Oncolytic activity of Sindbis virus in human oral squamous carcinoma cells

RNAi Screening in Tumor Cells Identifies Artificial microRNAs That Improve Oncolytic Virus Replication

Background/Objectives: Oncolytic viruses infect and kill tumor cells while leaving normal cells unharmed. They are often attenuated through the reduction in their ability to antagonize antiviral defenses, leading to robust replication in tumor cells, which often possess defects in antiviral pathways, while minimizing replication in normal cells. However, not all tumors have defects in their antiviral defenses, and virus replication in these tumors is minimal, thus limiting therapeutic benefits. Therefore, identifying and modulating host factors that regulate virus replication in oncolytic virus-resistant cancer cells, but not normal cells, could lead to increased replication in these tumors and potentially improved therapeutic outcomes. Methods: To identify host factors that modulate oncolytic virus replication in tumor cells, we conducted an RNA interference screen by using a replication-competent library of Sindbis virus recombinants individually enabled with the capacity to elicit RNA interference in host genes via the expression of artificial microRNAs. Since the expression of artificial microRNAs is coupled to virus replication, this results in the selective enrichment of viral clones which express an artificial microRNA that promotes virus replication. Results: By using this approach, the serial passage of the Sindbis virus-artificial microRNA library in a tumor cell line followed by the deep sequencing of the selected viral populations led to the identification of several artificial microRNA sequences that were enriched. Furthermore, the identified artificial miRNA sequences increased the replication of several oncolytic viruses both in vitro and in vivo, ultimately leading to an enhanced therapeutic effect. Conclusions: Altogether, our study highlights the utility of this screening platform in identifying artificial microRNAs that enhance oncolytic virus efficacy.

Nanoparticle-mediated active and passive drug targeting in oral squamous cell carcinoma: current trends and advances

Oral squamous cell carcinoma (OSCC) is an invasive and highly malignant cancer with significant morbidity and mortality. Existing treatments including surgery, chemotherapy and radiation have poor overall survival rates and prognosis. The intended therapeutic effects of chemotherapy are limited by drug resistance, systemic toxicity and adverse effects. This review explores advances in OSCC treatment, with a focus on lipid-based platforms (solid lipid nanoparticles, nanostructured lipid carriers, lipid-polymer hybrids, cubosomes), polymeric nanoparticles, self-assembling nucleoside nanoparticles, dendrimers, magnetic nanovectors, graphene oxide nanostructures, stimuli-responsive nanoparticles, gene therapy, folic acid receptor targeting, gastrin-releasing peptide receptor targeting, fibroblast activation protein targeting, urokinase-type plasminogen activator receptor targeting, biotin receptor targeting and transferrin receptor targeting. This review also highlights oncolytic viruses as OSCC therapy candidates.

Approaches for Head and Neck Cancer Research - Current Status and the Way Forward

Head and neck cancers (HNCs) are seeing an increasing trend in their prevalence among both genders and are the seventh most common cancer type occurring at the global level. Studies addressing both the cancer cell physiology and individual differences in response to a specific treatment modality should be understood for arriving at effective treatment and management of the HNCs. In this article, we discuss the trends in HNC research and their various approaches starting from 2D in vitro models, which are the traditional experimental materials to recently established Cancer-Tissue Originated Spheroids (CTOS) distinctly contributing towards personalized or precision medicine.

Viral Proteins as Emerging Cancer Therapeutics

Simple Summary

This review is focused on enlisting viral proteins from different host sources, irrespective of their origin, that may act as future cancer curatives. Unlike the viral proteins that are responsible for tumor progression, these newly emerged viral proteins function as tumor suppressors. Their ability to regulate various cell signaling mechanisms specifically in cancer cells makes them interesting candidates to explore their use in cancer therapy. The discussion about such viral components may provide new insights into cancer treatment in the absence of any adverse effects to normal cells. The study also highlights avian viral proteins as a substitute to human oncolytic viruses for their ability to evade pre-existing immunity.

Abstract

Viruses are obligatory intracellular parasites that originated millions of years ago. Viral elements cover almost half of the human genome sequence and have evolved as genetic blueprints in humans. They have existed as endosymbionts as they are largely dependent on host cell metabolism. Viral proteins are known to regulate different mechanisms in the host cells by hijacking cellular metabolism to benefit viral replication. Amicable viral proteins, on the other hand, from several viruses can participate in mediating growth retardation of cancer cells based on genetic abnormalities while sparing normal cells. These proteins exert discreet yet converging pathways to regulate events like cell cycle and apoptosis in human cancer cells. This property of viral proteins could be harnessed for their use in cancer therapy. In this review, we discuss viral proteins from different sources as potential anticancer therapeutics.

Value of functional in-vivo endpoints in preclinical radiation research

BACKGROUND

Cancer research faces the problem of high rates of clinical failure of new treatment approaches after positive preclinical data. We hypothesize that a major confounding factor to this problem in radiooncology is the choice of the preclinical endpoint.

METHODS

We present a comprehensive re-evaluation of large-scale preclinical in-vivo data on fractionated irradiation alone or simultaneously with Epidermal Growth Factor Receptor inhibition. Taking the permanent local tumour control assay as a gold standard, we evaluated different tumour volume dependent endpoints that are widely used for preclinical experiments.

RESULTS

The analysis showed the highest correlations between volume related and local tumour control endpoints after irradiation alone. For combined treatments, wide inter-tumoural variations were observed with reduced correlation between the endpoints. Evaluation of growth delay per Gray (GD/Gy) based on two or more dose levels showed closest correlation with local tumour control dose 50% (TCD₅₀).

CONCLUSIONS

GD/Gy with at least two dose groups correlates with TCD₅₀, but cannot replace the latter as the goldstandard.

Oncolytic activity of naturally attenuated herpes-simplex virus HF10 against an immunocompetent model of oral carcinoma

Prognosis for advanced oral carcinoma remains poor. Oncolytic virotherapy uses replication-competent viruses to infect and kill only the tumor cells. However, it has been difficult to investigate the oncolytic activity of viruses against oral carcinomas in mouse models. This study established a mouse model of oral cancer and investigated the in vitro and in vivo anti-tumor effects of HF10, a highly attenuated, replication-competent herpes simplex virus (HSV)-1. Mouse tongue cancer was induced by injecting 4-nitroquinoline 1-oxide into the mouse tongue. The murine oral cancer cell line isolated from this tumor, named NMOC1, formed invasive carcinoma within a week when injected into mouse tongue. HF10 successfully infected, replicated, and spread in the cancer cells in vitro. HF10 was able to kill cancer cells isolated from human or mouse tongue tumor. HF10 injection into tongue carcinomas prolonged mouse survival without any side effects or weight loss. Intertumoral injection of GFP-expressing HF10 confirmed that viral spread was confined within the tumors. Immunohistochemical staining showed that HF10 induced infiltration of CD8-positive T cells around HSV-infected cells in the tumor mass, implying increased anti-tumor immunity. We successfully established an oral cancer cell line and showed that HF10 is a promising therapeutic agent for oral cancer.

Sindbis viral structural protein cytotoxicity on human neuroblastoma cells

PURPOSE

Oncolytic viral therapy for neuroblastoma (NB) cells with Sindbis virus (SINV) is a promising strategy for treating high-risk NB. Here, we evaluated the possibility of using SINV structural proteins as therapeutic agents for NB since UV-inactivated SINV could induce cytopathogenic effects.

METHODS

The cytotoxicity of UV-inactivated SINV toward human NB cell lines NB69, NGP, GOTO, NLF, SK-N-SH, SH-SY5Y, CHP134, NB-1, IMR32, and RT-BM-1 were analyzed. Apoptosis was confirmed by TUNEL assays. To determine the components of SINV responsible for the cytotoxicity of UV-inactivated SINV, expression vectors encoding the structural proteins, namely capsid, E2, and E1, were transfected in NB cells. Cytotoxicity was evaluated by MTT assays.

RESULTS

UV-inactivated SINV elicited more significant cytotoxicity in NB69, NGP, and RT-BM-1 than in normal human fibroblasts. Results of the transfection experiments showed that all NB cell lines susceptible to UV-inactivated SINV were highly susceptible to the E1 protein, whereas fibroblasts transfected with vectors harboring capsid, E1, or E2 were not.

CONCLUSIONS

We demonstrated that the cytotoxicity of the UV-inactivated SINV is due to apoptosis induced by the E1 structural protein of SINV, which can be used selectively as a therapeutic agent for NB.

Deficiency of the IRE1α-Autophagy Axis Enhances the Antitumor Effects of the Oncolytic Virus M1

Oncolytic virotherapy is an emerging treatment modality that uses replication-competent viruses to destroy cancer cells. M1 is a naturally occurring alphavirus (Togaviridae) which shows potent oncolytic activities against many cancers. Accumulation of unfolded proteins during virus replication leads to a transcriptional/translational response known as the unfolded protein response (UPR), which might counteract the antitumor effect of the oncolytic virus. In this report, we show that either pharmacological or biological inhibition of IRE1α or PERK, but not ATF6, substantially increases the oncolytic effects of the M1 virus. Moreover, inhibition of IRE1α blocks M1 virus-induced autophagy, which restricts the antitumor effects of the M1 virus through degradation of viral protein, in glioma cells. In addition, IRE1α suppression significantly increases the oncolytic effect of M1 virus in an orthotopic glioma model. From a molecular pathology study, we found that IRE1α is expressed at lower levels in higher-grade gliomas, suggesting greater antitumor efficacy of the oncolytic virus M1. Taken together, these findings illustrate a defensive mechanism of glioma cells against the oncolytic virus M1 and identify possible approaches to enhance the oncolytic viral protein accumulation and the subsequent lysis of tumor cells.IMPORTANCE Although oncolytic virotherapy is showing great promise in clinical applications, not all patients are benefiting. Identifying inhibitory signals in refractory cancer cells for each oncolytic virus would provide a good chance to increase the therapeutic effect. Here we describe that infection with the oncolytic virus M1 triggers the unfolded protein response (UPR) and subsequent autophagy, while blocking the UPR-autophagy axis significantly potentiates the antitumor efficacy of M1 in vitro and in vivo A survey of cancer tissue banks revealed that IRE1α, a key element in the UPR pathway, is commonly downregulated in higher-grade human gliomas, suggesting favorable prospects for the application of M1. Our work provides a potential predictor and target for enhancement of the therapeutic effectiveness of the M1 virus. We predict that the mechanism-based combination therapy will promote cancer virotherapy in the future.

Monitoring the Efficacy of Oncolytic Viruses via Gene Expression

With the recent success of oncolytic viruses in clinical trials, efforts toward improved monitoring of the viruses and their mechanism have intensified. Four main gene expression strategies have been employed to date including: analyzing overall gene expression in tumor cells, looking at gene expression of a few specific genes in the tumor cells, focusing on gene expression of specific transgenes introduced into the virus, and following gene expression of certain viral genes. Each strategy presents certain advantages and disadvantages over the others. Various methods to organize the dysregulated genes into clusters have provided a window into the mechanism of action for these viruses. Methodologically, the combined approach of looking at both overall gene expression, the tumor cells and gene expression of viral genes, enables researchers to assess correlation between the introduction of the virus and the changes in the tumor. This would seem to be the most productive approach for future studies, providing much information on mechanism and timing.

Oncolytic Alphaviruses in Cancer Immunotherapy

Oncolytic viruses show specific targeting and killing of tumor cells and therefore provide attractive assets for cancer immunotherapy. In parallel to oncolytic viral vectors based on adenoviruses and herpes simplex viruses, oncolytic RNA viruses and particularly alphaviruses have been evaluated as delivery vehicles. Immunization studies in experimental rodent models for various cancers including glioblastoma, hematologic, hepatocellular, colon, cervix, and lung cancer as well as melanoma have been conducted with naturally occurring oncolytic alphavirus strains such as M1 and Sindbis AR339. Moreover, animals were vaccinated with engineered oncolytic replication-deficient and -competent Semliki Forest virus, Sindbis virus and Venezuelan equine encephalitis virus vectors expressing various antigens. Vaccinations elicited strong antibody responses and resulted in tumor growth inhibition, tumor regression and even complete tumor eradication. Vaccination also led to prolonged survival in several animal models. Furthermore, preclinical evaluation demonstrated both prophylactic and therapeutic efficacy of oncolytic alphavirus administration. Clinical trials in humans have mainly been limited to safety studies so far.

Oncolytic viral therapy for neuroblastoma cells with Sindbis virus AR339 strain

PURPOSE

With current treatment regimens, high-risk neuroblastoma (NB) remains largely incurable. Oncolytic viral therapy uses replication-competent viruses, like Sindbis virus (SINV), to kill cancers. The SINV AR339 strain is blood borne and relatively non-virulent. We evaluated the feasibility of SINV AR339 for treating human NB.

METHODS

The cytotoxicity and viral growth of SINV AR339 were evaluated for five human NB cell lines, SK-N-SH, IMR-32, LAN-5, GOTO, and RT-BM-1. SINV-induced apoptosis was confirmed by TUNEL assays and PARP-1 cleavage. In vivo effects of SINV on neuroblastoma cell xenografts in nude mice were assessed by intratumoral or intravenous SINV inoculation.

RESULTS

In five human NB cell lines, SINV infections induced remarkable cytotoxicity. The mRNA expressions of anti-apoptotic genes, Bcl-2 and Bcl-xL, in LAN-5 and RT-BM-1, which were less sensitive to SINV infection, increased in response to SINV infection, while the other NB cell lines sensitive to SINV infection failed to respond. In nude mice, intratumoral and intravenous SINV inoculations caused significant regression of NB xenograft tumors.

CONCLUSION

Our results suggested that SINV AR339 was significantly oncolytic against human NB. Thus, SINV showed promise as a novel therapy for treating NB.

Bugs and drugs: oncolytic virotherapy in combination with chemotherapy

Single agent therapies are rarely successful in treating cancer, particularly at metastatic or end stages, and survival rates with monotherapies alone are generally poor. The combination of multiple therapies to treat cancer has already driven significant improvements in the standard of care treatments for many types of cancers. The first combination treatments exploited for cancer therapy involved the use of several cytotoxic chemotherapy agents. Later, with the development of more targeted agents, the use of novel, less toxic drugs, in combination with the more classic cytotoxic drugs has proven advantageous for certain cancer types. Recently, the combination of oncolytic virotherapy with chemotherapy has shown that the use of these two therapies with very distinct anti-tumor mechanisms may also lead to synergistic interactions that ultimately result in increased therapeutic effects not achievable by either therapy alone. The mechanisms of synergy between oncolytic viruses (OVs) and chemotherapeutic agents are just starting to be elucidated. It is evident, however, that the success of these OV-drug combinations depends greatly on the particular OV, the drug(s) selected, and the cancer type targeted. This review summarizes the different OV-drug combinations investigated to date, including the use of second generation armed OVs, which have been studied with the specific purpose of generating synergistic interactions with particular chemotherapy agents. The known mechanisms of synergy between these OV-drug combinations are also summarized. The importance of further investigating these mechanisms of synergy will be critical in order to maximize the therapeutic efficacy of OV-drug combination therapies in the future.

N-acetylcysteine (NAC) inhibits cell growth by mediating the EGFR/Akt/HMG box-containing protein 1 (HBP1) signaling pathway in invasive oral cancer

OBJECTIVES

Overexpression of the epidermal growth factor (EGF) receptor (EGFR) gene in the squamous cell carcinomas of the head and neck (SCCHN) is often associated with inauspicious prognosis and poor survival. N-acetylcysteine (NAC), a compound from some vegetables and allium species, appears anti-tumorigenesis, but the underlying mechanism is unclear. The objective of this study is to investigate the role of NAC in EGFR-overexpressing oral cancer.

MATERIALS AND METHODS

Both HSC-3 and SCC-4 human tongue squamous carcinoma cell lines and an HSC-3 xenograft mouse model were used to test the anti-growth efficacy of NAC in vitro and in vivo, respectively.

RESULTS

NAC treatment suppressed cell growth, with concomitantly increased expression of HMG box-containing protein 1 (HBP1), a transcription suppressor, and decreased EGFR/Akt activation, in EGFR-overexpressing HSC-3 oral cancer cells. HBP1 knockdown attenuated the growth arrest and apoptosis induced by NAC. Lastly, NAC and AG1478, an EGFR inhibitor, additively suppressed colony formation in HSC-3 cells.

CONCLUSION

Taken together, our data indicate that NAC exerts its growth-inhibitory function through modulating EGFR/Akt signaling and HBP1 expression in EGFR-overexpressing oral cancer.

Alphavirus vectors for cancer therapy

Alphaviruses contain a single strand RNA genome that can be easily modified to express heterologous genes at very high levels in a broad variety of cells, including tumor cells. Alphavirus vectors can be used as viral particles containing a packaged vector RNA, or directly as nucleic acids in the form of RNA or DNA. In the latter case alphavirus RNA is cloned within a DNA vector downstream of a eukaryotic promoter. Expression mediated by these vectors is generally transient due to the induction of apoptosis. The high expression levels, induction of apoptosis, and activation of type I IFN response are the key features that have made alphavirus vectors very attractive for cancer treatment and vaccination. Alphavirus vectors have been successfully used as vaccines to induce protective and therapeutic immune responses against many tumor-associated antigens in animal models of mastocytoma, melanoma, mammary, prostate, and virally induced tumors. Alphavirus vectors have also shown a high antitumoral efficacy by expressing antitumoral molecules in tumor cells, which include cytokines, antiangiogenic factors or toxic proteins. In these studies induction of apoptosis in tumor cells contributed to the antitumoral efficacy by the release of tumor antigens that can be uptaken by antigen presenting cells, enhancing immune responses against tumors. The potential use of alphaviruses as oncolytic agents has also been evaluated for avirulent strains of Semliki Forest virus and Sindbis virus. The fact that this latter virus has a natural tropism for tumor cells has led to many studies in which this vector was able to reach metastatic tumors when administered systemically. Other "artificial" strategies to increase the tropism of alphavirus for tumors have also been evaluated and will be discussed.

Oncolytic Viruses for Cancer Therapy: Overcoming the Obstacles

Targeted therapy of cancer using oncolytic viruses has generated much interest over the past few years in the light of the limited efficacy and side effects of standard cancer therapeutics for advanced disease. In 2006, the world witnessed the first government-approved oncolytic virus for the treatment of head and neck cancer. It has been known for many years that viruses have the ability to replicate in and lyse cancer cells. Although encouraging results have been demonstrated in vitro and in animal models, most oncolytic viruses have failed to impress in the clinical setting. The explanation is multifactorial, determined by the complex interactions between the tumor and its microenvironment, the virus, and the host immune response. This review focuses on discussion of the obstacles that oncolytic virotherapy faces and recent advances made to overcome them, with particular reference to adenoviruses.