KRT5 and benign prostatic hyperplasia: Indeed, parallel analysis of YAP1 and CK5 protein expression in benign prostate hyperplasia (BPH), hormone naive PC (HNPC), and CRPC tissue revealed that in BPH, endogenous YAP1 is predominantly expressed in the nuclei of the AR-negative, CK5-positive basal epithelial cells (Figure 2A, 2B).