👤 Thomas Keil

Snail and Zeb1 have been suggested as markers for the hybrid/mixed epithelial (E)/mesenchymal (M) state of cancer cells. Such cancer cells co-express E- and M-specific transcripts and possess cancer stem cell properties. M13HS-2/-8 tumor hybrid clones derived from human M13SV1-EGFP-Neo breast epithelial cells and human HS578T-Hyg breast cancer cells exhibited co-expression of Snail and Zeb1. To explore the impact of Snail on stemness/epithelial-to-mesenchymal transition (EMT)-related properties in M13HS-2/-8 tumor hybrid clones, Snail was knocked out (KO) using CRISPR/Cas9. Mammosphere formation, colony formation, Western blot analyses, cell migration, and invasion assays were conducted for the characterization of Snail knockout cells. Interestingly, Snail-KO in M13SV1-EGFP-Neo cells resulted in the up-regulation of vimentin and N-cadherin, suggesting EMT induction, which was associated with a significantly enhanced colony formation capacity. In contrast, EMT marker pattern and colony formation capacities of M13HS-2/-8 Snail-KO tumor hybrid clones remained unchanged. Notably, the mammosphere formation capacities of M13HS-2/-8 Snail-KO tumor hybrid clones were significantly reduced. The migratory behavior of all Snail-KO cells was not altered compared with their wild-type counterparts. In contrast, M13HS-2 hybrids and their M13HS-2 Snail-KO variant exhibited a markedly enhanced invasive capacity. Therefore, Snail plays a role as a mediator of stemness properties rather than mediating EMT. Show less

Post-COVID syndrome (PCS) is an important sequela of COVID-19, characterised by symptom persistence for >3 months, post-acute symptom development, and worsening of pre-existing comorbidities. The causes and public health impact of PCS are still unclear, not least for the lack of efficient means to assess the presence and severity of PCS. COVIDOM is a population-based cohort study of polymerase chain reaction (PCR) confirmed cases of SARS-CoV-2 infection, recruited through public health authorities in three German regions (Kiel, Berlin, Würzburg) between November 15, 2020 and September 29, 2021. Main inclusion criteria were (i) a PCR confirmed SARS-CoV-2 infection and (ii) a period of at least 6 months between the infection and the visit to the COVIDOM study site. Other inclusion criteria were written informed consent and age ≥18 years. Key exclusion criterion was an acute reinfection with SARS-CoV-2. Study site visits included standardised interviews, in-depth examination, and biomaterial procurement. In sub-cohort Kiel-I, a PCS (severity) score was developed based upon 12 long-term symptom complexes. Two validation sub-cohorts (Würzburg/Berlin, Kiel-II) were used for PCS score replication and identification of clinically meaningful predictors. This study is registered at clinicaltrials.gov (NCT04679584) and at the German Registry for Clinical Studies (DRKS, DRKS00023742). In Kiel-I ( PCS severity can be quantified by an easy-to-use symptom-based score reflecting acute phase disease burden and general psychological predisposition. The PCS score thus holds promise to facilitate the clinical diagnosis of PCS, scientific studies of its natural course, and the development of therapeutic interventions. The COVIDOM study is funded by the Network University Medicine (NUM) as part of the National Pandemic Cohort Network (NAPKON). Show less

Mitogen-activated protein kinase (MAPK) signaling determines crucial cell fate decisions in most cell types, and mediates cellular transformation in many types of cancer. The activity of MAPK is controlled by reversible phosphorylation, and the quantitative characteristics of MAPK activation determine the cellular response. Many systems biological studies have analyzed the activation kinetics and the dose-response behavior of the MAPK signaling pathway. Here we investigate how the pathway activity is controlled by transcriptional feedback loops. Initially, we predict that MAPK signaling regulates phosphatases, by integrating promoter sequence data and ontology-based classification of gene function. From this, we deduce that MAPK signaling might be controlled by transcriptional negative feedback regulation via dual-specificity phosphatases (DUSPs), and implement a mathematical model to further test this hypothesis. Using time-resolved measurements of pathway activity and gene expression, we employ a model selection approach, and select DUSP6 as a highly likely candidate for shaping the activity of the MAPK pathway during cellular transformation caused by oncogenic RAS. Two predictions from the model were confirmed: first, feedback regulation requires that DUSP6 mRNA and protein are unstable; and second, the activation kinetics of MAPK are ultrasensitive. Taken together, an integrated systems biological approach reveals that transcriptional negative feedback controls the kinetics and the extent of MAPK activation under both physiological and pathological conditions. Show less