Organoid models of fibrolamellar carcinoma mutations reveal hepatocyte transdifferentiation through cooperative BAP1 and PRKAR2A loss

An in-depth understanding of the molecular pathogenesis of fibrolamellar carcinoma (FLC) is hampered due to limited human preclinical models. Here the authors engineer human organoids to reflect different FLC genetic backgrounds and show that hepatocytes can be a cell-of-origin of FLC that transdifferentiate into ductal/progenitor like cells due to combined BAP1 and PRKAR2A loss. Fibrolamellar carcinoma (FLC) is a lethal primary liver cancer, affecting young patients in absence of chronic liver disease. Molecular understanding of FLC tumorigenesis is limited, partly due to the scarcity of experimental models. Here, we CRISPR-engineer human hepatocyte organoids to recreate different FLC backgrounds, including the predominant genetic alteration, the DNAJB1-PRKACA fusion, as well as a recently reported background of FLC-like tumors, encompassing inactivating mutations of BAP1 and PRKAR2A. Phenotypic characterizations and comparisons with primary FLC tumor samples revealed mutant organoid-tumor similarities. All FLC mutations caused hepatocyte dedifferentiation, yet only combined loss of BAP1 and PRKAR2A resulted in hepatocyte transdifferentiation into liver ductal/progenitor-like cells that could exclusively grow in a ductal cell environment. BAP1-mutant hepatocytes represent primed cells attempting to proliferate in this cAMP-stimulating environment, but require concomitant PRKAR2A loss to overcome cell cycle arrest. In all analyses, DNAJB1-PRKACA(fus) organoids presented with milder phenotypes, suggesting differences between FLC genetic backgrounds, or for example the need for additional mutations, interactions with niche cells, or a different cell-of-origin. These engineered human organoid models facilitate the study of FLC.

Automated summary

By engineering human organoids to reflect different genetic backgrounds of fibrolamellar carcinoma (FLC), the authors demonstrate that hepatocytes can be a cell-of-origin of FLC that transdifferentiate into ductal/progenitor like cells due to combined BAP1 and PRKAR2A loss.