Heterogeneous phenotypes of Pten-null hepatocellular carcinoma in hepatitis B virus transgenic mice parallels liver lobule zonal gene expression patterns

HCC Model Induced by P53 and Pten Knockout in HBV-Transgenic Mice Mirrors Human HCC at the Transcriptome Level

With a multitude of HCC mouse models available, choosing the one that most closely resembles human HCC can be challenging. This study addresses this gap by conducting a comprehensive transcriptomic similarity analysis of widely used HCC mouse models. In this study, RNA-seq was performed on a model induced by double knockout of P53 and Pten via CRISPR/Cas9 in HBV-transgenic mice. Additionally, RNA-seq data from 2345 various other models induced by different methods were collected from GEO databases. The gene expression profiles, immune microenvironments, and metabolic pathways of these models were compared with those of human HCC. The analysis revealed distinct transcriptomic features among the different models. The HBV + P53&Pten KO model demonstrated the highest overall similarity to human HCC across various parameters. It shared a high degree of overlap in differentially expression genes (DEGs) between tumor and non-tumor tissues with human HCC, exhibited a transcriptome profile and immune cell infiltration pattern closely resembling human HCC, and showed metabolic alterations similar to those in human HCC. Conversely the DEN + CCl4-induced model showed the lowest similarity to human HCC in transcriptome profiles and DEGs and exhibited a distinct immune microenvironment with high NK cell infiltration, with minimal metabolic differences between tumor and non-tumor tissues. This study highlights the importance of selecting appropriate HCC mouse models for research. The HBV + p53&Pten KO model emerged as the most promising due to its remarkable similarity to human HCC across various aspects.

Foxa deficiency restricts hepatitis B virus biosynthesis through epigenic silencing

In the hepatis B virus (HBV) transgenic mouse model of chronic infection, the forkhead box protein A/hepatocyte nuclear factor 3 (Foxa/HNF3) family of pioneer transcription factors are required to support postnatal viral demethylation and subsequent HBV transcription and replication. Liver-specific Foxa-deficient mice with hepatic expression of only Foxa3 do not support HBV replication but display biliary epithelial hyperplasia with bridging fibrosis. However, liver-specific Foxa-deficient mice with hepatic expression of only Foxa1 or Foxa2 also successfully restrict viral transcription and replication but display only minimal alterations in liver physiology. These observations suggest that the level of Foxa activity, rather than the combination of specific Foxa genes, is a key determinant of HBV biosynthesis. Together, these findings suggest that targeting Foxa activity could lead to HBV DNA methylation and transcriptional inactivation, resulting in the resolution of chronic HBV infections that are responsible for approximately one million deaths annually worldwide.

IMPORTANCE

The current absence of curative therapies capable of resolving chronic hepatis B virus (HBV) infection is a major clinical problem associated with considerable morbidity and mortality. The small viral genome limits molecular targets for drug development, suggesting that the identification of cellular factors essential for HBV biosynthesis may represent alternative targets for therapeutic intervention. Genetic Foxa deficiency in the neonatal liver of HBV transgenic mice leads to the transcriptional silencing of viral DNA by CpG methylation without affecting viability or displaying an obvious phenotype. Therefore, limiting liver Foxa activity therapeutically may lead to the methylation of viral covalently closed circular DNA (cccDNA), resulting in its transcriptional silencing and ultimately the resolution of chronic HBV infection.

Distinct phenotypic spectra of hepatocellular carcinoma in liver-specific tumor suppressor-deficient hepatitis B virus transgenic mice

The hepatitis B virus (HBV) transgenic mouse model was used to interrogate the origins of HCC heterogeneity. HBV biosynthesis was used as a marker of liver tumor heterogeneity. Principal component and correlation analysis of HBV and cellular transcript levels demonstrated major differences within and between the gene expression profiles of Apc-deficient, Apc-deficient Pten-deficient, and Pten-deficient HCC. Hence, both oncogenic stimuli and zonal hepatocyte properties determine heterogeneous HCC phenotypes. Additionally, Apc-deficient HCC display decreased expression of Apob, Otc and Tet2 relative to Pten-deficient HCC and control liver tissue suggesting their gene products may represent markers of Apc-deficient HCC. A subset of human HCC with mutations in the β-catenin gene (CTNNB1) displayed a gene expression profile similar to that observed in the mouse Apc-deficient HCC indicating this model of liver cancer may be useful for interrogating the molecular properties of these tumors and their potential therapeutic vulnerabilities.