Immunotherapy with subcutaneous immunogenic autologous tumor lysate increases murine glioblastoma survival

Exploring dendritic cell subtypes in cancer immunotherapy: unraveling the role of mature regulatory dendritic cells

Dendritic cells (DCs) possess a specialized function in presenting antigens and play pivotal roles in both innate and adaptive immune responses. Their ability to cross-present antigens from tumor cells to naïve T cells is instrumental in generating specific T-cell-mediated antitumor responses, crucial for controlling tumor growth and preventing tumor cell dissemination. However, within a tumor immune microenvironment (TIME), the functions of DCs can be significantly compromised. This review focuses on the profile, function, and activation of DCs, leveraging recent studies that reveal insights into their phenotype acquisition, transcriptional state, and functional programs through single-cell RNA sequence (scRNA-seq) analysis. Additionally, the therapeutic potential of DC-mediated tumor antigen sensing in priming antitumor immunity is discussed.

rWTC-MBTA Vaccine Induces Potent Adaptive Immune Responses Against Glioblastomas via Dynamic Activation of Dendritic Cells

Despite strides in immunotherapy, glioblastoma multiforme (GBM) remains challenging due to low inherent immunogenicity and suppressive tumor microenvironment. Converting "cold" GBMs to "hot" is crucial for immune activation and improved outcomes. This study comprehensively characterized a therapeutic vaccination strategy for preclinical GBM models. The vaccine consists of Mannan-BAM-anchored irradiated whole tumor cells, Toll-like receptor ligands [lipoteichoic acid (LTA), polyinosinic-polycytidylic acid (Poly (I:C)), and resiquimod (R-848)], and anti-CD40 agonistic antibody (rWTC-MBTA). Intracranial GBM models (GL261, SB28 cells) are used to evaluate the vaccine efficacy. A substantial number of vaccinated mice exhibited complete regression of GBM tumors in a T-cell-dependent manner, with no significant toxicity. Long-term tumor-specific immune memory is confirmed upon tumor rechallenge. In the vaccine-draining lymph nodes of the SB28 model, rWTC-MBTA vaccination triggered a major rise in conventional dendritic cell type 1 (cDC1) 12 h post-treatment, followed by an increase in conventional dendritic cell type 2 (cDC2), monocyte-derived dendritic cell (moDC), and plasmacytoid dendritic cell (pDC) on Day 5 and Day 13. Enhanced cytotoxicity of CD4+ and CD8+ T cells in vaccinated mice is verified in co-culture with tumor cells. Analyses of immunosuppressive signals (T-cell exhaustion, myeloid-derived suppressor cells (MDSC), M2 macrophages) in the GBM microenvironment suggest potential combinations with other immunotherapies for enhanced efficacy. In conclusion, the authors findings demonstrate that rWTC-MBTA induces potent and long-term adaptive immune responses against GBM.

DC vaccines loaded with glioma cells killed by photodynamic therapy induce Th17 anti-tumor immunity and provide a four-gene signature for glioma prognosis

Gliomas, the most frequent type of primary tumor of the central nervous system in adults, results in significant morbidity and mortality. Despite the development of novel, complex, multidisciplinary, and targeted therapies, glioma therapy has not progressed much over the last decades. Therefore, there is an urgent need to develop novel patient-adjusted immunotherapies that actively stimulate antitumor T cells, generate long-term memory, and result in significant clinical benefits. This work aimed to investigate the efficacy and molecular mechanism of dendritic cell (DC) vaccines loaded with glioma cells undergoing immunogenic cell death (ICD) induced by photosens-based photodynamic therapy (PS-PDT) and to identify reliable prognostic gene signatures for predicting the overall survival of patients. Analysis of the transcriptional program of the ICD-based DC vaccine led to the identification of robust induction of Th17 signature when used as a vaccine. These DCs demonstrate retinoic acid receptor-related orphan receptor-γt dependent efficacy in an orthotopic mouse model. Moreover, comparative analysis of the transcriptome program of the ICD-based DC vaccine with transcriptome data from the TCGA-LGG dataset identified a four-gene signature (CFH, GALNT3, SMC4, VAV3) associated with overall survival of glioma patients. This model was validated on overall survival of CGGA-LGG, TCGA-GBM, and CGGA-GBM datasets to determine whether it has a similar prognostic value. To that end, the sensitivity and specificity of the prognostic model for predicting overall survival were evaluated by calculating the area under the curve of the time-dependent receiver operating characteristic curve. The values of area under the curve for TCGA-LGG, CGGA-LGG, TCGA-GBM, and CGGA-GBM for predicting five-year survival rates were, respectively, 0.75, 0.73, 0.9, and 0.69. These data open attractive prospects for improving glioma therapy by employing ICD and PS-PDT-based DC vaccines to induce Th17 immunity and to use this prognostic model to predict the overall survival of glioma patients.

Syngeneic murine glioblastoma models: reactionary immune changes and immunotherapy intervention outcomes

Glioblastoma is the most common primary malignant brain neoplasm with dismal 10-year survival rates of < 1%. Despite promising preliminary results from several novel therapeutic agents, clinical responses have been modest due to several factors, including tumor heterogeneity, immunosuppressive tumor microenvironment, and treatment resistance. Novel immunotherapeutics have been developed to reverse tumor-induced immunosuppression in patients with glioblastomas. In order to recapitulate the tumor microenvironment, reliable in vivo syngeneic murine models are critical for the development of new targeted agents as these models demonstrate rapid tumor induction and reliable tumor growth over multiple generations. Despite the clear advantages of murine models, choosing an appropriate model from an immunological perspective can be difficult and have significant ramifications on the translatability of the results from murine to human trials. Herein, the authors reviewed the 4 most commonly used immunocompetent syngeneic murine glioma models (GL261 [C57BL/6], SB28 [C57BL/6], CT-2A [C57BL/6], and SMA-560 [VM/Dk]) and compared their strengths and weaknesses from an immunological standpoint.

The Current Landscape of Immune Checkpoint Blockade in Glioblastoma

The glioblastoma tumor microenvironment is highly immunosuppressed. This immunosuppressive state is engineered by inhibitory molecules secreted by tumor cells that limit activation of immune effector cells, drive T-cell exhaustion, and enhance the immunosuppressive action of tumor-associated myeloid cells. Immunotherapeutic approaches have sought to combat glioblastoma microenvironment immunosuppression with agents such as immune checkpoint inhibitors. Although immune checkpoint blockade in glioblastoma has yielded disappointing results thus far, there is significant interest in the combination of immune checkpoint blockade with other approaches to enhance response.

Randomized Controlled Immunotherapy Clinical Trials for GBM Challenged

Simple Summary

Although multiple meta-analyses on active specific immunotherapy treatment for glioblastoma multiforme (GBM) have demonstrated a significant prolongation of overall survival, no single research group has succeeded in demonstrating the efficacy of this type of treatment in a prospective, double-blind, placebo-controlled, randomized clinical trial. In this paper, we explain how the complexity of the tumor biology and tumor–host interactions make proper stratification of a control group impossible. The individualized characteristics of advanced therapy medicinal products for immunotherapy contribute to heterogeneity within an experimental group. The dynamics of each tumor and in each patient aggravate comparative stable patient groups. Finally, combinations of immunotherapy strategies should be integrated with first-line treatment. We illustrate the complexity of a combined first-line treatment with individualized multimodal immunotherapy in a group of 70 adults with GBM and demonstrate that the integration of immunogenic cell death treatment within maintenance chemotherapy followed by dendritic cell vaccines and maintenance immunotherapy might provide a step towards improving the overall survival rate of GBM patients.

Abstract

Immunotherapies represent a promising strategy for glioblastoma multiforme (GBM) treatment. Different immunotherapies include the use of checkpoint inhibitors, adoptive cell therapies such as chimeric antigen receptor (CAR) T cells, and vaccines such as dendritic cell vaccines. Antibodies have also been used as toxin or radioactive particle delivery vehicles to eliminate target cells in the treatment of GBM. Oncolytic viral therapy and other immunogenic cell death-inducing treatments bridge the antitumor strategy with immunization and installation of immune control over the disease. These strategies should be included in the standard treatment protocol for GBM. Some immunotherapies are individualized in terms of the medicinal product, the immune target, and the immune tumor–host contact. Current individualized immunotherapy strategies focus on combinations of approaches. Standardization appears to be impossible in the face of complex controlled trial designs. To define appropriate control groups, stratification according to the Recursive Partitioning Analysis classification, MGMT promotor methylation, epigenetic GBM sub-typing, tumor microenvironment, systemic immune functioning before and after radiochemotherapy, and the need for/type of symptom-relieving drugs is required. Moreover, maintenance of a fixed treatment protocol for a dynamic, deadly cancer disease in a permanently changing tumor–host immune context might be inappropriate. This complexity is illustrated using our own data on individualized multimodal immunotherapies for GBM. Individualized medicines, including multimodal immunotherapies, are a rational and optimal yet also flexible approach to induce long-term tumor control. However, innovative methods are needed to assess the efficacy of complex individualized treatments and implement them more quickly into the general health system.

Proof of Concept Study: Mesoporous Silica Nanoparticles, From Synthesis to Active Specific Immunotherapy

Nanomaterials are increasingly valued tools in drug delivery research as they offer enhanced stability, controlled release and more effective drug encapsulation. Though yet to be introduced in clinical trial, mesoporous silica nanoparticles are promising delivery systems, due to their high chemical and mechanical stability while remaining biodegradable. This work provides proof of concept for particle based vaccines as cost-effective alternatives for dendritic cell immunotherapy. Synthesis and surface chemistry of the nanoparticles are optimized for protein conjugation and nanoparticles are characterized for their physicochemical properties and biodegradation. Ovalbumin is used as a model protein to load nanoparticles to produce a nanovaccine. The vaccine is tested in vitro on dendritic cultures to verify particle and vaccine uptake, toxicity, maturation effects and explicitly ovalbumin cross-presentation on MHC class I molecules. The optimized synthesis protocol renders reproducible mesoporous silica nanoparticles, resistant against agglomeration, within the required size range and have carboxylic surface functionalization necessary for protein conjugation. They are biodegradable over a time span of 1 week. This period is adjustable by changing synthesis parameters. UV sterilization of the particles does not induce quality loss, nor does it have toxic effects on cells. Treatment with mesoporous silica nanoparticles increases expression of MHC and costimulatory molecules of dendritic cells, indicating an adjuvant effect of nanoparticles on the adaptive immune system. Nanovaccine uptake and cross-presentation of ovalbumin are observed and the latter is increased when delivered by nanoparticles as compared to control conditions. This confirms the large potential of mesoporous silica nanoparticle based vaccines to replace dendritic-based active specific immunotherapy, offering a more standardized production process and higher efficacy.

Antigen-loaded monocyte administration induces potent therapeutic antitumor T cell responses

Efficacy of dendritic cell (DC) cancer vaccines is classically thought to depend on their antigen-presenting cell (APC) activity. Studies show, however, that DC vaccine priming of cytotoxic T lymphocytes (CTLs) requires the activity of endogenous DCs, suggesting that exogenous DCs stimulate antitumor immunity by transferring antigens (Ags) to endogenous DCs. Such Ag transfer functions are most commonly ascribed to monocytes, implying that undifferentiated monocytes would function equally well as a vaccine modality and need not be differentiated to DCs to be effective. Here, we used several murine cancer models to test the antitumor efficacy of undifferentiated monocytes loaded with protein or peptide Ag. Intravenously injected monocytes displayed antitumor activity superior to DC vaccines in several cancer models, including aggressive intracranial glioblastoma. Ag-loaded monocytes induced robust CTL responses via Ag transfer to splenic CD8+ DCs in a manner independent of monocyte APC activity. Ag transfer required cell-cell contact and the formation of connexin 43-containing gap junctions between monocytes and DCs. These findings demonstrate the existence of an efficient gap junction-mediated Ag transfer pathway between monocytes and CD8+ DCs and suggest that administration of tumor Ag-loaded undifferentiated monocytes may serve as a simple and efficacious immunotherapy for the treatment of human cancers.

Immune phenotyping of diverse syngeneic murine brain tumors identifies immunologically distinct types

Immunotherapy has emerged as a promising approach to treat cancer, however, its efficacy in highly malignant brain-tumors, glioblastomas (GBM), is limited. Here, we generate distinct imageable syngeneic mouse GBM-tumor models and utilize RNA-sequencing, CyTOF and correlative immunohistochemistry to assess immune-profiles in these models. We identify immunologically-inert and -active syngeneic-tumor types and show that inert tumors have an immune-suppressive phenotype with numerous exhausted CD8 T cells and resident macrophages; fewer eosinophils and SiglecF+ macrophages. To mimic the clinical-settings of first line of GBM-treatment, we show that tumor-resection invigorates an anti-tumor response via increasing T cells, activated microglia and SiglecF+ macrophages and decreasing resident macrophages. A comparative CyTOF analysis of resected-tumor samples from GBM-patients and mouse GBM-tumors show stark similarities in one of the mouse GBM-tumors tested. These findings guide informed choices for use of GBM models for immunotherapeutic interventions and offer a potential to facilitate immune-therapies in GBM patients.

Syngeneic mouse models for glioblastoma (GBM) cannot fully recapitulate clinical findings and response to therapy in patients. Here the authors perform a comprehensive immune profiling of different syngeneic GBM tumour models and compare it with the immune landscape of GBM patients to identify similarities and potential confounding differences.

Immunotherapy for gliomas: shedding light on progress in preclinical and clinical development

INTRODUCTION

Gliomas are infiltrating brain tumors associated with high morbidity and mortality. Current standard of care includes radiation, chemotherapy, and surgical resection. Today, survival rates for malignant glioma patients remain dismal and unchanged for decades. The glioma microenvironment is highly immunosuppressive and consequently this has motivated the development of immunotherapies for counteracting this condition, enabling the immune cells within the tumor microenvironment to react against this tumor.

AREAS COVERED

The authors discuss immunotherapeutic strategies for glioma in phase-I/II clinical trials and illuminate their mechanisms of action, limitations, and key challenges. They also examine promising approaches under preclinical development.

EXPERT OPINION

In the last decade there has been an expansion in immune-mediated anti-cancer therapies. In the glioma field, sophisticated strategies have been successfully implemented in preclinical models. Unfortunately, clinical trials have not yet yielded consistent results for glioma patients. This could be attributed to our limited understanding of the complex immune cell infiltration and its interaction with the tumor cells, the selected time for treatment, the combination with other therapies and the route of administration of the agent. Applying these modalities to treat malignant glioma is challenging, but many new alternatives are emerging to by-pass these hurdles.

Convection-enhanced delivery of liposomal drugs for effective treatment of glioblastoma multiforme

The blood-brain barrier (BBB) impedes the efficient delivery of systemically administered drugs to brain tumors, thus reducing the therapeutic efficacy. To overcome the limitations of intravascular delivery, convention-enhanced delivery (CED) was introduced to infuse drugs directly into the brain tumor using a catheter with a continuous positive pressure. However, tissue distribution and retention of the infused drugs are significantly hindered by microenvironmental factors of the tumor such as the extracellular matrix and lymphatic drainage system in the brain. Here, we leveraged a liposomal formulation to simultaneously improve tissue distribution and retention of drugs infused in the brain tumor via the CED method. Various liposomal formulations with different surface charge, PEGylation, and transition temperature (T_m) were prepared to test the cellular uptake in vitro, and the tissue distribution and retention in the brain. In in vitro studies, PEGylated liposomal formulations with a positive surface charge and high T_m showed the most efficient cellular uptake among the tested formulations. In in vivo studies, the liposomal formulations were infused directly into the brain via the CED method. PEGylated liposomal formulations with a positive surface charge and high T_m showed more efficient distribution and retention in both normal and tumor tissues while only-PEGylated formulations displayed rapid clearance from the tissues to cervical lymph nodes. Furthermore, we demonstrated that the CED of liposomal everolimus prepared with the PEGylated formulation with a positive surface charge and high T_m resulted in superior therapeutic effects for glioblastoma treatment compared to other formulations. Graphical abstract.

Convection-enhanced delivery of temozolomide and whole cell tumor immunizations in GL261 and KR158 experimental mouse gliomas

Background

Glioblastomas (GBM) are therapy-resistant tumors with a profoundly immunosuppressive tumor microenvironment. Chemotherapy has shown limited efficacy against GBM. Systemic delivery of chemotherapeutic drugs is hampered by the difficulty of achieving intratumoral levels as systemic toxicity is a dose-limiting factor. Although some of its effects might be mediated by immune reactivity, systemic chemotherapy can also inhibit induced or spontaneous antitumor immune reactivity. Convection-enhanced delivery of temozolomide (CED-TMZ) can tentatively increase intratumoral drug concentration while reducing systemic side effects. The objective of this study was to evaluate the therapeutic effect of intratumorally delivered temozolomide in combination with immunotherapy and whether such therapy can generate a cellular antitumor immune response.

Methods

Single bolus intratumoral injection and 3-day mini-osmotic pumps (Alzet®) were used to deliver intratumoral TMZ in C57BL6 mice bearing orthotopic gliomas. Immunotherapy consisted of subcutaneous injections of irradiated GL261 or KR158 glioma cells. Tumor size and intratumoral immune cell populations were analyzed by immunohistochemistry.

Results

Combined CED-TMZ and immunotherapy had a synergistic antitumor effect in the GL261 model, compared to CED-TMZ or immunotherapy as monotherapies. In the KR158 model, immunization cured a small proportion of the mice whereas addition of CED-TMZ did not have a synergistic effect. However, CED-TMZ as monotherapy prolonged the median survival. Moreover, TMZ bolus injection in the GL261 model induced neurotoxicity and lower cure rate than its equivalent dose delivered by CED. In addition, we found that T-cells were the predominant cells responsible for the TMZ antitumor effect in the GL261 model. Finally, CED-TMZ combined with immunotherapy significantly reduced tumor volume and increased the intratumoral influx of T-cells in both models.

Conclusions

We show that immunotherapy synergized with CED-TMZ in the GL261 model and cured animals in the KR158 model. Single bolus administration of TMZ was effective with a narrower therapeutic window than CED-TMZ. Combined CED-TMZ and immunotherapy led to an increase in the intratumoral influx of T-cells. These results form part of the basis for the translation of the therapy to patients with GBM but the dosing and timing of delivery will have to be explored in depth both experimentally and clinically.

PKHB1 Tumor Cell Lysate Induces Antitumor Immune System Stimulation and Tumor Regression in Syngeneic Mice with Tumoral T Lymphoblasts

Acute lymphocytic leukemia (ALL) is the most common pediatric cancer. Currently, treatment options for patients with relapsed and refractory ALL mostly rely on immunotherapies. However, hematological cancers are commonly associated with a low immunogenicity and immune tolerance, which may contribute to leukemia relapse and the difficulties associated with the development of effective immunotherapies against this disease. We recently demonstrated that PKHB1, a TSP1-derived CD47 agonist peptide, induces immunogenic cell death (ICD) in T cell ALL (T-ALL). Cell death induced by PKHB1 on T-ALL cell lines and their homologous murine, L5178Y-R (T-murine tumor lymphoblast cell line), induced damage-associated molecular patterns (DAMPs) exposure and release. Additionally, a prophylactic vaccination with PKHB1-treated L5178Y-R cells prevented tumor establishment in vivo in all the cases. Due to the immunogenic potential of PKHB1-treated cells, in this study we assessed their ability to induce antitumor immune responses ex vivo and in vivo in an established tumor. We first confirmed the selectivity of cell death induced by PKBH1 in tumor L5178Y-R cells and observed that calreticulin exposure increased when cell death increased. Then, we found that the tumor cell lysate (TCL) obtained from PKHB1-treated L5178YR tumor cells (PKHB1-TCL) was able to induce, ex vivo, dendritic cells maturation, cytokine production, and T cell antitumor responses. Finally, our results show that in vivo, PKHB1-TCL treatment induces tumor regression in syngeneic mice transplanted with L5178Y-R cells, increasing their overall survival and protecting them from further tumor establishment after tumor rechallenge. Altogether our results highlight the immunogenicity of the cell death induced by PKHB1 activation of CD47 as a potential therapeutic tool to overcome the low immunogenicity and immune tolerance in T-ALL.

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

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

Promising vaccines for treating glioblastoma

INTRODUCTION

Conventional therapies for glioblastoma  (GBM) typically fail to provide lasting antitumor benefits, owing to their inability to specifically eliminate all malignant cells. Cancer vaccines are currently being evaluated as a means to direct the adaptive immune system to target residual GBM cells that remain following standard-of-care treatment.

AREAS COVERED

In this review, we provide an overview of the more noteworthy cancer vaccines that are under investigation for the treatment of GBM, as well as potential future directions that may enhance GBM-vaccine effectiveness.

EXPERT OPINION

To date, no cancer vaccines have been proven effective against GBM; however, only a few have reached phase III clinical testing. Clinical immunological monitoring data suggest that GBM vaccines are capable of stimulating immune responses reactive to GBM antigens, but whether these responses have an appreciable antitumor effect on GBM is still uncertain. Nevertheless, there have been several promising outcomes in early phase clinical trials, which lend encouragement to this area of study. Further studies with GBM vaccines are, therefore, warranted.