Prostate cancer is the most common malignancy and the second leading cause of cancer-related deaths in men.
One common treatment is androgen-deprivation therapy, which reduces symptoms in most patients. However, over time, patients develop tumours that are androgen-independent and ultimately fatal. The mechanisms that cause this transition remain largely unknown, and as a result, there are no effective treatments against androgen-independent prostate cancer. As a model platform, we used the LNCaP cell line, and its androgen independent derivative, LNCaP-SF. Utilizing stable isotope labelling with amino acids in cell culture (SILAC) coupled to mass spectrometry, we assessed the differential global protein expression between the two cell lines. Our proteomic analysis resulted in the quantification of 3355 proteins. Bioinformatic prioritization resulted in 42 up-regulated and 46 down-regulated proteins in LNCaP-SF cells, compared to LNCaP cells. Our top candidate, HMGCS2, an enzyme involved in ketogenesis, was found to be 9-fold elevated in LNCaP-SF cells, based on peptide ratios. After analyzing the remaining enzymes of this pathway (ACAT1, BDH1, HMGCL, OXCT1), we observed increased expression of these proteins in the LNCaP-SF cells, which were further verified using western blotting. To determine whether these enzymes are up-regulated in clinical samples, we performed qPCR and immunohistochemistry on human prostate cancer tissues, from which we observed significantly increased transcript and protein levels in high grade cancer (Gleason Grade ≥8). In addition, we observed significant elevation these enzymes in the LuCaP 96AI castration-resistant xenograft. Further assessment of ACAT1 on human castration-resistant metastatic prostate cancer tissues revealed substantially elevated expression of ACAT1 in these specimens. Taken together, our results indicate that enzymes of the ketogenic pathway are up-regulated in high grade prostate cancer, and could serve as potential tissue biomarkers for diagnosis or prognosis of high grade disease.
Written by:
Saraon P, Cretu D, Musrap N, Karagiannis GS, Batruch I, Drabovich AP, van der Kwast T, Mizokami A, Morrissey C, Jarvi KA, Diamandis EP. Are you the author?
University of Toronto, Canada.
Reference: Mol Cell Proteomics. 2013 Feb 26. Epub ahead of print.
doi: 10.1074/mcp.M112.023887
PubMed Abstract
PMID: 23443136
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