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.
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.
IDH1/2 (p=0.0005) and BAP1 (p=0.0097) mutations were characteristic of ICC, while KRAS (p=0.0019) and TP53 (p=0.0019) were more frequent in ECC and GBC.
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.
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.
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 %).
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%).
IDH1 and IDH2 mutations were significantly associated with increased levels of p53 in intrahepatic cholangiocarcinomas, but no mutations in the p53 gene were found, suggesting that mutations in IDH1 and IDH2 may cause a stress that leads to p53 activation.
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.
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.
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.
Moreover, IDH and Kras mutations, genetic alterations that co-exist in a subset of human IHCCs, cooperate to drive the expansion of liver progenitor cells, development of premalignant biliary lesions, and progression to metastatic IHCC.
In line with these findings, human ICC with IDH mutations are characterized by a hepatic progenitor cell transcriptional signature suggesting that they are a distinct ICC subtype as compared to IDH wild type tumors.