DKK1 play a key role in growth and migration of prostate cancer cells

Prostate cancer is the most common cancer in Western countries and represents the fifth cause of cancer death. Androgen deprivation therapy is the first choice treatment in metastatic tumors. However, chemotherapy often is needed as consequence of tumor resistance, with frequent side effects and disappointing results. Therefore, new therapeutic approaches for metastatic and advanced prostate cancer are necessary. DKK1 is an inhibitor of the Wnt signaling pathway and its expression is increased in different types of cancer. In prostate cancer patients with bone metastases, an increase of DKK1 is observed both in the serum and in the prostate tissue, suggesting that DKK1 might be considered as a new molecular target in the metastatic prostate cancer therapy. The aim of this study was to evaluate the role of DKK1 in growth and migration of different prostate cancer cell lines: PC3 and DU145, which express high levels of DKK1, and LNCAP, which lacks DKK1. To this end, we carried out DKK1 gene knockout by CRISPR/CAS9 system in PC3 (PC3_KO) and DU145 (DU145_KO) cells and we overexpressed DKK1 by permanently transfection of LNCAP cell line (LNCAP_DKK1). Real-Time PCR, Western Blotting analysis, and secretion levels by ELISA confirmed DKK1 knockout and overexpression, respectively. The effects of knockout and overexpression were evaluated in terms of cell growth by colorimetric WST-1 test and cell migration by transwell migration assay. In PC3_KO and DU145_KO cells, a significant reduction of mRNA, protein levels and secretion of DKK1 was observed; functionally, DKK1 knockdown resulted in a reduction of cell growth (PC3_KO vs PC3 WT, p<0.05; DU145_KO vs DU145 WT, p<0.05) and migration (PC3_KO vs PC3 WT, p<0.001; DU145_KO vs DU145 WT, p<0.001) On the contrary, very high levels of DKK1 (at mRNA, protein levels and secretion) confirmed the permanent transfection of LNCAP cell line resulting in an increase of cell growth (LNCAP_DKK1 vs LNCAP WT, p<0.05) and migration (LNCAP_DKK1 vs LNCAP WT, p<0.001). In conclusion, our data support a key role of DKK1 in the growth and migration of prostate cancer cells. Based on our study, DKK1 may represent a specific target for a new therapy intended to specifically block its function in metastatic and advanced prostate cancer.