As depicted in Fig. 1A, the expression of SLC31A1 is significantly lower in certain tumours than in the adjacent normal tissues, including cholangiocarcinoma (CHOL), kidney renal clear cell carcinoma (KIRC), kidney renal papillary cell carcinoma (KIRP), liver hepatocellular carcinoma (LIHC), lung adenocarcinoma (LUAD), lung squamous cell carcinoma (LUSC), thyroid carcinoma (THCA), and prostate adenocarcinoma (PRAD). This evidence concerns the gene SLC31A1 and cholangiocarcinoma.