GATA2 exosomal mRNA: A novel urine biomarker for the diagnosis of clinically significant prostate cancer.

Abstract

18 Background: Prostate specific antigen (PSA) detection in blood is widely used to screen for prostate cancer (PCa). However, PSA has limited utility in discriminating tumors at high risk of progression from indolent-low risk tumors, which leads to PCa overtreatment and highlights the need to identify better biomarkers for the detection of clinically significant PCa (Gleason Score; GS ≥ 7). Here, we introduce a novel mRNA GATA2 exosomal biomarker detected in urine useful to diagnose clinically significant PCa. Exosomes are 50-120 nm sized vesicles shed in body fluids that contain RNA, DNA, and protein that can be used as biomarkers to interrogate the health of the originating cells. GATA2 is a pioneer transcription factor specific to PCa, increased in aggressive tumors. Methods: To evaluate the predictive value of exosomal GATA2 mRNA levels for aggressive PCa, we isolated exosomes using ultracentrifugation in non-DRE urines from 128 males with elevated PSA serum levels (> 4ng/ml) and analyzed them according to their tissue biopsy result. Results: Importantly, prostate origin of GATA2 mRNA detected in urine exosomes was confirmed by observing that exosomal GATA2 mRNA levels significantly dropped after prostatectomy (p < 0.05). Most remarkably, GATA2 exosomal mRNA expression was significantly increased in PCa biopsy positive patients (n=88) when compared to biopsy negative males (n=28, p < 0.001). Furthermore, GATA2 levels in PCa patients were significantly associated with GS, but not with disease stage and PSA levels. Multivariable regression analysis showed that GATA2 exosomal mRNA levels are an independent factor for the diagnosis of aggressive PCa. Urine GATA2 exosome mRNA expression plus SOC (age and PSA) was associated with improved discrimination of GS ≥ 7 versus GS 6 and benign disease: AUC of SOC alone 0.59 (0.49-0.70, p value=0.083) vs SOC plus GATA2 AUC of 0.68 (95% CI, 0.58-0.78, p value=0.0004). Conclusions: The analysis of urine exosomal GATA2 mRNA in individuals with high PSA may help distinguish clinically significant PCa and reduce the number of patients that need biopsy. Future studies are focused on combining this biomarker to others, such as urine exosomal PCA3, already used in the clinic.