A Chemical Glycoproteomics Platform Applied to Human Prostate Cancer

Abstract

Accurate diagnosis and treatment of prostate cancer demands a highly specific biomarker of prostate cancer, as prostate‐specific antigen (PSA), the current clinical biomarker for prostate cancer, suffers from high false positive and high false negative rates that leave many men without a conclusive diagnosis. As glycoproteins have proven to be altered in most cancers, we have focused on studying glycoproteins in human prostate tissue samples. We have developed an efficient method for labeling and enriching glycoproteins, followed by MS‐based analysis of normal and carcinoma tissue. Human prostate tissue derived from radical prostatectomies, at varying states of prostatic disease is chemically tagged with an azide functionalized monosaccharide. Labeled tissue slices are reacted with a biotin‐functionalized probe for the capture of azido‐sialylated glycoproteins. Once analysis of labeled tissue confirmed azide‐dependent labeling, glycoproteins were digested and analyzed on a linear ion trap mass spectrometer with collision‐induced dissociation (CID). Greater than 60% of the proteins identified by LC‐MS/MS were cell‐surface or secreted proteins, indicating that this strategy achieves enrichment of low abundance proteins. Additionally, a comparative proteomics analysis between diseased and healthy tissue identified proteins unique to each tissue type, which are undergoing further validation as potential biomarkers. Virtually all clinically approved cancer biomarkers are glycoproteins and this work extends the application of existing metabolic labeling techniques, while developing new methodologies for cellular labeling to discover biomarkers associated with prostate cancer.