In the digestive tract, CTSB was overexpressed in colon adenocarcinoma (COAD), esophageal carcinoma (ESCA), pancreatic adenocarcinoma (PAAD), rectum adenocarcinoma (READ), and stomach adenocarcinoma (STAD) rather than cholangiocarcinoma and liver hepatocellular carcinoma (Figure 3E). Here, CTSB is linked to cholangiocarcinoma.