HELLS and cholangiocarcinoma: Four were protective factors (ACO1, PEBP1, GOT1, and CXCL12), and 13 genes were risk factors (FANCD2, MT1G, PTGS2, SQLE, NQO1, SLC1A5, TF, MUC1, HELLS, SLC7A5, HAMP, SLC2A1, and RRM2) in CCA patients.