Further, the DKK1 promoter methylation status of tumor cells in the TCGA database were analyzed, and were found that the DKK1 promoter region of pancreatic adenocarcinoma cells were in hypomethylated state, colon adenocarcinoma cells showed differentially methylated state, and renal cell carcinoma cells showed hypermethylated state (Fig. S8B). The gene discussed is DKK1; the disease is renal cell carcinoma.