An effective therapeutic regime for treatment of glioma using oncolytic vaccinia virus expressing IL-21 in combination with immune checkpoint inhibition

An oncolytic HSV-1 vector induces a therapeutic adaptive immune response against glioblastoma

BACKGROUND

Glioblastoma (GBM) is the most frequent and aggressive brain tumor in adults with the lowest survival rates five years post-diagnosis. Oncolytic viruses (OVs) selectively target and damage cancer cells, and for this reason they are being investigated as new therapeutic tools also against GBM.

METHODS

An oncolytic herpes simplex virus type 1 (oHSV-1) with deletions in the γ34.5 neurovirulence gene and the US12 gene, expressing enhanced green fluorescent protein (EGFP-oHSV-1) as reporter gene was generated and tested for its capacity to infect and kill the murine GL261 glioblastoma (GBM) cell line. Syngeneic mice were orthotopically injected with GL261cells. Seven days post-implantation, EGFP-oHSV-1 was administered intratumorally. Twenty-one days after parental tumor challenge in the opposite brain hemisphere, mice were sacrified and their brains were analysed by immunohistochemistry to assess tumor presence and cell infiltrate.

RESULTS

oHSV-1 replicates and induces cell death of GL261 cells in vitro. A single intracranial injection of EGFP-oHSV-1 in established GL261 tumors significantly prolongs survival in all treated mice compared to placebo treatment. Notably, 45% of treated mice became long-term survivors, and rejected GL261 cells upon rechallenge in the contralateral brain hemisphere, indicating an anamnestic antitumoral immune response. Post-mortem analysis revealed a profound modification of the tumor microenvironment with increased infiltration of CD4 + and CD8 + T lymphocytes, intertumoral vascular collapse and activation and redistribution of macrophage, microglia, and astroglia in the tumor area, with the formation of intense fibrotic tissue suggestive of complete rejection in long-term survivor mice.

CONCLUSIONS

EGFP-oHSV1 demonstrates potent antitumoral activity in an immunocompetent GBM model as a monotherapy, resulting from direct cell killing combined with the stimulation of a protective adaptive immune response. These results open the way to possible application of our strategy in clinical setting.

Mesenchymal stem cells as therapeutic vehicles for glioma

Glioma is a disease with a poor prognosis despite the availability of multimodality treatments, and the development of novel therapies is urgently needed. Challenges in glioma treatment include the difficulty for drugs to cross the blood-brain barrier when administered systemically and poor drug diffusion when administered locally. Mesenchymal stem cells exhibit advantages for glioma therapy because of their ability to pass through the blood-brain barrier and migrate to tumor cells and their tolerance to the immune system. Therefore, mesenchymal stem cells have been explored as vehicles for various therapeutic agents for glioma treatment. Mesenchymal stem cells loaded with chemotherapeutic drugs show improved penetration and tumor accumulation. For gene therapy, mesenchymal stem cells can be used as vehicles for suicide genes, the so-called gene-directed enzyme prodrug therapy. Mesenchymal stem cell-based oncolytic viral therapies have been attempted in recent years to enhance the efficacy of infection against the tumor, viral replication, and distribution of viral particles. Many uncertainties remain regarding the function and behavior of mesenchymal stem cells in gliomas. However, strategies to increase mesenchymal stem cell migration to gliomas may improve the delivery of therapeutic agents and enhance their anti-tumor effects, representing promising potential for patient treatment.

Therapeutic potential of interleukin-21 in cancer

Interleukin-21 (IL-21) is an immunostimulatory cytokine which belongs to the common gamma-chain family of cytokines. It plays an import role in the development, differentiation, proliferation, and activation of immune cells, in particular T and natural killer (NK) cells. Since its discovery in 2000, IL-21 has been shown to regulate both adaptive and immune responses associates with key role in antiviral and antitumor responses. Recent advances indicate IL-21 as a promising target for cancer treatment and encouraging results were obtained in preclinical studies which investigated the potency of IL-21 alone or in combination with other therapies, including monoclonal antibodies, checkpoint inhibitory molecules, oncolytic virotherapy, and adoptive cell transfer. Furthermore, IL-21 showed antitumor effects in the treatment of patients with advanced cancer, with minimal side effects in several clinical trials. In the present review, we will outline the recent progress in IL-21 research, highlighting the potential of IL-21 based therapy as single agent or in combination with other drugs to enhance cancer treatment efficiency.

Interleukin-21 as an adjuvant in cancer immunotherapy: Current advances and future directions

Immunotherapy has revolutionized cancer treatment. However, it's well-recognized that a considerable proportion of patients fail to benefit from immunotherapy, and to improve immunotherapy response is clinically urgent. Insufficient immune infiltration and immunosuppressive tumor microenvironments (TME) are main contributors to immunotherapy resistance. Thus sustaining functional self-renewal capacity for immune cells and subverting immune-suppressive signals are potential strategies for boosting the efficacy of immunotherapy. Interleukin-21 (IL-21), a crucial cytokine, which could enhance cytotoxic function of immune cells and reduces immunosuppressive cells enrichment in TME, shows promising orientations as an immunoadjuvant in tumor immunotherapy. This review focuses on IL-21 in cancer treatment, including function and mechanisms of IL-21, preclinical and clinical studies, and future directions for IL-21-assisted therapies.

Combination of Oncolytic Virotherapy with Different Antitumor Approaches against Glioblastoma

Glioblastoma is one of the most malignant and aggressive tumors of the central nervous system. Despite the standard therapy consisting of maximal surgical resection and chemo- and radiotherapy, the median survival of patients with this diagnosis is about 15 months. Oncolytic virus therapy is one of the promising areas for the treatment of malignant neoplasms. In this review, we have focused on emphasizing recent achievements in virotherapy, both as a monotherapy and in combination with other therapeutic schemes to improve survival rate and quality of life among patients with glioblastoma.

Oncolytic vaccinia virus and cancer immunotherapy

Oncolytic virotherapy (OVT) is a promising form of cancer treatment that uses genetically engineered viruses to replicate within cancer cells and trigger anti-tumor immune response. In addition to killing cancer cells, oncolytic viruses can also remodel the tumor microenvironment and stimulate a long-term anti-tumor immune response. Despite achieving positive results in cellular and organismal studies, there are currently only a few approved oncolytic viruses for clinical use. Vaccinia virus (VACV) has emerged as a potential candidate due to its ability to infect a wide range of cancer cells. This review discusses the mechanisms, benefits, and clinical trials of oncolytic VACVs. The safety and efficacy of different viral backbones are explored, as well as the effects of oncolytic VACVs on the tumor microenvironment. The potential combination of oncolytic VACVs with immunotherapy or traditional therapies is also highlighted. The review concludes by addressing prospects and challenges in the field of oncolytic VACVs, with the aim of promoting further research and application in cancer therapy.

Improving the therapeutic efficacy of oncolytic viruses for cancer: targeting macrophages

Oncolytic viruses (OVs) for cancer treatment are in a rapid stage of development, and the direct tumor lysis and activation of a comprehensive host immune response are irreplaceable advantages of cancer immunotherapy. However, excessive antiviral immune responses also restrict the spread of OVs in vivo and the infection of tumor cells. Macrophages are functionally diverse innate immune cells that phagocytose tumor cells and present antigens to activate the immune response, while also limiting the delivery of OVs to tumors. Studies have shown that the functional propensity of macrophages between OVs and tumor cells affects the overall therapeutic effect of oncolytic virotherapy. How to effectively avoid the restrictive effect of macrophages on OVs and reshape the function of tumor-associated macrophages in oncolytic virotherapy is an important challenge we are now facing. Here, we review and summarize the complex dual role of macrophages in oncolytic virotherapy, highlighting how the functional characteristics of macrophage plasticity can be utilized to cooperate with OVs to enhance anti-tumor effects, as well as highlighting the importance of designing and optimizing delivery modalities for OVs in the future.

Interleukin-21 Influences Glioblastoma Course: Biological Mechanisms and Therapeutic Potential

Brain tumors represent a heterogeneous group of neoplasms involving the brain or nearby tissues, affecting populations of all ages with a high incidence worldwide. Among the primary brain tumors, the most aggressive and also the most common is glioblastoma (GB), a type of glioma that falls into the category of IV-grade astrocytoma. GB often leads to death within a few months after diagnosis, even if the patient is treated with available therapies; for this reason, it is important to continue to discover new therapeutic approaches to allow for a better survival rate of these patients. Immunotherapy, today, seems to be one of the most innovative types of treatment, based on the ability of the immune system to counteract various pathologies, including cancer. In this context, interleukin 21 (IL-21), a type I cytokine produced by natural killer (NK) cells and CD4+ T lymphocytes, appears to be a valid target for new therapies since this cytokine is involved in the activation of innate and adaptive immunity. To match this purpose, our review deeply evaluated how IL-21 could influence the progression of GB, analyzing its main biological processes and mechanisms while evaluating the potential use of the latest available therapies.

Recombinant Strains of Oncolytic Vaccinia Virus for Cancer Immunotherapy

Cancer virotherapy is an alternative therapeutic approach based on the viruses that selectively infect and kill tumor cells. Vaccinia virus (VV) is a member of the Poxviridae, a family of enveloped viruses with a large linear double-stranded DNA genome. The proven safety of the VV strains as well as considerable transgene capacity of the viral genome, make VV an excellent platform for creating recombinant oncolytic viruses for cancer therapy. Furthermore, various genetic modifications can increase tumor selectivity and therapeutic efficacy of VV by arming it with the immune-modulatory genes or proapoptotic molecules, boosting the host immune system, and increasing cross-priming recognition of the tumor cells by T-cells or NK cells. In this review, we summarized the data on bioengineering approaches to develop recombinant VV strains for enhanced cancer immunotherapy.

Correlative analysis from a phase I clinical trial of intrapleural administration of oncolytic vaccinia virus (Olvi-vec) in patients with malignant pleural mesothelioma

Background

The attenuated, genetically engineered vaccinia virus has been shown to be a promising oncolytic virus for the treatment of patients with solid tumors, through both direct cytotoxic and immune-activating effects. Whereas systemically administered oncolytic viruses can be neutralized by pre-existing antibodies, locoregionally administered viruses can infect tumor cells and generate immune responses. We conducted a phase I clinical trial to investigate the safety, feasibility and immune activating effects of intrapleural administration of oncolytic vaccinia virus (NCT01766739).

Methods

Eighteen patients with malignant pleural effusion due to either malignant pleural mesothelioma or metastatic disease (non-small cell lung cancer or breast cancer) underwent intrapleural administration of the oncolytic vaccinia virus using a dose-escalating method, following drainage of malignant pleural effusion. The primary objective of this trial was to determine a recommended dose of attenuated vaccinia virus. The secondary objectives were to assess feasibility, safety and tolerability; evaluate viral presence in the tumor and serum as well as viral shedding in pleural fluid, sputum, and urine; and evaluate anti-vaccinia virus immune response. Correlative analyses were performed on body fluids, peripheral blood, and tumor specimens obtained from pre- and post-treatment timepoints.

Results

Treatment with attenuated vaccinia virus at the dose of 1.00E+07 plaque-forming units (PFU) to 6.00E+09 PFU was feasible and safe, with no treatment-associated mortalities or dose-limiting toxicities. Vaccinia virus was detectable in tumor cells 2-5 days post-treatment, and treatment was associated with a decrease in tumor cell density and an increase in immune cell density as assessed by a pathologist blinded to the clinical observations. An increase in both effector (CD8+, NK, cytotoxic cells) and suppressor (Tregs) immune cell populations was observed following treatment. Dendritic cell and neutrophil populations were also increased, and immune effector and immune checkpoint proteins (granzyme B, perforin, PD-1, PD-L1, and PD-L2) and cytokines (IFN-γ, TNF-α, TGFβ1 and RANTES) were upregulated.

Conclusion

The intrapleural administration of oncolytic vaccinia viral therapy is safe and feasible and generates regional immune response without overt systemic symptoms.

Clinical trial registration

https://clinicaltrials.gov/ct2/show/NCT01766739, identifier NCT01766739.

Oncolytic Adenovirus, a New Treatment Strategy for Prostate Cancer

Prostate cancer is the most common cancer and one of the leading causes of cancer mortality in males. Androgen-deprivation therapy (ADT) is an effective strategy to inhibit tumour growth at early stages. However, 10~50% of cases are estimated to progress to metastatic castration-resistant prostate cancer (mCRPC) which currently lacks effective treatments. Clinically, salvage treatment measures, such as endocrine therapy and chemotherapy, are mostly used for advanced prostate cancer, but their clinical outcomes are not ideal. When the existing clinical therapeutic methods can no longer inhibit the development of advanced prostate cancer, human adenovirus (HAdV)-based gene therapy and viral therapy present promising effects. Pre-clinical studies have shown its powerful oncolytic effect, and clinical studies are ongoing to further verify its effect and safety in prostate cancer treatment. Targeting the prostate by HAdV alone or in combination with radiotherapy and chemotherapy sheds light on patients with castration-resistant and advanced prostate cancer. This review summarizes the advantages of oncolytic virus-mediated cancer therapy, strategies of HAdV modification, and existing preclinical and clinical investigations of HAdV-mediated gene therapy to further evaluate the potential of oncolytic adenovirus in prostate cancer treatment.

Transcriptome Analysis of Human Glioblastoma Cells Susceptible to Infection with the Leningrad-16 Vaccine Strain of Measles Virus

Glioblastoma multiforme (GBM) accounts for almost half of all primary malignant brain tumors in adults and has a poor prognosis. Here we demonstrated the oncolytic potential of the L-16 vaccine strain of measles virus (MV) against primary human GBM cells and characterized the genetic patterns that determine the sensitivity of primary human GBM cells to oncolytic therapy. MV replicated in all GBM cells, and seven out of eight cell lines underwent complete or partial oncolysis. RNA-Seq analysis identified about 1200 differentially expressed genes (FDR < 0.05) with at least two-fold expression level change between MV-infected and uninfected cells. Among them, the most significant upregulation was observed for interferon response, apoptosis and cytokine signaling. One out of eight GBM cell lines was defective in type I interferon production and, thus, in the post-interferon response, other cells lacked expression of different cellular defense factors. Thus, none of the cell lines displayed induction of the total gene set necessary for effective inhibition of MV replication. In the resistant cells, we detected aberrant expression of metalloproteinase genes, particularly MMP3. Thus, such genes could be considered intriguing candidates for further study of factors responsible for cell sensitivity and resistance to L-16 MV infection.