Cathepsin K regulates the tumor growth and metastasis by IL-17/CTSK/EMT axis and mediates M2 macrophage polarization in castration-resistant prostate cancer

A common stage of advanced prostate cancer is castration-resistant prostate cancer (CRPC), greater understanding of which is required in order to address and solve the clinically difficult challenge. Cathepsin K (CTSK) is a cysteine protease that usually has a strong activity of degrading extracellular matrix and is related to osteoclast-mediated bone destruction. However, the mechanism of CTSK-regulation in CRPC is still unclear to us. The current study aimed to analyze the expression of differentially expressed genes (DEGs) in patient samples (from localized PC and CRPC). Interestingly, we found that CTSK to be significantly up-regulated in CRPC. Through further signal pathway enrichment analysis, we found that the IL-17 signaling pathway to be highly correlated with CTSK. The oncogenic functions of CTSK and IL-17 in CRPC were proven by a series of in vivo and in vitro experiments. Possible downstream molecules of CTSK were investigated, which could serve as control elements to regulate the expression of EMT, thereby facilitating the metastasis and excessive proliferation of PC cells. Expression of CTSK was related to high concentration of M2 tumor-associated macrophages (TAMs) M2 in CRPC. A CTSK-mediated feedback circuit between TAMs and CRPC tissues was indicated in the process of transfer, proving the possibility of CTSK could be use as an available therapeutic target for CRPC.