DKK1 and hereditary clear cell renal cell carcinoma: As a major regulator of the Wnt signaling pathway, DKK1 induces cellular apoptosis in many diseases.29, 30, 31, 32 Overexpression of DKK1 sensitizes cells in brain tumors,42 renal-cell carcinoma and thyroid cancers43, 44 to apoptosis.