E2f8 mediates tumor suppression in postnatal liver development
Lindsey N. Kent, … , Alain de Bruin, Gustavo Leone
Lindsey N. Kent, … , Alain de Bruin, Gustavo Leone
Published July 25, 2016
Citation Information: J Clin Invest. 2016;126(8):2955-2969. https://doi.org/10.1172/JCI85506.
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Research Article Oncology

E2f8 mediates tumor suppression in postnatal liver development

Abstract

E2F-mediated transcriptional repression of cell cycle–dependent gene expression is critical for the control of cellular proliferation, survival, and development. E2F signaling also interacts with transcriptional programs that are downstream of genetic predictors for cancer development, including hepatocellular carcinoma (HCC). Here, we evaluated the function of the atypical repressor genes E2f7 and E2f8 in adult liver physiology. Using several loss-of-function alleles in mice, we determined that combined deletion of E2f7 and E2f8 in hepatocytes leads to HCC. Temporal-specific ablation strategies revealed that E2f8’s tumor suppressor role is critical during the first 2 weeks of life, which correspond to a highly proliferative stage of postnatal liver development. Disruption of E2F8’s DNA binding activity phenocopied the effects of an E2f8 null allele and led to HCC. Finally, a profile of chromatin occupancy and gene expression in young and tumor-bearing mice identified a set of shared targets for E2F7 and E2F8 whose increased expression during early postnatal liver development is associated with HCC progression in mice. Increased expression of E2F8-specific target genes was also observed in human liver biopsies from HCC patients compared to healthy patients. In summary, these studies suggest that E2F8-mediated transcriptional repression is a critical tumor suppressor mechanism during postnatal liver development.

Authors

Lindsey N. Kent, Jessica B. Rakijas, Shusil K. Pandit, Bart Westendorp, Hui-Zi Chen, Justin T. Huntington, Xing Tang, Sooin Bae, Arunima Srivastava, Shantibhusan Senapati, Christopher Koivisto, Chelsea K. Martin, Maria C. Cuitino, Miguel Perez, Julian M. Clouse, Veda Chokshi, Neelam Shinde, Raleigh Kladney, Daokun Sun, Antonio Perez-Castro, Ramadhan B. Matondo, Sathidpak Nantasanti, Michal Mokry, Kun Huang, Raghu Machiraju, Soledad Fernandez, Thomas J. Rosol, Vincenzo Coppola, Kamal S. Pohar, James M. Pipas, Carl R. Schmidt, Alain de Bruin, Gustavo Leone

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Figure 8

Identification of putative direct targets of E2F7/8 and evaluation of their relevance to human disease.

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Identification of putative direct targets of E2F7/8 and evaluation of th...
(A) Fold-change heat map of differentially expressed genes (DEGs) in livers from 4-week-old 7Δ/Δ 8Δ/Δ and control mice measured by Agilent Microarrays. DEGs are defined as having ≥ 1.5-fold change vs. control (P ≤ 0.05). Overlap of DEGs and E2F7/8-occupied promoters (ChIP-seq) represent putative ‘developmental’-associated direct targets. (B) Expression heat map of DEGs in livers or tumors from 12-month-old mice as measured by RNA-seq. DEGs were identified using CuffDiff (≥ 1.5-fold change and FDR < 0.5 between 7Δ/Δ 8Δ/Δ tumor vs. normal control samples). Overlap of DEGs and E2F7/8-occupied promoters represent putative ‘tumor’-associated direct targets. (C) Transcription factor (TF) binding site analysis of putative E2F7/8 targets showing the occurrence and estimated importance of the top 10 TF sites as well as all E2F sites (red). (D) Tag-intensity heat map showing the distribution of tags for all E2F7 and E2F8 promoter peaks identified by ChIP-seq that were associated with DEGs. Peaks were centered on E2F8-specific samples except for peaks that were specific to E2F7. (E) Heat map showing the expression of the 88 developmental-associated E2F7/8 target genes (from A) in normal (Norm) and diseased human patient samples. Cirrhosis (Cir), dysplasia (Dysp), early (E HCC), or advanced HCC (Adv HCC) human livers. (F) Heat map showing the expression of the 69 tumor-associated E2F7/8 target genes (from B) in normal and diseased human patient samples. (G) Kaplan-Meier plots showing % survival of patients that have low (<10%; black line) or high (≥10%; red line) expression of the 88 ‘developmental’-associated target genes. (H) Kaplan-Meier plots showing % survival of patients that have low (<10%; black line) or high (≥10%; red line) expression of the 69 ‘tumor’-associated target genes. HR, hazard ratio (G and H).