Eight-plex iTRAQ analysis of variant metastatic human prostate cancer cells identifies candidate biomarkers of progression: An exploratory study.
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.
Glen
Adam
A
Department of Human Metabolism, The Mellanby Centre for Bone Research, University of Sheffield Medical School, Sheffield, UK.
Evans
Caroline A
CA
Gan
Chee S
CS
Cross
Simon S
SS
Hamdy
Freddie C
FC
Gibbins
Jonathan
J
Lippitt
Jenny
J
Eaton
Colby L
CL
Noirel
Josselin
J
Wright
Phillip C
PC
Rehman
Ishtiaq
I
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
D006360:Heat-Shock Proteins; D006657:Histones; D011960:Receptors, Estrogen; D014174:Transketolase; D017430:Prostate-Specific Antigen