Integrative clustering of genetic and epigenetic data identified four iCCA subgroups with prognostic relevance further designated as IDH, high (H), medium (M), and low (L) alteration groups.
IDH1/2 mutations appeared more frequently in ICC (23.6%, P = 0.0002) than in GBC (4.0%) or ECC (2.3%), while ERBB2/3 mutations were found only in GBC (20.0%) and ECC (11.4%).
Intrahepatic cholangiocarcinomas are most likely to harbor mutations in isocitrate dehydrogenase genes (IDH1, IDH2), fibroblast growth factor receptors (FGFR1, FGFR2, FGFR3), Eph receptor 2 (EPHA2), and BAP1 (gene involved in chromatin remodeling) genes, whereas ARID1B, ELF3, PBRM1, cAMP dependent protein kinase (PRKACA, and PRKACB) genetic mutations were implicated more commonly in distal and perihilar subtypes.
Large-duct iCCA and pCCA more frequently had the loss of SMAD4 expression and MDM2 amplifications than small-duct iCCA, whereas the loss of BAP1 expression and IDH1 mutations were mostly restricted to small-duct iCCA.
Isocitrate dehydrogenases 1 and 2 (IDH1/2), KRAS protooncogene GTPase (KRAS), a RAS Viral Oncogene Homolog in neoroblastoma (NRAS) and P53 are primary genetic alterations in ICC.
D-2HG serum level measurement by liquid chromatography coupled to tandem mass spectrometry is a sensitive, specific, precise (a coefficient of variation <10% and an accuracy >95%), fast (9 min run per sample) and inexpensive surrogate marker of IDH1/2 somatic mutation in ICC.
Novel genomic alterations such as <i>FGFR2</i> fusions and <i>IDH1/2</i> mutations in intrahepatic cholangiocarcinoma (ICC) and <i>ERBB2</i> alterations in gallbladder cancer (GBCA) are emerging as targeted therapy options capable of advancing precision medicine for the care of these patients.
Although the IDH1 mutation rate between iCC and HCC demonstrated no significant difference, clear cell HCC revealed statistically increased mutation rate compared to that of HCC without clear cell change (P = 0.009).
Specificities are observed for some alterations and anatomical subtypes: frequent fibroblast growth factor receptor 2 (FGFR2) and isocitrate dehydrogenase 1/2 (IDH1/2) alterations are specific to intrahepatic cholangiocarcinomas (ICCs), whereas frequent ERBB2 oncogene alterations are specific to extrahepatic cholangiocarcinomas (ECCs) and gallbladder carcinomas (GBCs).
In CHC-SC-CLCs, the mutation rate of isocitrate dehydrogenase 1 (IDH1) or IDH2 was significantly higher (35%) than in MF (4%) or non-MF (0) ICCs (P < .001).
The most frequently mutated genes in EH-PCC were KRAS (47.4 %), TP53 (23.7 %) and ARID1A (15.8 %); in IH-PCC were KRAS (22.2 %), PBRM1 (16.7 %), and PIK3CA (16.7 %); and in ICC were IDH1 (17.1 %), NRAS (17.1 %), and BAP1 (14.3 %).
Genetic analyses revealed that KRAS mutation was significantly more frequent in type 1 ICC, whereas IDH mutation and FGFR2 translocation were restricted to type 2 ICC.
IDH1 and IDH2 are homodimeric enzymes that catalyze the conversion of isocitrate to α-ketoglutarate (α-KG) and concomitantly produce reduced NADPH from NADP(+) Mutations in the genes encoding IDH1 and IDH2 have recently been found in a variety of human cancers, most commonly glioma, acute myeloid leukemia (AML), chondrosarcoma, and intrahepatic cholangiocarcinoma.