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

Hepatocellular carcinoma (HCC) and cholangiocarcinoma (CCA) represent the two most common types of primary liver cancer, while combined HCC-CCA (cHCC-CCA) is rarely observed. Lineage-tracing studies in mice have shown that cholangiocarcinoma may develop from hepatocytes, while ductular cells may also give rise to HCC as a result of their plasticity. The aim of this project was to identify molecular mechanisms leading to a phenotypic switch in tumor cells resulting in cHCC-CCA formation.

Exome and transcriptome sequencing of HCC and CCA components of fifteen human cHCC-CCA samples was conducted. Data integration identified 57 potential phenotypic driver genes which were altered between both tumor compartments. In vivo RNAi screening was used to validate the candidate genes using two transposon-based mosaic mouse models (HCC model: MYC-AKT1 in C57BL/6 mice; iCCA model: KRASG12V in p19-/- mice). Individual tumor nodules displaying a phenotypic switch in tumor type based on histopathological evaluation were sequenced to identify the expressed shRNA.

One candidate gene (to be disclosed during the meeting) was identified and validated. It was upregulated in the CCA compartment of human cHCC-CCA and shRNA-mediated knockdown of gene expression resulted in a mixed HCC-CCA in the iCCA mouse model, while its overexpression led to cHCC-CCA formation in the HCC mouse model. Functional analyses in vitro revealed a protumorigenic impact on clonogenicity and cell viability of isogenic cell lines derived from our HCC mouse model compared to the controls.

Altogether, we discovered a new driver of cellular plasticity in liver cancer. Further mechanistic characterization is ongoing.

Publikationsverlauf

Artikel online veröffentlicht:
26. Januar 2022