Modulation of the Tumor Microenvironment by CXCR4 Antagonist-Armed Viral Oncotherapy Enhances the Antitumor Efficacy of Dendritic Cell Vaccines against Neuroblastoma in Syngeneic Mice

Current Knowledge and Perspectives of Immunotherapies for Neuroblastoma

Neuroblastoma (NBL) cells highly express disialoganglioside GD2, which is restricted and weakly expressed in selected healthy cells, making it a desirable target of immunotherapy. Over the past two decades, application of dinutuximab, an anti-GD2 monoclonal antibody (mAb), has been one of the few new therapies to substantially improve outcomes to current levels. Given the persistent challenge of relapse and therapeutic resistance, there is an urgent need for new effective and tolerable treatment options for high-risk NBL. Recent breakthroughs in immune checkpoint inhibitor (ICI) therapeutics have not translated into high-risk NBL, like many other major pediatric solid tumors. Given the suppressed tumor microenvironment (TME), single ICIs like anti-CTLA4 and anti-PD1 have not demonstrated significant antitumor response rates. Meanwhile, emerging studies are reporting novel advancements in GD2-based therapies, targeted therapies, nanomedicines, and other immunotherapies such as adoptive transfer of natural killer (NK) cells and chimeric antigen receptors (CARs), and these hold interesting promise for the future of high-risk NBL patient care. Herein, we summarize the current state of the art in NBL therapeutic options and highlight the unique challenges posed by NBL that have limited the successful adoption of immune-modifying therapies. Through this review, we aim to direct the field's attention to opportunities that may benefit from a combination immunotherapy strategy.

The Neuroblastoma Microenvironment, Heterogeneity and Immunotherapeutic Approaches

Neuroblastoma is a peripheral nervous system tumor that almost exclusively occurs in young children. Although intensified treatment modalities have led to increased patient survival, the prognosis for patients with high-risk disease is still around 50%, signifying neuroblastoma as a leading cause of cancer-related deaths in children. Neuroblastoma is an embryonal tumor and is shaped by its origin from cells within the neural crest. Hence, neuroblastoma usually presents with a low mutational burden and is, in the majority of cases, driven by epigenetically deregulated transcription networks. The recent development of Omic techniques has given us detailed knowledge of neuroblastoma evolution, heterogeneity, and plasticity, as well as intra- and intercellular molecular communication networks within the neuroblastoma microenvironment. Here, we discuss the potential of these recent discoveries with emphasis on new treatment modalities, including immunotherapies which hold promise for better future treatment regimens.

Revolutionizing pediatric neuroblastoma treatment: unraveling new molecular targets for precision interventions

Neuroblastoma (NB) is the most frequent solid tumor in pediatric cases, contributing to around 15% of childhood cancer-related deaths. The wide-ranging genetic, morphological, and clinical diversity within NB complicates the success of current treatment methods. Acquiring an in-depth understanding of genetic alterations implicated in the development of NB is essential for creating safer and more efficient therapies for this severe condition. Several molecular signatures are being studied as potential targets for developing new treatments for NB patients. In this article, we have examined the molecular factors and genetic irregularities, including those within insulin gene enhancer binding protein 1 (ISL1), dihydropyrimidinase-like 3 (DPYSL3), receptor tyrosine kinase-like orphan receptor 1 (ROR1) and murine double minute 2-tumor protein 53 (MDM2-P53) that play an essential role in the development of NB. A thorough summary of the molecular targeted treatments currently being studied in pre-clinical and clinical trials has been described. Recent studies of immunotherapeutic agents used in NB are also studied in this article. Moreover, we explore potential future directions to discover new targets and treatments to enhance existing therapies and ultimately improve treatment outcomes and survival rates for NB patients.

18F-FDG PET/CT-Based Radiomics Nomogram for Prediction of Bone Marrow Involvement in Pediatric Neuroblastoma: A Two-Center Study

RATIONALE AND OBJECTIVES

To assess the predictive ability of an 18F-FDG PET/CT-based radiomics nomogram for bone marrow involvement in pediatric neuroblastoma.

MATERIALS AND METHODS

A total of 241 neuroblastoma patients who underwent 18F-FDG PET/CT at two medical centers were retrospectively evaluated. Data from center A (n = 200) were randomized into a training cohort (n = 140) and an internal validation cohort (n = 60), while data from center B (n = 41) constituted the external validation cohort. For each patient, two regions of interest were defined using the tumor and axial skeleton. The clinical factors and radiomics features were derived to construct the clinical and radiomics models. The radiomics nomogram was built by combining clinical factors and radiomics features. The area under the receiver operating characteristic curves (AUCs) were used to assess the performance of the models.

RESULTS

Radiomics models created from tumor and axial skeleton achieved AUCs of 0.773 and 0.900, and the clinical model had an AUC of 0.858 in the training cohort. By incorporating clinical risk factors and axial skeleton-based radiomics features, the AUC of the radiomics nomogram in the training cohort, internal validation cohort, and external validation cohort was 0.932, 0.887, and 0.733, respectively.

CONCLUSION

The axial skeleton-based radiomics model performed better than the tumor-based radiomics model in predicting bone marrow involvement. Moreover, the radiomics nomogram showed that combining axial skeleton-based radiomics features with clinical risk factors improved their performance.

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.

Immunotherapies inducing immunogenic cell death in cancer: insight of the innate immune system

Cancer immunotherapies include monoclonal antibodies, cytokines, oncolytic viruses, cellular therapies, and other biological and synthetic immunomodulators. These are traditionally studied for their effect on the immune system's role in eliminating cancer cells. However, some of these therapies have the unique ability to directly induce cytotoxicity in cancer cells by inducing immunogenic cell death (ICD). Unlike general immune stimulation, ICD triggers specific therapy-induced cell death pathways, based on the release of damage-associated molecular patterns (DAMPs) from dying tumour cells. These activate innate pattern recognition receptors (PRRs) and subsequent adaptive immune responses, offering the promise of sustained anticancer drug efficacy and durable antitumour immune memory. Exploring how onco-immunotherapies can trigger ICD, enhances our understanding of their mechanisms and potential for combination strategies. This review explores the complexities of these immunotherapeutic approaches that induce ICD, highlighting their implications for the innate immune system, addressing challenges in cancer treatment, and emphasising the pivotal role of ICD in contemporary cancer research.

Oncolytic virotherapies for pediatric tumors

INTRODUCTION

Many pediatric patients with malignant tumors continue to suffer poor outcomes. The current standard of care includes maximum safe surgical resection followed by chemotherapy and radiation which may be associated with considerable long-term morbidity. The emergence of oncolytic virotherapy (OVT) may provide an alternative or adjuvant treatment for pediatric oncology patients.

AREAS COVERED

We reviewed seven virus types that have been investigated in past or ongoing pediatric tumor clinical trials: adenovirus (AdV-tk, Celyvir, DNX-2401, VCN-01, Ad-TD-nsIL-12), herpes simplex virus (G207, HSV-1716), vaccinia (JX-594), reovirus (pelareorep), poliovirus (PVSRIPO), measles virus (MV-NIS), and Senecavirus A (SVV-001). For each virus, we discuss the mechanism of tumor-specific replication and cytotoxicity as well as key findings of preclinical and clinical studies.

EXPERT OPINION

Substantial progress has been made in the past 10 years regarding the clinical use of OVT. From our review, OVT has favorable safety profiles compared to chemotherapy and radiation treatment. However, the antitumor effects of OVT remain variable depending on tumor type and viral agent used. Although the widespread adoption of OVT faces many challenges, we are optimistic that OVT will play an important role alongside standard chemotherapy and radiotherapy for the treatment of malignant pediatric solid tumors in the future.

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

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

Diagnostic Value of 18F-FDG PET/CT-Based Radiomics Nomogram in Bone Marrow Involvement of Pediatric Neuroblastoma

OBJECTIVES

To develop and validate an ¹⁸F-FDG PET/CT-based radiomics nomogram and evaluate the value of the ¹⁸F-FDG PET/CT-based radiomics nomogram for the diagnosis of bone marrow involvement (BMI) in pediatric neuroblastoma.

MATERIALS AND METHODS

A total of 144 patients with neuroblastoma (100 in the training cohort and 44 in the validation cohort) were retrospectively included. The PET/CT images of patients were visually assessed. The results of bone marrow aspirates or biopsies were used as the gold standard for BMI. Radiomics features and conventional PET parameters were extracted using the 3D slicer. Features were selected by the least absolute shrinkage and selection operator regression, and radiomics signature was constructed. Univariate and multivariate logistic regression analyses were applied to identify the independent clinical risk factors and construct the clinical model. Other different models, including the conventional PET model, combined PET-clinical model and combined radiomics model, were built using logistic regression. The combined radiomics model was based on clinical factors, conventional PET parameters and radiomics signature, which was presented as a radiomics nomogram. The diagnostic performance of the different models was evaluated by receiver operating characteristic (ROC) curves and decision curve analysis (DCA).

RESULTS

By visual assessment, BMI was observed in 80 patients. Four conventional PET parameters (SUVmax, SUVmean, metabolic tumor volume, and total lesion glycolysis) were extracted. And 15 radiomics features were selected to build the radiomics signature. The 11q aberration, neuron-specific enolase and vanillylmandelic acid were identified as the independent clinical risk factors to establish the clinical model. The radiomics nomogram incorporating the radiomics signature, the independent clinical risk factors and SUVmean demonstrated the best diagnostic value for identifying BMI, with an area under the curve (AUC) of 0.963 and 0.931 in the training and validation cohorts, respectively. And the DCA demonstrated that the radiomics nomogram was clinically useful.

CONCLUSION

The ¹⁸F-FDG PET/CT-based radiomics nomogram which incorporates radiomics signature, independent clinical risk factors and conventional PET parameters could improve the diagnostic performance for BMI of pediatric neuroblastoma without additional medical costs and radiation exposure.

Impaired Antitumor Immune Response in MYCN-amplified Neuroblastoma Is Associated with Lack of CCL2 Secretion and Poor Dendritic Cell Recruitment

In neuroblastoma, MYCN amplification is associated with sparse immune infiltrate and poor prognosis. Dendritic cells (DC) are crucial immune sentinels but their involvement in neuroblastoma pathogenesis is poorly understood. We observed that the migration of monocytes, myeloid and plasmacytoid DC induced by MYCN-nonamplified neuroblastoma supernatants was abrogated by the addition of anti-CCL2 antibodies, demonstrating the involvement of the CCR2/CCL2 axis in their recruitment by these tumors. Using public RNA sequencing and microarray datasets, we describe lower level of expression of CCL2 in MYCN-amplified neuroblastoma tumors, and we propose a working model for T-cell recruitment in neuroblastoma tumors in which CCL2 produced by neuroblastoma cells initiates the recruitment of monocytes, myeloid and plasmacytoid DCs. Among these cells, the CD1c⁺ subset may recruit T cells by means of CCL19/CCL22 secretion. In vitro, supernatants from DCs cocultured with neuroblastoma cell lines and activated contain CCL22 and CCL19, and are chemotactic for both CD4⁺ and CD8⁺ T cells. We also looked at immunomodulation induced by neuroblastoma cell lines, and found MYCN-nonamplified neuroblastoma cell lines were able to create a microenvironment where DC activation is enhanced. Overall, our findings highlight a major role for CCL2/CCR2 axis in monocytes, myeloid and plasmacytoid cells recruitment toward MYCN-nonamplified neuroblastoma, allowing further immune cell recruitment, and show that these tumors present a microenvironment that can favor DC responses.

Significance

In MYCN-nonamplified neuroblastoma, CCL2 produced by neuroblastoma cells induces the recruitment of antigen-presenting cells (DCs and monocytes/macrophages), allowing infiltration by T cells, in link with CCL19 and CCL22 production, hence favoring immune responses.

Immunovirotherapy for Pediatric Solid Tumors: A Promising Treatment That is Becoming a Reality

Immunotherapy has seen tremendous strides in the last decade, acquiring a prominent position at the forefront of cancer treatment since it has been proven to be efficacious for a wide variety of tumors. Nevertheless, while immunotherapy has changed the paradigm of adult tumor treatment, this progress has not yet been translated to the pediatric solid tumor population. For this reason, alternative curative therapies are urgently needed for the most aggressive pediatric tumors. In recent years, oncolytic virotherapy has consolidated as a feasible strategy for cancer treatment, not only for its tumor-specific effects and safety profile but also for its capacity to trigger an antitumor immune response. This review will summarize the current status of immunovirotherapy to treat cancer, focusing on pediatric solid malignancies. We will revisit previous basic, translational, and clinical research and discuss advances in overcoming the existing barriers and limitations to translate this promising therapeutic as an every-day cancer treatment for the pediatric and young adult populations.

Oncolytic Virotherapy in Peritoneal Metastasis Gastric Cancer: The Challenges and Achievements

Gastric cancer (GC) is the fourth most common cancer and the second leading cause of cancer death globally. Although the mortality rate in some parts of the world, such as East Asia, is still high, new treatments and lifestyle changes have effectively reduced deaths from this type of cancer. One of the main challenges of this type of cancer is its late diagnosis and poor prognosis. GC patients are usually diagnosed in the advanced stages of the disease, which is often associated with peritoneal metastasis (PM) and significantly reduces survival. This type of metastasis in patients with GC poses a serious challenge due to limitations in common therapies such as surgery and tumor resection, as well as failure to respond to systemic chemotherapy. To solve this problem, researchers have used virotherapy such as reovirus-based anticancer therapy in patients with GC along with PM who are resistant to current chemotherapies because this therapeutic approach is able to overcome immune suppression by activating dendritic cells (DCs) and eventually lead to the intrinsic activity of antitumor effector T cells. This review summarizes the immunopathogenesis of peritoneal metastasis of gastric cancer (PMGC) and the details for using virotherapy as an effective anticancer treatment approach, as well as its challenges and opportunities.

Progress of oncolytic virotherapy for neuroblastoma

As a neuroendocrine tumor derived from the neural crest, neuroblastoma (NB) is the most common extracranial solid tumor in children. The prognosis in patients with low- and intermediate-risk NB is favorable while that in high-risk patients is often detrimental. However, the management of the considerably large proportion of high-risk patients remains challenging in clinical practice. Among various new approaches, oncolytic virus (OV) therapy offers great advantages in tumor treatment, especially for high-risk NB. Genetic modified OVs can target NB specifically without affecting normal tissue and avoid the widespread drug resistance issue in anticancer monotherapy. Meanwhile, its safety profile provides great potential in combination therapy with chemo-, radio-, and immunotherapy. The therapeutic efficacy of OV for NB is impressive from bench to bedside. The effectiveness and safety of OVs have been demonstrated and reported in studies on children with NB. Furthermore, clinical trials on some OVs (Celyvir, Pexa-Vec (JX-594) and Seneca Valley Virus (NTX-010)) have reported great results. This review summarizes the latest evidence in the therapeutic application of OVs in NB, including those generated in cell lines, animal models and clinical trials.

Oncolytic ImmunoViroTherapy: A long history of crosstalk between viruses and immune system for cancer treatment

Cancer Immunotherapy relies on harnessing a patient's immune system to fine-tune specific anti-tumor responses and ultimately eradicate cancer. Among diverse therapeutic approaches, oncolytic viruses (OVs) have emerged as a novel form of cancer immunotherapy. OVs are a naturally occurring or genetically modified class of viruses able to selectively kill cancer cells, leaving healthy cells unharmed; in the last two decades, the role of OVs has been redefined to act beyond their oncolytic activity. Indeed, the immunogenic cancer cell death mediated by OVs induces the release of tumor antigens that in turn induces anti-tumor immunity, allowing OVs to act as in situ therapeutic cancer vaccines. Additionally, OVs can be engineered for intratumoral delivery of immunostimulatory molecules such as tumor antigens or cytokines to further enhance anti-tumor response. Moreover, OVs can be used in combination with other cancer immunotherapeutic approaches such as Immune Checkpoint Inhibitors and CAR-T cells. The current review first defines the three main mechanisms of action (MOA) of OVs currently used in cancer therapy that are: i) Oncolysis, ii) OV-induced cancer-specific immune activation, and iii) Exploiting pre-existing anti-viral immunity to enhance cancer therapy. Secondly, we focus on how OVs can induce and/or improve anti-cancer immunity in a specific or unspecific fashion, highlighting the importance of these approaches. Finally, the last part of the review analyses OVs combined with other cancer immunotherapies, revising present and future clinical applications.

The differentiation of new human CD303+ Plasmacytoid dendritic cell subpopulations expressing CD205 and/or CD103 regulated by Non-Small-Cell lung cancer cells

CD303⁺ plasmacytoid dendritic cells (pDCs) play an important role in the induction of immune tolerance and antitumor immunity. Here, we focused on the effect of NSCLC cells on the development of CD303⁺ pDC subsets expressing CD205 and/or CD103. The NSCLC cell line H1299 and primary NSCLC cells were incubated with DCs. The protein expression of costimulatory molecules on CD303⁺ pDCs, the production of pro-inflammatory and anti-inflammatory cytokines by CD303⁺ pDCs and the development of CD303⁺ pDC subsets were detected by using flow cytometry. Coculture with NSCLC cells modulates the protein expression of CD86 and HLA-DR on CD303⁺ pDCs. Moreover, NSCLC cells suppressed the production of IL-12 and IL-23 but facilitated the secretion of IL-27 and TGF-β by CD303⁺ pDCs. There were new CD303⁺ pDC subsets expressing CD205 and/or CD103 in healthy donors and NSCLC patients: CD303⁺CD205⁺CD103⁺, CD303⁺CD205⁺CD103^-, CD303⁺CD205^-CD103⁺ and CD303⁺CD205^-CD103^- pDCs. NSCLC cells modulated the differentiation of CD303⁺ pDC subpopulations by regulating the protein expression of CD205 and/or CD103 on CD303⁺ pDCs. NSCLC cells may regulate the immune functions of CD303⁺ pDCs by modulating the expression of costimulatory molecules on DCs and the production of pro-inflammatory/anti-inflammatory cytokines by DCs. NSCLC cells also regulate the development of CD303⁺ pDC subsets expressing CD205 and/or CD103. These outcomes may reveal a new cellular mechanism leading to the NSCLC-induced immune-suppressive microenvironment.

Recent Advances and Future Perspective of DC-Based Therapy in NSCLC

Current treatment for patients with non-small-cell lung cancer (NSCLC) is suboptimal since therapy is only effective in a minority of patients and does not always induce a long-lasting response. This highlights the importance of exploring new treatment options. The clinical success of immunotherapy relies on the ability of the immune system to mount an adequate anti-tumor response. The activation of cytotoxic T cells, the effector immune cells responsible for tumor cell killing, is of paramount importance for the immunotherapy success. These cytotoxic T cells are primarily instructed by dendritic cells (DCs). DCs are the most potent antigen-presenting cells (APCs) and are capable of orchestrating a strong anti-cancer immune response. DC function is often suppressed in NSCLC. Therefore, resurrection of DC function is an interesting approach to enhance anti-cancer immune response. Recent data from DC-based treatment studies has given rise to the impression that DC-based treatment cannot induce clinical benefit in NSCLC by itself. However, these are all early-phase studies that were mainly designed to study safety and were not powered to study clinical benefit. The fact that these studies do show that DC-based therapies were well-tolerated and could induce the desired immune responses, indicates that DC-based therapy is still a promising option. Especially combination with other treatment modalities might enhance immunological response and clinical outcome. In this review, we will identify the possibilities from current DC-based treatment trials that could open up new venues to improve future treatment.

Combined Effects of Myeloid Cells in the Neuroblastoma Tumor Microenvironment

Despite multimodal treatment, survival chances for high-risk neuroblastoma patients remain poor. Immunotherapeutic approaches focusing on the activation and/or modification of host immunity for eliminating tumor cells, such as chimeric antigen receptor (CAR) T cells, are currently in development, however clinical trials have failed to reproduce the preclinical results. The tumor microenvironment is emerging as a major contributor to immune suppression and tumor evasion in solid cancers and thus has to be overcome for therapies relying on a functional immune response. Among the cellular components of the neuroblastoma tumor microenvironment, suppressive myeloid cells have been described as key players in inhibition of antitumor immune responses and have been shown to positively correlate with more aggressive disease, resistance to treatments, and overall poor prognosis. This review article summarizes how neuroblastoma-driven inflammation induces suppressive myeloid cells in the tumor microenvironment and how they in turn sustain the tumor niche through suppressor functions, such as nutrient depletion and generation of oxidative stress. Numerous preclinical studies have suggested a range of drug and cellular therapy approaches to overcome myeloid-derived suppression in neuroblastoma that warrant evaluation in future clinical studies.

Artificial Tumor Microenvironments in Neuroblastoma

Simple Summary

Children with high-risk neuroblastoma have limited therapeutic options poor survival rates. The neuroblastoma tumor microenvironment contributes the lack of response to many interventions so innovative methods are needed to study the effects of the tumor microenvironment on new therapies. In this manuscript, we review the current literature related to the components of the tumor microenvironment and to the use of three-dimensional printing as modality to study cancer. This review highlights the potential for using three-dimensional printing to create an artificial tumor microenvironment in the presence of neuroblastoma to provide improved preclinical testing of novel therapies.

Abstract

In the quest to advance neuroblastoma therapeutics, there is a need to have a deeper understanding of the tumor microenvironment (TME). From extracellular matrix proteins to tumor associated macrophages, the TME is a robust and diverse network functioning in symbiosis with the solid tumor. Herein, we review the major components of the TME including the extracellular matrix, cytokines, immune cells, and vasculature that support a more aggressive neuroblastoma phenotype and encumber current therapeutic interventions. Contemporary treatments for neuroblastoma are the result of traditional two-dimensional culture studies and in vivo models that have been translated to clinical trials. These pre-clinical studies are costly, time consuming, and neglect the study of cofounding factors such as the contributions of the TME. Three-dimensional (3D) bioprinting has become a novel approach to studying adult cancers and is just now incorporating portions of the TME and advancing to study pediatric solid. We review the methods of 3D bioprinting, how researchers have included TME pieces into the prints, and highlight present studies using neuroblastoma. Ultimately, incorporating the elements of the TME that affect neuroblastoma responses to therapy will improve the development of innovative and novel treatments. The use of 3D bioprinting to achieve this aim will prove useful in developing optimal therapies for children with neuroblastoma.

Dendritic cell vaccine therapy for colorectal cancer

Colorectal cancer (CRC) remains a leading cause of cancer-related deaths in the United States despite an array of available treatment options. Current standard-of-care interventions for this malignancy include surgical resection, chemotherapy, and targeted therapies depending on the disease stage. Specifically, infusion of anti-vascular endothelial growth factor agents in combination with chemotherapy was an important development in improving the survival of patients with advanced colorectal cancer, while also helping give rise to other forms of anti-angiogenic therapies. Yet, one approach by which tumor angiogenesis may be further disrupted is through the administration of a dendritic cell (DC) vaccine targeting tumor-derived blood vessels, leading to cytotoxic immune responses that decrease tumor growth and synergize with other systemic therapies. Early generations of such vaccines exhibited protection against various forms of cancer in pre-clinical models, but clinical results have historically been disappointing. Sipuleucel-T (Provenge®) was the first, and to-date, only dendritic cell-based therapy to receive FDA approval after significantly increasing overall survival in prostate cancer patients. The unparalleled success of Sipuleucel-T has helped revitalize the clinical development of dendritic cell vaccines, which will be examined in this review. We also highlight the promise of these vaccines to instill anti-angiogenic immunity for individuals with advanced colorectal cancer.

Mesenchymal Stromal Cells in Neuroblastoma: Exploring Crosstalk and Therapeutic Implications

Neuroblastoma (NB) is the second most common solid cancer in childhood, accounting for 15% of cancer-related deaths in children. In high-risk NB patients, the majority suffers from metastasis. Despite intensive multimodal treatment, long-term survival remains <40%. The bone marrow (BM) is among the most common sites of distant metastasis in patients with high-risk NB. In this environment, small populations of tumor cells can persist after treatment (minimal residual disease) and induce relapse. Therapy resistance of these residual tumor cells in BM remains a major obstacle for the cure of NB. A detailed understanding of the microenvironment and its role in tumor progression is of utmost importance for improving the treatment efficiency of NB. In BM, mesenchymal stromal cells (MSCs) constitute an important part of the microenvironment, where they support hematopoiesis and modulate immune responses. Their role in tumor progression is not completely understood, especially for NB. Although MSCs have been found to promote epithelial-mesenchymal transition, tumor growth, and metastasis and to induce chemoresistance, some reports point toward a tumor-suppressive effect of MSCs. In this review, we aim to compile current knowledge about the role of MSCs in NB development and progression. We evaluate arguments that depict tumor-supportive versus -suppressive properties of MSCs in the context of NB and give an overview of factors involved in MSC-NB crosstalk. A focus lies on the BM as a metastatic niche, since that is the predominant site for NB metastasis and relapse. Finally, we will present opportunities and challenges for therapeutic targeting of MSCs in the BM microenvironment.

"Re-educating" Tumor Associated Macrophages as a Novel Immunotherapy Strategy for Neuroblastoma

Neuroblastoma is the most common extracranial pediatric tumor and often presents with metastatic disease, and patients with high-risk neuroblastoma have survival rates of ~50%. Neuroblastoma tumorigenesis is associated with the infiltration of various types of immune cells, including myeloid derived suppressor cells, tumor associated macrophages (TAMs), and regulatory T cells, which foster tumor growth and harbor immunosuppressive functions. In particular, TAMs predict poor clinical outcomes in neuroblastoma, and among these immune cells, TAMs with an M2 phenotype comprise an immune cell population that promotes tumor metastasis, contributes to immunosuppression, and leads to failure of radiation or checkpoint inhibitor therapy. This review article summarizes the role of macrophages in tumor angiogenesis, metastasis, and immunosuppression in neuroblastoma and discusses the recent advances in "macrophage-targeting strategies" in neuroblastoma with a focus on three aspects: (1) inhibition of macrophage recruitment, (2) targeting macrophage survival, and (3) reprogramming of macrophages into an immunostimulatory phenotype.

Engineering vaccinia virus as an immunotherapeutic battleship to overcome tumor heterogeneity

INTRODUCTION

Immunotherapy is a rapidly evolving area of cancer therapeutics aimed at driving a systemic immune response to fight cancer. Oncolytic viruses (OVs) are at the cutting-edge of innovation in the immunotherapy field. Successful OV platforms must be effective in reshaping the tumor microenvironment and controlling tumor burden, but also be highly specific to avoid off-target side effects. Large DNA viruses, like vaccinia virus (VACV), have a large coding capacity, enabling the encoding of multiple immunostimulatory transgenes to reshape the tumor immune microenvironment. VACV-based OVs have shown promising results in both pre-clinical and clinical studies, including safe and efficient intravenous delivery to metastatic tumors.

AREA COVERED

This review summarizes attenuation strategies to generate a recombinant VACV with optimal tumor selectivity and immunogenicity. In addition, we discuss immunomodulatory transgenes that have been introduced into VACV and summarize their effectiveness in controlling tumor burden.

EXPERT OPINION

VACV encodes several immunomodulatory genes which aid the virus in overcoming innate and adaptive immune responses. Strategic deletion of these virulence factors will enable an optimal balance between viral persistence and immunogenicity, robust tumor-specific expression of payloads and promotion of a systemic anti-cancer immune response. Rational selection of therapeutic transgenes will maximize the efficacy of OVs and their synergy in combinatorial immunotherapy schemes.

Delivery and Biosafety of Oncolytic Virotherapy

In recent years, oncolytic virotherapy has emerged as a promising anticancer therapy. Oncolytic viruses destroy cancer cells, without damaging normal tissues, through virus self-replication and antitumor immunity responses, showing great potential for cancer treatment. However, the clinical guidelines for administering oncolytic virotherapy remain unclear. Delivery routes for oncolytic virotherapy to patients vary in existing studies, depending on the tumor sites and the objective of studies. Moreover, the biosafety of oncolytic virotherapy, including mainly uncontrolled adverse events and long-term complications, remains a serious concern that needs to be accurately measured. This review provides a comprehensive and detailed overview of the delivery and biosafety of oncolytic virotherapy.

Dendritic Cells and Immunogenic Cancer Cell Death: A Combination for Improving Antitumor Immunity

The safety and feasibility of dendritic cell (DC)-based immunotherapies in cancer management have been well documented after more than twenty-five years of experimentation, and, by now, undeniably accepted. On the other hand, it is equally evident that DC-based vaccination as monotherapy did not achieve the clinical benefits that were predicted in a number of promising preclinical studies. The current availability of several immune modulatory and targeting approaches opens the way to many potential therapeutic combinations. In particular, the evidence that the immune-related effects that are elicited by immunogenic cell death (ICD)-inducing therapies are strictly associated with DC engagement and activation strongly support the combination of ICD-inducing and DC-based immunotherapies. In this review, we examine the data in recent studies employing tumor cells, killed through ICD induction, in the formulation of anticancer DC-based vaccines. In addition, we discuss the opportunity to combine pharmacologic or physical therapeutic approaches that can promote ICD in vivo with in situ DC vaccination.

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.

Trial watch: dendritic cell vaccination for cancer immunotherapy

Dendritic- cells (DCs) have received considerable attention as potential targets for the development of anticancer vaccines. DC-based anticancer vaccination relies on patient-derived DCs pulsed with a source of tumor-associated antigens (TAAs) in the context of standardized maturation-cocktails, followed by their reinfusion. Extensive evidence has confirmed that DC-based vaccines can generate TAA-specific, cytotoxic T cells. Nonetheless, clinical efficacy of DC-based vaccines remains suboptimal, reflecting the widespread immunosuppression within tumors. Thus, clinical interest is being refocused on DC-based vaccines as combinatorial partners for T cell-targeting immunotherapies. Here, we summarize the most recent preclinical/clinical development of anticancer DC vaccination and discuss future perspectives for DC-based vaccines in immuno-oncology.

Combination of PET and CXCR4-Targeted Peptide Molecule Agents for Noninvasive Tumor Monitoring

Precision medicine is emphasizing not only at individual but also at disease molecule level in modern medicine. Therefore, target-specific molecular agents are crucial for precise diagnosis and treatment. We developed a peptide agent that binds a critical chemokine receptor-CXCR4 and could be used to detect tumor status. Confocal images showed binding of the peptide agent to human osteosarcoma cells. Clinical gold-standard molecular imaging agent PET showed tumors had high glucose metabolism, CT showed that these xenograft tumors were calcified and displayed hypervascularity. Peptide imaging demonstrated that these tumors were CXCR4 positive. However, Western blot protein analysis revealed a discordance between the tumor and the CXCR4 targeted agent, suggesting that small changes in peptide sequences have profound effect on binding to their targets. We also demonstrated the molecular screening by modifying the peptide sequence and thereby altering the binding properties of the agent. In conclusion, this study demonstrates that small molecule peptide agents can be used as an additional diagnostic tool for precision medicine.

State of the art in immunotherapy of neuroblastoma

Neuroblastoma (NB) is a common and deadly malignancy mostly observed in children. Evolution of therapeutic options for NB led to the addition of immunotherapeutic modalities to the previously recruited chemotherapeutic options. Molecular studies of the NB cells resulted in the discovery of many tumor-associated genes and antigens such as MYCN gene and GD2. MYCN gene and GD2 surface antigen are two of the most practical discoveries regarding immunotherapy of neuroblastoma. The GD2 antigen has been targeted in many animal and human studies including Phase III clinical trials. Even though these antigens have changed the face of pediatric neuroblastoma, they do not take as much credit in immunotherapy of adult-onset neuroblastoma. Monoclonal antibodies have been designed to detect this antigen on the surface of NB tumor cells. Despite bettering the outcomes for NB patients, current therapies still fail in many cases. Studies are underway to discover more specific tumor-associated antigens and more effective treatment options. In the current narrative, immunotherapy of NB - from emerging of this therapeutic backbone in NB to the latest discoveries regarding this malignancy - has been reviewed.

Poxvirus oncolytic virotherapy

INTRODUCTION

Over the last decade, advances in biological therapies have resulted in remarkable clinical responses for the treatment of some previously incurable cancers. Oncolytic virotherapy is one of these promising novel strategies for cancer therapy. A successful oncolytic virus promotes tumor cell oncolysis and elicits a robust long-term anti-tumor immunity.

AREAS COVERED

Oncolytic poxviruses (Vaccinia virus and Myxoma virus) demonstrated encouraging results in multiple pre-clinical tumor models and some clinical trials for the treatment of various cancers. This review summarizes the advances made on poxvirus oncolytic virotherapy in the last five years.

EXPERT OPINION

Many challenges remain in poxvirus oncolytic virotherapy. Two key goals to achieve are enhancing the efficiency of viral delivery to tumor sites and overcoming local tumor immune-evasion. Additional efforts are necessary to explore the best combination of virotherapy with standard available treatments, particularly immunotherapies. By addressing these issues, this new modality will continue to improve as an adjunct biotherapy to treat malignant diseases.