Gadi Lalazar

Transcriptomic characterization of fibrolamellar hepatocellular carcinoma

Significance Fibrolamellar hepatocellular carcinoma (FLHCC) is a rare pediatric liver cancer. A deletion of ∼400 kb in one copy of chromosome 19 results in a chimeric protein, an activated protein kinase A. No other deletions, amplifications, mutations, or structural variants were found. This strongly implicates the chimera as the driving mutation. This paper examines gene expression in FLHCC. The results establish FLHCC as a single disease distinct from other cancers, including hepatocellular carcinoma. The results help explain some of the known pathophysiology: the collagen fibers that give fibrolamellar its name and the gynecomastia reported in young male patients. Finally, this work identifies oncogenes whose expression is increased and that may serve as targets for therapeutic intervention. Fibrolamellar hepatocellular carcinoma (FLHCC) tumors all carry a deletion of ∼400 kb in chromosome 19, resulting in a fusion of the genes for the heat shock protein, DNAJ (Hsp40) homolog, subfamily B, member 1, DNAJB1, and the catalytic subunit of protein kinase A, PRKACA. The resulting chimeric transcript produces a fusion protein that retains kinase activity. No other recurrent genomic alterations have been identified. Here we characterize the molecular pathogenesis of FLHCC with transcriptome sequencing (RNA sequencing). Differential expression (tumor vs. adjacent normal tissue) was detected for more than 3,500 genes (log2 fold change ≥1, false discovery rate ≤0.01), many of which were distinct from those found in hepatocellular carcinoma. Expression of several known oncogenes, such as ErbB2 and Aurora Kinase A, was increased in tumor samples. These and other dysregulated genes may serve as potential targets for therapeutic intervention.

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

Significance Efforts to understand and treat fibrolamellar hepatocellular carcinoma (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 preclinical studies. 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 either 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 the hepatotoxin 3,5-diethoxycarbonyl-1,4-dihydrocollidine, 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.

Fibrolamellar Carcinoma: Recent Advances and Unresolved Questions on the Molecular Mechanisms

Fibrolamellar hepatocellular carcinoma (FLC) is a rare form of primary liver cancer that affects adolescents and young adults without underlying liver disease. Surgery remains the mainstay of therapy; however, most patients are either not surgical candidates or suffer from recurrence. There is no approved systemic therapy and the overall survival remains poor. Historically classified as a subtype of hepatocellular carcinoma (HCC), FLC has a unique clinical, histological, and molecular presentation. At the genomic level, FLC contains a single 400kB deletion in chromosome 19, leading to a functional DNAJB1-PRKACA fusion protein. In this review, we detail the recent advances in our understanding of the molecular underpinnings of FLC and outline the current knowledge gaps.

Intracranial metastasis in fibrolamellar hepatocellular carcinoma

Fibrolamellar hepatocellular carcinoma (FLHCC) is a rare liver malignancy in adolescents and young adults. Surgery is the mainstay of therapy for primary and metastatic disease. Most patients relapse, with development of both local and distant metastases. Brain metastases from solid tumors are rare in the pediatric and young adult population. Here, we document three patients with brain metastases from FLHCC, confirmed by histology and molecular characterization of the chimeric fusion DNAJB1–PRKACA, each necessitating neurosurgical intervention. These observations highlight the ability of FLHCC to metastasize to the brain and suggest the need for surveillance neuroimaging for patients with advanced‐stage disease.

PSMD5 Inactivation Promotes 26S Proteasome Assembly during Colorectal Tumor Progression

Protein degradation by the ubiquitin-proteasome system (UPS) is central to protein homeostasis and cell survival. The active 26S proteasome is a large protease complex consisting of a catalytic 20S subunit and 19S regulatory particles. Cancer cells are exposed to considerable protein overload due to high metabolic rates, reprogrammed energy metabolism, and aneuploidy. Here we report a mechanism that facilitates the assembly of active 26S proteasomes in malignant cells. Upon tumorigenic transformation of the gut epithelium, 26S proteasome assembly was significantly enhanced, but levels of individual subunits were not changed. This enhanced assembly of 26S proteasomes increased further with tumor progression and was observed specifically in transformed cells, but not in other rapidly dividing cells. Moreover, expression of PSMD5, an inhibitor of proteasome assembly, was reduced in intestinal tumors and silenced with tumor progression. Reexpression of PSMD5 in tumor cells caused decreased 26S assembly and accumulation of polyubiquitinated proteins. These results suggest that inhibition of cancer-associated proteasome assembly may provide a novel therapeutic strategy to selectively kill cancer cells.Significance: Enhanced cancer-associated proteasome assembly is a major stress response that allows tumors to adapt to and to withstand protein overload.Graphical Abstract: http://cancerres.aacrjournals.org/content/canres/78/13/3458/F1.large.jpg Cancer Res; 78(13); 3458-68. ©2018 AACR.

DNAJB1-PRKACA fusion kinase drives tumorigenesis and interacts with β-catenin and the liver regenerative response.

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. Practical and scalable mouse models of this disease serve as a resource to further explore tumor development and treatment. Significance Limited resources are available for the treatment of FL-HCC and a lack of research tools have led to an absence of experimental characterization of the disease. Here, we describe a rapidly scalable method to generate synchronous cohorts of mice bearing FL-HCC tumors. We demonstrate that the Dnajb1-Prkaca gene fusion drives tumorigenesis in mice, and that fusion to DNAJB1 drives FL-HCC initiation more strongly than wild type PRKACA overexpression. The requirement of the PRKACA kinase domain reinforces 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 platform for future pre-clinical studies.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.

Non coding RNA analysis in fibrolamellar hepatocellular carcinoma

Fibrolamellar hepatocellular carcinoma (FLC) is a rare primary liver cancer found in adolescents and young adults without underlying liver disease. A deletion of ~400 kD has been found in one copy of chromosome 19 in the tumor tissue of all patients tested. This produces a fusion of the genes DNAJB1 and PRKACA which, in turn, produces a chimeric transcript and protein. Transcriptomic analysis of the tumor has shown upregulation of various oncologically relevant pathways, including EGF/ErbB, Aurora Kinase A, pak21 and wnt. To explore other factors that may contribute to oncogenesis, we examined the microRNA (miRNA) and long non-coding RNA (lncRNA) expression in FLC. The non-coding RNA expression profile in tumor tissue samples is distinctly different from the adjacent normal liver and from other liver tumors. Furthermore, miRZip knock down or over expression of certain miRNAs led to changes in the levels of coding genes that recapitulated changes observed in FLC, suggesting mechanistically that the changes in the cellular levels of miRNA are not merely correlative. Thus, in addition to serving as diagnostic tools for FLC, non-coding RNAs may serve as therapeutic targets.

FGF21: How sweet it is!

The liver hormone fibroblast growth factor 21 suppresses sweet and alcohol preferences.

Stressed-out dads can (metabolically) stress their kids

Paternal psychological stress induces hepatic gluconeogenesis and hyperglycemia in offspring.

What the elephant knew

Multiple copies of P53 may lie at the basis of the elephant’s resistance to cancer.