Histone deacetylase 6 inhibition enhances oncolytic viral replication in glioma

Cleavage of HDAC6 to dampen its antiviral activity by nsp5 is a common strategy of swine enteric coronaviruses

HDAC6, a structurally and functionally unique member of the histone deacetylase (HDAC) family, is an important host factor that restricts viral infection. The broad-spectrum antiviral activity of HDAC6 makes it a potent antiviral agent. Previously, we found that HDAC6 functions to antagonize porcine deltacoronavirus (PDCoV), an emerging enteropathogenic coronavirus with zoonotic potential. However, the final outcome is typically a productive infection that materializes as cells succumb to viral infection, indicating that the virus has evolved sophisticated mechanisms to combat the antiviral effect of HDAC6. Here, we demonstrate that PDCoV nonstructural protein 5 (nsp5) can cleave HDAC6 at glutamine 519 (Q519), and cleavage of HDAC6 was also detected in the context of PDCoV infection. More importantly, the anti-PDCoV activity of HDAC6 was damaged by nsp5 cleavage. Mechanistically, the cleaved HDAC6 fragments (amino acids 1-519 and 520-1159) lost the ability to degrade PDCoV nsp8 due to their impaired deacetylase activity. Furthermore, nsp5-mediated cleavage impaired the ability of HDAC6 to activate RIG-I-mediated interferon responses. We also tested three other swine enteric coronaviruses (transmissible gastroenteritis virus, porcine epidemic diarrhea virus, and swine acute diarrhea syndrome-coronavirus) and found that all these coronaviruses have adopted similar mechanisms to cleave HDAC6 in both an overexpression system and virus-infected cells, suggesting that cleavage of HDAC6 is a common strategy utilized by swine enteric coronaviruses to antagonize the host's antiviral capacity. Together, these data illustrate how swine enteric coronaviruses antagonize the antiviral function of HDAC6 to maintain their infection, providing new insights to the interaction between virus and host.IMPORTANCEViral infections and host defenses are in constant opposition. Once viruses combat or evade host restriction, productive infection is achieved. HDAC6 is a broad-spectrum antiviral protein that has been demonstrated to inhibit many viruses, including porcine deltacoronavirus (PDCoV). However, whether HDAC6 is reciprocally targeted and disabled by viruses remains unclear. In this study, we used PDCoV as a model and found that HDAC6 is targeted and cleaved by nsp5, a viral 3C-like protease. The cleaved HDAC6 loses its deacetylase activity as well as its ability to degrade viral proteins and activate interferon responses. Furthermore, this cleavage mechanism is shared among other swine enteric coronaviruses. These findings shed light on the intricate interplay between viruses and HDAC6, highlighting the strategies employed by viruses to evade host antiviral defenses.

Immunomodulatory properties of HDAC6 inhibitors in cancer diseases: New chances for sophisticated drug design and treatment optimization

Histone deacetylases (HDACs) are promising targets for the design of anticancer drugs. HDAC6 is of particular interest since it is a cytoplasmic HDAC regulating the acetylation state of cancer-relevant cytoplasmic proteins such as tubulin, Hsp90, p53, and others. HDAC6 also influences the immune system, and the combination of HDAC6 inhibitors with immune therapy showed promising anticancer results. In addition, the design of new HDAC6 inhibitors led to potent anticancer drugs with immunomodulatory activities. This review describes the current state of play, and the recent developments in the research on the interactions of HDAC6 inhibitors with the immune system, and the development of new HDAC6 inhibitors with immunomodulatory activities to improve the therapy options for cancer patients.

Transgelin Promotes Glioblastoma Stem Cell Hypoxic Responses and Maintenance Through p53 Acetylation

Glioblastoma (GBM) is a lethal cancer characterized by hypervascularity and necrosis associated with hypoxia. Here, it is found that hypoxia preferentially induces the actin-binding protein, Transgelin (TAGLN), in GBM stem cells (GSCs). Mechanistically, TAGLN regulates HIF1α transcription and stabilizes HDAC2 to deacetylate p53 and maintain GSC self-renewal. To translate these findings into preclinical therapeutic paradigm, it is found that sodium valproate (VPA) is a specific inhibitor of TAGLN/HDAC2 function, with augmented efficacy when combined with natural borneol (NB) in vivo. Thus, TAGLN promotes cancer stem cell survival in hypoxia and informs a novel therapeutic paradigm.

Histone deacetylase 6's function in viral infection, innate immunity, and disease: latest advances

In the family of histone-deacetylases, histone deacetylase 6 (HDAC6) stands out. The cytoplasmic class IIb histone deacetylase (HDAC) family is essential for many cellular functions. It plays a crucial and debatable regulatory role in innate antiviral immunity. This review summarises the current state of our understanding of HDAC6's structure and function in light of the three mechanisms by which it controls DNA and RNA virus infection: cytoskeleton regulation, host innate immune response, and autophagy degradation of host or viral proteins. In addition, we summed up how HDAC6 inhibitors are used to treat a wide range of diseases, and how its upstream signaling plays a role in the antiviral mechanism. Together, the findings of this review highlight HDAC6's importance as a new therapeutic target in antiviral immunity, innate immune response, and some diseases, all of which offer promising new avenues for the development of drugs targeting the immune response.

Oncolytic herpes simplex virus armed with a bacterial GBP1 degrader improves antitumor activity

Oncolytic viruses (OVs) encoding various transgenes are being evaluated for cancer immunotherapy. Diverse factors such as cytokines, immune checkpoint inhibitors, tumor-associated antigens, and T cell engagers have been exploited as transgenes. These modifications are primarily aimed to reverse the immunosuppressive tumor microenvironment. By contrast, antiviral restriction factors that inhibit the replication of OVs and result in suboptimal oncolytic activity have received far less attention. Here, we report that guanylate-binding protein 1 (GBP1) is potently induced during HSV-1 infection and restricts HSV-1 replication. Mechanistically, GBP1 remodels cytoskeletal organization to impede nuclear entry of HSV-1 genome. Previous studies have established that IpaH9.8, a bacterial E3 ubiquitin ligase, targets GBPs for proteasomal degradation. We therefore engineered an oncolytic HSV-1 to express IpaH9.8 and found that the modified OV effectively antagonized GBP1, replicated to a higher titer in vitro and showed superior antitumor activity in vivo. Our study features a strategy for improving the replication of OVs via targeting a restriction factor and achieving promising therapeutic efficacy.

Oncolytic herpes simplex viruses for the treatment of glioma and targeting glioblastoma stem-like cells

Glioblastoma (GBM) is one of the most lethal cancers, having a poor prognosis and a median survival of only about 15 months with standard treatment (surgery, radiation, and chemotherapy), which has not been significantly extended in decades. GBM demonstrates remarkable cellular heterogeneity, with glioblastoma stem-like cells (GSCs) at the apex. GSCs are a subpopulation of GBM cells that possess the ability to self-renew, differentiate, initiate tumor formation, and manipulate the tumor microenvironment (TME). GSCs are no longer considered a static population of cells with specific markers but are quite flexible phenotypically and in driving tumor heterogeneity and therapeutic resistance. In light of these features, they are a critical target for successful GBM therapy. Oncolytic viruses, in particular oncolytic herpes simplex viruses (oHSVs), have many attributes for therapy and are promising agents to target GSCs. oHSVs are genetically-engineered to selectively replicate in and kill cancer cells, including GSCs, but not normal cells. Moreover, oHSV can induce anti-tumor immune responses and synergize with other therapies, such as chemotherapy, DNA repair inhibitors, and immune checkpoint inhibitors, to potentiate treatment effects and reduce GSC populations that are partly responsible for chemo- and radio-resistance. Herein, we present an overview of GSCs, activity of different oHSVs, clinical trial results, and combination strategies to enhance efficacy, including therapeutic arming of oHSV. Throughout, the therapeutic focus will be on GSCs and studies specifically targeting these cells. Recent clinical trials and approval of oHSV G47Δ in Japan for patients with recurrent glioma demonstrate the efficacy and promise of oHSV therapy.

Microtubules and viral infection

Microtubules (MTs) form rapidly adaptable, complex intracellular networks of filaments that not only provide structural support, but also form the tracks along which motors traffic macromolecular cargos to specific sub-cellular sites. These dynamic arrays play a central role in regulating various cellular processes including cell shape and motility as well as cell division and polarization. Given their complex organization and functional importance, MT arrays are carefully controlled by many highly specialized proteins that regulate the nucleation of MT filaments at distinct sites, their dynamic growth and stability, and their engagement with other subcellular structures and cargoes destined for transport. This review focuses on recent advances in our understanding of how MTs and their regulatory proteins function, including their active targeting and exploitation, during infection by viruses that utilize a wide variety of replication strategies that occur within different cellular sub-compartments or regions of the cell.

Emerging Nano-/Biotechnology Drives Oncolytic Virus-Activated and Combined Cancer Immunotherapy

Oncolytic viruses (OVs) as one promising antitumor methods have made important contributions to tumor immunotherapy, which arouse increasing attention. They provide the dual mechanisms including direct killing effect toward tumor cells and immune activation for elevating antitumor responses, which have been proved in many preclinical studies. Especially, natural or genetically modified viruses as clinical immune preparations have emerged as a new promising approach objective to oncology treatment. The approval of talimogene laherparepvec (T-VEC) by the U.S. Food and Drug Administration (FDA) for the therapy of advanced melanoma could be considered as a milestone achievement in the clinical translation of OV. In this review, we first discussed the antitumor mechanisms of OVs with an emphasis on targeting, replication, and propagation. We further outlined the state of the art of current OVs in tumor and underlined the activated biological effects especially including immunity. More significantly, the enhanced immune responses based on OVs were systematically discussed from different perspectives such as combination with immunotherapy, genetic engineering of OVs, integration with nanobiotechnology or nanoparticles, and antiviral response counteraction, where their principles were shed light on. The development of OVs in the clinics was also highlighted to analyze the actuality and concerns of different OV applications in clinical trials. At last, the future perspectives and challenges of OVs as an already widely accepted treatment means were discussed. This review will provide a systematic review and deep insight into OV development and also offer new opportunities and guidance pathways to drive the further clinical translation.

Anti-microbial host factor HDAC6 is antagonised by the influenza A virus through host caspases and viral PA

Histone deacetylase 6 (HDAC6), through the repertoire of its substrate proteins, plays a critical role in human physiology, and an aberrant function of HDAC6 contributes to various pathophysiological conditions. HDAC6 is also known to be an anti-microbial host factor and has been implicated in restricting or clearing the infection of various human viral and bacterial pathogens. However, the state and the mechanisms of its antagonism in infected cells are not understood. Here, we demonstrate that influenza A virus (IAV) antagonises HDAC6 by recruiting both viral and host components. We found that HDAC6 mRNA expression, and consequently, the HDAC6 polypeptide expression is downregulated in human lung epithelial cells during early stage of IAV infection but can be rescued by depleting the expression of viral polymerase acidic (PA) protein, a subunit of IAV RNA polymerase. In addition, during later stage of the infection, the HDAC6 polypeptide undergoes caspase-mediated cleavage at two sites, generating two cleaved fragments. Both these fragments disappeared when the expression of caspase 3 was depleted in infected cells, whereas only second fragment disappeared when the expression of caspase 6 was depleted. But both fragments disappeared and the level of full-length HDAC6 polypeptide was rescued when the expression of PA was depleted in infected cells. Collectively, these data indicated that IAV antagonises the HDAC6 by decreasing its expression level in infected cells, both at mRNA and polypeptide level via PA gene, which has been implicated in auxiliary functions like degradation of host mRNA and induction of apoptosis.

Histone deacetylase inhibitors enhance oncolytic herpes simplex virus therapy for malignant meningioma

Approximately 20% of meningiomas are not benign (higher grade) and tend to relapse after surgery and radiation therapy. Malignant (anaplastic) meningioma (MM) is a minor subset of high-grade meningioma that is lethal with no effective treatment options currently. Oncolytic herpes simplex virus (oHSV) is a powerful anti-cancer modality that induces both direct cell death and anti-tumor immunity, and has shown activity in preclinical models of MM. However, clinically meaningful efficacy will likely entail rational mechanistic combination approaches. We here show that epigenome modulator histone deacetylase inhibitors (HDACi) increase anti-cancer effects of oHSV in human MM models, IOMM-Lee (NF2 wild-type) and CH157 (NF2 mutant). Minimally toxic, sub-micromolar concentrations of pan-HDACi, Trichostatin A and Panobinostat, substantively increased the infectability and spread of oHSV G47Δ within MM cells in vitro, resulting in enhanced oHSV-mediated killing of target cells when infected at low multiplicity of infection (MOI). Transcriptomics analysis identified selective alteration of mRNA processing and splicing modules that might underlie the potent anti-MM effects of combining HDACi and oHSV. In vivo, HDACi treatment increased intratumoral oHSV replication and boosted the capacity of oHSV to control the growth of human MM xenografts. Thus, our work supports further translational development of the combination approach employing HDACi and oHSV for the treatment of MM.

Improving cancer immunotherapy by rationally combining oncolytic virus with modulators targeting key signaling pathways

Oncolytic viruses (OVs) represent a new class of multi-modal immunotherapies for cancer, with OV-elicited antitumor immunity being key to their overall therapeutic efficacy. Currently, the clinical effectiveness of OV as monotherapy remains limited, and thus investigators have been exploring various combinations with other anti-cancer agents and demonstrated improved therapeutic efficacy. As cancer cells have evolved to alter key signaling pathways for enhanced cell proliferation, cancer progression and metastasis, these cellular and molecular changes offer promising targets for rational cancer therapy design. In this regard, key molecules in relevant signaling pathways for cancer cells or/and immune cells, such as EGFR-KRAS (e.g., KRAS^G12C), PI3K-AKT-mTOR, ERK-MEK, JAK-STAT, p53, PD-1-PD-L1, and epigenetic, or immune pathways (e.g., histone deacetylases, cGAS-STING) are currently under investigation and have the potential to synergize with OV to modulate the immune milieu of the tumor microenvironment (TME), thereby improving and sustaining antitumor immunity. As many small molecule modulators of these signaling pathways have been developed and have shown strong therapeutic potential, here we review key findings related to both OV-mediated immunotherapy and the utility of small molecule modulators of signaling pathways in immuno-oncology. Then, we focus on discussion of the rationales and potential strategies for combining OV with selected modulators targeting key cellular signaling pathways in cancer or/and immune cells to modulate the TME and enhance antitumor immunity and therapeutic efficacy. Finally, we provide perspectives and viewpoints on the application of novel experimental systems and technologies that can propel this exciting branch of medicine into a bright future.

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.

HDAC6 is a prognostic biomarker that mediates IL-13 expression to regulate macrophage polarization through AP-1 in oral squamous cell carcinoma

Oral squamous cell carcinoma (OSCC) is a common malignant tumor worldwide that is characterized by abnormal lesions or malignant hyperplasia of soft and hard tissues in the oral cavity. Previous research has found that HDAC6 may be a potential therapeutic target for cancer patients and has the ability to regulate immune cells. However, the mechanism of HDAC6 in OSCC pathogenesis is unclear. We collected clinical samples and analyzed the level of HDAC6 in OSCC patients. The results showed that in the high HDAC6 expression group, HDAC6 expression was positively correlated with the grade of OSCC (R = 0.182, P = 0.036) and that this group had a 3.248-fold increase in the mortality risk compared with the low HDAC6 expression group (P = 0.003). Survival analysis also identified a correlation between the expression of HDAC6 and overall survival in OSCC patients, and it was found that the expression of HDAC6 was inversely correlated with survival (P ≤ 0.001). In addition, we found that HDAC6 induced IL-13 expression through AP-1, resulting in M2 polarization of macrophages. Together, these results demonstrate that the level of HDAC6 may be a useful prognostic biomarker and offer a novel immune cell-related therapeutic strategy of targeting IL-13 in OSCC.

Agent-based computational modeling of glioblastoma predicts that stromal density is central to oncolytic virus efficacy

Oncolytic viruses (OVs) are emerging cancer immunotherapy. Despite notable successes in the treatment of some tumors, OV therapy for central nervous system cancers has failed to show efficacy. We used an ex vivo tumor model developed from human glioblastoma tissue to evaluate the infiltration of herpes simplex OV rQNestin (oHSV-1) into glioblastoma tumors. We next leveraged our data to develop a computational, model of glioblastoma dynamics that accounts for cellular interactions within the tumor. Using our computational model, we found that low stromal density was highly predictive of oHSV-1 therapeutic success, suggesting that the efficacy of oHSV-1 in glioblastoma may be determined by stromal-to-tumor cell regional density. We validated these findings in heterogenous patient samples from brain metastatic adenocarcinoma. Our integrated modeling strategy can be applied to suggest mechanisms of therapeutic responses for central nervous system cancers and to facilitate the successful translation of OVs into the clinic.

Virally programmed extracellular vesicles sensitize cancer cells to oncolytic virus and small molecule therapy

Recent advances in cancer therapeutics clearly demonstrate the need for innovative multiplex therapies that attack the tumour on multiple fronts. Oncolytic or “cancer-killing” viruses (OVs) represent up-and-coming multi-mechanistic immunotherapeutic drugs for the treatment of cancer. In this study, we perform an in-vitro screen based on virus-encoded artificial microRNAs (amiRNAs) and find that a unique amiRNA, herein termed amiR-4, confers a replicative advantage to the VSVΔ51 OV platform. Target validation of amiR-4 reveals ARID1A, a protein involved in chromatin remodelling, as an important player in resistance to OV replication. Virus-directed targeting of ARID1A coupled with small-molecule inhibition of the methyltransferase EZH2 leads to the synthetic lethal killing of both infected and uninfected tumour cells. The bystander killing of uninfected cells is mediated by intercellular transfer of extracellular vesicles carrying amiR-4 cargo. Altogether, our findings establish that OVs can serve as replicating vehicles for amiRNA therapeutics with the potential for combination with small molecule and immune checkpoint inhibitor therapy.

RNA-based viruses can be engineered to express artificial microRNAs (amiRNAs). Here, the authors identify a candidate amiRNA that confers a replicative advantage to oncolytic viruses, enhancing their anticancer potency, and show that intercellular transfer of extracellular vesicles carrying the amiRNA promotes bystander killing of uninfected cancer cells.

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.

Oncolytic Virus Therapy Alters the Secretome of Targeted Glioblastoma Cells

Simple Summary

Proteins secreted by cancer cells in response to oncolytic virus anti-tumor therapy constitute the instructions for the immune cells. Yet as there are hundreds of proteins, including those encapsulated in vesicles, whose message drives the mobilization of immune cells, we aimed to decipher the instruction sent by cancer cells in response to therapy. Searching the cataloged vesicle and vesicle-free secreted proteins, we found that the proteins associated with the favorable survival of brain cancer patients were those that have the power to mobilize the immune cells. Thus, this approach established cancer-secreted contributors to the immune–therapeutic effect of the oncolytic virus.

Abstract

Oncolytic virus (OV) therapy, which is being tested in clinical trials for glioblastoma, targets cancer cells, while triggering immune cells. Yet OV sensitivity varies from patient to patient. As OV therapy is regarded as an anti-tumor vaccine, by making OV-infected cancer cells secrete immunogenic proteins, linking these proteins to transcriptome would provide a measuring tool to predict their sensitivity. A set of six patient-derived glioblastoma cells treated ex-vivo with herpes simplex virus type 1 (HSV1) modeled a clinical setting of OV infection. The cellular transcriptome and secreted proteome (separated into extracellular vesicles (EV) and EV-depleted fractions) were analyzed by gene microarray and mass-spectroscopy, respectively. Data validation and in silico analysis measured and correlated the secretome content with the response to infection and patient survival. Glioblastoma cells reacted to the OV infection in a seemingly dissimilar fashion, but their transcriptomes changed in the same direction. Therefore, the upregulation of transcripts encoding for secreted proteins implies a common thread in the response of cancer cells to infection. Indeed, the OV-driven secretome is linked to the immune response. While these proteins have distinct membership in either EV or EV-depleted fractions, it is their co-secretion that augments the immune response and associates with favorable patient outcomes.

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.

Sunitinib inhibits RNase L by destabilizing its active dimer conformation

The pseudokinase (PK) RNase L is a functional ribonuclease and plays important roles in human innate immunity. The ribonuclease activity of RNase L can be regulated by the kinase inhibitor sunitinib. The combined use of oncolytic virus and sunitinib has been shown to exert synergistic effects in anticancer therapy. In this study, we aimed to uncover the mechanism of action through which sunitinib inhibits RNase L. We solved the crystal structures of RNase L in complex with sunitinib and its analogs toceranib and SU11652. Our results showed that sunitinib bound to the ATP-binding pocket of RNase L. Unexpectedly, the αA helix linking the ankyrin repeat-domain and the PK domain affected the binding mode of sunitinib and resulted in an unusual flipped orientation relative to other structures in PDB. Molecular dynamics simulations and dynamic light scattering results support that the binding of sunitinib in the PK domain destabilized the dimer conformation of RNase L and allosterically inhibited its ribonuclease activity. Our study suggested that dimer destabilization could be an effective strategy for the discovery of RNase L inhibitors and that targeting the ATP-binding pocket in the PK domain of RNase L was an efficient approach for modulating its ribonuclease activity.

Recent Progress in Histone Deacetylase Inhibitors as Anticancer Agents

Histone Deacetylase (HDAC) inhibitors are a relatively new class of anti-cancer agents that play important roles in epigenetic or non-epigenetic regulation, inducing death, apoptosis, and cell cycle arrest in cancer cells. Recently, their use has been clinically validated in cancer patients resulting in the approval by the FDA of four HDAC inhibitors, vorinostat, romidepsin, belinostat and panobinostat, used for the treatment of cutaneous/peripheral T-cell lymphoma and multiple myeloma. Many more HDAC inhibitors are at different stages of clinical development for the treatment of hematological malignancies as well as solid tumors. Also, clinical trials of several HDAC inhibitors for use as anti-cancer drugs (alone or in combination with other anti-cancer therapeutics) are ongoing. In the intensifying efforts to discover new, hopefully, more therapeutically efficacious HDAC inhibitors, molecular modelingbased rational drug design has played an important role. In this review, we summarize four major structural classes of HDAC inhibitors (hydroxamic acid derivatives, aminobenzamide, cyclic peptide and short-chain fatty acids) that are in clinical trials and different computer modeling tools available for their structural modifications as a guide to discover additional HDAC inhibitors with greater therapeutic utility.

Oncolytic Virotherapy for Malignant Tumor: Current Clinical Status

Oncolytic viruses, as novel biological anti-tumor agents, provide anti-tumor therapeutic effects by different mechanisms including directly selective tumor cell lysis and secondary systemic anti-tumor immune responses. Some wide-type and genetically engineered oncolytic viruses have been applied in clinical trials. Among them, T-Vec has a significant therapeutic effect on melanoma patients and received the approval of the US Food and Drug Administration (FDA) as the first oncolytic virus to treat cancer in the US. However, the mechanisms of virus interaction with tumor and immune systems have not been clearly elucidated and there are still no "gold standards" for instructions of virotherapy in clinical trials. This Review collected the recent clinical trials data from 2005 to summarize the basic oncolytic viruses biology, describe the application in recent clinical trials, and discuss the challenges in the application of oncolytic viruses in clinical trials.

Protocol Optimization for the Production of the Non-Cytotoxic JΔNI5 HSV Vector Deficient in Expression of Immediately Early Genes

Non-toxic herpes simplex virus (HSV) vectors can be generated by functional deletion of all immediate-early (IE) genes, providing a benign vehicle with potential for gene therapy. However, deletion of multiple IE genes raises manufacturing concerns and thus limits clinical application of these vectors. To address this issue, we previously developed a novel production cell line, called U2OS-ICP4/27, by lentiviral transduction of human osteosarcoma U2OS cells with two essential HSV IE genes, ICP4 and ICP27. To optimize the process of vector manufacturing on this platform, we evaluated several cell culture parameters of U2OS-ICP4/27 for high-titer and -quality production of non-toxic HSV vectors, revealing that the yields and functionality of these vectors can be significantly influenced by culturing conditions. We also found that several chemical compounds can enhance the replication of non-toxic HSV vectors and their release from producer cells into the supernatants. Notably, the vector produced by our optimized protocol displayed a greatly improved vector yield and quality and showed elevated transgene expression in cultures of primary dorsal root ganglion neurons. Taken together, our optimized production approach emerges as a relevant protocol for high-yield and high-quality preparation of non-toxic HSV-based gene therapy vectors.

Herpes Simplex Virus: The Hostile Guest That Takes Over Your Home

Alpha (α)-herpesviruses (HSV-1 and HSV-2), like other viruses, are obligate intracellular parasites. They hijack the cellular machinery to survive and replicate through evading the defensive responses by the host. The viral genome of herpes simplex viruses (HSVs) contains viral genes, the products of which are destined to exploit the host apparatus for their own existence. Cellular modulations begin from the entry point itself. The two main gateways that the virus has to penetrate are the cell membrane and the nuclear membrane. Changes in the cell membrane are triggered when the glycoproteins of HSV interact with the surface receptors of the host cell, and from here, the components of the cytoskeleton take over. The rearrangement in the cytoskeleton components help the virus to enter as well as transport to the nucleus and back to the cell membrane to spread out to the other cells. The entire carriage process is also mediated by the motor proteins of the kinesin and dynein superfamily and is directed by the viral tegument proteins. Also, the virus captures the cell’s most efficient cargo carrying system, the endoplasmic reticulum (ER)–Golgi vesicular transport machinery for egress to the cell membrane. For these reasons, the host cell has its own checkpoints where the normal functions are halted once a danger is sensed. However, a cell may be prepared for the adversities from an invading virus, and it is simply commendable that the virus has the antidote to these cellular strategies as well. The HSV viral proteins are capable of limiting the use of the transcriptional and translational tools for the cell itself, so that its own transcription and translation pathways remain unhindered. HSV prefers to constrain any self-destruction process of the cell—be it autophagy in the lysosome or apoptosis by the mitochondria, so that it can continue to parasitize the cell for its own survival. This review gives a detailed account of the significance of compartmentalization during HSV pathogenesis. It also highlights the undiscovered areas in the HSV cell biology research which demand attention for devising improved therapeutics against the infection.

Glioblastoma infiltration of both tumor- and virus-antigen specific cytotoxic T cells correlates with experimental virotherapy responses

The mode of action for oncolytic viruses (OVs) in cancer treatment is thought to depend on a direct initial cytotoxic effect against infected tumor cells and subsequent activation of immune cell responses directed against the neoplasm. To study both of these effects in a mouse model of glioblastoma (GBM), we employed murine GBM cells engineered to constitutively express the type I Herpes Simplex Virus (HSV1) HSV-1 receptor, nectin-1, to allow for more efficient infection and replication by oncolytic HSV (oHSV). These cells were further engineered with a surrogate tumor antigen to facilitate assays of T cell activity. We utilized MRI-based volumetrics to measure GBM responses after injection with the oHSV and bioluminescent imaging (BLI) to determine oHSV replicative kinetics in the injected tumor mass. We found increased infiltration of both surrogate tumor antigen- and oHSV antigen-specific CD8+ T cells within 7 days after oHSV injection. There was no increase in tumor infiltrating CD8+ T cells expressing “exhaustion” markers, yet oHSV infection led to a reduction in PD-1+ CD8+ T cells in injected GBMs and an increase in IFNγ+ CD8+ T cells. There was a significant direct correlation between oHSV-mediated reduction in GBM volume and increased infiltration of both viral and tumor antigen-specific CD8+ T cells, as well as oHSV intratumoral gene activity. These findings imply that CD8+ T cell cytotoxicity against both tumor and viral antigens as well as intratumoral oHSV gene expression are important in oHSV-mediated GBM therapy.

Further investigation of the potential anti-neoplastic, anti-inflammatory and immunomodulatory actions of phenoxybenzamine using the Broad Institute CLUE platform.. [DOI: 10.1101/767392] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Previous clinical studies with the FDA-approved alpha-adrenergic antagonist, phenoxybenzamine, showed apparent efficacy to reverse the symptoms and disabilities of the neuropathic condition, Complex Regional Pain Syndrome; also, the anatomic spread and intensity of this syndrome has a proliferative character and it was proposed that phenoxybenzamine may have an anti-inflammatory, immunomodulatory mode of action. A previous study gave evidence that phenoxybenzamine had anti-proliferative activity in suppression of growth in several human tumor cell cultures. The same report demonstrated that the drug possessed significant histone deacetylase inhibitory activity. Utilizing the Harvard/Massachusetts Institute of Technology Broad Institute genomic database, CLUE, the present study suggests that the gene expression signature of phenoxybenzamine in malignant cell lines is consistent with anti-inflammatory/immunomodulatory activity and suppression of tumor expansion by several possible mechanisms of action. Of particular note, phenoxybenzamine demonstrated signatures that were highly similar to those with glucocorticoid agonist activity. Also, gene expression signatures of phenoxbenzamine were consistent with several agents in each case that were known to suppress tumor proliferation, notably, protein kinase C inhibitors, Heat Shock Protein inhibitors, epidermal growth factor receptor inhibitors, and glycogen synthase kinase inhibitors. Searches in CLUE also confirmed the earlier observations of strong similarities between gene expression signatures of phenoxybenzamine and several histone deacetylase inhibitors.

Clinical Infections by Herpesviruses in Patients Treated with Valproic Acid: A Nested Case-Control Study in the Spanish Primary Care Database, BIFAP

The objective of this study is to evaluate the risk of clinical infections by herpesviruses in patients exposed to valproic acid (VPA). We performed a case-control study nested in a primary cohort selected from the Spanish primary care population-based research database BIFAP (Base de datos para la Investigación Farmacoepidemiológica en Atención Primaria) over the period 2001–2015. The events of interest were those diseases caused by any herpesviruses known to infect humans. For each case, up to 10 controls per case matched by age, gender, and calendar date were randomly selected. A conditional logistic regression was used to compute adjusted odds ratios (OR) and their 95% confidence intervals (95% CI). Current use of VPA was associated with a trend towards a reduced risk of clinical infections by herpesviruses as compared with non-users (OR 0.84; CI 95% 0.7–1.0; p = 0.057). Among current users, a trend to a decreased risk with treatment durations longer than 90 days was also observed. The results show a trend to a reduced risk of clinical infection by herpesviruses in patients exposed to VPA. These results are consistent with those in vitro studies showing that, in cultured cells, VPA can inhibit the production of the infectious progeny of herpesviruses. This study also shows the efficient use of electronic healthcare records for clinical exploratory research studies.

Histone deacetylase 6 promotes growth of glioblastoma through the MKK7/JNK/c-Jun signaling pathway

Histone deacetylase 6 (HDAC6) activity contributes to the malignant proliferation, invasion, and migration of glioma cells (GCs), but the molecular mechanisms underlying the processes remains elusive. Here, we reported that HDAC6 inhibition by Ricolinostat (ACY-1215) or CAY10603 led to a remarkable decrease in the phosphorylation of c-Jun N-terminal kinase (JNK) and c-Jun, which preceded its suppressive effects on glioma cell growth. Further investigation showed that these effects resulted from HDAC6 inhibitor-induced suppression of MAPK kinase 7 (MKK7), which was identified to be critical for JNK activation and exerts the oncogenic roles in GCs. Selectively silencing HDAC6 by siRNAs had the same responses, whereas transient transfections expressing HDAC6 promoted MKK7 expression. Interestingly, by performing Q-PCR, HDAC6 inhibition did not cause a down-regulation of MKK7 mRNA level, whereas the suppressive effects on MKK7 protein can be efficiently blocked by the proteasomal inhibitor MG132. As a further test, elevating MKK7-JNK activity was sufficient to rescue HDAC6 inhibitor-mediated-suppressive effects on c-Jun activation and the malignant features. The suppression of both MKK7 expression and JNK/c-Jun activities was involved in the tumor-growth inhibitory effects induced by CAY10603 in U87-xenograft mice. Collectively, our findings provide new insights into the molecular mechanism of glioma malignancy regarding HDAC6 in the selective regulation of MKK7 expression and JNK/c-Jun activity. MKK7 protein stability critically depends on HDAC6 activity, and inhibition of HDAC6 probably presents a potential strategy for suppressing the oncogenic roles of MKK7/JNK/c-Jun axis in GCs.

Oncolytic herpes simplex virus immunotherapy for brain tumors: current pitfalls and emerging strategies to overcome therapeutic resistance

Malignant tumors of the central nervous system (CNS) continue to be a leading cause of cancer-related mortality in both children and adults. Traditional therapies for malignant brain tumors consist of surgical resection and adjuvant chemoradiation; such approaches are often associated with extreme morbidity. Accordingly, novel, targeted therapeutics for neoplasms of the CNS, such as immunotherapy with oncolytic engineered herpes simplex virus (HSV) therapy, are urgently warranted. Herein, we discuss treatment challenges related to HSV virotherapy delivery, entry, replication, and spread, and in so doing focus on host antiviral immune responses and the immune microenvironment. Strategies to overcome such challenges including viral re-engineering, modulation of the immunoregulatory microenvironment and combinatorial therapies with virotherapy, such as checkpoint inhibitors, radiation, and vaccination are also examined in detail.

Amidic derivatives of valproic acid, valpromide and valnoctamide, inhibit HSV-1 infection in oligodendrocytes

Herpes simplex virus type 1 (HSV-1) is a ubiquitous infectious agent that can establish latency in neurons, and in some cases, viral retrograde transport results in infection of the central nervous system (CNS). Several antivirals have been identified with the ability to inhibit HSV-1 replication in human cells to a greater or lesser degree, most of which are nucleoside analogues that unfortunately exhibit teratogenic potential, embryotoxicity, carcinogenic or antiproliferative activities and resistances in immunocompromised patients, specially. In the present study, we assessed two amidic derivatives of valproic acid (VPA) - valpromide (VPD) and valnoctamide (VCD) - which are already used in clinic treatments, as feasible HSV-1 antivirals in glial cells. Both VPD and VCD have exhibited increased efficacy in bipolar disorders and as anticonvulsant drugs compared to VPA, while being less teratogenic and hepatotoxic. Cytotoxicity assays carried out in our laboratory showed that VPD and VCD were not toxic in a human oligodendroglioma cell line (HOG), at least at the concentrations established for human treatments. Infectivity assays showed a significant inhibition of HSV-1 infection in HOG cells after VPD and VCD treatment, being more pronounced in VPD-treated cells, comparable to the effects obtained with acyclovir. Furthermore, the same antiherpetic effects of VPD were observed in other oligodendrocytic cell lines and rat primary oligodendrocytes (OPCs), confirming the results obtained in HOG cells. Altogether, our results allow us to propose VPD as a potential antiherpetic drug that is able to act directly on oligodendrocytes of the CNS.

Herpesvirus acts with the cytoskeleton and promotes cancer progression

The cytoskeleton is a complex fibrous reticular structure composed of microfilaments, microtubules and intermediate filaments. These components coordinate morphology support and intracellular transport that is involved in a variety of cell activities, such as cell proliferation, migration and differentiation. In addition, the cytoskeleton also plays an important role in viral infection. During an infection by a Herpesvirus, the virus utilizes microfilaments to enter cells and travel to the nucleus by microtubules; the viral DNA replicates with the help of host microfilaments; and the virus particles start assembling with a capsid in the cytoplasm before egress. The cytoskeleton changes in cells infected with Herpesvirus are made to either counteract or obey the virus, thereby promote cell transforming into cancerous ones. This article aims to clarify the interaction between the virus and cytoskeleton components in the process of Herpesvirus infection and the molecular motor, cytoskeleton-associated proteins and drugs that play an important role in the process of a Herpesvirus infection and carcinogenesis process.

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.

Regulation of Chemokines and Cytokines by Histone Deacetylases and an Update on Histone Decetylase Inhibitors in Human Diseases

Histone acetyltransferases (HATs) and histone deacetylases (HDACs) counteract with each other to regulate gene expression by altering chromatin structure. Aberrant HDAC activity was reported in many human diseases including wide range of cancers, viral infections, cardiovascular complications, auto-immune diseases and kidney diseases. HDAC inhibitors are small molecules designed to block the malignant activity of HDACs. Chemokines and cytokines control inflammation, immunological and other key biological processes and are shown to be involved in various malignancies. Various HDACs and HDAC inhibitors were reported to regulate chemokines and cytokines. Even though HDAC inhibitors have remarkable anti-tumor activity in hematological cancers, they are not effective in treating many diseases and many patients relapse after treatment. However, the role of HDACs and cytokines in regulating these diseases still remain unclear. Therefore, understanding exact mechanisms and effector functions of HDACs are urgently needed to selectively inhibit them and to establish better a platform to combat various malignancies. In this review, we address regulation of chemokines and cytokines by HDACs and HDAC inhibitors and update on HDAC inhibitors in human diseases.

[On the road to deciphering the tubulin code: focus on acetylation and detyrosination]

Microtubules are cytoskeletal fibers formed by the assembly of α- and β-tubulin heterodimers. They contribute to cell morphology, mobility and polarity, as well as to cellular transport processes and cell division. The microtubular network constantly adapts to cellular needs and may be composed of very dynamic or more stable microtubules. To regulate their diverse functions in a spatio-temporal manner, microtubules are subjected to numerous reversible post-translational modifications, which generate the "tubulin code". This review focuses on two modifications characteristic of stable microtubules - acetylation and detyrosination of α-tubulin - and their deregulation in certain pathologies.

DNA-PK inhibition synergizes with oncolytic virus M1 by inhibiting antiviral response and potentiating DNA damage

Oncolytic virotherapy is a promising therapeutic strategy that uses replication-competent viruses to selectively destroy malignancies. However, the therapeutic effect of certain oncolytic viruses (OVs) varies among cancer patients. Thus, it is necessary to overcome resistance to OVs through rationally designed combination strategies. Here, through an anticancer drug screening, we show that DNA-dependent protein kinase (DNA-PK) inhibition sensitizes cancer cells to OV M1 and improves therapeutic effects in refractory cancer models in vivo and in patient tumour samples. Infection of M1 virus triggers the transcription of interferons (IFNs) and the activation of the antiviral response, which can be abolished by pretreatment of DNA-PK inhibitor (DNA-PKI), resulting in selectively enhanced replication of OV M1 within malignancies. Furthermore, DNA-PK inhibition promotes the DNA damage response induced by M1 virus, leading to increased tumour cell apoptosis. Together, our study identifies the combination of DNA-PKI and OV M1 as a potential treatment for cancers.

Oncolytic virotherapy is a promising strategy for cancer treatment. In this study, the authors demonstrate that DNA-dependent protein kinase (DNA-PK) inhibition sensitizes cancer cells to M1 virus and improves therapeutic effects in refractory cancer models in vivo and in patient tumour samples.

A Critical Overview of Targeted Therapies for Glioblastoma

Over the past century, treatment of malignant tumors of the brain has remained a challenge. Refinements in neurosurgical techniques, discovery of powerful chemotherapeutic agents, advances in radiotherapy, applications of biotechnology, and improvements in methods of targeted delivery have led to some extension of length of survival of glioblastoma patients. Refinements in surgery are mentioned because most of the patients with glioblastoma undergo surgery and many of the other innovative therapies are combined with surgery. However, cure of glioblastoma has remained elusive because it requires complete destruction of the tumor. Radical surgical ablation is not possible in the brain and even a small residual tumor leads to rapid recurrence that eventually kills the patient. Blood-brain barrier (BBB) comprising brain endothelial cells lining the cerebral microvasculature, limits delivery of drugs to the brain. Even though opening of the BBB in tumor core occurs locally, BBB limits systemic chemotherapy especially at the tumor periphery, where tumor cells invade normal brain structure comprising intact BBB. Comprehensive approaches are necessary to gain maximally from promising targeted therapies. Common methods used for critical evaluation of targeted therapies for glioblastoma include: (1) novel methods for targeted delivery of chemotherapy; (2) strategies for delivery through BBB and blood-tumor barriers; (3) innovations in radiotherapy for selective destruction of tumor; (4) techniques for local destruction of tumor; (5) tumor growth inhibitors; (6) immunotherapy; and (7) cell/gene therapies. Suggestions for improvements in glioblastoma therapy include: (1) controlled targeted delivery of anticancer therapy to glioblastoma through the BBB using nanoparticles and monoclonal antibodies; (2) direct introduction of genetically modified bacteria that selectively destroy cancer cells but spare the normal brain into the remaining tumor after resection; (3) use of better animal models for preclinical testing; and (4) personalized/precision medicine approaches to therapy in clinical trials and translation into practice of neurosurgery and neurooncology. Advances in these techniques suggest optimism for the future management of glioblastoma.

Arming an Oncolytic Herpes Simplex Virus Type 1 with a Single-chain Fragment Variable Antibody against PD-1 for Experimental Glioblastoma Therapy

PURPOSE

Glioblastoma (GBM) is resistant to standard of care. Immune checkpoints inhibitors (such as anti-PD-1 mAbs) efficiently restore antitumor T-cell activity. We engineered a new oncolytic herpes simplex virus (oHSV) expressing a single-chain antibody against PD-1 (scFvPD-1) to evaluate its efficacy in mouse models of GBM.

EXPERIMENTAL DESIGN

NG34scFvPD-1 expresses the human GADD34 gene transcriptionally controlled by the Nestin promoter to allow replication in GBM cells and a scFvPD-1 cDNA transcriptionally controlled by the CMV promoter. ELISA assays were performed to detect binding of scFvPD-1 to mouse and human PD-1. In vitro cytotoxicity and replication assays were performed to measure NG34scFvPD-1 oncolysis, and scFvPD-1 expression and secretion were determined. In vivo survival studies using orthotopic mouse GBM models were performed to evaluate the therapeutic potency of NG34scFvPD-1.

RESULTS

NG34scFvPD-1-infected GBM cells express and secrete scFvPD-1 that binds mouse PD-1. The introduction of the scFvPD-1 sequence in the viral backbone does not alter the oncolytic properties of NG34scFvPD-1. In situ NG34scFvPD-1 treatment improved the survival with a tail of durable survivorship in 2 syngeneic immunocompetent mouse models of GBM. Mice that survived the first GBM challenge rejected the second challenge of GBM when implanted in the contralateral hemisphere. However, this was not true when athymic mice were employed as the recipients of the second challenge, consistent with the need for an intact immune system to obtain a memory response.

CONCLUSIONS

NG34scFvPD-1 treatment induces a durable antitumor response in 2 preclinical mouse models of GBM with evidence for antitumor memory.

The Involvement of Histone H3 Acetylation in Bovine Herpesvirus 1 Replication in MDBK Cells

During bovine herpesvirus 1 (BoHV-1) productive infection in cell cultures, partial of intranuclear viral DNA is present in nucleosomes, and viral protein VP22 associates with histones and decreases histone H4 acetylation, indicating the involvement of histone H4 acetylation in virus replication. In this study, we demonstrated that BoHV-1 infection at the late stage (at 24 h after infection) dramatically decreased histone H3 acetylation [at residues K9 (H3K9ac) and K18 (H3K18ac)], which was supported by the pronounced depletion of histone acetyltransferases (HATs) including CBP/P300 (CREB binding protein and p300), GCN5L2 (general control of amino acid synthesis yeast homolog like 2) and PCAF (P300/CBP-associated factor). The depletion of GCN5L2 promoted by virus infection was partially mediated by ubiquitin-proteasome pathway. Interestingly, the viral replication was enhanced by HAT (histone acetyltransferase) activator CTPB [N-(4-Chloro-3-trifluoromethylphenyl)-2-ethoxy-6-pentadecylbenzamide], and vice versa, inhibited by HAT inhibitor Anacardic acid (AA), suggesting that BoHV-1 may take advantage of histone acetylation for efficient replication. Taken together, we proposed that the HAT-dependent histone H3 acetylation plays an important role in BoHV-1 replication in MDBK (Madin-Darby bovine kidney) cells.

Histone deacetylase 6 in cancer

Histone acetylation and deacetylation are important epigenetic mechanisms that regulate gene expression and transcription. Histone deacetylase 6 (HDAC6) is a unique member of the HDAC family that not only participates in histone acetylation and deacetylation but also targets several nonhistone substrates, such as α-tubulin, cortactin, and heat shock protein 90 (HSP90), to regulate cell proliferation, metastasis, invasion, and mitosis in tumors. Furthermore, HDAC6 also upregulates several critical factors in the immune system, such as program death receptor-1 (PD-1) and program death receptor ligand-1 (PD-L1) receptor, which are the main targets for cancer immunotherapy. Several selective HDAC6 inhibitors are currently in clinical trials for cancer treatment and bring hope for patients with malignant tumors. A fuller understanding of HDAC6 as a critical regulator of many cellular pathways will help further the development of targeted anti-HDAC6 therapies. Here, we review the unique features of HDAC6 and its role in cancer, which make HDAC6 an appealing drug target.

Anti-tumor activity of phenoxybenzamine and its inhibition of histone deacetylases

The principal finding from this study was the recognition that the α-adrenergic antagonist, phenoxybenzamine, possesses histone deacetylase inhibitory activity. Phenoxybenzamine is approved by the United States Food and Drug Administration for the treatment of hypertensive crises associated with tumors of the adrenal medulla, pheochromocytomas. It has several "off label" indications relative to its capacity to relax vascular smooth muscle and smooth muscle of the urogenital tract. The drug also has a long history of apparent efficacy in ameliorating, and perhaps reversing, the severe symptoms of neuropathic pain syndromes. Our interest in this feature of the drug relates to the fact that certain types of neuropathic pain, in particular complex regional pain syndrome, demonstrate a proliferative nature, with the capacity to spread from an injured limb, for example, to a non-injured limb and perhaps to essentially the entire body. Sensory neuronal sprouting in the spinal cord has been observed under conditions where there is a high sensory input from painful stimuli. Searches of gene expression signatures in the BroadBuild02 Molecular Signature Database using their connectivity map software suggested that phenoxybenzamine may have histone deacetylase inhibitory activity. Studies by others have reported inhibitory effects of phenoxybenzamine on growth, invasion and migration of human tumor cell cultures and, in one study, inhibition of tumor expansion in animal experiments. Inhibitory effects on human tumor cell cultures are also reported in the present study. Phenoxybenzamine was also found to have histone deacetylase inhibitory activity; histone deacetylase isoforms 5, 6, and 9 were the most sensitive to inhibition by phenoxybenzamine. The importance of elevated levels of these isoforms as biomarkers of poor prognosis in human malignant disease, and the recognized suppression of tumor growth that may accrue from their inhibition, opens consideration of possible translation of phenoxybenzamine to new clinical applications. This might be facilitated by the fact that phenoxybenzamine is already an approved drug entity. There appears to be no previous report of the activity of phenoxybenzamine as a histone deacetylase inhibitor.

Toxicity and Efficacy of a Novel GADD34-expressing Oncolytic HSV-1 for the Treatment of Experimental Glioblastoma

Purpose: Glioblastoma (GBM) is the most common primary central nervous system cancer in adults. Oncolytic HSV-1 (oHSV) is the first FDA-approved gene therapy approach for the treatment of malignant melanoma. For GBM, oHSVs need to be engineered to replicate within and be toxic to the glial tumor but not to normal brain parenchymal cells. We have thus engineered a novel oHSV to achieve these objectives.Experimental Design: NG34 is an attenuated HSV-1 with deletions in the genes encoding viral ICP6 and ICP34.5. These mutations suppress virus replication in nondividing brain neurons. NG34 expresses the human GADD34 gene under transcriptional control of a cellular Nestin gene promoter/enhancer element, whose expression occurs selectively in GBM. In vitro cytotoxicity assay and survival studies with mouse models were performed to evaluate therapeutic potency of NG34 against glioblastoma. In vivo neurotoxicity evaluation of NG34 was tested by intracerebral inoculation.Results: NG34 replicates in GBM cells in vitro with similar kinetics as those exhibited by an oHSV that is currently in clinical trials (rQNestin34.5). Dose-response cytotoxicity of NG34 in human GBM panels was equivalent to or improved compared with rQNestin34.5. The in vivo efficacy of NG34 against two human orthotopic GBM models in athymic mice was similar to that of rQNestin34.5, whereas intracerebral injection of NG34 in the brains of immunocompetent and athymic mice showed significantly better tolerability. NG34 was also effective in a syngeneic mouse glioblastoma model.Conclusions: A novel oHSV encoding GADD34 is efficacious and relatively nontoxic in mouse models of GBM. Clin Cancer Res; 24(11); 2574-84. ©2018 AACR.

Epigenetic agents in combined anticancer therapy

In the last decade, epigenetic drugs (such as inhibitors of DNA methyltransferases and histone deacetylases) have been intensively used for cancer treatment. Their applications have shown high anticancer effectivity and tolerable side effects. However, they are unfortunately not effective in the treatment of some types and phenotypes of cancers. Nevertheless, several studies have demonstrated that problems of drug efficacy can be overcome through the combined application of therapeutic modulates. Therefore, combined applications of epigenetic agents with chemotherapy, radiation therapy, immunotherapy, oncolytic virotherapy and hyperthermia have been presented. This review summarizes and discusses the general principles of this approach, as introduced and supported by numerous examples. In addition, predictions of the future potential applications of this methodology are included.

Selective Inhibition of Histone Deacetylation in Melanoma Increases Targeted Gene Delivery by a Bacteriophage Viral Vector

The previously developed adeno-associated virus/phage (AAVP) vector, a hybrid between M13 bacteriophage (phage) viruses that infect bacteria only and human Adeno-Associated Virus (AAV), is a promising tool in targeted gene therapy against cancer. AAVP can be administered systemically and made tissue specific through the use of ligand-directed targeting. Cancer cells and tumor-associated blood vessels overexpress the αν integrin receptors, which are involved in tumor angiogenesis and tumor invasion. AAVP is targeted to these integrins via a double cyclic RGD4C ligand displayed on the phage capsid. Nevertheless, there remain significant host-defense hurdles to the use of AAVP in targeted gene delivery and subsequently in gene therapy. We previously reported that histone deacetylation in cancer constitutes a barrier to AAVP. Herein, to improve AAVP-mediated gene delivery to cancer cells, we combined the vector with selective adjuvant chemicals that inhibit specific histone deacetylases (HDAC). We examined the effects of the HDAC inhibitor C1A that mainly targets HDAC6 and compared this to sodium butyrate, a pan-HDAC inhibitor with broad spectrum HDAC inhibition. We tested the effects on melanoma, known for HDAC6 up-regulation, and compared this side by side with a normal human kidney HEK293 cell line. Varying concentrations were tested to determine cytotoxic levels as well as effects on AAVP gene delivery. We report that the HDAC inhibitor C1A increased AAVP-mediated transgene expression by up to ~9-fold. These findings indicate that selective HDAC inhibition is a promising adjuvant treatment for increasing the therapeutic value of AAVP.

Glycosylation Changes in Brain Cancer

Protein glycosylation is a posttranslational modification that affects more than half of all known proteins. Glycans covalently bound to biomolecules modulate their functions by both direct interactions, such as the recognition of glycan structures by binding partners, and indirect mechanisms that contribute to the control of protein conformation, stability, and turnover. The focus of this Review is the discussion of aberrant glycosylation related to brain cancer. Altered sialylation and fucosylation of N- and O-glycans play a role in the development and progression of brain cancer. Additionally, aberrant O-glycan expression has been implicated in brain cancer. This Review also addresses the clinical potential and applications of aberrant glycosylation for the detection and treatment of brain cancer. The viable roles glycans may play in the development of brain cancer therapeutics are addressed as well as cancer-glycoproteomics and personalized medicine. Glycoprotein alterations are considered as a hallmark of cancer while high expression in body fluids represents an opportunity for cancer assessment.

Biomarkers and therapeutic advances in glioblastoma multiforme

Glioblastoma multiforme (GBM) is a malignant tumor within the brain. Generally classified as primary and secondary with several different subtypes, ample molecular biomarkers have risen throughout the years which have garnered the attention of researchers. The advancements in genomics and proteomics have allowed researchers to gather prominent molecular biomarkers. All these biomarkers are gathered by means of biopsy or bodily fluid sample collection and are quantitatively analyzed by polymerase chain reaction coupled with other computational technologies. This review highlights the significance, regulation and prevalence of molecular biomarkers such as O⁶ -methylguanine-DNA methyltransferase, epidermal growth factor receptor vIII, isocitrate dehydrogenase mutation and several others which expressed differently in different types and molecular subtypes of GBM. The discoveries and roles of GBM-specific microRNAs including miR-21 and miR-10b as biomarkers with promising prognostic values were also delineated. The role and mechanism of biomarkers in GBM tumorigenesis are essential in the development of therapy for patients suffering from the disease itself. Thus, this review also discusses the mechanisms, effects and limitations of therapy such as temozolomide, viral gene transfer, biomarker-based vaccines or even engineered T cells for more specific responses. Biomarkers have displayed a high value and could eventually be utilized as drug targets. It is hoped that by combining different aspects of the disease which present with different biomarkers could lead to the development of a robust, effective and innovative take on GBM therapy.

Microtubule Regulation and Function during Virus Infection

Microtubules (MTs) form a rapidly adaptable network of filaments that radiate throughout the cell. These dynamic arrays facilitate a wide range of cellular processes, including the capture, transport, and spatial organization of cargos and organelles, as well as changes in cell shape, polarity, and motility. Nucleating from MT-organizing centers, including but by no means limited to the centrosome, MTs undergo rapid transitions through phases of growth, pause, and catastrophe, continuously exploring and adapting to the intracellular environment. Subsets of MTs can become stabilized in response to environmental cues, acquiring distinguishing posttranslational modifications and performing discrete functions as specialized tracks for cargo trafficking. The dynamic behavior and organization of the MT array is regulated by MT-associated proteins (MAPs), which include a subset of highly specialized plus-end-tracking proteins (+TIPs) that respond to signaling cues to alter MT behavior. As pathogenic cargos, viruses require MTs to transport to and from their intracellular sites of replication. While interactions with and functions for MT motor proteins are well characterized and extensively reviewed for many viruses, this review focuses on MT filaments themselves. Changes in the spatial organization and dynamics of the MT array, mediated by virus- or host-induced changes to MT regulatory proteins, not only play a central role in the intracellular transport of virus particles but also regulate a wider range of processes critical to the outcome of infection.

Developing selective histone deacetylases (HDACs) inhibitors through ebselen and analogs

Histone deacetylases (HDACs) are key regulators of gene expression in cells and have been investigated as important therapeutic targets for cancer and other diseases. Different subtypes of HDACs appear to play disparate roles in the cells and are associated with specific diseases. Therefore, substantial effort has been made to develop subtype-selective HDAC inhibitors. In an effort to discover existing scaffolds with HDAC inhibitory activity, we screened a drug library approved by the US Food and Drug Administration and a National Institutes of Health Clinical Collection compound library in HDAC enzymatic assays. Ebselen, a clinical safe compound, was identified as a weak inhibitor of several HDACs, including HDAC1, HDAC3, HDAC4, HDAC5, HDAC6, HDAC7, HDAC8, and HDAC9 with half maximal inhibitory concentrations approximately single digit of µM. Two ebselen analogs, ebselen oxide and ebsulfur (a diselenide analog of ebselen), also inhibited these HDACs, however with improved potencies on HDAC8. Benzisothiazol, the core structure of ebsulfur, specifically inhibited HDAC6 at a single digit of µM but had no inhibition on other HDACs. Further efforts on structure-activity relationship based on the core structure of ebsulfur led to the discovery of a novel class of potent and selective HDAC6 inhibitors with RBC-2008 as the lead compound with single-digit nM potency. This class of histone deacetylase inhibitor features a novel pharmacophore with an ebsulfur scaffold selectively targeting HDAC6. Consistent with its inhibition on HDAC6, RBC-2008 significantly increased the acetylation levels of α-tubulin in PC-3 cells. Furthermore, treatment with these compounds led to cell death of multiple tumor cell lines in a dose-dependent manner. These results demonstrated that ebselen and ebsulfur analogs are inhibitors of HDACs, supporting further preclinical development of this class of compounds for potential therapeutic applications.

Cellular defence or viral assist: the dilemma of HDAC6

Histone deacetylase 6 (HDAC6) is a unique cytoplasmic deacetylase that regulates various important biological processes by preventing protein aggregation and deacetylating different non-histone substrates including tubulin, heat shock protein 90, cortactin, retinoic acid inducible gene I and β-catenin. Growing evidence has indicated a dual role for HDAC6 in viral infection and pathogenesis: HDAC6 may represent a host defence mechanism against viral infection by modulating microtubule acetylation, triggering antiviral immune response and stimulating protective autophagy, or it may be hijacked by the virus to enhance proinflammatory response. In this review, we will highlight current data illustrating the complexity and importance of HDAC6 in viral pathogenesis. We will summarize the structure and functional specificity of HDAC6, and its deacetylase- and ubiquitin-dependent activity in key cellular events in response to virus infection. We will also discuss how HDAC6 exerts its direct or indirect histone modification ability in viral lytic-latency switch.

Preclinical Mouse Models for Analysis of the Therapeutic Potential of Engineered Oncolytic Herpes Viruses

After more than two decades of research and development, oncolytic herpes viruses (oHSVs) are moving into the spotlight due to recent encouraging clinical trial data. oHSV and other oncolytic viruses function through direct oncolytic cancer cell-killing mechanisms and by stimulating antitumor immunity. As further viruses are developed and optimized for the treatment of various types of cancer, appropriate predictive preclinical models will be of great utility. This review will discuss existing data in this area, focusing on the mouse tumor models that are commonly used.