|Verification of Candidate Protein Biomarkers of Prostate Cancer by MRM Mass Spectrometry|
|Wed 11:00 AM - Session: Disease Markers|
|Candidate protein biomarkers of prostate cancer were discovered by differential expression analysis of Golgi proteins isolated from human prostate tumors and associated normal tissue from the same patients. Proteins contained in the Golgi lumen are destined to be released into the blood and therefore provide an accessible source of tissue-specific disease markers. Included among the proteins up-regulated in the lumen of the Golgi from the tumor were most of the known prostate tumor secretory protein markers as well as several unexpected biomarker candidates. The known markers PSA, KLK2, MIF, and ACPP are present in the 1 ng/ml range in blood. Although the relatively low plasma concentration makes these proteins inaccessible to direct biomarker discovery in the blood plasma, after immunopurification they are easily detectable by mass spectrometry.
Multiple reaction monitoring (MRM) assays have been developed to measure the concentration of these proteins in plasma. The MRM assays serve to verify both the expression level and the amino acid sequence of the candidate markers. Preliminary verification has been carried out on the same patients who provided the tissue for the biomarker discovery. Further verification will be carried out on an expanded patient cohort. Thus, the MRM assay can provide a relatively rapid method for verification of candidate biomarkers and accelerate the conversion of these markers into useful clinical assays.