Zika Virus Targets Glioblastoma Stem Cells through a SOX2-Integrin αvβ5 Axis

Understanding the immunosuppressive microenvironment of glioma: mechanistic insights and clinical perspectives

Glioblastoma (GBM), the predominant and primary malignant intracranial tumor, poses a formidable challenge due to its immunosuppressive microenvironment, thereby confounding conventional therapeutic interventions. Despite the established treatment regimen comprising surgical intervention, radiotherapy, temozolomide administration, and the exploration of emerging modalities such as immunotherapy and integration of medicine and engineering technology therapy, the efficacy of these approaches remains constrained, resulting in suboptimal prognostic outcomes. In recent years, intensive scrutiny of the inhibitory and immunosuppressive milieu within GBM has underscored the significance of cellular constituents of the GBM microenvironment and their interactions with malignant cells and neurons. Novel immune and targeted therapy strategies have emerged, offering promising avenues for advancing GBM treatment. One pivotal mechanism orchestrating immunosuppression in GBM involves the aggregation of myeloid-derived suppressor cells (MDSCs), glioma-associated macrophage/microglia (GAM), and regulatory T cells (Tregs). Among these, MDSCs, though constituting a minority (4-8%) of CD45+ cells in GBM, play a central component in fostering immune evasion and propelling tumor progression, angiogenesis, invasion, and metastasis. MDSCs deploy intricate immunosuppressive mechanisms that adapt to the dynamic tumor microenvironment (TME). Understanding the interplay between GBM and MDSCs provides a compelling basis for therapeutic interventions. This review seeks to elucidate the immune regulatory mechanisms inherent in the GBM microenvironment, explore existing therapeutic targets, and consolidate recent insights into MDSC induction and their contribution to GBM immunosuppression. Additionally, the review comprehensively surveys ongoing clinical trials and potential treatment strategies, envisioning a future where targeting MDSCs could reshape the immune landscape of GBM. Through the synergistic integration of immunotherapy with other therapeutic modalities, this approach can establish a multidisciplinary, multi-target paradigm, ultimately improving the prognosis and quality of life in patients with GBM.

Novel Clinical Trials and Approaches in the Management of Glioblastoma

PURPOSE OF REVIEW

The purpose of this review is to discuss a wide variety of novel therapies recently studied or actively undergoing study in patients with glioblastoma. This review also discusses current and future strategies for improving clinical trial design in patients with glioblastoma to maximize efficacy in discovering effective treatments.

RECENT FINDINGS

Over the years, there has been significant expansion in therapy modalities studied in patients with glioblastoma. These therapies include, but are not limited to, targeted molecular therapies, DNA repair pathway targeted therapies, immunotherapies, vaccine therapies, and surgically targeted radiotherapies. Glioblastoma is the most common malignant primary brain tumor in adults and unfortunately remains with poor overall survival following the current standard of care. Given the dismal prognosis, significant clinical and research efforts are ongoing with the goal of improving patient outcomes and enhancing quality and quantity of life utilizing a wide variety of novel therapies.

Zika Virus: A Neurotropic Warrior against High-Grade Gliomas-Unveiling Its Potential for Oncolytic Virotherapy

Gliomas account for approximately 75-80% of all malignant primary tumors in the central nervous system (CNS), with glioblastoma multiforme (GBM) considered the deadliest. Despite aggressive treatment involving a combination of chemotherapy, radiotherapy, and surgical intervention, patients with GBM have limited survival rates of 2 to 5 years, accompanied by a significant decline in their quality of life. In recent years, novel management strategies have emerged, such as immunotherapy, which includes the development of vaccines or T cells with chimeric antigen receptors, and oncolytic virotherapy (OVT), wherein wild type (WT) or genetically modified viruses are utilized to selectively lyse tumor cells. In vitro and in vivo studies have shown that the Zika virus (ZIKV) can infect glioma cells and induce a robust oncolytic activity. Consequently, interest in exploring this virus as a potential oncolytic virus (OV) for high-grade gliomas has surged. Given that ZIKV actively circulates in Colombia, evaluating its neurotropic and oncolytic capabilities holds considerable national and international importance, as it may emerge as an alternative for treating highly complex gliomas. Therefore, this literature review outlines the generalities of GBM, the factors determining ZIKV's specific tropism for nervous tissue, and its oncolytic capacity. Additionally, we briefly present the progress in preclinical studies supporting the use of ZIKV as an OVT for gliomas.

Natural Killer Cell Mechanosensing in Solid Tumors

Natural killer (NK) cells, which are an exciting alternative cell source for cancer immunotherapies, must sense and respond to their physical environment to traffic to and eliminate cancer cells. Herein, we review the mechanisms by which NK cells receive mechanical signals and explore recent key findings regarding the impact of the physical characteristics of solid tumors on NK cell functions. Data suggest that different mechanical stresses present in solid tumors facilitate NK cell functions, especially infiltration and degranulation. Moreover, we review recent engineering advances that can be used to systemically study the role of mechanical forces on NK cell activity. Understanding the mechanisms by which NK cells interpret their environment presents potential targets to enhance NK cell immunotherapies for the treatment of solid tumors.

Current approaches in glioblastoma multiforme immunotherapy

Glioblastoma multiform (GBM) is the most prevalent CNS (central nervous system) tumor in adults, with an average survival length shorter than 2 years and rare metastasis to organs other than CNS. Despite extensive attempts at surgical resecting, the inherently permeable nature of this disease has rendered relapse nearly unavoidable. Thus, immunotherapy is a feasible alternative, as stimulated immune cells can enter into the remote and inaccessible tumor cells. Immunotherapy has revolutionized patient upshots in various malignancies and might introduce different effective ways for GBM patients. Currently, researchers are exploring various immunotherapeutic strategies in patients with GBM to target both the innate and acquired immune responses. These approaches include reprogrammed tumor-associated macrophages, the use of specific antibodies to inhibit tumor progression and metastasis, modifying tumor-associated macrophages with antibodies, vaccines that utilize tumor-specific dendritic cells to activate anti-tumor T cells, immune checkpoint inhibitors, and enhanced T cells that function against tumor cells. Despite these findings, there is still room for improving the response faults of the many currently tested immunotherapies. This study aims to review the currently used immunotherapy approaches with their molecular mechanisms and clinical application in GBM.

A novel class of inhibitors that disrupts the stability of integrin heterodimers identified by CRISPR-tiling-instructed genetic screens

The plasma membrane is enriched for receptors and signaling proteins that are accessible from the extracellular space for pharmacological intervention. Here we conducted a series of CRISPR screens using human cell surface proteome and integrin family libraries in multiple cancer models. Our results identified ITGAV (integrin αV) and its heterodimer partner ITGB5 (integrin β5) as the essential integrin α/β pair for cancer cell expansion. High-density CRISPR gene tiling further pinpointed the integral pocket within the β-propeller domain of ITGAV for integrin αVβ5 dimerization. Combined with in silico compound docking, we developed a CRISPR-Tiling-Instructed Computer-Aided (CRISPR-TICA) pipeline for drug discovery and identified Cpd_AV2 as a lead inhibitor targeting the β-propeller central pocket of ITGAV. Cpd_AV2 treatment led to rapid uncoupling of integrin αVβ5 and cellular apoptosis, providing a unique class of therapeutic action that eliminates the integrin signaling via heterodimer dissociation. We also foresee the CRISPR-TICA approach to be an accessible method for future drug discovery studies.

Transduction Efficiency of Zika Virus E Protein Pseudotyped HIV-1gfp and Its Oncolytic Activity Tested in Primary Glioblastoma Cell Cultures

The development of new tools against glioblastoma multiforme (GBM), the most aggressive and common cancer originating in the brain, remains of utmost importance. Lentiviral vectors (LVs) are among the tools of future concepts, and pseudotyping offers the possibility of tailoring LVs to efficiently transduce and inactivate GBM tumor cells. Zika virus (ZIKV) has a specificity for GBM cells, leaving healthy brain cells unharmed, which makes it a prime candidate for the development of LVs with a ZIKV coat. Here, primary GBM cell cultures were transduced with different LVs encased with ZIKV envelope variants. LVs were generated by using the pNLgfpAM plasmid, which produces the lentiviral, HIV-1-based, core particle with GFP (green fluorescent protein) as a reporter (HIVgfp). Using five different GBM primary cell cultures and three laboratory-adapted GBM cell lines, we showed that ZIKV/HIVgfp achieved a 4-6 times higher transduction efficiency compared to the commonly used VSV/HIVgfp. Transduced GBM cell cultures were monitored over a period of 9 days to identify GFP+ cells to study the oncolytic effect due to ZIKV/HIVgfp entry. Tests of GBM tumor specificity by transduction of GBM tumor and normal brain cells showed a high specificity for GBM cells.

Genetically modified ZIKA virus as a microRNA-sensitive oncolytic virus against central nervous system tumors

Here we introduce a first-in-class microRNA-sensitive oncolytic Zika virus (ZIKV) for virotherapy application against central nervous system (CNS) tumors. The described methodology produced two synthetic modified ZIKV strains that are safe in normal cells, including neural stem cells, while preserving brain tropism and oncolytic effects in tumor cells. The microRNA-sensitive ZIKV introduces genetic modifications in two different virus sites: first, in the established 3'UTR region, and secondly, in the ZIKV protein coding sequence, demonstrating for the first time that the miRNA inhibition systems can be functional outside the UTR RNA sites. The total tumor remission in mice bearing human CNS tumors, including metastatic tumor growth, after intraventricular and systemic modified ZIKV administration, confirms the promise of this virotherapy as a novel agent against brain tumors-highly deadly diseases in urgent need of effective advanced therapies.

Repurposing of Zika virus live-attenuated vaccine (ZIKV-LAV) strains as oncolytic viruses targeting human glioblastoma multiforme cells

Glioblastoma multiforme (GBM) is the most common malignant primary brain cancer affecting the adult population. Median overall survival for GBM patients is poor (15 months), primarily due to high rates of tumour recurrence and the paucity of treatment options. Oncolytic virotherapy is a promising treatment alternative for GBM patients, where engineered viruses selectively infect and eradicate cancer cells by inducing cell lysis and eliciting robust anti-tumour immune response. In this study, we evaluated the oncolytic potency of live-attenuated vaccine strains of Zika virus (ZIKV-LAV) against human GBM cells in vitro. Our findings revealed that Axl and integrin αvβ5 function as cellular receptors mediating ZIKV-LAV infection in GBM cells. ZIKV-LAV strains productively infected and lysed human GBM cells but not primary endothelia and terminally differentiated neurons. Upon infection, ZIKV-LAV mediated GBM cell death via apoptosis and pyroptosis. This is the first in-depth molecular dissection of how oncolytic ZIKV infects and induces death in tumour cells.

Proteomics and Metabolomics in Congenital Zika Syndrome: A Review of Molecular Insights and Biomarker Discovery

Zika virus (ZIKV) infection can be transmitted vertically, leading to the development of congenital Zika syndrome (CZS) in infected fetuses. During the early stages of gestation, the fetuses face an elevated risk of developing CZS. However, it is important to note that late-stage infections can also result in adverse outcomes. The differences between CZS and non-CZS phenotypes remain poorly understood. In this review, we provide a summary of the molecular mechanisms underlying ZIKV infection and placental and blood-brain barriers trespassing. Also, we have included molecular alterations that elucidate the progression of CZS by proteomics and metabolomics studies. Lastly, this review comprises investigations into body fluid samples, which have aided to identify potential biomarkers associated with CZS.

RFX2 promotes tumor cell stemness through epigenetic regulation of PAF1 in spinal ependymoma

PURPOSE

Spinal ependymoma (SE) is a rare tumor that is most commonly low-grade and tends to recur when complete tumor resection is not feasible. We investigated the molecular mechanism induces stem cell features in SE.

METHODS

Immunohistochemical staining was conducted to analyze the expression of RFX2 in tumor tissues of SE patients at different stages. The expression of tumor stemness markers (Netsin and CD133) was analyzed using western blot analysis and IF, and the efficiency of sphere formation in SE cells was analyzed. The biological activities of SE cells were analyzed by EdU proliferation assay, TUNEL, wound healing, and Transwell assays. The regulatory relationship of RFX2 on PAF1 was verified by ChIP-qPCR and the dual-luciferase assay. SE cells were injected into the spinal cord of nude mice for in vivo assays.

RESULTS

RFX2 was higher in the tumor tissues of SE-III patients than in the tumor tissues of SE-I patients. RFX2 knockdown reduced the expression of tumor stemness markers in SE cells and inhibited the sphere formation efficiency. Moreover, RFX2 knockdown ameliorated the malignant progression of SE in nude mice, as manifested by prolonged survival and alleviated SE tumor infiltration. RFX2 bound to the PAF1 promoter to induce its transcription. Overexpression of PAF1 overturned the effects of RFX2 knockdown on stem cell features and biological activities of SE cells, thereby reducing survival in mice.

CONCLUSIONS

RFX2 activates PAF1 transcription, which promotes tumor stemness of SE cells and leads to the malignant progression of SE.

Advances in oncolytic herpes simplex virus and adenovirus therapy for recurrent glioma

Recurrent glioma treatment is challenging due to molecular heterogeneity and treatment resistance commonly observed in these tumors. Researchers are actively pursuing new therapeutic strategies. Oncolytic viruses have emerged as a promising option. Oncolytic viruses selectively replicate within tumor cells, destroying them and stimulating the immune system for an enhanced anticancer response. Among Oncolytic viruses investigated for recurrent gliomas, oncolytic herpes simplex virus and oncolytic adenovirus show notable potential. Genetic modifications play a crucial role in optimizing their therapeutic efficacy. Different generations of replicative conditioned oncolytic human adenovirus and oncolytic HSV have been developed, incorporating specific modifications to enhance tumor selectivity, replication efficiency, and immune activation. This review article summarizes these genetic modifications, offering insights into the underlying mechanisms of Oncolytic viruses' therapy. It also aims to identify strategies for further enhancing the therapeutic benefits of Oncolytic viruses. However, it is important to acknowledge that additional research and clinical trials are necessary to establish the safety, efficacy, and optimal utilization of Oncolytic viruses in treating recurrent glioblastoma.

Applications of organoid technology to brain tumors

Lacking appropriate model impedes basic and preclinical researches of brain tumors. Organoids technology applying on brain tumors enables great recapitulation of the original tumors. Here, we compared brain tumor organoids (BTOs) with common models including cell lines, tumor spheroids, and patient-derived xenografts. Different BTOs can be customized to research objectives and particular brain tumor features. We systematically introduce the establishments and strengths of four different BTOs. BTOs derived from patient somatic cells are suitable for mimicking brain tumors caused by germline mutations and abnormal neurodevelopment, such as the tuberous sclerosis complex. BTOs derived from human pluripotent stem cells with genetic manipulations endow for identifying and understanding the roles of oncogenes and processes of oncogenesis. Brain tumoroids are the most clinically applicable BTOs, which could be generated within clinically relevant timescale and applied for drug screening, immunotherapy testing, biobanking, and investigating brain tumor mechanisms, such as cancer stem cells and therapy resistance. Brain organoids co-cultured with brain tumors (BO-BTs) own the greatest recapitulation of brain tumors. Tumor invasion and interactions between tumor cells and brain components could be greatly explored in this model. BO-BTs also offer a humanized platform for testing the therapeutic efficacy and side effects on neurons in preclinical trials. We also introduce the BTOs establishment fused with other advanced techniques, such as 3D bioprinting. So far, over 11 brain tumor types of BTOs have been established, especially for glioblastoma. We conclude BTOs could be a reliable model to understand brain tumors and develop targeted therapies.

Differential Susceptibility of Ex Vivo Primary Glioblastoma Tumors to Oncolytic Effect of Modified Zika Virus

Glioblastoma (GBM), the most common primary malignant brain tumor, is a highly lethal form of cancer with a very limited set of treatment options. High heterogeneity in the tumor cell population and the invasive nature of these cells decrease the likely efficacy of traditional cancer treatments, thus requiring research into novel treatment options. The use of oncolytic viruses as potential therapeutics has been researched for some time. Zika virus (ZIKV) has demonstrated oncotropism and oncolytic effects on GBM stem cells (GSCs). To address the need for safe and effective GBM treatments, we designed an attenuated ZIKV strain (ZOL-1) that does not cause paralytic or neurological diseases in mouse models compared with unmodified ZIKV. Importantly, we found that patient-derived GBM tumors exhibited susceptibility (responders) and non-susceptibility (non-responders) to ZOL-1-mediated tumor cell killing, as evidenced by differential apoptotic cell death and cell viability upon ZOL-1 treatment. The oncolytic effect observed in responder cells was seen both in vitro in neurosphere models and in vivo upon xenograft. Finally, we observed that the use of ZOL-1 as combination therapy with multiple PI3K-AKT inhibitors in non-responder GBM resulted in enhanced chemotherapeutic efficacy. Altogether, this study establishes ZOL-1 as a safe and effective treatment against GBM and provides a foundation to conduct further studies evaluating its potential as an effective adjuvant with other chemotherapies and kinase inhibitors.

Vector-Transmitted Flaviviruses: An Antiviral Molecules Overview

Flaviviruses cause numerous pathologies in humans across a broad clinical spectrum with potentially severe clinical manifestations, including hemorrhagic and neurological disorders. Among human flaviviruses, some viral proteins show high conservation and are good candidates as targets for drug design. From an epidemiological point of view, flaviviruses cause more than 400 million cases of infection worldwide each year. In particular, the Yellow Fever, dengue, West Nile, and Zika viruses have high morbidity and mortality-about an estimated 20,000 deaths per year. As they depend on human vectors, they have expanded their geographical range in recent years due to altered climatic and social conditions. Despite these epidemiological and clinical premises, there are limited antiviral treatments for these infections. In this review, we describe the major compounds that are currently under evaluation for the treatment of flavivirus infections and the challenges faced during clinical trials, outlining their mechanisms of action in order to present an overview of ongoing studies. According to our review, the absence of approved antivirals for flaviviruses led to in vitro and in vivo experiments aimed at identifying compounds that can interfere with one or more viral cycle steps. Still, the currently unavailability of approved antivirals poses a significant public health issue.

Development of Zika Virus E Variants for Pseudotyping Retroviral Vectors Targeting Glioblastoma Cells

A fundamental idea for targeting glioblastoma cells is to exploit the neurotropic properties of Zika virus (ZIKV) through its two outer envelope proteins, prM and E. This study aimed to develop envelope glycoproteins for pseudotyping retroviral vectors that can be used for efficient tumor cell infection. Firstly, the retroviral vector pNLlucAM was packaged using wild-type ZIKV E to generate an E-HIVluc pseudotype. E-HIVluc infection rates for tumor cells were higher than those of normal prME pseudotyped particles and the traditionally used vesicular stomatitis virus G (VSV-G) pseudotypes, indicating that protein E alone was sufficient for the formation of infectious pseudotyped particles. Secondly, two envelope chimeras, E41.1 and E41.2, with the E wild-type transmembrane domain replaced by the gp41 transmembrane and cytoplasmic domains, were constructed; pNLlucAM or pNLgfpAM packaged with E41.1 or E41.2 constructs showed infectivity for tumor cells, with the highest rates observed for E41.2. This envelope construct can be used not only as a tool to further develop oncolytic pseudotyped viruses for therapy, but also as a new research tool to study changes in tumor cells after the transfer of genes that might have therapeutic potential.

Flaviviruses in AntiTumor Therapy

Oncolytic viruses offer a promising approach to tumor treatment. These viruses not only have a direct lytic effect on tumor cells but can also modify the tumor microenvironment and activate antitumor immunity. Due to their high pathogenicity, flaviviruses have often been overlooked as potential antitumor agents. However, with recent advancements in genetic engineering techniques, an extensive history with vaccine strains, and the development of new attenuated vaccine strains, there has been a renewed interest in the Flavivirus genus. Flaviviruses can be genetically modified to express transgenes at acceptable levels, and the stability of such constructs has been greatly improving over the years. The key advantages of flaviviruses include their reproduction cycle occurring entirely within the cytoplasm (avoiding genome integration) and their ability to cross the blood-brain barrier, facilitating the systemic delivery of oncolytics against brain tumors. So far, the direct lytic effects and immunomodulatory activities of many flaviviruses have been widely studied in experimental animal models across various types of tumors. In this review, we delve into the findings of these studies and contemplate the promising potential of flaviviruses in oncolytic therapies.

Progress in investigating the relationship between Schlafen5 genes and malignant tumors

The Schlafen5(SLFN5)gene belongs to the third group of the Schlafen protein family. As a tumor suppressor gene, SLFN5 plays a pivotal role in inhibiting tumor growth, orchestrating cell cycle regulation, and modulating the extent of cancer cell infiltration and metastasis in various malignancies. However, the high expression of SLFN 5 in some tumors was positively correlated with lymph node metastasis, tumor stage, and tumor grade. This article endeavors to elucidate the reciprocal relationship between the SLFN5 gene and malignant tumors, thereby enhancing our comprehension of the intricate mechanisms underlying the SLFN5 gene and its implications for the progression, invasive potential, and metastatic behavior of malignant tumors. At the same time, this paper summarizes the basis of SLFN 5 as a new biomarker of tumor diagnosis and prognosis, and provides new ideas for the target treatment of tumor.

Update on immune-based therapy strategies targeting cancer stem cells

Accumulating data reveals that tumors possess a specialized subset of cancer cells named cancer stem cells (CSCs), responsible for metastasis and recurrence of malignancies, with various properties such as self-renewal, heterogenicity, and capacity for drug resistance. Some signaling pathways or processes like Notch, epithelial to mesenchymal transition (EMT), Hedgehog (Hh), and Wnt, as well as CSCs' surface markers such as CD44, CD123, CD133, and epithelial cell adhesion molecule (EpCAM) have pivotal roles in acquiring CSCs properties. Therefore, targeting CSC-related signaling pathways and surface markers might effectively eradicate tumors and pave the way for cancer survival. Since current treatments such as chemotherapy and radiation therapy cannot eradicate all of the CSCs and tumor relapse may happen following temporary recovery, improving novel and more efficient therapeutic options to combine with current treatments is required. Immunotherapy strategies are the new therapeutic modalities with promising results in targeting CSCs. Here, we review the targeting of CSCs by immunotherapy strategies such as dendritic cell (DC) vaccines, chimeric antigen receptors (CAR)-engineered immune cells, natural killer-cell (NK-cell) therapy, monoclonal antibodies (mAbs), checkpoint inhibitors, and the use of oncolytic viruses (OVs) in pre-clinical and clinical studies. This review will mainly focus on blood malignancies but also describe solid cancers.

Two Sides of The Same Coin: Normal and Tumoral Stem Cells, The Relevance of In Vitro Models and Therapeutic Approaches: The Experience with Zika Virus in Nervous System Development and Glioblastoma Treatment

Neural stem cells (NSCs) were described for the first time more than two decades ago for their ability to differentiate into all neural cell lineages. The isolation of NSCs from adults and embryos was carried out by various laboratories and in different species, from mice to humans. Similarly, no more than two decades ago, cancer stem cells were described. Cancer stem cells, previously identified in hematological malignancies, have now been isolated from several solid tumors (breast, brain, and gastrointestinal compartment). Though the origin of these cells is still unknown, there is a wide consensus about their role in tumor onset, propagation and, in particular, resistance to treatments. Normal and neoplastic neural stem cells share common characteristics, and can thus be considered as two sides of the same coin. This is particularly true in the case of the Zika virus (ZIKV), which has been described as an inhibitor of neural development by specifically targeting NSCs. This understanding prompted us and other groups to evaluate ZIKV action in glioblastoma stem cells (GSCs). The results indicate an oncolytic activity of this virus vs. GSCs, opening potentially new possibilities in glioblastoma treatment.

Glioblastoma modeling with 3D organoids: progress and challenges

Glioblastoma (GBM) is the most aggressive adult primary brain tumor with nearly universal treatment resistance and recurrence. The mainstay of therapy remains maximal safe surgical resection followed by concurrent radiation therapy and temozolomide chemotherapy. Despite intensive investigation, alternative treatment options, such as immunotherapy or targeted molecular therapy, have yielded limited success to achieve long-term remission. This difficulty is partly due to the lack of pre-clinical models that fully recapitulate the intratumoral and intertumoral heterogeneity of GBM and the complex tumor microenvironment. Recently, GBM 3D organoids originating from resected patient tumors, genetic manipulation of induced pluripotent stem cell (iPSC)-derived brain organoids and bio-printing or fusion with non-malignant tissues have emerged as novel culture systems to portray the biology of GBM. Here, we highlight several methodologies for generating GBM organoids and discuss insights gained using such organoid models compared to classic modeling approaches using cell lines and xenografts. We also outline limitations of current GBM 3D organoids, most notably the difficulty retaining the tumor microenvironment, and discuss current efforts for improvements. Finally, we propose potential applications of organoid models for a deeper mechanistic understanding of GBM and therapeutic development.

Advancing organoid design through co-emergence, assembly, and bioengineering

Human adult stem cells and patient-derived induced pluripotent stem cells represent promising tools to understand human biology, development, and disease. Under a permissive environment, stem cell derivatives can self-organize and reconstruct their native milieu, resulting in the creation of organ-like entities known as organoids. Although organoids represent a breakthrough in the stem cell field, there are still considerable shortcomings preventing their widespread use, namely their variability, limited function, and reductionist size. In the past few years, sophisticated methodologies have been proposed to allow the design of organoids with improved biological fidelity and physiological relevance. Here, we summarize these emerging technologies and provide insights into how they can be utilized to fulfill the potential of stem cells.

Case report: Regression of Glioblastoma after flavivirus infection

Glioblastoma is the most frequent and aggressive primary brain cancer. In preclinical studies, Zika virus, a flavivirus that triggers the death of glioblastoma stem-like cells. However, the flavivirus oncolytic activity has not been demonstrated in human patients. Here we report a glioblastoma patient who received the standard of care therapy, including surgical resection, radiotherapy and temozolomide. However, shortly after the tumor mass resection, the patient was clinically diagnosed with a typical arbovirus-like infection, during a Zika virus outbreak in Brazil. Following the infection resolution, the glioblastoma regressed, and no recurrence was observed. This clinical response continues 6 years after the glioblastoma initial diagnosis.

Immunotherapy in glioblastoma treatment: Current state and future prospects

Glioblastoma remains as the most common and aggressive malignant brain tumor, standing with a poor prognosis and treatment prospective. Despite the aggressive standard care, such as surgical resection and chemoradiation, median survival rates are low. In this regard, immunotherapeutic strategies aim to become more attractive for glioblastoma, considering its recent advances and approaches. In this review, we provide an overview of the current status and progress in immunotherapy for glioblastoma, going through the fundamental knowledge on immune targeting to promising strategies, such as Chimeric antigen receptor T-Cell therapy, immune checkpoint inhibitors, cytokine-based treatment, oncolytic virus and vaccine-based techniques. At last, it is discussed innovative methods to overcome diverse challenges, and future perspectives in this area.

CEBPD is a master transcriptional factor for hypoxia regulated proteins in glioblastoma and augments hypoxia induced invasion through extracellular matrix-integrin mediated EGFR/PI3K pathway

Hypoxia contributes to the initiation and progression of glioblastoma by regulating a cohort of genes called hypoxia-regulated genes (HRGs) which form a complex molecular interacting network (HRG-MINW). Transcription factors (TFs) often play central roles for MINW. The key TFs for hypoxia induced reactions were explored using proteomic analysis to identify a set of hypoxia-regulated proteins (HRPs) in GBM cells. Next, systematic TF analysis identified CEBPD as a top TF that regulates the greatest number of HRPs and HRGs. Clinical sample and public database analysis revealed that CEBPD is significantly up-regulated in GBM, high levels of CEBPD predict poor prognosis. In addition, CEBPD is highly expressed in hypoxic condition both in GBM tissue and cell lines. For molecular mechanisms, HIF1α and HIF2α can activate the CEBPD promotor. In vitro and in vivo experiments demonstrated that CEBPD knockdown impaired the invasion and growth capacity of GBM cells, especially in hypoxia condition. Next, proteomic analysis identified that CEBPD target proteins are mainly involved in the EGFR/PI3K pathway and extracellular matrix (ECM) functions. WB assays revealed that CEBPD significantly positively regulated EGFR/PI3K pathway. Chromatin immunoprecipitation (ChIP) qPCR/Seq analysis and Luciferase reporter assay demonstrated that CEBPD binds and activates the promotor of a key ECM protein FN1 (fibronectin). In addition, the interactions of FN1 and its integrin receptors are necessary for CEBPD-induced EGFR/PI3K activation by promoting EGFR phosphorylation. Furthermore, GBM sample analysis in the database corroborated that CEBPD is positively correlated with the pathway activities of EGFR/PI3K and HIF1α, especially in highly hypoxic samples. At last, HRPs are also enriched in ECM proteins, indicating that ECM activities are important components of hypoxia induced responses in GBM. In conclusion, CEPBD plays important regulatory roles in the GBM HRG-MINW as a key TF, which activates the EGFR/PI3K pathway through ECM, especially FN1, mediated EGFR phosphorylation.

Modeling glioblastoma complexity with organoids for personalized treatments

Glioblastoma (GBM) remains a fatal diagnosis despite the current standard of care of maximal surgical resection, radiation, and temozolomide (TMZ) therapy. One aspect that impedes drug development is the lack of an appropriate model representative of the complexity of patient tumors. Brain organoids derived from cell culture techniques provide a robust, easily manipulatable, and high-throughput model for GBM. In this review, we highlight recent progress in developing GBM organoids (GBOs) with a focus on generating the GBM microenvironment (i.e., stem cells, vasculature, and immune cells) recapitulating human disease. Finally, we also discuss the use of organoids as a screening tool in drug development for GBM.

Cancer Spheroids and Organoids as Novel Tools for Research and Therapy: State of the Art and Challenges to Guide Precision Medicine

Spheroids and organoids are important novel players in medical and life science research. They are gradually replacing two-dimensional (2D) cell cultures. Indeed, three-dimensional (3D) cultures are closer to the in vivo reality and open promising perspectives for academic research, drug screening, and personalized medicine. A large variety of cells and tissues, including tumor cells, can be the starting material for the generation of 3D cultures, including primary tissues, stem cells, or cell lines. A panoply of methods has been developed to generate 3D structures, including spontaneous or forced cell aggregation, air-liquid interface conditions, low cell attachment supports, magnetic levitation, and scaffold-based technologies. The choice of the most appropriate method depends on (i) the origin of the tissue, (ii) the presence or absence of a disease, and (iii) the intended application. This review summarizes methods and approaches for the generation of cancer spheroids and organoids, including their advantages and limitations. We also highlight some of the challenges and unresolved issues in the field of cancer spheroids and organoids, and discuss possible therapeutic applications.

Quantitative Evaluation of Stem-like Markers of Human Glioblastoma Using Single-Cell RNA Sequencing Datasets

Targeting glioblastoma (GBM) stem-like cells (GSCs) is a common interest in both the laboratory investigation and clinical treatment of GBM. Most of the currently applied GBM stem-like markers lack validation and comparison with common standards regarding their efficiency and feasibility in various targeting methods. Using single-cell RNA sequencing datasets from 37 GBM patients, we obtained a large pool of 2173 GBM stem-like marker candidates. To evaluate and select these candidates quantitatively, we characterized the efficiency of the candidate markers in targeting the GBM stem-like cells by their frequencies and significance of being the stem-like cluster markers. This was followed by further selection based on either their differential expression in GBM stem-like cells compared with normal brain cells or their relative expression level compared with other expressed genes. The cellular location of the translated protein was also considered. Different combinations of selection criteria highlight different markers for different application scenarios. By comparing the commonly used GSCs marker CD133 (PROM1) with markers selected by our method regarding their universality, significance, and abundance, we revealed the limitations of CD133 as a GBM stem-like marker. Overall, we propose BCAN, PTPRZ1, SOX4, etc. for laboratory-based assays with samples free of normal cells. For in vivo targeting applications that require high efficiency in targeting the stem-like subtype, the ability to distinguish GSCs from normal brain cells, and a high expression level, we recommend the intracellular marker TUBB3 and the surface markers PTPRS and GPR56.

Oncolytic virus therapy for malignant gliomas: entering the new era

INTRODUCTION

To overcome the challenge of treating malignant brain tumors, oncolytic viruses (OVs) represent an innovative therapeutic approach, featuring unique mechanisms of action. The recent conditional approval of the oncolytic herpes simplex virus G47Δ as a therapeutic for malignant brain tumors marked a significant milestone in the long history of OV development in neuro-oncology.

AREAS COVERED

This review summarizes the results of recently completed and active clinical studies that investigate the safety and efficacy of different OV types in patients with malignant gliomas. The changing landscape of the OV trial design includes expansion of subjects to newly diagnosed tumors and pediatric populations. A variety of delivery methods and new routes of administration are vigorously tested to optimize tumor infection and overall efficacy. New therapeutic strategies such as combination with immunotherapies are proposed that take advantage of the characteristics of OV therapy as an immunotherapy. Preclinical studies of OV have been active and aim to translate new OV strategies to the clinic.

EXPERT OPINION

For the next decade, clinical trials and preclinical and translational research will continue to drive the development of innovative OV treatments for malignant gliomas and benefit patients and define new OV biomarkers.

Isolation of Cells from Glioblastoma Multiforme Grade 4 Tumors for Infection with Zika Virus prME and ME Pseudotyped HIV-1

This study aimed to isolate cells from grade 4 glioblastoma multiforme tumors for infection experiments with Zika virus (ZIKV) prME or ME enveloped HIV-1 pseudotypes. The cells obtained from tumor tissue were successfully cultured in human cerebrospinal fluid (hCSF) or a mixture of hCSF/DMEM in cell culture flasks with polar and hydrophilic surfaces. The isolated tumor cells as well as the U87, U138, and U343 cells tested positive for ZIKV receptors Axl and Integrin αvβ5. Pseudotype entry was detected by the expression of firefly luciferase or green fluorescent protein (gfp). In prME and ME pseudotype infections, luciferase expression in U-cell lines was 2.5 to 3.5 logarithms above the background, but still two logarithms lower than in the VSV-G pseudotype control. Infection of single cells was successfully detected in U-cell lines and isolated tumor cells by gfp detection. Even though prME and ME pseudotypes had low infection rates, pseudotypes with ZIKV envelopes are promising candidates for the treatment of glioblastoma.

Sprouty 4 suppresses glioblastoma invasion by inhibiting ERK phosphorylation and ETS-1-induced matrix metalloproteinase-9

BACKGROUND

Glioblastoma multiforme (GBM) is the most malignant glioma with highly aggressive behavior and the worst prognosis. Many efforts have been made to develop new drugs and improve the patient's survival, but the effects are not satisfactory. Here we aimed to evaluate the clinical significance and tumor-repressive function of Sprouty4 (SPRY4) in GBM.

METHODS

In our study, we detected the expression of SPRY4 in 109 GBM patients and 12 pairs of GBM tissues and the corresponding adjacent tissues. χ² test was applied to analyze the association between SPRY4 expression and the clinicopathological factors. The prognostic significances were evaluated with univariate and multivariate analyses, which were carried out by the Kaplan-Meier method and the Cox-regression proportional hazards model, respectively. With in-vitro experiments, we investigated the tumor-suppressing function of SPRY4 in GBM invasion and investigated the underlying mechanism.

RESULTS

SPRY4 mRNAs in GBMs were significantly lower than those in adjacent brain tissues. We demonstrated that SPRY4 expression could predict the favorable prognosis of GBM, and SPRY4 was an independent favorable prognostic factor of GBM. SPRY4 repressed GBM invasion via inhibiting ERK phosphorylation; therefore, suppressing ETS-1-induced MMP9 expression.

CONCLUSIONS

SPRY4 was an independent favorable prognostic factor of GBM, and it could suppress GBM invasion by ERK-ETS-MMP9 axis. Our results indicated that SPRY4 may be a promising drug target of GBM and SPRY4 detection could stratify patients with low SPRY4 expression who may benefit from anti-FGFR therapy.

Exploring the Expression and Function of cTyro3, a Candidate Zika Virus Receptor, in the Embryonic Chicken Brain and Inner Ear

The transmembrane protein Axl was proposed as an entry receptor for Zika virus (ZIKV) infection in vitro, but conflicting results from in vivo studies have made it difficult to establish Axl as a physiologically relevant ZIKV receptor. Both the functional redundancy of receptors and the experimental model used can lead to variable results. Therefore, it can be informative to explore alternative animal models to analyze ZIKV receptor candidates as an aid in discovering antivirals. This study used chicken embryos to examine the role of chicken Tyro3 (cTyro3), the equivalent of human Axl. Results show that endogenous cTyro3 mRNA expression overlaps with previously described hot spots of ZIKV infectivity in the brain and inner ear. We asked if ectopic expression or knockdown of cTyro3 influenced ZIKV infection in embryos. Tol2 vectors or replication-competent avian retroviruses were used in ovo to introduce full-length or truncated (presumed dominant-negative) cTyro3, respectively, into the neural tube on embryonic day two (E2). ZIKV was delivered to the brain 24 h later. cTyro3 manipulations did not alter ZIKV infection or cell death in the E5/E6 brain. Moreover, delivery of truncated cTyro3 variants to the E3 otocyst had no effect on inner ear formation on E6 or E10.

Signaling pathways in brain tumors and therapeutic interventions

Brain tumors, although rare, contribute to distinct mortality and morbidity at all ages. Although there are few therapeutic options for brain tumors, enhanced biological understanding and unexampled innovations in targeted therapies and immunotherapies have considerably improved patients' prognoses. Nonetheless, the reduced response rates and unavoidable drug resistance of currently available treatment approaches have become a barrier to further improvement in brain tumor (glioma, meningioma, CNS germ cell tumors, and CNS lymphoma) treatment. Previous literature data revealed that several different signaling pathways are dysregulated in brain tumor. Importantly, a better understanding of targeting signaling pathways that influences malignant behavior of brain tumor cells might open the way for the development of novel targeted therapies. Thus, there is an urgent need for a more comprehensive understanding of the pathogenesis of these brain tumors, which might result in greater progress in therapeutic approaches. This paper began with a brief description of the epidemiology, incidence, risk factors, as well as survival of brain tumors. Next, the major signaling pathways underlying these brain tumors' pathogenesis and current progress in therapies, including clinical trials, targeted therapies, immunotherapies, and system therapies, have been systemically reviewed and discussed. Finally, future perspective and challenges of development of novel therapeutic strategies in brain tumor were emphasized.

Zika virus cleaves GSDMD to disseminate prognosticable and controllable oncolysis in a human glioblastoma cell model

Glioblastoma (GBM) is the most common aggressive malignant brain cancer and is chemo- and radioresistant, with poor therapeutic outcomes. The "double-edged sword" of virus-induced cell death could be a potential solution if the oncolytic virus specifically kills cancer cells but spares normal ones. Zika virus (ZIKV) has been defined as a prospective oncolytic virus by selectively targeting GBM cells, but unclear understanding of how ZIKV kills GBM and the consequences hinders its application. Here, we found that the cellular gasdermin D (GSDMD) is required for the efficient death of a human GBM cell line caused by ZIKV infection. The ZIKV protease specifically cleaves human GSDMD to activate caspase-independent pyroptosis, harming both viral protease-harboring and naive neighboring cells. Analyzing human GSDMD variants showed that most people were susceptible to ZIKV-induced cytotoxicity, except for those with variants that resisted ZIKV cleavage or were defective in oligomerizing the N terminus GSDMD cleavage product. Consistently, ZIKV-induced secretion of the pro-inflammatory cytokine interleukin-1β and cytolytic activity were both stopped by a small-molecule inhibitor targeting GSDMD oligomerization. Thus, potential ZIKV oncolytic therapy for GBM would depend on the patient's GSDMD genetic background and could be abolished by GSDMD inhibitors if required.

SARS-CoV2 entry factors are expressed in primary human glioblastoma and recapitulated in cerebral organoid models

PURPOSE

Glioblastoma (GBM) is the most common and malignant primary brain tumor in adults with a median overall survival of only 14.6 months despite aggressive treatment. While immunotherapy has been successful in other cancers, its benefit has been proven elusive in GBM, mainly due to a markedly immunosuppressive tumor microenvironment. SARS-CoV-2 has been associated with the development of a pronounced central nervous system (CNS) inflammatory response when infecting different cells including astrocytes, endothelial cells, and microglia. While SARS-CoV2 entry factors have been described in different tissues, their presence and implication on GBM aggressiveness or microenvironment has not been studied on appropriate preclinical models.

METHODS

We evaluated the presence of crucial SARS-CoV-2 entry factors: ACE2, TMPRSS2, and NRP1 in matched surgically-derived GBM tissue, cells lines, and organoids; as well as in human brain derived specimens using immunohistochemistry, confocal pixel line intensity quantification, and transcriptome analysis.

RESULTS

We show that patient derived-GBM tissue and cell cultures express SARS-CoV2 entry factors, being NRP1 the most crucial facilitator of SARS-CoV-2 infection in GBM. Moreover, we demonstrate that, receptor expression remains present in our GBM organoids, making them an adequate model to study the effect of this virus in GBM for the potential development of viral therapies in the future.

CONCLUSION

Our findings suggest that the SARS-CoV-2 virus entry factors are expressed in primary tissues and organoid models and could be potentially utilized to study the susceptibility of GBM to this virus to target or modulate the tumor microenviroment.

Therapeutic Applications for Oncolytic Self-Replicating RNA Viruses

Self-replicating RNA viruses have become attractive delivery vehicles for therapeutic applications. They are easy to handle, can be rapidly produced in large quantities, and can be delivered as recombinant viral particles, naked or nanoparticle-encapsulated RNA, or plasmid DNA-based vectors. The self-replication of RNA in infected host cells provides the means for generating much higher transgene expression levels and the possibility to apply substantially reduced amounts of RNA to achieve similar expression levels or immune responses compared to conventional synthetic mRNA. Alphaviruses and flaviviruses, possessing a single-stranded RNA genome of positive polarity, as well as measles viruses and rhabdoviruses with a negative-stranded RNA genome, have frequently been utilized for therapeutic applications. Both naturally and engineered oncolytic self-replicating RNA viruses providing specific replication in tumor cells have been evaluated for cancer therapy. Therapeutic efficacy has been demonstrated in animal models. Furthermore, the safe application of oncolytic viruses has been confirmed in clinical trials. Multiple myeloma patients treated with an oncolytic measles virus (MV-NIS) resulted in increased T-cell responses against the measles virus and several tumor-associated antigen responses and complete remission in one patient. Furthermore, MV-CEA administration to patients with ovarian cancer resulted in a stable disease and more than doubled the median overall survival.

Interfer(on)ing with Zika virus

In this issue of Neuron, Bulstrode et al.¹ demonstrate that glioblastoma slice cultures, unlike neural progenitors, are refractory to Zika virus infection. The anti-infective mechanism is myeloid-lineage cell-secreted interferon beta. These studies have implications for therapeutics in both glioblastoma and Zika virus infections.

Myeloid cell interferon secretion restricts Zika flavivirus infection of developing and malignant human neural progenitor cells

Zika virus (ZIKV) can infect human developing brain (HDB) progenitors resulting in epidemic microcephaly, whereas analogous cellular tropism offers treatment potential for the adult brain cancer, glioblastoma (GBM). We compared productive ZIKV infection in HDB and GBM primary tissue explants that both contain SOX2+ neural progenitors. Strikingly, although the HDB proved uniformly vulnerable to ZIKV infection, GBM was more refractory, and this correlated with an innate immune expression signature. Indeed, GBM-derived CD11b+ microglia/macrophages were necessary and sufficient to protect progenitors against ZIKV infection in a non-cell autonomous manner. Using SOX2+ GBM cell lines, we found that CD11b+-conditioned medium containing type 1 interferon beta (IFNβ) promoted progenitor resistance to ZIKV, whereas inhibition of JAK1/2 signaling restored productive infection. Additionally, CD11b+ conditioned medium, and IFNβ treatment rendered HDB progenitor lines and explants refractory to ZIKV. These findings provide insight into neuroprotection for HDB progenitors as well as enhanced GBM oncolytic therapies.

A Comprehensive Update of Cerebral Organoids between Applications and Challenges

The basic technology of stem cells has been developed and created organoids, which have established a strong interest in regenerative medicine. Different cell types have been used to generate cerebral organoids, which include interneurons and oligodendrocytes (OLs). OLs are fundamental for brain development. Abundant studies have displayed that brain organoids can recapitulate fundamental and vital features of the human brain, such as cellular regulation and distribution, neuronal networks, electrical activities, and physiological structure. The organoids contain essential ventral brain domains and functional cortical interneurons, which are similar to the developing cortex and medial ganglionic eminence (MGE). So, brain organoids have provided a singular model to study and investigate neurological disorder mechanisms and therapeutics. Furthermore, the blood brain barrier (BBB) organoids modeling contributes to accelerate therapeutic discovery for the treatment of several neuropathologies. In this review, we summarized the advances of the brain organoids applications to investigate neurological disorder mechanisms such as neurodevelopmental and neurodegenerative disorders, mental disorders, brain cancer, and cerebral viral infections. We discussed brain organoids’ therapeutic application as a potential therapeutic unique method and highlighted in detail the challenges and hurdles of organoid models.

Identification and characterization of key residues in Zika virus envelope protein for virus assembly and entry

Zika virus (ZIKV), a family member in the Flavivirus genus, has re-emerged as a global public health concern. The envelope (E) proteins of flaviviruses play a dual role in viral assembly and entry. To identify the key residues of E in virus entry, we generated a ZIKV trans-complemented particle (ZIKV_TCP) system, in which a subgenomic reporter replicon was packaged by trans-complementation with expression of CprME. We performed mutagenesis studies of the loop regions that protrude from the surface of the virion in the E ectodomains (DI, DII, DIII). Most mutated ZIKV_TCPs exhibited deficient egress. Mutations in DII and in the hinge region of DI and DIII affected prM expression. With a bioorthogonal system, photocrosslinking experiments identified crosslinked intracellular E trimers and demonstrated that egress-deficient mutants in DIII impaired E trimerization. Of these mutants, an E-trimerization-dead mutation D389A that nears the E-E interface between two neighbouring spikes in the immature virion completely abolished viral egress. Several mutations abolished ZIKV_TCPs’ entry, without severely affecting viral egress. Further virus binding experiments demonstrated a deficiency of the mutated ZIKV_TCPs in virus attachment. Strikingly, synthesized peptide containing residues of two mutants (268-273aa in DII) could bind to host cells and significantly compete for viral attachment and interfere with viral infection, suggesting an important role of these resides in virus entry. Our findings uncovered the requirement for DIII mediated-E trimerization in viral egress, and discovered a key residue group in DII that participates in virus entry.

Wif1 Mediates Coordination of Bone Morphogenetic Protein and Wnt Signaling in Neural and Glioma Stem Cells

Wnts, bone morphogenetic protein (BMP), and fibroblast growth factor (FGF) are paracrine signaling pathways implicated in the niche control of stem cell fate decisions. BMP-on and Wnt-off are the dominant quiescent niche signaling pathways in many cell types, including neural stem cells (NSCs). However, among the multiple inhibitory family members of the Wnt pathway, those with direct action after BMP4 stimulation in NSCs remain unclear. We examined 11 Wnt inhibitors in NSCs after BMP4 treatment. Wnt inhibitory factor 1 (Wif1) has been identified as the main factor reacting to BMP4 stimuli. RNA sequencing confirmed that Wif1 was markedly upregulated after BMP4 treatment in different gene expression analyses. Similar to the functional role of BMP4, Wif1 significantly decreased the cell cycle of NSCs and significantly inhibited cell proliferation (P < 0.05). Combined treatment with BMP4 and Wif1 significantly enhanced the inhibition of cell growth compared with the single treatment (P < 0.05). Wif1 expression was clearly lower in glioblastoma and low-grade glioma samples than in normal samples (P < 0.05). A functional analysis revealed that both BMP4 and Wif1 could decrease glioma cell growth. These effects were abrogated by the BMP inhibitor Noggin. The collective findings demonstrate that Wif1 plays a key role in quiescent NSC homeostasis and glioma cell growth downstream of BMP-on signaling. The functional roles of Wif1/BMP4 in glioma cells may provide a technical basis for regenerative medicine, drug discovery, and personal molecular therapy in future clinical treatments.

SARS-CoV-2 infects human brain organoids causing cell death and loss of synapses that can be rescued by treatment with Sofosbuvir

The Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) is the causative agent of coronavirus disease 2019 (COVID-19), which was rapidly declared a pandemic by the World Health Organization (WHO). Early clinical symptomatology focused mainly on respiratory illnesses. However, a variety of neurological manifestations in both adults and newborns are now well-documented. To experimentally determine whether SARS-CoV-2 could replicate in and affect human brain cells, we infected iPSC-derived human brain organoids. Here, we show that SARS-CoV-2 can productively replicate and promote death of neural cells, including cortical neurons. This phenotype was accompanied by loss of excitatory synapses in neurons. Notably, we found that the U.S. Food and Drug Administration (FDA)-approved antiviral Sofosbuvir was able to inhibit SARS-CoV-2 replication and rescued these neuronal alterations in infected brain organoids. Given the urgent need for readily available antivirals, these results provide a cellular basis supporting repurposed antivirals as a strategic treatment to alleviate neurocytological defects that may underlie COVID-19- related neurological symptoms.

Glioma stem cells and neural stem cells respond differently to BMP4 signaling

Malignant glioma is a highly heterogeneous and invasive primary brain tumor characterized by high recurrence rates, resistance to combined therapy, and dismal prognosis. Glioma stem cells (GSCs) are likely responsible for tumor progression, resistance to therapy, recurrence, and poor prognosis owing to their high self-renewal and tumorigenic potential. As a family member of BMP signaling, bone morphogenetic protein4 (BMP4) has been reported to induce the differentiation of GSCs and neural stem cells (NSCs). However, the molecular mechanisms underlying the BMP4-mediated effects in these two cell types are unclear. In this study, we treated hGSCs and hNSCs with BMP4 and compared the phenotypic and transcriptional changes between these two cell types. Phenotypically, we found that the growth of hGSCs was greatly inhibited by BMP4, but the same treatment only increased the cell size of hNSCs. While the RNA sequencing results showed that BMP4 treatment evoked significantly transcriptional changes in both hGSCs and hNSCs, the profiles of differentially expressed genes were distinct between the two groups. A gene set that specifically targeted the proliferation and differentiation of hGSCs but not hNSCs was enriched and then validated in hGSC culture. Our results suggested that hGSCs and hNSCs responded differently to BMP4 stimulation. Understanding and investigating different responses between hGSCs and hNSCs will benefit finding partner factors working together with BMP4 to further suppress GSCs proliferation and stemness without disturbing NSCs.

The Japanese Encephalitis Antigenic Complex Viruses: From Structure to Immunity

In the last three decades, several flaviviruses of concern that belong to different antigenic groups have expanded geographically. This has resulted in the presence of often more than one virus from a single antigenic group in some areas, while in Europe, Africa and Australia, additionally, multiple viruses belonging to the Japanese encephalitis (JE) serogroup co-circulate. Morphological heterogeneity of flaviviruses dictates antibody recognition and affects virus neutralization, which influences infection control. The latter is further impacted by sequential infections involving diverse flaviviruses co-circulating within a region and their cross-reactivity. The ensuing complex molecular virus-host interplay leads to either cross-protection or disease enhancement; however, the molecular determinants and mechanisms driving these outcomes are unclear. In this review, we provide an overview of the epidemiology of four JE serocomplex viruses, parameters affecting flaviviral heterogeneity and antibody recognition, host immune responses and the current knowledge of the cross-reactivity involving JE serocomplex flaviviruses that leads to differential clinical outcomes, which may inform future preventative and therapeutic interventions.

Pathophysiological roles of integrins in gliomas from the perspective of glioma stem cells

Glioblastoma is the most common primary intracranial tumor and is also one of the most malignant central nervous system tumors. Its characteristics, such as high malignancy, abundant tumor vasculature, drug resistance, and recurrence-prone nature, cause great suffering to glioma patients. Furthermore, glioma stem cells are the primordial cells of the glioma and play a central role in the development of glioma. Integrins—heterodimers composed of noncovalently bound a and ß subunits—are highly expressed in glioma stem cells and play an essential role in the self-renewal, differentiation, high drug resistance, and chemo-radiotherapy resistance of glioma stem cells through cell adhesion and signaling. However, there are various types of integrins, and their mechanisms of function on glioma stem cells are complex. Therefore, this article reviews the feasibility of treating gliomas by targeting integrins on glioma stem cells.

SREBP2-dependent lipid gene transcription enhances the infection of human dendritic cells by Zika virus

The emergence of Zika virus (ZIKV) as a global health threat has highlighted the unmet need for ZIKV-specific vaccines and antiviral treatments. ZIKV infects dendritic cells (DC), which have pivotal functions in activating innate and adaptive antiviral responses; however, the mechanisms by which DC function is subverted to establish ZIKV infection are unclear. Here we develop a genomics profiling method that enables discrete analysis of ZIKV-infected versus neighboring, uninfected primary human DCs to increase the sensitivity and specificity with which ZIKV-modulated pathways can be identified. The results show that ZIKV infection specifically increases the expression of genes enriched for lipid metabolism-related functions. ZIKV infection also increases the recruitment of sterol regulatory element-binding protein (SREBP) transcription factors to lipid gene promoters, while pharmacologic inhibition or genetic silencing of SREBP2 suppresses ZIKV infection of DCs. Our data thus identify SREBP2-activated transcription as a mechanism for promoting ZIKV infection amenable to therapeutic targeting.

Glioblastoma microenvironment and its reprogramming by oncolytic virotherapy

Glioblastoma (GBM), a highly aggressive form of brain tumor, responds poorly to current conventional therapies, including surgery, radiation therapy, and systemic chemotherapy. The reason is that the delicate location of the primary tumor and the existence of the blood-brain barrier limit the effectiveness of traditional local and systemic therapies. The immunosuppressive status and multiple carcinogenic pathways in the complex GBM microenvironment also pose challenges for immunotherapy and single-targeted therapy. With an improving understanding of the GBM microenvironment, it has become possible to consider the immunosuppressive and highly angiogenic GBM microenvironment as an excellent opportunity to improve the existing therapeutic efficacy. Oncolytic virus therapy can exert antitumor effects on various components of the GBM microenvironment. In this review, we have focused on the current status of oncolytic virus therapy for GBM and the related literature on antitumor mechanisms. Moreover, the limitations of oncolytic virus therapy as a monotherapy and future directions that may enhance the field have also been discussed.

CDK4/6 inhibition enhances oncolytic virus efficacy by potentiating tumor-selective cell killing and T cell activation in refractory glioblastoma

Glioblastoma multiforme (GBM) is among the most aggressive human cancers. Although oncolytic virus (OV) therapy has been proposed as a potential approach to treat GBM, it frequently fails because GBM cells are usually nonpermissive to OV. Here, we describe a dual-step drug screen for identifying chemical enhancers of oncolytic virus in GBM. From a high-throughput screen of 1416 FDA-approved drugs, an inhibitor of CDK4/6 was identified as the top enhancer, selectively increasing potency of two OV strains, VSVΔ51 and Zika virus. Mechanistically, CDK4/6 inhibition promoted autophagic degradation of MAVS, resulting in impaired antiviral responses and enhanced tumor-selective replication of VSVΔ51 in vitro and in vivo. CDK4/6 inhibition cooperated with VSVΔ51 to induce severe DNA damage stress and amplify oncolysis. In GBM xenograft models, combined treatment with CDK4/6 inhibitor and VSVΔ51 significantly inhibited tumor growth and prolonged the survival of tumor-bearing mice. Further investigation revealed that CDK4/6 inhibitor and VSVΔ51 synergistically induced immunogenic cell death and boosted anti-tumor immunity. Together, this study features a promising approach of treating aggressive GBM through the combination of CDK4/6 inhibitor with OV.

Oct4A palmitoylation modulates tumorigenicity and stemness in human glioblastoma cells

BACKGROUND

Glioblastoma multiforme and other solid malignancies are heterogeneous, containing subpopulations of tumor cells that exhibit stem characteristics. Oct4, also known as POU5F1, is a key transcription factor in the self-renewal, proliferation, and differentiation of stem cells. Although it has been detected in advanced gliomas, the biological function of Oct4, and transcriptional machinery maintained by the stemness of Oct4 protein-mediated glioma stem cells (GSC), has not been fully determined.

METHODS

The expression of Oct4 variants was evaluated in brain cancer cell lines, and in brain tumor tissues, by quantitative real-time PCR, western blotting, and immunohistochemical analysis. The palmitoylation level of Oct4A was determined by the acyl-biotin exchange method, and the effects of palmitoylation Oct4A on GSCs were investigated by a series of in vitro (neuro-sphere formation assay, double immunofluorescence, pharmacological treatment, luciferase assay, and coimmunoprecipitation) and in vivo (xenograft model) experiments.

RESULTS

Here, we report that all three variants of Oct4 are expressed in different types of cerebral cancer, while Oct4A is important for maintaining tumorigenicity in GSCs. Palmitoylation mediated by ZDHHC17 was indispensable for preserving Oct4A from lysosome degradation to maintain its protein stability. Oct4A palmitoylation also helped to integrate Sox4 and Oct4A in the SOX2 enhancement subregion to maintain the stem performance of GSCs. We also designed Oct4A palmitoylation competitive inhibitors, inhibiting the self-renewal ability and tumorigenicity of GSCs.

CONCLUSIONS

These findings indicate that Oct4A acts on the tumorigenic activity of glioblastoma, and Oct4A palmitoylation is a candidate therapeutic target.