Increase of cell surface vimentin is associated with vimentin network disruption and subsequent stress-induced premature senescence in human chondrocytes

Accumulation of dysfunctional chondrocytes has detrimental consequences on the cartilagehomeostasis and is thus thought to play a crucial role during the pathogenesis of osteoarthritis(OA). However, the underlying mechanisms of phenotypical alteration in chondrocytes areincompletely understood. Here, we provide evidence that disruption of the intracellularvimentin network and consequent phenotypical alteration in human chondrocytes results in anexternalization of the intermediate filament. The presence of the so-called cell surfacevimentin (CSV) on chondrocytes was associated with the severity of tissue degeneration inclinical OA samples and was enhanced after mechanical injury of cartilage tissue. By meansof a doxorubicine-based in vitro model of stress-induced premature senescence (SIPS), wecould confirm the connection between cellular senescence and amount of CSV. AlthoughsiRNA-mediated silencing of CDKN2A clearly reduced the senescent phenotype as well asCSV levels of human chondrocytes, cellular senescence could not be completely reversed.Interestingly, knockdown of vimentin resulted in a SIPS-like phenotype and consequentlyincreased CSV. Therefore, we concluded that the integrity of the intracellular vimentinnetwork is crucial to maintain cellular function in chondrocytes. This assumption could beconfirmed by chemically- induced collapse of the vimentin network, which resulted in cellularstress and enhanced CSV expression. Regarding its biological function, CSV was found to beassociated with enhanced chondrocyte adhesion and plasticity. While osteogenic capacitiesseemed to be enhanced in chondrocytes expressing high levels of CSV, the chondrogenicpotential was clearly compromised. Overall, our study reinforces the importance of thevimentin network in maintenance of the chondrogenic phenotype and introduces CSV as anovel membrane-bound marker of dysfunctional chondrocytes.

Automated Capture and Analysis of Circulating Tumor Cells in Pediatric, Adolescent and Young Adult Patients with Central Nervous System Tumors

Tumors of the central nervous system (CNS) are the most common and lethal childhood malignancy. Detection of residual disease and longitudinal monitoring of treatment response in patients are challenging and rely on serial imaging. This current standard of care fails to detect microscopic disease or provide molecular characteristics of residual tumors. As such, there is dire need for minimally invasive liquid biopsy techniques. We have previously shown the high specificity of using cell surface vimentin (CSV) to identify circulating tumor cells (CTCs) from patients bearing various types of cancers. Here, we describe the first report of CTCs captured from peripheral blood samples in 58 pediatric CNS tumor patients. In this study, we used a CSV-coated cell capture chip, the Abnova CytoQuest automated CTC isolation system, to boost the CTC capture from pediatric patients with CNS tumors. We successfully isolated CTCs in six glioma patients using immunostaining of histone H3 lysine27-to-methionine (H3K27M) mutations which are highly expressed by this tumor. We show that CSV is a viable marker for CNS CTC isolation and that this is a feasible method for detecting microscopic disease. Larger-scale studies focusing on CTCs in pediatric CNS tumors to explore their diagnostic and prognostic value are warranted.

Vimentin as a Multifaceted Player and Potential Therapeutic Target in Viral Infections

Vimentin is an intermediate filament protein that plays key roles in integration of cytoskeletal functions, and therefore in basic cellular processes such as cell division and migration. Consequently, vimentin has complex implications in pathophysiology. Vimentin is required for a proper immune response, but it can also act as an autoantigen in autoimmune diseases or as a damage signal. Although vimentin is a predominantly cytoplasmic protein, it can also appear at extracellular locations, either in a secreted form or at the surface of numerous cell types, often in relation to cell activation, inflammation, injury or senescence. Cell surface targeting of vimentin appears to associate with the occurrence of certain posttranslational modifications, such as phosphorylation and/or oxidative damage. At the cell surface, vimentin can act as a receptor for bacterial and viral pathogens. Indeed, vimentin has been shown to play important roles in virus attachment and entry of severe acute respiratory syndrome-related coronavirus (SARS-CoV), dengue and encephalitis viruses, among others. Moreover, the presence of vimentin in specific virus-targeted cells and its induction by proinflammatory cytokines and tissue damage contribute to its implication in viral infection. Here, we recapitulate some of the pathophysiological implications of vimentin, including the involvement of cell surface vimentin in interaction with pathogens, with a special focus on its role as a cellular receptor or co-receptor for viruses. In addition, we provide a perspective on approaches to target vimentin, including antibodies or chemical agents that could modulate these interactions to potentially interfere with viral pathogenesis, which could be useful when multi-target antiviral strategies are needed.

Discovery of cell surface vimentin targeting mAb for direct disruption of GBM tumor initiating cells. Oncotarget. 2016;7:72021-72032. [PMID: 27713131 PMCID: PMC5342141 DOI: 10.18632/oncotarget.12458]

Intracellular vimentin overexpression has been associated with epithelial–mesenchymal transition, metastasis, invasion, and proliferation, but cell surface vimentin (CSV) is less understood. Furthermore, it remains unknown whether CSV can serve as a therapeutic target in CSV-expressing tumor cells. We found that CSV was present on glioblastoma multiforme (GBM) cancer stem cells and that CSV expression was associated with spheroid formation in those cells. A newly developed monoclonal antibody against CSV, 86C, specifically and significantly induced apoptosis and inhibited spheroid formation in GBM cells in vitro. The addition of 86C to GBM cells in vitro also led to rapid internalization of vimentin and decreased GBM cell viability. These findings were associated with an increase in caspase-3 activity, indicating activation of apoptosis. Finally, treatment with 86C inhibited GBM progression in vivo. In conclusion, CSV-expressing GBM cells have properties of tumor initiating cells, and targeting CSV with the monoclonal antibody 86C is a promising approach in the treatment of GBM.