Tissue Expression of Androgen Receptor Splice Variant 7 at Radical Prostatectomy Predicts Risk of Progression in Untreated Nonmetastatic Prostate Cancer

Abstract

Background: Androgen receptor splice variant V7 (AR-V7) was recently detected in circulating tumor cells of castration-resistant prostate cancer (PC) patients and its expression correlated with resistance to new-generation androgen signaling inhibitors. Objectives: We retrospectively analyzed whether AR-V7 expression was detectable on radical prostatectomy (RP) specimens of untreated nonmetastatic PC cases, and whether it could be associated with progression after surgery. Method: The expression of AR-V7 and AR-FL (full length) was separately evaluated by immunohistochemistry using a streptavidin-biotin-peroxidase system with 2 anti-AR-V7 and anti-AR-FL rabbit monoclonal antibodies. Results: 56 PC cases, classified by their clinical risk, were analyzed. Positive expression was found in 24/32 cases in the high-risk group, 4/13 in the intermediate-risk group, and only 2/11 in the low-risk group. We found a significant correlation between AR-V7 positivity and both risk classification (p < 0.001) and progression after surgery (p < 0.001). Conclusions: In our population of untreated nonmetastatic PC, AR-V7 is detectable by immunohistochemistry in more than 50% of cases. At this early stage, AR-V7 positivity is associated with risk classification and it can predict progression after surgery.