Identification of a plasticity driver of Combined Hepatocellular-Cholangiocarcinoma using functional interspecies comparison

Primary liver cancer (PLC) comprises hepatocellular carcinoma (HCC) and intrahepatic cholangiocarcinoma (iCCA), which may occur together as combined HCC-CCA (cHCC-CCA). For both tumor components, a single cell of origin is suggested. It is debated whether the cell of origin belongs to the stem/progenitor cell type or may represent a fully differentiated liver cell. It is believed that iCCA develops from biliary epithelial cells and that hepatocytes give rise to HCC. However, lineage tracing experiments in mice showed that iCCA may develop from hepatocytes while HCC can originate from ductular cells. These results suggest that differentiated liver epithelial cells can transdifferentiate based on their cellular plasticity. Mutation spectra of both hepatocellular carcinoma and cholangiocarcinoma have been published: However, it remains to be elucidated, which of these alterations are driving the tumor phenotype or determine its biological behavior. Determining the underlying mechanisms will have profound impact on our understanding of cancer biology and treatment options. In this project, an interspecies approach combining human, mouse, and in vitro data was performed to identify factors that affect the phenotype of liver cancer cells. Human primary liver cancer samples were selected by morphological analysis and subjected to genome-wide exomic and transcriptomic profiling. Next generation sequencing (NGS) data were integrated and candidate genes potentially affecting the phenotype of the tumor cells were identified. Between the two components of cHCC-CCA, 54 differentially expressed and/or differentially mutated genes were found. These were functionally validated by in vivo RNAi screening in mosaic mouse models of HCC (MYC-AKT1 in wildtype mice) and iCCA (KRASG12V in p19-deficient mice), which were generated by hydrodynamic tail vein injection of transposon vectors. Histological analysis of formalin-fixed paraffin-embedded individual tumor nodules followed by immunohistological assessment of hepatocellular (Hnf4α) ...