The BRAF pseudogene functions as a competitive endogenous RNA and induces lymphoma in vivo

SummaryResearch over the past decade has suggested important roles for pseudogenes in physiology and disease. In vitro experiments demonstrated that pseudogenes contribute to cell transformation through several mechanisms. However, in vivo evidence for a causal role of pseudogenes in cancer development is lacking. Here, we report that mice engineered to overexpress either the full-length murine B-Raf pseudogene Braf-rs1 or its pseudo “CDS” or “3′ UTR” develop an aggressive malignancy resembling human diffuse large B cell lymphoma. We show that Braf-rs1 and its human ortholog, BRAFP1, elicit their oncogenic activity, at least in part, as competitive endogenous RNAs (ceRNAs) that elevate BRAF expression and MAPK activation in vitro and in vivo. Notably, we find that transcriptional or genomic aberrations of BRAFP1 occur frequently in multiple human cancers, including B cell lymphomas. Our engineered mouse models demonstrate the oncogenic potential of pseudogenes and indicate that ceRNA-mediated microRNA sequestration may contribute to the development of cancer

PTEN Controls Junction Lengthening and Stability during Cell Rearrangement in Epithelial Tissue

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Comparison of inhibitory effects of irreversible and reversible Btk inhibitors on platelet function

All irreversible Bruton tyrosine kinase (Btk) inhibitors including ibrutinib and acalabrutinib induce platelet dysfunction and increased bleeding risk. New reversible Btk inhibitors were developed, like MK‐1026. The mechanism underlying increased bleeding tendency with Btk inhibitors remains unclear. We investigated the effects of ibrutinib, acalabrutinib and MK‐1026 on platelet function in healthy volunteers, patients and Btk‐deficient mice, together with off‐target effects on tyrosine kinase phosphorylation. All inhibitors suppressed GPVI‐ and CLEC‐2‐mediated platelet aggregation, activation and secretion in a dose‐dependent manner. Only ibrutinib inhibited thrombus formation on vWF‐co‐coated surfaces, while on collagen this was not affected. In blood from Btk‐deficient mice, collagen‐induced thrombus formation under flow was reduced, but preincubation with either inhibitor was without additional effects. MK‐1026 showed less off‐target effects upon GPVI‐induced TK phosphorylation as compared to ibrutinib and acalabrutinib. In ibrutinib‐treated patients, GPVI‐stimulated platelet activation, and adhesion on vWF‐co‐coated surfaces were inhibited, while CLEC‐2 stimulation induced variable responses. The dual inhibition of GPVI and CLEC‐2 signalling by Btk inhibitors might account for the increased bleeding tendency, with ibrutinib causing more high‐grade bleedings due to additional inhibition of platelet‐vWF interaction. As MK‐1026 showed less off‐target effects and only affected activation of isolated platelets, it might be promising for future treatment

The Platelet Lipidome Is Altered in Patients with COVID-19 and Correlates with Platelet Reactivity

Background  Activated platelets have been implicated in the proinflammatory and prothrombotic phenotype of coronavirus disease 2019 (COVID-19). While it is increasingly recognized that lipids have important structural and signaling roles in platelets, the lipidomic landscape of platelets during infection has remained unexplored. Objective  To investigate the platelet lipidome of patients hospitalized for COVID-19. Methods  We performed untargeted lipidomics in platelets of 25 patients hospitalized for COVID-19 and 23 noninfectious controls with similar age and sex characteristics, and with comparable comorbidities. Results  Twenty-five percent of the 1,650 annotated lipids were significantly different between the groups. The significantly altered part of the platelet lipidome mostly comprised lipids that were less abundant in patients with COVID-19 (20.4% down, 4.6% up, 75% unchanged). Platelets from COVID-19 patients showed decreased levels of membrane plasmalogens, and a distinct decrease of long-chain, unsaturated triacylglycerols. Conversely, platelets from patients with COVID-19 displayed class-wide higher abundances of bis(monoacylglycero)phosphate and its biosynthetic precursor lysophosphatidylglycerol. Levels of these classes positively correlated with ex vivo platelet reactivity-as measured by P-selectin expression after PAR1 activation-irrespective of disease state. Conclusion  Taken together, this investigation provides the first exploration of the profound impact of infection on the human platelet lipidome, and reveals associations between the lipid composition of platelets and their reactivity. These results warrant further lipidomic research in other infections and disease states involving platelet pathophysiology

The host response in different aetiologies of community-acquired pneumonia

Background: Community-acquired pneumonia (CAP) can be caused by a variety of pathogens, of which Streptococcus pneumoniae, Influenza and currently SARS-CoV-2 are the most common. We sought to identify shared and pathogen-specific host response features by directly comparing different aetiologies of CAP. Methods: We measured 72 plasma biomarkers in a cohort of 265 patients hospitalized for CAP, all sampled within 48 hours of admission, and 28 age-and sex matched non-infectious controls. We stratified the biomarkers into several pathophysiological domains- antiviral response, vascular response and function, coagulation, systemic inflammation, and immune checkpoint markers. We directly compared CAP caused by SARS-CoV-2 (COVID-19, n=39), Streptococcus pneumoniae (CAP-strep, n=27), Influenza (CAP-flu, n=22) and other or unknown pathogens (CAP-other, n=177). We adjusted the comparisons for age, sex and disease severity scores. Findings: Biomarkers reflective of a stronger cell-mediated antiviral response clearly separated COVID-19 from other CAPs (most notably granzyme B). Biomarkers reflecting activation and function of the vasculature showed endothelial barrier integrity was least affected in COVID-19, while glycocalyx degradation and angiogenesis were enhanced relative to other CAPs. Notably, markers of coagulation activation, including D-dimer, were not different between the CAP groups. Ferritin was most increased in COVID-19, while other systemic inflammation biomarkers such as IL-6 and procalcitonin were highest in CAP-strep. Immune checkpoint markers showed distinctive patterns in viral and non-viral CAP, with highly elevated levels of Galectin-9 in COVID-19. Interpretation: Our investigation provides insight into shared and distinct pathophysiological mechanisms in different aetiologies of CAP, which may help guide new pathogen-specific therapeutic strategies. Funding: This study was financially supported by the Dutch Research Council, the European Commission and the Netherlands Organization for Health Research and Development

The host response in different aetiologies of community-acquired pneumonia

Background: Community-acquired pneumonia (CAP) can be caused by a variety of pathogens, of which Streptococcus pneumoniae, Influenza and currently SARS-CoV-2 are the most common. We sought to identify shared and pathogen-specific host response features by directly comparing different aetiologies of CAP. Methods: We measured 72 plasma biomarkers in a cohort of 265 patients hospitalized for CAP, all sampled within 48 hours of admission, and 28 age-and sex matched non-infectious controls. We stratified the biomarkers into several pathophysiological domains- antiviral response, vascular response and function, coagulation, systemic inflammation, and immune checkpoint markers. We directly compared CAP caused by SARS-CoV-2 (COVID-19, n=39), Streptococcus pneumoniae (CAP-strep, n=27), Influenza (CAP-flu, n=22) and other or unknown pathogens (CAP-other, n=177). We adjusted the comparisons for age, sex and disease severity scores. Findings: Biomarkers reflective of a stronger cell-mediated antiviral response clearly separated COVID-19 from other CAPs (most notably granzyme B). Biomarkers reflecting activation and function of the vasculature showed endothelial barrier integrity was least affected in COVID-19, while glycocalyx degradation and angiogenesis were enhanced relative to other CAPs. Notably, markers of coagulation activation, including D-dimer, were not different between the CAP groups. Ferritin was most increased in COVID-19, while other systemic inflammation biomarkers such as IL-6 and procalcitonin were highest in CAP-strep. Immune checkpoint markers showed distinctive patterns in viral and non-viral CAP, with highly elevated levels of Galectin-9 in COVID-19. Interpretation: Our investigation provides insight into shared and distinct pathophysiological mechanisms in different aetiologies of CAP, which may help guide new pathogen-specific therapeutic strategies. Funding: This study was financially supported by the Dutch Research Council, the European Commission and the Netherlands Organization for Health Research and Development