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Combined blockade of MET and EGFR abolishes liver regeneration

ABSTRACT: Receptor tyrosine kinases MET and EGFR are critically involved in initiation of liver regeneration. Other cytokines and signaling molecules also help in the early part of the process. Regeneration employs effective redundancy schemes to compensate for missing signals. Elimination of any single signaling pathway only delays but does not abolish the process. Our present study, however, shows that combined systemic elimination of MET and EGFR signaling abolishes liver regeneration, prevents restoration of liver mass and leads to liver decompensation. Our results demonstrate that liver function is dependent on synchronous availability of signaling from these two pathways. The study shows that MET and EGFR separately control many non-overlapping signaling endpoints, allowing for compensation when only one of the signals is blocked. The combined elimination of the signals however was not tolerated. The results provide critical new information on interactive MET and EGFR signaling and the contribution of their combined absence to regeneration arrest and liver decompensation. We used microarrays to detail the global programme of gene expression in METKO-canertinib mouse liver following a partial hepatectomy

ORGANISM(S): Mus musculus

PROVIDER: GSE77867 | GEO | 2016/10/27

SECONDARY ACCESSION(S): PRJNA311906

REPOSITORIES: GEO

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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

Project description:EGFR is a critical regulator of hepatocyte proliferation and liver regeneration. Our recent work indicated EGFR can also regulate lipid metabolism during liver regeneration after partial-hepatectomy. Based on these findings, we investigated role of EGFR in a mouse model of NAFLD utilizing a pharmacological inhibition strategy. C57BL6/J mice were fed chow-diet, or fast-food diet with/without EGFR inhibitor (Canertinib) for 2-months. EGFR inhibition completely prevented development of steatosis and liver injury in this model. In order to study if EGFR inhibition can reverse NAFLD progression, mice were fed fast-food diet for 5-months, with/without Canertinib-treatment for the last 5-weeks of the study. EGFR-inhibition remarkably decreased steatosis, liver injury, fibrosis and improved glucose tolerance. Microarray analysis revealed ~40% of genes altered by fast-food diet were differentially expressed after EGFR-inhibition, and thus, are potentially regulated by EGFR. Several genes and enzymes related to lipid metabolism (particularly fatty-acid synthesis and lipolysis), which were disrupted by fast-food diet, were found to be modulated by EGFR. Several crucial transcription factors that play a central role in regulating these lipid metabolism genes during NAFLD, including PPARγ, SREBF1, ChREBP and HNF4α, were also found to be modulated by EGFR. In fact, ChIP-analysis revealed PPARγ binding to several crucial lipid metabolisms genes (Fasn, Scd1 and Plin2) was drastically reduced by EGFR inhibition. Further upstream, EGFR-inhibition suppressed AKT signaling, which is known to control these transcription factors, including PPARγ and SREBF1, in NAFLD models. Lastly, the effect of EGFR in FFD-induced fatty-liver phenotype was not shared by receptor-tyrosine-kinase MET, as investigated using MET-KO mice. In-conclusion, our study revealed a role of EGFR in NAFLD and the potential of EGFR-inhibition as a treatment strategy for NAFLD. We used microarrays to detail the global programme of gene expression in liver of C57BL6/J mice fed fast-food diet mice treated with EGFR inhibitor (canertinib)

Project description:Background: Genetic elimination of c-Met signaling in the liver has been shown to impact many cellular pathways involved in repair, regeneration, lipid homeostasis and redox balance. In this study, we analyzed a nutritional model of hepatic steatosis in Met fl/fl ; Alb-Cre +/- (MetKO) mice in a 129SV/C57BL/6 background fed a high cholesterol diet for 30 days. Methods: Liver injury was determined by histopathology and plasma enzymes, transcriptomic changes were examined using gene expression microarrays, and evaluation of key molecules involved in liver damage and lipid homestasis were evaluated by Western blot analysis. Results: We observed that in comparison with wild type mice subjected to the same diet, MetKO mice developed a strong liver lipid deposition, inflammatory infiltration and increment in total bile acids synthesis and liver damage markers. Global transcriptomic changes analysis confirmed the steatosis and cholestasis induced by the high cholesterol diet. In addition, we found affected pathways related to amino acids, glutathione and lipid metabolism, oxidative stress and mitochondria dysfunction. Oxidative stress exacerbation was corroborated by lipid and protein oxidation in liver tissue. To address further, Western blot studies revealed downregulation on Erk, NF-kB and Nrf2 survival pathways and target genes (cyclin D1, SOD1, gamma-GCS), an increment in proapoptotic proteins (p53, caspase 3) and changes in nuclear receptors such as RAR and RXR, which were increased, and CAR, FXR and PPAR alfa, which were decreased, in the MetKO diet. These results are in agreement with the steatosis and cholestasis phenotype. Conclusion: Our data provide evidence of c-Met signaling involvement in lipid metabolism, and bile acids synthesis and excretion. Disruption of these pathways leads to liver dysfunction, improper metabolism and hepatocellular damage. Global transcriptome changes between WT mice vs. c-Met KO mice fed a 2% cholesterol and 0.5% sodium cholate diet (high cholesterol) or a Chow regular diet (Chow) as control. Mice were fed a high cholesterol or chow regular diet for 30 days. Liver tissue was obtained, and RNA was extracted and subjected to Illumina microarray analysis.

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Combined blockade of MET and EGFR abolishes liver regeneration

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