CHRDL2 and cholangiocarcinoma: By dividing CC samples into clusters and further investigating NAD+ metabolic-related genes implicated in CC progression, we pinpointed 21 prognostic NAD+ metabolic-related genes (ADAMTS10, ANGPTL5, APCDD1L, CCDC85A, CGREF1, CHRDL2, CRP, DENND5B, EFS, FGF8, P4HA3, PCDH20, PCDHAC2, RASGRF2, S100P, SLC19A3, SLC6A14, TESC, TFPI, TNMD, ZNF229) using univariate and multivariate regression analyses.