Reciprocal cellular cross-talk within the tumor microenvironment promotes oncolytic virus activity. Nat Med. 2015;21:530-536. [PMID: 25894825 DOI: 10.1038/nm.3848]

Tuning cellular metabolism for cancer virotherapy

Oncolytic viruses (OVs) represent an emerging immunotherapeutic strategy owing to their capacity for direct tumor lysis and induction of antitumor immunity. However, hurdles like transient persistence and moderate efficacy necessitate innovative approaches. Metabolic remodeling has recently gained prominence as a strategic intervention, wherein OVs or combination regimens could reprogram tumor and immune cell metabolism to enhance viral replication and oncolysis. In this review, we summarize recent advances in strategic reprogramming of tumor and immune cell metabolism to enhance OV-based immunotherapies. Specific tactics include engineering viruses to target glycolytic, glutaminolytic, and nucleotide synthesis pathways in cancer cells, boosting viral replication and tumor cell death. Additionally, rewiring T cell and NK cell metabolism of lipids, amino acids, and carbohydrates shows promise to enhance antitumor effects. Further insights are discussed to pave the way for the clinical implementation of metabolically enhanced oncolytic platforms, including balancing metabolic modulation to limit antiviral responses while promoting viral persistence and tumor clearance.

Advances in cell-based delivery of oncolytic viruses as therapy for lung cancer

Lung cancer's intractability is enhanced by its frequent resistance to (chemo)therapy and often high relapse rates that make it the leading cause of cancer death worldwide. Improvement of therapy efficacy is a crucial issue that might lead to a significant advance in the treatment of lung cancer. Oncolytic viruses are desirable combination partners in the developing field of cancer immunotherapy due to their direct cytotoxic effects and ability to elicit an immune response. Systemic oncolytic virus administration through intravenous injection should ideally lead to the highest efficacy in oncolytic activity. However, this is often hampered by the prevalence of host-specific, anti-viral immune responses. One way to achieve more efficient systemic oncolytic virus delivery is through better protection against neutralization by several components of the host immune system. Carrier cells, which can even have innate tumor tropism, have shown their appropriateness as effective vehicles for systemic oncolytic virus infection through circumventing restrictive features of the immune system and can warrant oncolytic virus delivery to tumors. In this overview, we summarize promising results from studies in which carrier cells have shown their usefulness for improved systemic oncolytic virus delivery and better oncolytic virus therapy against lung cancer.

Combination of Oncolytic Virotherapy with Different Antitumor Approaches against Glioblastoma

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

Cancer immunotherapy with enveloped self-amplifying mRNA CARG-2020 that modulates IL-12, IL-17 and PD-L1 pathways to prevent tumor recurrence

Targeting multiple immune mechanisms may overcome therapy resistance and further improve cancer immunotherapy for humans. Here, we describe the application of virus-like vesicles (VLV) for delivery of three immunomodulators alone and in combination, as a promising approach for cancer immunotherapy. VLV vectors were designed to deliver single chain interleukin (IL)-12, short-hairpin RNA (shRNA) targeting programmed death ligand 1 (PD-L1), and a dominant-negative form of IL-17 receptor A (dn-IL17RA) as a single payload or as a combination payload. Intralesional delivery of the VLV vector expressing IL-12 alone, as well as the trivalent vector (designated CARG-2020) eradicated large established tumors. However, only CARG-2020 prevented tumor recurrence and provided long-term survival benefit to the tumor-bearing mice, indicating a benefit of the combined immunomodulation. The abscopal effects of CARG-2020 on the non-injected contralateral tumors, as well as protection from the tumor cell re-challenge, suggest immune-mediated mechanism of protection and establishment of immunological memory. Mechanistically, CARG-2020 potently activates Th1 immune mechanisms and inhibits expression of genes related to T cell exhaustion and cancer-promoting inflammation. The ability of CARG-2020 to prevent tumor recurrence and to provide survival benefit makes it a promising candidate for its development for human cancer immunotherapy.

Oncolytic virotherapy in cancer treatment: challenges and optimization prospects

Oncolytic viruses (OVs) are emerging cancer therapeutics that offer a multifaceted therapeutic platform for the benefits of replicating and lysing tumor cells, being engineered to express transgenes, modulating the tumor microenvironment (TME), and having a tolerable safety profile that does not overlap with other cancer therapeutics. The mechanism of OVs combined with other antitumor agents is based on immune-mediated attack resistance and might benefit patients who fail to achieve durable responses after immune checkpoint inhibitor (ICI) treatment. In this Review, we summarize data on the OV mechanism and limitations of monotherapy, which are currently in the process of combination partner development, especially with ICIs. We discuss some of the hurdles that have limited the preclinical and clinical development of OVs. We also describe the available data and provide guidance for optimizing OVs in clinical practice, as well as a summary of approved and promising novel OVs with clinical indications.

Immunological Assessment of Recent Immunotherapy for Colorectal Cancer

Colorectal cancer (CRC) is the third most prevalent malignancy with increased incidence and mortality rates worldwide. Traditional treatment approaches have attempted to efficiently target CRC; however, they have failed in most cases, owing to the cytotoxicity and non-specificity of these therapies. Therefore, it is essential to develop an effective alternative therapy to improve the clinical outcomes in heterogeneous CRC cases. Immunotherapy has transformed cancer treatment with remarkable efficacy and overcomes the limitations of traditional treatments. With an understanding of the cancer-immunity cycle and tumor microenvironment evolution, current immunotherapy approaches have elicited enhanced antitumor immune responses. In this comprehensive review, we outline the latest advances in immunotherapy targeting CRC and provide insights into antitumor immune responses reported in landmark clinical studies. We focused on highlighting the combination approaches that synergistically induce immune responses and eliminate immunosuppression. This review aimed to understand the limitations and potential of recent immunotherapy clinical studies conducted in the last five years (2019-2023) and to transform this knowledge into a rational design of clinical trials intended for effective antitumor immune responses in CRC.

An oncolytic virus-delivered TGFβ inhibitor overcomes the immunosuppressive tumor microenvironment

While checkpoint blockade immunotherapies have widespread success, they rely on a responsive immune infiltrate; as such, treatments enhancing immune infiltration and preventing immunosuppression are of critical need. We previously generated αPD-1 resistant variants of the murine HNSCC model MEER. While entirely αPD-1 resistant, these tumors regress after single dose of oncolytic vaccinia virus (VV). We then generated a VV-resistant MEER line to dissect the immunologic features of sensitive and resistant tumors. While treatment of both tumor types induced immune infiltration and IFNγ, we found a defining feature of resistance was elevation of immunosuppressive cytokines like TGFβ, which blunted IFNγ signaling, especially in regulatory T cells. We engineered VV to express a genetically encoded TGFβRII inhibitor. Inhibitor-expressing VV produced regressions in resistant tumor models and showed impressive synergy with checkpoint blockade. Importantly, tumor-specific, viral delivery of TGFβ inhibition had no toxicities associated with systemic TGFβ/TGFβR inhibition. Our data suggest that aside from stimulating immune infiltration, oncolytic viruses are attractive means to deliver agents to limit immunosuppression in cancer.

Oncolytic virotherapy evolved into the fourth generation as tumor immunotherapy

BACKGROUND

Oncolytic virotherapy (OVT) is a promising anti-tumor modality that utilizes oncolytic viruses (OVs) to preferentially attack cancers rather than normal tissues. With the understanding particularly in the characteristics of viruses and tumor cells, numerous innovative OVs have been engineered to conquer cancers, such as Talimogene Laherparepvec (T-VEC) and tasadenoturev (DNX-2401). However, the therapeutic safety and efficacy must be further optimized and balanced to ensure the superior safe and efficient OVT in clinics, and reasonable combination therapy strategies are also important challenges worthy to be explored.

MAIN BODY

Here we provided a critical review of the development history and status of OVT, emphasizing the mechanisms of enhancing both safety and efficacy. We propose that oncolytic virotherapy has evolved into the fourth generation as tumor immunotherapy. Particularly, to arouse T cells by designing OVs expressing bi-specific T cell activator (BiTA) is a promising strategy of killing two birds with one stone. Amazing combination of therapeutic strategies of OVs and immune cells confers immense potential for managing cancers. Moreover, the attractive preclinical OVT addressed recently, and the OVT in clinical trials were systematically reviewed.

CONCLUSION

OVs, which are advancing into clinical trials, are being envisioned as the frontier clinical anti-tumor agents coming soon.

Reprogramming the tumor microenvironment leverages CD8+ T cell responses to a shared tumor/self antigen in ovarian cancer

Tumor antigen-driven responses to weakly immunogenic self-antigens and neoantigens directly affect treatment efficacy following immunotherapy. Using orthotopically grown SV40 T antigen+ ovarian carcinoma in antigen-naive wild-type or TgMISIIR-TAg-Low transgenic mice expressing SV40 T antigen as a self-antigen, we investigated the impact of CXCR4-antagonist-armed oncolytic virotherapy on tumor progression and antitumor immunity. Immunostaining and single-cell RNA sequencing analyses of the peritoneal tumor microenvironment of untreated tumors in syngeneic wild-type mice revealed the presence of SV40 T antigen-specific CD8+ T cells, a balanced M1/M2 transcriptomic signature of tumor-associated macrophages, and immunostimulatory cancer-associated fibroblasts. This contrasted with polarized M2 tumor-associated macrophages, immunosuppressive cancer-associated fibroblasts, and poor immune activation in TgMISIIR-TAg-Low mice. Intraperitoneal delivery of CXCR4-antagonist-armed oncolytic vaccinia virus led to nearly complete depletion of cancer-associated fibroblasts, M1 polarization of macrophages, and generation of SV40 T antigen-specific CD8+ T cells in transgenic mice. Cell depletion studies revealed that the therapeutic effect of armed oncolytic virotherapy was dependent primarily on CD8+ cells. These results demonstrate that targeting the interaction between immunosuppressive cancer-associated fibroblasts and macrophages in the tolerogenic tumor microenvironment by CXCR4-A-armed oncolytic virotherapy induces tumor/self-specific CD8+ T cell responses and consequently increases therapeutic efficacy in an immunocompetent ovarian cancer model.

Fatty acid transport protein inhibition sensitizes breast and ovarian cancers to oncolytic virus therapy via lipid modulation of the tumor microenvironment

Introduction

Adipocytes in the tumour microenvironment are highly dynamic cells that have an established role in tumour progression, but their impact on anti-cancer therapy resistance is becoming increasingly difficult to overlook.

Methods

We investigated the role of adipose tissue and adipocytes in response to oncolytic virus (OV) therapy in adipose-rich tumours such as breast and ovarian neoplasms.

Results

We show that secreted products in adipocyte-conditioned medium significantly impairs productive virus infection and OV-driven cell death. This effect was not due to the direct neutralization of virions or inhibition of OV entry into host cells. Instead, further investigation of adipocyte secreted factors demonstrated that adipocyte-mediated OV resistance is primarily a lipid-driven phenomenon. When lipid moieties are depleted from the adipocyte-conditioned medium, cancer cells are re-sensitized to OV-mediated destruction. We further demonstrated that blocking fatty acid uptake by cancer cells, in a combinatorial strategy with virotherapy, has clinical translational potential to overcome adipocyte-mediated OV resistance.

Discussion

Our findings indicate that while adipocyte secreted factors can impede OV infection, the impairment of OV treatment efficacy can be overcome by modulating lipid flux in the tumour milieu.

Transarterial viroembolization improves the therapeutic efficacy of immune-excluded liver cancer: Three birds with one stone

OBJECTIVE

To investigate the mechanism and efficacy of transarterial viroembolization (TAVE) with an oncolytic virus (OH2) for the treatment of liver cancer in rabbit VX2 tumor models.

MATERIALS AND METHODS

Subcutaneous tumor and liver cancer models were established to determine the optimal viral titer and administration modality of OH2. Different liver cancer models were established to evaluate the locoregional tumor response, synergistic and standby effects, survival benefit, and specific antitumor immune memory after TAVE treatment. The immune cell densities in tumor tissues were measured.

RESULTS

The optimal viral titer of OH2 was 1 × 10⁷ CCID₅₀. TAVE was the most effective modality with greater homogeneous OH2 distribution and therapeutic efficacy compared to other administration routes of transarterial virus infusion (TAVI), commonly adopted intratumor injection (TI), and intravenous injection (IV). Additionally, TAVE treatment significantly improved the locoregional tumor response, standby effect, and survival benefit compared to the TAVI, transarterial embolization (TAE), and control groups. TAVE modified the immune cell densities for immune-excluded liver cancer, partially destroyed vessel metastases, and established antitumor immune memory. The synergistic treatment efficacy of TAVE was superior to the simple addition of two independent monotherapies.

CONCLUSION

TAVE was the optimal and a safe modality for treating immune-excluded liver cancer, and its synergistic effect achieved a remarkable tumor response, standby effect, survival benefit, and antitumor immune memory, which providing an innovative therapeutic modality for clinical practice.

DATA AVAILABILITY

Data is available from the corresponding author upon requirement.

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.

Signaling pathways in cancer-associated fibroblasts: recent advances and future perspectives

As a critical component of the tumor microenvironment (TME), cancer-associated fibroblasts (CAFs) play important roles in cancer initiation and progression. Well-known signaling pathways, including the transforming growth factor-β (TGF-β), Hedgehog (Hh), Notch, Wnt, Hippo, nuclear factor kappa-B (NF-κB), Janus kinase (JAK)/signal transducer and activator of transcription (STAT), mitogen-activated protein kinase (MAPK), and phosphoinositide 3-kinase (PI3K)/AKT pathways, as well as transcription factors, including hypoxia-inducible factor (HIF), heat shock transcription factor 1 (HSF1), P53, Snail, and Twist, constitute complex regulatory networks in the TME to modulate the formation, activation, heterogeneity, metabolic characteristics and malignant phenotype of CAFs. Activated CAFs remodel the TME and influence the malignant biological processes of cancer cells by altering the transcriptional and secretory characteristics, and this modulation partially depends on the regulation of signaling cascades. The results of preclinical and clinical trials indicated that therapies targeting signaling pathways in CAFs demonstrated promising efficacy but were also accompanied by some failures (e.g., NCT01130142 and NCT01064622). Hence, a comprehensive understanding of the signaling cascades in CAFs might help us better understand the roles of CAFs and the TME in cancer progression and may facilitate the development of more efficient and safer stroma-targeted cancer therapies. Here, we review recent advances in studies of signaling pathways in CAFs and briefly discuss some future perspectives on CAF research.

Modifying oncolytic virotherapy to overcome the barrier of the hypoxic tumor microenvironment. Where do we stand?

Viruses are completely dependent on host cell machinery for their reproduction. As a result, factors that influence the state of cells, such as signaling pathways and gene expression, could determine the outcome of viral pathogenicity. One of the important factors influencing cells or the outcome of viral infection is the level of oxygen. Recently, oncolytic virotherapy has attracted attention as a promising approach to improving cancer treatment. However, it was shown that tumor cells are mostly less oxygenated compared with their normal counterparts, which might affect the outcome of oncolytic virotherapy. Therefore, knowing how oncolytic viruses could cope with stressful environments, particularly hypoxic environments, might be essential for improving oncolytic virotherapy.

Oncolytic virus driven T-cell-based combination immunotherapy platform for colorectal cancer

Colorectal cancer is the third most diagnosed cancer and the second leading cause of cancer mortality worldwide, highlighting an urgent need for new therapeutic options and combination strategies for patients. The orchestration of potent T cell responses against human cancers is necessary for effective antitumour immunity. However, regression of a limited number of cancers has been induced by immune checkpoint inhibitors, T cell engagers (TCEs) and/or oncolytic viruses. Although one TCE has been FDA-approved for the treatment of hematological malignancies, many challenges exist for the treatment of solid cancers. Here, we show that TCEs targeting CEACAM5 and CD3 stimulate robust activation of CD4 and CD8-positive T cells in in vitro co-culture models with colorectal cancer cells, but in vivo efficacy is hindered by a lack of TCE retention in the tumour microenvironment and short TCE half-life, as demonstrated by HiBiT bioluminescent TCE-tagging technology. To overcome these limitations, we engineered Bispecific Engager Viruses, or BEVirs, a novel tumour-targeted vaccinia virus platform for intra-tumour delivery of these immunomodulatory molecules. We characterized virus-mediated TCE-secretion, TCE specificity and functionality from infected colorectal cancer cells and patient tumour samples, as well as TCE cytotoxicity in spheroid models, in the presence and absence of T cells. Importantly, we show regression of colorectal tumours in both syngeneic and xenograft mouse models. Our data suggest that a different profile of cytokines may contribute to the pro-inflammatory and immune effects driven by T cells in the tumour microenvironment to provide long-lasting immunity and abscopal effects. We establish combination regimens with immune checkpoint inhibitors for aggressive colorectal peritoneal metastases. We also observe a significant reduction in lung metastases of colorectal tumours through intravenous delivery of our oncolytic virus driven T-cell based combination immunotherapy to target colorectal tumours and FAP-positive stromal cells or CTLA4-positive Treg cells in the tumour microenvironment. In summary, we devised a novel combination strategy for the treatment of colorectal cancers using oncolytic vaccinia virus to enhance immune-payload delivery and boost T cell responses within tumours.

Counteracting Immunosuppression in the Tumor Microenvironment by Oncolytic Newcastle Disease Virus and Cellular Immunotherapy

An apparent paradox exists between the evidence for spontaneous systemic T cell- mediated anti-tumor immune responses in cancer patients, observed particularly in their bone marrow, and local tumor growth in the periphery. This phenomenon, known as "concomitant immunity" suggests that the local tumor and its tumor microenvironment (TME) prevent systemic antitumor immunity to become effective. Oncolytic Newcastle disease virus (NDV), an agent with inherent anti-neoplastic and immune stimulatory properties, is capable of breaking therapy resistance and immunosuppression. This review updates latest information about immunosuppression by the TME and discusses mechanisms of how oncolytic viruses, in particular NDV, and cellular immunotherapy can counteract the immunosuppressive effect of the TME. With regard to cellular immunotherapy, the review presents pre-clinical studies of post-operative active-specific immunotherapy and of adoptive T cell-mediated therapy in immunocompetent mice. Memory T cell (MTC) transfer in tumor challenged T cell-deficient nu/nu mice demonstrates longevity and functionality of these cells. Graft-versus-leukemia (GvL) studies in mice demonstrate complete remission of late-stage disease including metastases and cachexia. T cell based immunotherapy studies with human cells in human tumor xenotransplanted NOD/SCID mice demonstrate superiority of bone marrow-derived as compared to blood-derived MTCs. Results from clinical studies presented include vaccination studies using two different types of NDV-modified cancer vaccine and a pilot adoptive T-cell mediated therapy study using re-activated bone marrow-derived cancer-reactive MTCs. As an example for what can be expected from clinical immunotherapy against tumors with an immunosuppressive TME, results from vaccination studies are presented from the aggressive brain tumor glioblastoma multiforme. The last decades of basic research in virology, oncology and immunology can be considered as a success story. Based on discoveries of these research areas, translational research and clinical studies have changed the way of treatment of cancer by introducing and including immunotherapy.

Oncolytic herpes simplex virus delivery of dual CAR targets of CD19 and BCMA as well as immunomodulators to enhance therapeutic efficacy in solid tumors combined with CAR T cell therapy

BACKGROUND

The CAR T-cell therapy is a promising approach to treating hematologic malignancies. However, the application in solid tumors still has many tough challenges, including heterogenicity in antigen expressions and immunosuppressive tumor microenvironment (TME). As a new cancer treatment modality, oncolytic virotherapy can be engineered to circumvent these obstacles for CAR T cell therapy in solid tumors.

METHODS

In this study, an oHSV T7011 is engineered to drive ectopic expression of dual-antigens, extracellular domains of CD19 and BCMA, on the solid tumor cell surface to be targeted by approved CAR T cells. In addition, multiple immunomodulators, CCL5, IL-12, and anti-PD-1 antibody are also included to modulate the TME. The antitumor activities of T7011 in combination with CD19 or BCMA CAR T-cell were evaluated in vitro and in vivo.

RESULTS

The expression of CD19 or BMCA on the tumor cell surface could be detected after T7011 infection. The level of CCL5 in TME was also increased. Efficacy studies demonstrated that combination with T7011 and CAR-TCD19 or CAR-TBCMA cells showed significant synergistic anti-tumor responses in several solid tumor models.

CONCLUSION

These studies indicated that the new generation of oHSV T7011 can be a promising combinational therapy with CD19 or BCMA-specific CAR T cells for the treatment of a broad range of solid tumors.

Immunovirotherapy: The role of antibody based therapeutics combination with oncolytic viruses

Despite the fact that the new drugs and targeted therapies have been approved for cancer therapy during the past 30 years, the majority of cancer types are still remain challenging to be treated. Due to the tumor heterogeneity, immune system evasion and the complex interaction between the tumor microenvironment and immune cells, the great majority of malignancies need multimodal therapy. Unfortunately, tumors frequently develop treatment resistance, so it is important to have a variety of therapeutic choices available for the treatment of neoplastic diseases. Immunotherapy has lately shown clinical responses in malignancies with unfavorable outcomes. Oncolytic virus (OV) immunotherapy is a cancer treatment strategy that employs naturally occurring or genetically-modified viruses that multiply preferentially within cancer cells. OVs have the ability to not only induce oncolysis but also activate cells of the immune system, which in turn activates innate and adaptive anticancer responses. Despite the fact that OVs were translated into clinical trials, with T-VECs receiving FDA approval for melanoma, their use in fighting cancer faced some challenges, including off-target side effects, immune system clearance, non-specific uptake, and intratumoral spread of OVs in solid tumors. Although various strategies have been used to overcome the challenges, these strategies have not provided promising outcomes in monotherapy with OVs. In this situation, it is increasingly common to use rational combinations of immunotherapies to improve patient benefit. With the development of other aspects of cancer immunotherapy strategies, combinational therapy has been proposed to improve the anti-tumor activities of OVs. In this regard, OVs were combined with other biotherapeutic platforms, including various forms of antibodies, nanobodies, chimeric antigen receptor (CAR) T cells, and dendritic cells, to reduce the side effects of OVs and enhance their efficacy. This article reviews the promising outcomes of OVs in cancer therapy, the challenges OVs face and solutions, and their combination with other biotherapeutic agents.

Clinicopathological and prognostic value of lysyl oxidase expression in gastric cancer: a systematic review, meta-analysis and bioinformatic analysis

The association between the expression of Lysyl oxidase (LOX) and its clinicopathological parameters and prognosis in patients with gastric cancer (GC) is still disputed. We performed this meta-analysis and bioinformatics analysis to clarify the relationship between the expression and methylation level of LOX with its clinicopathological parameters and prognostic value. We applied odds ratios with a 95% confidence interval to study the associations between LOX expression and clinicopathological parameters and overall survival (OS) in GC patients. In addition, association analysis of promoter methylation levels and expression of LOX with its prognostic value was performed using the Cancer Genome Atlas (TCGA) and four Gene Expression Omnibus (GEO) datasets. The PRISMA 2020 checklist was used to guide the data extraction and analysis. This meta-analysis includes seven clinical studies with a total of 1435 GC patients. LOX expression was related to lymph node metastasis and tumor distant metastasis in GC patients, but not to gender, tumor differentiation, Lauren classification, or tumor depth of invasion. Patients with GC grouped in high-expression of LOX had a much worse OS than those in low-expression. In addition, TCGA and four GEO datasets with 1279 samples were included in the bioinformatics analysis. The bioinformatics analysis showed that patients with high LOX levels had poor OS; low levels of methylation at some cg sites in the LOX gene were strongly related to poor OS and PFS; and methylation levels of LOX are negatively correlated with advanced tumor stage. The conclusion from comprehensive DNA methylation and gene expression analysis supports LOX as a specific diagnostic and prognosis biomarker in GC. LOX expression was related to lymph node metastasis, tumor distant metastasis and poor prognosis in GC. Low methylation levels were related to advanced tumor stage and poor prognosis in GC. Integrative analysis supports LOX as a specific diagnostic and prognosis biomarker in GC.

Combination therapy with CAR T cells and oncolytic viruses: a new era in cancer immunotherapy

Chimeric antigen receptor (CAR) T-cell therapy is an encouraging and fast-growing platform used for the treatment of various types of tumors in human body. Despite the recent success of CAR T-cell therapy in hematologic malignancies, especially in B-cell lymphoma and acute lymphoblastic leukemia, the application of this treatment approach in solid tumors faced several obstacles resulted from the heterogeneous expression of antigens as well as the induction of immunosuppressive tumor microenvironment. Oncolytic virotherapy (OV) is a new cancer treatment modality by the use of competent or genetically engineered viruses to replicate in tumor cells selectively. OVs represent potential candidates to synergize the current setbacks of CAR T-cell application in solid tumors and then and overcome them. As well, the application of OVs gives researches the ability to engineer the virus with payloads in the way that it selectively deliver a specific therapeutic agents in tumor milieu to reinforce the cytotoxic activity of CAR T cells. Herein, we made a comprehensive review on the outcomes resulted from the combination of CAR T-cell immunotherapy and oncolytic virotherapy for the treatment of solid cancers. In the current study, we also provided brief details on some challenges that remained in this field and attempted to shed a little light on the future perspectives.

Distinguishing the Pros and Cons of Metabolic Reprogramming in Oncolytic Virus Immunotherapy

Oncolytic viruses (OVs) represent a class of cancer immunotherapies that rely on hijacking the host cell factory for replicative oncolysis and eliciting immune responses for tumor clearance. An increasing evidence suggests that the metabolic state of tumor cells and immune cells is a putative determinant of the efficacy of cancer immunotherapy. However, how therapeutic intervention with OVs affects metabolic fluxes within the tumor microenvironment (TME) remains poorly understood. Herein, we review the complexities of metabolic reprogramming involving the effects of viruses and their consequences on tumor cells and immune cells. We highlight the inherent drawback of oncolytic virotherapy, namely that treatment with OVs inevitably further exacerbates the depletion of nutrients and the accumulation of metabolic wastes in the TME, leading to a metabolic barrier to antitumor immune responses. We also describe targeted metabolic strategies that can be used to unlock the therapeutic potential of OVs.

Remodeling the tumor microenvironment by oncolytic viruses: beyond oncolysis of tumor cells for cancer treatment

Tumor cells manipulate the local environment in which they grow, creating a tumor microenvironment (TME) that promotes tumor survival and metastasis. The TME is an extremely complex environment rich in immunosuppressive cells and cytokines. Various methods to therapeutically target the complicated TME are emerging as a potential approach for cancer treatment. Oncolytic viruses (OVs) are one of the most promising methods for remodeling the TME into an antitumor environment and can be used alone or in combination with other immunotherapy options. OVs replicate specifically in tumor cells and can be genetically engineered to target multiple elements of the TME simultaneously, thus representing a therapeutic with the potential to modify the TME to promote activation of antitumor immune cells and overcome tumor therapeutic resistance and recurrence. In this review, we analyze the tropism of OVs towards tumor cells and explore the interaction between OVs and immune cells, tumor stroma, vasculature and the metabolic environment in detail to help understand how OVs may be one of our most promising prospects for long-term curative therapies. We also discuss some of the challenges associated with TME therapies, and future perspectives in this evolving field.

Virally programmed extracellular vesicles sensitize cancer cells to oncolytic virus and small molecule therapy

Recent advances in cancer therapeutics clearly demonstrate the need for innovative multiplex therapies that attack the tumour on multiple fronts. Oncolytic or “cancer-killing” viruses (OVs) represent up-and-coming multi-mechanistic immunotherapeutic drugs for the treatment of cancer. In this study, we perform an in-vitro screen based on virus-encoded artificial microRNAs (amiRNAs) and find that a unique amiRNA, herein termed amiR-4, confers a replicative advantage to the VSVΔ51 OV platform. Target validation of amiR-4 reveals ARID1A, a protein involved in chromatin remodelling, as an important player in resistance to OV replication. Virus-directed targeting of ARID1A coupled with small-molecule inhibition of the methyltransferase EZH2 leads to the synthetic lethal killing of both infected and uninfected tumour cells. The bystander killing of uninfected cells is mediated by intercellular transfer of extracellular vesicles carrying amiR-4 cargo. Altogether, our findings establish that OVs can serve as replicating vehicles for amiRNA therapeutics with the potential for combination with small molecule and immune checkpoint inhibitor therapy.

RNA-based viruses can be engineered to express artificial microRNAs (amiRNAs). Here, the authors identify a candidate amiRNA that confers a replicative advantage to oncolytic viruses, enhancing their anticancer potency, and show that intercellular transfer of extracellular vesicles carrying the amiRNA promotes bystander killing of uninfected cancer cells.

Engineering strategies to enhance oncolytic viruses in cancer immunotherapy

Oncolytic viruses (OVs) are emerging as potentially useful platforms in treatment methods for patients with tumors. They preferentially target and kill tumor cells, leaving healthy cells unharmed. In addition to direct oncolysis, the essential and attractive aspect of oncolytic virotherapy is based on the intrinsic induction of both innate and adaptive immune responses. To further augment this efficacious response, OVs have been genetically engineered to express immune regulators that enhance or restore antitumor immunity. Recently, combinations of OVs with other immunotherapies, such as immune checkpoint inhibitors (ICIs), chimeric antigen receptors (CARs), antigen-specific T-cell receptors (TCRs) and autologous tumor-infiltrating lymphocytes (TILs), have led to promising progress in cancer treatment. This review summarizes the intrinsic mechanisms of OVs, describes the optimization strategies for using armed OVs to enhance the effects of antitumor immunity and highlights rational combinations of OVs with other immunotherapies in recent preclinical and clinical studies.

Infection of non-cancer cells: A barrier or support for oncolytic virotherapy?

Oncolytic viruses are designed to specifically target cancer cells, sparing normal cells. Although numerous studies demonstrate the ability of oncolytic viruses to infect a wide range of non-tumor cells, the significance of this phenomenon for cancer virotherapy is poorly understood. To fill the gap, we summarize the data on infection of non-cancer targets by oncolytic viruses with a special focus on tumor microenvironment and secondary lymphoid tissues. The review aims to address two major questions: how do attenuated viruses manage to infect normal cells, and whether it is of importance for oncolytic virotherapy.

Targeting Type I Collagen for Cancer Treatment

Collagen is the most abundant protein in animals. Interactions between tumor cells and collagen influence every step of tumor development. Type I collagen is the main fibrillar collagen in the extracellular matrix and is frequently up-regulated during tumorigenesis. The binding of type I collagen to its receptors on tumor cells promotes tumor cell proliferation, epithelial-mesenchymal transition, and metastasis. Type I collagen also regulates the efficacy of tumor therapies, such as chemotherapy, radiotherapy, and immunotherapy. Furthermore, type I collagen fragments are diagnostic markers of metastatic tumors and have prognostic value. Inhibition of type I collagen synthesis has been reported to have anti-tumor effects in animal models. However, collagen has also been shown to possess anti-tumor activity. Therefore, the roles that type I collagen plays in tumor biology are complex and tumor type-dependent. In this review, we discuss the expression and regulation of synthesis of type I collagen, as well as the role up-regulated type I collagen plays in various stages of cancer progression. We also discuss the role of collagen in tumor therapy. Finally, we highlight several recent approaches targeting type I collagen for cancer treatment. This article is protected by copyright. All rights reserved.

Gastrointestinal cancer-associated fibroblasts expressing Junctional Adhesion Molecule-A are amenable to infection by oncolytic reovirus

Gastrointestinal (GI) cancers are characterized by extensive tumor stroma that both promotes tumor progression and acts as a physical barrier for adjacent tumor cells, limiting the effect of current treatment modalities. Oncolytic virotherapy is currently investigated in clinical trials as a novel therapeutic agent for different malignancies of the GI tract, but it is largely unknown whether these viruses can also target the tumor stroma. Here, we investigated the tropism of two commonly studied OVs, adenovirus and reovirus, towards primary GI fibroblasts from human oesophageal, gastric, duodenal and pancreatic carcinomas (N = 36). GI fibroblasts were susceptible to type 3 Dearing (T3D) strain R124 and bioselected mutant reovirus (jin-3) infection but not oncolytic adenovirus (Ad5-Δ24). Efficient infection and apoptosis of human and mouse GI cancer-derived fibroblasts by these reoviruses was partially dependent on the expression of the reovirus entry receptor, Junctional Adhesion Molecule-A (JAM-A). Moreover, human GI cancer organoid-fibroblast co-cultures showed higher overall infectivity when containing JAM-A expressing fibroblasts as compared to JAM-A negative fibroblasts, indicating a potential role of JAM-A expressing fibroblasts for viral dissemination. We further show that JAM-A is not only necessary for efficient reovirus infection of fibroblasts but also partially mediates reovirus-induced apoptosis, dependent on signaling through the C-terminal PDZ-domain of JAM-A. Altogether, our data show the presence of JAM-A expressing fibroblasts in both human and murine GI cancers that are amenable to infection and induction of apoptosis by reovirus, extending the potential anti-cancer actions of reovirus with stromal targeting.

Emerging systemic delivery strategies of oncolytic viruses: A key step toward cancer immunotherapy

Oncolytic virotherapy (OVT) is a novel type of immunotherapy that induces anti-tumor responses through selective self-replication within cancer cells and oncolytic virus (OV)-mediated immunostimulation. Notably, talimogene laherparepvec (T-Vec) developed by the Amgen company in 2015, is the first FDA-approved OV product to be administered via intratumoral injection and has been the most successful OVT treatment. However, the systemic administration of OVs still faces huge challenges, including in vivo pre-existing neutralizing antibodies and poor targeting delivery efficacy. Recently, state-of-the-art progress has been made in the development of systemic delivery of OVs, which demonstrates a promising step toward broadening the scope of cancer immunotherapy and improving the clinical efficacy of OV delivery. Herein, this review describes the general characteristics of OVs, focusing on the action mechanisms of OVs as well as the advantages and disadvantages of OVT. The emerging multiple systemic administration approaches of OVs are summarized in the past five years. In addition, the combination treatments between OVT and traditional therapies (chemotherapy, thermotherapy, immunotherapy, and radiotherapy, etc.) are highlighted. Last but not least, the future prospects and challenges of OVT are also discussed, with the aim of facilitating medical researchers to extensively apply the OVT in the cancer therapy.

Resistance Mechanisms Influencing Oncolytic Virotherapy, a Systematic Analysis

Resistance to therapy is a frequently observed phenomenon in the treatment of cancer, and as with other cancer therapeutics, therapies based on oncolytic viruses also face the challenges of resistance, such as humoral and cellular antiviral responses, and tumor-associated interferon-mediated resistance. In order to identify additional mechanisms of resistance that may contribute to therapeutic failure, we developed a systematic search strategy for studies published in PubMed. We analyzed 6143 articles on oncolytic virotherapy and found that approximately 8% of these articles use resistance terms in the abstract and/or title. Of these 439 articles, 87 were original research. Most of the findings reported pertain to resistance mediated by tumor-cell-dependent interferon signaling. Yet, mechanisms such as epigenetic modifications, hypoxia-mediated inhibition, APOBEC-mediated resistance, virus entry barriers, and spatiotemporal restriction to viral spread, although not frequently assessed, were demonstrated to play a major role in resistance. Similarly, our results suggest that the stromal compartment consisting of, but not limited to, myeloid cells, fibroblasts, and epithelial cells requires more study in relation to therapy resistance using oncolytic viruses. Thus, our findings emphasize the need to assess the stromal compartment and to identify novel mechanisms that play an important role in conferring resistance to oncolytic virotherapy.

MicroRNA-sensitive oncolytic measles virus for chemovirotherapy of pancreatic cancer

Advanced pancreatic cancer is characterized by few treatment options and poor outcomes. Oncolytic virotherapy and chemotherapy involve complementary pharmacodynamics and could synergize to improve therapeutic efficacy. Likewise, multimodality treatment may cause additional toxicity, and new agents have to be safe. Balancing both aims, we generated an oncolytic measles virus for 5-fluorouracil-based chemovirotherapy of pancreatic cancer with enhanced tumor specificity through microRNA-regulated vector tropism. The resulting vector encodes a bacterial prodrug convertase, cytosine deaminase-uracil phosphoribosyl transferase, and carries synthetic miR-148a target sites in the viral F gene. Combination of the armed and targeted virus with 5-fluorocytosine, a prodrug of 5-fluorouracil, resulted in cytotoxicity toward both infected and bystander pancreatic cancer cells. In pancreatic cancer xenografts, a single intratumoral injection of the virus induced robust in vivo expression of prodrug convertase. Based on intratumoral transgene expression kinetics, we devised a chemovirotherapy regimen to assess treatment efficacy. Concerted multimodality treatment with intratumoral virus and systemic prodrug administration delayed tumor growth and prolonged survival of xenograft-bearing mice. Our results demonstrate that 5-fluorouracil-based chemovirotherapy with microRNA-sensitive measles virus is an effective strategy against pancreatic cancer at a favorable therapeutic index that warrants future clinical translation.

Oncolytic viruses encoding bispecific T cell engagers: a blueprint for emerging immunovirotherapies

Bispecific T cell engagers (BiTEs) are an innovative class of immunotherapeutics that redirect T cells to tumor surface antigens. While efficacious against certain hematological malignancies, limited bioavailability and severe toxicities have so far hampered broader clinical application, especially against solid tumors. Another emerging cancer immunotherapy are oncolytic viruses (OVs) which selectively infect and replicate in malignant cells, thereby mediating tumor vaccination effects. These oncotropic viruses can serve as vectors for tumor-targeted immunomodulation and synergize with other immunotherapies. In this article, we discuss the use of OVs to overcome challenges in BiTE therapy. We review the current state of the field, covering published preclinical studies as well as ongoing clinical investigations. We systematically introduce OV-BiTE vector design and characteristics as well as evidence for immune-stimulating and anti-tumor effects. Moreover, we address additional combination regimens, including CAR T cells and immune checkpoint inhibitors, and further strategies to modulate the tumor microenvironment using OV-BiTEs. The inherent complexity of these novel therapeutics highlights the importance of translational research including correlative studies in early-phase clinical trials. More broadly, OV-BiTEs can serve as a blueprint for diverse OV-based cancer immunotherapies.

The next frontier of oncotherapy: accomplishing clinical translation of oncolytic bacteria through genetic engineering

The development of a 'smart' drug capable of distinguishing tumor from host cells has been sought for centuries, but the microenvironment of solid tumors continues to confound therapeutics. Solid tumors present several challenges for current oncotherapeutics, including aberrant vascularization, hypoxia, necrosis, abnormally high pH and local immune suppression. While traditional chemotherapeutics are limited by such an environment, oncolytic microbes are drawn to it - having an innate ability to selectively infect, colonize and eradicate solid tumors. Development of an oncolytic species would represent a shift in the cancer therapeutic paradigm, with ramifications reaching from the medical into the socio-economic. Modern genetic engineering techniques could be implemented to customize 'Frankenstein' bacteria with advantageous characteristics from several species.

Expanding the Spectrum of Pancreatic Cancers Responsive to Vesicular Stomatitis Virus-Based Oncolytic Virotherapy: Challenges and Solutions

Simple Summary

Pancreatic ductal adenocarcinoma (PDAC) is a devastating malignancy with a poor prognosis and a dismal survival rate. Oncolytic virus (OV) is an anticancer approach that utilizes replication-competent viruses to preferentially infect and kill tumor cells. Vesicular stomatitis virus (VSV), one such OV, is already in several phase I clinical trials against different malignancies. VSV-based recombinant viruses are effective OVs against a majority of tested PDAC cell lines. However, some PDAC cell lines are resistant to VSV. This review discusses multiple mechanisms responsible for the resistance of some PDACs to VSV-based OV therapy, as well multiple rational approaches to enhance permissiveness of PDACs to VSV and expand the spectrum of PDACs responsive to VSV-based oncolytic virotherapy.

Abstract

Pancreatic ductal adenocarcinoma (PDAC) is a devastating malignancy with poor prognosis and a dismal survival rate, expected to become the second leading cause of cancer-related deaths in the United States. Oncolytic virus (OV) is an anticancer approach that utilizes replication-competent viruses to preferentially infect and kill tumor cells. Vesicular stomatitis virus (VSV), one such OV, is already in several phase I clinical trials against different malignancies. VSV-based recombinant viruses are effective OVs against a majority of tested PDAC cell lines. However, some PDAC cell lines are resistant to VSV. Upregulated type I IFN signaling and constitutive expression of a subset of interferon-simulated genes (ISGs) play a major role in such resistance, while other mechanisms, such as inefficient viral attachment and resistance to VSV-mediated apoptosis, also play a role in some PDACs. Several alternative approaches have been shown to break the resistance of PDACs to VSV without compromising VSV oncoselectivity, including (i) combinations of VSV with JAK1/2 inhibitors (such as ruxolitinib); (ii) triple combinations of VSV with ruxolitinib and polycations improving both VSV replication and attachment; (iii) combinations of VSV with chemotherapeutic drugs (such as paclitaxel) arresting cells in the G2/M phase; (iv) arming VSV with p53 transgenes; (v) directed evolution approach producing more effective OVs. The latter study demonstrated impressive long-term genomic stability of complex VSV recombinants encoding large transgenes, supporting further clinical development of VSV as safe therapeutics for PDAC.

Reovirus-induced cell-mediated immunity for the treatment of multiple myeloma within the resistant bone marrow niche

BACKGROUND

Multiple myeloma (MM) remains an incurable disease and oncolytic viruses offer a well-tolerated addition to the therapeutic arsenal. Oncolytic reovirus has progressed to phase I clinical trials and its direct lytic potential has been extensively studied. However, to date, the role for reovirus-induced immunotherapy against MM, and the impact of the bone marrow (BM) niche, have not been reported.

METHODS

This study used human peripheral blood mononuclear cells from healthy donors and in vitro co-culture of MM cells and BM stromal cells to recapitulate the resistant BM niche. Additionally, the 5TGM1-Kalw/RijHSD immunocompetent in vivo model was used to examine reovirus efficacy and characterize reovirus-induced immune responses in the BM and spleen following intravenous administration. Collectively, these in vitro and in vivo models were used to characterize the development of innate and adaptive antimyeloma immunity following reovirus treatment.

RESULTS

Using the 5TGM1-Kalw/RijHSD immunocompetent in vivo model we have demonstrated that reovirus reduces both MM tumor burden and myeloma-induced bone disease. Furthermore, detailed immune characterization revealed that reovirus: (i) increased natural killer (NK) cell and CD8+ T cell numbers; (ii) activated NK cells and CD8+ T cells and (iii) upregulated effector-memory CD8+ T cells. Moreover, increased effector-memory CD8+ T cells correlated with decreased tumor burden. Next, we explored the potential for reovirus-induced immunotherapy using human co-culture models to mimic the myeloma-supportive BM niche. MM cells co-cultured with BM stromal cells displayed resistance to reovirus-induced oncolysis and bystander cytokine-killing but remained susceptible to killing by reovirus-activated NK cells and MM-specific cytotoxic T lymphocytes.

CONCLUSION

These data highlight the importance of reovirus-induced immunotherapy for targeting MM cells within the BM niche and suggest that combination with agents which boost antitumor immune responses should be a priority.

Oncolytic Virotherapy in Solid Tumors: The Challenges and Achievements

Oncolytic virotherapy (OVT) is a promising approach in cancer immunotherapy. Oncolytic viruses (OVs) could be applied in cancer immunotherapy without in-depth knowledge of tumor antigens. The capability of genetic modification makes OVs exciting therapeutic tools with a high potential for manipulation. Improving efficacy, employing immunostimulatory elements, changing the immunosuppressive tumor microenvironment (TME) to inflammatory TME, optimizing their delivery system, and increasing the safety are the main areas of OVs manipulations. Recently, the reciprocal interaction of OVs and TME has become a hot topic for investigators to enhance the efficacy of OVT with less off-target adverse events. Current investigations suggest that the main application of OVT is to provoke the antitumor immune response in the TME, which synergize the effects of other immunotherapies such as immune-checkpoint blockers and adoptive cell therapy. In this review, we focused on the effects of OVs on the TME and antitumor immune responses. Furthermore, OVT challenges, including its moderate efficiency, safety concerns, and delivery strategies, along with recent achievements to overcome challenges, are thoroughly discussed.

Enhancing the Efficacy of Tumor Vaccines Based on Immune Evasion Mechanisms

Tumor vaccines aim to expand tumor-specific T cells and reactivate existing tumor-specific T cells that are in a dormant or unresponsive state. As such, there is growing interest in improving the durable anti-tumor activity of tumor vaccines. Failure of vaccine-activated T cells to protect against tumors is thought to be the result of the immune escape mechanisms of tumor cells and the intricate immunosuppressive tumor microenvironment. In this review, we discuss how tumor cells and the tumor microenvironment influence the effects of tumor infiltrating lymphocytes and summarize how to improve the efficacy of tumor vaccines by improving the design of current tumor vaccines and combining tumor vaccines with other therapies, such as metabolic therapy, immune checkpoint blockade immunotherapy and epigenetic therapy.

Intratumoral expression of IL-7 and IL-12 using an oncolytic virus increases systemic sensitivity to immune checkpoint blockade

The immune status of the tumor microenvironment is a key indicator in determining the antitumor effectiveness of immunotherapies. Data support the role of activation and expansion of tumor-infiltrating lymphocytes (TILs) in increasing the benefit of immunotherapies in patients with solid tumors. We found that intratumoral injection of a tumor-selective oncolytic vaccinia virus encoding interleukin-7 (IL-7) and IL-12 into tumor-bearing immunocompetent mice activated the inflammatory immune status of previously poorly immunogenic tumors and resulted in complete tumor regression, even in distant tumor deposits. Mice achieving complete tumor regression resisted rechallenge with the same tumor cells, suggesting establishment of long-term tumor-specific immune memory. Combining this virotherapy with anti-programmed cell death-1 (PD-1) or anti-cytotoxic T lymphocyte antigen 4 (CTLA4) antibody further increased the antitumor activity as compared to virotherapy alone, in tumor models unresponsive to either of the checkpoint inhibitor monotherapies. These findings suggest that administration of an oncolytic vaccinia virus carrying genes encoding for IL-7 and IL-12 has antitumor activity in both directly injected and distant noninjected tumors through immune status changes rendering tumors sensitive to immune checkpoint blockade. The benefit of intratumoral IL-7 and IL-12 expression was also observed in humanized mice bearing human cancer cells. These data support further investigation in patients with non-inflamed solid tumors.

Oncolytic Viruses and Hematological Malignancies: A New Class of Immunotherapy Drugs

The use of viruses for tumour treatment has been imagined more than one hundred years ago, when it was reported that viral diseases were occasionally leading to a decrease in neoplastic lesions. Oncolytic viruses (OVs) seem to have a specific tropism for tumour cells. Previously, it was hypothesised that OVs’ antineoplastic actions were mainly due to their ability to contaminate, proliferate and destroy tumour cells and the immediate destructive effect on cells was believed to be the single mechanism of action of OVs’ action. Instead, it has been established that oncolytic viruses operate via a multiplicity of systems, including mutation of tumour milieu and a composite change of the activity of immune effectors. Oncolytic viruses redesign the tumour environment towards an antitumour milieu. The aim of our work is to evaluate the findings present in the literature about the use of OVs in the cure of haematological neoplastic pathologies such as multiple myeloma, acute and chronic myeloid leukaemia, and lymphoproliferative diseases. Further experimentations are essential to recognize the most efficient virus or treatment combinations for specific haematological diseases, and the combinations able to induce the strongest immune response.

Novel Chimeric Poxvirus CF17 Improves Survival in a Murine Model of Intraperitoneal Ovarian Cancer Metastasis

Despite improvements in surgical techniques and chemotherapy, ovarian cancer remains the most lethal gynecologic cancer. Thus, there is an urgent need for more effective therapeutics, particularly for chemo-resistant peritoneal ovarian cancer metastases. Oncolytic virotherapy represents an innovative treatment paradigm; however, for oncolytic viruses tested from the last generation of genetically engineered viruses, the therapeutic benefits have been modest. To overcome these limitations, we generated a chimeric poxvirus, CF17, through the chimerization of nine species of orthopoxviruses. Compared with its parental viruses, CF17 has demonstrated superior oncolytic characteristics. Here, we report the oncolytic potential of CF17 in ovarian cancer. Replication of CF17 and its resulting cytotoxicity were observed at multiplicities of infection (MOIs) as low as 0.001 in human and mouse cancer cell lines in vitro. Furthermore, CF17 exerted potent antitumor effects in a syngeneic mouse model of ovarian cancer at doses as low as 6 × 10⁶ plaque-forming units. Together, these data merit further investigation of the potential use of this novel chimeric poxvirus as an effective treatment for aggressive intraperitoneal ovarian cancer.

The discovery and development of oncolytic viruses: are they the future of cancer immunotherapy?

Introduction: Despite diverse treatment modalities and novel therapies, many cancers and patients are not effectively treated. Cancer immunotherapy has recently achieved breakthrough status yet is not effective in all cancer types or patients and can generate serious adverse effects. Oncolytic viruses (OVs) are a promising new therapeutic modality that harnesses virus biology and host interactions to treat cancer. OVs, genetically engineered or natural, preferentially replicate in and kill cancer cells, sparing normal cells/tissues, and mediating anti-tumor immunity.Areas covered: This review focuses on OVs as cancer therapeutic agents from a historical perspective, especially strategies to boost their immunotherapeutic activities. OVs offer a multifaceted platform, whose activities are modulated based on the parental virus and genetic alterations. In addition to direct viral effects, many OVs can be armed with therapeutic transgenes to also act as gene therapy vectors, and/or combined with other drugs or therapies.Expert opinion: OVs are an amazingly versatile and malleable class of cancer therapies. They tend to target cellular and host physiology as opposed to specific genetic alterations, which potentially enables broad responsiveness. The biological complexity of OVs have hindered their translation; however, the recent approval of talimogene laherparepvec (T-Vec) has invigorated the field.

Characterization and oncolytic virus targeting of FAP-expressing tumor-associated pericytes in glioblastoma

Cancer-associated fibroblasts (CAFs) are activated fibroblasts constituting the major stromal components in many types of cancer. CAFs contribute to hallmarks of cancer such as proliferation, invasion and immunosuppressive tumor microenvironment, and are associated with poor prognosis of patients with cancer. However, in glioblastoma (GBM), the most common and aggressive primary malignant brain tumor, our knowledge about CAFs or CAF-like stromal cells is limited. Here, using commonly accepted CAF markers, we characterized CAF-like cell populations in clinical glioma specimens and datasets along with mouse models of GBM. We found that tumor-associated pericytes marked by co-expression of fibroblast activation protein α (FAP) and PDGFRβ represent major stromal cell subsets in both human GBM and mouse GBM models, while a fraction of mesenchymal neoplastic cells also express FAP in patient tumors. Since oncolytic viruses can kill cancer cells and simultaneously modulate the tumor microenvironment by impacting non-neoplastic populations such as immune cells and tumor vasculature, we further investigated the ability of oncolytic viruses to target GBM-associated stromal cells. An oncolytic adenovirus, ICOVIR15, carrying ∆24-E1A and an RGD-fiber, infects and depletes FAP+ pericytes as well as GBM cells in murine GBM. Our study thus identifies FAP+/PDGFRβ+ pericytes as a major CAF-like stromal cell population in GBM, and highlights the unique property of this oncolytic adenovirus to target both GBM cells and GBM-associated stromal FAP+ cells.

Simultaneous Tumor and Stroma Targeting by Oncolytic Viruses

Current cancer therapeutics often insufficiently eradicate malignant cells due to the surrounding dense tumor stroma. This multi-componential tissue consists of mainly cancer-associated fibroblasts, the (compact) extracellular matrix, tumor vasculature, and tumor-associated macrophages, which all exert crucial roles in maintaining a pro-tumoral niche. Their continuous complex interactions with tumor cells promote tumor progression and metastasis, emphasizing the challenges in tumor therapy development. Over the last decade, advances in oncolytic virotherapy have shown that oncolytic viruses (OVs) are a promising multi-faceted therapeutic platform for simultaneous tumor and stroma targeting. In addition to promoting tumor cell oncolysis and systemic anti-tumor immunity, accumulating data suggest that OVs can also directly target stromal components, facilitating OV replication and spread, as well as promoting anti-tumor activity. This review provides a comprehensive overview of the interactions between native and genetically modified OVs and the different targetable tumor stromal components, and outlines strategies to improve stroma targeting by OVs.

Gallbladder cancer-associated fibroblasts promote vasculogenic mimicry formation and tumor growth in gallbladder cancer via upregulating the expression of NOX4, a poor prognosis factor, through IL-6-JAK-STAT3 signal pathway

Background

Cancer-associated fibroblasts (CAFs) and vasculogenic mimicry (VM) play important roles in the occurrence and development of tumors. However, the relationship between CAFs and VM formation, especially in gallbladder cancer (GBC) has not been clarified. In this study, we investigated whether gallbladder CAFs (GCAFs) can promote VM formation and tumor growth and explored the underlying molecular mechanism.

Methods

A co-culture system of human GBC cells and fibroblasts or HUVECs was established. VM formation, proliferation, invasion, migration, tube formation assays, CD₃₁-PAS double staining, optic/electron microscopy and tumor xenograft assay were used to detect VM formation and malignant phenotypes of 3-D co-culture matrices in vitro, as well as the VM formation and tumor growth of xenografts in vivo, respectively. Microarray analysis was used to analyze gene expression profile in GCAFs/NFs and VM (+)/VM (−) in vitro. QRT-PCR, western blotting, IHC and CIF were used to detected NOX4 expression in GCAFs/NFs, 3-D culture/co-culture matrices in vitro, the xenografts in vivo and human gallbladder tissue/stroma samples. The correlation between NOX4 expression and clinicopathological and prognostic factors of GBC patients was analyzed. And, the underlying molecular mechanism of GCAFs promoting VM formation and tumor growth in GBC was explored.

Results

GCAFs promote VM formation and tumor growth in GBC; and the finding was confirmed by facts that GCAFs induced proliferation, invasion, migration and tube formation of GBC cells in vitro, and promoted VM formation and tumor growth of xenografts in vivo. NOX4 is highly expressed in GBC and its stroma, which is the key gene for VM formation, and is correlated with tumor aggression and survival of GBC patients. The GBC patients with high NOX4 expression in tumor cells and stroma have a poor prognosis. The underlying molecular mechanism may be related to the upregulation of NOX4 expression through paracrine IL-6 mediated IL-6/JAK/STAT3 signaling pathway.

Conclusions

GCAFs promote VM formation and tumor growth in GBC via upregulating NOX4 expression through the activation of IL-6-JAK-STAT3 signal pathway. NOX4, as a VM-related gene in GBC, is overexpressed in GBC cells and GCAFs, which is related to aggression and unfavorable prognosis of GBC patients.

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.

Past, Present and Future of Oncolytic Reovirus

Oncolytic virotherapy (OVT) has received significant attention in recent years, especially since the approval of talimogene Laherparepvec (T-VEC) in 2015 by the Food and Drug administration (FDA). Mechanistic studies of oncolytic viruses (OVs) have revealed that most, if not all, OVs induce direct oncolysis and stimulate innate and adaptive anti-tumour immunity. With the advancement of tumour modelling, allowing characterisation of the effects of tumour microenvironment (TME) components and identification of the cellular mechanisms required for cell death (both direct oncolysis and anti-tumour immune responses), it is clear that a "one size fits all" approach is not applicable to all OVs, or indeed the same OV across different tumour types and disease locations. This article will provide an unbiased review of oncolytic reovirus (clinically formulated as pelareorep), including the molecular and cellular requirements for reovirus oncolysis and anti-tumour immunity, reports of pre-clinical efficacy and its overall clinical trajectory. Moreover, as it is now abundantly clear that the true potential of all OVs, including reovirus, will only be reached upon the development of synergistic combination strategies, reovirus combination therapeutics will be discussed, including the limitations and challenges that remain to harness the full potential of this promising therapeutic agent.

Combination Immunotherapy Using Oncolytic Virus for the Treatment of Advanced Solid Tumors

Oncolytic virus (OV) is a new therapeutic strategy for cancer treatment. OVs can selectively infect and destroy cancer cells, and therefore act as an in situ cancer vaccine by releasing tumor-specific antigens. Moreover, they can remodel the tumor microenvironment toward a T cell-inflamed phenotype by stimulating widespread host immune responses against the tumor. Recent evidence suggests several possible applications of OVs against cancer, especially in combination with immune checkpoint inhibitors. In this review, we describe the molecular mechanisms of oncolytic virotherapy and OV-induced immune responses, provide a brief summary of recent preclinical and clinical updates on this rapidly evolving field, and discuss a combinational strategy that is able to overcome the limitations of OV-based monotherapy.

Identification of PKP 2/3 as potential biomarkers of ovarian cancer based on bioinformatics and experiments

Background

Plakophilins (PKPs) are widely involved in gene transcription, translation, and signal transduction, playing a crucial role in tumorigenesis and progression. However, the function and potential mechanism of PKP1/2/3 in ovarian cancer (OC) remains unclear. It’s of great value to explore the expression and prognostic values of PKP1/2/3 and their potential mechanisms, immune infiltration in OC.

Methods

The expression levels, prognostic values and genetic variations of PKP1/2/3 in OC were explored by various bioinformatics tools and databases, and PKP2/3 were selected for further analyzing their regulation network and immune infiltration. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes pathways (KEGG) enrichment were also conducted. Finally, the expression and prognosis of PKP2 were validated by immunohistochemistry.

Results

The expression level and prognosis of PKP1 showed little significance in ovarian cancer, and the expression of PKP2/3 mRNA and protein were upregulated in OC, showing significant correlations with poor prognosis of OC. Functional enrichment analysis showed that PKP2/3 and their correlated genes were significantly enriched in adaptive immune response, cytokine receptor activity, organization of cell–cell junction and extracellular matrix; KEGG analysis showed that PKP2/3 and their significantly correlated genes were involved in signaling pathways including cytokine-mediated signaling pathway, receptor signaling pathway and pathways in cancer. Moreover, PKP2/3 were correlated with lymphocytes and immunomodulators. We confirmed that high expression of PKP2 was significantly associated with advanced stage, poor differentiation and poor prognosis of OC patients.

Conclusion

Members of plakophilins family showed various degrees of abnormal expressions and prognostic values in ovarian cancer. PKP2/3 played crucial roles in tumorigenesis, aggressiveness, malignant biological behavior and immune infiltration of OC, and can be regarded as potential biomarker for early diagnosis and prognosis evaluation in OC.

The limiting factors of oncolytic virus immunotherapy and the approaches to overcome them

Oncolytic virus (OV) immunotherapy is characterized by viruses which specifically target cancer cells and cause their cytolysis. They provide a unique and promising new tool for the eradication of cancer as they interact with and affect the tumor microenvironment (TME), vasculature, and immune system. Advancements of genetic engineering have allowed for these viruses to be armed in such a way to have enhanced targeting, strong immunomodulation properties, and an ability to modify the TME. However, there are still major limitations in their use, mostly due to difficulties in delivering the viral particles to the tumors and in ensuring that the immunomodulatory properties are able to stimulate the host immune response to mount a complete response. Using novel delivery systems and using OVs as a complementary therapy in a combinatorial treatment have shown some significant successes. In this review, we discuss the major issues and difficulties in using OVs as anti-tumor agents and some of the strategies put in place so far to overcome these limitations. KEY POINTS: • Oncolytic viruses (OVs) infect cancer cells and cause their cytolysis. • The major limitations in using OVs as anti-tumor therapy were discussed. • The potential strategies to overcome these limitations were summarized.

A Cellular Automata Model of Oncolytic Virotherapy in Pancreatic Cancer

Oncolytic virotherapy is known as a new treatment to employ less virulent viruses to specifically target and damage cancer cells. This work presents a cellular automata model of oncolytic virotherapy with an application to pancreatic cancer. The fundamental biomedical processes (like cell proliferation, mutation, apoptosis) are modeled by the use of probabilistic principles. The migration of injected viruses (as therapy) is modeled by diffusion through the tissue. The resulting diffusion–reaction equation with smoothed point viral sources is discretized by the finite difference method and integrated by the IMEX approach. Furthermore, Monte Carlo simulations are done to quantitatively evaluate the correlations between various input parameters and numerical results. As we expected, our model is able to simulate the pancreatic cancer growth at early stages, which is calibrated with experimental results. In addition, the model can be used to predict and evaluate the therapeutic effect of oncolytic virotherapy.

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

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