This article requires a subscription to view the full text. If you have a subscription you may use the login form below to view the article. Access to this article can also be purchased.
Graphical Abstract
Highlights
Seventy-six most promising proteins were qualified, and 19 proteins were verified by SRM in 219 seminal plasma samples of patients with prostate cancer and negative biopsies.
Prostate-specific, secreted and androgen-regulated protein-glutamine gamma-glutamyltransferase 4 (TGM4) was verified by SRM assay and an in-house immunoassay.
TGM4 detected prostate cancer on biopsy in seminal plasma (AUC=0.66), but not in blood serum.
Abstract
Seminal plasma, because of its proximity to prostate, is a promising fluid for biomarker discovery and noninvasive diagnostics. In this study, we investigated if seminal plasma proteins could increase diagnostic specificity of detecting primary prostate cancer and discriminate between high- and low-grade cancers. To select 147 most promising biomarker candidates, we combined proteins identified through five independent experimental or data mining approaches: tissue transcriptomics, seminal plasma proteomics, cell line secretomics, tissue specificity, and androgen regulation. A rigorous biomarker development pipeline based on selected reaction monitoring assays was designed to evaluate the most promising candidates. As a result, we qualified 76, and verified 19 proteins in seminal plasma of 67 negative biopsy and 152 prostate cancer patients. Verification revealed a prostate-specific, secreted and androgen-regulated protein-glutamine gamma-glutamyltransferase 4 (TGM4), which predicted prostate cancer on biopsy and outperformed age and serum Prostate-Specific Antigen (PSA). A machine-learning approach for data analysis provided improved multi-marker combinations for diagnosis and prognosis. In the independent verification set measured by an in-house immunoassay, TGM4 protein was upregulated 3.7-fold (p = 0.006) and revealed AUC = 0.66 for detecting prostate cancer on biopsy for patients with serum PSA ≥4 ng/ml and age ≥50. Very low levels of TGM4 (120 pg/ml) were detected in blood serum. Collectively, our study demonstrated rigorous evaluation of one of the remaining and not well-explored prostate-specific proteins within the medium-abundance proteome of seminal plasma. Performance of TGM4 warrants its further investigation within the distinct genomic subtypes and evaluation for the inclusion into emerging multi-biomarker panels.
- Prostate cancer biomarkers
- serum/plasma
- selected reaction monitoring
- absolute quantification
- assay development
- machine learning
- protein-glutamine gamma-glutamyltransferase 4
- seminal plasma
- TGM4
- XGBoost
Footnotes
Author contributions: A.P.D., K.J., and E.P.D. designed research; A.P.D., P.S., and T.K. performed research; A.P.D. contributed new reagents/analytic tools; A.P.D., M.D., and A.D. analyzed data; A.P.D. wrote the paper; M.E.H. and K.J. provided clinical samples and clinical expertise.
↵* This work was supported by grants from the Canadian Institute of Health Research (#285693) to E.P.D., K.J., and A.P.D, and Prostate Cancer Canada (RS2015-01) to A.P.D.
↵
This article contains supplemental material.
- Received June 4, 2019.
- © 2019 Drabovich et al.
Published under exclusive license by The American Society for Biochemistry and Molecular Biology, Inc.