To explore the specificity of GPC1, we analyzed expression of GPC1 in hepatocellular carcinoma (n = 40), cholangiocarcinoma (n = 40), gallbladder carcinoma (n = 40), colorectal carcinoma (n = 40), gastric carcinoma (n = 40), and prostate cancer (n = 40). Here, GPC1 is linked to cholangiocarcinoma.