Transglutaminase mediated asprosin oligomerization allows its tissue storage as fibers

Asprosin, the C-terminal furin cleavage product of profibrillin-1, was reported to act as a hormone that circulates at nanomolar levels and is recruited to the liver where it induces G protein-coupled activation of the cAMP-PKA pathway and stimulates rapid glucose release into the circulation. Although derived from profibrillin-1, a multidomain extracellular matrix glycoprotein with a ubiquitous distribution in connective tissues, little is known about the tissue distribution of asprosin. In the current view, asprosin is mainly produced by white adipose tissue from where it is released into the blood in monomeric form. Here, by employing newly generated specific asprosin antibodies we monitored the distribution pattern of asprosin in human and murine connective tissues such as placenta, and muscle. Thereby we detected the presence of asprosin positive extracellular fibers. Further, by screening established cell lines for asprosin synthesis we found that most cells derived from musculoskeletal tissues render asprosin into an oligomerized form. This oligomerization is facilitated by transglutaminase activity and requires an intact fibrillin fiber network for proper linear deposition. Our data suggest a new extracellular storage mechanism of asprosin in oligomerized form which may regulate its cellular bioavailability in tissues.

The potential of COVID-19 patients’ sera to cause antibody-dependent enhancement of infection and IL-6 production

Since the emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), many vaccine trials have been initiated. An important goal of vaccination is the development of neutralizing antibody (Ab) against SARS-CoV-2. However, the possible induction of antibody-dependent enhancement (ADE) of infection, which is known for other coronaviruses and dengue virus infections, is a particular concern in vaccine development. Here, we demonstrated that human iPS cell-derived, immortalized, and ACE2- and TMPRSS2-expressing myeloid cell lines are useful as host cells for SARS-CoV-2 infection. The established cell lines were cloned and screened based on their function in terms of susceptibility to SARS-CoV-2-infection or IL-6 productivity. Using the resulting K-ML2 (AT) clone 35 for SARS-CoV-2-infection or its subclone 35–40 for IL-6 productivity, it was possible to evaluate the potential of sera from severe COVID-19 patients to cause ADE and to stimulate IL-6 production upon infection with SARS-CoV-2.

Emerging Therapeutic Role of CDK Inhibitors in Targeting Cancer Stem Cells

Within a tumor, Cancer Stem Cells (CSCs) exists and own similar characteristics of a normal stem cell thus contributing towards aggressiveness of cancer by playing crucial role in tumor recurrence and metastasis capability. Various studies have been conducted to therapeutically target CSCs. One of the approaches include is to inhibit cell cycle progression in CSCs. Within last two decades cell cycle and role of various components in its regulation is firmly established. Cell cycle is regulated by Cyclin Dependent Kinases (CDK) bound to cyclin. CDK activity can be blocked by Cyclin-Dependent Kinase Inhibitors (CKIs) which can either bind cyclin/CDK complex or CDK alone and thus stops cell cycle. In this review various studies are discussed that have investigated the therapeutic role of CKIs in eradicating CSCs by inhibiting cell cycle. Overall, the analysis suggests that CKIs could be a potential therapeutic option in controlling CSCs populating in a tumor.

GSK-3 Inhibition is Cytotoxic in Glioma Stem Cells through Centrosome Destabilization and Enhances the Effect of Radiotherapy in Orthotopic Models

Background: Previous data on glycogen synthase kinase 3 (GSK-3) inhibition in cancer models support a cytotoxic effect with selectivity for tumor cells compared to normal tissue but the effect of these inhibitors in glioma has not been widely studied. Here, we investigate their potential as cytotoxics in glioma. Methods: We assessed the effect of pharmacologic GSK-3 inhibition on established (U87, U251) and patient-derived (GBM1, GBM4) glioblastoma (GBM) cell lines using cytotoxicity assays as well as undertaking a detailed investigation of the effect on cell cycle, mitosis, and centrosome biology. We also assessed drug uptake and efficacy of GSK-3 inhibition alone and in combination with radiation in xenograft models. Results: Using the selective GSK-3 inhibitor AZD2858, we demonstrated single agent cytotoxicity in two patient-derived glioma cell lines (GBM1, GBM4) and two established cell lines (U251 and U87) with IC50 in the low micromolar range promoting centrosome disruption, failed mitosis, and S-phase arrest. Glioma xenografts exposed to AZD2858 also showed growth delay compared to untreated controls. Combined treatment with radiation increased the cytotoxic effect of clinical radiation doses in vitro and in orthotopic glioma xenografts. Conclusions: These data suggest that GSK-3 inhibition promotes cell death in glioma through disrupting centrosome function and promoting mitotic failure and that AZD2858 is an effective adjuvant to radiation at clinical doses.

Efferocytosis: An Interface between Apoptosis and Pathophysiology

Several cell death modes, each with a unique feature and mode of inducing cell death have been established. Cell death occurring under physiological conditions is primarily caused by apoptosis, which is a non-inflammatory or silent process, whereas necroptosis or pyroptosis is triggered by pathogen invasion, which stimulates the immune system and induces inflammation. In physiology, clearing dead cells and associated cellular debris is necessary since billions of cells die during mammalian embryogenesis and every day in adult organisms. For degradation, dead cells produced by apoptosis are quickly engulfed by macrophages. This chapter will present a description of the phagocytosis of dead and dying cells, by a process known as efferocytosis. Macrophages and, to a lesser degree, other ‘professional’ phagocytes (such as monocytes and dendritic cells) and ‘non-professional’ phagocytes, such as epithelial cells, conduct efferocytosis. Recent discoveries have shed light on this mechanism and how it works to preserve homeostasis of tissue, repair of tissue and health of the organism. Caspases are a large family of proteases of cysteine acting in cascades. A cascade leading to activation of caspase 3 mediates apoptosis and is responsible for killing cells, hiring macrophages, and presenting a “eat me” signal(s). If macrophages do not effectively engulf apoptotic cells, they undergo secondary necrosis and release intracellular materials that reflect a molecular pattern associated with injury, which can lead to autoimmune diseases. Here, the processes of efferocytosis are illustrated and the pathophysiological effects that which occur when this phase is abrogated are highlighted.

A Cell-Based Platform for the Investigation of Immunoproteasome Subunit β5i Expression and Biology of β5i-Containing Proteasomes

The degradation of most intracellular proteins is a dynamic and tightly regulated process performed by proteasomes. To date, different forms of proteasomes have been identified. Currently the role of non-constitutive proteasomes (immunoproteasomes (iPs) and intermediate proteasomes (intPs)) has attracted special attention. Here, using a CRISPR-Cas9 nickase technology, four cell lines: histiocytic lymphoma, colorectal adenocarcinoma, cervix adenocarcinoma, and hepatocarcinoma were modified to express proteasomes with mCherry-tagged β5i subunit, which is a catalytic subunit of iPs and intPs. Importantly, the expression of the chimeric gene in modified cells is under the control of endogenous regulatory mechanisms and is increased following IFN-γ and/or TNF-α stimulation. Fluorescent proteasomes retain catalytic activity and are distributed within the nucleus and cytoplasm. RNAseq reveals marginal differences in gene expression profiles between the modified and wild-type cell lines. Predominant metabolic pathways and patterns of expressed receptors were identified for each cell line. Using established cell lines, we demonstrated that anti-cancer drugs Ruxolitinib, Vincristine and Gefitinib stimulated the expression of β5i-containing proteasomes, which might affect disease prognosis. Taken together, obtained cell lines can be used as a platform for real-time studies of immunoproteasome gene expression, localization of iPs and intPs, interaction of non-constitutive proteasomes with other proteins, proteasome trafficking and many other aspects of proteasome biology in living cells. Moreover, the established platform might be especially useful for fast and large-scale experiments intended to evaluate the effects of different conditions including treatment with various drugs and compounds on the proteasome pool.

EXTH-05. TUMOR TREATING FIELDS IN COMBINATION WITH THE TERT-INHIBITOR ERIBULIN HAVE SYNERGISTIC ANTIPROLIFERATIVE EFFECTS ON HUMAN GLIOBLASTOMA CELLS

OBJECTIVE Combination therapy, a treatment modality that combines two or more therapeutic agents, is a cornerstone of cancer therapy. The optimal combination therapy for Tumor Treating Fields (TTFields) in glioblastoma (GBM) treatment is unknown. The aim of our study was to analyze, the effects of the TERT-inhibitor eribulin in combination with TTFields on human GBM cells. METHODS Human GBM cells of the established cell lines U87, A172 and U251, and two patient-derived cell lines, were treated with eribulin monotherapy, TTFields monotherapy, or both modalities together. After 72 hours of therapy, cell counts were measured and clonogenic assays were performed. Annexin staining and fluorescence-activated cell scanning (FACS) was used to analyze cell death. RESULTS Overall surviving fractions were 39.8±11.0% for eribulin monotherapy, 32.2±23.9% for TTFields monotherapy, and 10.9±9.9% for the combined treatment. Mean observed annexin positive fractions were 11.2±8.2% (control), 28.6±9.7% (eribulin), 34.8±8.1% (TTFields), and 78.1±13.5% (combination), respectively. The mean clonogenic fractions over all cell lines were 25.9±7.8% for eribulin and 46.4±12.9% for TTFields. For the combination therapy, a synergistic effect with a decreased mean of 3.6% clonogenic fractions was observed. CONCLUSION Eribulin increases cell death and reduces clonogenicity our experiments. Additionally, a synergistic effect of the combined treatment of TTFields and eribulin synergistic was observed. Eribulin in combination with TTFields could be a new effective therapy for GBM.

Rapid production of SaCas9 in plant-based cell-free lysate for activity testing

Cas9 nucleases have become the most versatile tool for genome editing projects in a broad range of organisms. The recombinant production of Cas9 nuclease is desirable for in vitro activity assays or the preparation of ribonucleoproteins (RNPs) for DNA-free genome editing approaches. For the rapid production of Cas9, we explored the use of a recently established cell-free lysate from tobacco (Nicotiana tabacum L.) BY-2 cells. Using this system, the 130-kDa Cas9 nuclease from Staphylococcus aureus (SaCas9) was produced and subsequently purified via affinity chromatography. The purified apoenzyme was supplemented with ten different sgRNAs, and the nuclease activity was confirmed by the linearization of plasmid DNA containing cloned DNA target sequences.

Biobanked Glioblastoma Patient-Derived Organoids as a Precision Medicine Model to Study Inhibition of Invasion

Glioblastoma (GBM) is highly resistant to treatment and invasion into the surrounding brain is a cancer hallmark that leads to recurrence despite surgical resection. With the emergence of precision medicine, patient-derived 3D systems are considered potentially robust GBM preclinical models. In this study, we screened a library of 22 anti-invasive compounds (i.e., NF-kB, GSK-3-B, COX-2, and tubulin inhibitors) using glioblastoma U-251 MG cell spheroids. We evaluated toxicity and invasion inhibition using a 3D Matrigel invasion assay. We next selected three compounds that inhibited invasion and screened them in patient-derived glioblastoma organoids (GBOs). We developed a platform using available macros for FIJI/ImageJ to quantify invasion from the outer margin of organoids. Our data demonstrated that a high-throughput invasion screening can be done using both an established cell line and patient-derived 3D model systems. Tubulin inhibitor compounds had the best efficacy with U-251 MG cells, however, in ex vivo patient organoids the results were highly variable. Our results indicate that the efficacy of compounds is highly related to patient intra and inter-tumor heterogeneity. These results indicate that such models can be used to evaluate personal oncology therapeutic strategies.