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Regulation of Liver Regeneration and Hepatocarcinogenesis by Suppressor of Cytokine Signaling 3

ABSTRACT: Suppressor of cytokine signaling 3 (SOCS3) down-regulates several signaling pathways in multiple cell types, and previous data suggest that SOCS3 may shut off cytokine activation at the early stages of liver regeneration. We developed hepatocyte-specific Socs3 knockout (Socs3 h-KO) mice to directly study the role of SOCS3 during liver regeneration after 2/3 partial hepatectomy (PH). Socs3 h-KO mice demonstrate marked enhancement of DNA replication and liver weight restoration after 2/3 PH in comparison with littermate controls. Without SOCS3, signal transducer and activator of transcription 3 (STAT3) phosphorylation is prolonged, and activation of the mitogenic kinases extracellular signal-regulated kinase 1/2 (ERK1/2) is enhanced after PH. In vitro, we show that SOCS3 deficiency enhances hepatocyte proliferation in association with enhanced STAT3 and ERK activation after epidermal growth factor (EGF) or interleukin 6 (IL-6) stimulation. Microarray analyses show that SOCS3 modulates a distinct set of genes after PH, which fall into diverse physiologic categories. Using a model of chemical-induced carcinogenesis, we found that Socs3 h-KO mice develop hepatocellular carcinoma (HCC) at an accelerated rate. By acting on cytokines and multiple proliferative pathways, SOCS3 modulates both physiologic and neoplastic proliferative processes in the liver, and may act as a tumor suppressor. Keywords: SOCS3, liver regeneration

ORGANISM(S): Mus musculus

PROVIDER: GSE9549 | GEO | 2007/12/12

SECONDARY ACCESSION(S): PRJNA103365

REPOSITORIES: GEO

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Project description:Suppressor of cytokine signaling 3 (SOCS3) down-regulates several signaling pathways in multiple cell types, and previous data suggest that SOCS3 may shut off cytokine activation at the early stages of liver regeneration. We developed hepatocyte-specific Socs3 knockout (Socs3 h-KO) mice to directly study the role of SOCS3 during liver regeneration after 2/3 partial hepatectomy (PH). Socs3 h-KO mice demonstrate marked enhancement of DNA replication and liver weight restoration after 2/3 PH in comparison with littermate controls. Without SOCS3, signal transducer and activator of transcription 3 (STAT3) phosphorylation is prolonged, and activation of the mitogenic kinases extracellular signal-regulated kinase 1/2 (ERK1/2) is enhanced after PH. In vitro, we show that SOCS3 deficiency enhances hepatocyte proliferation in association with enhanced STAT3 and ERK activation after epidermal growth factor (EGF) or interleukin 6 (IL-6) stimulation. Microarray analyses show that SOCS3 modulates a distinct set of genes after PH, which fall into diverse physiologic categories. Using a model of chemical-induced carcinogenesis, we found that Socs3 h-KO mice develop hepatocellular carcinoma (HCC) at an accelerated rate. By acting on cytokines and multiple proliferative pathways, SOCS3 modulates both physiologic and neoplastic proliferative processes in the liver, and may act as a tumor suppressor. Experiment Overall Design: Hepatocyte-specific excision of the Socs3 gene was achieved by breeding Socs3 fl/fl mice with mice expressing the Cre recombinase transgene under control of the albumin promoter (Alb-Cre+), yielding Socs3 h-KO mice. Socs3 fl/fl, Alb-Cre- littermates were used as controls for all experiments, and are henceforth referred to as littermates. All mice (C57BL/6) were free of Helicobacter species, housed in a specific pathogen free facility with 12-h light/dark cycles with free access to standard food and water. 2/3 PH and sham operations were performed as previously described (15, 50) (n=3-6 mice per genotype per time point). Liver remnants were weighed after removal of necrotic stumps and sutures, and compared to post-operative body weight. For HCC experiments, a single i.p. injection of DEN (5mg/kg, Sigma) was performed 12-14 d after birth. For short time points, a single injection of DEN (100mg/kg) (31) was given to 4 wk old mice. At indicated time points, mice were sacrificed by CO2 inhalation. All animal studies were carried out under approved IACUC protocols at the University of Washington.

Project description:TCPOBOP (1,4-Bis [2-(3,5-Dichloropyridyloxy)] benzene) is a constitutive androstane receptor (CAR) agonist that induces robust hepatocyte proliferation and hepatomegaly without any liver injury or tissue loss. TCPOBOP-induced direct hyperplasia has been considered to be CAR-dependent with no evidence of involvement of cytokines or growth factor signaling. Receptor tyrosine kinases (RTKs), MET and EGFR, are known to play a critical role in liver regeneration after partial hepatectomy, but their role in TCPOBOP-induced direct hyperplasia, not yet explored, is investigated in the current study. Disruption of the RTK-mediated signaling was achieved utilizing MET KO mice along with Canertinib treatment for EGFR inhibition. Combined elimination of MET and EGFR signaling [MET KO + EGFRi], but not individual disruption, dramatically reduced TCPOBOP-induced hepatomegaly and hepatocyte proliferation. TCPOBOP-driven CAR activation was not altered in [MET KO + EGFRi] mice, as measured by nuclear CAR translocation and analysis of typical CAR target genes. However, TCPOBOP induced cell cycle activation was impaired in [MET KO + EGFRi] mice due to defective induction of cyclins, which regulate cell cycle initiation and progression. TCPOBOP-driven induction of FOXM1, a key transcriptional regulator of cell cycle progression during TCPOBOP-mediated hepatocyte proliferation, was greatly attenuated in [MET KO + EGFRi] mice. Interestingly, TCPOBOP treatment caused transient decline in HNF4α expression concomitant to proliferative response; this was not seen in [MET KO + EGFRi] mice. Transcriptomic profiling revealed vast majority (~40%) of TCPOBOP-dependent genes mainly related to proliferative response, but not to drug metabolism, were differentially expressed in [MET KO + EGFRi] mice. Conclusion: Taken together, combined disruption of EGFR and MET signaling lead to dramatic impairment of TCPOBOP-induced proliferative response without altering CAR activation. We used microarrays to detail the global programme of gene expression in [METKO + EGFRi] mice liver following TCPOBOP treatment

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Regulation of Liver Regeneration and Hepatocarcinogenesis by Suppressor of Cytokine Signaling 3

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