The cyclin E regulator cullin 3 prevents mouse hepatic progenitor cells from becoming tumor-initiating cells
Uta Kossatz, … , Jeffrey D. Singer, Nisar P. Malek
Uta Kossatz, … , Jeffrey D. Singer, Nisar P. Malek
Published October 11, 2010
Citation Information: J Clin Invest. 2010;120(11):3820-3833. https://doi.org/10.1172/JCI41959.
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Research Article Oncology

The cyclin E regulator cullin 3 prevents mouse hepatic progenitor cells from becoming tumor-initiating cells

Abstract

Cyclin E is often overexpressed in cancer tissue, leading to genetic instability and aneuploidy. Cullin 3 (Cul3) is a component of the BTB-Cul3-Rbx1 (BCR) ubiquitin ligase that is involved in the turnover of cyclin E. Here we show that liver-specific ablation of Cul3 in mice results in the persistence and massive expansion of hepatic progenitor cells. Upon induction of differentiation, Cul3-deficient progenitor cells underwent substantial DNA damage in vivo and in vitro, thereby triggering the activation of a cellular senescence response that selectively blocked the expansion of the differentiated offspring. Positive selection of undifferentiated progenitor cells required the expression of the tumor suppressor protein p53. Simultaneous loss of Cul3 and p53 in hepatic progenitors turned these cells into highly malignant tumor-initiating cells that formed largely undifferentiated tumors in nude mice. In addition, loss of Cul3 and p53 led to the formation of primary hepatocellular carcinomas. Importantly, loss of Cul3 expression was also detected in a large series of human liver cancers and correlated directly with tumor de-differentiation. The expression of Cul3 during hepatic differentiation therefore safeguards against the formation of progenitor cells that carry a great potential for transformation into tumor-initiating cells.

Authors

Uta Kossatz, Kai Breuhahn, Benita Wolf, Matthias Hardtke-Wolenski, Ludwig Wilkens, Doris Steinemann, Stephan Singer, Felicitas Brass, Stefan Kubicka, Brigitte Schlegelberger, Peter Schirmacher, Michael P. Manns, Jeffrey D. Singer, Nisar P. Malek

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Figure 1

Loss of Cul3 leads to accumulation of hepatic progenitor cells in the liver.

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Loss of Cul3 leads to accumulation of hepatic progenitor cells in the li...
(A) Livers from Cul3loxP/loxP AlfpCre mice were harvested at 4 and 8 weeks after birth. The livers showed a pale discoloration and firm consistency. Upon microscopic analysis, hepatocytes could be distinguished from small mononucleated cells. Arrow indicates small mononucleated cells in strands (compare inset) that surround hepatocytic fields. (B) LacZ stainings in Cul3loxP/loxP AlfpCre Rosa26-LacZ mice were used to analyze the functionality of the Cre recombinase. Scale bars: 50 μm; 20 μm (insets). (C) Immunofluorescence and immunohistochemical detection of progenitor-associated surface markers CK14, CD34 (first and third columns), and CD133. In wild-type livers, CK14-positive cells are primarily localized around bile ducts (compare arrows). CD34- and CD133-positive cells can only be found in Cul3-knockout livers (compare arrows that indicate positive cells in the strands). Cells also expressed the hepatocyte marker albumin. In the albumin staining, arrows indicate small mononucleated cells in the strands positive for albumin. Images in the second and fourth columns display the Dapi staining of the respective areas. Scale bars: 10 μm (top panels); 50 μm (bottom panels). (D) Quantification of hepatocytes in livers from Cul3loxP/loxP AlfpCre mice. H&E sections and β-catenin stainings (compare Supplemental Figure 1E) were used to quantitate the number of hepatocytes in the livers. For each quantification, 3–4 mice were analyzed. (E) Quantification of progenitor cells positive for CD34, CD133, and CK14 at 4 and 8 weeks after birth. For each quantification, 3–4 mice were analyzed. **P < 0.005.