Systemically administered AAV9-sTRAIL combats invasive glioblastoma in a patient-derived orthotopic xenograft model

Progress of nanoparticle drug delivery system for the treatment of glioma

Gliomas are typical malignant brain tumours affecting a wide population worldwide. Operation, as the common treatment for gliomas, is always accompanied by postoperative drug chemotherapy, but cannot cure patients. The main challenges are chemotherapeutic drugs have low blood-brain barrier passage rate and a lot of serious adverse effects, meanwhile, they have difficulty targeting glioma issues. Nowadays, the emergence of nanoparticles (NPs) drug delivery systems (NDDS) has provided a new promising approach for the treatment of gliomas owing to their excellent biodegradability, high stability, good biocompatibility, low toxicity, and minimal adverse effects. Herein, we reviewed the types and delivery mechanisms of NPs currently used in gliomas, including passive and active brain targeting drug delivery. In particular, we primarily focused on various hopeful types of NPs (such as liposome, chitosan, ferritin, graphene oxide, silica nanoparticle, nanogel, neutrophil, and adeno-associated virus), and discussed their advantages, disadvantages, and progress in preclinical trials. Moreover, we outlined the clinical trials of NPs applied in gliomas. According to this review, we provide an outlook of the prospects of NDDS for treating gliomas and summarise some methods that can enhance the targeting specificity and safety of NPs, like surface modification and conjugating ligands and peptides. Although there are still some limitations of these NPs, NDDS will offer the potential for curing glioma patients.

Applications of tissue-specific and cancer-selective gene promoters for cancer diagnosis and therapy

Current treatment of solid tumors with standard of care chemotherapies, radiation therapy and/or immunotherapies are often limited by severe adverse toxic effects, resulting in a narrow therapeutic index. Cancer gene therapy represents a targeted approach that in principle could significantly reduce undesirable side effects in normal tissues while significantly inhibiting tumor growth and progression. To be effective, this strategy requires a clear understanding of the molecular biology of cancer development and evolution and developing biological vectors that can serve as vehicles to target cancer cells. The advent and fine tuning of omics technologies that permit the collective and spatial recognition of genes (genomics), mRNAs (transcriptomics), proteins (proteomics), metabolites (metabolomics), epiomics (epigenomics, epitranscriptomics, and epiproteomics), and their interactomics in defined complex biological samples provide a roadmap for identifying crucial targets of relevance to the cancer paradigm. Combining these strategies with identified genetic elements that control target gene expression uncovers significant opportunities for developing guided gene-based therapeutics for cancer. The purpose of this review is to overview the current state and potential limitations in developing gene promoter-directed targeted expression of key genes and highlights their potential applications in cancer gene therapy.

Systems Biology Approaches for the Improvement of Oncolytic Virus-Based Immunotherapies

Oncolytic virus (OV)-based immunotherapy is mainly dependent on establishing an efficient cell-mediated antitumor immunity. OV-mediated antitumor immunity elicits a renewed antitumor reactivity, stimulating a T-cell response against tumor-associated antigens (TAAs) and recruiting natural killer cells within the tumor microenvironment (TME). Despite the fact that OVs are unspecific cancer vaccine platforms, to further enhance antitumor immunity, it is crucial to identify the potentially immunogenic T-cell restricted TAAs, the main key orchestrators in evoking a specific and durable cytotoxic T-cell response. Today, innovative approaches derived from systems biology are exploited to improve target discovery in several types of cancer and to identify the MHC-I and II restricted peptide repertoire recognized by T-cells. Using specific computation pipelines, it is possible to select the best tumor peptide candidates that can be efficiently vectorized and delivered by numerous OV-based platforms, in order to reinforce anticancer immune responses. Beyond the identification of TAAs, system biology can also support the engineering of OVs with improved oncotropism to reduce toxicity and maintain a sufficient portion of the wild-type virus virulence. Finally, these technologies can also pave the way towards a more rational design of armed OVs where a transgene of interest can be delivered to TME to develop an intratumoral gene therapy to enhance specific immune stimuli.

Novel Nano-Drug Delivery System for Brain Tumor Treatment

As the most dangerous tumors, brain tumors are usually treated with surgical removal, radiation therapy, and chemotherapy. However, due to the aggressive growth of gliomas and their resistance to conventional chemoradiotherapy, it is difficult to cure brain tumors by conventional means. In addition, the higher dose requirement of chemotherapeutic drugs caused by the blood-brain barrier (BBB) and the untargeted nature of the drug inevitably leads to low efficacy and systemic toxicity of chemotherapy. In recent years, nanodrug carriers have attracted extensive attention because of their superior drug transport capacity and easy-to-control properties. This review systematically summarizes the major strategies of novel nano-drug delivery systems for the treatment of brain tumors in recent years that cross the BBB and enhance brain targeting, and compares the advantages and disadvantages of several strategies.

Adding recombinant AAVs to the cancer therapeutics mix

Gene therapy is a powerful biological tool that is reshaping therapeutic landscapes for several diseases. Researchers are using both non-viral and viral-based gene therapy methods with success in the lab and the clinic. In the cancer biology field, gene therapies are expanding treatment options and the possibility of favorable outcomes for patients. While cellular immunotherapies and oncolytic virotherapies have paved the way in cancer treatments based on genetic engineering, recombinant adeno-associated virus (rAAV), a viral-based module, is also emerging as a potential cancer therapeutic through its malleability, specificity, and broad application to common as well as rare tumor types, tumor microenvironments, and metastatic disease. A wide range of AAV serotypes, promoters, and transgenes have been successful at reducing tumor growth and burden in preclinical studies, suggesting more groundbreaking advances using rAAVs in cancer are on the horizon.

Comparative study of neuron-specific promoters in mouse brain transduced by intravenously administered AAV-PHP.eB

Adeno-associated virus (AAV)- PHP.B and AAV-PHP.eB (PHP.eB), a capsid variant of AAV serotype 9, efficiently penetrates the mouse blood-brain barrier and predominantly infects neurons. Thus, the PHP.B / PHP.eB capsid and a neuron-specific promoter is a reasonable combination for effective neuronal transduction. However, the transduction characteristics of intravenously administered PHP.B / PHP.eB carrying different neuron-specific promoters have not been studied systematically. In this study, using an intravenous infusion of PHP.eB in mice, we performed a comparative study of the ubiquitous CBh and three neuron-specific promoters, the Ca²⁺/calmodulin-dependent kinase subunit α (CaMKII) promoter, neuron-specific enolase (NSE) promoter, and synapsin I with a minimal CMV sequence (SynI-minCMV) promoter. Expression levels of a transgene by three neuron-specific promoters were comparable to or higher than those of the CBh promoter. Among the promoters examined, the NSE promoter showed the highest transgene expression. All neuron-specific promoters were activated specifically in the neurons. PHP.eB carrying the CaMKII promoter, which is generally believed to exert its function exclusively in the excitatory neurons, transduced both the excitatory and inhibitory neurons without bias, whereas PHP.eB with the NSE and SynI-minCMV promoters transduced neurons with significant bias toward inhibitory neurons. These results are useful in neuron-targeted broad transgene expression through systemic infusion of blood-brain-barrier-penetrating AAV vectors carrying the neuron-specific promoter.

Apoptosis-Inducing TNF Superfamily Ligands for Cancer Therapy

Cancer is a complex disease with apoptosis evasion as one of its hallmarks; therefore, apoptosis induction in transformed cells seems a promising approach as a cancer treatment. TNF apoptosis-inducing ligands, which are naturally present in the body and possess tumoricidal activity, are attractive candidates. The most studied proteins are TNF-α, FasL, and TNF-related apoptosis-inducing ligand (TRAIL). Over the years, different recombinant TNF family-derived apoptosis-inducing ligands and agonists have been designed. Their stability, specificity, and half-life have been improved because most of the TNF ligands have the disadvantages of having a short half-life and affinity to more than one receptor. Here, we review the outlook on apoptosis-inducing ligands as cancer treatments in diverse preclinical and clinical stages and summarize strategies of overcoming their natural limitations to improve their effectiveness.

Synthetic and systems biology principles in the design of programmable oncolytic virus immunotherapies for glioblastoma

Oncolytic viruses (OVs) are a class of immunotherapeutic agents with promising preclinical results for the treatment of glioblastoma (GBM) but have shown limited success in recent clinical trials. Advanced bioengineering principles from disciplines such as synthetic and systems biology are needed to overcome the current challenges faced in developing effective OV-based immunotherapies for GBMs, including off-target effects and poor clinical responses. Synthetic biology is an emerging field that focuses on the development of synthetic DNA constructs that encode networks of genes and proteins (synthetic genetic circuits) to perform novel functions, whereas systems biology is an analytical framework that enables the study of complex interactions between host pathways and these synthetic genetic circuits. In this review, the authors summarize synthetic and systems biology concepts for developing programmable, logic-based OVs to treat GBMs. Programmable OVs can increase selectivity for tumor cells and enhance the local immunological response using synthetic genetic circuits. The authors discuss key principles for developing programmable OV-based immunotherapies, including how to 1) select an appropriate chassis, a vector that carries a synthetic genetic circuit, and 2) design a synthetic genetic circuit that can be programmed to sense key signals in the GBM microenvironment and trigger release of a therapeutic payload. To illustrate these principles, some original laboratory data are included, highlighting the need for systems biology studies, as well as some preliminary network analyses in preparation for synthetic biology applications. Examples from the literature of state-of-the-art synthetic genetic circuits that can be packaged into leading candidate OV chassis are also surveyed and discussed.

Challenges in adeno-associated virus-based treatment of central nervous system diseases through systemic injection

Adeno-associated virus (AAV) vector, an excellent gene therapy vector, has been widely used in the treatment of various central nervous system (CNS) diseases. Due to the presence of the blood-brain barrier (BBB), early attempts at AAV-based CNS diseases treatment were mainly performed through intracranial injections. Subsequently, systemic injections of AAV9, the first AAV that was shown to have BBB-crossing ability in newborn and adult mice, were assessed in clinical trials for multiple CNS diseases. However, the development of systemic AAV injections to treat CNS diseases is still associated with many challenges, such as the efficiency of AAV in crossing the BBB, the peripheral toxicity caused by the expression of AAV-delivered genes, and the immune barrier against AAV in the blood. In this review, we will introduce the biology of the AAV vector and the advantages of systemic AAV injections to treat CNS diseases. Most importantly, we will introduce the challenges associated with systemic injection of therapeutic AAV in treating CNS diseases and suggest feasible solutions.

Adeno-associated virus (AAV)-based gene therapy for glioblastoma

Glioblastoma (GBM) is the most common and malignant Grade IV primary craniocerebral tumor caused by glial cell carcinogenesis with an extremely poor median survival of 12–18 months. The current standard treatments for GBM, including surgical resection followed by chemotherapy and radiotherapy, fail to substantially prolong survival outcomes. Adeno-associated virus (AAV)-mediated gene therapy has recently attracted considerable interest because of its relatively low cytotoxicity, poor immunogenicity, broad tissue tropism, and long-term stable transgene expression. Furthermore, a range of gene therapy trials using AAV as vehicles are being investigated to thwart deadly GBM in mice models. At present, AAV is delivered to the brain by local injection, intracerebroventricular (ICV) injection, or systematic injection to treat experimental GBM mice model. In this review, we summarized the experimental trials of AAV-based gene therapy as GBM treatment and compared the advantages and disadvantages of different AAV injection approaches. We systematically introduced the prospect of the systematic injection of AAV as an approach for AAV-based gene therapy for GBM.

Current Opinion on Molecular Characterization for GBM Classification in Guiding Clinical Diagnosis, Prognosis, and Therapy

Glioblastoma (GBM) is highly invasive and the deadliest brain tumor in adults. It is characterized by inter-tumor and intra-tumor heterogeneity, short patient survival, and lack of effective treatment. Prognosis and therapy selection is driven by molecular data from gene transcription, genetic alterations and DNA methylation. The four GBM molecular subtypes are proneural, neural, classical, and mesenchymal. More effective personalized therapy heavily depends on higher resolution molecular subtype signatures, combined with gene therapy, immunotherapy and organoid technology. In this review, we summarize the principal GBM molecular classifications that guide diagnosis, prognosis, and therapeutic recommendations.

Towards Clinical Implementation of Adeno-Associated Virus (AAV) Vectors for Cancer Gene Therapy: Current Status and Future Perspectives

Adeno-associated virus (AAV) vectors have gained tremendous attention as in vivo delivery systems in gene therapy for inherited monogenetic diseases. First market approvals, excellent safety data, availability of large-scale production protocols, and the possibility to tailor the vector towards optimized and cell-type specific gene transfer offers to move from (ultra) rare to common diseases. Cancer, a major health burden for which novel therapeutic options are urgently needed, represents such a target. We here provide an up-to-date overview of the strategies which are currently developed for the use of AAV vectors in cancer gene therapy and discuss the perspectives for the future translation of these pre-clinical approaches into the clinic.

Viral Vector-Based Melanoma Gene Therapy

Gene therapy applications of oncolytic viruses represent an attractive alternative for cancer treatment. A broad range of oncolytic viruses, including adenoviruses, adeno-associated viruses, alphaviruses, herpes simplex viruses, retroviruses, lentiviruses, rhabdoviruses, reoviruses, measles virus, Newcastle disease virus, picornaviruses and poxviruses, have been used in diverse preclinical and clinical studies for the treatment of various diseases, including colon, head-and-neck, prostate and breast cancer as well as squamous cell carcinoma and glioma. The majority of studies have focused on immunotherapy and several drugs based on viral vectors have been approved. However, gene therapy for malignant melanoma based on viral vectors has not been utilized to its full potential yet. This review represents a summary of the achievements of preclinical and clinical studies using viral vectors, with the focus on malignant melanoma.

Synergistic Effects of Bortezomib-OV Therapy and Anti-Invasive Strategies in Glioblastoma: A Mathematical Model

It is well-known that the tumor microenvironment (TME) plays an important role in the regulation of tumor growth and the efficacy of anti-tumor therapies. Recent studies have demonstrated the potential of combination therapies, using oncolytic viruses (OVs) in conjunction with proteosome inhibitors for the treatment of glioblastoma, but the role of the TME in such therapies has not been studied. In this paper, we develop a mathematical model for combination therapies based on the proteosome inhibitor bortezomib and the oncolytic herpes simplex virus (oHSV), with the goal of understanding their roles in bortezomib-induced endoplasmic reticulum (ER) stress, and how the balance between apoptosis and necroptosis is affected by the treatment protocol. We show that the TME plays a significant role in anti-tumor efficacy in OV combination therapy, and illustrate the effect of different spatial patterns of OV injection. The results illustrate a possible phenotypic switch within tumor populations in a given microenvironment, and suggest new anti-invasion therapies.

Efficient Gene Transfer to the Central Nervous System by Single-Stranded Anc80L65

Adeno-associated viral vectors (AAVs) have demonstrated potential in applications for neurologic disorders, and the discovery that some AAVs can cross the blood-brain barrier (BBB) after intravenous injection has further expanded these opportunities for non-invasive brain delivery. Anc80L65, a novel AAV capsid designed from in silico reconstruction of the viral evolutionary lineage, has previously demonstrated robust transduction capabilities after local delivery in various tissues such as liver, retina, or cochlea, compared with conventional AAVs. Here, we compared the transduction efficacy of Anc80L65 with conventional AAV9 in the CNS after intravenous, intracerebroventricular (i.c.v.), or intraparenchymal injections. Anc80L65 was more potent at targeting the brain and spinal cord after intravenous injection than AAV9, and mostly transduced astrocytes and a wide range of neuronal subpopulations. Although the efficacy of Anc80L65 and AAV9 is similar after direct intraparenchymal injection in the striatum, Anc80L65's diffusion throughout the CNS was more extensive than AAV9 after i.c.v. infusion, leading to widespread EGFP expression in the cerebellum. These findings demonstrate that Anc80L65 is a highly efficient gene transfer vector for the murine CNS. Systemic injection of Anc80L65 leads to notable expression in the CNS that does not rely on a self-complementary genome. These data warrant further testing in larger animal models.

New frontiers in oncolytic viruses: optimizing and selecting for virus strains with improved efficacy

Oncolytic viruses have demonstrated selective replication and killing of tumor cells. Different types of oncolytic viruses – adenoviruses, alphaviruses, herpes simplex viruses, Newcastle disease viruses, rhabdoviruses, Coxsackie viruses, and vaccinia viruses – have been applied as either naturally occurring or engineered vectors. Numerous studies in animal-tumor models have demonstrated substantial tumor regression and prolonged survival rates. Moreover, clinical trials have confirmed good safety profiles and therapeutic efficacy for oncolytic viruses. Most encouragingly, the first cancer gene-therapy drug – Gendicine, based on oncolytic adenovirus type 5 – was approved in China. Likewise, a second-generation oncolytic herpes simplex virus-based drug for the treatment of melanoma has been registered in the US and Europe as talimogene laherparepvec.

Safety and Efficacy of AAV Retrograde Pancreatic Ductal Gene Delivery in Normal and Pancreatic Cancer Mice

Recombinant adeno-associated virus (rAAV)-mediated gene delivery shows promise to transduce the pancreas, but safety/efficacy in a neoplastic context is not well established. To identify an ideal AAV serotype, route, and vector dose and assess safety, we have investigated the use of three AAV serotypes (6, 8, and 9) expressing GFP in a self-complementary (sc) AAV vector under an EF1α promoter (scAAV.GFP) following systemic or retrograde pancreatic intraductal delivery. Systemic delivery of scAAV9.GFP transduced the pancreas with high efficiency, but gene expression did not exceed >45% with the highest dose, 5 × 10¹² viral genomes (vg). Intraductal delivery of 1 × 10¹¹ vg scAAV6.GFP transduced acini, ductal cells, and islet cells with >50%, ∼48%, and >80% efficiency, respectively, and >80% pancreatic transduction was achieved with 5 × 10¹¹ vg. In a Kras^G12D-driven pancreatic cancer mouse model, intraductal delivery of scAAV6.GFP targeted acini, epithelial, and stromal cells and exhibited persistent gene expression 5 months post-delivery. In normal mice, intraductal delivery induced a transient increase in serum amylase/lipase that resolved within a day of infusion with no sustained pancreatic inflammation or fibrosis. Similarly, in PDAC mice, intraductal delivery did not increase pancreatic intraepithelial neoplasia progression/fibrosis. Our study demonstrates that scAAV6 targets the pancreas/neoplasm efficiently and safely via retrograde pancreatic intraductal delivery.

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.