In contrast, the protein expression level of A20 in CCA tumor tissues was conspicuously higher than that in the corresponding peritumoral biliary tissues (2.23-fold on average, P < 0.0001), and it was also significantly higher than the protein expression level of A20 in normal biliary duct tissues (Fig 1C). This evidence concerns the gene TNFAIP3 and cholangiocarcinoma.