Inhibition of autophagy enhances the effects of E1A-defective oncolytic adenovirus dl922-947 against glioma cells in vitro and in vivo

Revolutionizing cancer treatment: the power of bi- and tri-specific T-cell engagers in oncolytic virotherapy

Bi- or tri-specific T cell engagers (BiTE or TriTE) are recombinant bispecific proteins designed to stimulate T-cell immunity directly, bypassing antigen presentation by antigen-presenting cells (APCs). However, these molecules suffer from limitations such as short biological half-life and poor residence time in the tumor microenvironment (TME). Fortunately, these challenges can be overcome when combined with OVs. Various strategies have been developed, such as encoding secretory BiTEs within OV vectors, resulting in improved targeting and activation of T cells, secretion of key cytokines, and bystander killing of tumor cells. Additionally, oncolytic viruses armed with BiTEs have shown promising outcomes in enhancing major histocompatibility complex I antigen (MHC-I) presentation, T-cell proliferation, activation, and cytotoxicity against tumor cells. These combined approaches address tumor heterogeneity, drug delivery, and T-cell infiltration, offering a comprehensive and effective solution. This review article aims to provide a comprehensive overview of Bi- or TriTEs and OVs as promising therapeutic approaches in the field of cancer treatment. We summarize the cutting-edge advancements in oncolytic virotherapy immune-related genetic engineering, focusing on the innovative combination of BiTE or TriTE with OVs.

Oncolytic viruses-modulated immunogenic cell death, apoptosis and autophagy linking to virotherapy and cancer immune response

Recent reports have revealed that oncolytic viruses (OVs) play a significant role in cancer therapy. The infection of OVs such as oncolytic vaccinia virus (OVV), vesicular stomatitis virus (VSV), parvovirus, mammalian reovirus (MRV), human adenovirus, Newcastle disease virus (NDV), herpes simplex virus (HSV), avian reovirus (ARV), Orf virus (ORFV), inactivated Sendai virus (ISV), enterovirus, and coxsackievirus offer unique opportunities in immunotherapy through diverse and dynamic pathways. This mini-review focuses on the mechanisms of OVs-mediated virotherapy and their effects on immunogenic cell death (ICD), apoptosis, autophagy and regulation of the immune system.

Combination of dl922-947 Oncolytic Adenovirus and G-Quadruplex Binders Uncovers Improved Antitumor Activity in Breast Cancer

G-quadruplexes (G4s) are nucleic secondary structures characterized by G-tetrads. G4 motif stabilization induces DNA damage and cancer cell death; therefore, G4-targeting small molecules are the focus of clinical investigation. DNA destabilization induced by G4 ligands might potentiate the anticancer activity of agents targeting DNA or inhibiting its repair such as oncolytic viruses. This study represents the first approach combining G4 ligands, BRACO-19 (B19), pyridostatin (PDS), and the adenovirus dl922-947 in breast cancer cells. We demonstrated that G4 binders and dl922-947 induce cytotoxicity in breast cancer cells (MDA-MB-231 and MCF-7) and at higher doses in other neoplastic cell lines of thyroid (BHT-101 cells) and prostate (PC3 cells). G4 binders induce G4 motifs distributed in the S and G2/M phases in MCF-7 cells. G4 binder/dl922-947 combination increases cell cytotoxicity and the accumulation in subG0/G1. Indeed, G4 binders favor viral entry and replication with no effect on coxsackie and adenovirus receptor. Notably, dl922-947 induces G4 motifs and its combination with PDS potentiates this effect in MCF-7 cells. The agents alone or in combination similarly enhanced cell senescence. Additionally, PDS/dl922-947 combination inactivates STING signaling in MDA-MB-231 cells. Our results suggest that G4 binder/virotherapy combination may represent a novel therapeutic anticancer approach.

Immunology Meets Bioengineering: Improving the Effectiveness of Glioblastoma Immunotherapy

Glioblastoma (GBM) therapy has seen little change over the past two decades. Surgical excision followed by radiation and chemotherapy is the current gold standard treatment. Immunotherapy techniques have recently transformed many cancer treatments, and GBM is now at the forefront of immunotherapy research. GBM immunotherapy prospects are reviewed here, with an emphasis on immune checkpoint inhibitors and oncolytic viruses. Various forms of nanomaterials to enhance immunotherapy effectiveness are also discussed. For GBM treatment and immunotherapy, we outline the specific properties of nanomaterials. In addition, we provide a short overview of several 3D (bio)printing techniques and their applications in stimulating the GBM microenvironment. Lastly, the susceptibility of GBM cancer cells to the various immunotherapy methods will be addressed.

Inhibition of MEK-ERK pathway enhances oncolytic vaccinia virus replication in doxorubicin-resistant ovarian cancer

Oncolytic vaccinia virus (OVV) has been reported to induce cell death in various types of cancer; however, the oncolytic activity of OVV in drug-resistant ovarian cancer remains limited. In the present study, we established doxorubicin-resistant ovarian cancer cells (A2780-R) from the A2780 human ovarian cancer cell line. Both A2780 and A2780-R cells were infected with OVV to explore its anticancer effects. Interestingly, OVV-infected A2780-R cells showed reduced viral replication and cell death compared with A2780 cells, suggesting their resistance against OVV-induced oncolysis; to understand the mechanism underlying this resistance, we explored the involvement of protein kinases. Among protein kinase inhibitors, PD0325901, an MEK inhibitor, significantly augmented OVV replication and cell death in A2780-R cells. PD0325901 treatment increased the phosphorylation of STAT3 in A2780-R cells. Moreover, cryptotanshinone, a STAT3 inhibitor, abrogated PD0325901-stimulated OVV replication. Furthermore, trametinib, a clinically approved MEK inhibitor, increased OVV replication in A2780-R cells. Transcriptomic analysis showed that the MEK inhibitor promoted OVV replication via increasing STAT3 activation and downregulating the cytosolic DNA-sensing pathway. Combined treatment with OVV and trametinib attenuated A2780-R xenograft tumor growth. These results suggest that pharmacological inhibition of MEK reinforces the oncolytic efficacy of OVV in drug-resistant ovarian cancer.

Targeting autophagy in prostate cancer: preclinical and clinical evidence for therapeutic response

Prostate cancer is a leading cause of death worldwide and new estimates revealed prostate cancer as the leading cause of death in men in 2021. Therefore, new strategies are pertinent in the treatment of this malignant disease. Macroautophagy/autophagy is a “self-degradation” mechanism capable of facilitating the turnover of long-lived and toxic macromolecules and organelles. Recently, attention has been drawn towards the role of autophagy in cancer and how its modulation provides effective cancer therapy. In the present review, we provide a mechanistic discussion of autophagy in prostate cancer. Autophagy can promote/inhibit proliferation and survival of prostate cancer cells. Besides, metastasis of prostate cancer cells is affected (via induction and inhibition) by autophagy. Autophagy can affect the response of prostate cancer cells to therapy such as chemotherapy and radiotherapy, given the close association between autophagy and apoptosis. Increasing evidence has demonstrated that upstream mediators such as AMPK, non-coding RNAs, KLF5, MTOR and others regulate autophagy in prostate cancer. Anti-tumor compounds, for instance phytochemicals, dually inhibit or induce autophagy in prostate cancer therapy. For improving prostate cancer therapy, nanotherapeutics such as chitosan nanoparticles have been developed. With respect to the context-dependent role of autophagy in prostate cancer, genetic tools such as siRNA and CRISPR-Cas9 can be utilized for targeting autophagic genes. Finally, these findings can be translated into preclinical and clinical studies to improve survival and prognosis of prostate cancer patients.

• Prostate cancer is among the leading causes of death in men where targeting autophagy is of importance in treatment;

• Autophagy governs proliferation and metastasis capacity of prostate cancer cells;

• Autophagy modulation is of interest in improving the therapeutic response of prostate cancer cells;

• Molecular pathways, especially involving non-coding RNAs, regulate autophagy in prostate cancer;

• Autophagy possesses both diagnostic and prognostic roles in prostate cancer, with promises for clinical application.

Autophagy in Tumor Immunity and Viral-Based Immunotherapeutic Approaches in Cancer

Autophagy is a fundamental catabolic process essential for the maintenance of cellular and tissue homeostasis, as well as directly contributing to the control of invading pathogens. Unsurprisingly, this process becomes critical in supporting cellular dysregulation that occurs in cancer, particularly the tumor microenvironments and their immune cell infiltration, ultimately playing a role in responses to cancer therapies. Therefore, understanding "cancer autophagy" could help turn this cellular waste-management service into a powerful ally for specific therapeutics. For instance, numerous regulatory mechanisms of the autophagic machinery can contribute to the anti-tumor properties of oncolytic viruses (OVs), which comprise a diverse class of replication-competent viruses with potential as cancer immunotherapeutics. In that context, autophagy can either: promote OV anti-tumor effects by enhancing infectivity and replication, mediating oncolysis, and inducing autophagic and immunogenic cell death; or reduce OV cytotoxicity by providing survival cues to tumor cells. These properties make the catabolic process of autophagy an attractive target for therapeutic combinations looking to enhance the efficacy of OVs. In this article, we review the complicated role of autophagy in cancer initiation and development, its effect on modulating OVs and immunity, and we discuss recent progress and opportunities/challenges in targeting autophagy to enhance oncolytic viral immunotherapy.

Enhancing Therapeutic Efficacy of Oncolytic Herpes Simplex Virus with MEK Inhibitor Trametinib in Some BRAF or KRAS-Mutated Colorectal or Lung Carcinoma Models

Oncolytic virus (OV) as a promising therapeutic agent can selectively infect and kill tumor cells with naturally inherited or engineered properties. Considering the limitations of OVs monotherapy, combination therapy has been widely explored. MEK inhibitor (MEKi) Trametinib is an FDA-approved kinase inhibitor indicated for the treatment of tumors with BRAF V600E or V600K mutations. In this study, the oncolytic activity in vitro and anti-tumor therapeutic efficacy in vivo when combined with oHSV and MEKi Trametinib were investigated. We found: (1) Treatment with MEKi Trametinib augmented oHSV oncolytic activity in BRAF V600E-mutated tumor cells. (2) Combination treatment with oHSV and MEKi Trametinib enhanced virus replication mediated by down-regulation of STAT1 and PKR expression or phosphorylation in BRAF V600E-mutated tumor cells as well as BRAF wt/KRAS-mutated tumor cells. (3) A remarkably synergistic therapeutic efficacy was shown in vivo for BRAF wt/KRAS-mutated tumor models, when a combination of oHSV including PD-1 blockade and MEK inhibition. Collectively, these data provide some new insights for clinical development of combination therapy with oncolytic virus, MEK inhibition, and checkpoint blockade for BRAF or KRAS-mutated tumors.

Oncolytic Virus-Induced Autophagy in Glioblastoma

Simple Summary

Glioblastoma (GBM) is the most common and aggressive brain tumor with an incidence rate of nearly 3.19/100,000. Current therapeutic options fall short in improving the survival of patients with GBM. Various genetic and microenvironmental factors contribute to GBM progression and resistance to therapy. The development of gene therapies using self-replicating oncolytic viruses can advance GBM treatment. Due to GBM heterogeneity, oncolytic viruses have been genetically modified to improve the antiglioma effect in vitro and in vivo. Oncolytic viruses can activate autophagy signaling in GBM upon tumoral infection. Autophagy can be cytoprotective, whereby the GBM cells catabolize damaged organelles to accommodate to virus-induced stress, or cytotoxic, whereby it leads to the destruction of GBM cells. Understanding the molecular mechanisms that control oncolytic virus-induced autophagic signaling in GBM can fuel further development of novel and more effective genetic vectors.

Abstract

Autophagy is a catabolic process that allows cells to scavenge damaged organelles and produces energy to maintain cellular homeostasis. It is also an effective defense method for cells, which allows them to identify an internalized pathogen and destroy it through the fusion of the autophagosome and lysosomes. Recent reports have demonstrated that various chemotherapeutic agents and viral gene therapeutic vehicles provide therapeutic advantages for patients with glioblastoma as monotherapy or in combination with standards of care. Despite nonstop efforts to develop effective antiglioma therapeutics, tumor-induced autophagy in some studies manifests tumor resistance and glioma progression. Here, we explore the functional link between autophagy regulation mediated by oncolytic viruses and discuss how intracellular interactions control autophagic signaling in glioblastoma. Autophagy induced by oncolytic viruses plays a dual role in cell death and survival. On the one hand, autophagy stimulation has mostly led to an increase in cytotoxicity mediated by the oncolytic virus, but, on the other hand, autophagy is also activated as a cell defense mechanism against intracellular pathogens and modulates antiviral activity through the induction of ER stress and unfolded protein response (UPR) signaling. Despite the fact that the moment of switch between autophagic prosurvival and prodeath modes remains to be known, in the context of oncolytic virotherapy, cytotoxic autophagy is a crucial mechanism of cancer cell death.

Metabolome-Driven Regulation of Adenovirus-Induced Cell Death

A viral infection that involves virus invasion, protein synthesis, and virion assembly is typically accompanied by sharp fluctuations in the intracellular levels of metabolites. Under certain conditions, dramatic metabolic shifts can result in various types of cell death. Here, we review different types of adenovirus-induced cell death associated with changes in metabolic profiles of the infected cells. As evidenced by experimental data, in most cases changes in the metabolome precede cell death rather than represent its consequence. In our previous study, the induction of autophagic cell death was observed following adenovirus-mediated lactate production, acetyl-CoA accumulation, and ATP release, while apoptosis was demonstrated to be modulated by alterations in acetate and asparagine metabolism. On the other hand, adenovirus-induced ROS production and ATP depletion were demonstrated to play a significant role in the process of necrotic cell death. Interestingly, the accumulation of ceramide compounds was found to contribute to the induction of all the three types of cell death mentioned above. Eventually, the characterization of metabolite analysis could help in uncovering the molecular mechanism of adenovirus-mediated cell death induction and contribute to the development of efficacious oncolytic adenoviral vectors.

Crosstalk between oncolytic viruses and autophagy in cancer therapy

Oncolytic viruses have attracted attention as a promising strategy in cancer therapy owing to their ability to selectively infect and kill tumor cells, without affecting healthy cells. They also exert their anti-tumor effects by releasing immunostimulatory molecules from dying cancer cells. Several regulatory mechanisms, such as autophagy, contribute to the anti-tumor properties of oncolytic viruses. Autophagy is a conserved catabolic process in responses to various stresses, such as nutrient deprivation, hypoxia, and infection that produces energy by lysosomal degradation of intracellular contents. Autophagy can support infectivity and replication of the oncolytic virus and enhance their anti-tumor effects via mediating oncolysis, autophagic cell death, and immunogenic cell death. On the other hand, autophagy can reduce the cytotoxicity of oncolytic viruses by providing survival nutrients for tumor cells. In his review, we summarize various types of oncolytic viruses in clinical trials, their mechanism of action, and autophagy machinery. Furthermore, we precisely discuss the interaction between oncolytic viruses and autophagy in cancer therapy and their combinational effects on tumor cells.

Kinase inhibitors with viral oncolysis: Unmasking pharmacoviral approaches for cancer therapy

There are more than 500 kinases in the human genome, many of which are oncogenic once constitutively activated. Fortunately, numerous hyperactive kinases are druggable, and several targeted small molecule kinase inhibitors have demonstrated impressive clinical benefits in cancer treatment. However, their often cytostatic rather than cytotoxic effect on cancer cells, and the development of resistance mechanisms, remain significant limitations to these targeted therapies. Oncolytic viruses are an emerging class of immunotherapeutic agents with a specific oncotropic nature and excellent safety profile, highlighting them as a promising alternative to conventional therapeutic modalities. Nonetheless, the clinical efficacy of oncolytic virotherapy is challenged by immunological and physical barriers that limit viral delivery, replication, and spread within tumours. Several of these barriers are often associated with oncogenic kinase activity and, in some cases, worsened by the action of oncolytic viruses on kinase signaling during infection. What if inhibiting these kinases could potentiate the cancer-lytic and anti-tumour immune stimulating properties of oncolytic virotherapies? This could represent a paradigm shift in the use of specific kinase inhibitors in the clinic and provide a novel therapeutic approach to the treatment of cancers. A phase III clinical trial combining the oncolytic Vaccinia virus Pexa-Vec with the kinase inhibitor Sorafenib was initiated. While this trial failed to show any benefits over Sorafenib monotherapy in patients with advanced liver cancer, several pre-clinical studies demonstrate that targeting kinases combined with oncolytic viruses have synergistic effects highlighting this strategy as a unique avenue to cancer therapy. Herein, we review the combinations of oncolytic viruses with kinase inhibitors reported in the literature and discuss the clinical opportunities that represent these pharmacoviral approaches.

Virotherapy: From single agents to combinatorial treatments

Virotherpay is emerging as a promising strategy against cancer, and three oncolytic viruses (OVs) have gained approval in different countries for the treatment of several cancer types. Beyond the capability to selectively infect, replicate and lyse cancer cells, OVs act through a multitude of events, including modification of the tumour micro/macro-environment as well as a complex modulation of the anti-tumour immune response by activation of danger signals and immunogenic cell death pathways. Most OVs show limited effects, depending on the viral platform and the interactions with the host. OVs used as monotherapy only in a minority of patients elicited a full response. Better outcomes were obtained using OVs in combination with other treatments, such as immune therapy or chemotherapy, suggesting that the full potential of OVs can be unleashed in combination with other treatment modalities. Here, we report the main described combination of OVs with conventional chemotherapeutic agents: platinum salts, mitotic inhibitors, anthracyclines and other antibiotics, anti-metabolites, alkylating agents and topoisomerase inhibitors. Additionally, our work provides an overview of OV combination with targeted therapies: histone deacetylase inhibitors, kinase inhibitors, monoclonal antibodies, inhibitors of DNA repair, inhibitors of the proteasome complex and statins that demonstrated enhanced OV anti-neoplastic activity. Although further studies are required to assess the best combinations to translate the results in the clinic, it is clear that combined therapies, acting with complementary mechanisms of action might be useful to target cancer lesions resistant to currently available treatments.

MEK inhibition enhances oncolytic virus immunotherapy through increased tumor cell killing and T cell activation

Melanoma is an aggressive cutaneous malignancy, but advances over the past decade have resulted in multiple new therapeutic options, including molecularly targeted therapy, immunotherapy, and oncolytic virus therapy. Talimogene laherparepvec (T-VEC) is a herpes simplex type 1 oncolytic virus, and trametinib is a MEK inhibitor approved for treatment of melanoma. Therapeutic responses with T-VEC are often limited, and BRAF/MEK inhibition is complicated by drug resistance. We observed that the combination of T-VEC and trametinib resulted in enhanced melanoma cell death in vitro. Further, combination treatment resulted in delayed tumor growth and improved survival in mouse models. Tumor regression was dependent on activated CD8⁺ T cells and Batf3⁺ dendritic cells. We also observed antigen spreading and induction of an inflammatory gene signature, including increased expression of PD-L1. Triple therapy with the combination of T-VEC, MEK inhibition, and anti-PD-1 antibody further augmented responses. These data support clinical development of combination oncolytic viruses, MEK inhibitors, and checkpoint blockade in patients with melanoma.

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

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

Sensitisation to mitoxantrone-induced apoptosis by the oncolytic adenovirus Ad∆∆ through Bcl-2-dependent attenuation of autophagy

Anti-apoptotic Bcl-2 is frequently activated in human malignant cells to promote cell survival and inhibit cell death. Replication-selective oncolytic adenoviruses deleted in the functional Bcl-2 homologue E1B19K potently synergise with apoptosis-inducing chemotherapeutic drugs, including mitoxantrone for prostate cancer. Here, we demonstrate that our previously generated oncolytic mutant Ad∆∆ (E1B19K- and E1ACR2-deleted) caused potent synergistic apoptotic cell death in both drug-sensitive 22Rv1, and drug-insensitive PC3 and PC3M prostate cancer cells. The synergistic cell killing was dependent on Bcl-2 expression and was prevented by Bcl-2 knockdown, which led to activation of the autophagy pathway. Mitoxantrone-induced autophagy, which was decreased in combination with Ad∆∆-infection resulting in increased apoptosis. Expression of the viral E1A12S protein alone mimicked the synergistic effects with Ad∆∆ in combination with mitoxantrone while intact wild-type virus (Ad5) had no effect. Early and late-stage inhibition of autophagy by Atg7 knockdown and chloroquine respectively, promoted apoptotic cell killing with mitoxantrone similar to Ad∆∆. These findings revealed currently unexplored actions of E1B19K-deleted oncolytic adenoviruses and the central role of Bcl-2 in the synergistic cell killing. This study suggests that cancers with functional Bcl-2 expression may be selectively re-sensitised to drugs by Ad∆∆.

Targeting Autophagy for Oncolytic Immunotherapy

Oncolytic viruses (OVs) are capable of exerting anti-cancer effects by a variety of mechanisms, including immune-mediated tumor cell death, highlighting their potential use in immunotherapy. Several adaptation mechanisms such as autophagy contribute to OV-mediated anti-tumor properties. Autophagy regulates immunogenic signaling during cancer therapy which can be utilized to design therapeutic combinations using approaches that either induce or block autophagy to potentiate the therapeutic efficacy of OVs. In this article, we review the complicated interplay between autophagy, cancer, immunity, and OV, summarize recent progress in the contribution of OV-perturbed autophagy to oncolytic immunity, and discuss the challenges in targeting autophagy to enhance oncolytic immunotherapy.

The intersection between viral oncolysis, drug resistance, and autophagy

Resistance to both cytotoxic and targeted therapies is a major problem facing cancer treatment. The mechanisms of resistance to unrelated drugs share many common features, including up-regulation of detoxifying pathways, activation of pro-survival mechanisms, and ineffective induction of cell death. Oncolytic viruses (OVs) are promising biotherapeutics for cancer treatment that specifically replicate in and lyse cancer cells. In addition to direct viral lysis, the anti-tumor effects of OVs are mediated via innate and adaptive immune responses, and several adaptation mechanisms such as autophagy appear to contribute to their anti-tumor properties. Autophagy is a versatile pathway that plays a key role in cancer survival during stressful conditions such as starvation or cytotoxic drug challenges. Autophagy also plays a role in mediating innate and adaptive immune responses by contributing to antigen presentation and cytokine secretion. This role of autophagy in regulation of immune responses can be utilized to design therapeutic combinations using approaches that either stimulate or block autophagy to potentiate therapeutic efficacy of OVs. Additional studies are needed to determine optimal multimodal combination approaches that will facilitate future successful clinical implementation of OV-based therapies.

Altered expression of autophagy-related genes might contribute to glucocorticoid resistance in precursor B-cell-type acute lymphoblastic leukemia

OBJECTIVES

Autophagy is an evolutionarily conserved process playing an important role in tumor cell's resistance to chemotherapy. Response to glucocorticoid (GC) treatment is out of the most important prognostic factors in childhood acute lymphoblastic leukemia (ALL); however, only few data are available connecting GC response and role of autophagy. Our aim was to investigate whether altered expression of autophagy-related genes contributes to GC-resistant phenotype in GC-sensitive and GC-resistant precursor B-cell-type (PBC) ALL cells.

METHODS

Gene expression data were obtained from public database for 26 children diagnosed with PBC ALL either sensitive or resistant to in vitro prednisolone treatment.

RESULTS

We have identified 36 autophagy-associated genes which were differently expressed, based on at least a twofold difference, GC-sensitive group as compared to GC-resistant one. Of the 36 genes, 10 were downregulated and 26 upregulated in the GC-resistant group. The average fold change values for the decreased and increased transcripts were -4.57 and 2.67, respectively.

CONCLUSIONS

Our data imply that GC sensitivity might depend on the expression of several genes involved in regulation and execution of autophagy in a way that key autophagy inducers are downregulated while inhibitors of autophagy are upregulated in GC-resistant cells.

The oncolytic virus dl922-947 reduces IL-8/CXCL8 and MCP-1/CCL2 expression and impairs angiogenesis and macrophage infiltration in anaplastic thyroid carcinoma

Anaplastic thyroid carcinoma (ATC) is one of the most aggressive human solid tumor and current treatments are ineffective in increasing patients' survival. Thus, the development of new therapeutic approaches for ATC is needed. We have previously shown that the oncolytic adenovirus dl922-947 induces ATC cell death in vitro and tumor regression in vivo. However, the impact of dl922-947 on the pro-tumorigenic ATC microenvironment is still unknown. Since viruses are able to regulate cytokine and chemokine production from infected cells, we sought to investigate whether dl922-947 virotherapy has such effect on ATC cells, thereby modulating ATC microenvironment. dl922-947 decreased IL-8/CXCL8 and MCP-1/CCL2 production by the ATC cell lines 8505-c and BHT101-5. These results correlated with dl922-947-mediated reduction of NF-κB p65 binding to IL8 promoter in 8505-c and BHT101-5 cells and CCL2 promoter in 8505-c cells. IL-8 stimulates cancer cell proliferation, survival and invasion, and also angiogenesis. dl922-947-mediated reduction of IL-8 impaired ATC cell motility in vitro and ATC-induced angiogenesis in vitro and in vivo. We also show that dl922-947-mediated reduction of the monocyte-attracting chemokine CCL2 decreased monocyte chemotaxis in vitro and tumor macrophage density in vivo. Interestingly, dl922-947 treatment induced the switch of tumor macrophages toward a pro-inflammatory M1 phenotype, likely by increasing the expression of the pro-inflammatory cytokine interferon-γ. Altogether, we demonstrate that dl922-947 treatment re-shape the pro-tumorigenic ATC microenvironment by modulating cancer-cell intrinsic factors and the immune response. An in-depth knowledge of dl922-947-mediated effects on ATC microenvironment may help to refine ATC virotherapy in the context of cancer immunotherapy.

Eradication of metastatic melanoma through cooperative expression of RNA-based HDAC1 inhibitor and p73 by oncolytic adenovirus

Malignant melanoma is a highly aggressive cancer that retains functional p53 and p73, and drug unresponsiveness largely depends on defects in death pathways after epigenetic gene silencing in conjunction with an imbalanced p73/DNp73 ratio. We constructed oncolytic viruses armed with an inhibitor of deacetylation and/or p73 to specifically target metastatic cancer. Arming of the viruses is aimed at lifting epigenetic blockage and re-opening apoptotic programs in a staggered manner enabling both, efficient virus replication and balanced destruction of target cells through apoptosis. Our results showed that cooperative expression of shHDAC1 and p73 efficiently enhances apoptosis induction and autophagy of infected cells which reinforces progeny production. In vitro analyses revealed 100% cytotoxicity after infecting cells with OV.shHDAC1.p73 at a lower virus dose compared to control viruses. Intriguingly, OV.shHDAC1.p73 acts as a potent inhibitor of highly metastatic xenograft tumors in vivo. Tumor expansion was significantly reduced after intratumoral injection of 3 × 10⁸ PFU of either OV.shHDAC1 or OV.p73 and, most important, complete regression could be achieved in 100% of tumors treated with OV.shHDAC1.p73. Our results point out that the combination of high replication capacity and simultaneous restoration of cell death routes significantly enhance antitumor activity.

Inhibition of Autophagy Potentiated the Antitumor Effect of Nedaplatin in Cisplatin-Resistant Nasopharyngeal Carcinoma Cells

Nedaplatin, a cisplatin analog, was developed to reduce the toxicity of cisplatin, whereas it can be cross-resistant with cisplatin in some circumstances. This study aimed to investigate the role of autophagy in nedaplatin induced cell death in cisplatin-resistant nasopharyngeal carcinoma cells. Here, we showed that HNE1/DDP and CNE2/DDP cells were resistant to nedaplatin-induced cell death with reduced apoptotic activity. Nedaplatin treatment resulted in autophagosome accumulation and increased expression of LC3-II, indicating the induction of autophagy by nedaplatin in HNE1/DDP and CNE2/DDP cells. Inhibition of autophagy by Bafilomycin A1 (Baf A1) and 3-Methyladenine (3-MA) remarkably enhanced the antitumor efficacy of nedaplatin in HNE1/DDP and CNE2/DDP cells, suggesting that the resistance to nedaplatin-induced cell death was caused by enhanced autophagy in nedaplatin-resistant NPC cells. Additionally, Baf A1 enhanced reactive oxygen species (ROS) generation and apoptosis induced by nedaplatin in HNE1/DDP cells. Mechanistically, nedaplatin treatment caused activation of ERK1/2 and suppression of Akt/mTOR signaling pathways. While inhibition of ERK1/2 by MEK1/2 inhibitor, U0126, could reduce the expression of LC3-II in nedaplatin-resistant NPC cells. Furthermore, suppression of ROS could inhibit nedaplatin-induced ERK activation in HNE1/DDP cells, indicating that ROS and ERK were involved in nedaplatin-induced autophagy. Together, these findings suggested that autophagy played a cytoprotective role in nedaplatin-induced cytotoxicity of HNE1/DDP and CNE2/DDP cells. Furthermore, our results highlighted a potential approach to restore the sensitivity of cisplatin-resistant nasopharyngeal cancer cells to nedaplatin in combination with autophagy inhibitors.

Inactivated Sendai virus induces apoptosis and autophagy via the PI3K/Akt/mTOR/p70S6K pathway in human non-small cell lung cancer cells

Inactivated Sendai virus (HVJ-E) has shown potential anticancer efficacy in various cancer cells. However, the ability of HVJ-E to regulate cancer cell survival and death remains largely unknown. In the present study we first found that HVJ-E exhibited cytotoxic effects in the non-small cell lung cancer cell (NSCLC) line A549 and cisplatin-resistant A549 cells (A549/DDP). The suppression of cell viability was due to both the activation of caspases and the JNK and p38 MAPK signaling pathways in A549 and A549/DDP human lung cancer cells. In addition, we demonstrated that HVJ-E could induce autophagy in NSCLC cells via the PI3K/Akt/mTOR/p70S6K signaling pathway for the first time. Inhibiting autophagy in A549/DDP cells and inducing autophagy in A549 cells enhanced HVJ-E-induced apoptosis. These findings provide a molecular basis of HVJ-E-mediated cell death and support the notion that combination treatment with autophagy modulators is an effective strategy to augment the cytotoxic effects of HVJ-E in NSCLC cells.

PARP inhibitor olaparib increases the oncolytic activity of dl922-947 in in vitro and in vivo model of anaplastic thyroid carcinoma

PARP inhibitors are mostly effective as anticancer drugs in association with DNA damaging agents. We have previously shown that the oncolytic adenovirus dl922-947 induces extensive DNA damage, therefore we hypothesized a synergistic antitumoral effect of the PARP inhibitor olaparib in association with dl922-947. Anaplastic thyroid carcinoma was chosen as model since it is a particularly aggressive tumor and, because of its localized growth, it is suitable for intratumoral treatment with oncolytic viruses. Here, we show that dl922-947 infection induces PARP activation, and we confirm in vitro and in vivo that PARP inhibition increases dl922-947 replication and oncolytic activity. In vitro, the combination with olaparib exacerbates the appearance of cell death markers, such as Annexin V positivity, caspase 3 cleavage, cytochrome C release and propidium iodide permeability. In vivo, we also observed a better viral distribution upon PARP inhibition. Changes in CD31 levels suggest a direct effect of olaparib on tumor vascularization and on the viral distribution within the tumor mass. The observation that PARP inhibition enhances the effects of dl922-947 is highly promising not only for the treatment of anaplastic thyroid carcinoma but, in general, for the treatment of other tumors that could benefit from the use of oncolytic viruses.

Pharmacological modulation of autophagy enhances Newcastle disease virus-mediated oncolysis in drug-resistant lung cancer cells

Background

Oncolytic viruses represent a promising therapy against cancers with acquired drug resistance. However, low efficacy limits its clinical application. The objective of this study is to investigate whether pharmacologically modulating autophagy could enhance oncolytic Newcastle disease virus (NDV) strain NDV/FMW virotherapy of drug-resistant lung cancer cells.

Methods

The effect of NDV/FMW infection on autophagy machinery in A549 lung cancer cell lines resistant to cisplatin (A549/DDP) or paclitaxel (A549/PTX) was investigated by detection of GFP-microtubule-associated protein 1 light chain 3 (GFP-LC3) puncta, formation of double-membrane vesicles and conversion of the nonlipidated form of LC3 (LC3-I) to the phosphatidylethanolamine-conjugated form (LC3-II). The effects of autophagy inhibitor chloroquine (CQ) and autophagy inducer rapamycin on NDV/FMW-mediated antitumor activity were evaluated both in culture cells and in mice bearing drug-resistant lung cancer cells.

Results

We show that NDV/FMW triggers autophagy in A549/PTX cells via dampening the class I PI3K/Akt/mTOR/p70S6K pathway, which inhibits autophagy. On the contrary, NDV/FMW infection attenuates the autophagic process in A549/DDP cells through the activation of the negative regulatory pathway. Furthermore, combination with CQ or knockdown of ATG5 significantly enhances NDV/FMW-mediated antitumor effects on A549/DDP cells, while the oncolytic efficacy of NDV/FMW in A549/PTX cells is significantly improved by rapamycin. Interestingly, autophagy modulation does not increase virus progeny in these drug resistant cells. Importantly, CQ or rapamycin significantly potentiates NDV/FMW oncolytic activity in mice bearing A549/DDP or A549/PTX cells respectively.

Conclusions

These results demonstrate that combination treatment with autophagy modulators is an effective strategy to augment the therapeutic activity of NDV/FMW against drug-resistant lung cancers.

Chemotherapy and Oncolytic Virotherapy: Advanced Tactics in the War against Cancer

Cancer is a traitorous archenemy that threatens our survival. Its ability to evade detection and adapt to various cancer therapies means that it is a moving target that becomes increasingly difficult to attack. Through technological advancements, we have developed sophisticated weapons to fight off tumor growth and invasion. However, if we are to stand a chance in this war against cancer, advanced tactics will be required to maximize the use of our available resources. Oncolytic viruses (OVs) are multi-functional cancer-fighters that can be engineered to suit many different strategies; in particular, their retooling can facilitate increased capacity for direct tumor killing (oncolytic virotherapy) and elicit adaptive antitumor immune responses (oncolytic immunotherapy). However, administration of these modified OVs alone, rarely induces successful regression of established tumors. This may be attributed to host antiviral immunity that acts to eliminate viral particles, as well as the capacity for tumors to adapt to therapeutic selective pressure. It has been shown that various chemotherapeutic drugs with distinct functional properties can potentiate the antitumor efficacy of OVs. In this review, we summarize the chemotherapeutic combinatorial strategies used to optimize virally induced destruction of tumors. With a particular focus on pharmaceutical immunomodulators, we discuss how specific therapeutic contexts may alter the effects of these synergistic combinations and their implications for future clinical use.

Association of oncolytic adenoviruses with chemotherapies: an overview and future directions

Oncolytic adenoviruses have been used in different preclinical and clinical studies, showing their capacity to kill tumor cells without major adverse events. However, these studies also underline the limitations of this approach. The efficacy of oncolytic adenoviruses is hampered by their limited ability to transduce some tumor types, their lack of selectivity, and their poor dissemination within tumors. In addition, the host immune response may limit oncolytic adenovirus efficacy. Combining oncolytic adenoviruses with chemotherapeutics constitutes an appealing strategy to increase their potency. The first part of this review describes the molecular basis of oncolytic adenoviruses, their use in preclinical studies and clinical trials, their limitations, and strategies to circumvent these limitations. The second part will focus on studies combining oncolytic adenoviruses with chemotherapeutic drugs, including standard chemotherapeutic drugs, molecularly targeted drugs, and other drugs that have been combined with oncolytic adenoviruses. Finally, based on these studies, we describe future directions and general rules that could be followed to identify chemotherapeutic drugs displaying additive/synergistic effects when combined with oncolytic adenoviruses.

Increased 8-hydroxydeoxyguanosine in high-grade gliomas is associated with activation of autophagy

AIM OF THE STUDY

To understand the interaction between oxidative stress and autophagy in gliomas of different grades.

MATERIALS AND METHODS

In the present study, we analyzed levels of oxidative stress in 45 human glioma tumors, using the DNA oxidation marker 8-hydroxydeoxyguanosine (8-OHdG). In addition, we determined activation of autophagy in gliomas samples by assessing expression of microtubule-associated protein 1 light chain-3B (LC3B). To confirm our in vivo findings, in vitro studies using U87 cells were conducted.

RESULTS

It was determined that the grade of gliomas, that is, different malignant degrees according to WHO classification, significantly affected level of 8-OHdG. High levels of 8-OHdG were present in high-grade gliomas. This trend was significant in male patients and in young adult patients (<50 years old). Further study showed increased expression of LC3B in high-grade gliomas. In addition, levels of 8-OHdG and expression of LC3B were positively correlated. Reducing autophagic activity by 3-methyladenine resulted in significantly increased intracellular reactive oxygen species (ROS) in U87 cells.

CONCLUSIONS

Our study provides evidence that high levels of oxidative stress in high-grade gliomas are associated with autophagy activation that may play a protective role promoting the survival of high-grade gliomas under severe oxidative stress.

The interplay of reovirus with autophagy

Autophagy participates in multiple fundamental physiological processes, including survival, differentiation, development, and cellular homeostasis. It eliminates cytoplasmic protein aggregates and damaged organelles by triggering a series of events: sequestering the protein substrates into double-membrane vesicles, fusing the vesicles with lysosomes, and then degrading the autophagic contents. This degradation pathway is also involved in various disorders, for instance, cancers and infectious diseases. This paper provides an overview of modulation of autophagy in the course of reovirus infection and also the interplay of autophagy and reovirus.

Ionizing radiation enhances dl922-947-mediated cell death of anaplastic thyroid carcinoma cells

dl922-947 is an oncolytic adenovirus potentially suitable for the treatment of aggressive localized tumors, such as anaplastic thyroid carcinoma (ATC). In this study, we have analyzed the effects of dl922-947 in combination with ionizing radiations, testing different schedules of administration and observing synergistic effects only when ATC cells were irradiated 24 h prior to viral infection. Cells undergoing combined treatment exhibited a marked increase in cell death and viral replication, suggesting that irradiation blocks cells in a more permissive state for viral life cycle. We also show that dl922-947 triggers a DNA damage response, characterized by mobilization of the MRN complex (composed by Mre11-Rad50-Nbs1), accumulation of γH2AX, and activation of the checkpoint kinases ataxia telangiectasia mutated (ATM) and Chk1. Based on these observations, we speculate that the DNA damage response acts as a cellular protective mechanism to hinder viral infection and replication. To confirm this hypothesis, we demonstrate that the ATM inhibitor KU55933 increased the oncolytic activity of dl922-947 and its replication. Finally, we validate the potential therapeutic use of this approach by showing in vivo that the combined treatment slows tumor xenograft growth more potently than either irradiation or infection alone.

Targeting autophagy to enhance oncolytic virus-based cancer therapy

INTRODUCTION

Autophagy is a conserved catabolic process crucial in maintaining cellular homeostasis. On infection, oncolytic viruses (OVs) perturb the cellular autophagy machinery in infected tumor cells both in vitro and in vivo. Currently, pharmacological modulation of autophagy in OV-infected tumor cells has been shown to augment OV-mediated antitumor effects in preclinical studies. Combination of OVs with autophagy modulators can, therefore, have many potential applications in the future research on targeting autophagy and novel anticancer therapies.

AREAS COVERED

This review provides a detailed description of known interactions between OVs and autophagy and summarizes the roles of autophagy in OV replication and cell lysis. The recent literature on targeting autophagy with either the autophagy inducers, such as rapamycin, or autophagy inhibitors, such as chloroquine, to increase OV-induced cytotoxicity is reviewed to help researchers in further investigations. The major challenge for investigators is to understand the molecular mechanism underlying the interplay between OV and the autophagy machinery and its effect on oncolysis.

EXPERT OPINION

Targeting the cellular autophagy machinery could be explored as a new therapeutic strategy to enhance OV-mediated antitumor effects in the future.

Oncolytic virotherapy with modified adenoviruses and novel therapeutic targets

INTRODUCTION

Numerous oncolytic viral mutants derived from a variety of strains have antitumor efficacy with limited or no toxicity to normal tissue. While all modes of administration were determined to be safe in patients with solid cancers refractory to current standard of care, this therapeutic approach requires further improvements to achieve definite efficacy.

AREAS COVERED

We review the most promising clinical developments with several oncolytic viruses. The focus is on preclinical and clinical findings with replication-selective adenoviral mutants including ONYX-015, H101 and Ad5ΔCR mutants that, to date, are the most studied oncolytic viruses. Cellular pathways reported to play a role in virus-induced cell killing are reviewed as potential targets for the development of more effective combinatorial therapies.

EXPERT OPINION

The most promising clinical outcomes for metastatic cancers have been reported for oncolytic vaccinia and herpes virus mutants expressing the cytokine GMCSF. However, highly efficacious and selective adenoviral mutants have been developed that interact synergistically with cytotoxic drugs in model systems. We anticipate that by delineating the cellular targets for synergistic cancer cell killing in response to adenoviral mutants and drugs such as apoptosis and autophagy signaling, greatly improved anticancer therapies will result in the near future.