APOE and intrahepatic cholangiocarcinoma: Then, a PPI network was built to research the correlation of the DEGs, and twenty hub genes that were all downregulated in ICC were discovered by cytoscape 3.8.2, including CAT, APOB, HP, C3, FGA, AHSG, APOE, KNG1, FGG, GC, EHHADH, TF, A2M, AMBP, AGT, HPX, ITIH4, ACAA1, ACOX2 and ECI2.