title: Eight-plex iTRAQ analysis of variant metastatic human prostate cancer cells identifies candidate biomarkers of progression: An exploratory study.
abstract: BACKGROUND
  Due to the heterogeneity in the biological behavior of prostate cancer, biomarkers that can reliably distinguish indolent from aggressive disease are urgently needed to inform treatment choices.
  
  
  METHODS
  We employed 8-plex isobaric Tags for Relative and Absolute Quantitation (iTRAQ), to profile the proteomes of two distinct panels of isogenic prostate cancer cells with varying growth and metastatic potentials, in order to identify novel biomarkers associated with progression. The LNCaP, LNCaP-Pro5, and LNCaP-LN3 panel of cells represent a model of androgen-responsive prostate cancer, while the PC-3, PC-3M, and PC-3M-LN4 panel represent a model of androgen-insensitive disease.
  
  
  RESULTS
  Of the 245 unique proteins identified and quantified (>or=95% confidence; >or=2 peptides/protein), 17 showed significant differential expression (>or=+/-1.5), in at least one of the variant LNCaP cells relative to parental cells. Similarly, comparisons within the PC-3 panel identified 45 proteins to show significant differential expression in at least one of the variant PC-3 cells compared with parental cells. Differential expression of selected candidates was verified by Western blotting or immunocytochemistry, and corresponding mRNA expression was determined by quantitative real-time PCR (qRT-PCR). Immunostaining of prostate tissue microarrays for ERp5, one of the candidates identified, showed a significant higher immunoexpression in pre-malignant lesions compared with non-malignant epithelium (P < 0.0001, Mann-Whitney U-test), and in high Gleason grade (4-5) versus low grade (2-3) cancers (P < 0.05).
  
  
  CONCLUSIONS
  Our study provides proof of principle for the application of an 8-plex iTRAQ approach to uncover clinically relevant candidate biomarkers for prostate cancer progression.
authors.affiliation: Department of Human Metabolism, The Mellanby Centre for Bone Research, University of Sheffield Medical School, Sheffield, UK.
authors.forename: Adam
authors.initials: A
authors.lastname: Glen
authors.forename: Caroline A
authors.initials: CA
authors.lastname: Evans
authors.forename: Chee S
authors.initials: CS
authors.lastname: Gan
authors.forename: Simon S
authors.initials: SS
authors.lastname: Cross
authors.forename: Freddie C
authors.initials: FC
authors.lastname: Hamdy
authors.forename: Jonathan
authors.initials: J
authors.lastname: Gibbins
authors.forename: Jenny
authors.initials: J
authors.lastname: Lippitt
authors.forename: Colby L
authors.initials: CL
authors.lastname: Eaton
authors.forename: Josselin
authors.initials: J
authors.lastname: Noirel
authors.forename: Phillip C
authors.initials: PC
authors.lastname: Wright
authors.forename: Ishtiaq
authors.initials: I
authors.lastname: Rehman
mesh_terms: D000818:Animals; D015153:Blotting, Western; D018450:Disease Progression; D014644:Genetic Variation; D006360:Heat-Shock Proteins / Q000235:genetics; D006657:Histones / Q000235:genetics; D006801:Humans; D007150:Immunohistochemistry; D015994:Incidence; D008297:Male; D051379:Mice; D008819:Mice, Nude; D009362:Neoplasm Metastasis; D009368:Neoplasm Transplantation; D017430:Prostate-Specific Antigen / Q000235:genetics*; D011471:Prostatic Neoplasms / Q000453:epidemiology / Q000235:genetics / Q000378:metabolism / Q000401:mortality / Q000473:pathology*; D011960:Receptors, Estrogen / Q000032:analysis / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016019:Survival Analysis; D014174:Transketolase / Q000235:genetics; D014407:Tumor Cells, Cultured
chemical_list: D006360:Heat-Shock Proteins; D006657:Histones; D011960:Receptors, Estrogen; D014174:Transketolase; D017430:Prostate-Specific Antigen