Urinary Exosome Based Androgen Receptor Variant 7 Detection in Metastatic Castration Resistant Prostate Cancer Patient

BACKGROUND Androgen receptor variant 7 (AR-V7) detection provides important reference to the clinical management of abiraterone in metastatic castration-resistant PCa (mCRPC). We performed a noninvasive urine-derived exosomal AR-V7 analysis in mCRPC patients. METHODS A total of 34 mCRPC patients were categorized into 16 patients responded to abiraterone (ABI-Sta group) and 18 were resistant to abiraterone (ABI-Res group). First morning urine collected from patients as well as healthy control were used for analysis. Exosomal RNA was isolated for AR-V7 detection, and the correlation between AR-V7 expression and the therapeutic effect of abiraterone was analyzed. RESULTS Urine is ideal biological sample for exosome separation and androgen receptor full-length (AR-FL) analysis. Positive urine-derived exosomal AR-V7 were detected in 32.4% (11 of 34) mCRPC urine samples. Positive AR-V7 is more common in ABI-Res patients (50.0% in ABI-Res group vs. 12.5% in ABI-Sta patients respectively, p =0.009) and associate with higher PSA progression rate and poorer overall survival (p=0.0031, 0.0012). CONCLUSIONS Urine-derived exosome is an alternative option for liquid biopsy-based AR-V7 detection in prostate cancer. Urinary exosomal AR-V7 is a dynamic marker that may predict the response to abiraterone in mCRPC patients.