Presentation Authors: Tariq A. Khemees*, Bing Yang, Adam Schultz, Glenn O. Allen, Joseph Gawdzik, Kyle A. Richards, Tracy M. Downs, E. Jason Abel, David F. Jarrard, Madison, WI
Introduction: Prostate cancer (PCa) development and progression are driven by the interplay of genetic and epigenetic changes that include DNA methylation. The detection of PCa cells in urine has been hindered by their infrequent shedding, but non-tumor prostate cells are found more frequently (14-20%). These normal cells contain DNA methylation alterations associated with a cancer field defect. In the current study, we analyzed a series of DNA methylation field markers to determine if they predict the presence of PCa using urine samples.
Methods: Following IRB approval, urine samples were collected after prostate biopsy for patients who presented with an elevated PSA from 2012 to 2016. Urine samples were collected from patients with biopsy-proven PCa (90), and without PCa (77). From the urine pellet, methylated DNA was analyzed across several regions near EVX1, CAV1 and PLA2G16 using bisulfite pyrosequencing. Normal prostate tissue for EVX1 and CAV1 has previously found to involve a field methylation defect (J Urol, 2015). PLA2G16 methylation was tested in non-tumor tissues from patients with and without PCa.
Results: Mean patient age was 64yo and mean PSA was 13ng/ml. Methylation changes in urine cell pellets showed significantly increased methylation at CpG shores associated with EVX1, CAV1 and PLA2G16 genes from patients who had PCa compared to those without PCa. Predictive accuracy for prostate cancer detection was measured using ROC curves: EXV1 (AUC 0.75, OR 1.09; 95% CI 0.94-1.25), CAV1 (AUC 0.75, OR 1.07; 95% CI 0.96-1.2) and PLA2G16 (AUC 0.75, OR 1.19; 95% CI 1.02-1.38). Combined three-marker assay performed better than PSA with AUC of 0.76 vs PSA AUC of 0.61 (P=0.01) (Figure). Further analysis of PLA2G16 showed significant hypermethylation in histologically normal prostate biopsies from patients with PCa compared to those without (21% vs 24% respectively; p < 0.001). Decreased PLA2G16 gene expression negatively correlates to methylation (R= -0.47, p < 0.001).
Conclusions: Methylation of PLA2G16, EVX1 and CAV1 distinguishes between tumor associated and non-tumor associated prostate tissues marking a field defect associated with the development of PCa. Genes methylated in this field defect can be detected in urine and may be utilized as a novel biomarker approach to detect PCa.
Source of Funding: Funded by Urology Care Foundation / AUA Research Scholar Award (T.K.)