The oncolytic herpes simplex virus vector G47∆ effectively targets breast cancer stem cells

The prevalence of varicella zoster virus, herpes simplex virus type 2, and human papillomavirus in breast cancerous tissues and their adjacent ones in Iran

Background

Breast cancer is the second type of cancer in the world. Some internal and external risk factors, especially infection diseases, can progress breast cancer. As the relation between varicella zoster virus (VZV), human papillomavirus (HPV), herpes simplex virus type 2 (HSV-2), and breast cancer has not been understood, it was attempting to find the effect of these viruses and breast cancer in this study.

Materials and Methods

We collected 40 breast cancer and 50 healthy adjacent tissues from Taleghani and Imam Hossein Hospital, Tehran, Iran, in 3 years starting in 2017. After extracting DNA from breast tissues, multiplex polymerase chain reaction (PCR), nested PCR, and PCR were done to analyze the prevalence of HSV-2, VZV, and HPV.

Results

Our results showed that HPV may be one of the important causes of breast cancer. Nested PCR illustrated nine breast cancerous tissues (mean age: 43) and three healthy adjacent ones (mean age: 41) were infected by HPV. Phylogenetic analysis illustrated that all of the infected HPV cancerous and healthy tissues were HPV 18 (except two healthy samples infected with HPV 6). Nevertheless, there were not any infected tissues by HSV-2 and VZV.

Conclusion

It seems that HPV virus type 18 can have high prevalence in breast cancerous tissues in comparison with healthy adjacent ones, and it is likely to have an effect on breast cancer progression. However, the opposite trend is true for HSV-2 and VZV as we did not find any differences between different kinds of breast tissues.

Oncolytic BHV-1 Is Sufficient to Induce Immunogenic Cell Death and Synergizes with Low-Dose Chemotherapy to Dampen Immunosuppressive T Regulatory Cells

Immunogenic cell death (ICD) can switch immunologically "cold" tumors "hot", making them sensitive to immune checkpoint inhibitor (ICI) therapy. Many therapeutic platforms combine multiple modalities such as oncolytic viruses (OVs) and low-dose chemotherapy to induce ICD and improve prognostic outcomes. We previously detailed many unique properties of oncolytic bovine herpesvirus type 1 (oBHV) that suggest widespread clinical utility. Here, we show for the first time, the ability of oBHV monotherapy to induce bona fide ICD and tumor-specific activation of circulating CD8⁺ T cells in a syngeneic murine model of melanoma. The addition of low-dose mitomycin C (MMC) was necessary to fully synergize with ICI through early recruitment of CD8⁺ T cells and reduced infiltration of highly suppressive PD-1⁺ Tregs. Cytokine and gene expression analyses within treated tumors suggest that the addition of MMC to oBHV therapy shifts the immune response from predominantly anti-viral, as evidenced by a high level of interferon-stimulated genes, to one that stimulates myeloid cells, antigen presentation and adaptive processes. Collectively, these data provide mechanistic insights into how oBHV-mediated therapy modalities overcome immune suppressive tumor microenvironments to enable the efficacy of ICI therapy.

Inactivation of the UL37 Deamidase Enhances Virus Replication and Spread of the HSV-1(VC2) Oncolytic Vaccine Strain and Secretion of GM-CSF

The HSV-1 (VC2) live-attenuated vaccine strain was engineered with specific deletions in the amino termini of glycoprotein K (gK) and membrane protein UL20, rendering the virus unable to enter neurons and establish latency. VC2 replicates efficiently in epithelial cell culture but produces lower viral titers and smaller viral plaques than its parental HSV-1 (F) wild-type virus. VC2 is an effective live-attenuated vaccine against HSV-1 and HSV-2 infections in mice and guinea pigs and an anti-tumor immunotherapeutic and oncolytic virus against melanoma and breast cancer in mouse models. Previously, we reported that the gK/UL20 complex interacts with the UL37 tegument protein, and this interaction is essential for virion intracellular envelopment and egress. To investigate the potential role of the UL37 deamidase functions, the recombinant virus FC819S and VC2C819S were constructed with a C819S substitution to inactivate the UL37 predicted deamidase active site on an HSV-1(F) and HSV-1(VC2) genetic background, respectively. FC819S replicated to similar levels with HSV-1(F) and produced similar size viral plaques. In contrast, VC2C819S replication was enhanced, and viral plaques increased in size, approaching those of the wild-type HSV-1(F) virus. FC819S infection of cell cultures caused enhanced GM-CSF secretion in comparison to HSV-1(F) across several cell lines, including HEp2 cells and cancer cell lines, DU145 (prostate) and Panc 04.03 (pancreas), and primary mouse peritoneal cells. VC2 infection of these cell lines caused GM-CSF secretion at similar levels to FC819S infection. However, the VC2C819S virus did not exhibit any further enhancement of GM-CSF secretion compared to the VC2 virus. These results suggest that the UL37 deamidation functions in conjunction with the gK/UL20 complex to facilitate virus replication and GM-CSF secretion.

Triple-mutated oncolytic herpes virus for treating both fast- and slow-growing tumors

Oncolytic virus therapy has emerged as a promising treatment option against cancer. To date, oncolytic viruses have been developed for malignant tumors, but the need for this new therapeutic modality also exists for benign and slow‐growing tumors. G47∆ is an oncolytic herpes simplex virus type 1 (HSV‐1) with an enhanced replication capability highly selective to tumor cells due to genetically engineered, triple mutations in the γ34.5, ICP6 and α47 genes. To create a powerful, but safe oncolytic HSV‐1 that replicates efficiently in tumors regardless of growth speed, we used a bacterial artificial chromosome system that allows a desired promoter to regulate the expression of the ICP6 gene in the G47∆ backbone. Restoration of the ICP6 function in a tumor‐specific manner using the hTERT promoter led to a highly capable oncolytic HSV‐1. T‐hTERT was more efficacious in the slow‐growing OS‐RC‐2 and DU145 tumors than the control viruses, while retaining a high efficacy in the fast‐growing U87MG tumors. The safety features are also retained, as T‐hTERT proved safe when inoculated into the brain of HSV‐1 sensitive A/J mice. This new technology should facilitate the use of oncolytic HSV‐1 for all tumors irrespective of growth speed.

HSV-1 Oncolytic Viruses from Bench to Bedside: An Overview of Current Clinical Trials

Herpes simplex virus 1 (HSV-1) provides a genetic chassis for several oncolytic viruses (OVs) currently in clinical trials. Oncolytic HSV1 (oHSV) have been engineered to reduce neurovirulence and enhance anti-tumor lytic activity and immunogenicity to make them attractive candidates in a range of oncology indications. Successful clinical data resulted in the FDA-approval of the oHSV talimogene laherparepvec (T-Vec) in 2015, and several other variants are currently undergoing clinical assessment and may expand the landscape of future oncologic therapy options. This review offers a detailed overview of the latest results from clinical trials as well as an outlook on newly developed HSV-1 oncolytic variants with improved tumor selectivity, replication, and immunostimulatory capacity and related clinical studies.

Designer nanocarriers for navigating the systemic delivery of oncolytic viruses

Nanotechnology is paving the way for new carrier systems designed to overcome the greatest challenges of oncolytic virotherapy; systemic administration and subsequent implications of immune responses and specific cell binding and entry. Systemic administration of oncolytic agents is vital for disseminated neoplasms, however transition of nanoparticles (NP) to virotherapy has yielded modest results. Their success relies on how they navigate the merry-go-round of often-contradictory phases of NP delivery: circulatory longevity, tissue permeation and cellular interaction, with many studies postulating design features optimal for each phase. This review discusses the optimal design of NPs for the transport of oncolytic viruses within these phases, to determine whether improved virotherapeutic efficacy lies in the pharmacokinetic/pharmacodynamics characteristics of the NP-oncolytic viruses complexes rather than manipulation of the virus and targeting ligands.

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.

Recent advances of oncolytic virus in cancer therapy

Oncolytic viruses have been taking the front stage in biological therapy for cancer recently. The first and most potent virus to be used in oncolytic virotherapy is human adenovirus. Recently, ongoing extensive research has suggested that other viruses like herpes simplex virus (HSV) and measles virus can also be considered as potential candidates in cancer therapy. An HSV-based oncolytic virus, T-VEC, has completed phase Ш clinical trial and has been approved by the U.S. Food and Drug Administration (FDA) for use in biological cancer therapy. Moreover, the vaccine strain of the measles virus has shown impressive results in pre-clinical and clinical trials. Considering their therapeutic efficacy, safety, and reduced side effects, the use of such engineered viruses in biological cancer therapy has the potential to establish a milestone in cancer research. In this review, we summarize the recent clinical advances in the use of oncolytic viruses in biological therapy for cancer. Additionally, this review evaluates the potential viral candidates for their benefits and shortcomings and sheds light on the future prospects.

Oncolytic viruses: how "lytic" must they be for therapeutic efficacy?

Oncolytic viruses (OVs) preferentially target and kill cancer cells without affecting healthy cells through a multi-modal mechanism of action. While historically the direct killing activity of OVs was considered the primary mode of action, initiation or augmentation of a host antitumor immune response is now considered an essential aspect of oncolytic virotherapy. To improve oncolytic virotherapy, many studies focus on increasing virus replication and spread. In this article, we open for discussion the traditional dogma that correlates replication with the efficacy of OVs, pointing out several examples that oppose this principle.

Therapeutic potency of oncolytic virotherapy in breast cancer targeting, current status and perspective

Breast cancer is the most common cause of cancer death in women and presents a serious therapeutic challenge worldwide. Traditional treatments are less successful at targeting cancer tumors, leading to recurrent treatment-resistant secondary malignancies. Oncolytic virotherapy (OV) is a novel anticancer strategy with therapeutic implications at targeting cancer cells by using mechanisms that differ from conventional therapies. Administration of OVs either alone or in combination with standard therapies provide new insights regarding the effectiveness and improvement of treatment responses for breast cancer patients. This review summarizes cellular, animal and clinical studies investigating therapeutic potency of oncolytic virotherapy in breast cancer treatment for a better understanding and hence a better management of this disease.

Comparative proteomics as a tool for identifying specific alterations within interferon response pathways in human glioblastoma multiforme cells

An acquisition of increased sensitivity of cancer cells to viruses is a common outcome of malignant progression that justifies the development of oncolytic viruses as anticancer therapeutics. Studying molecular changes that underlie the sensitivity to viruses would help to identify cases where oncolytic virus therapy would be most effective. We quantified changes in protein abundances in two glioblastoma multiforme (GBM) cell lines that differ in the ability to induce resistance to vesicular stomatitis virus (VSV) infection in response to type I interferon (IFN) treatment. In IFN-treated samples we observed an up-regulation of protein products of some IFN-regulated genes (IRGs). In total, the proteome analysis revealed up to 20% more proteins encoded by IRGs in the glioblastoma cell line, which develops resistance to VSV infection after pre-treatment with IFN. In both cell lines protein-protein interaction and signaling pathway analyses have revealed a significant stimulation of processes related to type I IFN signaling and defense responses to viruses. However, we observed a deficiency in STAT2 protein in the VSV-sensitive cell line that suggests a de-regulation of the JAK/STAT/IRF9 signaling. The study has shown that the up-regulation of IRG proteins induced by the IFNα treatment of GBM cells can be detected at the proteome level. Similar analyses could be applied for revealing functional alterations within the antiviral mechanisms in glioblastoma samples, accompanying by acquisition of sensitivity to oncolytic viruses. The approach can be useful for discovering the biomarkers that predict a potential sensitivity of individual glioblastoma tumors to oncolytic virus therapy.

Targeting Nucleotide Biosynthesis: A Strategy for Improving the Oncolytic Potential of DNA Viruses

The rapid growth of tumors depends upon elevated levels of dNTPs, and while dNTP concentrations are tightly regulated in normal cells, this control is often lost in transformed cells. This feature of cancer cells has been used to advantage to develop oncolytic DNA viruses. DNA viruses employ many different mechanisms to increase dNTP levels in infected cells, because the low concentration of dNTPs found in non-cycling cells can inhibit virus replication. By disrupting the virus-encoded gene(s) that normally promote dNTP biosynthesis, one can assemble oncolytic versions of these agents that replicate selectively in cancer cells. This review covers the pathways involved in dNTP production, how they are dysregulated in cancer cells, and the various approaches that have been used to exploit this biology to improve the tumor specificity of oncolytic viruses. In particular, we compare and contrast the ways that the different types of oncolytic virus candidates can directly modulate these processes. We limit our review to the large DNA viruses that naturally encode homologs of the cellular enzymes that catalyze dNTP biogenesis. Lastly, we consider how this knowledge might guide future development of oncolytic viruses.

Oncolytic Adenovirus Expressing Monoclonal Antibody Trastuzumab for Treatment of HER2-Positive Cancer

Monoclonal anti-HER2 antibody trastuzumab has significantly improved the survival of patients with HER2-overexpressing tumors. Nevertheless, systemic antibody therapy is expensive, limited in efficacy due to physical tumor barriers, and carries the risk of severe side effects such as cardiomyopathy. Oncolytic viruses mediate cancer-selective transgene expression, kill infected cancer cells while mounting antitumor immune responses, and have recently demonstrated promising efficacy in combination treatments. Here, we armed an oncolytic adenovirus with full-length trastuzumab to achieve effective in situ antibody production coupled with progressive oncolytic cancer cell killing. We constructed an infectivity-enhanced serotype 5 oncolytic adenovirus, Ad5/3-Δ24-tras, coding for human trastuzumab antibody heavy- and light-chain genes, connected by an internal ribosome entry site. Infected cancer cells were able to assemble full-length functional antibody, as confirmed by Western blot, ELISA, and antibody-dependent cell-mediated cytotoxicity assay. Importantly, oncolysis was required for release of the antibody into tumors, providing additional spatial selectivity. Ad5/3-Δ24-tras showed potent in vitro cytotoxicity and enhanced antitumor efficacy over oncolytic control virus Ad5/3-Δ24 or commercial trastuzumab in HER2-positive cancer models in vivo (both P < 0.05). Furthermore, Ad5/3-Δ24-tras resulted in significantly higher tumor-to-systemic antibody concentrations (P < 0.001) over conventional delivery. Immunological analyses revealed dendritic cell activation and natural killer cell accumulation in tumor-draining lymph nodes. Thus, Ad5/3-Δ24-tras is an attractive anticancer approach combining oncolytic immunotherapy with local trastuzumab production, resulting in improved in vivo efficacy and immune cell activation in HER2-positive cancer. Moreover, the finding that tumor cells can produce functional antibody as directed by oncolytic virus could lead to many valuable antitumor approaches. Mol Cancer Ther; 15(9); 2259-69. ©2016 AACR.

Cancer immunotherapy via combining oncolytic virotherapy with chemotherapy: recent advances

Oncolytic viruses are multifunctional anticancer agents with huge clinical potential, and have recently passed the randomized Phase III clinical trial hurdle. Both wild-type and engineered viruses have been selected for targeting of specific cancers, to elicit cytotoxicity, and also to generate antitumor immunity. Single-agent oncolytic virotherapy treatments have resulted in modest effects in the clinic. There is increasing interest in their combination with cytotoxic agents, radiotherapy and immune-checkpoint inhibitors. Similarly to oncolytic viruses, the benefits of chemotherapeutic agents may be that they induce systemic antitumor immunity through the induction of immunogenic cell death of cancer cells. Combining these two treatment modalities has to date resulted in significant potential in vitro and in vivo synergies through various mechanisms without any apparent additional toxicities. Chemotherapy has been and will continue to be integral to the management of advanced cancers. This review therefore focuses on the potential for a number of common cytotoxic agents to be combined with clinically relevant oncolytic viruses. In many cases, this combined approach has already advanced to the clinical trial arena.

The oncolytic herpes simplex virus vector, G47Δ, effectively targets tamoxifen-resistant breast cancer cells

The aim of the present study was to establish a tamoxifen-resistant cell line (MCF-7/TAM-R) and to investigate the therapeutic effect of G47Δ on this cell line both in vitro and in vivo. In the present study, the MCF-7/TAM-R monoclonal subline was established after exposing MCF-7 cells to tamoxifen for 21 days. Then, it was compared with a wild-type MCF-7 subline (MCF-7W), which was not treated with tamoxifen. Cell proliferation, viability, cell cycle and apoptosis analyses were carried out to examine the characteristics of the MCF-7/TAM-R cells. Both in vitro and in vivo toxicity studies were conducted to investigate the therapeutic effect of G47Δ on the MCF-7/TAM-R cells. Compared to the MCF-7W cells, we found that the MCF-7/TAM-R cells exhibited a higher proliferation ability (P<0.05) and a stronger resistance to the cytotoxic effects induced by 4-hydroxytamoxifen (4-OHT) (P<0.05). G47Δ demonstrated a high cytotoxic effect on both the MCF-7/TAM-R and MCF-7W cell lines. After being infected with G47Δ at an MOI of 0.01, >90% of the MCF-7/TAM-R and MCF-7W cells died on day 5. G47Δ induced cell cycle arrest in the G2/M phase. Furthermore, G47Δ inhibited tumor growth in subcutaneous tumor models of both MCF-7/TAM-R and MCF-7W. Thus, we conclude that G47Δ, a third generation oncolytic herpes simplex virus, is highly sensitive and safe in targeting tamoxifen-resistant breast cancer cells both in vitro and in vivo.

Oncolytic bovine herpesvirus type 1 as a broad spectrum cancer therapeutic

Oncolytic viruses selectively replicate in tumor cells and elicit antitumor effects in vivo by both direct and indirect methods. They are attractive avenues of cancer therapy due to the absence of toxic side effects often seen in current treatment modalities. Bovine herpesvirus type 1 (BHV-1) holds promise as a broad-spectrum oncolytic vector that is able to infect and kill human tumor cells from a variety of histological origins, including cancer-initiating cells. In the majority of cases, BHV-1 elicits tumor cell death in the absence of a productive infection. In vivo, BHV-1 affects the incidence of secondary lesions in cotton rats bearing subcutaneous breast adenocarcinomas. These recent studies contribute to the characterization of BHV-1 as an oncolytic virus.