Treatment of Cancer with a Novel Dual-Targeted Conditionally Replicative Adenovirus Armed with mda-7/IL-24 Gene

Oncolytic Adenovirus in Cancer Immunotherapy

Tumor-selective replicating "oncolytic" viruses are novel and promising tools for immunotherapy of cancer. However, despite their first success in clinical trials, previous experience suggests that currently used oncolytic virus monotherapies will not be effective enough to achieve complete tumor responses and long-term cure in a broad spectrum of cancers. Nevertheless, there are reasonable arguments that suggest advanced oncolytic viruses will play an essential role as enablers of multi-stage immunotherapies including established systemic immunotherapies. Oncolytic adenoviruses (oAds) display several features to meet this therapeutic need. oAds potently lyse infected tumor cells and induce a strong immunogenic cell death associated with tumor inflammation and induction of antitumor immune responses. Furthermore, established and versatile platforms of oAds exist, which are well suited for the incorporation of heterologous genes to optimally exploit and amplify the immunostimulatory effect of viral oncolysis. A considerable spectrum of functional genes has already been integrated in oAds to optimize particular aspects of immune stimulation including antigen presentation, T cell priming, engagement of additional effector functions, and interference with immunosuppression. These advanced concepts have the potential to play a promising future role as enablers of multi-stage immunotherapies involving adoptive cell transfer and systemic immunotherapies.

Interleukin-24 enhancing antitumor activity of chimeric oncolytic adenovirus for treating acute promyelocytic leukemia cell

BACKGROUND

Acute promyelocytic leukaemia (APL) is a clonal disease arising by hematopoietic stem cell (HSC), which characterized by inappropriate proliferation/differentiation or survival of immature myeloid progenitors. Oncolytic adenoviruses have been under widespread investigation as anticancer agents. Recently, our data suggested that tumor cells were cured by AdCN205-IL-24, an adenovirus serotype 5-based conditionally replicating adenovirus expressing IL-24 after infection.

METHODS

In this study, we created a novel fiber chimeric oncolytic adenovirus AdCN306-IL-24 that has Ad11 tropism and approved CAR (coxsackie adenovirus receptor, CAR)-independent cell entry, which could allow development of selective cytopathic effects (CPE) in APL cells in vitro.

RESULTS

Formidable cytotoxic effect was specifically implemented in APL cells after infection with AdCN306-IL-24. The expression of IL-24 was up-regulated upon treated with accepted tumors. And the vector also induced superior cytolytic effects activity in APL cells by activation of programmed cell death.

CONCLUSIONS

Taken together, our data suggested that chimeric oncolytic adenovirus AdCN306-IL-24 could express IL-24 gene, representing a potential therapeutics for acute promyelocytic leukemia.

An oncolytic adenovirus that expresses the HAb18 and interleukin 24 genes exhibits enhanced antitumor activity in hepatocellular carcinoma cells

Hepatocellular carcinoma (HCC) is characterized by alterations in multiple genes. High expression of CD147 on the surface of HCC cells promotes proliferation. The monoclonal antibody HAb18 recognizes CD147. We constructed an oncolytic adenoviral vector to express HAb18 (ZD55-HAb18) in HCC cells. Interleukin 24 (IL24) was co-expressed through the use of an F2A linker. ZD55-HAb18-IL24 decreased HCC cell viability to a greater degree than either ZD55-HAb18 or ZD55-IL24 alone. ZD55-HAb18-IL24 also induced apoptosis and autophagy in PLC/PRF/5 HCC cells. Intratumoral injection of ZD55-HAb18-IL24 repressed tumor growth in a PLC/PRF/5 xenograft model. Our results suggest that antibody-antitumor gene conjugation elicited a stronger antitumor effect than the antibody alone, and that this strategy could broaden the applications of antibody-based therapies in HCC.

A hypoxia- and telomerase-responsive oncolytic adenovirus expressing secretable trimeric TRAIL triggers tumour-specific apoptosis and promotes viral dispersion in TRAIL-resistant glioblastoma

Glioblastoma is a highly aggressive and malignant type of cancer that is apoptosis resistant and difficult to cure by conventional cancer therapies. In this regard, an oncolytic adenovirus that selectively targets the tumour tissue and induces tumour cell lysis is a promising treatment option. We designed and constructed a hypoxia-responsive and cancer-specific modified human telomerase reverse transcriptase (H5CmTERT) promoter to drive replication of an oncolytic adenovirus (H5CmTERT-Ad). To enhance the anti-tumour efficacy of H5CmTERT-Ad against malignant glioblastoma, we also generated an H5CmTERT-Ad expressing secretable trimeric tumour necrosis factor-related apoptosis-inducing ligand (H5CmTERT-Ad/TRAIL). H5CmTERT promoter-regulated oncolytic adenoviruses showed cancer-specific and superior cell-killing effect in contrast to a cognate control oncolytic adenovirus replicating under the control of the endogenous adenovirus promoter. The cancer cell-killing effects of H5CmTERT-Ad and H5CmTERT-Ad/TRAIL were markedly higher during hypoxia than normoxia owing to hypoxia responsiveness of the promoter. H5CmTERT-Ad/TRAIL showed more potent anti-tumour efficacy than H5CmTERT-Ad did in a xenograft model of TRAIL-resistant subcutaneous and orthotopic glioblastoma through superior induction of apoptosis and more extensive virus distribution in the tumour tissue. Altogether, our findings show that H5CmTERT-Ad/TRAIL can promote dispersion of an oncolytic adenovirus through robust induction of apoptosis in a highly TRAIL-resistant glioblastoma.

Simultaneous overexpression of miR-126 and miR-34a induces a superior antitumor efficacy in pancreatic adenocarcinoma

Background

Pancreatic adenocarcinoma (PAC) is one of the most fatal cancers due to its high degree of malignancy, increasing incidence, high mortality, and unsatisfactory treatment efficacy. Evidence has suggested that numerous microRNAs (miRNAs), including miR-126 and miR-34a, have potent tumor-suppressing effects on PAC, implicating a possible application of miRNA in tumor therapy. However, the therapeutic effect of a single miRNA on pancreatic cancer is limited.

Methods

We simultaneously delivered miR-126 and miR-34a into PAC cells by a carcinoembryonic antigen promoter-driven oncolytic adenovirus (AdCEAp-miR126/34a), and examined the antitumor efficacy of the therapeutic system in in vitro and in vivo experiments.

Results

In vitro cytological experiments found that the expression levels of miR-126 and miR-34a were specifically increased in the AdCEAp-miR126/34a-infected PAC cells, and the antitumor efficacy was enhanced in aspects of cancer cell viability, migration, invasion, and apoptosis, by synergistically combining the antitumor effects of overexpressed miR-126 and miR-34a and the oncolytic effect of viral replication specifically in PAC cells. The expression levels of miR-126 target genes (vascular endothelial growth factor-A and SOX2) and miR-34a target genes (cyclin D1, E2F1, and Bcl-2) were markedly decreased in the PAC cells after being infected with AdCEAp-miR126/34a. Notable suppression of the therapeutic system on tumor growth was also proven in established PAC xenograft tumor models in nude mice, which demonstrated that the combination of miR-126 and miR-34a exerts more effective antitumor outcomes than a single miRNA.

Conclusion

The therapeutic system co-expressing miR-126 and miR-34a mediated by oncolytic adenovirus is a promising system for PAC target therapy.

Mechanism of Action and Applications of Interleukin 24 in Immunotherapy

Interleukin 24 (IL-24) is an important pleiotropic immunoregulatory cytokine, whose gene is located in human chromosome 1q32-33. IL-24's signaling pathways have diverse biological functions related to cell differentiation, proliferation, development, apoptosis, and inflammation, placing it at the center of an active area of research. IL-24 is well known for its apoptotic effect in cancer cells while having no such effect on normal cells. IL-24 can also be secreted by both immune and non-immune cells. Downstream effects of IL-24, after binding to the IL-20 receptor, can occur dependently or independently of the JAK/STAT signal transduction pathway, which is classically involved in cytokine-mediated activities. After exogenous addition of IL-24, apoptosis is induced in tumor cells independently of the JAK/STAT pathway. We have shown that IL-24 binds to Sigma 1 Receptor and this event induces endoplasmic reticulum stress, calcium mobilization, reactive oxygen species generation, p38MAPK activity, and ceramide production. Here we review IL-24's role in autoimmunity, infectious disease response, wound repair, and vascular disease. Detailed understanding of the pleiotropic roles of IL-24 signaling can assist in the selection of more accurate therapeutic approaches, as well as targeting of appropriate cell types in treatment strategy development, and ultimately achieve desired therapeutic effects.

A combinatory use of adenoviruses expressing melanoma differentiation-associated gene-7 and replication-competent adenoviruses produces synergistic effects on pancreatic carcinoma cells

Type 5 adenoviruses expressing mda-7 gene (Ad-mda-7) induced cell death in various kinds of human tumors, but pancreatic carcinoma cells were relatively resistant to Ad-mda-7-mediated cytotoxicity. We then examined whether infection of Ad-mda-7 together with replication-competent Ad produced combinatory cytotoxic effects. We prepared replication-competent Ad, defective of the E1B55kDa gene or activated by a transcriptional regulatory region of the midkine or the survivin gene of which the expression was up-regulated in human tumors. Type 5 Ad bearing the exogenous regulatory region were further modified by replacing the fiber-knob region with that of type 35 Ad. Pancreatic carcinoma cells were infected with replication-incompetent Ad-mda-7 and the replication-competent Ad. Combinatory effects were examined with the CalcuSyn software and cell cycle analyses. Ad-mda-7 and the replication-competent Ad achieved cytotoxicity to pancreatic carcinoma. A combinatory use of Ad-mda-7 and either Ad defective of the E1B55kDa gene or Ad activated by the regulatory region produced synergistic cytotoxic effects. Cell cycle analyses demonstrated that the combination increased sub-G1 populations. These data collectively suggest that expression of MDA-7 augments cytotoxicity of replication-competent Ad and achieves adjuvant effects on Ad-mediated cell death.

Oncolytic adenovirus‑mediated mda‑7/IL‑24 expression suppresses osteosarcoma growth and enhances sensitivity to doxorubicin

Osteosarcoma (OS) is a malignant disease with a high mortality rate and poor response to current chemotherapy. Melanoma differentiation associated gene‑7 (Mda7)/interleukin (IL)‑24 has been demonstrated to suppress the growth of OS. However, the expression level of Mda7/IL‑24 mediated by the current adenoviral vector is limited for effective clinical treatment of OS. In order to solve this issue, an oncolytic adenovirus was employed to express IL‑24 (OA‑IL‑24) in OS cells. Quantitative polymerase chain reaction, immunoblot and ELISA assays verified that OA‑IL‑24 expressed IL‑24 at a higher level than the replication‑deficient adenoviral vector, Ad‑IL24. OA‑IL‑24 infection led to decreased cell viability and increased apoptosis of OS cells, compared with Ad‑IL‑24. Animal studies further confirmed the increased anti‑tumor activity of OA‑IL‑24. Notably, OA‑IL‑24 was also found to sensitize OS cells to doxorubicin. OA‑IL‑24‑induced multiple drug resistance reversion was associated with reduced expression of Pgp and BCRP1, as well as minimized autophagy. Furthermore, restoring Pgp and BCRP1 expression as well as autophagy, was able to rescue the effect of IL‑24 on the cytotoxicity of doxorubicin to OS. In conclusion, a method for inducing a high expression of IL‑24 in OS was provided. In addition, IL‑24 was demonstrated to increase the sensitivity of OS to doxorubicin.

MicroRNAs and oncolytic viruses

MicroRNAs regulate gene expression in mammalian cells and often exhibit tissue-specific expression patterns. Incorporation of microRNA target sequences can be used to control exogenous gene expression and viral tropism in specific tissues to enhance the therapeutic indices of oncolytic viruses expressing therapeutic transgenes. Continued development of this targeting strategy has resulted in the generation of unattenuated oncolytic viruses with enhanced potency, broad species-tropisms and reduced off-target toxicities in multiple-tissues simultaneously. Furthermore, oncolytic viruses have been used to enhance the delivery, duration and therapeutic efficacy of microRNA-based therapeutics designed to either restore or inhibit the function of dysregulated microRNAs in cancer cells. Recent efforts focused on combining oncolytic virotherapy and microRNA regulation have generated increasingly potent and safe cancer therapeutics.

Sorting Out Pandora's Box: Discerning the Dynamic Roles of Liver Microenvironment in Oncolytic Virus Therapy for Hepatocellular Carcinoma

Oncolytic viral therapies have recently found their way into clinical application for hepatocellular carcinoma (HCC), a disease with limited treatment options and poor prognosis. Adding to the many intrinsic challenges of in vivo oncolytic viral therapy, is the complex microenvironment of the liver, which imposes unique limitations to the successful delivery and propagation of the virus. The normal liver milieu is characterized by an intricate network of hepatocytes and non-parenchymal cells including Kupffer cells, stellate cells, and sinusoidal endothelial cells, which can secrete anti-viral cytokines, provide a platform for non-specific uptake, and form a barrier to efficient viral spread. In addition, natural killer cells are greatly enriched in the liver, contributing to the innate defense against viruses. The situation is further complicated when HCC arises in the setting of underlying hepatitis virus infection and/or hepatic cirrhosis, which occurs in more than 90% of clinical cases. These conditions pose further inhibitory effects on oncolytic virus (OV) therapy due to the presence of chronic inflammation, constitutive cytokine expression, altered hepatic blood flow, and extracellular matrix deposition. In addition, OVs can modulate the hepatic microenvironment, resulting in a complex interplay between virus and host. The immune system undoubtedly plays a substantial role in the outcome of OV therapy, both as an inhibitor of viral replication, and as a potent mechanism of virus-mediated tumor cell killing. This review will discuss the particular challenges of oncolytic viral therapy for HCC, as well as some potential strategies for modulating the immune system and synergizing with the hepatic microenvironment to improve therapeutic outcome.

Tumor-targeting TRAIL expression mediated by miRNA response elements suppressed growth of uveal melanoma cells

Malignant uveal melanoma severely damages eye function and is prone to metastasize to other organs. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a promising agent to treat uveal melanoma because of its induction of apoptosis in cancer cells both at primary and metastatic sites. However, TRAIL therapy lacks tumor specificity in the current delivery systems for uveal melanoma treatment, thereby causing cytotoxiciy to normal tissues. To improve uveal melanoma specificity of adenovirus-based TRAIL introduction, we used miRNA response elements (MREs) of miR-34a, miR-137 and miR-182, which have been shown to have reduced expression in uveal melanoma cells, to regulate its expression. miR-34a, miR-137 and miR-182 all had lower expression levels in uveal melanoma cell lines, compared with normal cells. MREs-regulated luciferase activity was reduced in normal cell lines, but not significantly attenuated in uveal melanoma cells. The infection of MRE-regulated TRAIL-expressing adenoviral vector (Ad-TRAIL-3MREs) led to high level of TRAIL expression in uveal melanoma cell lines, but not in normal cells. Strong expression of TRAIL had a high anti-tumor capacity by inducing apoptosis in uveal melanoma cells. In contrast, Ad-TRAIL-3MREs had no cytotoxicity to normal cell lines. Animal experiments further confirmed tumor-suppressing effect of Ad-TRAIL-3MREs on uveal melanoma xenografts and its biosafety to hepatic tissues. Collectively, we constructed an MRE-directed TRAIL-expressing adenoviral vector and provided evidence that this vector possessed high anti-tumor activity and uveal melanoma specificity.

Chapter four--Design of improved oncolytic adenoviruses

During the last decade adenovirus has lost its appeal in gene therapy due to a high immunogenicity that leads to a transient gene expression. However, adenovirus has gained attention as replication-competent vector to treat cancer. Designed for virotherapy, adenovirus has been successfully modified to replicate selectively in tumor cells. After the initial clinical trials with tumor-selective adenoviruses, it has become clear that further improvements on tumor targeting, intratumoral dissemination, and modulation of antiviral and antitumor immune responses are needed to effectively treat cancer. The non-viral delivery of infectious DNA encoding an oncolytic adenovirus armed with extracellular matrix-degrading genes and with genes that regulate the immune system to favor antitumor instead of antiviral immunity are key in the design oncolytic adenovirus.

Conditionally replicative adenovirus-based mda-7/IL-24 expression enhances sensitivity of colon cancer cells to 5-fluorouracil and doxorubicin

BACKGROUND

Multiple drug resistance (MDR) greatly limits the efficacy of chemotherapy for colon cancer. An adenovirus armed with Melanoma differentiation associated gene-7/interleukin-24 (mda-7/IL-24; abbreviated to 'IL-24' here) was shown to reverse the MDR of colon cancer cells to oxaliplatin and doxorubicin. However, the relatively low expression level of IL-24 mediated by a replication-deficient adenoviral vector hindered its clinical application.

METHODS

To enhance IL-24-dependentreversion of the MDR phenotype, we utilized a conditionally replicative adenoviral vector, AdBB-IL24, to express IL-24 at a high level for more efficient MDR reversion.

RESULTS

An enzyme-linked immunosorbent assay (ELISA) suggested conditionally replicative adenoviral vector-mediated IL-24 expression was elevated in comparison with that of a replication-deficient adenoviral vector, Ad-IL24. AdBB-IL24 was shown to reverse MDR in colon cancer cells more potently than Ad-IL24. The AdBB-IL24-induced MDR reversion was linked to reduced P-glycoprotein (Pgp) and breast cancer resistance protein 1 (BCRP1) expression. Consistently, 5-fluorouracil and doxorubicin induced more apoptosis in AdBB-IL24-infected colon cancer cells compared with that in the Ad-IL24-infected cells. A cell viability assay showed that AdBB-IL24 could enhance the growth-inhibitory effect of 5-fluorouracil and doxorubicin on colon cancer cells more effectively than Ad-IL24 in vitro. In a mouse model, we also found that the combination of 5-fluorouracil and doxorubicin with AdBB-IL24 completely inhibited the growth of colon cancer cells.

CONCLUSION

We here provide evidence supporting conditionally replicative adenoviral vector-based gene therapy as a powerful strategy to enhance mda7/IL-24-dependent MDR reversion of colon cancer cells.

Oncolytic adenovirus co-expressing miRNA-34a and IL-24 induces superior antitumor activity in experimental tumor model

It has been demonstrated that numerous microRNAs (miRNAs) have potent tumor-suppressing effects on a variety of cancers, implicating a possible application of miRNA in tumor therapy. Oncolytic adenovirus is a suitable vector to deliver tumor suppressor genes for treatment of cancers. However, it remains unknown whether co-expression of tumor suppressor genes and miRNAs can contribute to a more potent antitumor capacity within an oncolytic adenovirus delivery system. In this study, we found that expression of miRNA-34a was reduced in hepatocellular carcinoma (HCC), and the reduced expression of miRNA-34a was associated with worse outcome of HCC patients. Thus, we developed an oncolytic adenoviral vector, AdCN205, to co-express miRNA-34a and IL-24 driven by an adenovirus endogenous E3 promoter in HCC cells. High levels of miRNA-34a and IL-24 expression were detected in AdCN205-IL-24-miR-34a-infected HCC cells. AdCN205-IL-24-miR-34a significantly induced dramatic antitumor activity, as compared with that induced by AdCN205-IL-24 or AdCN205-miR-34a alone. Transfer of miRNA-34a into HCC cells inhibited the expression of its target genes, Bcl-2 and SIRT1. Treatment of established xenograft HCC tumors with AdCN205-IL-24-miR-34a in a mouse model resulted in complete tumor regression without recurrence. Taken together, our data provide a promising and reasonable delivery strategy of double-aimed cancer therapy, in which miRNAs and tumor-suppressing genes are used simultaneously.

Combined therapy with cytokine-induced killer cells and oncolytic adenovirus expressing IL-12 induce enhanced antitumor activity in liver tumor model

Both adoptive immunotherapy and gene therapy hold a great promise for treatment of malignancies. However, these strategies exhibit limited anti-tumor activity, when they are used alone. In this study, we explore whether combination of cytokine-induced killer (CIK) adoptive immunotherapy with oncolytic adenovirus-mediated transfer of human interleukin-12 (hIL-12) gene induce the enhanced antitumor potency. Our results showed that oncolytic adenovirus carrying hIL-12 (AdCN205-IL12) could produce high levels of hIL-12 in liver cancer cells, as compared with replication-defective adenovirus expressing hIL-12 (Ad-IL12). AdCN205-IL12 could specifically induce cytotoxocity to liver cancer cells. Combination of CIK cells with AdCN205-IL12 could induce higher antitumor activity to liver cancer cells in vitro than that induced by either CIK or AdCN205-IL12 alone, or combination of CIK and control vector AdCN205-GFP. Furthermore, treatment of the established liver tumors with the combined therapy of CIK cells and AdCN205-IL12 resulted in tumor regression and long-term survival. High level expression of hIL-12 in tumor tissues could increase traffic of CIK cells to tumor tissues and enhance their antitumor activities. Our study provides a novel strategy for the therapy of cancer by the combination of CIK adoptive immunotherapy with oncolytic adenovirus-mediated transfer of immune stimulatory molecule hIL-12.

Conditionally replicating adenoviruses carrying mda-7/IL-24 for cancer therapy

BACKGROUND

Melanoma differentiation associated gene-7/interleukin-24 (mda-7/IL-24) suppresses growth and induces apoptosis in a broad range of human cancers without significant cytotoxicity to normal cells. Conditionally replicating adenoviruses (CRAds) not only have the ability to destroy cancer cells but may also be potential vectors for the expression of therapeutic genes.

METHODS

This review provides an overview of specifications for a novel anti-tumor approach CRAds carrying IL-24, and discusses recent progress in this field.

RESULTS

Studies in multiple laboratories report that CRAds carrying IL-24 selectively induced apoptosis in some cancer cells, and enhanced selective toxicity to cancer cells when combined with chemotherapeutic agents.

CONCLUSION

CRAds carrying IL-24 may prove a novel and effective approach for the treatment of cancers.

Potent growth-inhibitory effect of TRAIL therapy mediated by double-regulated oncolytic adenovirus on osteosarcoma

Osteosarcoma (OS) severely threatens the health of young people and understanding on the molecular mechanisms of OS etiology enables gene therapy to become an effective therapeutic modality. However, insufficient expression level of genes using existing vectors limits the clinical application of gene therapy for OS. To solve the problem, we developed an oncolytic adenoviral vector, OAT, which can selectively and efficiently replicate in OS cells to enhance the expression of transferred genes. We demonstrated that OAT-mediated TRAIL expression is significantly elevated after infection of OS cells than replication-incompetent Ad5 vector. Increased antitumor capacity was observed in OS cells after OAT-TRAIL treatment both in vitro and in vivo. In normal cells, adenoviral replication, TRAIL expression and growth-inhibiting effect were quite limited when OAT-TRAIL was administrated, showing a high biosafety of this oncolytic adenoviral vector. Collectively, we generated an efficient and promising expression vector for OS gene therapy.

Potent antitumor activity of oncolytic adenovirus-mediated SOCS1 for hepatocellular carcinoma

Signal transducer and activator of transcription 3 (STAT3) is constitutively activated in diverse cancers, which contributes to the proliferation and survival of cancer cells by upregulating apoptosis inhibitors and cell cycle regulators. Suppressor of cytokine signaling 1 (SOCS1) is an important negative regulator of STAT pathways and is frequently silenced in many types of cancers. In this study, we used oncolytic adenoviral vector to deliver SOCS1 gene (AdCN305-SOCS1) to treat hepatocellular carcinoma (HCC). Our data showed that SOCS1 was downregulated in HCC cells by hypermethylation. AdCN305-SOCS1 was found selectively replicated, which led to SOCS1 overexpression in HCC cells. Infection of HCC cells with AdCN305-SOCS1 resulted in inhibition of STAT3 phosphorylation and downregulation of survivin, cyclin D1, Bcl-xL and C-myc. AdCN305-SOCS1 exhibited strong cytotoxicity to HCC cells by inducing apoptosis in vitro and in vivo. This study suggests that transfer of SOCS1 by an oncolytic adenovirus may be a potent antitumor approach for cancer therapy.

Replicating viral vectors for cancer therapy: strategies to synergize with host immune responses

Tumour‐specific replicating (oncolytic) viruses are novel anticancer agents, currently under intense investigation in preclinical studies and phase I–III clinical trials. Until recently, most studies have focused on the direct antitumour properties of these viruses. There is now an increasing body of evidence indicating that host immune responses may be critical to the efficacy of oncolytic virotherapy. Although the immune response to oncolytic viruses can rapidly restrict viral replication, thereby limiting the efficacy of therapy, oncolytic virotherapy also has the potential to induce potent antitumoural immune effectors that destroy those cancer cells, which are not directly lysed by virus. In this review, we discuss the role of the immune system in terms of antiviral and antitumoural responses, as well as strategies to evade or promote these responses in favour of improved therapeutic potentials.

Adenovirus-mediated human interleukin 24 (MDA-7/IL-24) selectively suppresses proliferation and induces apoptosis in keloid fibroblasts

Keloids are fibroproliferative dermal lesions characterized by the proliferation of fibroblasts and the formation of excess scar tissue, for which no effective treatment exists. We transfected a replication-incompetent adenovirus vector expressing green fluorescent protein and interleukin-24 gene (Ad-GFP/IL-24) into keloid fibroblasts (KF) and normal dermal fibroblasts (NDF) in vitro to investigate the suppression effects by observation on cell lines growth, apoptosis, mitosis cycle, etc. The expression of GFP and IL-24 mRNA confirmed that Ad-GFP/IL-24 was transfected into KF and NDF successfully. The expression level of secreting IL-24 protein detected by enzyme-linked immunosorbent assay in Ad-GFP/IL-24-treated KF and PBS-treated NDF was higher than controls; treatment with Ad-GFP/IL-24 in KF induced growth suppression (71.83% ± 6.67%, P < 0.05 to 9.79% ± 3.34%, P < 0.01), apoptosis (24.2% ± 3.08% to 66.51% ± 5.29%, P < 0.01) and increased the percentage of the G2/M phase (42.26% ± 6.44%, P < 0.01) in KF but not in NDF. The data showed that the exogenous IL-24 gene could selectively inhibit human KF proliferation and induce significant apoptosis.

A novel conditionally replicating "armed" adenovirus selectively targeting gastrointestinal tumors with aberrant wnt signaling

Using conditionally replicating adenoviral vectors (CRAds) is a promising strategy in the treatment of solid tumors. The prospective of this study was to design a novel CRAd for the treatment of gastrointestinal cancer and show its efficacy in vitro, as well as in vivo. To determine if aberrant wnt signaling in tumor cells can be used to selectively drive viral replication, we analyzed six colorectal and hepatocellular cell lines, as well as 13 colorectal tumors and 17 gastric tumors, for β-catenin mutation status or aberrant wnt signaling, both of which were found frequently. Based on these findings, a novel CRAd (Ad5F11.wnt-E1A-hIL24) containing an E1A expression cassette driven by an artificial wnt promoter and delivering an apoptosis-inducing gene, interleukin-24 (IL24), was engineered. To enhance infection efficiency, the virus was pseudotyped by replacing adenovirus serotype 5 (Ad5) with Ad11 fiber. Ad5F11.wnt-E1A-hIL24 virus exhibited high selectivity toward cells with aberrant wnt signaling both in vitro and in mouse xenograft tumors. Transduction efficiency was significantly improved compared with that of nonpseudotyped control viruses. The proliferation of tumor cell lines, as well as tumor growth, in mouse xenografts could be profoundly inhibited by viral infection with Ad5F11.wnt-E1A-hIL24. The therapeutic effect was associated with increased apoptosis through caspase-3 activation. In addition, Ad5F11b vector exhibited a more favorable biodistribution, blood clearance, and transgene expression compared with conventional Ad5 vector after systemic or intratumoral injection in human gastrointestinal cancer xenografts. We think that our approach is a promising strategy in the treatment of gastrointestinal cancer, warranting further clinical investigation.

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), enzyme-linked 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)-2,5-diphenyltetrazolium 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.

"Buy one get one free": armed viruses for the treatment of cancer cells and their microenvironment

Oncolytic viral therapy is a promising biological therapy for the treatment of cancer. Recent advances in genetic engineering have facilitated the construction of custom-built oncolytic viruses that can be exquisitely targeted to tumors by exploiting each cancer's unique biology and their efficacy can be further enhanced by "arming" them with additional therapeutic genes. Such an approach allows the virus to unload its "therapeutic cargo" at the tumor site, thereby enhancing its anti-neoplastic properties. While several clever strategies have been recently described using genes that can induce cellular apoptosis/suicide and/or facilitate tumor/virus imaging, viruses armed with genes that also affect the tumor microenvironment present an exciting and promising approach to therapy. In this review we discuss recently developed oncolytic viruses armed with genes encoding for angiostatic factors, inflammatory cytokines, or proteases that modulate the extracellular matrix to regulate tumor vascularization, anti-tumor immune responses and viral spread throughout the solid tumor.

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.

Chemical modification with high molecular weight polyethylene glycol reduces transduction of hepatocytes and increases efficacy of intravenously delivered oncolytic adenovirus

Oncolytic adenoviruses are anticancer agents that replicate within tumors and spread to uninfected tumor cells, amplifying the anticancer effect of initial transduction. We tested whether coating the viral particle with polyethylene glycol (PEG) could reduce transduction of hepatocytes and hepatotoxicity after systemic (intravenous) administration of oncolytic adenovirus serotype 5 (Ad5). Conjugating Ad5 with high molecular weight 20-kDa PEG but not with 5-kDa PEG reduced hepatocyte transduction and hepatotoxicity after intravenous injection. PEGylation with 20-kDa PEG was as efficient at detargeting adenovirus from Kupffer cells and hepatocytes as virus predosing and warfarin. Bioluminescence imaging of virus distribution in two xenograft tumor models in nude mice demonstrated that PEGylation with 20-kDa PEG reduced liver infection 19- to 90-fold. Tumor transduction levels were similar for vectors PEGylated with 20-kDa PEG and unPEGylated vectors. Anticancer efficacy after a single intravenous injection was retained at the level of unmodified vector in large established prostate carcinoma xenografts, resulting in complete elimination of tumors in all animals and long-term tumor-free survival. Anticancer efficacy after a single intravenous injection was increased in large established hepatocellular carcinoma xenografts, resulting in significant prolongation of survival as compared with unmodified vector. The increase in efficacy was comparable to that obtained with predosing and warfarin pretreatment, significantly extending the median of survival. Shielding adenovirus with 20-kDa PEG may be a useful approach to improve the therapeutic window of oncolytic adenovirus after systemic delivery to primary and metastatic tumor sites.

New insights on adenovirus as vaccine vectors

Adenovirus (Ad) vectors were initially developed for treatment of genetic diseases. Their usefulness for permanent gene replacement was limited by their high immunogenicity, which resulted in rapid elimination of transduced cells through induction of T and B cells to antigens of Ad and the transgene product. The very trait that excluded their use for sustained treatment of genetic diseases made them highly attractive as vaccine carriers. Recently though results showed that Ad vectors based on common human serotypes, such as serotype 5, may not be ideal as vaccine carriers. A recently conducted phase 2b trial, termed STEP trial, with an AdHu5-based vaccine expressing antigens of human immunodeficiency virus 1 (HIV-1) not only showed lack of efficacy in spite of the vaccine's immunogenicity, but also suggested an increased trend for HIV acquisition in individuals that had circulating AdHu5 neutralizing antibodies prior to vaccination. Alternative serotypes from humans or nonhuman primates (NHPs), to which most humans lack pre-existing immunity, have been vectored and may circumvent the problems encountered with the use of AdHu5 vectors in humans. In summary, although Ad vectors have seen their share of setbacks in recent years, they remain viable tools for prevention or treatment of a multitude of diseases.

Armed replicating adenoviruses for cancer virotherapy

Conditionally replicating adenoviruses (CRAds) have many advantages as agents for cancer virotherapy and have been safely used in human clinical trials. However, replicating adenoviruses have been limited in their ability to eliminate tumors by oncolysis. Thus, the efficacy of these agents must be improved. To this end, CRAds have been engineered to express therapeutic transgenes that exert antitumor effects independent of direct viral oncolysis. These transgenes can be expressed under native gene control elements, in which case placement within the genome determines the expression profile, or they can be controlled by exogenous promoters. The therapeutic transgenes used to arm replicating adenoviruses can be broadly classified into three groups. There are those that mediate killing of the infected cell, those that modulate the tumor microenvironment and those with immunomodulatory functions. Overall, the studies to date in animal models have shown that arming a CRAd with a rationally chosen therapeutic transgene can improve its antitumor efficacy over that of an unarmed CRAd. However, a number of obstacles must be overcome before the full potential of armed CRAds can be realized in the human clinical context. Hence, strategies are being developed to permit intravenous delivery to disseminated cancer cells, overcome the immune response and enable in vivo monitoring of the biodistribution and activity of armed CRAds.