C
authors.lastname: Li
authors.forename: Bo
authors.initials: B
authors.lastname: Pang
authors.forename: Meng
authors.initials: M
authors.lastname: Xue
authors.forename: Jian
authors.initials: J
authors.lastname: Wang
authors.forename: Jianguang
authors.initials: J
authors.lastname: Zhou
mesh_terms: D014408:Biomarkers, Tumor / Q000097:blood*; D002460:Cell Line; D017077:Culture Media, Conditioned / Q000032:analysis; D016326:Extracellular Matrix Proteins / Q000097:blood*; D006367:HeLa Cells; D006801:Humans; D008297:Male; D009363:Neoplasm Proteins / Q000097:blood*; D011467:Prostate / Q000737:chemistry*; D017430:Prostate-Specific Antigen / Q000032:analysis; D011471:Prostatic Neoplasms / Q000097:blood*; D012680:Sensitivity and Specificity
chemical_list: D014408:Biomarkers, Tumor; D017077:Culture Media, Conditioned; D016326:Extracellular Matrix Proteins; D009363:Neoplasm Proteins; C122166:SPON2 protein, human; D017430:Prostate-Specific Antigen