Loss of YAP protein in prostate cancer is associated with Gleason score increase

Aims and Background: To investigate the expression of YAP protein by immunohistochemistry in prostate cancer tissues and hyperplasia or normal prostate tissues adjacent to cancer, and establish the correlation of YAP expression with Gleason score. Methods and Study design: The expression of YAP protein was evaluated in tissue microarray by immunohistochemistry. The samples included 66 radical prostatectomy specimens with clinically detected prostate cancer and 54 hyperplasia or normal prostate tissues adjacent to cancer. Results: YAP expression was present mainly in the nuclei of basal cells in both prostate cancer tissues and normal prostate or hyperplasia tissues adjacent to cancer. Cytoplasmic expression of YAP was weaker than nuclear expression in both malignant and nonmalignant luminal epithelial cells. YAP expression was decreased or lost in prostate cancer tissues; hyperplasia or normal prostate tissues adjacent to cancer exhibited stronger nuclear and cytoplasmic expression of YAP (p = 0.0001). Downregulation of YAP expression in prostate cancer samples correlated with Gleason score increase (p = 0.002). Conclusions: This immunohistochemical study expands our knowledge of the expression and localization of YAP in prostate cancer tissue and nonmalignant prostate tissue adjacent to cancer. YAP might function as a tumor suppressor in prostate cancer. Such information may provide the foundation for the treatment of preneoplastic and neoplastic lesions of the prostate.