A novel mouse model of cholangiocarcinoma uncovers a role for a SOX17-Tensin 4 pathway in tumor progression

Background & Aims Although earlier diagnosis and treatment of intrahepatic cholangiocarcinoma (iCCA) is necessary to improve therapy, there is still limited information available about initiation and evolution of iCCA precursor lesions. Therefore, there is a need to identify mechanisms driving formation of precancerous lesions and their progression towards invasive tumor using experimental models that faithfully recapitulate human tumorigenesis.Methods We generated a new mouse model which combines cholangiocyte-specific expression of Kras G12D with 3,5-diethoxycarbonyl-1,4-dihydrocollidine diet-induced inflammation to mimic iCCA development in patients with cholangitis. Histological and transcriptomic analyses of the mouse precursor lesions and iCCA were performed and compared with human analyses. The function of genes overexpressed during tumorigenesis was investigated in human cell lines.Results Mice expressing Kras G12D in cholangiocytes and fed a DDC diet developed cholangitis, ductular proliferations, intraductal papillary neoplasms of bile ducts (IPNBs) and eventually iCCAs. The histology of mouse and human IPNBs were highly similar, and mouse iCCAs displayed histological characteristics of human mucin-producing large duct type iCCA. Signaling pathways activated in human iCCA were activated in mice. The identification of transition zones between IPNB and iCCA on tissue sections, combined with RNA-sequencing analyses of the lesions supported that iCCAs derive from IPNBs. We provide evidence that a gene cascade which comprises KRAS G12D , SRY-related HMG box transcription factor 17 ( SOX17 ) and Tensin 4 ( TNS4 ), and which is activated by epidermal growth factor, promotes tumor progression.Conclusions We developed a novel mouse model that faithfully recapitulates human iCCA tumorigenesis and identified a gene cascade promoting tumor progression.* BilIN : biliary intraepithelial neoplasia CK19 : cytokeratin 19 DDC : 3,5-diethoxycarbonyl-1,4 dihydrocollidine EGF : epidermal growth factor EGFR : epidermal growth factor receptor EpCAM : epithelial cell adhesion molecule ERK : extracellular-regulated kinase ERBB2 : v-erb-b2 erythroblastic leukemia viral oncogene homolog 2/human epidermal growth factor receptor 2 eYFP : enhanced yellow fluorescent protein HES1 : hairy and enhancer of split-1 H&E : hematoxylin and eosin IL-33 : interleukin-33 iCCA : intrahepatic cholangiocarcinoma IPNB : intraductal papillary neoplasm of bile ducts KRAS : v-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog MAPK : mitogen activated protein kinase PI3K : phosphoinositide-3-kinase SMAD2 : small mothers against decapentaplegic 2 SOX17 : SRY-related HMG box transcription factor 17 TCGA : The Cancer Genome Atlas TGFβ : transforming growth factor β TNS4 : tensin 4