DKK1 and esophageal squamous cell carcinoma: Furthermore, they analyzed the positive expression rates of DKK1 and DKK3 in ESCC and found there were 54.2% of ESCC cases expressing CKAP4 and its ligands (DKK1 40.3%, DKK3 37.5%, and DKK1 and DKK3 23.6%) (Kajiwara et al., 2018).