RecruitingPhase 2Drug trialBortezomib in Patients With Metastatic Castration-Resistant Prostate Cancer With PTEN DeletionThe goal of this clinical trial is to test the anti-tumor activity of bortezomib in participants with Metastatic Castration Resistant Prostate Cancer (mCRPC) with PTEN Deletion. The main question\[s\] it aims to answer is if the use of bortezomib will result in a decline in PSA for participants. Participants will receive a sub-cutaneous injection of bortezomib for up 8 cycles. Each cycle is about 21 days.