Polarized hepatocytes expressing hyperactive Ha-Ras adopt an invasive and metastatic phenotype in cooperation with transforming growth factor (TGF)-b. This dramatic increase in malignancy is displayed by an epithelial to mesenchymal transition (EMT), which mimics the TGFb-mediated progression of human hepatocellular carcinomas. In culture, hepatocellular EMT occurs highly synchronously, facilitating the analysis of molecular events underlying the various stages of this process. Here, we show that in response to TGF-b, phosphorylated Smads rapidly translocated into the nucleus and activated transcription of target genes such as E-cadherin repressors of the Snail superfamily, causing loss of cell adhesion. Within the TGF-b superfamily of cytokines, TGF-b1, -b2 and -b3 were specific for the induction of hepatocellular EMT. Expression profiling of EMT kinetics revealed 78 up-and 235 downregulated genes, which preferentially modulate metabolic activities, extracellular matrix composition, transcriptional activities and cell survival. Independent of the genetic background, platelet-derived growth factor (PDGF)-A ligand and both PDGF receptor subunits were highly elevated, together with autocrine secretion of bioactive PDGF. Interference with PDGF signalling by employing hepatocytes expressing the dominant-negative PDGF-a receptor revealed decreased TGF-b-induced migration in vitro and efficient suppression of tumour growth in vivo. In conclusion, these results provide evidence for a crucial role of PDGF in TGF-bmediated tumour progression of hepatocytes and suggest PDGF as a target for therapeutic intervention in liver cancer.
Five lipoxygenase (5-LO) is the first committed enzyme in the metabolic pathway leading to the synthesis of the leukotrienes. We examined genomic DNA isolated from 25 normal subjects and 31 patients with asthma (6 of whom had aspirin-sensitive asthma) for mutations in the known transcription factor binding regions and
The cooperation of Ras -extracellular signal-regulated kinase/mitogen-activated protein kinase and transforming growth factor (TGF)-b signaling provokes an epithelial to mesenchymal transition (EMT) of differentiated p19 ARF null hepatocytes, which is accompanied by a shift in malignancy and gain of metastatic properties. Upon EMT, TGF-b induces the secretion and autocrine regulation of platelet-derived growth factor (PDGF) by upregulation of PDGF-A and both PDGF receptors. Here, we demonstrate by loss-of-function analyses that PDGF provides adhesive and migratory properties in vitro as well as proliferative stimuli during tumor formation. PDGF signaling resulted in the activation of phosphatidylinositol-3 kinase, and furthermore associated with nuclear b-catenin accumulation upon EMT. Hepatocytes expressing constitutively active b-catenin or its negative regulator Axin were employed to study the impact of nuclear b-catenin. Unexpectedly, active b-catenin failed to accelerate proliferation during tumor formation, but in contrast, correlated with growth arrest. Nuclear localization of b-catenin was accompanied by strong expression of the Cdk inhibitor p16INK4A and the concomitant induction of the b-catenin target genes cyclin D1 and c-myc. In addition, active b-catenin revealed protection of malignant hepatocytes against anoikis, which provides a prerequisite for the dissemination of carcinoma. From these data, we conclude that TGF-b acts tumor progressive by induction of PDGF signaling and subsequent activation of bcatenin, which endows a subpopulation of neoplastic hepatocytes with features of cancer stem cells.
BackgroundThe effects of neuromuscular electrical stimulation (NMES) in critically ill patients after cardiothoracic surgery are unknown. The objectives were to investigate whether NMES prevents loss of muscle layer thickness (MLT) and strength and to observe the time variation of MLT and strength from preoperative day to hospital discharge.MethodsIn this randomized controlled trial, 54 critically ill patients were randomized into four strata based on the SAPS II score. Patients were blinded to the intervention. In the intervention group, quadriceps muscles were electrically stimulated bilaterally from the first postoperative day until ICU discharge for a maximum of 14 days. In the control group, the electrodes were applied, but no electricity was delivered. The primary outcomes were MLT measured by ultrasonography and muscle strength evaluated with the Medical Research Council (MRC) scale. The secondary functional outcomes were average mobility level, FIM score, Timed Up and Go Test and SF-12 health survey. Additional variables of interest were grip strength and the relation between fluid balance and MLT. Linear mixed models were used to assess the effect of NMES on MLT, MRC score and grip strength.ResultsNMES had no significant effect on MLT. Patients in the NMES group regained muscle strength 4.5 times faster than patients in the control group. During the first three postoperative days, there was a positive correlation between change in MLT and cumulative fluid balance (r = 0.43, P = 0.01). At hospital discharge, all patients regained preoperative levels of muscle strength, but not of MLT. Patients did not regain their preoperative levels of average mobility (P = 0.04) and FIM score (P = 0.02) at hospital discharge, independent of group allocation.ConclusionsNMES had no effect on MLT, but was associated with a higher rate in regaining muscle strength during the ICU stay. Regression of intramuscular edema during the ICU stay interfered with measurement of changes in MLT. At hospital discharge patients had regained preoperative levels of muscle strength, but still showed residual functional disability and decreased MLT compared to pre-ICU levels in both groups.Trial registrationClinicaltrials.gov identifier NCT02391103. Registered on 7 March 2015.Electronic supplementary materialThe online version of this article (doi:10.1186/s13054-016-1199-3) contains supplementary material, which is available to authorized users.
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