MDM2 and intrahepatic cholangiocarcinoma: Importantly, though p53 is the most frequently mutated gene in human cancers, it is noteworthy that QBC939 and RBE cell lines used in this study were reported to bear wild‐type (WT) p53 genes.[17, 18] In order to verify whether the inhibitory role of circUGP2 in ICC progression was through regulating the p53 signaling pathway, we used pifithrin‐α hydrobromide (PFT), a p53 protein inhibitor,[19] as well as idasanutlin, a p53‐MDM2 complex antagonist,[20] to inhibit/activate the p53 signaling pathway (Figure 3D,E).