Loss of c-Met Disrupts Gene Expression Program Required for G2/M Progression during Liver Regeneration in Mice

conditional knockout mice to determine the effects of c-Met dysfunction in hepatocytes on kinetics of liver regeneration. primary hepatocytes and partially restored expression levels of mitotic cell cycle regulators albeit to a lesser degree as compared to control cultures.In conclusion, our results assign a novel non-redundant function for HGF/c-Met signaling in regulation of G2/M gene expression program via maintaining a persistent Erk1/2 activation throughout liver regeneration

Heterogeneous contributions of change in population distribution of body mass index to change in obesity and underweight NCD Risk Factor Collaboration (NCD-RisC)

From 1985 to 2016, the prevalence of underweight decreased, and that of obesity and severe obesity increased, in most regions, with significant variation in the magnitude of these changes across regions. We investigated how much change in mean body mass index (BMI) explains changes in the prevalence of underweight, obesity, and severe obesity in different regions using data from 2896 population-based studies with 187 million participants. Changes in the prevalence of underweight and total obesity, and to a lesser extent severe obesity, are largely driven by shifts in the distribution of BMI, with smaller contributions from changes in the shape of the distribution. In East and Southeast Asia and sub-Saharan Africa, the underweight tail of the BMI distribution was left behind as the distribution shifted. There is a need for policies that address all forms of malnutrition by making healthy foods accessible and affordable, while restricting unhealthy foods through fiscal and regulatory restrictions

Heterogeneity within Animal Thioredoxin Reductases

Animal thioredoxin reductases (TRs) are selenocysteine- containing flavoenzymes that utilize NADPH for reduction of thioredoxins and other protein and nonprotein substrates. Three types of mammalian TRs are known, with TR1 being a cytosolic enzyme, and TR3, a mitochondrial enzyme. Previously characterized TR1 and TR3 occurred as homodimers of 55–57-kDa subunits. We report here that TR1 isolated from mouse liver, mouse liver tumor, and a human T-cell line exhibited extensive heterogeneity as detected by electrophoretic, immunoblot, and mass spectrometry analyses. In particular, a 67-kDa band of TR1 was detected. Furthermore, a novel form of mouse TR1 cDNA encoding a 67-kDa selenoprotein subunit with an additional N-terminal sequence was identified. Subsequent homology analyses revealed three distinct isoforms of mouse and rat TR1 mRNA. These forms differed in 5’ sequences that resulted from the alternative use of the first three exons but had common downstream sequences. Similarly, expression of multiple mRNA forms was observed for human TR3 and Drosophila TR. In these genes, alternative first exon splicing resulted in the formation of predicted mitochondrial and cytosolic proteins. In addition, a human TR3 gene overlapped with the gene for catechol-Omethyltransferase (COMT) on a complementary DNA strand, such that mitochondrial TR3 and membrane-bound COMT mRNAs had common first exon sequences; however, transcription start sites for predicted cytosolic TR3 and soluble COMT forms were separated by ~30 kilobases. Thus, this study demonstrates a remarkable heterogeneity within TRs, which, at least in part, results from evolutionary conserved genetic mechanisms employing alternative first exon splicing. Multiple transcription start sites within TR genes may be relevant to complex regulation of expression and/or organelle- and cell type-specific location of animal thioredoxin reductases

Genomic modeling of tumor onset and progression in a mouse model of aggressive human liver cancer.

International audienceA comprehensive understanding of molecular mechanisms driving cancer onset and progression should provide a basis for improving early diagnosis, biomarker discovery and treatment options. A key value of genetically engineered mice for modeling human cancer is the possibility to analyze the entire process of tumor development. Here, we applied functional genomics approach to study step-by-step development of hepatocellular carcinoma (HCC) in the c-Myc/Tgfα transgenic mouse model of aggressive human liver cancer. We report that coexpression of c-Myc and Tgfα induces progressive and cumulative transcriptional alterations in the course of liver oncogenesis. Functional analysis of deregulated genes at the early stage of HCC disease supports a model of active hepatocyte proliferation on the background of chronic oxidative stress generated by a general metabolic disorder. In addition, early and persistent deregulation of numerous immune-related genes suggested that disruption of immune microenvironment may contribute to oncogenic process in this model of accelerated liver carcinogenesis. In particularly, by flow cytometry analysis, we found loss of the major histocompatibility complex class I expression in dysplastic hepatocytes followed by upregulation of numerous activating ligands for natural killer (NK) cells concomitant with a drastic decrease in hepatic NK cell frequency. In conclusion, our study provides a comprehensive characterization of sequential molecular changes during a stepwise progression of preneoplastic lesions toward HCC and highlights a critical role of metabolic disorders and innate immunity at the early stages of liver cancer

Acceleration of c-myc-Induced Hepatocarcinogenesis by Co-Expression of Transforming Growth Factor (TGF)-α in Transgenic Mice Is Associated with TGF-β1 Signaling Disruption

We have previously shown in transgenic mice that transforming growth factor (TGF)-α dramatically enhances c-myc-induced hepatocarcinogenesis by promoting proliferation and survival of hepatocellular carcinoma (HCC) cells. As transgenic livers display increased levels of mature TGF-β1 from the early stages of hepatocarcinogenesis, we have now assessed whether impairment of TGF-β1 signaling contributes to the deregulation of cell cycle progression and apoptosis observed during this process. Focal preneoplastic lesions lacking expression of TGF-β receptor type II (TβRII) were detected in c-myc/TGF-α but not in c-myc livers. In c-myc/TGF-α mice, 40% (2/5) of adenomas and 90% (27/30) of HCCs showed down-regulation of TβRII expression in comparison with 11% (2/18) of adenomas and 47% (14/30) of HCCs in c-myc mice. Down-regulation of the TGF-β1-inducible p15(INK4B) mRNA and reduced apoptotic rates in TβRII-negative HCCs further indicated the disruption of TGF-β1 signaling. Furthermore, both TβRII-negative and -positive c-myc TGF-α HCCs, but not c-myc HCCs, were characterized by decreased levels of the cell cycle inhibitor p27. These results suggest 1) an inverse correlation of decreased p27 expression with the particularly strong expression of TGF-α in these lesions, consistent with the capacity of TGF-α signaling to post-transcriptionally regulate p27, and 2) the presence of alternative, downstream defects of TGF-β1 signaling in c-myc/TGF-α HCCs that may impair the growth-inhibitory response to TGF-β1. Thus, the accelerated neoplastic development in c-myc/TGF-α mice is associated with an early and frequent occurrence of TβRII-negative lesions and with reduced levels of p27 in HCC cells, indicating that disruption of TGF-β1 responsiveness may play a crucial role in the enhancement of c-myc-induced hepatocarcinogenesis by TGF-α

Vitamin E down-modulates iNOS and NADPH oxidase in c-Myc/TGF-alpha transgenic mouse model of liver cancer

Background/Aims. Co-expression of c-Myc and TGF-α in the mouse liver accelerates hepatocarcinogenesis and enhances DNA damage due to chronic oxidative stress. Dietary supplementation with vitamin E (VE) inhibits hepatocarcinogenesis and reduces chromosomal alterations in the same mice. Here we investigated the sources of reactive oxygen species (ROS) production in c-Myc/TGF-α transgenic mice. Methods. Inducible nitric oxide synthase (iNOS) and NADPH oxidase levels were determined in c-Myc, TGF-α and c-Myc/TGF-α mice by RT-PCR, western blot analysis and immunohistochemistry. Results. iNOS and nitrotyrosines levels were higher in the three transgenic lines when compared with wild-type mice. Preneoplastic and neoplastic lesions from c-Myc, TGF-α and c-Myc/TGF-α transgenic mice displayed upregulation of NADPH oxidase subunits p47-, 67-phox, Rac1, HSP 70, and HO-1. Importantly, dietary supplementation with vitamin E abolished iNOS expression, lowered nitrotyrosines, p47-, p67-phox, and Rac1 levels, and suppressed HSP 70 and HO-1 proteins in c-Myc/TGF-α livers. Conclusions. The results suggest that iNOS and NADPH oxidase are involved in ROS generation during c-Myc/TGF-α hepatocarcinogenesis and are inhibited by VE treatment. The data provide additional evidence for the potential use of VE in treatment of chronic liver diseases and HCC prevention

Disregulation of E-cadherin in transgenic mouse models of liver cancer

E-cadherin is a cell–cell adhesion molecule that plays a pivotal role in the development and maintenance of cell polarity. Disruption of E-cadherin-mediated adhesion represents a key step toward the invasive phenotype in a variety of solid tumors, including hepatocellular carcinoma (HCC). Here, we investigate whether deregulation of E-cadherin occurs along the multistep process of hepatocarcinogenesis in transgenic mouse models, including c-Myc, E2F1, c-Myc/TGF-α and c-Myc/E2F1 mice. Liver tumors from the transgenic mouse lines could be divided into two categories based on E-cadherin levels. Of 28, 20 (71.4%) c-Myc HCCs showed marked reduction of E-cadherin expression when compared with wild-type livers. In contrast, all of c-Myc/TGF-α and the majority of E2F1 and c-myc/E2F1 preneoplastic and neoplastic lesions exhibited overexpression of E-cadherin. Downregulation of E-cadherin was associated with promoter hypermethylation in seven of 20 c-Myc HCCs (35%), while no loss of heterozygosity at the E-cadherin locus was detected. Nuclear accumulation of β-catenin did not correlate with E-cadherin downregulation. Furthermore, c-Myc HCCs with reduced E-cadherin displayed upregulation of hypoxia-inducible factor-1α and vascular endothelial growth factor proteins. Importantly, loss of E-cadherin was associated with increased cell proliferation and higher microvessel density in c-Myc tumors. Taken together, these data suggest that loss of E-cadherin might favor tumor progression in relatively more benign HCC from c-Myc transgenic mice by stimulating neoplastic proliferation and angiogenesis under hypoxic conditions