Suppression of HMGB1 Released in the Glioblastoma Tumor Microenvironment Reduces Tumoral Edema

Tuning cellular metabolism for cancer virotherapy

Oncolytic viruses (OVs) represent an emerging immunotherapeutic strategy owing to their capacity for direct tumor lysis and induction of antitumor immunity. However, hurdles like transient persistence and moderate efficacy necessitate innovative approaches. Metabolic remodeling has recently gained prominence as a strategic intervention, wherein OVs or combination regimens could reprogram tumor and immune cell metabolism to enhance viral replication and oncolysis. In this review, we summarize recent advances in strategic reprogramming of tumor and immune cell metabolism to enhance OV-based immunotherapies. Specific tactics include engineering viruses to target glycolytic, glutaminolytic, and nucleotide synthesis pathways in cancer cells, boosting viral replication and tumor cell death. Additionally, rewiring T cell and NK cell metabolism of lipids, amino acids, and carbohydrates shows promise to enhance antitumor effects. Further insights are discussed to pave the way for the clinical implementation of metabolically enhanced oncolytic platforms, including balancing metabolic modulation to limit antiviral responses while promoting viral persistence and tumor clearance.

Impact of HMGB1 on cancer development and therapeutic insights focused on CNS malignancy

The present study explores the complex roles of High Mobility Group Box 1 (HMGB1) in the context of cancer development, emphasizing glioblastoma (GBM) and other central nervous system (CNS) cancers. HMGB1, primarily known for its involvement in inflammation and angiogenesis, emerges as a multifaceted player in the tumorigenesis of GBM. The overexpression of HMGB1 correlates with glioma malignancy, influencing key pathways like RAGE/MEK/ERK and RAGE/Rac1. Additionally, HMGB1 secretion is linked to the maintenance of glioma stem cells (GSCs) and contributes to the tumor microenvironment's (TME) vascular leakiness. Henceforth, our review discusses the bidirectional impact of HMGB1, acting as both a promoter of tumor progression and a mediator of anti-tumor immune responses. Notably, HMGB1 exhibits tumor-suppressive roles by inducing apoptosis, limiting cellular proliferation, and enhancing the sensitivity of GBM to therapeutic interventions. This dualistic nature of HMGB1 calls for a nuanced understanding of its implications in GBM pathogenesis, offering potential avenues for more effective and personalized treatment strategies. The findings underscore the need to explore HMGB1 as a prognostic marker, therapeutic target, and a promising tool for stimulating anti-tumor immunity in GBM.

circ_0008285 Regulates Glioma Progression via the miR-384/HMGB1 Axis

Background

Recent studies indicate that circular RNAs (circRNAs) have been implicated in the initiation or progression of a wide spectrum of diseases. In the current study, we explored the potential engagement of circ_0008285 in glioma and investigated the downstream regulators.

Methods

The detection of circ_0008285 level in glioma specimens and cell lines was conducted by quantitative real-time polymerase chain reaction. The chi-squared test was employed to evaluate the relationship between the circ_0008285 level and the clinical features of glioma patients. The roles of circ_0008285 on the proliferation and apoptosis of glioma cells were studied by knockdown experiment. Meanwhile, the regulatory relationship of circ_0008285, miR-384, and high mobility group protein B1 (HMGB1) was explored in glioma cells, and we explored the effects of circ_0008285/miR-384/HMGB1 pathway on glioma cells.

Results

In glioma specimens and cell lines, the expression of circ_0008285 was significantly increased, and a high circ_0008285 level was associated with a larger tumor size and more advanced grading in glioma patients. Furthermore, downregulating circ_0008285 suppressed proliferation and triggered apoptosis of glioma cells, which was associated with a cell cycle arrest at the G1/G0 phase. Mechanism studies indicated that circ_0008285 regulated HMGB1 by sponging miR-384. Functional experiments demonstrated that circ_0008285 promoted the malignant phenotype of glioma cells by miR-384/HMGB1 axis.

Conclusion

Our study revealed circ_0008285 as a novel oncogenic factor in glioma through modulating the miR-384/HMGB1 pathway, suggesting that targeting circ_0008285 could serve as a strategy for glioma management.

esRAGE-expressing oHSV enhances anti-tumor efficacy by inhibition of endothelial cell activation

High-mobility group box 1 (HMGB1) is a damage-associated molecular pattern (DAMP) molecule that plays an important role in inflammation and tumorigenesis. Receptor for advanced glycation end products (RAGE) is one of the major receptors to which extracellular HMGB1 binds to mediate its activity. RAGE is highly expressed on the endothelial cells (ECs) and regulates endothelial permeability during inflammation. Here, we introduced the endogenous secretory form of RAGE (esRAGE) as a decoy receptor for RAGE ligands into an oncolytic herpes simplex virus 1 (oHSV) (OVesRAGE), which, upon release, can function to block RAGE signaling. OVesRAGE significantly decreased phosphorylation of MEK1/2 and Erk and increased cleaved PARP in glioblastoma (GBM) cells in vitro and in vivo. oHSV-infected GBM cells co-cultured with ECs were used to test OVesRAGE effect on EC activation, vessel leakiness, virus replication, and tumor cell killing. OVesRAGE could effectively secrete esRAGE and rescue virus-induced EC migration and activation. Reduced EC activation facilitated virus replication in tumor cells when co-cultured with ECs. Finally, OVesRAGE significantly enhanced therapeutic efficacy in GBM-bearing mice. Collectively, our data demonstrate that HMGB1-RAGE signaling could be a promising target and that its inhibition is a feasible approach to improve the efficacy of oHSV therapy.

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.

The combination of radiomics features and VASARI standard to predict glioma grade

Background and Purpose

Radiomics features and The Visually AcceSAble Rembrandt Images (VASARI) standard appear to be quantitative and qualitative evaluations utilized to determine glioma grade. This study developed a preoperative model to predict glioma grade and improve the efficacy of clinical strategies by combining these two assessment methods.

Materials and Methods

Patients diagnosed with glioma between March 2017 and September 2018 who underwent surgery and histopathology were enrolled in this study. A total of 3840 radiomic features were calculated; however, using the least absolute shrinkage and selection operator (LASSO) method, only 16 features were chosen to generate a radiomic signature. Three predictive models were developed using radiomic features and VASARI standard. The performance and validity of models were evaluated using decision curve analysis and 10-fold nested cross-validation.

Results

Our study included 102 patients: 35 with low-grade glioma (LGG) and 67 with high-grade glioma (HGG). Model 1 utilized both radiomics and the VASARI standard, which included radiomic signatures, proportion of edema, and deep white matter invasion. Models 2 and 3 were constructed with radiomics or VASARI, respectively, with an area under the receiver operating characteristic curve (AUC) of 0.937 and 0.831, respectively, which was less than that of Model 1, with an AUC of 0.966.

Conclusion

The combination of radiomics features and the VASARI standard is a robust model for predicting glioma grades.

AllergoOncology: Danger signals in allergology and oncology: A European Academy of Allergy and Clinical Immunology (EAACI) Position Paper

The immune system interacts with many nominal 'danger' signals, endogenous danger-associated (DAMP), exogenous pathogen (PAMP) and allergen (AAMP)-associated molecular patterns. The immune context under which these are received can promote or prevent immune activating or inflammatory mechanisms and may orchestrate diverse immune responses in allergy and cancer. Each can act either by favouring a respective pathology or by supporting the immune response to confer protective effects, depending on acuity or chronicity. In this Position Paper under the collective term danger signals or DAMPs, PAMPs and AAMPs, we consider their diverse roles in allergy and cancer and the connection between these in AllergoOncology. We focus on their interactions with different immune cells of the innate and adaptive immune system and how these promote immune responses with juxtaposing clinical outcomes in allergy and cancer. While danger signals present potential targets to overcome inflammatory responses in allergy, these may be reconsidered in relation to a history of allergy, chronic inflammation and autoimmunity linked to the risk of developing cancer, and with regard to clinical responses to anti-cancer immune and targeted therapies. Cross-disciplinary insights in AllergoOncology derived from dissecting clinical phenotypes of common danger signal pathways may improve allergy and cancer clinical outcomes.

Up-regulation of LINC00665 contributes to the progression of glioma and correlates with its MRI characteristics

BACKGROUND

LncRNA LINC00665 partakes in controlling the malignant phenotype of cancer cells, but its role in glioma and the related regulatory mechanism remain uncertain.

METHODS

RT-PCR was exploited to examine LINC00665 expression. The relationships among the LINC00665 expression, the clinicopathologic values and magnetic resonance imaging (MRI) characteristics of glioma were analyzed. The multiplication, movement, and aggressiveness of glioma cell lines were evaluated by CCK-8, EdU, and Transwell experiments after constructing LINC00665 overexpression and LINC00665 knockdown cell models. A dual-luciferase reporter gene experiment and RIP experiment were executed to validate the interactions between LINC00665 and miR-129-5p, and between miR-129-5p and HMGB1. Western blot and RT-PCR were conducted to find the impact of LINC00665 and miR-129-5p on HMGB1 expression. Nude mouse model was also constructed to examine the impact of LINC00665 on multiplication and aggressiveness of glioma cells in vivo.

RESULTS

LINC00665 expression was markedly increased in glioma. High LINC00665 expression in glioma was closely linked to larger tumor diameter, higher pathologic grade, heterogeneous MRI signal of the tumor, increased peritumoral edema, and stronger MRI enhancement characteristics. LINC00665 overexpression facilitated the malignant behavior of glioma cells, while LINC00665 knockdown played the reverse role. Mechanistically, LINC00665 could decoy miR-129-5p, and indirectly increased HMGB1 expression.

CONCLUSION

LINC00665 functions as an oncogenic lncRNA in glioma, to accelerate glioma progression by modulating miR-129-5p and increasing HMGB1 expression.

The use of oncolytic virotherapy in the neoadjuvant setting

Surgical removal of tumors remains a front-line therapy for many types of cancer. However, this treatment often fails to eradicate disease due to either recurrence of the original tumor or development of distant micrometastases. To address these challenges, patients are often given non-curative treatments presurgery with the intent of improving surgical outcomes. These treatments, collectively known as neoadjuvant therapies, have traditionally focused on the presurgical use of chemotherapeutics. Recently, however, a variety of immunotherapies have also been identified as potentially effective in the neoadjuvant setting. One of these immunotherapies is oncolytic virotherapy, whose clinical use has exploded with the Food and Drug Administration approval of Talimogene Laherparepvec. This review summarizes both the preclinical and clinical literature examining the use of oncolytic virotherapy in the neoadjuvant setting for different types of cancers and discusses some of the major questions that still need to be addressed in order for this unique use of immunotherapy to become clinically viable.

Implications of immune cells in oncolytic herpes simplex virotherapy for glioma

Despite current progress in treatment, glioblastoma (GBM) remains a lethal primary malignant tumor of the central nervous system. Although immunotherapy has recently achieved remarkable survival effectiveness in multiple malignancies, none of the immune checkpoint inhibitors (ICIs) for GBM have shown anti-tumor efficacy in clinical trials. GBM has a characteristic immunosuppressive tumor microenvironment (TME) that results in the failure of ICIs. Oncolytic herpes simplex virotherapy (oHSV) is the most advanced United States Food and Drug Administration-approved virotherapy for advanced metastatic melanoma patients. Recently, another oHSV, Delytact^®, was granted conditional approval in Japan against GBM, highlighting it as a promising treatment. Since oncolytic virotherapy can recruit abundant immune cells and modify the immune TME, oncolytic virotherapy for immunologically cold GBM will be an attractive therapeutic option for GBM. However, as these immune cells have roles in both anti-tumor and anti-viral immunity, fine-tuning of the TME using oncolytic virotherapy will be important to maximize the therapeutic efficacy. In this review, we discuss the current knowledge of oHSV, with a focus on the role of immune cells as friend or foe in oncolytic virotherapy.

A Dual Anti-Inflammatory and Anti-Proliferative 3-Styrylchromone Derivative Synergistically Enhances the Anti-Cancer Effects of DNA-Damaging Agents on Colon Cancer Cells by Targeting HMGB1-RAGE-ERK1/2 Signaling

The current anti-cancer treatments are not enough to eradicate tumors, and therefore, new modalities and strategies are still needed. Most tumors generate an inflammatory tumor microenvironment (TME) and maintain the niche for their development. Because of the critical role of inflammation via high-mobility group box 1 (HMGB1)–receptor for advanced glycation end-products (RAGE) signaling pathway in the TME, a novel compound possessing both anti-cancer and anti-inflammatory activities by suppressing the HMGB1-RAGE axis provides an effective strategy for cancer treatment. A recent work of our group found that some anti-cancer 3-styrylchromones have weak anti-inflammatory activities via the suppression of this axis. In this direction, we searched such anti-cancer molecules possessing potent anti-inflammatory activities and discovered 7-methoxy-3-hydroxy-styrylchromone (C6) having dual suppressive activities. Mechanism-of-action studies revealed that C6 inhibited the increased phosphorylation of extracellular signal-regulated kinases 1 and 2 (ERK1/2) under the stimulation of HMGB1-RAGE signaling and thereby suppressed cytokine production in macrophage-like RAW264.7 cells. On the other hand, in colorectal cancer HCT116 cells, C6 inhibited the activation of ERK1/2, cyclin-dependent kinase 1, and AKT, down-regulated the protein level of XIAP, and up-regulated pro-apoptotic Bax and caspase-3/7 expression. These alterations are suggested to be involved in the C6-induced suppression of cell cycle/proliferation and initiation of apoptosis in the cancer cells. More importantly, in cancer cells, the treatment of C6 potentiates the anti-cancer effects of DNA-damaging agents. Thus, C6 may be a promising lead for the generation of a novel class of cancer therapeutics.

Necrotic reshaping of the glioma microenvironment drives disease progression

Glioblastoma is the most common primary brain tumor and has a dismal prognosis. The development of central necrosis represents a tipping point in the evolution of these tumors that foreshadows aggressive expansion, swiftly leading to mortality. The onset of necrosis, severe hypoxia and associated radial glioma expansion correlates with dramatic tumor microenvironment (TME) alterations that accelerate tumor growth. In the past, most have concluded that hypoxia and necrosis must arise due to "cancer outgrowing its blood supply" when rapid tumor growth outpaces metabolic supply, leading to diffusion-limited hypoxia. However, growing evidence suggests that microscopic intravascular thrombosis driven by the neoplastic overexpression of pro-coagulants attenuates glioma blood supply (perfusion-limited hypoxia), leading to TME restructuring that includes breakdown of the blood-brain barrier, immunosuppressive immune cell accumulation, microvascular hyperproliferation, glioma stem cell enrichment and tumor cell migration outward. Cumulatively, these adaptations result in rapid tumor expansion, resistance to therapeutic interventions and clinical progression. To inform future translational investigations, the complex interplay among environmental cues and myriad cell types that contribute to this aggressive phenotype requires better understanding. This review focuses on contributions from intratumoral thrombosis, the effects of hypoxia and necrosis, the adaptive and innate immune responses, and the current state of targeted therapeutic interventions.

NOTCH induced MDSC recruitment after oHSV virotherapy in CNS cancer models modulates anti-tumor immunotherapy

PURPOSE

Oncolytic herpes simplex virus-1 (oHSV) infection of brain tumors activates NOTCH, however the consequences of NOTCH on oHSV-induced immunotherapy is largely unknown. Here we evaluated the impact of NOTCH blockade on virus-induced immunotherapy.

EXPERIMENTAL DESIGN

RNA sequencing (RNA-seq), TCGA data analysis, flow cytometry, Luminex- and ELISA-based assays, brain tumor animal models, and serum analysis of patients with recurrent glioblastoma (GBM) treated with oHSV was used to evaluate the effect of NOTCH signaling on virus-induced immunotherapy.

RESULTS

TCGA data analysis of patients with grade IV glioma and oHSV treatment of experimental brain tumors in mice showed that NOTCH signaling significantly correlated with a higher myeloid cell infiltration. Immunofluorescence staining and RNA-seq uncovered a significant induction of Jag1 (NOTCH ligand) expression in infiltrating myeloid cells upon oHSV infection. Jag1-expressing macrophages further spread NOTCH activation in the tumor microenvironment (TME). NOTCH-activated macrophages increased the secretion of CCL2, which further amplified myeloid-derived suppressor cells. CCL2 and IL10 induction was also observed in serum of patients with recurrent GBM treated with oHSV (rQnestin34.5; NCT03152318). Pharmacologic blockade of NOTCH signaling rescued the oHSV-induced immunosuppressive TME and activated a CD8-dependent antitumor memory response, resulting in a therapeutic benefit.

CONCLUSIONS

NOTCH-induced immunosuppressive myeloid cell recruitment limited antitumor immunity. Translationally, these findings support the use of NOTCH inhibition in conjunction with oHSV therapy.

Replication and Spread of Oncolytic Herpes Simplex Virus in Solid Tumors

Oncolytic herpes simplex virus (oHSV) is a highly promising treatment for solid tumors. Intense research and development efforts have led to first-in-class approval for an oHSV for melanoma, but barriers to this promising therapy still exist that limit efficacy. The process of infection, replication and transmission of oHSV in solid tumors is key to obtaining a good lytic destruction of infected cancer cells to kill tumor cells and release tumor antigens that can prime anti-tumor efficacy. Intracellular tumor cell signaling and tumor stromal cells present multiple barriers that resist oHSV activity. Here, we provide a review focused on oncolytic HSV and the essential viral genes that allow for virus replication and spread in order to gain insight into how manipulation of these pathways can be exploited to potentiate oHSV infection and replication among tumor cells.

Current strategies in engaging oncolytic viruses with antitumor immunity

Oncolytic virotherapy has produced promising yet limited results in preclinical and clinical studies. Besides direct oncolytic activity, a significant therapeutic mechanism of oncolytic virotherapy is the induction of tumor-specific immunity. Consequently, the efficacy of oncolytic viruses can be improved by the insertion of immune stimulator genes and rational combinatorial therapy with other immunotherapies. This article reviews recent efforts on arming oncolytic viruses with a variety of immune stimulator molecules, immune cell engagers, and other immune potentiating molecules. We outline what is known about the mechanisms of action and the corresponding results. The review also discusses recent preclinical and clinical studies of combining oncolytic virotherapy with immune-checkpoint inhibitors and the role of oncolytic virotherapy in changing the tumor microenvironment.

Potential effects of HMGB1 on viral replication and virus infection-induced inflammatory responses: A promising therapeutic target for virus infection-induced inflammatory diseases

Inflammatory responses, characterized by the overproduction of numerous proinflammatory mediators by immune cells, is essential to protect the host against invading pathogens. Excessive production of proinflammatory cytokines is a key pathogenic factor accounting for severe tissue injury and disease progression during the infection of multiple viruses, which are therefore termed as "cytokine storm". High mobility group box 1 (HMGB1), a ubiquitous DNA-binding protein released either over virus-infected cells or activated immune cells, may act as a proinflammatory cytokine with a robust capacity to potentiate inflammatory response and disease severity. Moreover, HMGB1 is a host factor that potentially participates in the regulation of viral replication cycles with complicated mechanisms. Currently, HMGB1 is regarded as a promising therapeutic target against virus infection. Here, we provide an overview of the updated studies on how HMGB1 is differentially manipulated by distinct viruses to regulate viral diseases.

The Current State of Oncolytic Herpes Simplex Virus for Glioblastoma Treatment

Glioblastoma (GBM) is a lethal primary malignant brain tumor with no current effective treatments. The recent emergence of immuno-virotherapy and FDA approval of T-VEC have generated a great expectation towards oncolytic herpes simplex viruses (oHSVs) as a promising treatment option for GBM. Since the generation and testing of the first genetically engineered oHSV in glioma in the early 1990s, oHSV-based therapies have shown a long way of great progress in terms of anti-GBM efficacy and safety, both preclinically and clinically. Here, we revisit the literature to understand the recent advancement of oHSV in the treatment of GBM. In addition, we discuss current obstacles to oHSV-based therapies and possible strategies to overcome these pitfalls.

Inhibiting protein phosphatase 2A increases the antitumor effect of protein arginine methyltransferase 5 inhibition in models of glioblastoma

BACKGROUND

Despite multi-model therapy of maximal surgical resection, radiation, chemotherapy, and tumor treating fields, the median survival of Glioblastoma (GBM) patients is less than 15 months. Protein Arginine Methyltransferase 5 (PRMT5) catalyzes the symmetric di-methylation of arginine residues and is overexpressed in GBM. Inhibition of PRMT5 causes senescence in stem-like GBM tumor cells. LB100, a first-in-class small molecular inhibitor of Protein Phosphatase 2A (PP2A) can sensitize therapy-resistant tumor cells. Here, we tested the anti-GBM effect of concurrent PRMT5 and PP2A inhibition.

METHODS

Patient-derived primary GBM neurospheres (GBMNS), transfected with PRMT5 target-specific siRNA were treated with LB100 and subjected to in vitro assays including PP2A activity and western blot. The intracranial mouse xenograft model was used to test the in vivo antitumor efficacy of combination treatment.

RESULTS

We found that PRMT5-depletion increased PP2A activity in GBMNS. LB100 treatment significantly reduced the viability of PRMT5-depleted GBMNS compared to PRMT5 intact GBMNS. LB100 enhanced G1 cell cycle arrest induced by PRMT5-depletion. Combination therapy also increased the expression of phospho-MLKL. Necrostatin-1 rescued PRMT5-depleted cells from the cytotoxic effects of LB100, indicating that necroptosis caused the enhanced cytotoxicity of combination therapy. In the in vivo mouse tumor xenograft model, LB100 treatment combined with transient depletion of PRMT5 significantly decreased tumor size and prolonged survival, while LB100 treatment alone had no survival benefit.

CONCLUSION

Overall, combined PRMT5 and PP2A inhibition had significantly greater antitumor effects than PRMT5 inhibition alone.

Role of RAGE and Its Ligands on Inflammatory Responses to Brain Tumors

Gliomas, the most common form of brain cancer, can range from relatively slow-growing low-grade to highly aggressive glioblastoma that has a median overall survival of only 15 months despite multimodal standard therapy. Although immunotherapy with checkpoint inhibitors has significantly improved patient survival for some cancers, to date, these agents have not shown consistent efficacy against malignant gliomas. Therefore, there is a pressing need to better understand the impact of host inflammatory responses on the efficacy of emerging immunotherapy approaches for these resistant tumors. RAGE is a multi-ligand pattern recognition receptor that is activated in various inflammatory states such as diabetes, Alzheimer's disease, cystic fibrosis, and cancer. Low levels of RAGE can be found under normal physiological conditions in neurons, immune cells, activated endothelial, and vascular smooth muscle cells, but it is over-expressed under chronic inflammation due to the accumulation of its ligands. RAGE binds to a range of damage-associated molecular pattern molecules (DAMPs) including AGEs, HMGB1, S100s, and DNA which mediate downstream cellular responses that promote tumor growth, angiogenesis, and invasion. Both in vitro and in vivo studies have shown that inhibition of RAGE signaling can disrupt inflammation and cancer progression and metastasis. Here, we will review our current understanding of the role of RAGE pathway on glioma progression and how it could be exploited to improve the efficacy of immunotherapy approaches.

Disrupting the Homeostasis of High Mobility Group Protein Promotes the Systemic Movement of Bamboo mosaic virus

Viruses hijack various organelles and machineries for their replication and movement. Ever more lines of evidence indicate that specific nuclear factors are involved in systemic trafficking of several viruses. However, how such factors regulate viral systemic movement remains unclear. Here, we identify a novel role for Nicotiana benthamiana high mobility group nucleoprotein (NbHMG1/2a) in virus movement. Although infection of N. benthamiana with Bamboo mosaic virus (BaMV) decreased NbHMG1/2a expression levels, nuclear-localized NbHMG1/2a protein was shuttled out of the nucleus into cytoplasm upon BaMV infection. NbHMG1/2a knockdown or even overexpression did not affect BaMV accumulation in inoculated leaves, but it did enhance systemic movement of the virus. Interestingly, the positive regulator Rap-GTPase activation protein 1 was highly upregulated upon infection with BaMV, whereas the negative regulator thioredoxin h protein was greatly reduced, no matter if NbHMG1a/2a was silenced or overexpressed. Our findings indicate that NbHMG1/2a may have a role in plant defense responses. Once its homeostasis is disrupted, expression of relevant host factors may be perturbed that, in turn, facilitates BaMV systemic movement.

Modulating microenvironments for treating glioblastoma

Purpose of review

This review focuses on the development and progression of glioblastoma through the brain and glioma microenvironment. Specifically we highlight how the tumor microenvironment contributes to the hallmarks of cancer in hopes of offering novel therapeutic options and tools to target this microenvironment.

Recent findings

The hallmarks of cancer, which represent elements of cancers that contribute to the disease's malignancy, yet elements within the brain tumor microenvironment, such as other cellular types as well as biochemical and biophysical cues that can each uniquely affect tumor cells, have not been well-described in this context and serve as potential targets for modulation.

Summary

Here, we highlight how the brain tumor microenvironment contributes to the progression and therapeutic response of tumor cells. Specifically, we examine these contributions through the lens of Hanahan & Weinberg's Hallmarks of Cancer in order to identify potential novel targets within the brain that may offer a means to treat brain cancers, including the deadliest brain cancer, glioblastoma.

High Mobility Group Box 1 in Human Cancer

High mobility group box 1 (HMGB1) is an extremely versatile protein that is located predominantly in the nucleus of quiescent eukaryotic cells, where it is critically involved in maintaining genomic structure and function. During cellular stress, however, this multifaceted, cytokine-like protein undergoes posttranslational modifications that promote its translocation to the cytosol, from where it is released extracellularly, either actively or passively, according to cell type and stressor. In the extracellular milieu, HMGB1 triggers innate inflammatory responses that may be beneficial or harmful, depending on the magnitude and duration of release of this pro-inflammatory protein at sites of tissue injury. Heightened awareness of the potentially harmful activities of HMGB1, together with a considerable body of innovative, recent research, have revealed that excessive production of HMGB1, resulting from misdirected, chronic inflammatory responses, appears to contribute to all the stages of tumorigenesis. In the setting of established cancers, the production of HMGB1 by tumor cells per se may also exacerbate inflammation-related immunosuppression. These pro-inflammatory mechanisms of HMGB1-orchestrated tumorigenesis, as well as the prognostic potential of detection of elevated expression of this protein in the tumor microenvironment, represent the major thrusts of this review.

Enhancing Antitumor Efficacy of Heavily Vascularized Tumors by RAMBO Virus through Decreased Tumor Endothelial Cell Activation

Vascularization is a common pathology for many solid tumors, and therefore anti-angiogenic strategies are being investigated as a therapeutic target for treatment. Numerous studies are also being conducted regarding the effects of oncolytic viruses, including Imlygic^TM, an FDA approved oncolytic herpes simplex virus-1 (oHSV) for the treatment of highly vascularized tumors such as Kaposi sarcoma (NCT04065152), and brain tumors. To our knowledge, the effects of combining oncolytic HSV with angiogenesis inhibition on endothelial cell activation has not been previously described. Here, we tested the effects of Rapid Antiangiogenesis Mediated By Oncolytic Virus (RAMBO), an oHSV which expresses a potent anti-angiogenic gene Vasculostatin on endothelial cell activation in heavily vascularized solid tumors. oHSV treatment induces endothelial cell activation, which inhibits virus propagation and oncolysis in adjacent tumor cells in vitro. Consistently, this was also observed in intravital imaging of intracranial tumor-bearing mice in vivo where infected tumor endothelial cells could efficiently clear the virus without cell lysis. Quantitative real-time PCR (Q-PCR), leukocyte adhesion assay, and fluorescent microscopy imaging data, however, revealed that RAMBO virus significantly decreased expression of endothelial cell activation markers and leukocyte adhesion, which in turn increased virus replication and cytotoxicity in endothelial cells. In vivo RAMBO treatment of subcutaneously implanted sarcoma tumors significantly reduced tumor growth in mice bearing sarcoma compared to rHSVQ. In addition, histological analysis of RAMBO-treated tumor tissues revealed large areas of necrosis and a statistically significant reduction in microvessel density (MVD). This study provides strong preclinical evidence of the therapeutic benefit for the use of RAMBO virus as a treatment option for highly vascularized tumors.

Inhibition of USP14 Deubiquitinating Activity as a Potential Therapy for Tumors with p53 Deficiency

Functional elimination of p53 is a common feature of a large percentage of human malignancies. Here, we report the development of a pharmacological strategy aimed at restoring p53 function and its use for targeted therapy in p53-deficient mice. Specific inhibition of deubiquitinases ubiquitin-specific peptidase 14 (USP14) resulted in durable tumor regressions of autochthonous lymphomas and sarcomas in p53-deficient mice without affecting normal tissues, and therapeutic response was correlated with an increase in the ubiquitination of constitutive photomorphogenesis 9 (COP9) signalosome subunit 5 (COPS5), a key negative regulatory effector for p53. Inhibition of USP14 resulted in durable tumor regression through COPS5 deubiquitilation and a p53-dependent and -independent regulation mechanism by USP14. This series highlights the utility of proteasome deubiquitinating activity inhibition as a novel treatment paradigm for p53-deficient cancers. In addition, it provides preliminary evidence that inhibition of USP14 resulted in durable tumor regression through COPS5 deubiquitilation and p53-dependent and -independent regulation mechanism by USP14. These findings suggest that the deubiquitinating activity of the 19S regulatory particle is a new anticancer drug target for patients with p53 deficiency.

Oncolytic HSV therapy increases trametinib access to brain tumors and sensitizes them in vivo

BACKGROUND

Hyperactivation of the RAS-RAF-MEK-ERK signaling pathway is exploited by glioma cells to promote their growth and evade apoptosis. MEK activation in tumor cells can increase replication of ICP34.5-deleted herpes simplex virus type 1 (HSV-1), but paradoxically its activation in tumor-associated macrophages promotes a pro-inflammatory signaling that can inhibit virus replication and propagation. Here we investigated the effect of blocking MEK signaling in conjunction with oncolytic HSV-1 (oHSV) for brain tumors.

METHODS

Infected glioma cells co-cultured with microglia or macrophages treated with or without trametinib were used to test trametinib effect on macrophages/microglia. Enzyme-linked immunosorbent assay, western blotting, and flow cytometry were utilized to evaluate the effect of the combination therapy. Pharmacokinetic (PK) analysis of mouse plasma and brain tissue was used to evaluate trametinib delivery to the CNS. Intracranial human and mouse glioma-bearing immune deficient and immune competent mice were used to evaluate the antitumor efficacy.

RESULT

Oncolytic HSV treatment rescued trametinib-mediated feedback reactivation of the mitogen-activated protein kinase signaling pathway in glioma. In vivo, PK analysis revealed enhanced blood-brain barrier penetration of trametinib after oHSV treatment. Treatment by trametinib, a MEK kinase inhibitor, led to a significant reduction in microglia- and macrophage-derived tumor necrosis factor alpha (TNFα) secretion in response to oHSV treatment and increased survival of glioma-bearing mice. Despite the reduced TNFα production observed in vivo, the combination treatment activated CD8+ T-cell mediated immunity and increased survival in a glioma-bearing immune-competent mouse model.

CONCLUSION

This study provides a rationale for combining oHSV with trametinib for the treatment of brain tumors.

The Use of Murine Models for Studying Mechanistic Insights of Genomic Instability in Multiple Myeloma

Multiple myeloma (MM) is a B-cell malignancy characterized by the accumulation of clonal plasma cells in the bone marrow. In normal plasma cell development, cells undergo programmed DNA breaks and translocations, a process necessary for generation of a wide repertoire of antigen-specific antibodies. This process also makes them vulnerable for the acquisition of chromosomal defects. Well-known examples of these aberrations, already seen at time of MM diagnosis, are hyperdiploidy or the translocations involving the immunoglobulin heavy chain. Over the recent years, however, novel aspects concerning genomic instability and its role in tumor development, disease progression and nascence of refractory disease were identified. As such, genomic instability is becoming a very relevant research topic with the potential identification of novel disease pathways. In this review, we aim to describe recent studies involving murine MM models focusing on the deregulation of processes implicated in genomic instability and their clinical impact. More specifically, we will discuss chromosomal instability, DNA damage and repair responses, development of drug resistance, and recent insights into the study of clonal hierarchy using different murine MM models. Lastly, we will discuss the importance and the use of murine MM models in the pre-clinical evaluation of promising novel therapeutic agents.

Oncolytic herpes simplex virus therapy for malignant glioma: current approaches to successful clinical application

INTRODUCTION

With the approval of talimogene laherparepvec (T-VEC) for advanced malignant melanoma, virotherapy using oncolytic herpes simplex virus (oHSV) is now emerging as a viable therapeutic option for cancer patients, including malignant gliomas.

AREAS COVERED

This review summarizes the most recent literature to provide cutting-edge knowledge about preclinical and clinical development of oHSV therapy for malignant gliomas, presenting current approaches to overcome obstacles to successful clinical application of oHSV in neuro-oncology.

EXPERT OPINION

Current strategies to improve the efficacy of oHSV therapy include engineering new viruses, modulation of innate and adaptive immune responses, combination with other treatments, and developing new oHSV delivery. All of these could rapidly be translated into clinical investigations, following several clinical trials that are currently ongoing.

A Characterization of Dendritic Cells and Their Role in Immunotherapy in Glioblastoma: From Preclinical Studies to Clinical Trials

Glioblastoma (GBM) is the most common and fatal primary central nervous system malignancy in adults with a median survival of less than 15 months. Surgery, radiation, and chemotherapy are the standard of care and provide modest benefits in survival, but tumor recurrence is inevitable. The poor prognosis of GBM has made the development of novel therapies targeting GBM of paramount importance. Immunotherapy via dendritic cells (DCs) has garnered attention and research as a potential strategy to boost anti-tumor immunity in recent years. As the “professional” antigen processing and presenting cells, DCs play a key role in the initiation of anti-tumor immune responses. Pre-clinical studies in GBM have shown long-term tumor survival and immunological memory in murine models with stimulation of DC activity with various antigens and costimulatory molecules. Phase I and II clinical trials of DC vaccines in GBM have demonstrated some efficacy in improving the median overall survival with minimal to no toxicity with promising initial results from the first Phase III trial. However, there remains no standardization of vaccines in terms of which antigens are used to pulse DCs ex vivo, sites of DC injection, and optimal adjuvant therapies. Future work with DC vaccines aims to elucidate the efficacy of DC-based therapy alone or in combination with other immunotherapy adjuvants in additional Phase III trials.