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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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 5

E2F8 DNA binding activity is essential for endoreduplication.

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E2F8 DNA binding activity is essential for endoreduplication. (A) Histol...
(A) Histology of livers from 12-month-old 8+/+ and 8DBD/DBD mice. H&E-stained sections (left), immunofluorescence (IF; right) for cadherin 1 (CDH1) (red) and DAPI (blue). Scale bars: 50 μm. (B) Representative fluorescence-activated cell sorting profiles of propidium iodide–stained liver nuclei from 4-month-old 8+/+, 8DBD/DBD, and 8–/– mice. (C) Nuclear liver ploidy of mice from B. Bars represent means ± SEM. Wilcoxon tests with Bonferroni’s correction for multiple tests. *, 8DBD/DBD and/or 8–/– vs. 8+/+. For 8DBD/DBD: 2C, P = 0.002; 4C, P < 0.001; and 8C, P < 0.001. For 8–/–: 2C, P < 0.001; 4C, P = 0.001; 8C, P < 0.001; and 16C, P = 0.002. (D) IHC using Myc epitope–specific antibodies that recognize the expression of 5×Myc-tagged 8DBD (MYC-8DBD) in livers of 8DBD/DBD mice at the indicated ages. Scale bar: 50 μm. (E) Quantification of MYC-8DBD expression in D. Average percentage of positive hepatocytes per ×40 field ± SEM for 2 livers for 0 to 8 weeks and 1 liver for 52 weeks. At least 640 hepatocytes were counted per liver. (F) IF for MYC-8DBD (green), KI-67 (red), and DAPI (blue) in livers of 3-week-old 8DBD/DBD mice. Colocalization of 8DBD and KI-67 (arrowheads). Scale bar: 50 μm. (G) IF for MYC-8DBD (green), EdU (red), and DAPI (blue) of liver sections from tissue removed during partial hepatectomy (Pre-PH), from sham surgery mice (Sham), or regenerating tissue 32 hours after partial hepatectomy (Post-PH). Scale bar: 50 μm. (H) Representative pictures of Sham- and Post-PH–treated livers. The right lobe (which was not excised) is outlined in yellow. Scale bar: 1 cm. (I) Quantification of MYC-8DBD–positive and EdU-positive hepatocytes from livers described in G. At least 100 hepatocytes were counted per liver. n, number of mice per group.