Oncolytic viruses as therapeutic cancer vaccines

The Multifaceted Role of Macrophages in Oncolytic Virotherapy

One of the cancer hallmarks is immune evasion mediated by the tumour microenvironment (TME). Oncolytic virotherapy is a form of immunotherapy based on the application of oncolytic viruses (OVs) that selectively replicate in and induce the death of tumour cells. Virotherapy confers reciprocal interaction with the host’s immune system. The aim of this review is to explore the role of macrophage-mediated responses in oncolytic virotherapy efficacy. The approach was to study current scientific literature in this field in order to give a comprehensive overview of the interactions of OVs and macrophages and their effects on the TME. The innate immune system has a central influence on the TME; tumour-associated macrophages (TAMs) generally have immunosuppressive, tumour-supportive properties. In the context of oncolytic virotherapy, macrophages were initially thought to predominantly contribute to anti-viral responses, impeding viral spread. However, macrophages have now also been found to mediate transport of OV particles and, after TME infiltration, to be subjected to a phenotypic shift that renders them pro-inflammatory and tumour-suppressive. These TAMs can present tumour antigens leading to a systemic, durable, adaptive anti-tumour immune response. After phagocytosis, they can recirculate carrying tissue-derived proteins, which potentially enables the monitoring of OV replication in the TME. Their role in therapeutic efficacy is therefore multifaceted, but based on research applying relevant, immunocompetent tumour models, macrophages are considered to have a central function in anti-cancer activity. These novel insights hold important clinical implications. When optimised, oncolytic virotherapy, mediating multifactorial inhibition of cancer immune evasion, could contribute to improved patient survival.

Combining Oncolytic Viruses and Small Molecule Therapeutics: Mutual Benefits

The focus of treating cancer with oncolytic viruses (OVs) has increasingly shifted towards achieving efficacy through the induction and augmentation of an antitumor immune response. However, innate antiviral responses can limit the activity of many OVs within the tumor and several immunosuppressive factors can hamper any subsequent antitumor immune responses. In recent decades, numerous small molecule compounds that either inhibit the immunosuppressive features of tumor cells or antagonize antiviral immunity have been developed and tested for. Here we comprehensively review small molecule compounds that can achieve therapeutic synergy with OVs. We also elaborate on the mechanisms by which these treatments elicit anti-tumor effects as monotherapies and how these complement OV treatment.

Co-delivery of novel bispecific and trispecific engagers by an amplicon vector augments the therapeutic effect of an HSV-based oncolytic virotherapy

BACKGROUND

Although oncolytic virotherapy has shown substantial promises as a new treatment modality for many malignancies, further improvement on its therapeutic efficacy will likely bring more clinical benefits. One plausible way of enhancing the therapeutic effect of virotherapy is to enable it with the ability to concurrently engage the infiltrating immune cells to provide additional antitumor mechanisms. Here, we report the construction and evaluation of two novel chimeric molecules (bispecific chimeric engager proteins, BiCEP and trispecific chimeric engager protein, TriCEP) that can engage both natural killer (NK) and T cells with tumor cells for enhanced antitumor activities.

METHODS

BiCEP was constructed by linking orthopoxvirus major histocompatibility complex class I-like protein, which can selectively bind to NKG2D with a high affinity to a mutant form of epidermal growth factor (EGF) that can strongly bind to EGF receptor. TriCEP is similarly constructed except that it also contains a modified form of interleukin-2 that can only function as a tethered form. As NKG2D is expressed on both NK and CD8⁺ T cells, both of which can thus be engaged by BiCEP and TriCEP.

RESULTS

Both BiCEP and TriCEP showed the ability to engage NK and T cells to kill tumor cells in vitro. Coadministration of BiCEP and TriCEP with an oncolytic herpes simplex virus enhanced the overall antitumor effect. Furthermore, single-cell RNA sequencing analysis revealed that TriCEP not only engaged NK and T cells to kill tumor cells, it also promotes the infiltration and activation of these important immune cells.

CONCLUSIONS

These novel chimeric molecules exploit the ability of the oncolytic virotherapy in altering the tumor microenvironment with increased infiltration of important immune cells such as NK and T cells for cancer immunotherapy. The ability of BiCEP and TriCEP to engage both NK and T cells makes them an ideal choice for arming an oncolytic virotherapy.

Combined with interventional therapy, immunotherapy can create a new outlook for tumor treatment

Recent progress in immunotherapy provides hope of a complete cure to cancer patients. However, recent studies have reported that only a limited number of cancer patients with a specific immune status, known as "cold tumor", can benefit from a single immune agent. Although the combination of immune agents with different mechanisms can partially increase the low response rate and improve efficacy, it can also result in more side effects. Therefore, discovering therapies that can improve tumors' response rate to immunotherapy without increasing toxicity for patients is urgently needed. Tumor interventional therapy is promising. It mainly includes transcatheter arterial chemoembolization, ablation, radioactive particle internal irradiation, and photodynamic interventional therapy based on a luminal stent. Interventional therapy can directly kill tumor cells by targeted drug delivery in situ, thus reducing drug dosage and systemic toxicity like cytokine release syndrome. More importantly, interventional therapy can regulate the immune system through numerous mechanisms, making it a suitable choice for immunotherapy to combine with. In this review, we provide a brief description of immunotherapies (and their side effects) on tumors of different immune types and preliminarily elaborate on interventional therapy mechanisms to improve immune efficacy. We also discuss the progress and challenges of the combination of interventional therapy and immunotherapy.

Viral Gene Therapy for Glioblastoma Multiforme: A Promising Hope for the Current Dilemma

Glioblastoma multiforme (GBM), as one of the most common malignant brain tumors, was limited in its treatment effectiveness with current options. Its invasive and infiltrative features led to tumor recurrence and poor prognosis. Effective treatment and survival improvement have always been a challenge. With the exploration of genetic mutations and molecular pathways in neuro-oncology, gene therapy is becoming a promising therapeutic approach. Therapeutic genes are delivered into target cells with viral vectors to act specific antitumor effects, which can be used in gene delivery, play an oncolysis effect, and induce host immune response. The application of engineering technology makes the virus vector used in genetics a more prospective future. Recent advances in viral gene therapy offer hope for treating brain tumors. In this review, we discuss the types and designs of viruses as well as their study progress and potential applications in the treatment of GBM. Although still under research, viral gene therapy is promising to be a new therapeutic approach for GBM treatment in the future.

Intratumoral expression of interleukin 23 variants using oncolytic vaccinia virus elicit potent antitumor effects on multiple tumor models via tumor microenvironment modulation

Background: Newly emerging cancer immunotherapy has led to significant progress in cancer treatment; however, its efficacy is limited in solid tumors since the majority of them are “cold” tumors. Oncolytic viruses, especially when properly armed, can directly target tumor cells and indirectly modulate the tumor microenvironment (TME), resulting in “hot” tumors. These viruses can be applied as a cancer immunotherapy approach either alone or in combination with other cancer immunotherapies. Cytokines are good candidates to arm oncolytic viruses. IL-23, an IL-12 cytokine family member, plays many roles in cancer immunity. Here, we used oncolytic vaccinia viruses to deliver IL-23 variants into the tumor bed and explored their activity in cancer treatment on multiple tumor models.

Methods: Oncolytic vaccinia viruses expressing IL-23 variants were generated by homologue recombination. The characteristics of these viruses were in vitro evaluated by RT-qPCR, ELISA, flow cytometry and cytotoxicity assay. The antitumor effects of these viruses were evaluated on multiple tumor models in vivo and the mechanisms were investigated by RT-qPCR and flow cytometry.

Results: IL-23 prolonged viral persistence, probably mediated by up-regulated IL-10. The sustainable IL-23 expression and viral oncolysis elevated the expression of Th1 chemokines and antitumor factors such as IFN-γ, TNF-α, Perforin, IL-2, Granzyme B and activated T cells in the TME, transforming the TME to be more conducive to antitumor immunity. This leads to a systemic antitumor effect which is dependent on CD8⁺ and CD4⁺ T cells and IFN-γ. Oncolytic vaccinia viruses could not deliver stable IL-23A to the tumor, attributed to the elevated tristetraprolin which can destabilize the IL-23A mRNA after the viral treatment; whereas vaccinia viruses could deliver membrane-bound IL-23 to elicit a potent antitumor effect which might avoid the possible toxicity normally associated with systemic cytokine exposure.

Conclusion: Either secreted or membrane-bound IL-23-armed vaccinia virus can induce potent antitumor effects and IL-23 is a candidate cytokine to arm oncolytic viruses for cancer immunotherapy.

MSCs loaded with oncolytic reovirus: migration and in vivo virus delivery potential for evaluating anti-cancer effect in tumor-bearing C57BL/6 mice

Background and aims

Several oncolytic viruses applications have been approved in the clinic or in different phases of clinical trials. However, these methods have some rudimentary problems. Therefore, to enhance the delivery and quality of treatment, considering the advantage of cell carrier-based methods such as Mesenchymal Stem Cells (MSC) have been proposed. This study was designed to evaluate the performance and quality of cancer treatment based on MSCs loaded by oncolytic reovirus in the cancerous C57BL/6 mouse model. Also, we evaluated MSCs migration potency in vitro and in vivo following the oncolytic reovirus infection.

Methods

C57BL/6 mice were inoculated with TC-1 cell lines and tumors were established in the right flank. Mice were systemically treated with reovirus, MSCs-loaded with reovirus, MSCs, and PBS as a control in separated groups. Effects of infected AD-MSCs with reovirus on tumor growth and penetration in the tumor site were monitored. All groups of mice were monitored for two months in order to therapeutic and anticancer potential. After treatments, tumor size alteration and apoptosis rate, as well as cytokine release pattern was assessed.

Results

The results of the current study indicated that the effect of reovirus infection on AD-MSCs is not devastating the migration capacity especially in MOI 1 and 5 while intact cells remain. On the other hand, MSCs play an efficient role as a carrier to deliver oncolytic virus into the tumor site in comparison with systemic administration of reovirus alone. Apoptosis intensity relies on viral titration and passing time. Followed by systemic administration, treatment with oncolytic reovirus-infected AD-MSCs and MSCs alone had shown significant inhibition in tumor growth. Also, treatment by reovirus causes an increase in IFN-γ secretion.

Conclusion

The results of in vitro and in vivo study confirmed the tumor-homing properties of infected AD-MSCs and the significant antitumor activity of this platform. Hence, our results showed that the cell carrier strategy using oncolytic reovirus-loaded AD-MSCs enhanced virus delivery, infiltration, and antitumor activity can be effectively applied in most cancers.

Therapeutic potential of interleukin-15 in cancer (Review)

The immune system is dysfunctional in cancer, and therapeutic approaches designated to restore immunity and increase long-term overall survival are desirable. The role of immunotherapy is to trigger the immune system to recognize and destroy tumor cells. Interleukin-15 (IL-15) is a member of the common gamma-chain (γc) cytokines that promote the differentiation and expansion of T cells, B cells and natural killer (NK) cells, leading to enhanced antitumor responses. This suggests that IL-15 is a promising candidate for anticancer therapy. Renewed interest in cancer immunotherapy has led to an increased number of preclinical studies and clinical trials that have investigated the reliability and potency of IL-15-based agents, not only as single therapy, but also in combination with others. This review provides a description of these studies which show the advantages and disadvantages of IL-15 as an immunotherapeutic agent. We present here the role of IL-15 and pharmacologically improved IL-15 superagonists as a single treatment or in combination with other therapeutic agents.

A mathematical model of viral oncology as an immuno-oncology instigator

We develop and analyse a mathematical model of tumour-immune interaction that explicitly incorporates heterogeneity in tumour cell cycle duration by using a distributed delay differential equation. We derive a necessary and sufficient condition for local stability of the cancer-free equilibrium in which the amount of tumour-immune interaction completely characterizes disease progression. Consistent with the immunoediting hypothesis, we show that decreasing tumour-immune interaction leads to tumour expansion. Finally, by simulating the mathematical model, we show that the strength of tumour-immune interaction determines the long-term success or failure of viral therapy.

IL-36γ-armed oncolytic virus exerts superior efficacy through induction of potent adaptive antitumor immunity

In this study, we aimed to apply the cytokine IL-36γ to cancer immunotherapy by constructing new oncolytic vaccinia viruses (OV) expressing interleukin-36γ (IL-36γ-OVs), leveraging unique synergism between OV and IL-36γ’s ability to promote antitumor adaptive immunity and modulate tumor microenvironment (TME). IL-36γ-OV had dramatic therapeutic efficacies in multiple murine tumor models, frequently leading to complete cancer eradication in large fractions of mice. Mechanistically, IL-36-γ-armed OV induced infiltration of lymphocytes and dendritic cells, decreased myeloid-derived suppressor cells and M2-like tumor-associated macrophages, and T cell differentiation into effector cells. Further study showed that IL-36γ-OV increased the number of tumor antigen-specific CD4⁺ and CD8⁺ T cells and the therapeutic efficacy depended on both CD8⁺ and CD4⁺ T cells. These results demonstrate that these IL36γ-armed OVs exert potent therapeutic efficacy mainly though antitumor immunity and they may hold great potential to advance treatment in human cancer patients.

Oncolytic virus promotes tumor-reactive infiltrating lymphocytes for adoptive cell therapy

Adoptive cell therapy (ACT) using tumor-specific tumor-infiltrating lymphocytes (TILs) has demonstrated success in patients where tumor-antigen specific TILs can be harvested from the tumor, expanded, and re-infused in combination with a preparatory regimen and IL2. One major issue for non-immunogenic tumors has been that the isolated TILs lack tumor specificity and thus possess limited in vivo therapeutic function. An oncolytic virus (OV) mediates an immunogenic cell death for cancer cells, leading to elicitation and dramatic enhancement of tumor-specific TILs. We hypothesized that the tumor-specific TILs elicited and promoted by an OV would be a great source for ACT for solid cancer. In this study, we show that a local injection of oncolytic poxvirus in MC38 tumor with low immunogenicity in C57BL/6 mice, led to elicitation and accumulation of tumor-specific TILs in the tumor tissue. Our analyses indicated that IL2-armed OV-elicited TILs contain lower quantities of exhausted PD-1hiTim-3+ CD8+ T cells and regulatory T cells. The isolated TILs from IL2-expressing OV-treated tumor tissue retained high tumor specificity after expansion ex vivo. These TILs resulted in significant tumor regression and improved survival after adoptive transfer in mice with established MC38 tumor. Our study showcases the feasibility of using an OV to induce tumor-reactive TILs that can be expanded for ACT.

Telomerase-specific oncolytic immunotherapy for promoting efficacy of PD-1 blockade in osteosarcoma

Immune checkpoint inhibitors including anti-programmed cell death 1 (PD-1) antibody have recently improved clinical outcome in certain cancer patients; however, osteosarcoma (OS) patients are refractory to PD-1 blockade. Oncolytic virotherapy has emerged as novel immunogenic therapy to augment antitumor immune response. We developed a telomerase-specific replication-competent oncolytic adenovirus OBP-502 that induces lytic cell death via binding to integrins. In this study, we assessed the combined effect of PD-1 blockade and OBP-502 in OS cells. The expression of coxsackie and adenovirus receptor (CAR), integrins αvβ3 and αvβ5, and programmed cell death ligand 1 (PD-L1) was analyzed in two murine OS cells (K7M2, NHOS). The cytopathic activity of OBP-502 in both cells was analyzed using the XTT assay. OBP-502-induced immunogenic cell death was assessed by analyzing the level of extracellular ATP and high-mobility group box protein B1 (HMGB1). Subcutaneous tumor models for K7M2 and NHOS cells were used to evaluate the antitumor effect and number of tumor-infiltrating CD8+ cells in combination therapy. K7M2 and NHOS cells showed high expression of integrins αvβ3 and αvβ5, but not CAR. OBP-502 significantly suppressed the viability of both cells, in which PD-L1 expression and the release of ATP and HMGB1 were significantly increased. Intratumoral injection of OBP-502 significantly augmented the efficacy of PD-1 blockade on subcutaneous K2M2 and NHOS tumor models via enhancement of tumor-infiltrating CD8+  T cells. Our results suggest that telomerase-specific oncolytic virotherapy is a promising antitumor strategy to promote the efficacy of PD-1 blockade in OS.

Retargeted and Multi-cytokine-Armed Herpes Virus Is a Potent Cancer Endovaccine for Local and Systemic Anti-tumor Treatment

Oncolytic viruses (OVs) are novel anti-tumor agents with the ability to selectively infect and kill tumor cells while sparing normal tissue. Beyond tumor cytolysis, OVs are capable of priming an anti-tumor immune response via lysis and cross-presentation of locally expressed endogenous tumor antigens, acting as an “endovaccine.” The effectiveness of OVs, similar to other immunotherapies, can be hampered by an immunosuppressive tumor microenvironment. In this study, we modified a previously generated oncolytic herpes simplex virus (oHSV) retargeted to the human HER2 (hHER2) tumor molecule and encoding murine interleukin-12 (mIL-12), by insertion of a second immunomodulatory molecule, murine granulocyte-macrophage colony-stimulating factor (mGM-CSF), to maximize therapeutic efficacy. We assessed the efficacy of this double-armed virus (R-123) compared to singly expressing GM-CSF and IL-12 oHSVs in tumor-bearing mice. While monotherapies were poorly effective, combination with α-PD1 enhanced the anti-tumor response, with the highest efficacy of 100% response rate achieved by the combination of R-123 and α-PD1. Efficacy was T cell-dependent, and the induced immunity was long lasting and able to reject a second contralateral tumor. Importantly, systemic delivery of R-123 combined with α-PD1 was effective in inhibiting the development of tumor metastasis. As such, this approach could have a significant therapeutic impact paving the way for further development of this platform in cancer immunotherapy.

Oncolytic Viruses as a Platform for the Treatment of Malignant Brain Tumors

Malignant brain tumors remain incurable diseases. Although much effort has been devoted to improving patient outcome, multiple factors such as the high tumor heterogeneity, the strong tumor-induced immunosuppressive microenvironment, and the low mutational burden make the treatment of these tumors especially challenging. Thus, novel therapeutic strategies are urgent. Oncolytic viruses (OVs) are biotherapeutics that have been selected or engineered to infect and selectively kill cancer cells. Increasingly, preclinical and clinical studies demonstrate the ability of OVs to recruit T cells and induce durable immune responses against both virus and tumor, transforming a “cold” tumor microenvironment into a “hot” environment. Besides promising clinical results as a monotherapy, OVs can be powerfully combined with other cancer therapies, helping to overcome critical barriers through the creation of synergistic effects in the fight against brain cancer. Although many questions remain to be answered to fully exploit the therapeutic potential of OVs, oncolytic virotherapy will clearly be part of future treatments for patients with malignant brain tumors.

Pharmacological Inhibition of WEE1 Potentiates the Antitumoral Effect of the dl922-947 Oncolytic Virus in Malignant Mesothelioma Cell Lines

Malignant mesothelioma (MM) is a very aggressive asbestos-related cancer, for which no therapy proves to be effective. We have recently shown that the oncolytic adenovirus dl922-947 had antitumor effects in MM cell lines and murine xenografts. Previous studies demonstrated that dl922-947-induced host cell cycle checkpoint deregulation and consequent DNA lesions associated with the virus efficacy. However, the cellular DNA damage response (DDR) can counteract this virus action. Therefore, we assessed whether AZD1775, an inhibitor of the G2/M DNA damage checkpoint kinase WEE1, could enhance MM cell sensitivity to dl922-947. Through cell viability assays, we found that AZD1775 synergized with dl922-947 selectively in MM cell lines and increased dl922-947-induced cell death, which showed hallmarks of apoptosis (annexinV-positivity, caspase-dependency, BCL-XL decrease, chromatin condensation). Predictably, dl922-947 and/or AZD1775 activated the DDR, as indicated by increased levels of three main DDR players: phosphorylated histone H2AX (γ-H2AX), phospho-replication protein A (RPA)32, phospho-checkpoint kinase 1 (CHK1). Dl922-947 also increased inactive Tyr-15-phosphorylated cyclin-dependent kinase 1 (CDK1), a key WEE1 substrate, which is indicative of G2/M checkpoint activation. This increase in phospho-CDK1 was effectively suppressed by AZD1775, thus suggesting that this compound could, indeed, abrogate the dl922-947-induced DNA damage checkpoint in MM cells. Overall, our data suggest that the dl922-947-AZD1775 combination could be a feasible strategy against MM.

Oncolytic Immunotherapy: Can't Start a Fire Without a Spark

Recent advances in cancer immunotherapy have renewed interest in oncolytic viruses (OVs) as a synergistic platform for the development of novel antitumor strategies. Cancer cells adopt multiple mechanisms to evade and suppress antitumor immune responses, essentially establishing a non-immunogenic ('cold') tumor microenvironment (TME), with poor T-cell infiltration and low mutational burden. Limitations to the efficacy of immunotherapy still exist, especially for a variety of solid tumors, where new approaches are necessary to overcome physical barriers in the TME and to mitigate adverse effects associated with current immunotherapeutics. OVs offer an attractive alternative by inducing direct oncolysis, immunogenic cell death, and immune stimulation. These multimodal mechanisms make OVs well suited to reprogram non-immunogenic tumors and TME into inflamed, immunogenic ('hot') tumors; enhanced release of tumor antigens by dying cancer cells is expected to augment T-cell infiltration, thereby eliciting potent antitumor immunity. Advances in virus engineering and understanding of tumor biology have allowed the optimization of OV-tumor selectivity, oncolytic potency, and immune stimulation. However, OV antitumor activity is likely to achieve its greatest potential as part of combinatorial strategies with other immune or cancer therapeutics.

Bi- and Tri-Specific T Cell Engager-Armed Oncolytic Viruses: Next-Generation Cancer Immunotherapy

Oncolytic viruses (OVs) are potent anti-cancer biologics with a bright future, having substantial evidence of efficacy in patients with cancer. Bi- and tri-specific antibodies targeting tumor antigens and capable of activating T cell receptor signaling have also shown great promise in cancer immunotherapy. In a cutting-edge strategy, investigators have incorporated the two independent anti-cancer modalities, transforming them into bi- or tri-specific T cell engager (BiTE or TriTE)-armed OVs for targeted immunotherapy. Since 2014, multiple research teams have studied this combinatorial strategy, and it showed substantial efficacy in various tumor models. Here, we first provide a brief overview of the current status of oncolytic virotherapy and the use of multi-specific antibodies for cancer immunotherapy. We then summarize progress on BiTE and TriTE antibodies as a novel class of cancer therapeutics in preclinical and clinical studies, followed by a discussion of BiTE- or TriTE-armed OVs for cancer therapy in translational models. In addition, T cell receptor mimics (TCRm) have been developed into BiTEs and are expected to greatly expand the application of BiTEs and BiTE-armed OVs for the effective targeting of intracellular tumor antigens. Future applications of such innovative combination strategies are emerging as precision cancer immunotherapies.

Myxoma Virus-Loaded Mesenchymal Stem Cells in Experimental Oncolytic Therapy of Murine Pulmonary Melanoma

Oncolytic viruses can target neoplasms, triggering oncolytic and immune effects. Their delivery to melanoma lesions remains challenging. Bone-marrow-derived mesenchymal stem cells (MSCs) were shown to be permissive for oncolytic myxoma virus (MYXV), allowing its transfer to melanoma cells, leading to their killing. Involvement of progeny virus was demonstrated in the transfer from MSCs to co-cultured melanoma cells. The inhibitory effect of virus on melanoma foci formation in murine lungs was revealed using melanoma cells previously co-cultured with MYXV-infected MSCs. Virus accumulation and persistence in lungs of lesion-bearing mice were shown following intravenous administration of MSC-shielded MYXV construct encoding luciferase. Therapy of experimentally induced lung melanoma in mice with interleukin (IL)-15-carrying MYXV construct delivered by MSCs led to marked regression of lesions and could increase survival. Elevated natural killer (NK) cell percentages in blood indicated robust innate responses against unshielded virus only. Lung infiltration by NK cells was followed by inflow of CD8+ T lymphocytes into melanoma lesions. Elevated expression of genes involved in adaptive immune response following oncolytic treatment was confirmed using RT-qPCR. No adverse pathological effects related to MSC-mediated oncolytic therapy with MYXV were observed. MSCs allow for safe and efficient ferrying of therapeutic MYXV to pulmonary melanoma foci triggering immune effects.

In Situ Therapeutic Cancer Vaccination with an Oncolytic Virus Expressing Membrane-Tethered IL-2

Successful in situ therapeutic vaccination would allow locally delivered oncolytic virus (OV) to exert systemic immunologic effects on metastases and improve survival. We have utilized bilateral flank tumor models to determine the most efficacious regimens of in situ vaccination. Intratumoral injection with membrane-tethered interleukin -2-armed OV (vvDD-mIL2) plus a Toll-like receptor 9 ligand (CpG) yielded systemic immunization and decreased tumor growth in a contralateral, noninjected tumor. Our main aims were to study the tumor immune microenvironment (TME) after vaccination and identify additional immune adjuvants that may improve the systemic tumor-specific immunity. Immunological profiles in the spleen showed an increased CD8+ T cell/regulatory T cell (Treg) ratio and increased CD11c+ cells after dual injection in one flank tumor. Concurrently, there was increased infiltration of tumor necrosis factor alpha (TNF-α)+CD8+ T cells and interferon gamma (IFN-γ)+CD4+ T cells and reduced CTLA-4+PD-1+CD8+ T cells in the contralateral, noninjected tumor. The anti-tumoral activity depended on CD8+ T cells and IFN-γ, but not CD4+ T cells. Based on the negative immune components still existing in the untreated tumors, we investigated additional adjuvants: clodronate liposome-mediated depletion of macrophages plus anti-PD-1 therapy. This regimen dramatically reduced the tumor burden in the noninjected tumor and increased median survival by 87%, suggesting that inhibition/elimination of suppressive components in the tumor microenvironment (TME) can improve therapeutic outcomes. This study emphasizes the importance of immune profiling to design rational, combined immunotherapy regimens ultimately to impact patient survival.

Elimination of MYCN-Amplified Neuroblastoma Cells by Telomerase-Targeted Oncolytic Virus via MYCN Suppression

Neuroblastoma (NB) is a primary malignant tumor of the peripheral sympathetic nervous system. High-risk NB is characterized by MYCN amplification and human telomerase reverse transcriptase (hTERT) rearrangement, contributing to hTERT activation and a poor outcome. For targeting hTERT-activated tumors, we developed two oncolytic adenoviruses, OBP-301 and tumor suppressor p53-armed OBP-702, in which the hTERT promoter drives expression of the viral E1 gene for tumor-specific virus replication. In this study, we demonstrate the therapeutic potential of the hTERT-driven oncolytic adenoviruses OBP-301 and OBP-702 using four human MYCN-amplified NB cell lines (IMR-32, CHP-134, NB-1, LA-N-5) exhibiting high hTERT expression. OBP-301 and OBP-702 exhibited a strong antitumor effect in association with autophagy in NB cells. Virus-mediated activation of E2F1 protein suppressed MYCN expression. OBP-301 and OBP-702 significantly suppressed the growth of subcutaneous CHP-134 tumors. Thus, these hTERT-driven oncolytic adenoviruses are promising antitumor agents for eliminating MYCN-amplified NB cells via E2F1-mediated suppression of MYCN protein.

Novel recombinant coxsackievirus B3 with genetically inserted basic peptide elicits robust antitumor activity against lung cancer

Cancer therapy that utilizes oncolytic virus may offer an exciting alternative, and coxsackievirus B3 (CVB3) is a potent oncolytic virus. This study was to assess the oncolytic activities of novel recombinant CVB3 with genetically inserted basic peptides in lung cancer. Recombinant CVB3 was produced in Vero cells, with or without genetically inserted basic peptides. In vitro and in vivo experiments with nude mouse models bearing human lung carcinoma xenografts were performed to examine the antitumor activities. Cytokines and immune responses to the recombinant CVB3 were determined in cynomolgus monkeys. Recombinant CVB3 with genetically inserted basic peptides was associated with significantly higher pH values within tumors. Mice treated with recombinant CVB3 showed significantly less tumor progression, and recombinant CVB3 with genetically inserted basic peptides appeared to enhance tumor suppression. Recombinant CVB3 was associated with significantly less proliferation of various lung cancer cells without affecting proliferation of normal lung fibroblasts. The cytokine profiles of the cynomolgus monkeys were comparable among control group (normal saline solution) and those given recombinant CVB3 with or without fused basic peptides, with no induction of excessive cytokine or immune responses. In conclusions, recombinant CVB3, especially those with fused basic peptides, possess strong antitumor activities without eliciting excessive immune responses.

Relevance of immune cell and tumor microenvironment imaging in the new era of immunotherapy

Tumor-infiltrating immune cells play a key role against cancer. However, malignant cells are able to evade the immune response and establish a very complex balance in which different immune subtypes may drive tumor progression, metastatization and resistance to therapy. New immunotherapeutic approaches aim at restoring the natural balance and increase immune response against cancer by different mechanisms. The complexity of these interactions and the heterogeneity of immune cell subpopulations are a real challenge when trying to develop new immunotherapeutics and evaluate or predict their efficacy in vivo. To this purpose, molecular imaging can offer non-invasive diagnostic tools like radiopharmaceuticals, contrast agents or fluorescent dyes. These agents can be useful for preclinical and clinical purposes and can overcome [18F]FDG limitations in discriminating between true-progression and pseudo-progression. This review provides a comprehensive overview of immune cells involved in microenvironment, available immunotherapies and imaging agents to highlight the importance of new therapeutic biomarkers and their in vivo evaluation to improve the management of cancer patients.

Targeting telomerase for its advent in cancer therapeutics

Telomerase has emerged as an important primary target in anticancer therapy. It is a distinctive reverse transcriptase enzyme, which extends the length of telomere at the 3' chromosomal end, and uses telomerase reverse transcriptase (TERT) and telomerase RNA template-containing domains. Telomerase has a vital role and is a contributing factor in human health, mainly affecting cell aging and cell proliferation. Due to its unique feature, it ensures unrestricted cell proliferation in malignancy and plays a major role in cancer disease. The development of telomerase inhibitors with increased specificity and better pharmacokinetics is being considered to design and develop newer potent anticancer agents. Use of natural and synthetic compounds for the inhibition of telomerase activity can lead to an opening of new vistas in cancer treatment. This review details about the telomerase biochemistry, use of natural and synthetic compounds; vaccines and oncolytic virus in therapy that suppress the telomerase activity. We have discussed structure-activity relationships of various natural and synthetic telomerase inhibitors to help medicinal chemists and chemical biology researchers with a ready reference and updated status of their clinical trials. Suppression of human TERT (hTERT) activity through inhibition of hTERT promoter is an important approach for telomerase inhibition.

Immunotherapy in anaplastic thyroid cancer

Anaplastic thyroid cancer (ATC) is one of the worst human malignancies, with an associated median survival of only 5 months. It is resistant to conventional thyroid cancer therapies, including radioiodine and thyroid-stimulating hormone suppression. Cancer immunotherapy has emerged over the past few decades as a transformative approach to treating a wide variety of cancers. However, immunotherapy for ATC is still in the experimental stage. This review will cover several strategies of immunotherapy and discuss the possible application of these strategies in the treatment of ATC (such as targeted therapy for tumor-associated macrophages, cancer vaccines, adoptive immunotherapy, monoclonal antibodies and immune checkpoint blockade) with the hope of improving the prognosis of ATC in the future.

Intratumoral Delivery of a PD-1-Blocking scFv Encoded in Oncolytic HSV-1 Promotes Antitumor Immunity and Synergizes with TIGIT Blockade

Oncolytic virotherapy can lead to systemic antitumor immunity, but the therapeutic potential of oncolytic viruses in humans is limited due to their insufficient ability to overcome the immunosuppressive tumor microenvironment (TME). Here, we showed that locoregional oncolytic virotherapy upregulated the expression of PD-L1 in the TME, which was mediated by virus-induced type I and type II IFNs. To explore PD-1/PD-L1 signaling as a direct target in tumor tissue, we developed a novel immunotherapeutic herpes simplex virus (HSV), OVH-aMPD-1, that expressed a single-chain variable fragment (scFv) against PD-1 (aMPD-1 scFv). The virus was designed to locally deliver aMPD-1 scFv in the TME to achieve enhanced antitumor effects. This virus effectively modified the TME by releasing damage-associated molecular patterns, promoting antigen cross-presentation by dendritic cells, and enhancing the infiltration of activated T cells; these alterations resulted in antitumor T-cell activity that led to reduced tumor burdens in a liver cancer model. Compared with OVH, OVH-aMPD-1 promoted the infiltration of myeloid-derived suppressor cells (MDSC), resulting in significantly higher percentages of CD155⁺ granulocytic-MDSCs (G-MDSC) and monocytic-MDSCs (M-MDSC) in tumors. In combination with TIGIT blockade, this virus enhanced tumor-specific immune responses in mice with implanted subcutaneous tumors or invasive tumors. These findings highlighted that intratumoral immunomodulation with an OV expressing aMPD-1 scFv could be an effective stand-alone strategy to treat cancers or drive maximal efficacy of a combination therapy with other immune checkpoint inhibitors.

A SIRPα-Fc fusion protein enhances the antitumor effect of oncolytic adenovirus against ovarian cancer

Oncolytic viruses armed with therapeutic transgenes of interest show great potential in cancer immunotherapy. Here, a novel oncolytic adenovirus carrying a signal regulatory protein-α (SIRPα)-IgG1 Fc fusion gene (termed SG635-SF) was constructed, which could block the CD47 'don't eat me' signal of cancer cells. A strong promoter sequence (CCAU) was chosen to control the expression of the SF fusion protein, and a 5/35 chimeric fiber was utilized to enhance the efficiency of infection. As a result, SG635-SF was found to specifically proliferate in hTERT-positive cancer cells and largely increased the abundance of the SF gene. The SF fusion protein was effectively detected, and CD47 was successfully blocked in SK-OV3 and HO8910 ovarian cancer cells expressing high levels of CD47. Although the ability to induce cell cycle arrest and cell death was comparable to that of the control empty SG635 oncolytic adenovirus in vitro, the antitumor effect of SG635-SF was significantly superior to that of SG635 in vivo. Furthermore, CD47 was largely blocked and macrophage infiltration distinctly increased in xenograft tissues of SK-OV3 cells but not in those of CD47-negative HepG2 cells, indicating that the enhanced antitumor effect of SG635-SF was CD47-dependent. Collectively, these findings highlight a potent antitumor effect of SG635-SF in the treatment of CD47-positive cancers.

Bone and Soft-Tissue Sarcoma: A New Target for Telomerase-Specific Oncolytic Virotherapy

Adenovirus serotype 5 (Ad5) is widely and frequently used as a virus vector in cancer gene therapy and oncolytic virotherapy. Oncolytic virotherapy is a novel antitumor treatment for inducing lytic cell death in tumor cells without affecting normal cells. Based on the Ad5 genome, we have generated three types of telomerase-specific replication-competent oncolytic adenoviruses: OBP-301 (Telomelysin), green fluorescent protein (GFP)-expressing OBP-401 (TelomeScan), and tumor suppressor p53-armed OBP-702. These viruses drive the expression of the adenoviral E1A and E1B genes under the control of the hTERT (human telomerase reverse transcriptase-encoding gene) promoter, providing tumor-specific virus replication. This review focuses on the therapeutic potential of three hTERT promoter-driven oncolytic adenoviruses against bone and soft-tissue sarcoma cells with telomerase activity. OBP-301 induces the antitumor effect in monotherapy or combination therapy with chemotherapeutic drugs via induction of autophagy and apoptosis. OBP-401 enables visualization of sarcoma cells within normal tissues by serving as a tumor-specific labeling reagent for fluorescence-guided surgery via induction of GFP expression. OBP-702 exhibits a profound antitumor effect in OBP-301-resistant sarcoma cells via activation of the p53 signaling pathway. Taken together, telomerase-specific oncolytic adenoviruses are promising antitumor reagents that are expected to provide novel therapeutic options for the treatment of bone and soft-tissue sarcomas.

Tumor-targeting oncolytic virus elicits potent immunotherapeutic vaccine responses to tumor antigens

Oncolytic viruses represent a promising therapeutic modality, but they have yet to live up to their therapeutic potential. Safety and efficacy concerns impel us to identify least toxic oncolytic agents that would generate durable and multifaceted anti-tumor immune responses to disrupt the tumors. Here we describe a rational engineered oncolytic herpes virus (OVH) that is a selective killer for targeting tumors, has strong safety records, induces complete regression of tumors in multiple tumor models, and elicits potent antitumor immunity. By far, the potential of OVs in promoting the tumor antigen-specific humoral immune responses remains obscure. In this study, we found that effective treatment by OVH induced immunogenic cell death, which facilitates to elicit humoral immune responses. Depletion experiments revealed that B cells were required for maximal antitumor efficacy of oncolytic immunotherapy. Both serum transfer and antibody treatment experiments revealed that endogenous oncolysis-induced antigen-targeting therapeutic antibodies can lead to systemic tumor regression. Our data demonstrate that tumor-targeting immune modulatory properties confer oncolytic OVH virotherapy as potent immunotherapeutic cancer vaccines that can generate specific and efficacious antitumor humoral responses by eliciting endogenous tumor antigen-targeting therapeutic antibodies in situ, resulting in an efficacious and tumor-specific therapeutic effect.

Immune Modulation by Telomerase-Specific Oncolytic Adenovirus Synergistically Enhances Antitumor Efficacy with Anti-PD1 Antibody

The clinical benefit of monotherapy involving immune checkpoint inhibitors (ICIs) such as anti-programmed death-1 antibody (PD-1 Ab) is limited to small populations. We previously developed a telomerase-specific oncolytic adenovirus, Telomelysin (OBP-301), the safety of which was confirmed in a phase I clinical study. Here, we examined the potential of OBP-502, an OBP-301 variant, as an agent for inducing immunogenic cell death (ICD) and synergistically enhancing the efficacy of OBP-502 with PD-1 Ab using CT26 murine colon cancer and PAN02 murine pancreatic cancer cell lines. OBP-502 induced the release of ICD molecules such as adenosine triphosphate (ATP) and high-mobility group box protein 1 (HMGB1) from CT26 and PAN02 cells, leading to recruitment of CD8-positive lymphocytes and inhibition of Foxp3-positive lymphocyte infiltration into tumors. Combination therapy involving OBP-502 intratumoral administration and PD-1 Ab systemic administration significantly suppressed the growth of not only OBP-502-treated tumors but also tumors not treated with OBP-502 (so-called abscopal effect) in CT26 and PAN02 bilateral subcutaneous tumor models, in which active recruitment of CD8-positve lymphocytes was observed even in tumors not treated with OBP-502. This combined efficacy was similar to that observed in a CT26 rectal orthotopic tumor model involving liver metastases. In conclusion, telomerase-specific oncolytic adenoviruses are promising candidates for combined therapies with ICIs.

Design and application of oncolytic viruses for cancer immunotherapy

The approval of the first oncolytic virus (OV) for the treatment of metastatic melanoma and the recent discovery that the use of oncolytic viruses may enhance cancer immunotherapies targeted against various immune checkpoint proteins have attracted great interest in the field of cancer virotherapy. OVs are designed to target and kill cancer cells leaving normal cell unharmed. OV infection and concomitant cancer cell killing stimulate anti-tumour immunity and modulates tumour microenvironment towards less immunosuppressive phenotype. The intrinsic capacity of OVs to turn immunologically cold tumours into immunologically hot tumours, and to increase immune cell and cytokine infiltration, can be further enhanced by arming OVs with transgenes that increase their immunostimulatory activities and direct immune responses specifically towards cancer cells. These OVs, specifically engineered to be used as cancer immunotherapeutics, can be synergized with other immune modulators or cytotoxic agents to achieve the most potent immunotherapy for cancer.

The alternative cap-binding complex is required for antiviral defense in vivo

Cellular response to environmental challenges requires immediate and precise regulation of transcriptional programs. During viral infections, this includes the expression of antiviral genes that are essential to combat the pathogen. Transcribed mRNAs are bound and escorted to the cytoplasm by the cap-binding complex (CBC). We recently identified a protein complex consisting of NCBP1 and NCBP3 that, under physiological conditions, has redundant function to the canonical CBC, consisting of NCBP1 and NCBP2. Here, we provide evidence that NCBP3 is essential to mount a precise and appropriate antiviral response. Ncbp3-deficient cells allow higher virus growth and elicit a reduced antiviral response, a defect happening on post-transcriptional level. Ncbp3-deficient mice suffered from severe lung pathology and increased morbidity after influenza A virus challenge. While NCBP3 appeared to be particularly important during viral infections, it may be more broadly involved to ensure proper protein expression.

Immunology of Adenoviral Vectors in Cancer Therapy

Adenoviruses are a commonly utilized virus for gene therapy platforms worldwide. Since adenovirus components are characterized as highly immunogenic, their immunogenicity inhibits the widespread use of adenoviral vectors to treat genetic disorders. However, stimulation of the immune response can be exploited for cancer immunotherapy platforms, and thus adenoviral vectors are used for therapeutic gene transfer, vaccines, and oncolytic agents in the cancer gene therapy field. It is now accepted that the generation of anti-tumor immune responses induced by oncolytic adenovirus treatments is critical for their anti-tumor efficacy. As such, in cancer immunotherapy with adenoviral vectors, a balance must be struck between induction of anti-adenoviral and anti-tumor immune responses. The recent trend in adenoviral-based cancer gene therapy is the development of adenoviral vectors to enhance immune responses and redirect them toward tumors. This review focuses on anti-adenoviral immunity and how adenovirotherapies skew the immune response toward an anti-tumor response.

Advances in Engineering Cells for Cancer Immunotherapy

Cancer immunotherapy aims to utilize the host immune system to kill cancer cells. Recent representative immunotherapies include T-cell transfer therapies, such as chimeric antigen receptor T cell therapy, antibody-based immunomodulator therapies, such as immune checkpoint blockade therapy, and cytokine therapies. Recently developed therapies leveraging engineered cells for immunotherapy against cancers have been reported to enhance antitumor efficacy while reducing side effects. Such therapies range from biologically, chemically and physically -engineered cells to bioinspired and biomimetic nanomedicines. In this review, advances of engineering cells for cancer immunotherapy are summarized, and prospects of this field are discussed.

Virotherapy as a Potential Therapeutic Approach for the Treatment of Aggressive Thyroid Cancer

Virotherapy is a novel cancer treatment based on oncolytic viruses (OVs), which selectively infect and lyse cancer cells, without harming normal cells or tissues. Several viruses, either naturally occurring or developed through genetic engineering, are currently under investigation in clinical studies. Emerging reports suggesting the immune-stimulatory property of OVs against tumor cells further support the clinical use of OVs for the treatment of lesions lacking effective therapies. Poorly differentiated thyroid carcinoma (PDTC) and anaplastic thyroid carcinoma (ATC), have a poor prognosis and limited treatment options. Therefore, several groups investigated the therapeutic potential of OVs in PDTC/ATC models producing experimental data sustaining the potential clinical efficacy of OVs in these cancer models. Moreover, the presence of an immunosuppressive microenvironment further supports the potential use of OVs in ATC. In this review, we present the results of the studies evaluating the efficacy of OVs alone or in combination with other treatment options. In particular, their potential therapeutic combination with multiple kinases inhibitors (MKIs) or immune checkpoint inhibitors are discussed.

Graphene oxide arms oncolytic measles virus for improved effectiveness of cancer therapy

BACKGROUND

Replication-competent oncolytic viruses (OVs) have been proven to be a potent anticancer weapon for clinical therapy. The preexisting neutralizing antibody in patients is a big challenge for oncolytic efficacy of OVs. Graphene oxide sheets (GOS) possess excellent biological compatibility and are easy to decorate for targeted delivery.

METHODS

We generated PEI-GOS-PEG-FA (Polyethyleneimine-Graphene oxide sheets-Polyethylene glycol-Folic acid). After intravenous injection, the distribution of PEI-GOS-PEG-FA in tumor-bearing mice was visualized by the IVIS Lumina XR system. Then, the oncolytic measles virus (MV-Edm) was coated with PEI-GOS-PEG-FA to form a viral-GOS complex (GOS/MV-Edm). The oncolytic effects of GOS/MV-Edm were investigated both in vitro and in vivo.

RESULTS

GOS/MV-Edm exhibited higher infectivity and enhanced oncolysis. In tumor-bearing mice, GOS/MV-Edm had significantly elevated viral replication within the tumor mass, and achieved an improved antitumor effect. Then, we confirmed that GOS/MV-Edm entered cancer cells via the folate receptor instead of CD46, a natural cognate receptor of MV-Edm. GOS/MV-Edm remained the infectivity in murine cells that lack CD46. Finally, we found that GOS/MV-Edm was effectively protected from neutralization in the presence of antiserum both in vitro and in vivo. In passively antiserum immunized tumor-bearing mice, the survival was remarkably improved with intravenous injection of GOS/MV-Edm.

CONCLUSION

Our findings demonstrate that GOS/MV-Edm displays significantly elevated viral replication within the tumor mass, leading to an improved antitumor effect in solid tumor mouse model. Our study provided a novel strategy to arm OVs for more efficient cancer therapy. That may become a promising therapeutic strategy for cancer patients.

Past, Current, and Future of Immunotherapies for Prostate Cancer

Prostate cancer (PCa) is the most common cancer in men, and the second leading cause of cancer related death in men in Western countries. The standard therapy for metastatic PCa is androgen suppression therapy (AST). Men undergoing AST eventually develop metastatic castration-resistant prostate cancer (mCRPC), of which there are limited treatment options available. Immunotherapy has presented substantial benefits for many types of cancer, but only a marginal benefit for mCRPC, at least in part, due to the immunosuppressive tumor microenvironment (TME). Current clinical trials are investigating monotherapies or combination therapies involving adoptive cellular therapy, viral, DNA vaccines, oncolytic viruses, and immune checkpoint inhibitors (ICI). Immunotherapies are also being combined with chemotherapy, radiation, and AST. Additionally, preclinical investigations show promise with the recent description of alternative ways to circumvent the immunosuppressive nature of the prostate tumor microenvironment, including harnessing the immune stimulatory NKG2D pathway, inhibiting myeloid derived suppressor cells, and utilizing immunomodulatory oncolytic viruses. Herein we provide an overview of recent preclinical and clinical developments in cancer immunotherapies and discuss the perspectives for future immunotherapies in PCa.

RNA-loaded dendritic cells: more than a tour de force in cancer therapeutics

A wide array of therapeutic strategies has been implemented against cancers, yet their clinical benefit is limited. The lack of clinical efficacy of the conventional treatment options might be due to the inept immune competency of the patients. Dendritic cells (DCs) have a vital role in initiating and directing immune responses and have been frequently used as delivery vehicles in clinical research. The recent clinical data suggest the potential use of DCs pulsed with nucleic acid, especially with RNA holds a great potential as an immunotherapeutic measure with compare to other cancer therapeutics. This review mainly deals with the DCs and their role in transfection with RNA in cancer immunotherapy.

Glioblastoma Treatment Modalities besides Surgery

Glioblastoma multiforme (GBM) is commonly known as the most aggressive primary CNS tumor in adults. The mean survival of it is 14 to 15 months, following the standard therapy from surgery, chemotherapy, to radiotherapy. Efforts in recent decades have brought many novel therapies to light, however, with limitations. In this paper, authors reviewed current treatments for GBM besides surgery. In the past decades, only radiotherapy, temozolomide (TMZ), and tumor treating field (TTF) were approved by FDA. Though promising in preclinical experiments, therapeutic effects of other novel treatments including BNCT, anti-angiogenic therapy, immunotherapy, epigenetic therapy, oncolytic virus therapy, and gene therapy are still either uncertain or discouraging in clinical results. In this review, we went through current clinical trials, underlying causes, and future therapy designs to present neurosurgeons and researchers a sketch of this field.

Recombinant Adenovirus Expressing a Soluble Fusion Protein PD-1/CD137L Subverts the Suppression of CD8+ T Cells in HCC

Oncolytic viruses are an excellent platform for developing effective strategies in cancer immunotherapy. Several challenges remain in the use of viro-immunotherapy for cancer, such as the lack of costimulatory signals and negative regulation of immune checkpoints. In this study, we designed a novel adenovirus expressing a soluble fusion protein, programmed cell death protein 1 (PD-1)/CD137L, which contains the extracellular domains of PD-1 and CD137L at each terminus (Ad5-PC). Ad5-PC preserved the costimulatory activity of CD137L and facilitated the persistence of activated CD8⁺ T cells. Ad5-PC induced strikingly increased antitumor activity in both ascitic and subcutaneous hepatocellular carcinoma (HCC) tumor models, with 70% and 60% long-term cure rates, respectively. The improved antitumor effect of Ad5-PC was attributed to the sustained high-level lymphocyte activation and interferon (IFN)-γ production in the tumor microenvironment, and was essentially dependent on CD8⁺ T cells rather than natural killer (NK) cells. Moreover, Ad5-huPC-expressing human soluble PD-1/CD137L fusion protein was effective in suppressing tumor growth and improving survival in a humanized mouse model. We confirmed that Ad5-PC induced tumor-specific and systematic protection against tumor rechallenges at both in situ and distant sites. Thus, Ad5-PC harnesses several distinct functions to efficiently overcome several major hurdles of viro-immunotherapy.

The Oncolytic Virus dl922-947 Triggers Immunogenic Cell Death in Mesothelioma and Reduces Xenograft Growth

Background: Malignant pleural mesothelioma (MPM) is an aggressive cancer associated with asbestos exposure that urgently requires effective therapeutic strategies. Current treatments are unable to increase significantly patient survival, which is often limited to <1 year from diagnosis. Virotherapy, based on the use of oncolytic viruses that exert anti-cancer effects by direct cell lysis and through the induction of anti-tumor immune response, represents an alternative therapeutic option for rare tumors with limited life expectancy. In this study, we propose the use of the adenovirus dl922-947, engineered to allow selective replication in cancer cells, to counteract MPM.

Methods: We performed a thorough preclinical assessment of dl922-947 effects in a set of MPM cell lines and xenografts. Cytotoxicity of dl922-947 alone and in combination assays was evaluated by sulforhodamine B assay. Cell cycle, calreticulin expression, and high mobility group box protein 1 (HMGB1) secretion were determined by flow cytometry, whereas ATP content was determined by a luminescence-based bioassay. The modulation of angiogenic factors in MPM-infected cells was evaluated through ELISA.

Results: We found that dl922-947 infection exhibits cytotoxic effects in MPM cell lines, affecting cell viability, cell cycle progression, and regulating main hallmarks of immunogenic cell death inducing calreticulin surface exposure, HMGB1 and ATP release. Our results also suggest that dl922-947 may affect angiogenic signals by regulation of VEGF-A and IL-8 secretion. Furthermore, dl922-947 shows anti-tumor efficacy in murine xenograft models reducing tumor growth and enhancing survival. Finally, the combination with cisplatin potentiated the cytotoxic effect of dl922-947.

Conclusions: Overall our data identify virotherapy, based on the use of dl922-947, as a new possible therapeutic strategy against MPM, which could be used alone, in combination with standard chemotherapy drugs, as shown here, or other approaches also aimed at enhancing the antitumoral immune response elicited by the virus.

The oncolytic efficacy and safety of avian reovirus and its dynamic distribution in infected mice

Primary liver cancer is a major public health challenge that ranks as the third most common cause of cancer worldwide despite therapeutic improvement. Reovirus has been emerging as a potential anti-cancer agent and is undergoing multiple clinical trials, and it is reported that reovirus can preferentially cause the cell death of a variety of cancers in a manner of apoptosis. As few studies have reported the efficacy of oncolytic activity and safety profile of avian reovirus, in our study, LDH assay, MTT assay, DAPI staining, and flow cytometry assay were performed to demonstrate the oncolytic effects of avian reovirus against the HepG2 cells, and quantitative real-time PCR (qRT-PCR) and animal experiments were conducted to investigate the dynamic distribution of avian reovirus in infected mice and then illustrate the safety and tissue tropism of avian reovirus. LDH assay, DAPI staining, and flow cytometry assay confirmed the efficacy of the oncotherapeutic effects of avian reovirus, and MTT assay has indicated that avian reovirus suppressed the proliferation of HepG2 cells and decreased their viability significantly. qRT-PCR revealed the dynamic distribution of avian reovirus in infected mice that avian reovirus might replicate better and have more powerful oncolytic activity in liver, kidney, and spleen tissues. Furthermore, histopathological examination clearly supported that avian reovirus appeared non-pathogenic to the normal host, so our study may provide the new insights and rationale for the new strategy of removing liver cancer.

Impact statement

We demonstrated the efficacy of oncolytic activity of avian reovirus (ARV) by LDH assay, MTT assay, DAPI staining, and flow cytometry assay, and also investigated the dynamic distribution of ARV in infected mice and then illustrated the safety and tissue tropism of ARV by quantitative real-time PCR (qRT-PCR) and animal experiments. Collectively, our study may provide the new insights and rationale for the new strategy of removing liver cancer.

Novel Delivery Systems for Checkpoint Inhibitors

Checkpoint inhibition (CPI) therapies have been proven to be powerful clinical tools in treating cancers. FDA approvals and ongoing clinical development of checkpoint inhibitors for treatment of various cancers highlight the immense potential of checkpoint inhibitors as anti-cancer therapeutics. The occurrence of immune-related adverse events, however, is a major hindrance to the efficacy and use of checkpoint inhibitors as systemic therapies in a wide range of patients. Hence, methods of sustained and tumor-targeted delivery of checkpoint inhibitors are likely to improve efficacy while also decreasing toxic side effects. In this review, we summarize the findings of the studies that evaluated methods of tumor-targeted delivery of checkpoint inhibitors, review their strengths and weaknesses, and discuss the outlook for therapeutic use of these delivery methods.

Oncolytic paramyxoviruses-induced autophagy; a prudent weapon for cancer therapy

Oncolytic virotherapy has currently emerged as a promising approach upon which scientists have been able to induce tumor-specific cell death in a broad spectrum of malignancies. Paramyxoviruses represent intrinsic oncolytic capability, which makes them excellent candidates to be widely used in oncolytic virotherapy. The mechanisms through which these viruses destroy the cancerous cells involve triggering the autophagic machinery and apoptosis in target cells. Interestingly, oncolytic paramyxoviruses have been found to induce autophagy and lead to tumor cells death rather than their survival. Indeed, the induction of autophagy has been revealed to enhance the immunogenicity of tumor cells via the release of damage-associated molecular patterns (DAMPs) and the activation of autophagy-related immunogenic cell death (ICD). Subsequent cross-presentation of tumor-associated antigens (TAA) through the MHC-I complex to CD8+ T cells results in the productive priming of the tumor-specific immune response. In this review, we first briefly discuss autophagy and explain the process of viral xenophagy. Finally, we focus on the interactions between virus and autophagy proteins, elaborating on the global preclinical studies on oncolytic paramyxoviruses.

A chimeric poxvirus with J2R (thymidine kinase) deletion shows safety and anti-tumor activity in lung cancer models

Oncolytic viruses have shown excellent safety profiles in preclinical and clinical studies; however, in most cases therapeutic benefits have been modest. We have previously reported the generation of a chimeric poxvirus (CF33), with significantly improved oncolytic characteristics, through chimerization among different poxviruses. Here we report the sequence analysis of CF33 and oncolytic potential of a GFP-encoding CF33 virus (CF33-GFP) with a J2R deletion in lung cancer models. Replication of CF33-GFP and the resulting cytotoxicity were higher in cancer cell lines compared to a normal cell line, in vitro. After infection with virus, cancer cells expressed markers for immunogenic cell death in vitro. Furthermore, CF33-GFP was safe and exerted potent anti-tumor effects at a dose as low as 1000 plaque forming units in both virus-injected and un-injected distant tumors in A549 tumor xenograft model in mice. Likewise, in a syngeneic model of lung cancer in mice, the virus showed significant anti-tumor effect and was found to increase tumor infiltration by CD8+ T cells. Collectively, these data warrant further investigation of this novel chimeric poxvirus for its potential use as a cancer bio-therapeutic.

STAT3 Contributes To Oncolytic Newcastle Disease Virus-Induced Immunogenic Cell Death in Melanoma Cells

Background: Oncolytic viruses (OVs) are emerging as potent inducers of immunogenic cell death (ICD), releasing danger-associated molecular patterns (DAMPs) that induce potent anticancer immunity. Oncolytic Newcastle disease virus (NDV) has been shown to educe ICD in both glioma and lung cancer cells. The objective of this study is to investigate whether oncolytic NDV induces ICD in melanoma cells and how it is regulated.

Methods: Various time points were actuated to check the expression and release of ICD markers induced by NDV strain, NDV/FMW in melanoma cell lines. The expression and release of ICD markers induced by oncolytic NDV strain, NDV/FMW, in melanoma cell lines at various time points were determined. Surface-exposed calreticulin (CRT) was inspected by confocal imaging. The supernatants of NDV/FMW infected cells were collected and concentrated for the determination of ATP secretion by ELISA, HMGB1, and HSP70/90 expression by immunoblot (IB) analysis. Pharmacological inhibition of apoptosis, autophagy, necroptosis, ER Stress, and STAT3 (signal transducer and activator of transcription 3) was achieved by treatment with small molecule inhibitors. Melanoma cell lines stably depleted of STAT3 were established with lentiviral constructs. Supernatants from NDV-infected cells were intratumorally injected to mice bearing melanoma cells-derived tumors.

Results: Oncolytic NDV induced CRT exposure, the release of HMGB1 and HSP70/90 as well as secretion of ATP in melanoma cells. Inhibition of apoptosis, autophagy, necroptosis or ER stress attenuated NDV/FMW-induced release of HMGB1 and HSP70/90. Moreover, NDV/FMW-induced ICD markers in melanoma cells were also suppressed by either treatment with a STAT3 inhibitor or shRNA-mediated depletion of STAT3. Of translational importance, treatment of mice bearing melanoma cells-derived tumors with supernatants from NDV/FMW-infected cells significantly inhibited tumor growth.

Conclusions: Our data authenticate that oncolytic NDV/FMW might be a potent inducer of ICD in melanoma cells, which is amalgamated with several forms of cell death. We also show that STAT3 plays a role in NDV/FMW-induced ICD in melanoma cells. Together, our data highlight oncolytic NDV as propitious for cancer therapeutics by stimulatingan anti-melanoma immune response.

From immune checkpoints to vaccines: The past, present and future of cancer immunotherapy

Cancer is a worldwide medical problem with significant repercussions on individual patients and societies as a whole. In order to alter the outcomes of this deadly disease the treatment of cancer over the centuries has undergone a unique evolution. However, utilizing the best treatment modalities and achieving cures or long-term durable responses have been inconsistent and limited, that is until recently. Contemporary research has highlighted a fundamental gap in our understanding of how we approach treating cancer, by revealing the intricate relationship between the immune system and tumors. In this atmosphere, the growth of immunotherapy has not only forever changed our understanding of cancer biology, but the manner by which we treat patients. It's paradigm shifting success has led to the approval of over 10 different immunotherapeutic agents, including checkpoint inhibitors, vaccine-based therapies, oncolytic viruses and T cell directed therapies for nearly 20 different indications across countless tumor types. Despite the breakthroughs that have occurred in the field of immunotherapy, it has not been the panacea for all cancers. With a deeper understanding of the immune system we have been able to peer into tumor immune escape and therapy resistance. Simultaneously this understanding has paved the way for the investigation and development of novel immune system altering agents and combinatorial therapies. In this chapter we review the immune system and its intricate relationship with cancer, the evolution of immunotherapy, its current landscape, and future directions in the context of resistance mechanisms and the challenges faced by immunotherapy against cancer.

Regression of solid breast tumours in mice by Newcastle disease virus is associated with production of apoptosis related-cytokines

BACKGROUND

Different strains of Newcastle disease virus (NDV) worldwide proved to have tumouricidal activity in several types of cancer cells. However, the possible anti-cancer activity of Malaysian NDV AF2240 strain and its mechanism of action remains unknown. The ability of cytokine-related apoptosis-inducing NDV AF2240 to treat breast cancer was investigated in the current study.

METHODS

A total of 90 mice were used and divided into 15 groups, each group comprising of 6 mice. Tumour, body weight and mortality of the mice were determined throughout the experiment, to observe the effect of NDV and NDV + tamoxifen treatments on the mice. In addition, the toxic effect of the treatments was determined through liver function test. In order to elucidate the involvement of cytokine production induced by NDV, a total of six cytokines, i.e. IL-6, IFN-γ, MCP-1, IL-10, IL12p70 and TNF-α were measured using cytometric bead array assay (plasma) and enzyme-linked immunosorbent spot (isolated splenocytes).

RESULTS

The results demonstrated that 4 T1 breast cancer cells in allotransplanted mice treated with AF2240 showed a noticeable inhibition of tumour growth and induce apoptotic-related cytokines.

CONCLUSIONS

NDV AF2240 suppression of breast tumour growth is associated with induction of apoptotic-related cytokines. It would be important to further investigate the molecular mechanism underlaying cytokines production by Newcastle disease virus.