Preclinical and clinical trials of oncolytic vaccinia virus in cancer immunotherapy:a comprehensive review

Oncolytic virotherapy has emerged as a promising treatment for human cancers owing to an ability to elicit curative effects via systemic administration.Tumor cells often create an unfavorable immunosuppressive microenvironment that degrade viral structures and impede viral replication;however,recent studies have established that viruses altered via genetic modifications can serve as effective oncolytic agents to combat hostile tumor environments.Specifically,oncolytic vaccinia virus(OVV)has gained popularity owing to its safety,potential for systemic delivery,and large gene insertion capacity.This review highlights current research on the use of engineered mutated viruses and gene-armed OVVs to reverse the tumor microenvironment and enhance antitumor activity in vitro and in vivo,and provides an overview of ongoing clinical trials and combination therapies.In addition,we discuss the potential benefits and drawbacks of OVV as a cancer therapy,and explore different perspectives in this field.

Oncolytic virus-based hepatocellular carcinoma treatment:Current status,intravenous delivery strategies,and emerging combination therapeutic solutions

Current treatments for advanced hepatocellular carcinoma(HCC)have limited success in improving patients’quality of life and prolonging life expectancy.The clinical need for more efficient and safe therapies has contributed to the exploration of emerging strategies.Recently,there has been increased interest in oncolytic viruses(OVs)as a therapeutic modality for HCC.OVs undergo selective replication in cancerous tissues and kill tumor cells.Strikingly,pexastimogene devacirepvec(Pexa-Vec)was granted an orphan drug status in HCC by the U.S.Food and Drug Administration(FDA)in 2013.Meanwhile,dozens of OVs are being tested in HCC-directed clinical and preclinical trials.In this review,the pathogenesis and current therapies of HCC are outlined.Next,we summarize multiple OVs as single therapeutic agents for the treatment of HCC,which have demonstrated certain efficacy and lowtoxicity.Emerging carrier cell-,bioengineered cell mimetic-or nonbiological vehicle-mediated OV intravenous delivery systems in HCC therapy are described.In addition,we highlight the combination treatments between oncolytic virotherapy and other modalities.Finally,the clinical challenges and prospects of OV-based biotherapy are discussed,with the aim of continuing to develop a fascinating approach in HCC patients.

Progress in oncolytic viruses modified with nanomaterials for intravenous application

In oncolytic virus(OV)therapy,a critical component of tumor immunotherapy,viruses selectively infect,replicate within,and eventually destroy tumor cells.Simultaneously,this therapy activates immune responses and mobilizes immune cells,thereby eliminating residual or distant cancer cells.However,because of OVs’high immunogenicity and immune clearance during circulation,their clinical applications are currently limited to intratumoral injections,and their use is severely restricted.In recent years,numerous studies have used nanomaterials to modify OVs to decrease virulence and increase safety for intravenous injection.The most commonly used nanomaterials for modifying OVs are liposomes,polymers,and albumin,because of their biosafety,practicability,and effectiveness.The aim of this review is to summarize progress in the use of these nanomaterials in preclinical experiments to modify OVs and to discuss the challenges encountered from basic research to clinical application.

Oncolytic adenovirus-mediated MDA-7/IL-24 overexpression enhances antitumor activity in hepatocellular carcinoma cell lines

BACKGROUND: Melanoma differentiation-associated gene-7 (MDA-7)/interleukin-24 (IL-24) is a novel tumor suppressor gene, which has suppressor activity in a broad spectrum of human cancer cells. We investigated the effect of the replication-competent oncolytic adenovirus SG600-IL24 and replication-incompetent adenovirus Ad.IL-24, both expressing human MDA-7/IL-24 on the hepatocellular carcinoma cell lines HepG2, Hep3B, SMMC-7721, HCCLM3, and the normal liver cell line L02. METHODS: Hepatocellular carcinoma cell lines and the normal liver cell line were infected with SG600-IL24 and Ad.IL-24. The mRNA and protein expression of MDA-7/IL-24 in infected cells was confirmed by RT-PCR, ELISA, and Western blotting. MTT assay was used to investigate the proliferation effect. Hoechst staining and Annexin-V and PI staining were performed to study the MDA-7/IL-24 gene expressed in HCC cell lines and the normal liver cell line. Flow cytometry was used to analyse the cell cycle. RESULTS: RT-PCR, ELISA and Western blotting confirmed that the exogenous MDA-7/IL-24 gene was highly expressed in cells infected with SG600-IL24. MTT and apoptosis detection indicated that SG600-IL24 induced growth suppression, promoted apoptosis, and blocked cancer cell lines in the G2/M phase in hepatocellular carcinoma cell lines but not in the normal liver cell line. CONCLUSIONS: SG600-IL24 selectively induces growth suppression and apoptosis in hepatocellular carcinoma cell lines in vitro but not in the normal liver cell line L02. Compared with Ad.IL-24, SG600-IL24 dramatically enhances antitumor activity in hepatocellular carcinoma cell lines. (Hepatobiliary Pancreat Dis Int 2010; 9:615-621)

Oncolytic viruses against cancer stem cells: A promising approach for gastrointestinal cancer

Gastrointestinal cancer has been one of the five most commonly diagnosed and leading causes of cancer mortality over the past few decades. Great progress in traditional therapies has been made, which prolonged survival in patients with early cancer, yet tumor relapse and drug resistance still occurred, which is explained by the cancer stem cell(CSC) theory. Oncolytic virotherapy has attracted increasing interest in cancer because of its ability to infect and lyse CSCs. This paper reviews the basic knowledge, CSC markers and therapeutics of gastrointestinal cancer(liver, gastric, colon and pancreatic cancer), as well as research advances and possible molecular mechanisms of various oncolytic viruses against gastrointestinal CSCs. This paper also summarizes the existing obstacles to oncolytic virotherapy and proposes several alternative suggestions to overcome the therapeutic limitations.

Oncolytic adenovirus SG600-IL24 selectively kills hepatocellular carcinoma cell lines

AIM: To investigate the effect of oncolytic adenovirus SG600-IL24 and replication-incompetent adenovirus Ad.IL-24 on hepatocellular carcinoma (HCC) cell lines and normal liver cell line. METHODS: HCC cell lines (HepG2, Hep3B and MHCC97L) and normal liver cell line (L02) with a different p53 status were infected with SG600-IL24 and Ad.IL-24, respectively. Melanoma differentiation-associated (MDA)-7/interleukin (IL)-24 mRNA and protein expressions in infected cells were detected by reverse transcription-polymerase chain reaction (RT-PCR), enzymelinked immunosorbent assay (ELISA), and Western blotting, respectively. Apoptosis of HCC cells and normal liver cells was detected by cytometric assay with Hoechst33258 staining. 3-(4,5-dimethylthiazol-2-yl)-2,5diphenyltetrazolium bromide (MTT) assay was used to investigate proliferation of HCC cells and normal liver cells, and cell cycle was assayed by flow cytometry. RESULTS: RT-PCR, ELISA and Western blotting showed that the exogenous MDA-7/IL-24 gene was highly expressed in cells infected with SG600-IL24. MTT indicated that SG600-IL24 could suppress the growth of HepG2, Hep3B, MHCC97L, with an inhibition rate of 75% ± 2.5%, 85% ± 2.0%, 72% ± 1.8%, respectively (P < 0.01), promote the apoptosis of HepG2, Hep3B, MHCC97L, with an apoptosis rate of 56.59% ± 4.0%, 78.36% ± 3.5%, 43.39% ± 2.5%, respectively (P < 0.01), and block the HCC cell lines in the G2/M phase with a blocking rate of 35.4% ± 4.2%, 47.3% ± 6.2%, 42% ± 5.0%, respectively (P < 0.01) but not the normal liver cell line in a p53-independent manner. CONCLUSION: SG600-IL24 can selectively suppress the proliferation and apoptosis of HCC cell lines in vitro but not normal liver cell line L02 in a p53-independent manner. Compared with Ad.IL-24, SG600-IL24 can significantly enhance the antitumor activity in HCC cell lines.

Synergistic Antitumor Efficacy of Oncolytic Adenovirus Combined with Chemotherapy

Objective： Chemotherapy is an effective means of treating breast cancer, and cancer-specific replicative adenovirus is also a promising antitumor agent in recent years. Our investigation aims to demonstrate that CNHK300 can mediate selective antitumor efficacy and produce synergistic cytotoxicity with chemotherapy on HER-2 over-expressing breast cancer. Methods： We engineered the telomerase-dependent replicative adenovirus CNHK300 by placing the E1A gene under the control of the human hTERT promoter. By analysis of E1A expression, we proved the fidelity of hTERT promoter in adenovirus genome and the selective expression of E1A in telomerase-positive breast cancer cells but not in normal fibroblast cells. By proliferation test, we further showed efficient replication of CNHK300 in breast cancer cells with apparently attenuated proliferation in normal fibroblast cells. Finally, we demonstrated by MTT methods that CNHK300 virus caused potent cytolysis and produced synergistic cytotoxicity with chemotherapy in breast cancer cells with attenuated cytotoxicity on normal cells. Results： In this virus, the E1A gene is successfully placed under the control of the human hTERT promoter. CNHK300 virus replicated as efficiently as the wild-type adenovirus and caused intensive cell killing in HER-2 over-expressing breast cancer cells in vitro. In contrast, telomerase-negative normal fibroblast cells, which expressed no hTERT activity, were not able to support CNHK300 replication. Combined treatment of CNHK300 with paclitaxel improved cytotoxicity on cancer cells. Conclusion： We conclude that CNHK300 can produce selective antitumor efficacy and enhance the in vitro response of chemotherapy on HER-2 overexpressing breast cancer.

Mathematical Modeling and Analysis of Tumor Therapy with Oncolytic Virus

In this paper, we have proposed and analyzed a nonlinear mathematical model for the study of interaction between tumor cells and oncolytic viruses. The model is analyzed using stability theory of differential equa- tions. Positive equilibrium points of the system are investigated and their stability analysis is carried out. Moreover, the numerical simulation of the proposed model is also performed by using fourth order Runge- Kutta method which supports the theoretical findings. It is found that both infected and uninfected tumor cells and hence tumor load can be eliminated with time, and complete recovery is possible because of virus therapy, if certain conditions are satisfied. It is further found that the system appears to exhibit periodic limit cycles and chaotic attractors for some ranges of the system parameters.

Non-Linear Mathematical Model of the Interaction between Tumor and Oncolytic Viruses

A mathematical modeling of tumor therapy with oncolytic viruses is discussed. The model consists of two coupled, deterministic differential equations allowing for cell reproduction and death, and cell infection. The model is one of the conceptual mathematical models of tumor growth that treat a tumor as a dynamic society of interacting cells. In this paper, we obtain an approximate analytical expression of uninfected and infected cell population by solving the non-linear equations using Homotopy analysis method (HAM). Furthermore, the results are compared with the numerical simulation of the problem using Matlab program. The obtained results are valid for the whole solution domain.

Oncolytic virus therapy in cancer: A current review

In view of the advancement in the understanding about the most diverse types of cancer and consequently a relentless search for a cure and increased survival rates of cancer patients,finding a therapy that is able to combat the mechanism of aggression of this disease is extremely important.Thus,oncolytic viruses(OVs)have demonstrated great benefits in the treatment of cancer because it mediates antitumor effects in several ways.Viruses can be used to infect cancer cells,especially over normal cells,to present tumor-associated antigens,to activate“danger signals”that generate a less immune-tolerant tumor microenvironment,and to serve transduction vehicles for expression of inflammatory and immunomodulatory cytokines.The success of therapies using OVs was initially demonstrated by the use of the genetically modified herpes virus,talimogene laherparepvec,for the treatment of melanoma.At this time,several OVs are being studied as a potential treatment for cancer in clinical trials.However,it is necessary to be aware of the safety and possible adverse effects of this therapy;after all,an effective treatment for cancer should promote regression,attack the tumor,and in the meantime induce minimal systemic repercussions.In this manuscript,we will present a current review of the mechanism of action of OVs,main clinical uses,updates,and future perspectives on this treatment.

Oncolytic adenovirus targeting LASP-1 inhibited renal cell cancerprogression

Recent studies suggested that LIM and SH3 protein 1(LASP-1)is a promising therapeutic target for renal cell cancer(RCC).This study aimed to explore the role of LASP-1 in RCC.For this purpose,LASP-1 expression in RCC tissues was analyzed by immunohistochemistry and Western blot analysis.Cell proliferation,migration,invasion,and gene expression were detected by CCK-8 assay,Transwell assay,and Western blot analysis.The results showed that LASP-1 was highly expressed in RCC,and its expression level,t was positively correlated with lymph node metastasis and tumor,nodes,and metastases(TNM)stage.The knockdown of LASP-1 expression significantly inhibited the proliferation of RCC cells,increased the apoptosis rate,and inhibited RCC cell invasion and migration by inhibiting epithelial–mesenchymal transition.We conclude that LASP-1 promotes RCC progression and metastasis and is a promising therapeutic target for RCC.

Combined use of chemotherapeutics and oncolytic adenovirus in treatment of AFP-expressing hepatocellular carcinoma

BACKGROUND: Hepatocellular carcinoma (HCC) which is always refractory to most chemotherapeutic agents may result in poor survival of patients with advanced HCC. Oncolytic adenovirus is a new form for cancer gene therapy via its ability to replicate and kill tumor cells in a tumor-specific manner. In order to eradicate tumors effectively, the combination of chemotherapeutic agents and oncolytic adenovirus has been considered. This study aimed to systematically analyze the possibility of synergistic cytotoxicity of oncolytic adenoviruses in combination with chemotherapeutic agents. METHODS: Several types of human HCC cell lines were used to determine the specificity and cytotoxicity of oncolytic adenovirus Ad5-HC and Ad5-AFP (IRES) by measuring cell viability in vitro and antitumor efficiency in vivo. The cytotoxicity of Ad5-HC and Ad5-AFP (IRES) combined with chemotherapeutic agents were also assessed by the methyl thiazolyl tetrazolium assay. RESULTS: Both Ad5-HC and Ad5-AFP (IRES) were significantly cytotoxic to HCC cells with great specificity in vitro and in vivo. The combination of oncolytic adenovirus with 5-FU, doxorubicin, and paclitaxel was synergistically effective for the killing of HCC cells. CONCLUSIONS: These data suggest that oncolytic adenovirus sensitize tumors to chemotherapy and the combination therapy of chemotherapeutic agents and oncolytic adenovirus has an enhanced antitumor effect on HCC cells. (Hepatobiliary Pancreat Dis Int 2009; 8: 282-287)

Oncoselectivity in Oncolytic Viruses against Colorectal Cancer

In humans colorectal cancer (CRC) is a significant cause of morbidity and mortality. New treatment options are urgently needed to supplement existing therapies. Replication-competent oncolytic viruses (RCOVs) for the treatment of cancerous tumors?in vivo?is a relatively new therapeutic modality with great but largely unrealized potential against CRC. In the context of oncolytic virus safety, oncoselectivity is an important criterion. It is at the conceptual intersection of viral replication strategy and tumor cell biology that RCOVs acquire their oncoselectivity, and thus their safety. Every aspect of tumor molecular biology which distinguishes it from normal, non-neoplastic cells is a potential target for exploitation. In the first section of this review we will provide an explanation of some of the successful and widely used strategies for improving oncoselectivity in wild-type viruses to make them more suitable as RCOVs. In the second section we will describe some of the characteristics of CRC biology which can be exploited to provide oncoselectivity against CRC. Throughout the review examples of successfully-engineered RCOVs which embody the approach or strategy under discussion are noted. By showing what has been done, we hope to highlight what is possible and what remains to be done to generate oncoselective RCOVs for use against CRC in humans.

CXCL12 Retargeting of an Oncolytic Adenovirus Vector to the Chemokine CXCR4 and CXCR7 Receptors in Breast Cancer

Breast cancer is the most frequently diagnosed cancer in women under 60, and the second most diagnosed cancer in women over 60. While significant progress has been made in developing targeted therapies for breast cancer, advanced breast cancer continues to have high mortality, with poor 5-year survival rates. Thus, current therapies are insufficient in treating advanced stages of breast cancer;new treatments are sorely needed to address the complexity of advanced-stage breast cancer. Oncolytic virotherapy has been explored as a therapeutic approach capable of systemic administration, targeting cancer cells, and sparing normal tissue. In particular, oncolytic adenoviruses have been exploited as viral vectors due to their ease of manipulation, production, and demonstrated clinical safety profile. In this study, we engineered an oncolytic adenovirus to target the chemokine receptors CXCR4 and CXCR7. The overexpression of CXCR4 and CXCR7 is implicated in the initiation, survival, progress, and metastasis of breast cancer. Both receptors bind to the ligand, CXCL12 (SDF-1), which has been identified to play a crucial role in the metastasis of breast cancer cells. This study incorporated a T4 fibritin protein fused to CXCL12 into the tail domain of an adenovirus fiber to retarget the vector to the CXCR4 and CXCR7 chemokine receptors. We showed that the modified virus targets and infects CXCR4- and CXCR7-overexpressing breast cancer cells more efficiently than a wild-type control vector. In addition, the substitution of the wild-type fiber and knob with the modified chimeric fiber did not interfere with oncolytic capability. Overall, the results of this study demonstrate the feasibility of retargeting adenovirus vectors to chemokine receptor-positive tumors.

Oncolytic Herpes Simplex Virus ICP47 Deletion Reverses Tumor Immune Evasion

Herpes simplex virus (HSV) is an enveloped, double-stranded DNA virus that has been used with modification as oncolytic viruses (OVs) against a number of tumor types. OVs represent a new class of therapeutic agents that promote anti-tumour responses through a dual mechanism of action that is dependent on selective tumor cell killing and the induction of systemic anti-tumour immunity. Among OVs, HSVs preferentially replicate in and lyse cancer cells, leading to in situ autovaccination, adaptive anti-virus and anti-tumor immunity. Suppression of antitumor immunity after OV therapy has been observed and the molecular and cellular mechanisms of action are recently reported. ICP47, a small protein produced by the herpes simplex virus, is considered as an important factor in the evasion of cellular immune responses in HSV-infected cells. Therefore, reviewing the research status of ICP47 is certainly helpful to improve the anti-tumor effect of oncolytic HSVs (oHSVs). Here, this review will focus on the following contents: 1) Anti-tumor mechanism of OVs;2) Functions of early HSV genes;3) The mechanism of immune escape of ICP47;4) Recombinant HSV against cancer;5) The functional verification of ICP47 deletion. This review highlights the current understanding of recombinant HSVs against cancers.

Oncolytic Engineering of ICP34.5 and LAT of Herpes Simplex Virus Type 1

Oncolytic virus (OV) is a kind of virus that can preferentially infect and kill tumor cells. The second oncolytic virus drug was oncolytic herpes simplex virus (oHSV) Talimogene Laherparepvec (T-VEC). HSV-1 infectious cell culture protein 34.5 (ICP34.5) and latency-associated transcript (LAT) genes are closely related to virus selective infection and latent infection. Their engineering is essential for constructing efficient and safe oHSV. We summarized the mechanisms of ICP34.5 and LAT in the course of HSV-1 infection and reviewed the engineered oHSVs. We are aimed to provide an insight in developing oHSV in the future.

Novel Functional Motifs of the Cell Entry Glycoprotein D for Oncolytic Herpes Simplex Viruses

Background: Oncolytic herpes simplex virus (oHSV) have been proved effective and safe to treat tumors. Glycoprotein D (gD) has been engineered for targeting cancer cells and de-targeting normal cells successfully, however, the effectiveness and safety of oHSVs still need to be improved. Method: Here we sequenced the DNA encoding gD of our recently isolated new strain HSV-1-LXMW and compared the gD amino acid sequence with the gDs of other 7 HSV-1 and 3 HSV-2 strains. Results: Phylogenetic analysis revealed that HSV-1-LXMW is evolutionarily close to HSV-1-Patton and -KOS strains. The gD amino acid sequence alignment identified 19 conserved and 8 variable regions. We further predicted 10 new motifs in HSV gD for the first time and identified motif differences in HSV-1 and HSV-2. We summarized the gD-engineered oHSVs and found that some of the newly identified gD motifs are actually functional. Conclusion: Our results shed light on HSV gD biology and provided new directions for future gD functional studies and engineering in order to make better oHSVs.

Polymer-based synthetic oncolytic virus-like nanoparticles for cancer immunotherapy

Oncolytic viruses have emerged as new powerful therapeutic agents for cancer therapy by specifically lysing cancer cells while activating innate immune responses at the same time.However,due to the thorny issues of safety concerns and host immune reaction,the clinical application of oncolytic viruses is still limited.Herein,we report a rationally designed oncolytic virus-like nanoparticles(OV-NPs)composed of stimulator of interferon genes(STING)-stimulating polymer loaded with therapeutic genes for cancer immunotherapy.After injection into tumor,the OV-NPs carrying OX40L plasmid could reprogram tumor cells to express OX40L immune checkpoint molecules and activate the STING pathway for cooperatively enhancing antitumor immunity,with a tumor suppression rate of 92.3%in B16F10 tumor model and 78.7%in MC38 tumor model without causing any toxicity.The OV-NPs could be further applied in carrying other plasmids(IL-12)and utilization in gene combination therapy.This study should inspire designing synthetic OV-NPs as alternative strategies for extending oncolytic virus application in cancer immunotherapy.

Therapeutic potential of oncolytic viruses in the era of precision oncology

Oncolytic virus(OV)therapy has been shown to be an effective targeted cancer therapy treatment in recent years,providing an avenue of treatment that poses no damage to surrounding healthy tissues.Not only do OVs cause direct oncolysis,but they also amplify both innate and adaptive immune responses generating long-term anti-tumour immunity.Genetically engineered OVs have become the common promising strategy to enhance anti-tumour immunity,safety,and efficacy as well as targeted delivery.The studies of various OVs have been accomplished through phase I-III clinical trial studies.In addition,the uses of carrier platforms of organic materials such as polymer chains,liposomes,hydrogels,and cell carriers have played a vital role in the potentially targeted delivery of OVs.The mechanism,rational design,recent clinical trials,applications,and the development of targeted delivery platforms of OVs will be discussed in this review.