Dickkopf-3 function in the prostate: implications for epithelial homeostasis and tumor progression.

The tumor suppressor Dickkopf-3 (Dkk-3) is rather a unique molecule. Although it is related to the Dickkopf family of secreted Wnt antagonists, it does not directly inhibit Wnt signaling, and its function and mechanism of action are unknown. Endogenous Dkk-3 was recently found to be required to limit cell proliferation both in the developing mouse prostate and in 3D cultures of human prostate epithelial cells. Dkk-3 was further shown to modulate the response of normal prostate epithelial cells to transforming growth factor-β (TGF-β). These studies are consistent with a model in which Dkk-3 is required by normal cells to prevent the TGF-β switch from tumor suppressor to tumor promoter. Here, we discuss these findings and their potential impact on the development and progression of prostate cancer.