Distinct phenotypic consequences of cholangiocarcinoma-associated FGFR2 alterations depend on biliary epithelial maturity

Epithelial cancers disrupt tissue architecture and are often driven by mutations in genes that play important roles in normal epithelial morphogenesis. The intrahepatic biliary system is an epithelial tubular network that forms within the developing liver via the de novo initiation and expansion of apical lumens. Intrahepatic biliary tumors (intrahepatic cholangiocarcinoma) commonly harbor activating genomic alterations in the FGFR2 receptor tyrosine kinase, which plays important roles in epithelial morphogenesis in other developmental settings. Using a physiologic and quantitative 3D model we demonstrate that FGFR signaling is important for biliary morphogenesis and that oncogenic FGFR2 fusions and in-frame deletions disrupt biliary architecture. Importantly, we show that the trafficking of and signaling from the FGFR2 mutants, as well as their phenotypic impacts, are governed by the epithelial state of the cell. Unexpectedly, we also found that distinct tumor-driving FGFR2 mutants disrupt biliary morphogenesis in completely different and clinically relevant ways, informing our understanding of morphogenesis and tumorigenesis and highlighting the importance of convergent studies of both. Summary statementUsing a physiologic 3D model of biliary tubulogenesis, Chiasson-MacKenzie et al. show that FGFR2 signaling is important for biliary morphogenesis and that different intrahepatic cholangiocarcinoma-causing FGFR2 alterations have unexpectedly distinct and epithelial state-specific impacts on biliary architecture.