Replication-selective adenoviruses as oncolytic agents

Oncolytic virus Ad-TD-nsIL-12 inhibits glioma growth and reprograms the tumor immune microenvironment

AIMS

Gliomas are the most common central nervous system malignancies, with limited therapeutic options and poor prognosis, which are primarily attributed to the "immune desert" microenvironment. Previously, we constructed a three-gene-deleted oncolytic adenovirus (Ad-TD) loaded with non-secreting interleukin-12 (nsIL-12), which could be amplified in tumor cells and induce immunity to suppress tumors. However, the effects of this oncolytic virus on gliomas and their immune microenvironment remain unclear. There is an urgent need for further research.

MATERIALS AND METHODS

We constructed a Syrian hamster brain tumor model and demonstrated the efficacy and mechanism of the novel oncolytic virus in treating brain tumors through a series of in vitro and in vivo experiments. We investigated the efficacy and safety (the number of hamsters in each group is either 5 or 10) of the oncolytic virus treatment in Syrian hamsters using a virus-treated group, a control virus-treated group, and a blank control group.

KEY FINDINGS

In vitro assays showed that Ad-TD-nsIL-12 could specifically proliferate in brain tumor cells which induce tumor cell apoptosis and intracellular expression of interleukin (IL)-12. Moreover, in vivo experiments demonstrated that Ad-TD-nsIL-12 could effectively inhibit the progression of brain tumors and prolong survival. Ad-TD-nsIL-12 significantly enhanced T-cell infiltration in the brain tumor microenvironment.

SIGNIFICANCE

Ad-TD-nsIL-12 can inhibit glioma progression and increase T-cell infiltration in the tumor tissue, particularly infiltration by cytotoxic T cells (CD8+). Ad-TD-nsIL-12 can amplify and produce IL-12, inducing anti-glioma immune responses to inhibit tumor progression.

Clinical Trials of Oncolytic Viruses in Breast Cancer

Breast cancer is the second most common kind of cancer worldwide and oncolytic viruses may offer a new treatment approach. There are three different types of oncolytic viruses used in clinical trials; (i) oncolytic viruses with natural anti-neoplastic properties; (ii) oncolytic viruses designed for tumor-selective replication; (iii) oncolytic viruses modified to activate the immune system. Currently, fourteen different oncolytic viruses have been investigated in eighteen published clinical trials. These trials demonstrate that oncolytic viruses are well tolerated and safe for use in patients and display clinical activity. However, these trials mainly studied a small number of patients with different advanced tumors including some with breast cancer. Future trials should focus on breast cancer and investigate optimal routes of administration, occurrence of neutralizing antibodies, viral gene expression, combinations with other antineoplastic therapies, and identify subtypes that are particularly suitable for oncolytic virotherapy.

Insights into the Mechanisms of Action of MDA-7/IL-24: A Ubiquitous Cancer-Suppressing Protein

Melanoma differentiation associated gene-7/interleukin-24 (MDA-7/IL-24), a secreted protein of the IL-10 family, was first identified more than two decades ago as a novel gene differentially expressed in terminally differentiating human metastatic melanoma cells. MDA-7/IL-24 functions as a potent tumor suppressor exerting a diverse array of functions including the inhibition of tumor growth, invasion, angiogenesis, and metastasis, and induction of potent "bystander" antitumor activity and synergy with conventional cancer therapeutics. MDA-7/IL-24 induces cancer-specific cell death through apoptosis or toxic autophagy, which was initially established in vitro and in preclinical animal models in vivo and later in a Phase I clinical trial in patients with advanced cancers. This review summarizes the history and our current understanding of the molecular/biological mechanisms of MDA-7/IL-24 action rendering it a potent cancer suppressor.

Oncolytic Adenoviruses for Cancer Therapy

Many immuno-therapeutic strategies are currently being developed to fight cancer. In this scenario, oncolytic adenoviruses (Onc.Ads) have an interesting role for their peculiar tumor selectivity, safety, and transgene-delivery capability. The major strength of the Onc.Ads is the extraordinary immunogenicity that leads to a strong T-cell response, which, together with the possibility of the delivery of a therapeutic transgene, could be more effective than current strategies. In this review, we travel in the adenovirus (Ads) and Onc.Ads world, focusing on a variety of strategies that can enhance Onc.Ads antitumoral efficacy, passing through tumor microenvironment modulation. Onc.Ads-based therapeutic strategies constitute additional weapons in the fight against cancer and appear to potentiate conventional and immune checkpoint inhibitors (ICIs)-based therapies leading to a promising scenario.

Identification of oncolytic vaccinia restriction factors in canine high-grade mammary tumor cells using single-cell transcriptomics

Mammary carcinoma, including triple-negative breast carcinomas (TNBC) are tumor-types for which human and canine pathologies are closely related at the molecular level. The efficacy of an oncolytic vaccinia virus (VV) was compared in low-passage primary carcinoma cells from TNBC versus non-TNBC. Non-TNBC cells were 28 fold more sensitive to VV than TNBC cells in which VV replication is impaired. Single-cell RNA-seq performed on two different TNBC cell samples, infected or not with VV, highlighted three distinct populations: naïve cells, bystander cells, defined as cells exposed to the virus but not infected and infected cells. The transcriptomes of these three populations showed striking variations in the modulation of pathways regulated by cytokines and growth factors. We hypothesized that the pool of genes expressed in the bystander populations was enriched in antiviral genes. Bioinformatic analysis suggested that the reduced activity of the virus was associated with a higher mesenchymal status of the cells. In addition, we demonstrated experimentally that high expression of one gene, DDIT4, is detrimental to VV production. Considering that DDIT4 is associated with a poor prognosis in various cancers including TNBC, our data highlight DDIT4 as a candidate resistance marker for oncolytic poxvirus therapy. This information could be used to design new generations of oncolytic poxviruses. Beyond the field of gene therapy, this study demonstrates that single-cell transcriptomics can be used to identify cellular factors influencing viral replication.

The identification of cellular genes influencing viral replication/propagation has been studied using hypothesis-driven approaches and/or high-throughput RNA interference screens. In the present report, we propose a methodology based on single-cell transcriptomics. We have studied, in the context of oncolytic virotherapy, the susceptibility of different grades of primary low-passage mammary carcinoma cells of canine origin to an oncolytic vaccinia virus (VV). We highlight a fault in replication of VV in cells that originated from high-grade triple-negative breast carcinomas (TNBC). Single-cell RNA-seq performed on TNBC cell samples infected with VV suggested that the reduced activity of the virus was associated with a higher mesenchymal status of the cells. We also demonstrate that high expression of one gene, DDIT4, is detrimental to VV production. Considering that DDIT4 is associated with a poor prognosis in various cancers including TNBC, our data highlight DDIT4 as a candidate resistance marker for oncolytic poxvirus therapy. Beyond the field of cancer gene therapy, we demonstrate here that single-cell transcriptomics increases the arsenal of tools available to identify cellular factors influencing viral replication.

Oncolytic effect of Midkine promoter-based conditionally replicating adenoviruses expressing EGFR siRNA in head and neck squamous cancer cell line T891

Background

Epidermal growth factor receptor (EGFR) is overexpressed in head and neck squamous cell carcinomas (HNSCCs). Midkine expression is restricted in adult tissues but is increased in several malignant tumors, including HNSCCs.

Aim

Here, we evaluated the antitumor effect of Midkine promoter–based conditionally replicative adenovirus expressing siRNA against EGFR for targeting HNSCCs expressing Midkine.

Methods and results

A conditionally replicative adenovirus vector controlled by the Midkine promoter, Ad‐MK‐siEGFR, was generated by integrating gene‐expressing siRNA against EGFR. Antitumor effect of Ad‐MK‐siEGFR was tested in vitro using established HNSCC cell line, T891 with strong Midkine expression. Expression of EGFR in T891 infected with Ad‐MK‐siEGFR was significantly lower than that of T891 infected with control. Cytotoxicity assays showed significant growth suppression of Ad‐MK‐siEGFR in T891 cells.

Conclusions

This study demonstrated the possibility of oncolytic therapy using the Midkine promoter–based conditional replication‐selective adenovirus containing siRNA against EGFR in HNSCC cell line T891. Further validation of the findings in more cell lines and in vivo should be performed to clarify the potential clinical application.

Adenoviral Vectors Armed with PAPILLOMAVIRUs Oncogene Specific CRISPR/Cas9 Kill Human-Papillomavirus-Induced Cervical Cancer Cells

Human papillomaviruses (HPV) cause malignant epithelial cancers including cervical carcinoma, non-melanoma skin and head and neck cancer. They drive tumor development through the expression of their oncoproteins E6 and E7. Designer nucleases were shown to be efficient to specifically destroy HPV16 and HPV18 oncogenes to induce cell cycle arrest and apoptosis. Here, we used high-capacity adenoviral vectors (HCAdVs) expressing the complete CRISPR/Cas9 machinery specific for HPV18-E6 or HPV16-E6. Cervical cancer cell lines SiHa and CaSki containing HPV16 and HeLa cells containing HPV18 genomes integrated into the cellular genome, as well as HPV-negative cancer cells were transduced with HPV-type-specific CRISPR-HCAdV. Upon adenoviral delivery, the expression of HPV-type-specific CRISPR/Cas9 resulted in decreased cell viability of HPV-positive cervical cancer cell lines, whereas HPV-negative cells were unaffected. Transduced cervical cancer cells showed increased apoptosis induction and decreased proliferation compared to untreated or HPV negative control cells. This suggests that HCAdV can serve as HPV-specific cancer gene therapeutic agents when armed with HPV-type-specific CRISPR/Cas9. Based on the versatility of the CRISPR/Cas9 system, we anticipate that our approach can contribute to personalized treatment options specific for the respective HPV type present in each individual tumor.

Oncolytic adenoviruses: a game changer approach in the battle between cancer and the immune system

INTRODUCTION

Oncolytic adenoviruses are among the most studied oncolytic viruses because of their tumor selectivity, safety, and transgene-delivery capability. With a growing number of different immunotherapies against cancer, the extraordinary immunogenicity of the adenovirus has emerged as a differentiating strength. Enabling T-cell related therapies with oncolytic adenoviruses appears a promising approach due to its inherent ability to elicit responses from the adaptive immune compartment.

AREAS COVERED

These viruses have successfully enhanced both adoptive T-cell therapies and immune-checkpoint therapies. Oncolytic viruses induce several effects at the tumor and on the systemic level that help to circumvent current limitations of T-cells and related therapies, such as T-cell trafficking, tumor immune suppressivity and antigen spreading

EXPERT OPINION

Taking into account the multitude of possibilities of treating cancer with immunotherapies, learning to optimize the combinations and administration strategies of these drugs, could lead to durable responses in patients with currently incurable cancers.

Physically crosslinked injectable hydrogels for long-term delivery of oncolytic adenoviruses for cancer treatment

A dual pH- and temperature-responsive physically crosslinked and injectable hydrogel system was developed for efficient and long-term delivery of oncolytic adenoviruses (Ads).

Cancer terminator viruses (CTV): A better solution for viral-based therapy of cancer

In principle, viral gene therapy holds significant potential for the therapy of solid cancers. However, this promise has not been fully realized and systemic administration of viruses has not proven as successful as envisioned in the clinical arena. Our research is focused on developing the next generation of efficacious viruses to specifically treat both primary cancers and a major cause of cancer lethality, metastatic tumors (that have spread from a primary site of origin to other areas in the body and are responsible for an estimated 90% of cancer deaths). We have generated a chimeric tropism-modified type 5 and 3 adenovirus that selectively replicates in cancer cells and simultaneously produces a secreted anti-cancer toxic cytokine, melanoma differentiation associated gene-7/Interleukin-24 (mda-7/IL-24), referred to as a Cancer Terminator Virus (CTV) (Ad.5/3-CTV). In preclinical animal models, injection into a primary tumor causes selective cell death and therapeutic activity is also observed in non-injected distant tumors, that is, "bystander anti-tumor activity." To enhance the impact and therapeutic utility of the CTV, we have pioneered an elegant approach in which viruses are encapsulated in microbubbles allowing "stealth delivery" to tumor cells that when treated with focused ultrasound causes viral release killing tumor cells through viral replication, and producing and secreting MDA-7/IL-24, which stimulates the immune system to attack distant cancers, inhibits tumor angiogenesis and directly promotes apoptosis in distant cancer cells. This strategy is called UTMD (ultrasound-targeted microbubble-destruction). This novel CTV and UTMD approach hold significant promise for the effective therapy of primary and disseminated tumors.

Re-designing Interleukin-12 to enhance its safety and potential as an anti-tumor immunotherapeutic agent. Nat Commun. 2017;8:1395. [PMID: 29123084 PMCID: PMC5680234 DOI: 10.1038/s41467-017-01385-8]

Interleukin-12 (IL-12) has emerged as one of the most potent agents for anti-tumor immunotherapy. However, potentially lethal toxicity associated with systemic administration of IL-12 precludes its clinical application. Here we redesign the molecule in such a way that its anti-tumor efficacy is not compromised, but toxic effects are eliminated. Deletion of the N-terminal signal peptide of IL-12 can effect such a change by preventing IL-12 secretion from cells. We use a newly designed tumor-targeted oncolytic adenovirus (Ad-TD) to deliver non-secreting (ns) IL-12 to tumor cells and examine the therapeutic and toxic effects in Syrian hamster models of pancreatic cancer (PaCa). Strikingly, intraperitoneal delivery of Ad-TD-nsIL-12 significantly enhanced survival of animals with orthotopic PaCa and cured peritoneally disseminated PaCa with no toxic side effects, in contrast to the treatment with Ad-TD expressing unmodified IL-12. These findings offer renewed hope for development of IL-12-based treatments for cancer.

Interleukin-12 (IL-12) is a potent immunotherapeutic agent.

Mesenchymal stromal cells for the delivery of oncolytic viruses in gliomas

Mesenchymal stromal cells (MSCs) are a type of adult stem cell that has been exploited for the treatment of a variety of diseases, including cancer. In particular, MSCs have been studied extensively for their ability to treat glioblastoma (GBM), the most common and deadly form of brain cancer in adults. MSCs are attractive therapeutics because they can be obtained relatively easily from patients, are capable of being expanded numerically in vitro, can be easily engineered and are inherently capable of homing to tumors, making them ideal vehicles for delivering biological antitumoral agents. Oncolytic viruses are promising biological therapeutic agents that have been used in the treatment of GBMs, and MSCs are currently being explored as a means of delivering these viruses. Here we review the role of MSCs in the treatment of GBMs, focusing on the intersection of MSCs and oncolytic viruses.

Adenoviral Vectors Armed with Cell Fusion-Inducing Proteins as Anti-Cancer Agents

Cancer is a devastating disease that affects millions of patients every year, and causes an enormous economic burden on the health care system and emotional burden on affected families. The first line of defense against solid tumors is usually extraction of the tumor, when possible, by surgical methods. In cases where solid tumors can not be safely removed, chemotherapy is often the first line of treatment. As metastatic cancers often become vigorously resistant to treatments, the development of novel, more potent and selective anti-cancer strategies is of great importance. Adenovirus (Ad) is the most commonly used virus in cancer clinical trials, however, regardless of the nature of the Ad-based therapeutic, complete responses to treatment remain rare. A number of pre-clinical studies have shown that, for all vector systems, viral spread throughout the tumor mass can be a major limiting factor for complete tumor elimination. By expressing exogenous cell-fusion proteins, many groups have shown improved spread of Ad-based vectors. This review summarizes the research done to examine the potency of Ad vectors expressing fusogenic proteins as anti-cancer therapeutics.

Oncolytic viruses: From bench to bedside with a focus on safety

Oncolytic viruses are a relatively new class of anti-cancer immunotherapy agents. Several viruses have undergone evaluation in clinical trials in the last decades, and the first agent is about to be approved to be used as a novel cancer therapy modality. In the current review, an overview is presented on recent (pre)clinical developments in the field of oncolytic viruses that have previously been or currently are being evaluated in clinical trials. Special attention is given to possible safety issues like toxicity, environmental shedding, mutation and reversion to wildtype virus.

Activation of Cyclic Adenosine Monophosphate Pathway Increases the Sensitivity of Cancer Cells to the Oncolytic Virus M1

Oncolytic virotherapy is a novel and emerging treatment modality that uses replication-competent viruses to destroy cancer cells. Although diverse cancer cell types are sensitive to oncolytic viruses, one of the major challenges of oncolytic virotherapy is that the sensitivity to oncolysis ranges among different cancer cell types. Furthermore, the underlying mechanism of action is not fully understood. Here, we report that activation of cyclic adenosine monophosphate (cAMP) signaling significantly sensitizes refractory cancer cells to alphavirus M1 in vitro, in vivo, and ex vivo. We find that activation of the cAMP signaling pathway inhibits M1-induced expression of antiviral factors in refractory cancer cells, leading to prolonged and severe endoplasmic reticulum (ER) stress, and cell apoptosis. We also demonstrate that M1-mediated oncolysis, which is enhanced by cAMP signaling, involves the factor, exchange protein directly activated by cAMP 1 (Epac1), but not the classical cAMP-dependent protein kinase A (PKA). Taken together, cAMP/Epac1 signaling pathway activation inhibits antiviral factors and improves responsiveness of refractory cancer cells to M1-mediated virotherapy.

Conditionally replicating oncolytic adenoviral vector expressing arresten and tumor necrosis factor-related apoptosis-inducing ligand experimentally suppresses lung carcinoma progression

Current methods of treatment for lung carcinoma are ineffective for the majority of patients. Conditionally replicating adenoviruses (CRAds) represent a potential novel treatment for a number of neoplastic diseases, including lung carcinoma. The present study aimed to investigate the synergistic mechanisms underlying the anti-angiogenesis gene, arresten, and the apoptosis-inducing gene, tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), in order to evaluate their therapeutic potential in lung cancer. The two genes were expressed by CRAd, which was confirmed using reverse transcription-polymerase chain reaction and western blotting. In vitro analyses demonstrated that CRAd adenoviruses are capable of selectively inhibiting A549 lung cancer cell growth and replication but not in that of healthy cells. In vivo analyses demonstrated that the infection of A549 cell lines using CRAd armed with the two genes (CRAd-arresten-TRAIL) enhanced the tumor inhibition, compared with cells infected with CRAd-arresten, CRAd-TRAIL or CRAd, and with the control group. CRAd-arresten-TRAIL may therefore be useful in the treatment of lung cancer.

pH-sensitive oncolytic adenovirus hybrid targeting acidic tumor microenvironment and angiogenesis

Although oncolytic adenoviruses (Ads) are an attractive option for cancer gene therapy, the intravenous administration of naked Ad still encounters unfavorable host responses, non-specific interactions, and heterogeneity in targeted cancer cells. To overcome these obstacles and achieve specific targeting of the tumor microenvironment, Ad was coated with the pH-sensitive block copolymer, methoxy poly(ethylene glycol)-b-poly(l-histidine-co-l-phenylalanine) (PEGbPHF). The physicochemical properties of the generated nanocomplex, Ad/PEGbPHF, were assessed. At pH6.4, GFP-expressing Ad/PEGbPHF induced significantly higher GFP expression than naked Ad in both coxsackie and adenovirus receptor (CAR)-positive and -negative cells. To assess the therapeutic efficacy of the Ad/PEGbPHF complex platform, an oncolytic Ad expressing VEGF promoter-targeting transcriptional repressor (KOX) was used to form complexes. At pH6.4, KOX/PEGbPHF significantly suppressed VEGF gene expression, cancer cell migration, vessel sprouting, and cancer cell killing effect compared to naked KOX or KOX/PEGbPHF at pH7.4, demonstrating that KOX/PEGbPHF can overcome the lack of CAR that is frequently observed in tumor tissues. The antitumor activity of KOX/PEGbPHF systemically administered to a tumor xenograft model was significantly higher than that of naked KOX. Furthermore, KOX/PEGbPHF showed lower hepatic toxicity and did not induce an innate immune response against Ad. Altogether, these results demonstrate that pH-sensitive polymer-coated Ad complex significantly increases net positive charge upon exposure to hypoxic tumor microenvironment, allowing passive targeting to the tumor tissue. It may offer superior potential for systemic therapy, due to its improved tumor selectivity, increased therapeutic efficacy, and lower toxicity compared to naked KOX.

Combination of bladder cancer-specific oncolytic adenovirus gene therapy with cisplatin on bladder cancer in vitro

Bladder cancer-specific oncolytic adenovirus Ad/PSCAE/UPII/E1A, carrying E1A gene regulated by human Uroplakin II (UPII) promoter and prostate stem cell antigen enhancer (PSCAE), could kill bladder tumor cells preferentially. The aim of this study was to examine the effects of Ad/PSCAE/UPII/E1A combined with cisplatin on human bladder cancer cells and to identify the underlying mechanisms. The combined effects of Ad/PSCAE/UPII/E1A and cisplatin on EJ, 5637, and BIU-87 bladder cancer cells were evaluated by MTT cell proliferation assay. Cell apoptosis was detected by flow cytometry with fluorescein isothiocyanate-conjugated annexin V (annexin V-FITC) and propidium iodide staining. The activation of the caspase pathway and the expression of Bcl-2 family proteins were determined by western blot assay. Ad/PSCAE/UPII/E1A adenovirus vector could infect bladder cancer cell lines selectively and induce growth inhibition effectively. Of note, the combination treatment of cisplatin and Ad/PSCAE/UPII/E1A could inhibit the proliferation of bladder cancer cells significantly compared with the "alone" treatment. Furthermore, Ad/PSCAE/UPII/E1A plus cisplatin combined treatment resulted in enhanced apoptosis in bladder cancer cells. The enhanced antitumor effects in vitro elicited by Ad/PSCAE/UPII/E1A plus cisplatin were closely related to the increased Fas expression and cleavage of caspase-8 and Bid and decrease in the ratio of anti- to pro-apoptotic proteins followed by activation of caspase-9 and caspase-3, which may contribute to the activation of extrinsic and intrinsic apoptotic pathways. Our results indicate that the combination of Ad/PSCAE/UPII/E1A with cisplatin exerts a synergistic antitumor effect on human bladder cancer cells and is a potential combined treatment strategy for bladder cancer.

Experimental studies on treatment of pancreatic cancer with double-regulated duplicative adenovirus AdTPHre-hEndo carrying human endostatin gene

BACKGROUND

Gene-virus targeted therapy is a promising new method of treating pancreatic cancer. To increase the efficacy and decrease the side-effect, we constructed a conditionally replicative adenovirus (CRAd) expressing human endostatin, with a human Telomoerase Reverse Transcriptase (hTERT) promoter for the regulation of the early stage of adenovirus expression of gene E1a and a Hypoxia Response Element (HRE) promoter to regulate the gene E1b.

METHODS

A gene recombination technique was adopted to construct and generate the adenovirus AdTPHre-hEndo. Pancreatic cancer cells were studied both in vitro and in vivo. Western blotting was adopted to observe the expressions of protein E1A and E1B; duplication assay was applied to observe the selective duplication capability of recombinant cells. MTT assay was applied to measure the lethal effects of virus on pancreatic cancer cells, and ELISA was adopted to detect the human endostatin gene expression. A pancreatic cancer transplantation tumor model of nude mice was constructed to observe the antitumor effects of the virus.

RESULTS

Double-regulated duplicative adenovirus AdTPHre-hEndo genes were successfully constructed. Duplication and lethal assays proved that AdTPHre-hEndo could replicate specifically in pancreatic cancer cells and kill them. The endostatin expression in a cultured supernatant from tumor cells was significantly higher than that obtained from non-duplicative adenovirus vectors carrying that gene. The animal experiment demonstrated that AdTPHre-hEndo has a high capability to limit pancreatic cancer growth.

CONCLUSIONS

AdTPHre-hEndo has a special ability to duplicate and kill pancreatic cancer cells in in vitro and in vivo experiments, thus providing a new gene-virus-based treatment system for pancreatic cancer.

Current status of local therapy in malignant gliomas--a clinical review of three selected approaches

Malignant gliomas are the most frequently occurring, devastating primary brain tumors, and are coupled with a poor survival rate. Despite the fact that complete neurosurgical resection of these tumors is impossible in consideration of their infiltrating nature, surgical resection followed by adjuvant therapeutics, including radiation therapy and chemotherapy, is still the current standard therapy. Systemic chemotherapy is restricted by the blood-brain barrier, while methods of local delivery, such as with drug-impregnated wafers, convection-enhanced drug delivery, or direct perilesional injections, present attractive ways to circumvent these barriers. These methods are promising ways for direct delivery of either standard chemotherapeutic or new anti-cancer agents. Several clinical trials showed controversial results relating to the influence of a local delivery of chemotherapy on the survival of patients with both recurrent and newly diagnosed malignant gliomas. Our article will review the development of the drug-impregnated release, as well as convection-enhanced delivery and the direct injection into brain tissue, which has been used predominantly in gene-therapy trials. Further, it will focus on the use of convection-enhanced delivery in the treatment of patients with malignant gliomas, placing special emphasis on potential shortcomings in past clinical trials. Although there is a strong need for new or additional therapeutic strategies in the treatment of malignant gliomas, and although local delivery of chemotherapy in those tumors might be a powerful tool, local therapy is used only sporadically nowadays. Thus, we have to learn from our mistakes in the past and we strongly encourage future developments in this field.

Local sustained delivery of oncolytic adenovirus with injectable alginate gel for cancer virotherapy

Adenoviruses (Ad) have been investigated for their efficacy in reducing primary tumors after local intratumoral administration. Despite high Ad concentrations and repetitive administration, the therapeutic efficacy of Ad has been limited because of rapid dissemination of the Ad into the surrounding normal tissues and short maintenance of Ad biological activity in vivo. To maximize the therapeutic potential of Ad-mediated gene therapeutics, we investigated the efficacy of local, sustained Ad delivery, using an injectable alginate gel matrix system. The biological activity of Ad loaded in alginate gel was prolonged compared with naked Ad, as evidenced by the high green fluorescent protein gene transduction efficiency over an extended time period. Moreover, oncolytic Ad encapsulated in alginate gel elicited 1.9- to 2.4-fold greater antitumor activity than naked Ad in both C33A and U343 human tumor xenograft models. Histological and quantitative PCR analysis confirmed that the oncolytic Ad/alginate gel matrix system significantly increased preferential replication and dissemination of oncolytic Ad in a larger area of tumor tissue in vivo. Taken together, these results show that local sustained delivery of oncolytic Ad in alginate gel augments therapeutic effect through selective infection of tumor cells, sustained release and prolonged maintenance of Ad activity.

Chapter One---Cancer terminator viruses and approaches for enhancing therapeutic outcomes

No single or combinatorial therapeutic approach has proven effective in decreasing morbidity or engendering a cure of metastatic cancer. In principle, conditionally replication-competent adenoviruses that induce tumor oncolysis through cancer-specific replication hold promise for cancer therapy. However, a single-agent approach may not be adequate to completely eradicate cancer in a patient because most cancers arise from abnormalities in multiple genetic and signal transduction pathways and targeting disseminated metastases is difficult to achieve. Based on these considerations, a novel class of cancer destroying adenoviruses have been produced, cancer terminator viruses (CTVs), in which cancer-specific replication is controlled by the progression-elevated gene-3 promoter and replicating viruses produce a second transgene encoding an apoptosis-inducing and immunomodulatory cytokine, either melanoma differentiation-associated gene-7/interleukin-24 (mda-7/IL-24) or interferon-γ. This review focuses on these viruses and ways to improve their delivery systemically and enhance their therapeutic efficacy.

Randomized dose-finding clinical trial of oncolytic immunotherapeutic vaccinia JX-594 in liver cancer

Oncolytic viruses and active immunotherapeutics have complementary mechanisms of action (MOA) that are both self amplifying in tumors, yet the impact of dose on subject outcome is unclear. JX-594 (Pexa-Vec) is an oncolytic and immunotherapeutic vaccinia virus. To determine the optimal JX-594 dose in subjects with advanced hepatocellular carcinoma (HCC), we conducted a randomized phase 2 dose-finding trial (n=30). Radiologists infused low- or high-dose JX-594 into liver tumors (days 1, 15 and 29); infusions resulted in acute detectable intravascular JX-594 genomes. Objective intrahepatic Modified Response Evaluation Criteria in Solid Tumors (mRECIST) (15%) and Choi (62%) response rates and intrahepatic disease control (50%) were equivalent in injected and distant noninjected tumors at both doses. JX-594 replication and granulocyte-macrophage colony-stimulating factor (GM-CSF) expression preceded the induction of anticancer immunity. In contrast to tumor response rate and immune endpoints, subject survival duration was significantly related to dose (median survival of 14.1 months compared to 6.7 months on the high and low dose, respectively; hazard ratio 0.39; P=0.020). JX-594 demonstrated oncolytic and immunotherapy MOA, tumor responses and dose-related survival in individuals with HCC.

Fiber-substituted conditionally replicating adenovirus Ad5F35 induces oncolysis of human bladder cancer cells in in vitro analysis

OBJECTIVE

To assess the oncolytic effect of fiber-substituted conditionally replicating adenovirus type 5 (Ad5) F35 vector on human bladder cancer cell lines such as 253J, 5637, KK-47, T24, TCCSUP, and UMUC-3 cells.

MATERIALS AND METHODS

Ad5F35 and Ad5 conditionally replicating adenovirus vectors containing the E1 gene controlled by the human midkine promoter (Ad5F35/MKp-E1 and Ad5/MKp-E1, respectively) were constructed. Reverse transcriptase-polymerase chain reaction and cell viability assay were performed in cells transfected with Ad5F35/MKp-E1 or Ad5/MKp-E1.

RESULTS

Of the bladder cancer cells used, considerably lower expression of mRNA for Coxsackie and adenovirus receptor, an Ad5 receptor, was found with T24 and TCCSUP cells. However, the mRNA for CD46, an Ad35 receptor, was abundantly expressed in all the cell types. Ad5F35/MKp-E1 induced oncolysis in a plaque formation unit-dependent manner for all the bladder cancer cells used, with greater efficacy than Ad5/MKp-E1 for T24, TCCSUP, and 253J cells.

CONCLUSION

The results of the present study have shown that Ad5F35/MKp-E1 is more useful for the gene therapy of bladder cancer than Ad5/MKp-E1 is for some cell lines.

MicroRNA-mediated suppression of oncolytic adenovirus replication in human liver

MicroRNAs (miRNAs) are important and ubiquitous regulators of gene expression that can suppress their target genes by translational inhibition as well as mRNA destruction. Cell type-specific miRNA expression patterns have been successfully exploited for targeting the expression of experimental and therapeutic gene constructs, for example to reduce pathogenic effects of cancer virotherapy in normal tissues. In order to avoid liver damage associated with systemic or intrahepatic delivery of oncolytic adenoviruses we have introduced the concept of suppressing adenovirus replication in hepatic cells by inserting target elements for the liver-specific miR122 into the viral genome. Here we show using ex vivo cultured tissue specimens that six perfectly complementary miR122 target sites in the 3′ untranslated region of the viral E1A gene are sufficient in the absence of any other genetic modifications to prevent productive replication of serotype 5 adenovirus (Ad5) in normal human liver. This modification did not compromise the replicative capacity of the modified virus in cancer tissue derived from a colon carcinoma liver metastasis or its oncolytic potency in a human lung cancer xenograft mouse model. Unlike wild-type Ad5, the modified virus did not result in increased serum levels of liver enzymes in infected mice. These results provide a strong preclinical proof of concept for the use of miR122 target sites for reducing the risk of liver damage caused by oncolytic adenoviruses, and suggest that ectopic miR122 target elements should be considered as an additional safety measure included in any therapeutic virus or viral vector posing potential hazard to the liver.

A novel CRAd in combination with cisplatin enhanced the antitumor efficacy in ovarian cancer

OBJECTIVES

The aim of this study was to investigate the combined effects of a novel survivin promoter-based conditionally replicating adenovirus (CRAd-S.RGD) plus cis-diamminedichloroplatinum (cisplatin, CDDP) in ovarian cancer in vitro and in vivo.

METHODS

The viability of human ovarian cancer cell line SKOV3 was determined by MTT assay following the infection with different doses of CRAd-S.RGD, either alone or in combination with CDDP. The antitumor efficacies and survival curves were evaluated at the end of the treatment regimens with the subcutaneous administration of CRAd-S.RGD, CDDP, combined therapy of CRAd-S.RGD plus CDDP, or phosphate-buffered saline in a SKOV3 xenograft animal model. Furthermore, the apoptosis rate of tumor tissues in mice was determined subsequent to the treatments.

RESULTS

In vitro, the CRAd-S.RGD destroyed SKOV3 cells by oncolysis in a dose-dependent manner, and the viability of SKOV3 cells was significantly lower in the combined-therapy group than that in the individual-therapy groups. In vivo, enhanced tumor inhibition and animal survival rates were obtained in a synergistic manner with CRAd-S.RGD plus CDDP, as compared with the treatment with CRAd-S.RGD or CDDP alone. There was an increase in the apoptosis rate of the cells following the combined therapy. The results clearly demonstrated that there was a synergistic effect in the combination of CRAd-S.RGD and CDDP in increased therapeutic efficacy. Similar therapeutic efficacy could be obtained with CRAd-S.RGD plus CDDP at 2 lower doses that minimized the drug toxicity to host tissues.

CONCLUSIONS

The strategy of CRAd-S.RGD in combination with CDDP was a potential therapeutic modality for the therapy in ovarian cancer.

ABBREVIATIONS

CDDP - cisplatin, cis-diamminedichloroplatinum, CRAd - conditionally replicating adenovirus, CRAd-survivin - the survivin promoter-based conditionally replicating adenovirus, CRAd-S.RGD - CRAd-survivin-RGD4C, MOI - multiplicity of infection, PBS - phosphate-buffered saline, PI - propidium iodide.

Therapeutic efficacy of an oncolytic adenovirus containing RGD ligand in minor capsid protein IX and Fiber, Δ24DoubleRGD, in an ovarian cancer model

Ovarian cancer is the leading cause of gynecological disease death despite advances in medicine. Therefore, novel strategies are required for ovarian cancer therapy. Conditionally replicative adenoviruses (CRAds), genetically modified as anti-cancer therapeutics, are one of the most attractive candidate agents for cancer therapy. However, a paucity of coxsackie B virus and adenovirus receptor (CAR) expression on the surface of ovarian cancer cells has impeded treatment of ovarian cancer using this approach. This study sought to engineer a CRAd with enhanced oncolytic ability in ovarian cancer cells, "Δ24DoubleRGD." Δ24DoubleRGD carries an arginine-glycine-aspartate (RGD) motif incorporated into both fiber and capsid protein IX (pIX) and its oncolytic efficacy was evaluated in ovarian cancer. In vitro analysis of cell viability showed that infection of ovarian cancer cells with Δ24DoubleRGD leads to increased cell killing relative to the control CRAds. Data from this study suggested that not only an increase in number of RGD motifs on the CRAd capsid, but also a change in the repertoir of targeted integrins could lead to enhanced oncolytic potency of Δ24DoubleRGD in ovarian cancer cells in vitro. In an intraperitoneal model of ovarian cancer, mice injected with Δ24DoubleRGD showed, however, a similar survival rate as mice treated with control CRAds.

Effects of nanoparticle coatings on the activity of oncolytic adenovirus-magnetic nanoparticle complexes

Limitations to adenovirus infectivity can be overcome by association with magnetic nanoparticles and enforced infection by magnetic field influence. Here we examined three core-shell-type iron oxide magnetic nanoparticles differing in their surface coatings, particle sizes and magnetic properties for their ability to enhance the oncolytic potency of adenovirus Ad520 and to stabilize it against the inhibitory effects of serum or a neutralizing antibody. It was found that the physicochemical properties of magnetic nanoparticles are critical determinants of the properties which govern the oncolytic productivities of their complexes with Ad520. Although high serum concentration during infection or a neutralizing antibody had strong inhibitory influence on the uptake or oncolytic productivity of the naked virus, one particle type was identified which conferred high protection against both inhibitory factors while enhancing the oncolytic productivity of the internalized virus. This particle type equipped with a silica coating and adsorbed polyethylenimine, displaying a high magnetic moment and high saturation magnetization, mediated a 50% reduction of tumor growth rate versus control upon intratumoral injection of its complex with Ad520 and magnetic field influence, whereas Ad520 alone was inefficient. The correlations between physical properties of the magnetic particles or virus complexes and oncolytic potency are described herein.

Clinical development of experimental therapies for malignant glioma

Advances in medical and surgical treatments in the last two to three decades have resulted in quantum leaps in the overall survival of patients with many types of non-central nervous system (CNS) malignant disease, while survival of patients with malignant gliomas (WHO grades 3 and 4) has only moderately improved. Surgical resection, external fractionated radiotherapy and oral chemotherapy, during and after irradiation, remain the pillars of malignant glioma therapy and have shown significant benefits. However, numerous clinical trials with adjuvant agents, most of them administered systemically and causing serious complications and side effects, have not achieved a noteworthy extension of survival, or only with considerable deterioration in patients' quality of life. Significant attention was focussed in the last decades on the cell biology and molecular genetics of gliomas. Improved understanding of the fundamental features of tumour cells has resulted in the introduction and increasing clinical use of local therapies, which employ spatially defined delivery methods and tumour-selective agents specifically designed to be used in the environment of a glioma-invaded brain. This review summarises the key findings of some of the most recent and important clinical studies of locally administered novel treatments for malignant glioma. Several such therapies have shown considerable anti-tumour activity and a favourable profile of local and systemic side effects. These include biodegradable polymers for interstitial chemotherapy, targeted toxins administered by convection enhanced delivery, and intra- and peritumourally injected genetically modified viruses conferring glioma-selective toxicity. Areas of possible improvement of these therapies and essential future developments are also outlined.

A novel E1B-55kD-deleted oncolytic adenovirus carrying mutant KRAS-regulated hdm2 transgene exerts specific antitumor efficacy on colorectal cancer cells

E1B-55kD-deleted adenoviruses have been used as conditionally replicative adenoviruses (CRAds) for therapeutic purposes in tumors with loss-of-function p53 mutation. To target cancer cells that harbor activating mutant KRAS (KRAS(aMut)) but spare p53(wild) normal cells, we constructed and examined by reporter assays a KRAS(aMut) but not p53-responsive promoter, the Deltap53REP2 promoter. The Deltap53REP2 promoter, derived from human double minute 2 (hdm2) P2 promoter with its p53 response elements being deleted, was used to regulate the expression of the hdm2 transgene in a novel E1B-55kD-deleted CRAd, the Ad-KRhdm2. The Ad-KRhdm2 selectively replicated in and exerted cytopathic effects on KRAS(aMut) colorectal cancer cell lines (HCT116, LoVo, LS174T, LS123, and SW620), regardless of their p53 gene statuses, by forming plaques and exhibiting cytopathic effect in cultured cells. Ad-KRhdm2, like other E1B-55kD-deleted adenoviruses, also exerted selective cytopathic effects on tumor cells with loss-of-function p53 mutant. The multiplicities of infection of Ad-KRhdm2 required to decrease 50% viability of KRAS(aMut) tumor cells cultured for 7 days were 440 to 3,400 times less than those of MRC5 normal fibroblasts and KRAS(wild)/p53(wild) RKO tumor cells. Intratumoral injection of Ad-KRhdm2 vectors exhibited specific lytic activities in nude mouse xenografts of KRAS(aMut) cell lines (LoVo, SW620, and LS174T) but not in xenografts of RKO cells. Transduction of KRAS(aMut)/p53(wild) HCT116, LoVo, and LS174T cells by Ad-KRhdm2 significantly increased Hdm2 expression, decreased p53 level, and abolished the p53-transactivating p21(Cip1) promoter activity. Ad-KRhdm2 has shown its therapeutic potential in KRAS(aMut) cancer cells and warrants further clinical trials.

Fiber mediated receptor masking in non-infected bystander cells restricts adenovirus cell killing effect but promotes adenovirus host co-existence. PLoS One. 2009;4:e8484. [PMID: 20041185 PMCID: PMC2793518 DOI: 10.1371/journal.pone.0008484]

The basic concept of conditionally replicating adenoviruses (CRAD) as oncolytic agents is that progenies generated from each round of infection will disperse, infect and kill new cancer cells. However, CRAD has only inhibited, but not eradicated tumor growth in xenograft tumor therapy, and CRAD therapy has had only marginal clinical benefit to cancer patients. Here, we found that CRAD propagation and cancer cell survival co-existed for long periods of time when infection was initiated at low multiplicity of infection (MOI), and cancer cell killing was inefficient and slow compared to the assumed cell killing effect upon infection at high MOI. Excessive production of fiber molecules from initial CRAD infection of only 1 to 2% cancer cells and their release prior to the viral particle itself caused a tropism-specific receptor masking in both infected and non-infected bystander cells. Consequently, the non-infected bystander cells were inefficiently bound and infected by CRAD progenies. Further, fiber overproduction with concomitant restriction of adenovirus spread was observed in xenograft cancer therapy models. Besides the CAR-binding Ad4, Ad5, and Ad37, infection with CD46-binding Ad35 and Ad11 also caused receptor masking. Fiber overproduction and its resulting receptor masking thus play a key role in limiting CRAD functionality, but potentially promote adenovirus and host cell co-existence. These findings also give important clues for understanding mechanisms underlying the natural infection course of various adenoviruses.

Oncolytic gene therapy for canine cancers: teaching old dog viruses new tricks

The use of viruses to treat cancer has been studied for decades. With the advancement of molecular biology, viruses have been modified and genetically engineered to optimize their ability to target cancer cells. Canine viruses, such as distemper virus and adenovirus, are being exploited for the treatment of canine cancer as the dog has proven to be a good comparative model for human cancer research and proof of concept investigations. In this review, we introduce the concept of oncolytic viruses and describe some of the preliminary attempts to use oncolytic viruses for the treatment of canine cancer.

Gene therapy of benign gynecological diseases

Gene therapy is the introduction of genetic material into patient's cells to achieve therapeutic benefit. Advances in molecular biology techniques and better understanding of disease pathogenesis have validated the use of a variety of genes as potential molecular targets for gene therapy based approaches. Gene therapy strategies include: mutation compensation of dysregulated genes; replacement of defective tumor-suppressor genes; inactivation of oncogenes; introduction of suicide genes; immunogenic therapy and antiangiogenesis based approaches. Preclinical studies of gene therapy for various gynecological disorders have not only shown to be feasible, but also showed promising results in diseases such as uterine leiomyomas and endometriosis. In recent years, significant improvement in gene transfer technology has led to the development of targetable vectors, which have fewer side-effects without compromising their efficacy. This review provides an update on developing gene therapy approaches to treat common gynecological diseases such as uterine leiomyoma and endometriosis.

Potent antitumor activity of double-regulated oncolytic adenovirus-mediated ST13 for colorectal cancer

Following targeted gene virotherapy, the suppression of tumorigenicity 13 (ST13) gene was inserted into the double-regulated oncolytic adenovirus SG500 to ensure more safety and potent antitumor activity against colorectal cancer in vitro and in vivo. We generated the ST13-expressing oncolytic adenovirus SG500-ST13, with which colorectal carcinoma cell lines SW620 and HCT116, and the lung fibroblast cell line WI38, were infected. Crystal violet staining was carried out to detect the cytopathic effect in cells, and the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide method was used to assay cell viability. The effect of apoptosis induced by SG500-ST13 was confirmed by Hoechst staining and the TdT-mediated dUTP-biotin nick-end labeling method. To further identify the antitumor effects of SG500-ST13 on HCT116 xenografts in Balb/c nude mice, the induction of cell death was assessed by hematoxylin-eosin staining. Immunohistochemical study was also carried out.

Replication competent Semliki Forest virus prolongs survival in experimental lung cancer

We evaluated the therapeutic potential of the replication competent vector VA7-EGFP, which is based on the avirulent Semliki Forest virus (SFV) strain A7 (74) carrying the EGFP marker gene in an orthotopic lung cancer tumor model in nude mice. We have previously shown that this oncolytic vector destroys tumor cells efficiently in vitro and in vivo (in subcutaneous tumor model). Tumor growth in animals with orthotopically implanted adenocarcinoma cells (A549) were monitored during the study with small animal CT. We show that locally administered virotherapy with VA7-EGFP increased survival rate in experimental lung cancer significantly (p < 0.001) comparable to results obtained with the second generation conditionally replicating adenoviral vector Ad5-Delta24TK-GFP, used for comparison. The limited efficacy in systemically administered oncolytic viruses is the essential problem in oncolytic virotherapy and also in this study we were not able to elicit significant response with systemic administration route. Despite the fact that tumor microenvironment in orthotopic lung cancer is more optimal, viruses failed to home to the tumors and were unable to initiate efficient intratumoral replication. Clearly, the efficacy of virotherapy is influenced by many factors such as the route of virus administration, immunological and physiological barriers and cancer cell-specific features (IFN-responsiveness).

Inhibition of renal cancer cell growth in vitro and in vivo with oncolytic adenovirus armed short hairpin RNA targeting Ki-67 encoding mRNA

RNA interference (RNAi) has been proved to be a powerful tool for gene knockdown purpose and holds great promise for the treatment of cancer. Our previous study demonstrated that the reduction of Ki-67 expression by means of chemically synthesized siRNAs and shRNAs expressed from plasmid resulted in proliferation inhibition in human renal carcinoma cells. In this study, we constructed a novel oncolytic adenovirus-based shRNA expression system, ZD55-Ki67, and explored ZD55-Ki67-mediated RNAi for Ki-67 gene silencing. Our results showed that ZD55-Ki67 could induce silencing of the Ki-67 gene effectively, allow for efficient tumor-specific viral replication and induce the apoptosis of tumor cells effectively in vitro and in nude mice. We conclude that combining shRNA gene therapy and oncolytic virotherapy can enhance antitumor efficacy as a result of synergism between CRAd oncolysis and shRNA antitumor responses.

Conditionally replicating E1B-deleted adenovirus driven by the squamous cell carcinoma antigen 2 promoter for uterine cervical cancer therapy

Cervical cancer is the second most common type of malignant tumor among women worldwide. When the disease is confined locally, it can be controlled with surgical resection and radiotherapy. However, patients with recurrent or metastatic disease often have a poor prognosis. Measurement of serum levels of squamous cell carcinoma (SCC) antigens has been widely used as serological markers for SCC of uterine cervix. Recently, it has been demonstrated that cervical cancer patients with elevated squamous cell carcinoma antigen-2 (SCCA2) expression in tumor cells carry a poor prognosis. Here, by using a luciferase reporter assay, we show that SCCA2 promoter was active in SCCA2-producing human cervical cancer cell lines, including Cx, Cxwj, SiHa and HeLa cells, but relatively quiescent in normal cervical epithelial cells. We then developed a conditionally replicating adenovirus, designated Ad-KFH, under the transcriptional control of the SCCA2 promoter. This E1B-55 kDa-deleted oncolytic adenovirus replicated specifically in and lysed SCCA2-producing cervical cancer cells. Furthermore, in a peritoneal metastatic tumor model, Ad-KFH retarded Cxwj tumor growth in NOD/severe combined immunodeficient mice and prolonged survival of tumor-bearing mice, especially when combined with cisplatin. These results suggest that Ad-KFH may provide a new strategy of gene therapy for advanced or recurrent uterine cervical cancer.

Carboxypeptidase-G2-based gene-directed enzyme-prodrug therapy: a new weapon in the GDEPT armoury

Gene-directed enzyme-prodrug therapy (GDEPT) aims to improve the therapeutic ratio (benefit versus toxic side-effects) of cancer chemotherapy. A gene encoding a 'suicide' enzyme is introduced into the tumour to convert a subsequently administered non-toxic prodrug into an active drug selectively in the tumour, but not in normal tissues. Significant effects can now be achieved in vitro and in targeted experimental models, and GDEPT therapies are entering the clinic. Our group has developed a GDEPT system that uses the bacterial enzyme carboxypeptidase G2 to convert nitrogen mustard prodrugs into potent DNA crosslinking agents, and a clinical trial of this system is pending.

Midkine promoter-based conditionally replicative adenovirus for targeting midkine-expressing human bladder cancer model

OBJECTIVES

To develop a novel therapeutic strategy against human bladder cancer using Ad-MK-E1a-a midkine (MK) promoter-regulated, conditionally replicating, adenovirus.

METHODS

We tested several human cancer cell lines in vitro, including those of bladder cancer (KK47, 5637, and T24), lung cancer (A549), and head and neck cancer (H891). In each cell line, we examined MK mRNA expression by TaqMan real-time quantitative polymerase chain reaction, MK promoter activity, after plasmid transfection, using a luciferase assay, and the transduction efficiency by co-transfection with the cytomegalovirus-beta-gal plasmid. In these cells, we assessed the cell type-specific replication of Ad-MK-E1a virus by measuring the E1a DNA copy number by real-time polymerase chain reaction and the cell growth inhibition due to this virus using the Alamar blue assay. In animal studies, nude mice were subcutaneously inoculated with KK47 cells and later intratumorally injected with phosphate-buffered saline or Ad5-CMV-LacZ or Ad-MK-E1a.

RESULTS

The MK mRNA expression level and MK promoter-driven luciferase activity were relatively greater and markedly increased, respectively, in the 5637, A549, and KK47 cells than in the T24 and H891 cells. After Ad-MK-E1a infection, the E1a DNA copy number increased more significantly in the KK47, 5637, and A549 cells than in the T24 and H891 cells. At a multiplicity of infection of 0.01, Ad-MK-E1a significantly inhibited KK47 and 5637 cell growth. In vivo, Ad-MK-E1a injection markedly inhibited KK47 tumor growth.

CONCLUSIONS

We have demonstrated the antitumor effect of Ad-MK-E1a in a human bladder cancer model overexpressing MK mRNA.

p53-expressing conditionally replicative adenovirus CNHK500-p53 against hepatocellular carcinoma in vitro

AIM: To develop a conditionally replicative gene-viral vector system called CNHK500-p53, which contains dual promoters within the E1 region, and combines the advantages of oncolytic virus and gene therapies for hepatocellular carcinoma (HCC).

METHODS: CNHK500-p53 was constructed by using human telomerase reverse transcriptase (hTERT) promoter to drive adenovirus E1a gene and hypoxia response element (HRE) promoter to drive adenovirus E1b gene. p53 gene expressing cassette was inserted into the genome of replicative virus. Viral replication experiments, cytopathic effect (CPE) and methyl thiazolyl tetrazolium (MTT) assay were performed to test the selective replication and oncolytic efficacy of CNHK500-p53.

RESULTS: Immunohistochemistry verified that infection with CNHK500-p53 was associated with selective replication of adenovirus and production of p53 protein in telomerase-positive and hypoxia-inducible factor-dependent HCC cells. p53 protein secreted from HepG2, infected with CNHK500-p53 was significantly higher than that infected with nonreplicative adenovirus Ad-p53 in vitro (388 ± 34.6 μg/L vs 76.3 ± 13.17 μg/L). Viral replication experiments showed that replication of CNHK500-p53 and CNHK500 or WtAd5, was much stronger than that of Ad-p53 in tested HCC cell lines. CPE and MTT assay indicated that CNHK500-p53 selectively replicated in and killed HCC cells while leaving normal cells unaffected.

CONCLUSION: A more efficient gene-viral system is developed by combining selective oncolysis with exogenous expression of p53 against HCC cells.

Pharmacodynamics of non-replicating viruses, bacteriocins and lysins

The pharmacodynamics of antibiotics and many other chemotherapeutic agents is often governed by a 'multi-hit' kinetics, which requires the binding of several molecules of the therapeutic agent for the killing of their targets. In contrast, the pharmacodynamics of novel alternative therapeutic agents, such as phages and bacteriocins against bacterial infections or viruses engineered to target tumour cells, is governed by a 'single-hit' kinetics according to which the agent will kill once it is bound to its target. In addition to requiring only a single molecule for killing, these agents bind irreversibly to their targets. Here, we explore the pharmacodynamics of such 'irreversible, single-hit inhibitors' using mathematical models. We focus on agents that do not replicate, i.e. in the case of phage therapy, we deal only with non-lytic phages and in the case of cancer treatment, we restrict our analysis to replication of incompetent viruses. We study the impact of adsorption on dead cells, heterogeneity in adsorption rates and spatial compartmentalization.

Drug discovery and delivery in the 21st century

Drug discovery in the late 20th century has increasingly focused on the definition and characterization of the macromolecular substrates that serve as targets for drug design. The advent of genomics and the molecular biology revolution has permitted both the definition of new targets and the characterization of the genetic basis of disease states. The introduction of powerful new technologies should greatly accelerate the pace of new drug discovery. Although genomics, both human and nonhuman, should in principle increase the number of potential drug targets and provide a greater understanding of cellular events contributing to the pathology of disease this has yet to occur in practice, primarily because of the underlying complexity of cellular signaling processes. The emerging discipline of systems biology is attempting to bring both order and understanding to these signaling processes. Genomics has, however, impacted on drug discovery in ways that are important beyond a mere increase in potential drug target numbers. Genomics has provided the tools of contemporary drug discovery, the pharmacogenomic pathways to personalized medicine, and has greatly influenced the nature of synthetic organic chemistry, a discipline that is still the cornerstone of contemporary drug discovery. In the future, genomics and the tools of molecular biology will have a corresponding impact on drug delivery processes and mechanisms through introduction of drug delivery machines capable of both synthesis and activation by disease-specific signals. Such machines will be based on a synthetic genome, using an expanded genetic code, and designed for specific drug synthesis and delivery and activation by a pathological signal. This essay is based upon a lecture of the same title presented at the Faculty of Medicine, Kuwait University during a visit in the spring of 2005. It is intended, as was the lecture, to be a broad, descriptive and speculative overview rather than a comprehensive and detailed review.

A Phase I Trial of Intravenous CG7870, a Replication-Selective, Prostate-Specific Antigen–Targeted Oncolytic Adenovirus, for the Treatment of Hormone-Refractory, Metastatic Prostate Cancer

CG7870 is a replication-selective oncolytic adenovirus genetically engineered to replicate preferentially in prostate tissue. In a previous phase I/II clinical trial of intraprostatic delivery of CG7870 for locally recurrent prostate cancer this virus was well tolerated. In this phase I study CG7870 was administered as a single intravenous infusion in a group-sequential dose escalation design (1 x 10(10) to 6 x 10(12) viral particles (vp)) to 23 patients with hormone-refractory metastatic prostate cancer. Flulike symptoms (fever, fatigue, rigors, nausea, and/or vomiting) were the most common adverse events. Three therapy-related grade 3 adverse events were reported, one of which (fatigue) was serious. At doses greater than 10(12) vp all five patients experienced asymptomatic grade 1 to 2 transaminitis and/or isolated d-dimer elevations starting on day 2 through 8; dose escalation was therefore halted at 6 x 10(12) vp. All tested patients had CG7870 genomes present in the peripheral blood for at least 90 minutes after infusion; patients in the highest dose group had persistence of genomes through 29 days. A "secondary" or "delayed" peak in plasma CG7870 genome copies (defined as a >10-fold increase in CG7870 genomes from nadir concentration) suggestive of active viral replication and shedding into the bloodstream was detected in 16/23 (70%) patients. CG7870 was detected in the saliva of 3 patients, whereas all urine samples tested negative. All patients developed antibodies to CG7870. Dose-related increases in interleukins 6 and 10 (IL-6, IL-10) blood levels were detected. The peak IL-6 concentration after CG7870 treatment was associated with a transient, asymptomatic decrease in blood pressure. No partial or complete prostate-specific antigen (PSA) responses were observed; however, 5 patients had a decrease in serum PSA of 25% to 49% following a single treatment, including 3 of 8 patients at the highest dose levels.

Genome microevolution of chikungunya viruses causing the Indian Ocean outbreak

BACKGROUND

A chikungunya virus outbreak of unprecedented magnitude is currently ongoing in Indian Ocean territories. In Réunion Island, this alphavirus has already infected about one-third of the human population. The main clinical symptom of the disease is a painful and invalidating poly-arthralgia. Besides the arthralgic form, 123 patients with a confirmed chikungunya infection have developed severe clinical signs, i.e., neurological signs or fulminant hepatitis.

METHODS AND FINDINGS

We report the nearly complete genome sequence of six selected viral isolates (isolated from five sera and one cerebrospinal fluid), along with partial sequences of glycoprotein E1 from a total of 127 patients from Réunion, Seychelles, Mauritius, Madagascar, and Mayotte islands. Our results indicate that the outbreak was initiated by a strain related to East-African isolates, from which viral variants have evolved following a traceable microevolution history. Unique molecular features of the outbreak isolates were identified. Notably, in the region coding for the non-structural proteins, ten amino acid changes were found, four of which were located in alphavirus-conserved positions of nsP2 (which contains helicase, protease, and RNA triphosphatase activities) and of the polymerase nsP4. The sole isolate obtained from the cerebrospinal fluid showed unique changes in nsP1 (T301I), nsP2 (Y642N), and nsP3 (E460 deletion), not obtained from isolates from sera. In the structural proteins region, two noteworthy changes (A226V and D284E) were observed in the membrane fusion glycoprotein E1. Homology 3D modelling allowed mapping of these two changes to regions that are important for membrane fusion and virion assembly. Change E1-A226V was absent in the initial strains but was observed in >90% of subsequent viral sequences from Réunion, denoting evolutionary success possibly due to adaptation to the mosquito vector.

CONCLUSIONS

The unique molecular features of the analyzed Indian Ocean isolates of chikungunya virus demonstrate their high evolutionary potential and suggest possible clues for understanding the atypical magnitude and virulence of this outbreak.