Interferon-β-armed oncolytic adenovirus induces both apoptosis and necroptosis in cancer cells

Rotavirus non-structural protein 4 usurps host cellular RIPK1-RIPK3 complex to induce MLKL-dependent necroptotic cell death

The dynamic interface between invading viral pathogens and programmed cell death (PCD) of the host is a finely regulated process. Host cellular demise at the end of the viral life cycle ensures the release of progeny virions to initiate new infection cycles. Rotavirus (RV), a diarrheagenic virus with double-stranded RNA genome, has been reported to trigger different types of PCD such as apoptosis and pyroptosis in a highly regulated way to successfully disseminate progeny virions. Recently our lab also showed that induction of MLKL-driven programmed necroptosis by RV. However, the host cellular machinery involved in RV-induced necroptosis and the upstream viral trigger responsible for it remained unaddressed. In the present study, the signalling upstream of MLKL-driven necroptosis has been delineated where the involvement of Receptor interacting serine/threonine kinase 3 (RIPK3) and 1 (RIPK1) from the host side and RV non-structural protein 4 (NSP4) as the viral trigger for necroptosis has been shown. Interestingly, RV-NSP4 was found to be an integral component of the necrosome complex by interacting with RIPK1, thereby bypassing the requirement of RIPK1 kinase activity. Subsequently, NSP4-driven elevated cytosolic Ca2+ concentration and Ca2+-binding to NSP4 lead further to RHIM domain-dependent RIPK1-RIPK3 interaction, RIPK3-dependent MLKL phosphorylation, and eventual necroptosis. Overall, this study presents the interplay between RV-NSP4 and the host cellular necrosome complex to induce necroptotic death of host cells.

Construction and application of adenoviral vectors

Adenoviral vectors have been widely used as vaccine candidates or potential vaccine candidates against infectious diseases due to the convenience of genome manipulation, their ability to accommodate large exogenous gene fragments, easy access of obtaining high-titer of virus, and high efficiency of transduction. At the same time, adenoviral vectors have also been used extensively in clinical research for cancer gene therapy and treatment of diseases caused by a single gene defect. However, application of adenovirus also faces a series of challenges such as poor targeting, strong immune response against the vector itself, and they cannot be used repeatedly. It is believed that these problems will be solved gradually with further research and technological development in related fields. Here, we review the construction methods of adenoviral vectors, including "gutless" adenovirus and discuss application of adenoviral vectors as prophylactic vaccines for infectious pathogens and their application prospects as therapeutic vaccines for cancer and other kinds of chronic infectious disease such as human papillomavirus, hepatitis B virus, and hepatitis C virus.

Ruxolitinib altered IFN-β induced necroptosis of human dental pulp stem cells during osteoblast differentiation

OBJECTIVE

This study aimed to evaluate the role of ruxolitinib in the interferon beta (IFN-β) mediated osteoblast differentiation using human dental pulp stem cells (hDPSCs).

DESIGN

hDPSCs from five deciduous teeth of healthy patients were stimulated by adding human recombinant IFN-β protein (1 or 2 ng/ml) to the osteogenic differentiation induction medium. Substrate formation was determined using Alizarin Red staining, calcium concentration, and osteoblast marker expression levels. Ruxolitinib was used to inhibit the Janus kinase/signal transducers and activators of transcription (JAK-STAT) pathway. Apoptosis was detected using terminal deoxynucleotidyl nick-end labeling (TUNEL) staining, and necroptosis was detected using propidium iodide staining and phosphorylated mixed lineage kinase domain-like protein (pMLKL) expression.

RESULTS

In the IFN-β-treated group, substrate formation was inhibited by a reduction in alkaline phosphatase (ALP) expression in a concentration-dependent manner. Although the proliferation potency was unchanged between the IFN-β-treated and control groups, the cell number was significantly reduced in the experimental group. TUNEL-positive cell number was not significantly different; however, the protein level of necroptosis markers, interleukin-6 (IL-6) and pMLKL were significantly increased in the substrate formation. Cell number and ALP expression level were improved in the group administered ruxolitinib, a JAK-STAT inhibitor. Additionally, ruxolitinib significantly suppressed IL-6 and pMLKL levels.

CONCLUSION

Ruxolitinib interfered with the IFN-β-mediated necroptosis and osteogenic differentiation via the JAK-STAT pathway.

A Novel Necroptosis-Related lncRNA Signature for Predicting Prognosis and Immune Response of Glioma

Glioma is one of the most common intracranial malignancies that plagues people around the world. Despite current improvements in treatment, the prognosis of glioma is often unsatisfactory. Necroptosis is a form of programmed cell death. As research progresses, the role of necroptosis in tumors has gradually attracted the attention of researchers. And lncRNA is regarded as a critical role in the development of cancer. Therefore, this study is aimed at establishing a prognostic model based on necroptosis-associated lncRNAs to accurately assess the prognosis and immune response of patients with glioma. The RNA sequences of glioma patients and normal brain samples were downloaded from The Cancer Genome Atlas (TCGA) and GTEx databases, respectively. The coexpression analysis was performed to identify the necroptosis-related lncRNAs. Then, we utilized LASSO analysis following univariate Cox analysis to construct a prognostic model. Subsequently, we applied the Kaplan-Meier curve, time-dependent receiver operating characteristics (ROC), and univariate and multivariate Cox regression analyses to assess the effectiveness of this model. And the functional enrichment analyses and immune-related analyses were employed to investigate the potential biological functions. A validation set was obtained from the Chinese Glioma Genome Atlas (CGGA) database. And qRT-PCR was employed to further validate the expression levels of selected necroptosis-associated lncRNAs. Seven necroptosis-related lncRNAs (FAM13A-AS1, JMJD1C-AS1, LBX2-AS1, ZBTB20-AS4, HAR1A, SNHG14, and LINC00900) were determined to construct a prognostic model. The area under the ROC curve (AUC) was 0.871, 0.901, and 0.911 at 1, 2, and 3 years, respectively. The risk score was shown to be an important independent predictor in both univariate and multivariate Cox regression analyses. Through functional enrichment analyses, we found that the differentially expressed genes (DEGs) were mainly enriched in protein binding and signaling-related biological functions and immune-associated pathways. In conclusion, we established and validated a novel necroptosis-related lncRNA signature, which could accurately predict the overall survival of glioma patients and serve as potential therapeutic targets.

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.

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.

Role of tumor-associated neutrophils in regulation of tumor growth in lung cancer development: A mathematical model

Neutrophils display rapid and potent innate immune responses in various diseases. Tumor-associated neutrophils (TANs) however either induce or overcome immunosuppressive functions of the tumor microenvironment through complex tumor-stroma crosstalk. We developed a mathematical model to address the question of how phenotypic alterations between tumor suppressive N1 TANS, and tumor promoting N2 TANs affect nonlinear tumor growth in a complex tumor microenvironment. The model provides a visual display of the complex behavior of populations of TANs and tumors in response to various TGF-β and IFN-β stimuli. In addition, the effect of anti-tumor drug administration is incorporated in the model in an effort to achieve optimal anti-tumor efficacy. The simulation results from the mathematical model were in good agreement with experimental data. We found that the N2-to-N1 ratio (N21R) index is positively correlated with aggressive tumor growth, suggesting that this may be a good prognostic factor. We also found that the antitumor efficacy increases when the relative ratio (Dap) of delayed apoptotic cell death of N1 and N2 TANs is either very small or relatively large, providing a basis for therapeutically targeting prometastatic N2 TANs.

Newcastle disease virus V protein inhibits apoptosis in DF-1 cells by downregulating TXNL1

Many viral proteins are related to suppressing apoptosis in target cells and are hence beneficial to viral replication. The V protein of Newcastle disease virus (NDV) is one such protein that plays an important role in inhibiting apoptosis in a species-specific manner. However, to date, there have been no reports clarifying the antiapoptotic mechanisms of the V protein. The present study was undertaken to determine the apoptotic potential of the V protein in a chicken embryo fibroblast cell line (DF-1 cell) and to elucidate its molecular mechanisms of action. Here, a yeast two-hybrid system was used to screen the host proteins that interact with the V protein and identified thioredoxin-like protein 1 (TXNL1) as a potential binding partner. Immuno-colocalization of V protein and TXNL1 protein in DF-1 cells further verified the interaction of the two proteins. Through the overexpression of TXNL1 protein and knockdown of TXNL1 protein in DF-1 cells, the effects of NDV replication and cell apoptosis were examined. Cell apoptosis was detected by flow cytometry. The mRNA and protein expression levels of Bax, Bcl-2 and Caspase-3 were detected by quantitative real-time PCR (Q-PCR) and Western blotting. NDV expression was detected by Q-PCR and plaque assay. The results revealed that the TXNL1 protein induced apoptosis and inhibited NDV replication in DF-1 cells. Furthermore, the Western blot and Q-PCR results suggested that TXNL1 induced cell apoptosis through a pathway involving Bcl-2\Bax and Caspase-3. Finally, this work provides insight into the mechanism by which the V protein inhibits apoptosis.

Necroptosis in tumorigenesis, activation of anti-tumor immunity, and cancer therapy

While the mechanisms underlying apoptosis and autophagy have been well characterized over recent decades, another regulated cell death event, necroptosis, remains poorly understood. Elucidating the signaling networks involved in the regulation of necroptosis may allow this form of regulated cell death to be exploited for diagnosis and treatment of cancer, and will contribute to the understanding of the complex tumor microenvironment. In this review, we have summarized the mechanisms and regulation of necroptosis, the converging and diverging features of necroptosis in tumorigenesis, activation of anti-tumor immunity, and cancer therapy, as well as attempts to exploit this newly gained knowledge to provide therapeutics for cancer.

Silver nanoparticles of different sizes induce a mixed type of programmed cell death in human pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma, with the high resistance to chemotherapeutic agents, remains the fourth leading cause of cancer-death in the world. Due to the wide range of biological activity and unique properties, silver nanoparticles (AgNPs) are indicated as agents with potential to overcome barriers involved in chemotherapy failure. Therefore, in our study we decided to assess the ability of AgNPs to kill pancreatic cancer cells, and then to identify the molecular mechanism underlying this effect. Moreover, we evaluated the cytotoxicity of AgNPs against non-tumor cell of the same tissue (hTERT-HPNE cells) for comparison. Our results indicated that AgNPs with size of 2.6 and 18 nm decreased viability, proliferation and caused death of pancreatic cancer cells in a size- and concentration-dependent manner. Ultrastructural analysis identified that cellular uptake of AgNPs resulted in apoptosis, autophagy, necroptosis and mitotic catastrophe. These alterations were associated with increased pro-apoptotic protein Bax and decreased level of anti-apoptotic protein Bcl-2. Moreover, AgNPs significantly elevated the level of tumor suppressor p53 protein as well as necroptosis- and autophagy-related proteins: RIP-1, RIP-3, MLKL and LC3-II, respectively.

In addition, we found that PANC-1 cells were more vulnerable to AgNPs-induced cytotoxicity compared to pancreatic non-tumor cells.

In conclusion, AgNPs by inducing mixed type of programmed cell death in PANC-1 cells, could provide a new therapeutic strategy to overcome chemoresistance in one of the deadliest human cancer.

Sensitization of glycoengineered interferon-β1a-resistant cancer cells by cFLIP inhibition for enhanced anti-cancer therapy

In this study, we examined the molecular mechanism underlying the resistance of cancer cells to R27T, a glycoengineered version of recombinant human interferon (IFN)-β1a, and sought to overcome R27T resistance through combination therapy. R27T has been shown to induce anti-proliferation and apoptosis in human OVCAR-3 and MCF-7 cells, but not in HeLa cells. R27T treatment increased caspase-8 activity and the consequent cleavage of caspase-8 and -3 in R27T-sensitive OVCAR-3 cells, but not in R27T-resistant HeLa cells. Conversely, R27T increased the expression of cellular FLICE-like inhibitory protein (cFLIP) in HeLa cells, but not in OVCAR-3 cells. The sensitization of HeLa cells with cFLIP small interfering RNA or 4,5,6,7-tetrabromobenzotriazole (TBB, an inhibitor of casein kinase-2) facilitated R27T-induced caspase activation, and consequently apoptosis. In OVCAR-3-xenografted mice, intraperitoneal administration of R27T showed 2.1-fold higher anti-tumor efficacy than did the control vehicle. The combined administration of R27T and TBB showed the greatest anti-tumor effect in HeLa tumor-bearing mice, reducing the relative tumor volume by 35.7% compared to that in R27T-treated mice. Taken together, our results suggest that R27T has potential as an anti-cancer drug, and combination therapy with cFLIP inhibitors may be an effective strategy for overcoming R27T resistance.

Immunogenicity of oncolytic vaccinia viruses JX-GFP and TG6002 in a human melanoma in vitro model: studying immunogenic cell death, dendritic cell maturation and interaction with cytotoxic T lymphocytes

Oncolytic virotherapy is an emerging immunotherapeutic modality for cancer treatment. Oncolytic viruses with genetic modifications can further enhance the oncolytic effects on tumor cells and stimulate antitumor immunity. The oncolytic vaccinia viruses JX-594-GFP+/hGM-CSF (JX-GFP) and TG6002 are genetically modified by secreting granulocyte-macrophage colony-stimulating factor (GM-CSF) or transforming 5-fluorocytosine (5-FC) into 5-fluorouracil (5-FU). We compared their properties to kill tumor cells and induce an immunogenic type of cell death in a human melanoma cell model using SK29-MEL melanoma cells. Their influence on human immune cells, specifically regarding the activation of dendritic cells (DCs) and the interaction with the autologous cytotoxic T lymphocyte (CTL) clone, was investigated. Melanoma cells were infected with either JX-GFP or TG6002 alone or in combination with 5-FC and 5-FU. The influence of viral infection on cell viability followed a time- and multiplicity of infection dependent manner. Combination of virus treatment with 5-FU resulted in stronger reduction of cell viability. TG6002 in combination with 5-FC did not significantly strengthen the reduction of cell viability in this setting. Expression of calreticulin and high mobility group 1 protein (HMGB1), markers of immunogenic cell death (ICD), could be detected after viral infection. Accordingly, DC maturation was noted after viral oncolysis. DCs presented stronger expression of activation and maturation markers. The autologous CTL clone IVSB expressed the activation marker CD69, but viral treatment failed to enhance cytotoxicity marker. In summary, vaccinia viruses JX-GFP and TG6002 lyse melanoma cells and induce additional immunostimulatory effects to promote antitumor immune response. Further investigation in vivo is needed to consolidate the data.

Histone deacetylase inhibitor trichostatin A enhances the antitumor effect of the oncolytic adenovirus H101 on esophageal squamous cell carcinoma in vitro and in vivo

Replication-selective oncolytic virotherapy provides a novel modality to treat cancer by inducing cell death in tumor cells but not in normal cells. However, the utilization of oncolytic viruses as a stand-alone treatment is problematic due to their poor transduction efficiency in vivo. H101 was the first oncolytic adenovirus (Ads) to be approved by the Chinese FDA, and exhibits modest antitumor effects when applied as a single agent. The multiple histone deacetylase inhibitor trichostatin A (TSA) has been demonstrated to potently enhance the spread and replication of oncolytic Ads in several infection-resistant types of cancer. The present study aimed to investigate the antitumor effects of H101 in combination with TSA on esophageal squamous cell carcinoma (ESCC) in vitro and in vivo, and determine the mechanisms underlying these effects. H101 and TSA in combination increased the survival of mice harboring human ESCC cell line-tumor xenografts, as compared with mice treated with these agents individually. Therefore, TSA may enhance the antitumor effects of H101 in ESCC.

Spatiotemporally restricted arenavirus replication induces immune surveillance and type I interferon-dependent tumour regression

Immune-mediated effector molecules can limit cancer growth, but lack of sustained immune activation in the tumour microenvironment restricts antitumour immunity. New therapeutic approaches that induce a strong and prolonged immune activation would represent a major immunotherapeutic advance. Here we show that the arenaviruses lymphocytic choriomeningitis virus (LCMV) and the clinically used Junin virus vaccine (Candid#1) preferentially replicate in tumour cells in a variety of murine and human cancer models. Viral replication leads to prolonged local immune activation, rapid regression of localized and metastatic cancers, and long-term disease control. Mechanistically, LCMV induces antitumour immunity, which depends on the recruitment of interferon-producing Ly6C+ monocytes and additionally enhances tumour-specific CD8+ T cells. In comparison with other clinically evaluated oncolytic viruses and to PD-1 blockade, LCMV treatment shows promising antitumoural benefits. In conclusion, therapeutically administered arenavirus replicates in cancer cells and induces tumour regression by enhancing local immune responses.

Intratumoral Immunization by p19Arf and Interferon-β Gene Transfer in a Heterotopic Mouse Model of Lung Carcinoma

Therapeutic strategies that act by eliciting and enhancing antitumor immunity have been clinically validated as an effective treatment modality but may benefit from the induction of both cell death and immune activation as primary stimuli. Using our AdRGD-PG adenovector platform, we show here for the first time that in situ gene transfer of p19Arf and interferon-β (IFNβ) in the LLC1 mouse model of lung carcinoma acts as an immunotherapy. Although p19Arf is sufficient to induce cell death, only its pairing with IFNβ significantly induced markers of immunogenic cell death. In situ gene therapy with IFNβ, either alone or in combination with p19Arf, could retard tumor progression, but only the combined treatment was associated with a protective immune response. Specifically in the case of combined intratumoral gene transfer, we identified 167 differentially expressed genes when using microarray to evaluate tumors that were treated in vivo and confirmed the activation of CCL3, CXCL3, IL1α, IL1β, CD274, and OSM, involved in immune response and chemotaxis. Histologic evaluation revealed significant tumor infiltration by neutrophils, whereas functional depletion of granulocytes ablated the antitumor effect of our approach. The association of in situ gene therapy with cisplatin resulted in synergistic elimination of tumor progression. In all, in situ gene transfer with p19Arf and IFNβ acts as an immunotherapy involving recruitment of neutrophils, a desirable but previously untested outcome, and this approach may be allied with chemotherapy, thus providing significant antitumor activity and warranting further development for the treatment of lung carcinoma.

Nrf2 Knockdown Disrupts the Protective Effect of Curcumin on Alcohol-Induced Hepatocyte Necroptosis

It has emerged that hepatocyte necroptosis plays a critical role in chronic alcoholic liver disease (ALD). Our previous study has identified that the beneficial therapeutic effect of curcumin on alcohol-caused liver injury might be attributed to activation of nuclear factor (erythroid-derived 2)-like 2 (Nrf2), whereas the role of curcumin in regulating necroptosis and the underlying mechanism remain to be determined. We first found that chronic alcohol consumption triggered obvious hepatocyte necroptosis, leading to increased expression of receptor-interacting protein 1, receptor-interacting protein 3, high-mobility group box 1, and phosphorylated mixed lineage kinase domain-like in murine livers. Curcumin dose-dependently ameliorated hepatocyte necroptosis and alleviated alcohol-caused decrease in hepatic Nrf2 expression in alcoholic mice. Then Nrf2 shRNA lentivirus was introduced to generate Nrf2-knockdown mice. Our results indicated that Nrf2 knockdown aggravated the effects of alcohol on liver injury and necroptosis and even abrogated the inhibitory effect of curcumin on necroptosis. Further, activated Nrf2 by curcumin inhibited p53 expression in both livers and cultured hepatocytes under alcohol stimulation. The next in vitro experiments, similar to in vivo ones, revealed that although Nrf2 knockdown abolished the suppression of curcumin on necroptosis of hepatocytes exposed to ethanol, p53 siRNA could clearly rescued the relative effect of curcumin. In summary, for the first time, we concluded that curcumin attenuated alcohol-induced hepatocyte necroptosis in a Nrf2/p53-dependent mechanism. These findings make curcumin an excellent candidate for ALD treatment and advance the understanding of ALD mechanisms associated with hepatocyte necroptosis.

Oncolytic vaccine virus harbouring the IL-24 gene suppresses the growth of lung cancer by inducing apoptosis

Lung cancer has an especially high incidence rate worldwide, and its resistance to cell death and chemotherapeutic drugs increases its intractability. The vaccinia virus has been shown to destroy neoplasm within a short time and disseminate rapidly and extensively as an enveloped virion throughout the circulatory system, and this virus has also demonstrated a strong ability to overexpress exogenous genes. Interleukin-24 (IL-24/mda-7) is an important cytokine that belongs to the activating caspase family and facilitates the inhibition of STAT3 when a cell enters the apoptosis pathway. In this study, we constructed a cancer-targeted vaccinia virus carrying the IL-24 gene knocked in the region of the viral thymidine kinase (TK) gene (VV-IL-24). Our results showed that VV-IL-24 efficiently infected and destroyed lung cancer cells via caspase-dependent apoptosis and decreased the expression of STAT3. In vivo, VV-IL-24 expressed IL-24 at a high level in the transplanted tumour, reduced STAT3 activity, and eventually led to apoptosis. In conclusion, we demonstrated that vv-IL-24 has the potential for use as a new human lung cancer treatment.

Microglia and astrocytes attenuate the replication of the oncolytic vaccinia virus LIVP 1.1.1 in murine GL261 gliomas by acting as vaccinia virus traps

Background

Oncolytic virotherapy is a novel approach for the treatment of glioblastoma multiforme (GBM) which is still a fatal disease. Pathologic features of GBM are characterized by the infiltration with microglia/macrophages and a strong interaction between immune- and glioma cells. The aim of this study was to determine the role of microglia and astrocytes for oncolytic vaccinia virus (VACV) therapy of GBM.

Methods

VACV LIVP 1.1.1 replication in C57BL/6 and Foxn1^nu/nu mice with and without GL261 gliomas was analyzed. Furthermore, immunohistochemical analysis of microglia and astrocytes was investigated in non-, mock-, and LIVP 1.1.1-infected orthotopic GL261 gliomas in C57BL/6 mice. In cell culture studies virus replication and virus-mediated cell death of GL261 glioma cells was examined, as well as in BV-2 microglia and IMA2.1 astrocytes with M1 or M2 phenotypes. Co-culture experiments between BV-2 and GL261 cells and apoptosis/necrosis studies were performed. Organotypic slice cultures with implanted GL261 tumor spheres were used as additional cell culture system.

Results

We discovered that orthotopic GL261 gliomas upon intracranial virus delivery did not support replication of LIVP 1.1.1, similar to VACV-infected brains without gliomas. In addition, recruitment of Iba1⁺ microglia and GFAP⁺ astrocytes to orthotopically implanted GL261 glioma sites occurred already without virus injection. GL261 cells in culture showed high virus replication, while replication in BV-2 and IMA2.1 cells was barely detectable. The reduced viral replication in BV-2 cells might be due to rapid VACV-induced apoptotic cell death. In BV-2 and IMA 2.1 cells with M1 phenotype a further reduction of virus progeny and virus-mediated cell death was detected. Application of BV-2 microglial cells with M1 phenotype onto organotypic slice cultures with implanted GL261 gliomas resulted in reduced infection of BV-2 cells, whereas GL261 cells were well infected.

Conclusion

Our results indicate that microglia and astrocytes, dependent on their activation state, may preferentially clear viral particles by immediate uptake after delivery. By acting as VACV traps they further reduce efficient virus infection of the tumor cells. These findings demonstrate that glia cells need to be taken into account for successful GBM therapy development.

Apoptosis, autophagy, necroptosis, and cancer metastasis

Metastasis is a crucial hallmark of cancer progression, which involves numerous factors including the degradation of the extracellular matrix (ECM), the epithelial-to-mesenchymal transition (EMT), tumor angiogenesis, the development of an inflammatory tumor microenvironment, and defects in programmed cell death. Programmed cell death, such as apoptosis, autophagy, and necroptosis, plays crucial roles in metastatic processes. Malignant tumor cells must overcome these various forms of cell death to metastasize. This review summarizes the recent advances in the understanding of the mechanisms by which key regulators of apoptosis, autophagy, and necroptosis participate in cancer metastasis and discusses the crosstalk between apoptosis, autophagy, and necroptosis involved in the regulation of cancer metastasis.

Adipose tissue-derived mesenchymal stem cells cultured at high density express IFN-β and suppress the growth of MCF-7 human breast cancer cells

Although it has been reported that mesenchymal stem cells (MSCs) suppress tumor growth in vitro and in vivo, little is known about the underlying molecular mechanisms. We found that type I interferon is expressed in adipose tissue-derived stem cells (ASCs) cultured at high density, and ASCs and their conditioned medium (ASC-CM) suppress the growth of MCF-7 cells in vitro. Growth inhibition was amplified by glucose deprivation that resulted from high density culture of ASCs after 3days. The cytotoxic effect of the ASC-CM obtained from high density culture of ASCs was neutralized by anti-IFN-β antibody. STAT1 was phosphorylated in MCF-7 cells treated with ASC-CM, and JAK1/JAK2 inhibitor treatment decreased STAT1 phosphorylation. The cytotoxic effect of ASC-CM was reduced especially by JAK1 inhibitors in MCF-7 cells. Our findings suggest that ASCs cultured at high density express type I interferons, which suppresses tumor growth via STAT1 activation resulting from IFN-β secretion in MCF-7 breast cancer cells.

SMAC-armed vaccinia virus induces both apoptosis and necroptosis and synergizes the efficiency of vinblastine in HCC

Hepatocellular carcinoma (HCC) has particularly high incidence rate in Asia and its resistance to the chemotherapeutic drugs and cell death make it intractable. Vaccinia virus (VV) is a potential vehicle and has been widely used in cancer therapy. SMAC/DIABLO is a critical factor in activating caspases and eliminating inhibition of IAPs when the programmed cell death is promoted. In this study, we constructed a tumor-targeted vaccinia virus carrying SMAC/DIABLO gene that was knocked in the region of viral thymidine kinase gene (VV-SMAC). Our results showed that VV-SMAC efficiently infected and destroyed HCC cells via triggering both caspase-dependent apoptosis and necroptosis with depletion of IAPs. Furthermore, ripoptosome, a prerequisite complex of necroptosis, was assembled and induced by VV-SMAC. In addition, the combination of VV-SMAC and vinblastine represented a synergistic effect on HCC cells. In summary, our data suggest that VV-SMAC is a potential candidate and combination of VV-SMAC and vinblastine may provide a new avenue in treatment of HCC.

Multimodal immunogenic cancer cell death as a consequence of anticancer cytotoxic treatments

Apoptotic cell death generally characterized by a morphologically homogenous entity has been considered to be essentially non-immunogenic. However, apoptotic cancer cell death, also known as type 1 programmed cell death (PCD), was recently found to be immunogenic after treatment with several chemotherapeutic agents and oncolytic viruses through the emission of various danger-associated molecular patterns (DAMPs). Extensive studies have revealed that two different types of immunogenic cell death (ICD) inducers, recently classified by their distinct actions in endoplasmic reticulum (ER) stress, can reinitiate immune responses suppressed by the tumor microenvironment. Indeed, recent clinical studies have shown that several immunotherapeutic modalities including therapeutic cancer vaccines and oncolytic viruses, but not conventional chemotherapies, culminate in beneficial outcomes, probably because of their different mechanisms of ICD induction. Furthermore, interests in PCD of cancer cells have shifted from its classical form to novel forms involving autophagic cell death (ACD), programmed necrotic cell death (necroptosis), and pyroptosis, some of which entail immunogenicity after anticancer treatments. In this review, we provide a brief outline of the well-characterized DAMPs such as calreticulin (CRT) exposure, high-mobility group protein B1 (HMGB1), and adenosine triphosphate (ATP) release, which are induced by the morphologically distinct types of cell death. In the latter part, our review focuses on how emerging oncolytic viruses induce different forms of cell death and the combinations of oncolytic virotherapies with further immunomodulation by cyclophosphamide and other immunotherapeutic modalities foster dendritic cell (DC)-mediated induction of antitumor immunity. Accordingly, it is increasingly important to fully understand how and which ICD inducers cause multimodal ICD, which should aid the design of reasonably multifaceted anticancer modalities to maximize ICD-triggered antitumor immunity and eliminate residual or metastasized tumors while sparing autoimmune diseases.

Antitumor effect of recombinant human interferon-β adenovirus on esophageal squamous cell cancer in vitro

Interferon (IFN)-β has efficient antitumor effect both in vitro and in vivo, but its clinical implication is limited by short half-life and systemic toxicities. Gene therapy could be the choice to avoid the defects. Adenovirus vector containing human IFN-β gene was transfected into esophageal squamous cell carcinoma KYSE150 cells. Expression of human (h)IFN-β was detected by reverse transcription polymerase chain reaction and immunocytochemistry in KYSE150 cells. Cell growth and clonogenic assays, and flow cytometry were used to observe the antiproliferation effect and apoptosis on tumor cells, respectively. Reverse transcription polymerase chain reaction and immunocytochemistry showed obvious hIFN-β expression in KYSE150 cells after transfection and the tumor cell proliferation was obviously inhibited through cell proliferation and clonogenic assays. Flow cytometry analysis showed 27.3% cell apoptosis in adenovirus vector containing human IFN-β gene transfection group compared with 1.12% in empty vector control group. These findings indicate that hIFN-β gene mediated by recombinant adenovirus may have antitumor activity against human esophageal carcinoma cell by inducing apoptosis in vitro.