DNAJB1–PRKACA fusion kinase interacts with β-catenin and the liver regenerative response to drive fibrolamellar hepatocellular carcinoma

Abstract A segmental deletion resulting in DNAJB1– PRKACAgene fusion is now recognized as the signature genetic event of fibrolamellar hepatocellular carcinoma(FL-HCC), a rare but lethal liver cancer that primarily affects adolescents and young adults. Here we implement CRISPR- Cas9 genome editingand transposon-mediated somatic gene transfer to demonstrate that expression of either the endogenous fusion protein or a chimeric cDNA leads to the formation of indolent liver tumorsin mice that closely resemble human FL-HCC. Notably, overexpression of the wild-type PRKACAwas unable to fully recapitulate the oncogenic activity of DNAJB1– PRKACA, implying that FL-HCC does not simply result from enhanced PRKACAexpression. Tumorigenesis was significantly enhanced by genetic activation of β-catenin, an observation supported by evidence of recurrent Wnt pathway mutations in human FL-HCC, as well as treatment with the hepatotoxin3,5-diethoxycarbonyl-1,4-dihydrocollidine, which causes tissue injury, inflammation, and fibrosis. Our study validates the DNAJB1– PRKACAfusion kinase as an oncogenic driver and candidate drug target for FL-HCC, and establishes a practical model for preclinical studies to identify strategies to treat this disease.