First oncolytic virus approved for melanoma immunotherapy

Oncolytic activity of naturally attenuated herpes-simplex virus HF10 against an immunocompetent model of oral carcinoma

Prognosis for advanced oral carcinoma remains poor. Oncolytic virotherapy uses replication-competent viruses to infect and kill only the tumor cells. However, it has been difficult to investigate the oncolytic activity of viruses against oral carcinomas in mouse models. This study established a mouse model of oral cancer and investigated the in vitro and in vivo anti-tumor effects of HF10, a highly attenuated, replication-competent herpes simplex virus (HSV)-1. Mouse tongue cancer was induced by injecting 4-nitroquinoline 1-oxide into the mouse tongue. The murine oral cancer cell line isolated from this tumor, named NMOC1, formed invasive carcinoma within a week when injected into mouse tongue. HF10 successfully infected, replicated, and spread in the cancer cells in vitro. HF10 was able to kill cancer cells isolated from human or mouse tongue tumor. HF10 injection into tongue carcinomas prolonged mouse survival without any side effects or weight loss. Intertumoral injection of GFP-expressing HF10 confirmed that viral spread was confined within the tumors. Immunohistochemical staining showed that HF10 induced infiltration of CD8-positive T cells around HSV-infected cells in the tumor mass, implying increased anti-tumor immunity. We successfully established an oral cancer cell line and showed that HF10 is a promising therapeutic agent for oral cancer.

Delivery systems for enhancing oncolytic adenoviruses efficacy

Oncolytic adenovirus (OAds) has long been considered a promising biotherapeutic agent against various types of cancer owing to selectively replicate in and lyse cancer cells, while remaining dormant in healthy cells. In the last years, multiple (pre)clinical studies using genetic engineering technologies enhanced OAds anti-tumor effects in a broad range of cancers. However, poor targeting delivery, tropism toward healthy tissues, low-level expression of Ad receptors on tumor cells, and pre-existing neutralizing antibodies are major hurdles for systemic administration of OAds. Different vehicles have been developed for addressing these obstacles, such as stem cells, nanoparticles (NPs) and shielding polymers, extracellular vesicles (EVs), hydrogels, and microparticles (MPs). These carriers can enhance the therapeutic efficacy of OVs through enhancing transfection, circulatory longevity, cellular interactions, specific targeting, and immune responses against cancer. In this paper, we reviewed adenovirus structure and biology, different types of OAds, and the efficacy of different carriers in systemic administration of OAds.

Current Status and Challenges Associated with CNS-Targeted Gene Delivery across the BBB

The era of the aging society has arrived, and this is accompanied by an increase in the absolute numbers of patients with neurological disorders, such as Alzheimer’s disease (AD) and Parkinson’s disease (PD). Such neurological disorders are serious costly diseases that have a significant impact on society, both globally and socially. Gene therapy has great promise for the treatment of neurological disorders, but only a few gene therapy drugs are currently available. Delivery to the brain is the biggest hurdle in developing new drugs for the central nervous system (CNS) diseases and this is especially true in the case of gene delivery. Nanotechnologies such as viral and non-viral vectors allow efficient brain-targeted gene delivery systems to be created. The purpose of this review is to provide a comprehensive review of the current status of the development of successful drug delivery to the CNS for the treatment of CNS-related disorders especially by gene therapy. We mainly address three aspects of this situation: (1) blood-brain barrier (BBB) functions; (2) adeno-associated viral (AAV) vectors, currently the most advanced gene delivery vector; (3) non-viral brain targeting by non-invasive methods.

Overcoming Immune Evasion in Melanoma

Melanoma is the most aggressive and dangerous form of skin cancer that develops from transformed melanocytes. It is crucial to identify melanoma at its early stages, in situ, as it is "curable" at this stage. However, after metastasis, it is difficult to treat and the five-year survival is only 25%. In recent years, a better understanding of the etiology of melanoma and its progression has made it possible for the development of targeted therapeutics, such as vemurafenib and immunotherapies, to treat advanced melanomas. In this review, we focus on the molecular mechanisms that mediate melanoma development and progression, with a special focus on the immune evasion strategies utilized by melanomas, to evade host immune surveillances. The proposed mechanism of action and the roles of immunotherapeutic agents, ipilimumab, nivolumab, pembrolizumab, and atezolizumab, adoptive T- cell therapy plus T-VEC in the treatment of advanced melanoma are discussed. In this review, we implore that a better understanding of the steps that mediate melanoma onset and progression, immune evasion strategies exploited by these tumor cells, and the identification of biomarkers to predict treatment response are critical in the design of improved strategies to improve clinical outcomes for patients with this deadly disease.

Generation of an Oncolytic Herpes Simplex Viral Vector Completely Retargeted to the GDNF Receptor GFRα1 for Specific Infection of Breast Cancer Cells

Oncolytic herpes simplex viruses (oHSV) are under development for the treatment of a variety of human cancers, including breast cancer, a leading cause of cancer mortality among women worldwide. Here we report the design of a fully retargeted oHSV for preferential infection of breast cancer cells through virus recognition of GFRα1, the cellular receptor for glial cell-derived neurotrophic factor (GDNF). GFRα1 displays a limited expression profile in normal adult tissue, but is upregulated in a subset of breast cancers. We generated a recombinant HSV expressing a completely retargeted glycoprotein D (gD), the viral attachment/entry protein, that incorporates pre-pro-GDNF in place of the signal peptide and HVEM binding domain of gD and contains a deletion of amino acid 38 to eliminate nectin-1 binding. We show that GFRα1 is necessary and sufficient for infection by the purified recombinant virus. Moreover, this virus enters and spreads in GFRα1-positive breast cancer cells in vitro and caused tumor regression upon intratumoral injection in vivo. Given the heterogeneity observed between and within individual breast cancers at the molecular level, these results expand our ability to deliver oHSV to specific tumors and suggest opportunities to enhance drug or viral treatments aimed at other receptors.

Cytokines in oncolytic virotherapy

Tumors represent a hostile environment for the effector cells of cancer immunosurveillance. Immunosuppressive receptors and soluble or membrane-bound ligands are abundantly exposed and released by malignant entities and their stromal accomplices. As a consequence, executioners of antitumor immunity inefficiently navigate across cancer tissues and fail to eliminate malignant targets. By inducing immunogenic cancer cell death, oncolytic viruses profoundly reshape the tumor microenvironment. They trigger the local spread of danger signals and tumor-associated (as well as viral) antigens, thus attracting antigen-presenting cells, promoting the activation and expansion of lymphocytic populations, facilitating their infiltration in the tumor bed, and reinvigorating cytotoxic immune activity. The present review recapitulates key chemokines, growth factors and other cytokines that orchestrate this ballet of antitumoral leukocytes upon oncolytic virotherapy.

Neospora caninum: a new class of biopharmaceuticals in the therapeutic arsenal against cancer

BACKGROUND

Microorganisms that can be used for their lytic activity against tumor cells as well as inducing or reactivating antitumor immune responses are a relevant part of the available immunotherapy strategies. Viruses, bacteria and even protozoa have been largely explored with success as effective human antitumor agents. To date, only one oncolytic virus-T-VEC-has been approved by the US Food and Drug Administration for use in biological cancer therapy in clinical trials. The goal of our study is to evaluate the potential of a livestock pathogen, the protozoan Neospora caninum, non-pathogenic in humans, as an effective and safe antitumorous agent.

METHODS/RESULTS

We demonstrated that the treatment of murine thymoma EG7 by subcutaneous injection of N. caninum tachyzoites either in or remotely from the tumor strongly inhibits tumor development, and often causes their complete eradication. Analysis of immune responses showed that N. caninum had the ability to 1) lyze infected cancer cells, 2) reactivate the immunosuppressed immune cells and 3) activate the systemic immune system by generating a protective antitumor response dependent on natural killer cells, CD8-T cells and associated with a strong interferon (IFN)-γ secretion in the tumor microenvironment. Most importantly, we observed a total clearance of the injected agent in the treated animals: N. caninum exhibited strong anticancer effects without persisting in the organism of treated mice. We also established in vitro and an in vivo non-obese diabetic/severe combined immunodeficiency mouse model that N. caninum infected and induced a strong regression of human Merkel cell carcinoma. Finally, we engineered a N. caninum strain to secrete human interleukin (IL)-15, associated with the alpha-subunit of the IL-15 receptor thus strengthening the immuno-stimulatory properties of N. caninum. Indeed, this NC1-IL15hRec strain induced both proliferation of and IFN-γ secretion by human peripheral blood mononuclear cells, as well as improved efficacy in vivo in the EG7 tumor model.

CONCLUSION

These results highlight N. caninum as a potential, extremely effective and non-toxic anticancer agent, capable of being engineered to either express at its surface or to secrete biodrugs. Our work has identified the broad clinical possibilities of using N. caninum as an oncolytic protozoan in human medicine.

CRISPR-Cas12a with an oAd Induces Precise and Cancer-Specific Genomic Reprogramming of EGFR and Efficient Tumor Regression

CRISPR-Cas12a represents a class 2/type V CRISPR RNA-guided endonuclease, holding promise as a precise genome-editing tool in vitro and in vivo. For efficient delivery of the CRISPR-Cas system into cancer, oncolytic adenovirus (oAd) has been recognized as a promising alternative vehicle to conventional cancer therapy, owing to its cancer specificity; however, to our knowledge, it has not been used for genome editing. In this study, we show that CRISPR-Cas12a mediated by oAd disrupts the oncogenic signaling pathway with excellent cancer specificity. The intratumoral delivery of a single oAd co-expressing a Cas12a and a CRISPR RNA (crRNA) targeting the epidermal growth factor receptor (EGFR) gene (oAd/Cas12a/crEGFR) induces efficient and precise editing of the targeted EGFR gene in a cancer-specific manner, without detectable off-target nuclease activity. Importantly, oAd/Cas12a/crEGFR elicits a potent antitumor effect via robust induction of apoptosis and inhibition of tumor cell proliferation, ultimately leading to complete tumor regression in a subset of treated mice. Collectively, in this study we show precise genomic reprogramming via a single oAd vector-mediated CRISPR-Cas system and the feasibility of such system as an alternative cancer therapy.

Successful gene therapy requires targeting the vast majority of cancer cells

Suicide gene therapy using gene-directed enzyme prodrug therapy (GDEPT) is based on delivering a gene-encoded enzyme to cells that converts a nontoxic prodrug into its toxic metabolite. The bystander effect is thought to compensate for inefficiencies in delivery and expression because the produced toxic metabolite can spread to adjacent non-expressing cells.

The purpose of this study was to assess the significance of bystander effect in GDEPT over the long term in vivo.

We performed experiments using mixtures of yeast cytosine deaminase (yCD) expressing and empty vector (EV) containing cells. First, the bystander effect was assessed in various ratios of colon cancer cell lines RKO with yCD/EV in 2D and 3D culture. Next, tumors raised from RKO with yCD/EV in mice were treated with the prodrug 5-fluorocytosine (5-FC) for 42 days to assess bystander effect in vivo. Cell types constituting relapsed tumors were determined by 5-FC treatment and PCR.

We were able to demonstrate bystander effect in both 2D and 3D. In mice, tumors initially regressed, but they all eventually recurred including those produced from 80% yCD expressing cells. Cells explanted from the recurrent tumors demonstrated that suicide gene expressing cells had been selected against during in vivo treatment with 5-FC.

We conclude that gene therapy of malignant tumors in patients using the yCD/5-FC system will require targeting well over 80% of the malignant cells, and therefore will likely require improved bystander effect or repeated treatment.

Identification of 22 Novel Motifs of the Cell Entry Fusion Glycoprotein B of Oncolytic Herpes Simplex Viruses: Sequence Analysis and Literature Review

Objective: Herpes simplex viruses (HSVs) are widely spread throughout the world, causing infections from oral, and genital mucous membrane ulcerations to severe viral encephalitis. Glycoprotein B (gB) was the first HSV envelope glycoprotein identified to induce cell fusion. This glycoprotein initiates viral entry and thereby determines the infectivity of HSV, as well as oncolytic HSV (oHSV). Clarifying its molecular characterization and enlarging its motif reservoir will help to engineer oHSV and in cancer treatment applications. Only in recent years has the importance of gB been acknowledged in HSV infection and oHSV engineering. Although gB-modified oHSVs have been developed, the detailed molecular biology of gB needs to be illustrated more clearly in order to construct more effective oHSVs.

Method: Here, we performed a systematic comparative sequence analysis of gBs from the 9 HSV-1 and 2 HSV-2 strains, including HSV-1-LXMW, which was isolated by our lab. Online software was implemented to predict gB secondary structure and motifs. Based on extensive literature reviews, a functional analysis of the predicted motifs was performed.

Results: Here, we reported the DNA and predicted amino acid sequences of our recently isolated HSV-1-LXMW and found that the strain was evolutionarily close to HSV-1 strains F, H129, and SC16 based on gB analysis. The 22 novel motifs of HSV gB were identified for the first time. An amino acid sequence alignment of the 11 HSV strains showed that the gB motifs are conserved among HSV strains, suggesting that they are functional in vivo. Additionally, we found that certain amino acids within the 13 motifs out of the 22 were reported to be functional in vivo. Furthermore, the gB mutants and gB-engineered oHSVs were also summarized.

Conclusion: Our identification of the 22 novel motifs shed light on HSV gB biology and provide new options for gB engineering to improve the efficiency and safety of oHSVs.

Measles virus in cancer therapy

Over the last years, the development of viruses to treat cancer patients has re-gained considerable attention. A genetically modified herpesvirus, Talimogene laherparepvec, has already been authorized for the treatment of melanoma patients. Also recombinant measles virus (MeV) is developed as an oncolytic virus. Because of its high genetic flexibility, a number of different MeV strains have been the basis for the generation of targeted, armed, or shielded viruses that are highly specific for a given tumor target, more effective, or protected against serum neutralization. Such MeV have been extensively tested in vitro and in vivo, whereby remarkable oncolytic potency is accompanied by safety also in non-human primates. Therefore, MeV has been introduced into 19 different clinical trials and has reached phase II against two different tumor entities, multiple myeloma and ovarian carcinoma. Remarkably, one patient with advanced stage myeloma experienced long-term remission after treatment, visualizing the potency of this approach.

Oncolytic effects of Hitchner B1 strain of newcastle disease virus against cervical cancer cell proliferation is mediated by the increased expression of cytochrome C, autophagy and apoptotic pathways

Newcastle disease virus (NDV) is a potential oncolytic virus for the cancer treatment due to its ability to replicate in tumor cells. The aim of this study was to evaluate the in vitro anticancer properties of Hitchner B1 (HB1) strain of NDV on TC-1 cell line and underlying molecular mechanisms. The cytolytic effects of oncolytic HB1 strain of NDV was determined by lactate dehydrogenase (LDH) release assay. Apoptosis, intracellular reactive oxygen species (ROS) levels, cleaved caspase-3 and autophagy were evaluated by flow cytometry. Cytochrome-C and survivin protein levels were distinguished by Enzyme-Linked Immunosorbent Assay (ELISA). Our results from LDH method showed that the viability of the TC-1 cell line following HB1 NDV infection was dose-dependent and decreased significantly with increasing the dose of HB1 NDV infection (MOIs: 5, 10, and 15). Other evaluations also revealed that HB1 strain of NDV potentially led to the ROS production, and apoptosis and autophagy induction in TC-1 cell line in a dose-dependent manner. The in vitro experiments also presented that NDV treatment significantly up-regulated the expression of cytochrome-C and down-regulated the expression of survivin, as detected by ELISA assay. Our results confirmed that the HB1 NDV could be introduced as a powerful candidate for the therapy of cervical cancer. However, further examinations are needed to explain the underlying mechanisms of the HB1 NDV against TC-1 cell line and cervical cancer.

A tool with many applications: vesicular stomatitis virus in research and medicine

INTRODUCTION

Vesicular stomatitis virus (VSV) has long been a useful research tool in virology and recently become an essential part of medicinal products. Vesiculovirus research is growing quickly following its adaptation to clinical gene and cell therapy and oncolytic virotherapy.

AREAS COVERED

This article reviews the versatility of VSV as a research tool and biological reagent, its use as a viral and vaccine vector delivering therapeutic and immunogenic transgenes and an oncolytic virus aiding cancer treatment. Challenges such as the immune response against such advanced therapeutic medicinal products and manufacturing constraints are also discussed.

EXPERT OPINION

The field of in vivo gene and cell therapy is advancing rapidly with VSV used in many ways. Comparison of VSV's use as a versatile therapeutic reagent unveils further prospects and problems for each application. Overcoming immunological challenges to aid repeated administration of viral vectors and minimizing harmful host-vector interactions remains one of the major challenges. In the future, exploitation of reverse genetic tools may assist the creation of recombinant viral variants that have improved onco-selectivity and more efficient vaccine vector activity. This will add to the preferential features of VSV as an excellent advanced therapy medicinal product (ATMP) platform.

Development of lipid-like materials for RNA delivery based on intracellular environment-responsive membrane destabilization and spontaneous collapse

Messenger RNA and small interfering RNA are attractive modalities for curing diseases by complementation or knock-down of proteins. For success of these RNAs, a drug delivery system (DDS) is required to control a pharmacokinetics, to enhance cellular uptake, to overcome biological membranes, and to release the cargo into the cytoplasm. Based on past research, developing nanoparticles that are neutrally charged have been the mainstream of their development. Also, the materials are further mounted with pH- and/or reducing environment-responsive units. In this review, we summarize progress made in the molecular design of these materials. We also focus on the importance of the hydrophobic scaffold for tissue/cell targeting, intracellular trafficking, and immune responses. As a practical example, the design concept of the SS-cleavable and pH-activated lipid-like material (ssPalm) and subsequent molecular modification tailored to the RNA-based medical application is discussed.

Resistance to immune checkpoint inhibitors in non-small cell lung cancer: biomarkers and therapeutic strategies

The treatment landscape for patients with advanced non-small cell lung cancer has evolved greatly with the advent of immune checkpoint inhibitors. However, many patients do not derive benefit from checkpoint blockade, developing either primary or secondary resistance, highlighting a need for alternative approaches to modulate immune function. In this review, we highlight the absence of a common definition of primary and secondary resistance and summarize their frequency and clinical characteristics. Furthermore, we provide an overview of the biomarkers and mechanisms of resistance involving the tumor, the tumor microenvironment and the host, and suggest treatment strategies to overcome these mechanisms and improve clinical outcomes.

Cancer immunotherapy: dawn of the death of cancer?

Cancer is one of the proficient evaders of the immune system which claims millions of lives every year. Developing therapeutics against cancer is extremely challenging as cancer involves aberrations in self, most of which are not detected by the immune system. Conventional therapeutics like chemotherapy, radiotherapy are not only toxic but they significantly lower the quality of life. Immunotherapy, which gained momentum in the 20th century, is emerging as one of the alternatives to the conventional therapies and is relatively less harmful but more costly. This review explores the modern advances in an array of such therapies and try to compare them along with a limited analysis of concerns associated with them.

MAP3K7 and CHD1 Are Novel Mediators of Resistance to Oncolytic Vesicular Stomatitis Virus in Prostate Cancer Cells

A key principle of oncolytic viral therapy is that many cancers develop defects in their antiviral responses, making them more susceptible to virus infection. However, some cancers display resistance to viral infection. Many of these resistant cancers constitutively express interferon-stimulated genes (ISGs). The goal of these experiments was to determine the role of two tumor suppressor genes, MAP3K7 and CHD1, in viral resistance and ISG expression in PC3 prostate cancer cells resistant to oncolytic vesicular stomatitis virus (VSV). MAP3K7 and CHD1 are often co-deleted in aggressive prostate cancers. Silencing expression of MAP3K7 and CHD1 in PC3 cells increased susceptibility to the matrix (M) gene mutant M51R-VSV, as shown by increased expression of viral genes, increased yield of progeny virus, and reduction of tumor growth in nude mice. Silencing MAP3K7 alone had a greater effect on virus susceptibility than did silencing CHD1. Silencing MAP3K7 and CHD1 decreased constitutive expression of ISG mRNAs and proteins, whereas silencing MAP3K7 alone decreased expression of ISG proteins, but actually increased expression of ISG mRNAs. These results suggest a role for the protein product of MAP3K7, transforming growth factor β-activated kinase 1 (TAK1), in regulating translation of ISG mRNAs and a role of CHD1 in maintaining the transcription of ISGs.

Recombinant Myxoma Virus Expressing Walleye Dermal Sarcoma Virus orfC Is Attenuated in Rabbits

The poxvirus, myxoma virus (MYXV) has shown efficacy as an oncolytic virus (OV) in some cancer models. However, MYXV replication within murine cancer models and spontaneous canine sarcomas is short-lived. In mice, successful treatment of tumors requires frequent injections with MYXV. We hypothesize that treatment of cancer with a recombinant MYXV that promotes apoptosis could improve the efficacy of MYXV. The orfC gene of walleye dermal sarcoma virus (WDSV), which induces apoptosis, was recombined into the MYXV genome (MYXVorfC). A marked increase in apoptosis was observed in cells infected with MYXVorfC. To ensure that expression of WDSV orfC by MYXV does not potentiate the pathogenesis of MYXV, we evaluated the effects of MYXVorfC inoculation in the only known host of MYXV, New Zealand white rabbits. Virus dissemination in rabbit tissues was similar for MYXVorfC and MYXV. Virus titers recovered from tissues were lower in MYXVorfC-infected rabbits as compared to MYXV-infected rabbits. Importantly, rabbits infected with MYXVorfC had a delayed onset of clinical signs and a longer median survival time than rabbits infected with MYXV. This study indicates that MYXVorfC is attenuated and suggests that MYXVorfC will be safe to use as an OV therapy in future studies.

Integrative functional genomics decodes herpes simplex virus 1

The predicted 80 open reading frames (ORFs) of herpes simplex virus 1 (HSV-1) have been intensively studied for decades. Here, we unravel the complete viral transcriptome and translatome during lytic infection with base-pair resolution by computational integration of multi-omics data. We identify a total of 201 transcripts and 284 ORFs including all known and 46 novel large ORFs. This includes a so far unknown ORF in the locus deleted in the FDA-approved oncolytic virus Imlygic. Multiple transcript isoforms expressed from individual gene loci explain translation of the vast majority of ORFs as well as N-terminal extensions (NTEs) and truncations. We show that NTEs with non-canonical start codons govern the subcellular protein localization and packaging of key viral regulators and structural proteins. We extend the current nomenclature to include all viral gene products and provide a genome browser that visualizes all the obtained data from whole genome to single-nucleotide resolution.

Delivery of genome editing tools: A promising strategy for HPV-related cervical malignancy therapy

INTRODUCTION

Persistent high-risk human papillomavirus infection is the main cause of various types of cancer especially cervical cancer. The E6 and E7 oncoproteins of HPV play critical roles in promoting carcinogenesis and cancer cell growth. As a result, E6 and E7 oncogenes are considered as promising therapeutic targets for cervical cancer. Recently, the development of genome-editing technologies including transcription activator-like effector nucleases (TALEN), meganucleases (MNs), zinc finger nucleases (ZFN), and more importantly clustered regularly interspaced short palindromic repeat-CRISPR-associated protein (CRISPR-Cas) has sparked a revolution in the cervical cancer-targeted therapy. However, due to immunogenicity, off-target effect, renal clearance, guide RNA (gRNA) nuclease degradation, and difficult direct transportation into the cytoplasm and nucleus, the safe and effective delivery is considered as the Achilles' heel of this robust strategy.

AREAS COVERED

In this review, we discuss cutting-edge available strategies for in vivo delivery of genome-editing technologies for HPV-induced cervical cancer therapy. Moreover, the combination of genome-editing tools and other therapies has been fully discussed.

EXPERT OPINION

The combination of nanoparticle-based delivery systems and genome-editing tools is a promising powerful strategy for cervical cancer therapy. The most significant limitations of this strategy that need to be focused on are low efficiency and off-target events.

How Computational Chemistry and Drug Delivery Techniques Can Support the Development of New Anticancer Drugs

The early and late development of new anticancer drugs, small molecules or peptides can be slowed down by some issues such as poor selectivity for the target or poor ADME properties. Computer-aided drug design (CADD) and target drug delivery (TDD) techniques, although apparently far from each other, are two research fields that can give a significant contribution to overcome these problems. Their combination may provide mechanistic understanding resulting in a synergy that makes possible the rational design of novel anticancer based therapies. Herein, we aim to discuss selected applications, some also from our research experience, in the fields of anticancer small organic drugs and peptides.

Next-generation stem cells - ushering in a new era of cell-based therapies

Naturally occurring stem cells isolated from humans have been used therapeutically for decades. This has primarily involved the transplantation of primary cells such as haematopoietic and mesenchymal stem cells and, more recently, derivatives of pluripotent stem cells. However, the advent of cell-engineering approaches is ushering in a new generation of stem cell-based therapies, greatly expanding their therapeutic utility. These next-generation stem cells are being used as 'Trojan horses' to improve the delivery of drugs and oncolytic viruses to intractable tumours and are also being engineered with angiogenic, neurotrophic and anti-inflammatory molecules to accelerate the repair of injured or diseased tissues. Moreover, gene therapy and gene editing technologies are being used to create stem cell derivatives with improved functionality, specificity and responsiveness compared with their natural counterparts. Here, we review these engineering approaches and areas in which they will help broaden the utility and clinical applicability of stem cells.

Protein Expression in Metastatic Melanoma and the Link to Disease Presentation in a Range of Tumor Phenotypes

Malignant melanoma is among the most aggressive skin cancers and it has among the highest metastatic potentials. Although surgery to remove the primary tumor is the gold standard treatment, once melanoma progresses and metastasizes to the lymph nodes and distal organs, i.e., metastatic melanoma (MM), the usual outcome is decreased survival. To improve survival rates and life span, advanced treatments have focused on the success of targeted therapies in the MAPK pathway that are based on BRAF (BRAF V600E) and MEK. The majority of patients with tumors that have higher expression of BRAF V600E show poorer prognosis than patients with a lower level of the mutated protein. Based on the molecular basis of melanoma, these findings are supported by distinct tumor phenotypes determined from differences in tumor heterogeneity and protein expression profiles. With these aspects in mind, continued challenges are to: (1) deconvolute the complexity and heterogeneity of MM; (2) identify the signaling pathways involved; and (3) determine protein expression to develop targeted therapies. Here, we provide an overview of the results from protein expression in MM and the link to disease presentation in a variety of tumor phenotypes and how these will overcome the challenges of clinical problems and suggest new promising approaches in metastatic melanoma and cancer therapy.

Deciphering the Immunomodulatory Capacity of Oncolytic Vaccinia Virus to Enhance the Immune Response to Breast Cancer

Vaccinia virus (VACV) is a double-stranded DNA virus that devotes a large portion of its 200 kbp genome to suppressing and manipulating the immune response of its host. Here, we investigated how targeted removal of immunomodulatory genes from the VACV genome impacted immune cells in the tumor microenvironment with the intention of improving the therapeutic efficacy of VACV in breast cancer. We performed a head-to-head comparison of six mutant oncolytic VACVs, each harboring deletions in genes that modulate different cellular pathways, such as nucleotide metabolism, apoptosis, inflammation, and chemokine and interferon signaling. We found that even minor changes to the VACV genome can impact the immune cell compartment in the tumor microenvironment. Viral genome modifications had the capacity to alter lymphocytic and myeloid cell compositions in tumors and spleens, PD-1 expression, and the percentages of virus-targeted and tumor-targeted CD8⁺ T cells. We observed that while some gene deletions improved responses in the nonimmunogenic 4T1 tumor model, very little therapeutic improvement was seen in the immunogenic HER2/neu TuBo model with the various genome modifications. We observed that the most promising candidate genes for deletion were those that interfere with interferon signaling. Collectively, this research helped focus attention on the pathways that modulate the immune response in the context of VACV oncolytic virotherapy. They also suggest that the greatest benefits to be obtained with these treatments may not always be seen in "hot tumors."

Embelin Promotes Oncolytic Vaccinia Virus-Mediated Antitumor Immunity Through Disruption of IL-6/STAT3 Signaling in Lymphoma

Objective

Oncolytic virotherapy is a promising alternative to conventional treatment, yet limited viral replication and immune-negative feedback are the major hurdles to effective viro-immunotherapy.

Methods

In this study, we found that use of an adjuvant of embelin, a small molecular inhibitor of XIAP, increased the replication of oncolytic vaccinia virus (OVV) by mitigating antiviral innate immunity. Moreover, embelin suppresses constitutive STAT3 phosphorylation and mitigates OVV-induced activation of STAT3 in lymphoma. In the subcutaneous lymphoma model, embelin significantly enhanced the therapeutic efficacy of OVV and prolonged the survival. In addition, embelin significantly increased the OVV-induced infiltration of T cells and NK cells and decreased the number of OVV-induced myeloid-derived suppressor cells (MDSCs) in the tumor microenvironment.

Results

Our results explored the ability of OVV and embelin in combination to enhance lymphoma cell lysis, revealing a beneficial combinatorial effect wherein both lymphoma cell lysis and OVV replication were enhanced both in vitro and in an in vivo murine model system.

Conclusion

Our findings indicate the utility of embelin as an adjuvant for oncolytic viro-immunotherapy.

Insights Into Lung Cancer Immune-Based Biology, Prevention, and Treatment

Lung cancer is the number one cause of cancer-related deaths. The malignancy is characterized by dismal prognosis and poor clinical outcome mostly due to advanced-stage at diagnosis, thereby inflicting a heavy burden on public health worldwide. Recent breakthroughs in immunotherapy have greatly benefited a subset of lung cancer patients, and more importantly, they are undauntedly bringing forth a paradigm shift in the drugs approved for cancer treatment, by introducing "tumor-type agnostic therapies". Yet, and to fulfill immunotherapy's potential of personalized cancer treatment, demarcating the immune and genomic landscape of cancers at their earliest possible stages will be crucial to identify ideal targets for early treatment and to predict how a particular patient will fare with immunotherapy. Recent genomic surveys of premalignant lung cancer have shed light on early alterations in the evolution of lung cancer. More recently, the advent of immunogenomic technologies has provided prodigious opportunities to study the multidimensional landscape of lung tumors as well as their microenvironment at the molecular, genomic, and cellular resolution. In this review, we will summarize the current state of immune-based therapies for cancer, with a focus on lung malignancy, and highlight learning outcomes from clinical and preclinical studies investigating the naïve immune biology of lung cancer. The review also collates immunogenomic-based evidence from seminal reports which collectively warrant future investigations of premalignancy, the tumor-adjacent normal-appearing lung tissue, pulmonary inflammatory conditions such as chronic obstructive pulmonary disease, as well as systemic microbiome imbalance. Such future directions enable novel insights into the evolution of lung cancers and, thus, can provide a low-hanging fruit of targets for early immune-based treatment of this fatal malignancy.

Review of talimogene laherparepvec: A first-in-class oncolytic viral treatment of advanced melanoma

Talimogene laherparepvec (T-VEC) is an oncolytic virus based on herpes simplex virus type 1 approved for intralesional treatment of advanced melanoma. In this article, we review the clinical literature on T-VEC for advanced melanoma and provide a practical approach to using T-VEC in the dermatologic surgery and oncology clinic. PubMed was used to conduct a systematic literature review of articles describing the structure, basic science, and clinical and therapeutic properties of T-VEC. The national clinical trials database was also searched for T-VEC clinical trials. Phase I to III clinical trials and early real-world experience have shown the efficacy of T-VEC in advanced melanoma as single or combination therapy with tolerable adverse effects. We conclude that with a standardized clinical approach and training, dermatologists can pave the way in using T-VEC and future oncolytic virus therapies in appropriate clinical scenarios.

Emergence in protein derived nanomedicine as anticancer therapeutics: More than a tour de force

Cancer has thwarted as a major health problem affecting the global population. With an alarming increase in the patient population suffering from diverse varieties of cancers, the global demographic data predicts sharp escalation in the number of cancer patients. This can be expected to reach 420 million cases by 2025. Among the diverse types of cancers, the most frequently diagnosed cancers are the breast, colorectal, prostate and lung cancer. From years, conventional treatment approaches like surgery, chemotherapy and radiation therapy have been practiced. In the past few years, increasing research on molecular level diagnosis and treatment of cancers have significantly changed the realm of cancer treatment. Lately, uses of advanced chemotherapy and immunotherapy like treatments have gained significant progress in the cancer therapy, but these approaches have several limitations on their safety and toxicity. This has generated lot of momentum for the evolution of new drug delivery approaches for the effective delivery of anticancer therapeutics, which may improve the pharmacokinetic and pharmacodynamic effect of the drugs along with significant reduction in the side effects. In this regard, the protein-based nano-medicines have gained wider attention in the management of cancer. Proteins are organic macromolecules essential, for life and have quite well explored in developing the nano-carriers. Furthermore, it provides passive or active tumour cell targeted delivery, by using protein based nanovesicles or virus like structures, antibody drug conjugates, viral particles, etc. Moreover, by utilizing various formulation strategies, both the animal and plant derived proteins can be converted to produce self-assembled virus like nano-metric structures with high efficiency in targeting the metastatic cancer cells. Therefore, the present review extensively discusses the applications of protein-based nano-medicine with special emphasis on intracellular delivery/drug targeting ability for anticancer drugs.

Point Mutations in Retargeted gD Eliminate the Sensitivity of EGFR/EGFRvIII-Targeted HSV to Key Neutralizing Antibodies

Effective oncolytic virotherapy may require systemic delivery, tumor targeting, and resistance to virus-neutralizing (VN) antibodies. Since herpes simplex virus (HSV) glycoprotein D (gD) is the viral attachment/entry protein and predominant VN target, we examined the impact of gD retargeting alone and in combination with alterations in dominant VN epitopes on virus susceptibility to VN antibodies. We compared the binding of a panel of anti-gD monoclonal antibodies (mAbs) that mimic antibody specificities in human HSV-immune sera to the purified ectodomains of wild-type and retargeted gD, revealing the retention of two prominent epitopes. Substitution of a key residue in each epitope, separately and together, revealed that both substitutions (1) blocked retargeted gD recognition by mAbs to the respective epitopes, and, in combination, caused a global reduction in mAb binding; (2) protected against fusion inhibition by VN mAbs reactive with each epitope in virus-free cell-cell fusion assays; and (3) increased the resistance of retargeted HSV-1 to these VN mAbs. Although the combined modifications of retargeted gD allowed bona fide retargeting, incorporation into virions was partially compromised. Our results indicate that stacking of epitope mutations can additively block retargeted gD recognition by VN antibodies but also that improvements in gD incorporation into virus particles may be required.

Oncolytic adenovirus targeting TGF-β enhances anti-tumor responses of mesothelin-targeted chimeric antigen receptor T cell therapy against breast cancer

Chimeric antigen receptor (CAR)-modified T cell therapy evokes only modest antitumor responses in solid tumors. Meso-CAR-T cells are CAR-T cells targeted mesothelin, which are over-expressed in tumor tissues of breast cancer patients. To improve the therapeutic effects, we combined it with rAd.sT, a transforming growth factor β signaling-targeted oncolytic adenovirus, to therapy breast cancer. In subcutaneous MDA-MB-231 xenograft of NSG mice, both rAd.sT and meso-CAR-T inhibited tumor growth, however combination therapy produced stronger inhibitory effects. Interestingly, rAd.sT reduced tumor burden at initial stage following vector treatments, while meso-CAR-T cells decreased tumor burden at a later stage. Moreover, meso-CAR-T could target tumor microenvironments, and combination therapy could enhance cytokines production, such as interleukin (IL)-6 and IL-12 in tumor microenvironment. In conclusion, combination of rAd.sT with meso-CAR-T produced much more impressive antitumor responses to breast cancer and its metastasis, which could be developed as a promising therapeutic strategy.

Engineering HSV-1 Vectors for Gene Therapy

Virus vectors have been employed as gene transfer vehicles for various preclinical and clinical gene therapy applications and with the approval of Glybera (Alipogene tiparvovec) as the first gene therapy product as a standard medical treatment (Yla-Herttuala, Mol Ther 20:1831-1832, 2013), gene therapy has reached the status of being a part of standard patient care. Replication-competent herpes simplex virus (HSV) vectors that replicate specifically in actively dividing tumor cells have been used in Phase I-III human trials in patients with glioblastoma multiforme (GBM), a fatal form of brain cancer, and in malignant melanoma. In fact, Imlygic^® (T-VEC, Talimogene laherparepvec, formerly known as OncoVex GM-CSF), displayed efficacy in a recent Phase-III trial when compared to standard GM-CSF treatment alone (Andtbacka et al., J Clin Oncol 31:sLBA9008, 2013), and has since become the first FDA-approved viral gene therapy product used in standard patient care (October 2015) (Pol et al., Oncoimmunology 5:e1115641, 2016). Moreover, increased efficacy was observed when Imlygic^® was combined with checkpoint inhibitory antibodies as a frontline therapy for malignant melanoma (Ribas et al., Cell 170:1109-1119.e1110, 2017; Dummer et al., Cancer Immunol Immunother 66:683-695, 2017). In addition to the replication-competent oncolytic HSV vectors like T-VEC, replication-defective HSV vectors have been employed in Phase I-II human trials and have been explored as delivery vehicles for disorders such as pain, neuropathy and other neurodegenerative conditions. Research during the last decade on the development of HSV vectors has resulted in the engineering of recombinant vectors that are completely replication defective, nontoxic, and capable of long-term transgene expression in neurons. This chapter describes methods for the construction of recombinant genomic HSV vectors based on the HSV-1 replication-defective vector backbones, steps in their purification, and their small-scale production for use in cell culture experiments as well as preclinical animal studies.

Mathematical Modeling of Oncolytic Virotherapy

Mathematical modeling in biology has a long history as it allows the analysis and simulation of complex dynamic biological systems at little cost. A mathematical model trained on experimental or clinical data can be used to generate and evaluate hypotheses, to ask "what if" questions, and to perform in silico experiments to guide future experimentation and validation. Such models may help identify and provide insights into the mechanisms that drive changes in dynamic systems. While a mathematical model may never replace actual experiments, it can synergize with experiments to save time and resources by identifying experimental conditions that are unlikely to yield favorable outcomes, and by using optimization principles to identify experiments that are most likely to be successful. Over the past decade, numerous models have also been developed for oncolytic virotherapy, ranging from merely theoretic frameworks to fully integrated studies that utilize experimental data to generate actionable hypotheses. Here we describe how to develop such models for specific oncolytic virotherapy experimental setups, and which questions can and cannot be answered using integrated mathematical oncology.

Radiotherapy as a Backbone for Novel Concepts in Cancer Immunotherapy

Radiation-induced immunogenic cell death has been described to contribute to the efficacy of external beam radiotherapy in local treatment of solid tumors. It is well established that radiation therapy can induce immunogenic cell death in cancer cells under certain conditions. Initial clinical studies combining radiotherapy with immunotherapies suggest a synergistic potential of this approach. Improving our understanding of how radiation reconditions the tumor immune microenvironment should pave the way for designing rational and robust combinations with immunotherapeutic drugs that enhance both local and systemic anti-cancer immune effects. In this review, we summarize irradiation-induced types of immunogenic cell death and their effects on the tumor microenvironment. We discuss preclinical insights on mechanisms and benefits of combining radiotherapy with immunotherapy, focusing on immune checkpoint inhibitors. In addition, we elaborate how these observations were translated into clinical studies and which parameters may be optimized to achieve best results in future clinical trials.

Syncytia Formation in Oncolytic Virotherapy

Oncolytic virotherapy uses replication-competent virus as a means of treating cancer. Whereas this field has shown great promise as a viable treatment method, the limited spread of these viruses throughout the tumor microenvironment remains a major challenge. To overcome this issue, researchers have begun looking at syncytia formation as a novel method of increasing viral spread. Several naturally occurring fusogenic viruses have been shown to possess strong oncolytic potential and have since been studied to gain insight into how this process benefits oncolytic virotherapy. Whereas these naturally fusogenic viruses have been beneficial, there are still challenges associated with their regular use. Because of this, engineered/recombinant fusogenic viruses have also been created that enhance nonfusogenic oncolytic viruses with the beneficial property of syncytia formation. The purpose of this review is to examine the existing body of literature on syncytia formation in oncolytics and offer direction for potential future studies.

Combination Therapy with Reovirus and ATM Inhibitor Enhances Cell Death and Virus Replication in Canine Melanoma

Oncolytic virotherapy using reovirus is a promising new anti-cancer treatment with potential for use in humans and dogs. Because reovirus monotherapy shows limited efficacy in human and canine cancer patients, the clinical development of a combination therapy is necessary. To identify candidate components of such a combination, we screened a 285-compound drug library for those that enhanced reovirus cytotoxicity in a canine melanoma cell line. Here, we show that exposure to an inhibitor of the ataxia telangiectasia mutated protein (ATM) enhances the oncolytic potential of reovirus in five of six tested canine melanoma cell lines. Specifically, the ATM inhibitor potentiated reovirus replication in cancer cells along with promoting the lysosomal activity, resulting in an increased proportion of caspase-dependent apoptosis and cell cycle arrest at G2/M compared to those observed with reovirus alone. Overall, our study suggests that the combination of reovirus and the ATM inhibitor may be an attractive option in cancer therapy.

Impact of Induced Syncytia Formation on the Oncolytic Potential of Myxoma Virus

Introduction

Cancer has become one of the most critical health issues of modern times. To overcome the ineffectiveness of current treatment options, research is being done to explore new therapeutic modalities. One such novel treatment is oncolytic virotherapy (OV) which uses tumor tropic viruses to specifically target and kill malignant cells. While OV has shown significant promise in recent clinical trials, the therapeutic use of viruses poses a number of unique challenges. In particular, obtaining effective viral spread throughout the tumor microenvironment remains problematic. Previous work has suggested this can be overcome by forcing oncolytic viruses to induce syncytia formation.

Methods

In the current work, we generated a series of recombinant myxoma viruses expressing exogenous fusion proteins from other viral genomes and examined their therapeutic potential in vitro and in vivo.

Results

Similar to previous studies, we observed that the expression of these fusion proteins during myxoma infection induced the formation of multinucleated syncytia which increased viral spread and lytic potential compared to non-fusogenic controls. Contrary to expectations, however, the treatment of established tumors with these viruses resulted in decreased therapeutic efficacy which corresponded with reduced viral persistence.

Discussion

These findings indicate that enhanced viral spread caused by syncytia formation can actually reduce the efficacy of OV and supports a number of previous works suggesting that the in vitro properties of viruses frequently fail to predict their in vivo efficacy.

Targeting aerobic glycolysis by dichloroacetate improves Newcastle disease virus-mediated viro-immunotherapy in hepatocellular carcinoma

BACKGROUND

Oncolytic viro-immunotherapy holds promise for cancer treatment. While immune activation can be robustly triggered by oncolytic viruses, negative feedback is often upregulated in the tumour microenvironment (TME). Lactate accumulation, signal transducer and activator of transcription 3 (STAT3) activation, indoleamine 2,3-dioxygenase 1 (IDO1) expression, and myeloid-derived suppressor cell (MDSC) infiltration coordinate to shape the immunosuppressive TME.

METHODS

Representative hepatocellular carcinoma (HCC) cell lines and HCC-bearing mice were treated with oncolytic Newcastle disease virus (NDV), alone or in combination with dichloroacetate (DCA, a pyruvate dehydrogenase kinase (PDK) inhibitor).

RESULTS

We found that infection with oncolytic NDV led to significant induction of the aforementioned suppressive factors. Interestingly, DCA significantly reduced lactate release, STAT3 activation, IDO1 upregulation, and MDSC infiltration in NDV-treated HCC. Consequently, DCA significantly enhanced the antitumour immune responses, leading to improved antitumour efficacy and prolonged survival in mouse models of ascitic and subcutaneous HCC. Furthermore, DCA increased NDV replication in a PDK-1-dependent manner in HCC.

CONCLUSIONS

Targeting aerobic glycolysis by DCA improves NDV-mediated viro-immunotherapy in HCC by mitigating immune negative feedback and promoting viral replication. These findings provide a rationale for targeting reprogrammed metabolism together with oncolytic virus-mediated viro-immunotherapy for HCC treatment.

The potential of the combined use of targeted type I interferon pathway inhibitors and oncolytic viruses to treat sarcomas

Replicating oncolytic viruses (OVs) are appealing, new, FDA-approved, therapeutic options for humans with head and neck cancers and melanomas. These treatments are not yet available for veterinary patients, but recent clinical trials have shown several OVs to be safe in dogs and cats. Specific viruses being used to treat sarcomas in dogs include modified canine adenovirus 2, myxoma virus, vesicular stomatitis virus and reovirus. In cats with vaccine-associated sarcomas, poxviruses have been injected postoperatively and a reduced rate of tumour recurrence was documented. To date, the response rates of canine and feline patients to OV therapy have been variable (as they are in people). Optimal methods of OV administration and dosing schedules continue to be evaluated. One way to improve outcomes of OV therapy in veterinary patients may be to use OVs in combination with other immunomodulatory therapies. This review discusses the potential utility of concurrent therapy with an OV and an inhibitor of the type I interferon pathway.

Immunological Effects and Viral Gene Expression Determine the Efficacy of Oncolytic Measles Vaccines Encoding IL-12 or IL-15 Agonists

Tumor-targeted immunomodulation using oncolytic viral vectors is currently being investigated as a promising strategy in cancer therapy. In a previous study, we showed that a measles virus Schwarz vaccine strain (MeVac) vector encoding an interleukin-12 fusion protein (FmIL-12) is an effective immunotherapy in the MC38cea murine colon adenocarcinoma model. We hypothesized that MeVac encoding interleukin-15 may mediate enhanced T and NK cell responses and thus increase the therapeutic efficacy, especially in NK cell-controlled tumors. Therefore, we generated MeVac vectors encoding an interleukin-15 superagonist, FmIL-15. Replication and oncolytic capacity, transgene expression, and functionality of MeVac FmIL-15 vectors were validated in vitro. Effects on the tumor immune landscape and therapeutic efficacy of both FmIL-12 and FmIL-15 vectors were studied in the MC38cea and B16hCD46 tumor models. Treatment with MeVac FmIL-15 increased T and NK cell infiltration in both models. However, MeVac FmIL-12 showed more robust viral gene expression and immune activation, resulting in superior anti-tumor efficacy. Based on these results, MeVac encoding a human IL-12 fusion protein was developed for future clinical translation.

Clinical-Grade Oncolytic Adenovirus Purification Using Polysorbate 20 as an Alternative for Cell Lysis

Introduction:

Oncolytic virus therapy is currently considered as a promising therapeutic ap-proach for cancer treatment. Adenovirus is well-known and extensively characterized as an oncolytic agent. The increasing number of clinical trials using this virus generates the demand for the development of a well-established purification approach. Triton X-100 is commonly used in cell lysis buffer prepara-tions. The addition of this surfactant in the list of substances with the very high concern of the Registra-tion, Evaluation, Authorization and Restriction of Chemicals (REACH) regulation promoted the research for effective alternatives.

Methods:

In this work, a purification strategy for oncolytic adenovirus compatible with phase I clinical trials, using an approved surfactant – Polysorbate 20 was developed. The proposed downstream train, composed by clarification, concentration using tangential flow filtration, intermediate purification with anion exchange chromatography, followed by a second concentration and a final polishing step was evaluated for both Triton X-100 and Polysorbate 20 processes. The impact of cell lysis with Polysorb-ate20 and Triton X-100 for each downstream step was evaluated in terms of product recovery and impu-rities removal. Overall, 61 ± 4% of infectious viral particles were recovered. Depletion of host cell pro-teins and ds-DNA was 99.9% and 97.1%, respectively.

Results & Conclusion:

The results indicated that Polysorbate 20 can be used as a replacement for Triton X-100 during cell lysis with no impact on product recovery, potency, and purity. Moreover, the devel-oped process is scalable and able to provide a highly purified product to be used in phase I and II clinical trials.

Oncolytic activity of HF10 in head and neck squamous cell carcinomas

Recent developments in therapeutic strategies have improved the prognosis of head and neck squamous cell carcinoma (HNSCC). Nevertheless, 5-year survival rate remains only 40%, necessitating new therapeutic agents. Oncolytic virotherapy entails use of replication-competent viruses to selectively kill cancer cells. We aimed to explore the potential of HF10 as an oncolytic virus against human or mouse HNSCC cell lines, and primary-cultured HNSCC cells. HF10 replicated well in all the HNSCC cells, in which it induced cytopathic effects and cell killing. Next, we investigated the oncolytic effects of HF10 in ear tumor models with human or mouse tumor cells. We detected HF10-infected cells within the ear tumors based on their expression of green fluorescent protein. HF10 injection suppressed ear tumor growth and prolonged overall survival. In the syngeneic model, HF10 infection induced tumor necrosis with infiltration of CD8-positive cells. Moreover, the splenocytes of HF10-treated mice released antitumor cytokines, IL-2, IL-12, IFN-alpha, IFN-beta, IFN-gamma, and TNF-alpha, after stimulation with tumor cells in vitro. The HF10-treated mice that survived their original tumor burdens rejected tumor cells upon re-challenge. These results suggested that HF10 killed HNSCC cells and induced antitumoral immunity, thereby establishing it as a promising agent for the treatment of HNSCC patients.

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.

Bugs as Cancer Drugs: Challenges and Opportunities

The first nonsurgical cancer therapy was bacterial therapy introduced in 1891 to treat solid tumors. Because in many cases it was harmful and ineffective, and with the emergence of radiotherapy and chemotherapy, bacterial therapy was discontinued. Motivated by the need to improve targeting of solid tumors and in light of recent progress made in developing microbial therapies, the National Cancer Institute has for the first time issued funding opportunities to stimulate research on bacterium-based cancer therapies for conditions under which current cancer therapies are inadequate.

Role of cell surface proteoglycans in cancer immunotherapy

Over the past few decades, understanding how tumor cells evade the immune system and their communication with their tumor microenvironment, has been the subject of intense investigation, with the aim of developing new cancer immunotherapies. The current therapies against cancer such as monoclonal antibodies against checkpoint inhibitors, adoptive T-cell transfer, cytokines, vaccines, and oncolytic viruses have managed to improve the clinical outcome of the patients. However, in some tumor entities, the response is limited and could benefit from the identification of novel therapeutic targets. It is known that tumor-extracellular matrix interplay and matrix remodeling are necessary for anti-tumor and pro-tumoral immune responses. Proteoglycans are dominant components of the extracellular matrix and are a highly heterogeneous group of proteins characterized by the covalent attachment of a specific linear carbohydrate chain of the glycosaminoglycan type. At cell surfaces, these molecules modulate the expression and activity of cytokines, chemokines, growth factors, adhesion molecules, and function as signaling co-receptors. By these mechanisms, proteoglycans influence the behavior of cancer cells and their microenvironment during the progression of solid tumors and hematopoietic malignancies. In this review, we discuss why cell surface proteoglycans are attractive pharmacological targets in cancer, and we present current and recent developments in cancer immunology and immunotherapy utilizing proteoglycan-targeted strategies.

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.