title: Isocitrate dehydrogenase 1 and 2 mutations in cholangiocarcinoma.
abstract: Somatic mutations in isocitrate dehydrogenase 1 and 2 genes are common in gliomas and help stratify patients with brain cancer into histologic and molecular subtypes. However, these mutations are considered rare in other solid tumors. The aims of this study were to determine the frequency of isocitrate dehydrogenase 1 and 2 mutations in cholangiocarcinoma and to assess histopathologic differences between specimens with and without an isocitrate dehydrogenase mutation. We sequenced 94 formalin-fixed, paraffin-embedded cholangiocarcinoma (67 intrahepatic and 27 extrahepatic) assessing for isocitrate dehydrogenase 1 (codon 132) and isocitrate dehydrogenase 2 (codons 140 and 172) mutations. Multiple histopathologic characteristics were also evaluated and compared with isocitrate dehydrogenase 1/2 mutation status. Of the 94 evaluated specimens, 21 (22%) had a mutation including 14 isocitrate dehydrogenase 1 and 7 isocitrate dehydrogenase 2 mutations. Isocitrate dehydrogenase mutations were more frequently observed in intrahepatic cholangiocarcinoma than in extrahepatic cholangiocarcinoma (28% versus 7%, respectively; P = .030). The 14 isocitrate dehydrogenase 1 mutations were R132C (n = 9), R132S (n = 2), R132G (n = 2), and R132L (n = 1). The 7 isocitrate dehydrogenase 2 mutations were R172K (n = 5), R172M (n = 1), and R172G (n = 1). Isocitrate dehydrogenase mutations were more frequently observed in tumors with clear cell change (P < .001) and poorly differentiated histology (P = .012). The results of this study show for the first time that isocitrate dehydrogenase 1 and 2 genes are mutated in cholangiocarcinoma. The results of this study are encouraging because it identifies a new potential target for genotype-directed therapeutic trials and may represent a potential biomarker for earlier detection of cholangiocarcinoma in a subset of cases.
authors.affiliation: Department of Laboratory Medicine and Pathology, Mayo Clinic College of Medicine, Rochester, MN 55905, USA. kipp.benjamin@mayo.edu
authors.forename: Benjamin R
authors.initials: BR
authors.lastname: Kipp
authors.forename: Jesse S
authors.initials: JS
authors.lastname: Voss
authors.forename: Sarah E
authors.initials: SE
authors.lastname: Kerr
authors.forename: Emily G
authors.initials: EG
authors.lastname: Barr Fritcher
authors.forename: Rondell P
authors.initials: RP
authors.lastname: Graham
authors.forename: Lizhi
authors.initials: L
authors.lastname: Zhang
authors.forename: W Edward
authors.initials: WE
authors.lastname: Highsmith
authors.forename: Jun
authors.initials: J
authors.lastname: Zhang
authors.forename: Lewis R
authors.initials: LR
authors.lastname: Roberts
authors.forename: Gregory J
authors.initials: GJ
authors.lastname: Gores
authors.forename: Kevin C
authors.initials: KC
authors.lastname: Halling
mesh_terms: D001483:Base Sequence; D001650:Bile Duct Neoplasms / Q000235:genetics* / Q000473:pathology; D001653:Bile Ducts, Intrahepatic / Q000473:pathology*; D018281:Cholangiocarcinoma / Q000235:genetics* / Q000473:pathology; D005260:Female; D006801:Humans; D007521:Isocitrate Dehydrogenase / Q000235:genetics*; D008297:Male; D008875:Middle Aged; D009154:Mutation; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: C538784:IDH2 protein, human; D007521:Isocitrate Dehydrogenase; C543588:IDH1 protein, human