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

Abstract

A segmental deletion resulting in DNAJB1-PRKACA gene 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 editing and transposon-mediated somatic gene transfer to demonstrate that expression of both the endogenous fusion protein or a chimeric cDNA leads to the formation of indolent liver tumors in mice that closely resemble human FL-HCC. Notably, overexpression of the wild type PRKACA was unable to fully recapitulate the oncogenic activity of DNAJB1-PRKACA, implying that FL-HCC does not simply result from enhanced PRKACA expression. 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 hepatotoxin 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC), which causes tissue injury, inflammation and fibrosis. Our study validates the DNAJB1-PRKACA fusion 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. SignificanceEfforts to understand and treat FL-HCC have been confounded by a lack of models that accurately reflect the genetics and biology of the disease. Here, we demonstrate that the Dnajb1-Prkaca gene fusion drives tumorigenesis in mice, and that fusion to DNAJB1 drives FL-HCC initiation more effectively than wild type PRKACA overexpression. The requirement of the PRKACA kinase domain in tumor initiation establishes the potential utility of kinase inhibitors targeting the fusion. By identifying genetic and environmental factors that can enhance the consistency and aggressiveness of disease progression, we reveal biological characteristics of the disease and advance a robust platform for future pre-clinical studies.

Hotspots of aberrant enhancer activity in fibrolamellar carcinoma reveal molecular mechanisms of oncogenesis and intrinsic drug resistance

“…To determine whether the DNAJB1-PRKACA fusion is sufficient to perturb these genes of interest, we took advantage of two murine models of FLC. In the first model, a transposon expressing human DNAJB1-PRKACA is introduced into the livers of C57BL/6 mice by hydrodynamic tail vein injection, forming FLC-like liver tumors (Kastenhuber et al, 2017). We examined the expression of our genes of interest in the resulting liver tumors compared to livers from mice injected with an empty vector control.…”

“…FLC is genetically characterized by a ~400 kb heterozygous deletion on chromosome 19 that leads to the formation of the DNAJB1-PRKACA fusion (Honeyman et al, 2014). This fusion occurs in at least 80% of patients (Cornella et al, 2014;Honeyman et al, 2014), is specific to FLC (Dinh et al, 2017;Graham et al, 2015;Kastenhuber et al, 2017), and is sufficient to drive liver tumor formation in mice (Engelholm et al, 2017;Kastenhuber et al, 2017). Multiple groups have performed genome-scale analyses to identify dysregulated genes (Cornella et al, 2014;Dinh et al, 2017;Griffith et al, 2016;Malouf et al, 2014;Simon et al, 2015;Sorenson et al, 2017;Xu et al, 2014), long non-coding RNAs (Dinh et al, 2017), and microRNAs (Dinh et al, 2019;Farber et al, 2018) in FLC.…”

Fibrolamellar carcinoma as a distinct subtype of hepatocellular carcinoma: molecular genetics features, diagnostics and treatment prospects

“…Экзогенная экспрессия химерного гена в клеточных линиях ГЦР приводит к повышению скорости пролиферации и способности клеток образовывать колонии [33]. Делеция гомологичного делетируемому в ФлК челове ка участка генома у мышей или экзогенная экспрессия хи мерного белка DNAJB1PRKАCA вызывают формирование опухолей печени с морфологическими и молекулярногене тическими характеристиками, аналогичными ФлК [34].…”

“…К настоящему времени данных о разработке и испытаниях такого ингибитора в литературе не представлено, однако успешный опыт создания и эффективного использования специфических киназных ингибиторов для терапии лей козов и опухолей легкого, а также разработка клеточных и in vivo экспериментальных моделей ФлК [26,34] позво ляет надеяться на появление такого препарата в недале ком будущем.…”

“…Являясь ключевым драйвером развития опухоли, химерный белок DNAJB1PRKCA может быть использован для дифференциальной диагностики ФлК, поскольку вы соко специфичен для конкретного типа опухолей и вы является методами, рутинно адаптируемыми для кли нической практики. Согласно данным опубликованных исследований [34,35] Abstract: Fibrolamellar carcinonoma (FLC) was described in 1956 as a separate subtype of hepatocellular carcinoma (HCC) that affects young adults without underling liver diseases. Morphologically FLC is characterized as HCC with large cells, gross nucleus and fibrous collagen bands organized into branched net.…”