DKK4 and prostate cancer: Although poorly studied in prostate cancer, both downregulation and upregulation of DKK4 are reported to promote tumor progression in other human epithelial malignancies through the activation of Wnt/β-catenin signaling or other oncogenic cascades (e.g., non-canonical Wnt/JNK signaling or the MAPK cascade), respectively (reviewed in [161]).