Abstract 4618: Integrative molecular classification of extrahepatic cholangiocarcinoma

Background and Aims: Cholangiocarcinoma (CCA) is the second most common primary hepatic malignancy. Based on its anatomical location, CCA can be divided into intrahepatic (iCCA) or extrahepatic (eCCA), with differences in etiology, pathogenesis and clinical management. Few studies have focused on the molecular profiling of eCCA as a single entity, even though it accounts for the most prevalent subtype. Thus, integrative genomic analysis of eCCA would provide critical understanding for the biological traits of this tumor. Methods: 189 FFPE primary eCCA treated by resection were collected at seven international centers from 1995 to 2015. Median survival of the cohort was of 48.5mo. Whole gene-expression profiles were submitted to unsupervised clustering by NMF consensus. Clusters were characterized by Gene Set Enrichment Analysis and Ingenuity Pathway Analysis. Activation of signaling pathways (mTOR/pRPS6 and HER2) was assessed by immunohistochemistry (IHC). Molecular features were correlated with clinico-pathological data. Screening of most prevalent somatic mutations and copy number aberrations is ongoing. Results: We have identified four distinct molecular subtypes of eCCA (cophenetic coefficient=0.995). Tumors classified within the metabolic class (18.7%) were enriched by gene signatures defining bile and fatty acid metabolism (p<0.001) and presented overexpression of classic hepatocyte markers, with HNF4A as the major activated upstream transcription factor (p<0.001). The proliferation class (22.5%) was associated with papillary histology (p=0.004) and presented enrichment of MYC (p<0.001), mTOR (p=0.018) and HER2 (p=0.024) signaling. Subclass mapping identified similarity with the iCCA proliferation subclass (p<0.001). The mesenchymal class (47.3%) was associated with signatures defining epithelial-mesenchymal transition (p<0.001) as well as stromal activation (p<0.001), which was in accordance with TGFB1 as the major activated upstream regulator (p<0.001) and the presence of higher desmoplasia at pathological analysis (p=0.046). Moreover, mesenchymal tumors were significantly associated with poor prognosis in terms of OS (33.2 vs 55.5mo, HR=2.02, p=0.022). Finally, tumors classified as immune class (11.5%) presented increased tumor-infiltrating lymphocytes (p=0.001) and were characterized by enrichment of IFNγ signaling (p<0.001). Conclusions: Transcriptome-based subtyping of eCCA identifies four distinct molecular classes (metabolic, proliferation, mesenchymal and immune) that correlate with clinical-pathological characteristics. These findings enhance the opportunities for therapeutic development in this tumor with dismal prognosis and without approved molecular treatments. Citation Format: Robert Montal, Wei Qiang Leow, Carla Montironi, Laia Bassaganyas, Agrin Moeini, Daniela Sia, Roser Pinyol, Laia Cabellos, Judit Peix, Miho Maeda, Carlos Villacorta, Parissa Tabrizian, Christine Sempoux, Beatriz Minguez, Tim Pawlik, Ismail Labgaa, Lewis Roberts, Manel Sole, Maria Isabel Fiel, Swan Thung, Sasan Roayaie, Augusto Villanueva, Myron Schwartz, Josep Maria Llovet. Integrative molecular classification of extrahepatic cholangiocarcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4618.