Parainfluenza Virus Infection Sensitizes Cancer Cells to DNA-Damaging Agents: Implications for Oncolytic Virus Therapy

Resistance to complement-mediated lysis of parainfluenza virus 5-infected cells is acquired after transition from acute to persistent infection

Persistent viral infections can be an important medical problem, with persistently infected (PI) cells extending viral shedding, maintaining inflammation, and providing potential sources for new viral variants. Given that PI cells can acquire resistance to some innate immune pathways, we tested the hypothesis that complement (C')-mediated lysis of parainfluenza virus 5 (PIV5)-infected cells would differ between acute-infected and PI cells. Biochemical and real-time cell viability assays showed effective C'-mediated lysis of A549 lung cells acutely infected with PIV5, through pathways that depended on C3 and C5, but largely independent of C6. A PIV5 PI cell line established by long-term culturing of acutely infected A549 cells showed a high-level persistent expression of PIV5 proteins and infectious virus. Under conditions that led to effective lysis of acute PIV5-infected cells, the PI cells were nearly completely resistant to C'-mediated killing. This lack of C' killing was not due to failure to activate C', since C'-treated PIV5 PI cells had extensive C3 and membrane attack complex deposition, as well as production of C3a and C5a. Transcriptomics analysis revealed the C' cascade as the most significantly upregulated pathway in PIV5 PI cells versus acute infection. Biochemical analyses showed that resistance to C' killing correlated with increased expression in PI cells of two major C' inhibitors: complement factor H and Vitronectin. The finding of acquisition of C' resistance after the transition from acute PIV5 infection to PI cells raises the potential to inform therapeutics for PIs based on modulating C' pathways.

IMPORTANCE

A persistent infection (PI) with RNA viruses can extend virus shedding, prolong inflammation, and be a source of new viral variants. Since profound changes to innate immune pathways can occur in PI cells, it was important to test PI cells for changes in sensitivity to the complement (C') system, powerful innate immune pathways capable of lysing infected cells. Using parainfluenza virus 5 (PIV5) as a model system, we show that PI cells are nearly completely resistant to C'-mediated lysis, in stark contrast to high sensitivity of acute PIV5-infected cells to C' killing. A key finding was the upregulated expression in PI cells of two C' inhibitors: Vitronectin and complement factor H. These are important results with strong potential to inform therapeutics, given that polymorphisms in C' genes can correlate with severity of viral infections, and clinical trials are underway with new drugs that modulate C' responses.

Molecular biology of canine parainfluenza virus V protein and its potential applications in tumor immunotherapy

Canine parainfluenza virus (CPIV) is a zoonotic virus that is widely distributed and is the main pathogen causing canine infectious respiratory disease (CIRD), also known as "kennel cough," in dogs. The CPIV-V protein is the only nonstructural protein of the virus and plays an important role in multiple stages of the virus life cycle by inhibiting apoptosis, altering the host cell cycle and interfering with the interferon response. In addition, studies have shown that the V protein has potential applications in the field of immunotherapy in oncolytic virus therapy or self-amplifying RNA vaccines. In this review, the biosynthesis, structural characteristics and functions of the CPIV-V protein are reviewed with an emphasis on how it facilitates viral immune escape and its potential applications in the field of immunotherapy. Therefore, this review provides a scientific basis for research into the CPIV-V protein and its potential applications.

DNA methyltransferase inhibitor 5-azacytidine enhances neuroblastoma cell lysis by an oncolytic parainfluenza virus

Studies with neuroblastoma have shown that the presence of aberrant DNA epigenetic modifications mediated by DNA methyltransferases correlates with poor prognosis, making these enzymes a target for therapeutics based on synthetic epigenetic modulators such as DNA methyltransferase inhibitors (DNMTi). Here, we have used a neuroblastoma cell line model to test the hypothesis that treatment with a DNMTi would enhance cell killing when used in combination with oncolytic Parainfluenza virus 5 (P/V virus), a cytoplasmic-replicating RNA virus. Pretreatment of SK-N-AS cells with the DNMTi 5-azacytidine substantially enhanced P/V virus-mediated cell death in a dose- and multiplicity of infection-dependent manner. Infection with the virus alone and the combination treatment with 5-azacytidine and P/V virus infection led to the activation of caspases-8, -9, and -3/7. Inhibition of caspases using a pan-caspase inhibitor minimally affected cell killing by P/V virus alone, but by contrast, largely reduced cell death mediated by 5-azacytidine treatment alone or in combination with P/V virus infection. 5-Azacytidine pretreatment dampened P/V virus gene expression and growth within the SK-N-AS cell population, which correlated with enhanced expression of important antiviral genes such as interferon-β and OAS2 . Taken together, our data support the role of combination treatment using 5-azacytidine and an oncolytic P/V virus for neuroblastoma therapy.

Comprehensive assessment on the applications of oncolytic viruses for cancer immunotherapy

The worldwide burden of cancers is increasing at a very high rate, including the aggressive and resistant forms of cancers. Certain levels of breakthrough have been achieved with the conventional treatment methods being used to treat different forms of cancers, but with some limitations. These limitations include hazardous side effects, destruction of non-tumor healthy cells that are rapidly dividing and developing, tumor resistance to anti-cancer drugs, damage to tissues and organs, and so on. However, oncolytic viruses have emerged as a worthwhile immunotherapeutic option for the treatment of different types of cancers. In this treatment approach, oncolytic viruses are being modeled to target cancer cells with optimum cytotoxicity and spare normal cells with optimal safety, without the oncolytic viruses themselves being killed by the host immune defense system. Oncolytic viral infection of the cancer cells are also being genetically manipulated (either by removal or addition of certain genes into the oncolytic virus genome) to make the tumor more visible and available for attack by the host immune cells. Hence, different variants of these viruses are being developed to optimize their antitumor effects. In this review, we examined how grave the burden of cancer is on a global level, particularly in sub-Saharan Africa, major conventional therapeutic approaches to the treatment of cancer and their individual drawbacks. We discussed the mechanisms of action employed by these oncolytic viruses and different viruses that have found their relevance in the fight against various forms of cancers. Some pre-clinical and clinical trials that involve oncolytic viruses in cancer management were reported. This review also examined the toxicity and safety concerns surrounding the adoption of oncolytic viro-immunotherapy for the treatment of cancers and the likely future directions for researchers and general audience who wants updated information.

CD24 Expression Dampens the Basal Antiviral State in Human Neuroblastoma Cells and Enhances Permissivity to Zika Virus Infection

Zika virus (ZIKV) exhibits distinct selectivity for infection of various cells and tissues, but how host cellular factors modulate varying permissivity remains largely unknown. Previous studies showed that the neuroblastoma cell line SK-N-AS (expressing low levels of cellular protein CD24) was highly restricted for ZIKV infection, and that this restriction was relieved by ectopic expression of CD24. We tested the hypothesis that CD24 expression allowed ZIKV replication by suppression of the antiviral response. SK-N-AS cells expressing an empty vector (termed CD24-low cells) showed elevated basal levels of phosphorylated STAT1, IRF-1, IKKE, and NFκB. In response to exogenously added type I interferon (IFN-I), CD24-low cells had higher-level induction of antiviral genes and activity against two IFN-I-sensitive viruses (VSV and PIV5-P/V) compared to SK-N-AS cells with ectopic CD24 expression (termed CD24-high cells). Media-transfer experiments showed that the inherent antiviral state of CD24-low cells was not dependent on a secreted factor such as IFN-I. Transcriptomics analysis revealed that CD24 expression decreased expression of genes involved in intracellular antiviral pathways, including IFN-I, NFκB, and Ras. Our findings that CD24 expression in neuroblastoma cells represses intracellular antiviral pathways support the proposal that CD24 may represent a novel biomarker in cancer cells for susceptibility to oncolytic viruses.

Advances in nanoparticle mediated targeting of RNA binding protein for cancer

RNA binding proteins (RBPs) enact a very crucial part in the RNA directive processes. Atypical expression of these RBPs affects many steps of RNA metabolism, majorly altering its expression. Altered expression and dysfunction of RNA binding proteins lead to cancer progression and other diseases. We enumerate various available interventions, and recent findings focused on targeting RBPs for cancer therapy and diagnosis. The treatment, sensitization, chemoprevention, gene-mediated, and virus mediated interventions were studied to treat and diagnose cancer. The application of passively and actively targeted lipidic nanoparticles, polymeric nanoparticles, virus-based particles, and vaccine-based immunotherapy for the delivery of therapeutic agent/s against cancer are discussed. We also discuss the formulation aspect of nanoparticles for achieving delivery at the site of action and ongoing clinical trials targeting RBPs.

Differential In Vitro Growth and Cell Killing of Cancer versus Benign Prostate Cells by Oncolytic Parainfluenza Virus

The development of effective oncolytic viruses will require understanding the differences in virus replication and killing between normal and cancer cells. Here, we have evaluated infections of metastatic cancer (22Rv1) and benign non-tumorigenic (BPH-1) prostate cell lines with a mutant parainfluenza virus 5 (P/V/F) encoding a defective V protein and a hyperfusogenic F protein. Under low multiplicity of infection (MOI), the P/V/F mutant efficiently spread in 22Rv1 cells but was restricted in BPH-1 cells due to type-I interferon (IFN-I) responses. In mixed co-cultures, the P/V/F mutant showed specificity towards and spread within the 22Rv1 cells versus BPH-1 cells. Under high MOI conditions, both BPH-1 and 22Rv1 cells showed efficient infection by the P/V/F mutant. However, compared to BPH-1 cells, the 22Rv1 cancer cells showed increased cytopathic effect, higher induction of caspase-8 and -9, and extensive syncytia formation. In 22Rv1 spheroid cultures, P/V/F infection was less efficient compared to monolayers, but the virus was able to spread through spheroids and induce death. These data indicate that IFN-I sensitivity is a major determinant of specificity of P/V/F spread through populations of cancer versus benign cells, and additionally, differences in activation of apoptotic pathways and syncytia formation can contribute to differential outcomes in cancer versus benign cells.

Small molecules baicalein and cinnamaldehyde are potentiators of measles virus-induced breast cancer oncolysis

BACKGROUND

Although the breast cancer mortality has slowed down from 2008 to 2017, breast cancer incidence rate continues to rise and thus, new and/or improved treatments are highly needed. Among them, oncolytic virotherapy which has the ability of facilitating the antitumor adaptive immunity, appears as a promising anticancer therapy. Oncolytic measles virus (MV) is particularly suitable for targeting breast cancer due to the upregulation of MV's receptor nectin-4. Nonetheless, with limited clinical success currently, ways of boosting MV-induced breast cancer oncolysis are therefore necessary. Oncolytic virotherapy alone and combined with chemotherapeutic drugs are two strategic areas with intensive development for the search of anticancer drugs. Considering that baicalein (BAI) and cinnamaldehyde (CIN) have demonstrated antitumor properties against multiple cancers including breast cancer, they could be good partners for MV-based oncolytic virotherapy.

PURPOSE

To assess the in vitro effect of BAI and CIN with MV and assess their combination effects.

METHODS

We examined the combinatorial cytotoxic effect of oncolytic MV and BAI or CIN on MCF-7 breast cancer cells. Potential anti-MV activities of the phytochemicals were first investigated in vitro to determine the optimal combination model. Synergism of MV and BAI or CIN was then evaluated in vitro by calculating the combination indices. Finally, cell cycle analysis and apoptosis assays were performed to confirm the mechanism of synergism.

RESULTS

Overall, the viral sensitization combination modality using oncolytic MV to first infect MCF-7 breast cancer cells followed by drug treatment with BAI or CIN was found to produce significantly enhanced tumor killing. Further mechanistic studies showed that the combinations 'MV-BAI' and 'MV-CIN' display synergistic anti-breast cancer effect, mediated by elevated apoptosis.

CONCLUSION

We demonstrated, for the first time, effective combination of oncolytic MV with BAI or CIN that could be further explored and potentially developed into novel therapeutic strategies targeting nectin-4-marked breast cancer cells.

Persistent Newcastle disease virus infection in bladder cancer cells is associated with putative pro-survival and anti-viral transcriptomic changes

Background

Newcastle disease virus (NDV) is an oncolytic virus with excellent selectivity against cancer cells, both in vitro and in vivo. Unfortunately, prolonged in vitro NDV infection results in the development of persistent infection in the cancer cells which are then able to resist NDV-mediated oncolysis. However, the mechanism of persistency of infection remains poorly understood.

Methods

In this study, we established persistently NDV-infected EJ28 bladder cancer cells, designated as EJ28P. Global transcriptomic analysis was subsequently carried out by microarray analysis. Differentially expressed genes (DEGs) between EJ28 and EJ28P cells identified by the edgeR program were further analysed by Gene Set Enrichment Analysis (GSEA) and Ingenuity Pathway Analysis (IPA) analyses. In addition, the microarray data were validated by RT-qPCR.

Results

Persistently NDV-infected EJ28 bladder cancer cells were successfully established and confirmed by flow cytometry. Microarray analysis identified a total of 368 genes as differentially expressed in EJ28P cells when compared to the non-infected EJ28 cells. GSEA revealed that the Wnt/β-catenin and KRAS signalling pathways were upregulated while the TGF-β signalling pathway was downregulated. Findings from this study suggest that the upregulation of genes that are associated with cell growth, pro-survival, and anti-apoptosis may explain the survivability of EJ28P cells and the development of persistent infection of NDV.

Conclusions

This study provides insights into the transcriptomic changes that occur and the specific signalling pathways that are potentially involved in the development and maintenance of NDV persistency of infection in bladder cancer cells. These findings warrant further investigation and is crucial towards the development of effective NDV oncolytic therapy against cancer.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-08345-y.

Cytotoxicity, cellular uptake and apoptotic responses in human coronary artery endothelial cells exposed to ultrasmall superparamagnetic iron oxide nanoparticles

Ultrasmall superparamagnetic iron oxide nanoparticles (USPION) possess reactive surfaces, are metabolized and exhibit unique magnetic properties. These properties are desirable for designing novel theranostic biomedical products; however, toxicity mechanisms of USPION are not completely elucidated. The goal of this study was to investigate cell interactions (uptake and cytotoxicity) of USPION using human coronary artery endothelial cells as a vascular cell model. Polyvinylpirrolidone-coated USPION were characterized: average diameter 17 nm (transmission electron microscopy [TEM]), average hydrodynamic diameter 44 nm (dynamic light scattering) and zeta potential -38.75 mV. Cells were exposed to 0 (control), 25, 50, 100 or 200 μg/mL USPION. Concentration- and time-dependent cytotoxicity were observed after 3-6 hours through 24 hours of exposure using Alamar Blue and Real-Time Cell Electronic Sensing assays. Cell uptake was evaluated by imaging using live-dead confocal microscopy, actin and nuclear fluorescent staining, and TEM. Phase-contrast, confocal microscopy, and TEM imaging showed significant USPION internalization as early as 3 hours after exposure to 25 μg/mL. TEM imaging demonstrated particle internalization in secondary lysosomes with perinuclear localization. Three orthogonal assays were conducted to assess apoptosis. TUNEL staining demonstrated a marked increase in fragmented DNA, a response pathognomonic of apoptosis, after a 4-hour exposure. Cells subjected to agarose gel electrophoresis exhibited degraded DNA 3 hours after exposure. Caspase-3/7 activity increased after a 3-hour exposure. USPION uptake resulted in cytotoxicity involving apoptosis and these results contribute to further mechanistic understanding of the USPION toxicity in vitro in cardiovascular endothelial cells.

Recent advances in oncolytic virus-based cancer therapy

Administration of oncolytic viruses (OVs) is an emerging anticancer strategy that exploits the lytic nature of viral replication to enhance the killing of malignant cells. OVs can be used as tools to directly induce cancer cell death and to trigger local and/or systemic immune responses to metastatic cancer in vivo. The effectiveness of OV therapy was initially highlighted by the clinical use of the genetically modified herpes virus, talimogene laherparepvec, for melanoma therapy. A number of OVs are now being evaluated as potential treatments for cancer in clinical trials. In spite of being engineered to specifically target tumor cells, the safety and off-target effects of OV therapy are a concern. The potential safety concerns of OVs are highlighted by current clinical trial criteria, which exclude individuals harbouring other viral infections and people who are immunocompromised. Despite the potential for adverse effects, clinical trials to date revealed relatively minimal adverse immune-related effects, such as fever. With advances in our understanding of virus replication cycles, several novel OVs have emerged. Reverse genetic systems have facilitated the insertion of anticancer genes into a range of OVs to further enhance their tumor-killing capacity. In this review, we highlight the recent advances in OV therapy for a range of human cancers in in vitro and in in vivo animal studies. We further discuss the future of OVs as a therapeutic strategy for a range of life-threatening cancers.

Inhibition of DNA Repair Mechanisms and Induction of Apoptosis in Triple Negative Breast Cancer Cells Expressing the Human Herpesvirus 6 U94

Triple-negative breast cancer (TNBC) accounts for 15–20% of all breast cancers. In spite of initial good response to chemotherapy, the prognosis of TNBC remains poor and no effective specific targeted therapy is readily available. Recently, we demonstrated the ability of U94, the latency gene of human herpes virus 6 (HHV-6), to interfere with proliferation and with crucial steps of the metastatic cascade by using MDA-MB 231 TNBC breast cancer cell line. U94 expression was also associated with a partial mesenchymal-to-epithelial transition (MET) of cells, which displayed a less aggressive phenotype. In this study, we show the ability of U94 to exert its anticancer activity on three different TNBC cell lines by inhibiting DNA damage repair genes, cell cycle and eventually leading to cell death following activation of the intrinsic apoptotic pathway. Interestingly, we found that U94 acted synergistically with DNA-damaging drugs. Overall, we provide evidence that U94 is able to combat tumor cells with different mechanisms, thus attesting for the great potential of this molecule as a multi-target drug in cancer therapy.

Histone Deacetylase Inhibitors Enhance Cell Killing and Block Interferon-Beta Synthesis Elicited by Infection with an Oncolytic Parainfluenza Virus

Previous results have shown that infection with the cytoplasmic-replicating parainfluenza virus 5 mutant P/V-CPI- sensitizes cells to DNA damaging agents, resulting in the enhanced killing of airway cancer cells. Here, we have tested the hypothesis that histone deacetylase (HDAC) inhibitors can also act with P/V-CPI- infection to enhance cancer cell killing. Using human small cell lung cancer and laryngeal cancer cell lines, 10 HDAC inhibitors were tested for their effect on viability of P/V-CPI- infected cells. HDAC inhibitors such as scriptaid enhanced caspase-3/7, -8 and -9 activity induced by P/V-CPI- and overall cell toxicity. Scriptaid-mediated enhanced killing was eliminated in lung cancer cells that were engineered to express a protein which sequesters double stranded RNA. Scriptaid also enhanced cancer cell killing by two other negative strand RNA viruses - the La Crosse virus and vesicular stomatitis virus. Scriptaid treatment enhanced the spread of the P/V-CPI- virus through a population of cancer cells, and suppressed interferon-beta induction through blocking phosphorylation and nuclear translocation of Interferon Regulatory Factor 3 (IRF-3). Taken together, these data support a role for combinations of a cytoplasmic-replicating RNA virus such as the P/V-CPI- mutant along with chemotherapeutic agents.