Simultaneous expression of DKK1 and CKAP4 is associated with poor prognosis in pancreatic ductal adenocarcinoma (PDAC), lung adenocarcinoma and squamous cell carcinoma, and esophageal squamous cell carcinoma (ESCC) patients [21–23]. The gene discussed is DKK1; the disease is esophageal squamous cell carcinoma.