Clinical validity of CTC detection as a biomarker for predicting overall survival of patients with metastatic castration-resistant prostate cancer patients (mCRPC) was provided by the application of the AdnaTest, in which magnetic beads conjugated with HER2 and EpCAM antibodies were utilized to isolate CTCs, followed by qRT-PCR analysis of captured cells for expression of prostate-specific genes (KLK3, PSMA, and EGFR) [245]; assays were also designed to detect AR splice variants and ligand-binding domain mutations associated with resistance to AR-directed therapies. Here, KLK3 is linked to prostate cancer.