Comparative analysis of prostate cancer specific biomarkers in whole urine, urinary sediments and exosomes.

Hendriks, R.J. (2014) Comparative analysis of prostate cancer specific biomarkers in whole urine, urinary sediments and exosomes. thesis, Medicine.

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Abstract

Purpose: Prostate cancer (PCa) is the most commonly diagnosed malignancy in men from Western countries. Serum prostate specific antigen (PSA) level is used as a tool in the detection, staging and monitoring of PCa. However, it has limitations as an early detection biomarker because it is not prostate cancer-specific. Therefore, there is an urgent need for new, more specific biomarkers to detect PCa. Numerous mRNA-based biomarkers with possible clinical value have been identified in urine. Urine consists of different fractions which can be used as substrate for biomarker testing. Especially urinary exosomes have been studied as promising source for identifying new biomarkers. The aim of this study was to compare the expression levels of PCa-related biomarkers in three urine fractions - whole urine, urinary sediments (cell pellets) and exosomes - and to evaluate the effect of digital rectal examination (DRE) on the expression levels of these biomarkers. The diagnostic performance of the PCa-specific biomarkers PCA3 and ERG was assessed. Material and methods: In this prospective explorative study urine samples were obtained before and after DRE from men (n=29) undergoing prostate biopsies based on elevated serum PSA (≥3.0 ng/ml) and/or suspicious DRE. The urine was separated in whole urine, cell pellets and exosomes prior to biomarker analysis. Biomarker mRNA expression levels were measured with qPCR. Non-parametric statistical tests were used to compare the biomarker expression levels. The diagnostic performance was determined by comparing the expression levels to prostate biopsy results using Receiver Operating Characteristics (ROC) curves. Results: The expression levels of the biomarkers PSA, PCA3 and ERG were highest in whole urine, followed by exosomes. PSA mRNA, PCA3 mRNA and ERG mRNA expression was significantly higher after DRE in whole urine (p=0.000, p=0.000 and p=0.002 resp.), cell pellet (p=0.000, p=0.002 and p=0.022 resp.) and exosomes (p=0.000, p=0.000 and p=0.011 resp.). Moreover, less samples after DRE contained an amount of mRNA below the analytical detection limit for qPCR testing. PCa was diagnosed in 15 of the 29 patients (51.7%). PCa patients had a higher amount of biomarker mRNA in all urine fractions after DRE compared to patients without PCa. The expression level of PCA3 in PCa-patients was significantly higher in whole urine and cell pellet samples after DRE (p=0.018 and p=0.023 resp.). ERG expression was also significantly higher in cell pellets from PCa-patients after DRE (p=0.020). The diagnostic performance of PCA3 increased after DRE in all urine fractions. Conclusion: Whole urine samples taken after performing a DRE seem to be the substrate of choice to use molecular diagnostics for early diagnosis of PCa in clinical urological practice. DRE has a significant positive effect on the amount of biomarker mRNA measured in all urine fractions and should be considered as necessary in biomarker testing. Urinary exosomes contain more biomarker mRNA compared to cell pellets but the analytical process is much more complicated. Therefore, the clinical use of urinary exosomes in biomarker testing needs to be further investigated in larger clinical studies.

Item Type:	Thesis (Thesis)
Supervisor name:	Schalken, Prof. dr. J.A. and Dijkstra, Drs. S. and Department Urology and Radboud University and Medical Center, Nijmegen and Nijholt, Dr. I.M. and Isala, Zwolle
Faculty:	Medical Sciences
Date Deposited:	25 Jun 2020 10:57
Last Modified:	25 Jun 2020 10:57
URI:	https://umcg.studenttheses.ub.rug.nl/id/eprint/1721

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