Transductional and transcriptional targeting of adenovirus for clinical applications

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.

Emerging Applications of Nanotechnology in Healthcare Systems: Grand Challenges and Perspectives

Healthcare, as a basic human right, has often become the focus of the development of innovative technologies. Technological progress has significantly contributed to the provision of high-quality, on-time, acceptable, and affordable healthcare. Advancements in nanoscience have led to the emergence of a new generation of nanostructures. Each of them has a unique set of properties that account for their astonishing applications. Since its inception, nanotechnology has continuously affected healthcare and has exerted a tremendous influence on its transformation, contributing to better outcomes. In the last two decades, the world has seen nanotechnology taking steps towards its omnipresence and the process has been accelerated by extensive research in various healthcare sectors. The inclusion of nanotechnology and its allied nanocarriers/nanosystems in medicine is known as nanomedicine, a field that has brought about numerous benefits in disease prevention, diagnosis, and treatment. Various nanosystems have been found to be better candidates for theranostic purposes, in contrast to conventional ones. This review paper will shed light on medically significant nanosystems, as well as their applications and limitations in areas such as gene therapy, targeted drug delivery, and in the treatment of cancer and various genetic diseases. Although nanotechnology holds immense potential, it is yet to be exploited. More efforts need to be directed to overcome these limitations and make full use of its potential in order to revolutionize the healthcare sector in near future.

Microbubble-mediated delivery of human adenoviruses does not elicit innate and adaptive immunity response in an immunocompetent mouse model of prostate cancer

Background

Gene transfer to malignant sites using human adenoviruses (hAds) has been limited because of their immunogenic nature and host specificity. Murine cells often lack some of the receptors needed for hAds attachment, thus murine cells are generally non-permissive for human adenoviral infection and replication, which limits translational studies.

Methods

We have developed a gene transfer method that uses a combination of lipid-encapsulated perfluorocarbon microbubbles and ultrasound to protect and deliver hAds to a target tissue, bypassing the requirement of specific receptors.

Results

In an in vitro model, we showed that murine TRAMP-C2 and human DU145 prostate cancer cells display a comparable expression pattern of receptors involved in hAds adhesion and internalization. We also demonstrated that murine and human cells showed a dose-dependent increase in the percentage of cells transduced by hAd-GFP (green fluorescent protein) after 24 h and that GFP transgene was efficiently expressed at 48 and 72 h post-transduction. To assess if our image-guided delivery system could effectively protect the hAds from the immune system in vivo, we injected healthy immunocompetent mice (C57BL/6) or mice bearing a syngeneic prostate tumor (TRAMP-C2) with hAd-GFP/MB complexes. Notably, we did not observe activation of innate (TNF-α and IL-6 cytokines), or adaptive immune response (neutralizing antibodies, INF-γ+ CD8⁺ T cells).

Conclusions

This study brings us a step closer to demonstrating the feasibility of murine cancer models to investigate the clinical translation of image guided site-specific adenoviral gene therapy mediated by ultrasound-targeted microbubble destruction.

Electronic supplementary material

The online version of this article (10.1186/s12967-019-1771-0) contains supplementary material, which is available to authorized users.

Efficient tumor transduction and antitumor efficacy in experimental human osteosarcoma using retroviral replicating vectors

Retroviral replicating vectors (RRVs) have achieved efficient tumor transduction and enhanced therapeutic benefit in a wide variety of cancer models. Here, we evaluated two different RRVs derived from amphotropic murine leukemia virus (AMLV) and gibbon ape leukemia virus (GALV), which utilize different cellular receptors (PiT-2 and PiT-1, respectively) for viral entry, in human osteosarcoma cells. Quantitative RT-PCR showed that low levels of expression of both receptors were observed in normal and non-malignant cells. However, high PiT-2 (for AMLV) and low PiT-1 (for GALV) expression was observed in most osteosarcoma cell lines. Accordingly, AMLV expressing the green fluorescent protein gene infected and replicated more efficiently than GALV in most osteosarcoma cell lines. Furthermore, RRVs expressing the cytosine deaminase prodrug activator gene showed differential cytotoxicity that correlated with the results of viral spread. AMLV-RRV-mediated prodrug activator gene therapy achieved significant inhibition of subcutaneous MG-63 tumor growth over GALV in nude mice. These data indicate that AMLV vectors predominate over GALV in human osteosarcoma cells. Moreover, our findings support the potential utility of the two RRVs in personalized cancer virotherapy on the basis of receptor expression.

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.

Potent antitumor activity of Oct4 and hypoxia dual-regulated oncolytic adenovirus against bladder cancer

Most solid tumors undergo hypoxia, leading to rapid cell division, metastasis and expansion of a cell population with hallmarks of cancer stem cells (CSCs). Tumor-selective replication of oncolytic adenoviruses may be hindered by oxygen deprivation in tumors. It is desirable to develop a potent oncolytic adenovirus, retaining its antitumor activity even in a hypoxic environment. We have previously generated an Oct4-dependent oncolytic adenovirus, namely Ad9OC, driven by nine copies of the Oct4 response element (ORE) for specifically killing Oct4-overexpressing bladder tumors. Here, we developed a novel Oct4 and hypoxia dual-regulated oncolytic adenovirus, designated AdLCY, driven by both hypoxia response element (HRE) and ORE. We showed that hypoxia-inducible factor (HIF)-2α and Oct4 were frequently overexpressed in hypoxic bladder cancer cells, and HIF-2α was involved in HRE-dependent and Oct4 transactivation. AdLCY exhibited higher cytolytic activities than Ad9OC against hypoxic bladder cancer cells, while sparing normal cells. AdLCY exerted potent antitumor effects in mice bearing human bladder tumor xenografts and syngeneic bladder tumors. It could target hypoxic CD44- and CD133-positive bladder tumor cells. Therefore, AdLCY may have therapeutic potential for targeting hypoxic bladder tumors and CSCs. As Oct4 is expressed in various cancers, AdLCY may be further explored as a broad-spectrum anticancer agent.

Species D human adenovirus type 9 exhibits better virus-spread ability for antitumor efficacy among alternative serotypes

Species C human adenovirus serotype 5 (HAdV-C5) is widely used as a vector for cancer gene therapy, because it efficiently transduces target cells. A variety of HAdV-C5 vectors have been developed and tested in vitro and in vivo for cancer gene therapy. While clinical trials with HAdV-C5 vectors resulted in effective responses in many cancer patients, administration of HAdV-C5 vectors to solid tumors showed responses in a limited area. A biological barrier in tumor mass is considered to hinder viral spread of HAdV-C5 vectors from infected cells. Therefore, efficient virus-spread from an infected tumor cell to surrounding tumor cells is required for successful cancer gene therapy. In this study, we compared HAdV-C5 to sixteen other HAdV serotypes selected from species A to G for virus-spread ability in vitro. HAdV-D9 showed better virus-spread ability than other serotypes, and its viral progeny were efficiently released from infected cells during viral replication. Although the HAdV-D9 fiber protein contains a binding site for coxsackie B virus and adenovirus receptor (CAR), HAdV-D9 showed expanded tropism for infection due to human CAR (hCAR)-independent attachment to target cells. HAdV-D9 infection effectively killed hCAR-negative cancer cells as well as hCAR-positive cancer cells. These results suggest that HADV-D9, with its better virus-spread ability, could have improved therapeutic efficacy in solid tumors compared to HAdV-C5.

Oncolytic immunotherapy: where are we clinically?

Following a century of preclinical and clinical work, oncolytic viruses are now proving themselves in randomized phase 3 trials. Interestingly, human data indicates that these agents have potent immunostimulatory activity, raising the possibility that the key consequence of oncolysis might be induction of antitumor immunity, especially in the context of viruses harboring immunostimulatory transgenes. While safety and efficacy of many types of oncolytic viruses, including adenovirus, herpes, reo, and vaccinia seem promising, few mechanisms of action studies have been performed with human substrates. Thus, the relative contribution of "pure" oncolysis, the immune response resulting from oncolysis, and the added benefit of adding a transgene remain poorly understood. Here, the available clinical data on oncolytic viruses is reviewed, with emphasis on immunological aspects.

Highly efficient tumor transduction and antitumor efficacy in experimental human malignant mesothelioma using replicating gibbon ape leukemia virus

Retroviral replicating vectors (RRVs) have been shown to achieve efficient tumor transduction and enhanced therapeutic benefit in a wide variety of cancer models. Here we evaluated two different RRVs derived from amphotropic murine leukemia virus (AMLV) and gibbon ape leukemia virus (GALV), in human malignant mesothelioma cells. In vitro, both RRVs expressing the green fluorescent protein gene efficiently replicated in most mesothelioma cell lines tested, but not in normal mesothelial cells. Notably, in ACC-MESO-1 mesothelioma cells that were not permissive for AMLV-RRV, the GALV-RRV could spread efficiently in culture and in mice with subcutaneous xenografts by in vivo fluorescence imaging. Next, GALV-RRV expressing the cytosine deaminase prodrug activator gene showed efficient killing of ACC-MESO-1 cells in a prodrug 5-fluorocytosine dose-dependent manner, compared with AMLV-RRV. GALV-RRV-mediated prodrug activator gene therapy achieved significant inhibition of subcutaneous ACC-MESO-1 tumor growth in nude mice. Quantitative reverse transcription PCR demonstrated that ACC-MESO-1 cells express higher PiT-1 (GALV receptor) and lower PiT-2 (AMLV receptor) compared with normal mesothelial cells and other mesothelioma cells, presumably accounting for the distinctive finding that GALV-RRV replicates much more robustly than AMLV-RRV in these cells. These data indicate the potential utility of GALV-RRV-mediated prodrug activator gene therapy in the treatment of mesothelioma.

We still have a long way to go to effectively deliver genes!

Gene therapy is emerging as a revolutionary alternative to conventional therapeutic approaches. However, its clinical application is still hampered by the lack of safe and effective gene delivery techniques. Among the plethora of diverse approaches used to ferry nucleic acids into target cells, non-viral vectors represent promising and safer alternatives to viruses and physical techniques. Both cationic lipids and polymers spontaneously wrap and shrink the genetic material in complexes named lipoplexes and polyplexes, respectively, thereby protecting it and shielding its negative charges. The development of non-viral vectors commenced more than two decades ago. Since then, some major classes of interesting molecules have been identified and modified to optimize their properties. However, the way towards the final goal of gene delivery, i.e. protein expression or gene silencing, is filled with obstacles and current non-viral carriers still have concerns about their overall efficiency. We strongly believe that the future of non-viral gene delivery relies on the development of multifunctional vectors specifically tailored with diverse functionalities that act more like viruses. Although these vectors are still a long way from clinical practice they are the ideal platform to effectively shuttle the genetic material to target cells in a safe and controlled way. In this review, after briefly introducing the basis of gene delivery and therapeutic applications we discuss the main polymeric and lipidic vectors utilized for gene delivery, focusing on the strategies adopted to overcome the major weaknesses inherent to their still limited activity, on the way towards ideal multifunctional vectors.

Enhanced delivery of mda-7/IL-24 using a serotype chimeric adenovirus (Ad.5/3) in combination with the Apogossypol derivative BI-97C1 (Sabutoclax) improves therapeutic efficacy in low CAR colorectal cancer cells

Adenovirus (Ad)-based gene therapy represents a potentially viable strategy for treating colorectal cancer. The infectivity of serotype 5 adenovirus (Ad.5), routinely used as a transgene delivery vector, is dependent on Coxsackie-adenovirus receptors (CAR). CAR expression is downregulated in many cancers thus preventing optimum therapeutic efficiency of Ad.5-based therapies. To overcome the low CAR problem, a serotype chimerism approach was used to generate a recombinant Ad (Ad.5/3) that is capable of infecting cancer cells via Ad.3 receptors in a CAR-independent manner. We evaluated the improved transgene delivery and efficacy of Ad.5/3 recombinant virus expressing melanoma differentiation associated gene-7/interleukin-24 (mda-7/IL-24), an effective wide-spectrum cancer-selective therapeutic. In low CAR human colorectal cancer cells RKO, wild-type Ad.5 virus expressing mda-7/IL-24 (Ad.5-mda-7) failed to infect efficiently resulting in lack of expression of MDA-7/IL-24 or induction of apoptosis. However, a recombinant Ad.5/3 virus expressing mda-7/IL-24 (Ad.5/3-mda-7) efficiently infected RKO cells resulting in higher MDA-7/IL-24 expression and inhibition of cell growth both in vitro and in nude mice xenograft models. Addition of the novel Bcl-2 family pharmacological inhibitor Apogossypol derivative BI-97C1 (Sabutoclax) significantly augmented the efficacy of Ad.5/3-mda-7. A combination regimen of suboptimal doses of Ad.5/3-mda-7 and BI-97C1 profoundly enhanced cytotoxicity in RKO cells both in vitro and in vivo. Considering the fact that Ad.5-mda-7 has demonstrated significant objective responses in a Phase I clinical trial for advanced solid tumors, Ad.5/3-mda-7 alone or in combination with BI-97C1 would be predicted to exert significantly improved therapeutic efficacy in colorectal cancer patients.

Virotherapy induces massive infiltration of neutrophils in a subset of tumors defined by a strong endogenous interferon response activity

Oncolytic virotherapy has shown substantial promises as an alternative therapeutic modality for solid tumors in both preclinical studies and clinical trials. The main therapeutic activity of virotherapy derives from the direct lytic effect associated with virus replication and the induction of host immune responses to the infected tumor cells. Here we show that some human and murine tumor cell lines are highly resistant to the lytic effect of a type II herpes simplex virus-derived oncolytic virus, FusOn-H2, which was constructed by deleting the N-terminal region of the ICP10 gene. However, these tumor cells still respond exceptionally well to FusOn-H2 virotherapy in vivo. Histological examination of the treated tumors revealed that, in contrast to tumors supporting FusOn-H2 replication, implants of these highly resistant lines showed massive infiltration of neutrophils after virotherapy. Further analysis showed that there is a correlation between an intrinsically strong interferon response activity and the recruitment of neutrophils in these tumors. These results suggest that an innate immune response mainly represented by neutrophils may be part of the virotherapy-mediated antitumor mechanism in these tumors.

Adenovirus-retrovirus hybrid vectors achieve highly enhanced tumor transduction and antitumor efficacy in vivo

Murine leukemia virus (MLV)-based replication-competent retrovirus (RCR) vectors have been shown to mediate efficient, selective, and persistent tumor transduction, thereby achieving significant therapeutic benefit in a wide variety of cancer models. To further augment the efficiency of this strategy, we have developed a delivery method employing a gutted adenovirus encoding an RCR vector (AdRCR); thus, tumor cells transduced with the adenoviral vector transiently become RCR vector producer cells in situ. As expected, high-titer AdRCR achieved significantly higher initial transduction levels in human cancer cells both in vitro and in vivo, as compared to the original RCR vector itself. Notably, even at equivalent initial transduction levels, more secondary RCR progeny were produced from AdRCR-transduced cells as compared to RCR-transduced cells, resulting in further acceleration of subsequent RCR replication kinetics. In pre-established tumor models in vivo, prodrug activator gene therapy with high-titer AdRCR could achieve enhanced efficacy compared to RCR alone, in a dose-dependent manner. Thus, AdRCR hybrid vectors offer the advantages of high production titers characteristic of adenovirus and secondary production of RCR in situ, which not only accelerates subsequent vector spread and progressive tumor transduction, but can also significantly enhance the therapeutic efficacy of RCR-mediated prodrug activator gene therapy.

Second-generation HIF-activated oncolytic adenoviruses with improved replication, oncolytic, and antitumor efficacy

There is a need to develop more potent oncolytic adenoviruses that exhibit increased anti-tumor activity in patients. The HYPR-Ads are targeted oncolytic adenoviruses that specifically kill tumor cells which express active hypoxia-inducible factor (HIF). While therapeutically efficacious, the HYPR-Ads exhibited attenuated replication and oncolytic activity. To overcome these deficiencies and improve anti-tumor efficacy, we created new HIF-activated oncolytic Ads, HIF-Ad and HIF-Ad-IL4, which have two key changes: (i) a modified HIF-responsive promoter to regulate the E1A replication gene and (ii) insertion of the E3 gene region. The HIF-Ads demonstrated conditional activation of E1A expression under hypoxia. Importantly, the HIF-Ads exhibit hypoxia-dependent replication, oncolytic, and cellular release activities and potent anti-tumor efficacy, all of which are significantly greater than the HYPR-Ads. Notably, HIF-Ad-IL4 treatment led to regressions in tumor size by 70% and extensive tumor infiltration by leukocytes resulting in an anti-tumor efficacy that is up to 6-fold greater than the HYPR-Ads, HIF-Ad, and wild-type adenovirus treatment. These studies demonstrate that treatment with a HIF-activated oncolytic adenovirus leads to a measurable therapeutic response. The novel design of the HIF-Ads represents a significant improvement compared to first-generation oncolytic Ads and has great potential to increase the efficacy of this cancer therapy.

A conditionally replicative adenovirus, CRAd-S-pK7, can target endometriosis with a cell-killing effect

BACKGROUND

Novel therapeutic approaches for endometriosis based on molecular strategies may prove to be useful. Conditionally replicative adenoviruses (CRAds) are designed to exploit key differences between target and normal cells. The wild-type adenovirus (Adwt) promoter can be replaced by tissue-specific promoters, allowing viral replication only in target cells. Viral infectivity can be enhanced by altering Ad tropism via fiber modification. We investigated whether CRAds can be used to target endometriosis and determined the most efficient transcriptional- and transductional-targeting strategy.

METHODS

An in vitro study was carried out using human endometriotic cell lines, 11Z (epithelial) and 22B (stromal), normal human ovarian surface epithelial cell line (NOSE006) and primary human endometriosis cells. A total of 9 promoters and 12 Ad tropism modifications were screened by means of a luciferase reporter assay. From this screening data, three CRAds (CRAd-S-pK7, CRAd-S-RGD, CRAd-S-F5/3sigma1, all incorporating the survivin promoter but with different fiber modifications) were selected to perform experiments using Adwt and a replication-deficient virus as controls. CRAds were constructed using a plasmid recombination system. Viral-binding capacity, rates of entry and DNA replication were evaluated by quantitative real-time PCR of viral genome copy. Cell-killing effects were determined by crystal violet staining and a cell viability assay for different concentrations of viral particles per cell.

RESULTS

Comparison of promoters demonstrated that the survivin promoter exhibited the highest induction in both endometriotic cell lines. Among the fiber-modified viruses, the polylysine modification (pK7) showed the best infection enhancement. CRAd-S-pK7 was validated as the optimal CRAd to target endometriosis in terms of binding ability, entry kinetics, DNA replication and cell-killing effect. CRAd-S-pK7 also exhibited a high level of DNA replication in primary endometriosis cells.

CONCLUSIONS

CRAd-S-pK7 has the best infection and cell-killing effect in the context of endometriosis. It could prove to be a useful novel method to target refractory cases of endometriosis.

Generation of anti-TLR2 intrabody mediating inhibition of macrophage surface TLR2 expression and TLR2-driven cell activation

Background

Toll-like receptor (TLR) 2 is a component of the innate immune system and senses specific pathogen associated molecular patterns (PAMPs) of both microbial and viral origin. Cell activation via TLR2 and other pattern recognition receptors (PRRs) contributes to sepsis pathology and chronic inflammation both relying on overamplification of an immune response. Intracellular antibodies expressed and retained inside the endoplasmatic reticulum (ER-intrabodies) are applied to block translocation of secreted and cell surface molecules from the ER to the cell surface resulting in functional inhibition of the target protein. Here we describe generation and application of a functional anti-TLR2 ER intrabody (αT2ib) which was generated from an antagonistic monoclonal antibody (mAb) towards human and murine TLR2 (T2.5) to inhibit the function of TLR2. αT2ib is a scFv fragment comprising the variable domain of the heavy chain and the variable domain of the light chain of mAb T2.5 linked together by a synthetic (Gly₄Ser)₃ amino acid sequence.

Results

Coexpression of αT2ib and mouse TLR2 in HEK293 cells led to efficient retention and accumulation of TLR2 inside the ER compartment. Co-immunoprecipitation of human TLR2 with αT2ib indicated interaction of αT2ib with its cognate antigen within cells. αT2ib inhibited NF-κB driven reporter gene activation via TLR2 but not through TLR3, TLR4, or TLR9 if coexpressed in HEK293 cells. Co-transfection of human TLR2 with increasing amounts of the expression plasmid encoding αT2ib into HEK293 cells demonstrated high efficiency of the TLR2-αT2ib interaction. The αT2ib open reading frame was integrated into an adenoviral cosmid vector for production of recombinant adenovirus (AdV)-αT2ib. Transduction with AdVαT2ib specifically inhibited TLR2 surface expression of murine RAW264.7 and primary macrophages derived from bone marrow (BMM). Furthermore, TLR2 activation dependent TNFα mRNA accumulation, as well as TNFα translation and release by macrophages were largely abrogated upon transduction of αT2ib. αT2ib was expressed in BMM and splenocytes over 6 days upon systemic infection with AdVαT2ib. Systemic transduction applying AdVαT2ib rendered immune cells largely non-responsive to tripalmitoyl-peptide challenge. Our results show persistent paralysis of TLR2 activity and thus inhibition of immune activation.

Conclusion

The generated anti-TLR2 scFv intrabody inhibits specifically and very efficiently TLR2 ligand-driven cell activation in vitro and ex vivo. This indicates a therapeutic potential of αT2ib in microbial or viral infections.

Enhanced delivery of mda-7/IL-24 using a serotype chimeric adenovirus (Ad.5/3) improves therapeutic efficacy in low CAR prostate cancer cells

Gene therapy is being examined as a potential strategy for treating prostate cancer. Serotype 5 adenovirus (Ad.5) is routinely used as a vector for transgene delivery. However, the infectivity of Ad.5 is dependent on Coxsackie-adenovirus receptors (CARs); many tumor types show a reduction in this receptor in vivo, thereby limiting therapeutic gene transduction. Serotype chimerism is one approach to circumvent CAR deficiency; this strategy is used to generate an Ad.5/3-recombinant Ad that infects cancer cells through Ad.3 receptors in a CAR-independent manner. In this report, the enhanced transgene delivery and efficacy of Ad.5/3-recombinant virus was evaluated using an effective wide-spectrum anticancer therapeutic melanoma differentiation-associated gene-7/interleukin-24 (mda-7/IL-24). Our data show that in low CAR human prostate cancer cells (PC-3), a recombinant Ad.5/3 virus delivering mda-7/IL-24 (Ad.5/3-mda-7) is more efficacious than an Ad.5 virus encoding mda-7/IL-24 (Ad.5-mda-7) in infecting tumor cells, expressing MDA-7/IL-24 protein, inducing cancer-specific apoptosis, inhibiting in vivo tumor growth and exerting an antitumor 'bystander' effect in a nude mouse xenograft model. Considering the fact that Ad.5-mda-7 has shown significant objective responses in a phase I clinical trial for solid tumors, Ad.5/3-mda-7 is predicted to exert enhanced therapeutic benefit in patients with prostate 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.

A potent, imaging adenoviral vector driven by the cancer-selective mucin-1 promoter that targets breast cancer metastasis

PURPOSE

With breast cancer, early detection and proper staging are critical, and will often influence both the treatment regimen and the therapeutic outcome for those affected with this disease. Improvements in these areas will play a profound role in reducing mortality from breast cancer.

EXPERIMENTAL DESIGN

In this work we developed a breast cancer-targeted serotype 5 adenoviral vector, utilizing the tumor-specific mucin-1 promoter in combination with the two-step transcriptional amplification system, a system used to augment the activity of weak tissue-specific promoters.

RESULTS

We showed the strong specificity of this tumor-selective adenovirus to express the luciferase optical imaging gene, leading to diagnostic signals that enabled detection of sentinel lymph node metastasis of breast cancer. Furthermore, we were able to target hepatic metastases following systemic administration of this mucin-1 selective virus.

CONCLUSIONS

Collectively, we showed that the amplified mucin-1 promoter-driven vector is able to deliver to and selectively express a desirable transgene in metastatic lesions of breast tumors. This work has strong clinical relevance to current diagnostic staging approaches, and could add to targeted therapeutic strategies to advance the fight against breast cancer.

Combined transductional untargeting/retargeting and transcriptional restriction enhances adenovirus gene targeting and therapy for hepatic colorectal cancer tumors

Unresectable hepatic colorectal cancer (CRC) metastases are a leading cause of cancer mortality. These tumors and other epithelial tumors often express both cyclooxygenase-2 (COX-2) and carcinoembryonic antigen (CEA). Because adenovirus (Ad) vectors infect the liver and lack tumor tropism, they cannot be used for systemic therapy of hepatic metastases. We used COX-2 transcriptional restriction, in combination with transductional Ad hepatic untargeting and tumor retargeting by a bispecific adapter, sCARhMFE, composed of sCAR [the coxsackie/Ad receptor (CAR) ectodomain] and MFE-23 (a single-chain anti-CEA antibody), to untarget liver after i.v. administration of Ad vectors expressing firefly luciferase and to retarget virus to hepatic colorectal tumor xenografts and non-small cell lung tumor xenografts. To improve both liver untargeting and tumor retargeting, we developed sCARfMFE, a trimerized sCARhMFE adapter. Trimerization greatly improves both untargeting of CAR-dependent Ad infection and CEA-dependent virus retargeting in culture and in vivo. Combining sCARfMFE bispecific adapter transductional liver untargeting and transductional tumor retargeting with COX-2 transcriptional tumor-restricted transgene expression increases systemically administered Ad therapeutic efficacy for hepatic CRC tumors, using herpes virus type 1 thymidine kinase (HSV1-tk) as a therapeutic gene in conjunction with the prodrug ganciclovir (GCV). Both transductional untargeting and COX-2 transcriptional restriction also reduce HSV1-tk/GCV hepatic toxicity. In addition, transductional sCARfMFE untargeting reduces the innate immune response to systemic Ad administration. Combined transductional liver Ad untargeting, transductional tumor retargeting, and transcriptional transgene restriction suggests a means to engineer practical, effective therapeutic agents for hepatic CRC metastases in particular, as well as hepatic metastases of other epithelial cancers.

Imaging of viral thymidine kinase gene expression by replicating oncolytic adenovirus and prediction of therapeutic efficacy

PURPOSE

We have used a genetically attenuated adenoviral vector which expresses HSVtk to assess the possible additive role of suicidal gene therapy for enhanced oncolytic effect of the virus. Expression of TK was measured using a radiotracer-based molecular counting and imaging system.

MATERIALS AND METHODS

Replication-competent recombinant adenoviral vector (Ad-DeltaE1B19/55) was used in this study, whereas replication-incompetent adenovirus (Ad-DeltaE1A) was generated as a control. Both Ad-DeltaE1B19/55-TK and Ad-DeltaE1A-TK comprise the HSVtk gene inserted into the E3 region of the viruses. YCC-2 cells were infected with the viruses and incubated with 2'-deoxy-2'-fluoro-beta-D-arabinofuranosyl-5-iodouracil (I-131 FIAU) to measure amount of radioactivity. The cytotoxicity of the viruses was determined, and gamma ray imaging of HSVtk gene was performed. MTT assay was also performed after GCV treatment.

RESULTS

On gamma counter-analyses, counts/ minute (cpm)/microg of protein showed MOIs dependency with DeltaE1B19/55-TK infection. On MTT assay, Ad-DeltaE1B19/55-TK led to more efficient cell killing than Ad-DeltaE1A-TK. On plate imaging by gamma camera, both Ad-DeltaE1B19/55-TK and Ad-DeltaE1A-TK infected cells showed increased I-131 FIAU uptake in a MOI dependent pattern, and with GCV treatment, cell viability of DeltaE1B19/55-TK infection was remarkably reduced compared to that of Ad-DeltaE1A-TK infection.

CONCLUSION

Replicating Ad-DeltaE1B19/55-TK showed more efficient TK expression even in the presence of higher-cancer cell killing effects compared to non-replicating Ad-DeltaE1A-TK. Therefore, GCV treatment still possessed an additive role to oncolytic effect of Ad-DeltaE1B19/55-TK. The expression of TK by oncolytic viruses could rapidly be screened using a radiotracer-based counting and imaging technique.

The cyclo-oxygenase 2 promoter is induced in nontarget cells following adenovirus infection, but an AU-rich 3'-untranslated region destabilization element can increase specificity

BACKGROUND

Cyclo-oxygenase 2 (Cox-2) is expressed in many types of tumors, but typically undetectable in normal tissues. However, Cox-2 is known to be induced following infection by many microbial agents, which might threaten the tumor selectivity of the Cox-2 promoter in the context of virotherapy or viral gene delivery. Cox-2 expression is regulated in part post-transcriptionally by stimulation or inhibition of mRNA degradation by 3'-untranslated region (3'-UTR) AU-rich elements. In the present study, we investigated the induction of the Cox-2 promoter both in normal and tumor cells after adenovirus infection and explored the utility of AU-rich elements for regaining promoter selectivity.

METHODS

Nontumor and tumor cells were transfected in vitro and in vivo with plasmids containing the Cox-2 or cytomegalovirus immediate early promoter driving luciferase (with or without 3'-UTR elements) followed by adenoviral infection. Selectivity and activity of the promoters and 3'-UTR elements were analysed by luciferase assay and in-vivo imaging.

RESULTS

The Cox-2 promoter was induced in both normal and tumor cells following infection with E1 containing replicative adenoviruses but not in the absence of E1. Utilization of AU-rich elements counteracted promoter induction in vitro and in vivo in nonmalignant cells but not in cancer cells, thus increasing the selectivity of the approach ten-fold without loss of potency.

CONCLUSIONS

Adenoviral infection induces the Cox-2 promoter in normal and tumor cells, which might compromise specificity of the promoter. Utilization of AU-rich destabilization elements can rescue the tumor selectivity of the promoter.

Toward gene therapy of endometriosis: transductional and transcriptional targeting of adenoviral vectors to endometriosis cells

OBJECTIVE

The purpose of this study was to screen a panel of targeted adenoviruses as vectors for endometriosis gene therapy.

STUDY DESIGN

Endometriotic cells were obtained from subjects with ovarian endometriomas. Liver tissues were taken from donors during hepatic transplantation surgery. Human endometriotic cells and liver tissues were transfected by targeted adenoviruses expressing luciferase reporter gene. Luciferase activity that was mediated by each virus was expressed as a percentage of adenovirus serotype 5 (Ad5-CMV-luc) activity. The 2-tailed Studentt test was used to compare the adenovirus data.

RESULTS

In endometriotic cells, the adenovirus-RGD (Ad-RGD-luc), adenovirus under secretory leukocyte protease inhibitor promoter (Ad-SLPI-luc), and adenovirus under heparanase promoter (Ad-heparanase-luc) showed significantly higher activity, compared with the adenovirus serotype 5. In liver tissues, adenovirus-survivin (Ad-survivin-luc) and Ad-heparanase-luc had significantly lower activity, compared with adenovirus serotype 5.

CONCLUSION

Ad-heparanase-luc showed "endometriosis on, liver off" phenotype and is a promising vector for endometriosis gene therapy.

Adenovirus-mediated transduction of auto- and dual-regulated transgene expression in mammalian cells

Transduction of therapeutic transgenes using multiply attenuated viral vectors is considered an essential technology for gene therapy scenarios. While first-generation viral transduction systems were engineered for constitutive expression of a single therapeutic transgene, most advanced viral gene-transfer technologies enable regulated expression of several transgenes. Efficient transfer of numerous transgenes enables co-expression of therapeutic transgenes along with marker or selection determinants, production of multi-subunit protein complexes, or combinatorial expression of a particular set of genes to treat multigenic disorders. Likewise, adjustable transcription control is fundamental to adapt therapeutic protein production to the changing daily dosing regimes of a patient, to titrate expression of protein pharmaceuticals into the therapeutic window, and to reverse dosing upon completion of the therapy. Also, conditional transcription dosing has been successfully used for production of difficult-to-express protein therapeutics in biopharmaceutical manufacturing and for sophisticated gene-function analysis in basic research programs. By way of example, we provide detailed design (auto-regulated and binary dual-regulated expression configurations), production (generation, purification, and quality control of transgenic adenovirus particles), and handling (transduction) protocols for adenovirus vectors that enable transduction of mammalian cells for regulated expression of several transgenes.

Gene therapy of gynaecological diseases

Gene therapy represents a potentially useful approach for the treatment of diseases refractory to conventional therapies. Various preclinical and clinical strategies have been explored for treatment of gynaecological diseases. Given the most severe unmet clinical need, much of the work has been performed with gynaecological cancers and ovarian cancer in particular. Although the safety of many treatment strategies has been demonstrated in early phase clinical trials, efficacy has been mostly limited heretofore. Major challenges include improving the vectors used with the aim of more effective and selective delivery. In addition, effective penetration into and spreading within advanced and complex tumour masses and metastases remains challenging. This review focuses on existing and developmental gene transfer applications for gynaecological diseases.

High Cancer-Specific Expression of Mesothelin (MSLN) Is Attributable to an Upstream Enhancer Containing a Transcription Enhancer Factor–Dependent MCAT Motif

Identification of genes with cancer-specific overexpression offers the potential to efficiently discover cancer-specific activities in an unbiased manner. We apply this paradigm to study mesothelin (MSLN) overexpression, a nearly ubiquitous, diagnostically and therapeutically useful characteristic of pancreatic cancer. We identified an 18-bp upstream enhancer, termed CanScript, strongly activating transcription from an otherwise weak tissue-nonspecific promoter and operating selectively in cells having aberrantly elevated cancer-specific MSLN transcription. Introducing mutations into CanScript showed two functionally distinct sites: an Sp1-like site and an MCAT element. Gel retardation and chromatin immunoprecipitation assays showed the MCAT element to be bound by transcription enhancer factor (TEF)-1 (TEAD1) in vitro and in vivo. The presence of TEF-1 was required for MSLN protein overexpression as determined by TEF-1 knockdown experiments. The cancer specificity seemed to be provided by a putative limiting cofactor of TEF-1 that could be outcompeted by exogenous TEF-1 only in a MSLN-overexpressing cell line. A CanScript concatemer offered enhanced activity. These results identify a TEF family member as a major regulator of MSLN overexpression, a fundamental characteristic of pancreatic and other cancers, perhaps due to an upstream and highly frequent aberrant cellular activity. The CanScript sequence represents a modular element for cancer-specific targeting, potentially suitable for nearly a third of human malignancies.

A mosaic fiber adenovirus serotype 5 vector containing reovirus sigma 1 and adenovirus serotype 3 knob fibers increases transduction in an ovarian cancer ex vivo system via a coxsackie and adenovirus receptor-independent pathway

PURPOSE

Adenovirus serotype 5 (Ad5) has been used for gene therapy with limited success due to insufficient infectivity in cells with low expression of the primary receptor, the coxsackie and adenovirus receptor (CAR). Evidence that adenovirus serotype receptors other than CAR may be of use was presented in previous studies that showed that the Ad3 receptor is expressed at high levels in ovarian cancer cells. We hypothesized that combined use of unique chimeric fibers in the context of novel mosaic adenovirus vectors would enhance infectivity via non-CAR pathways in ovarian cancer cells.

EXPERIMENTAL DESIGN

We constructed and characterized Ad5 vectors that use Ad3 knob and reovirus fibers to generate a mosaic fiber virion. Serotype 3 Dearing reovirus uses a fiber-like sigma 1 protein to infect cells expressing sialic acid and junction adhesion molecule 1. We therefore constructed a mosaic fiber Ad5 vector, designated Ad5/3-sigma 1, encoding two fibers: a sigma 1 chimeric fiber and the chimeric Ad5/3 fiber composed of an Ad3 knob.

RESULTS

Functionally, Ad5/3-sigma 1 used sialic acid, junction adhesion molecule 1, and Ad3 receptor for cell transduction and achieved maximum infectivity enhancement in ovarian cancer cells with low CAR expression. Furthermore, Ad5/3-sigma 1 achieved infectivity enhancement in primary tissue slices of human ovarian tumor.

CONCLUSIONS

We have developed a new type of Ad5 vector with the novel tropism, possessing fibers from Ad3 and reovirus, which exhibits enhanced infectivity via CAR-independent pathway(s). In addition, the flexible genetic platform of vector allows different combination of fiber variants that can be incorporated within the same particle.

Blocking translocation of cell surface molecules from the ER to the cell surface by intracellular antibodies targeted to the ER

Intracellular antibodies (intrabodies) constitute a potent tool to neutralize the function of target proteins inside specific cell compartments (cytosol, nucleus, mitochondria and ER). The intrabody technology is an attractive alternative to the generation of gene-targeted knockout animals and complements or replaces knockdown techniques such as antisense-RNA, RNAi and RNA aptamers. This article focuses on intrabodies targeted to the ER. Intracellular anti-bodies expressed and retained inside the ER (ER intrabodies) are shown to be highly efficient in blocking the translocation of secreted and cell surface molecules from the ER to the cell surface.The advantage of ER intrabodies over cytoplasmic intrabodies is that they are correctly folded and easier to select. A particular advantage of the intrabody technology over existing ones is the possibility of inhibiting selectively post-translational modifications of proteins.The main applications of ER intrabodies so far have been (i) inactivation of oncogenic receptors and (ii) functional inhibition of virus envelope proteins and virus-receptor molecules on the surface of host cells.In cancer research, the number of in vivo mouse models for evaluation of the therapeutic potential of intrabodies is increasing.In the future, endosomal localized receptors involved in bacterial and viral infections, intracellular oncogenic receptors and enzymes involved in glycosylation of tumour antigens might be new targets for ER intrabodies.

Gene therapy for ovarian cancer

Ovarian cancer remains the leading cause of death due to gynecologic cancer in women in the United States. Gene and viral-based therapies represent novel therapeutic approaches for cancer. The manipulation of genetic content of tumor cells toward a therapeutic end has been divided into several general strategies, including molecular chemotherapy, mutation compensation, immunopotentiation, and virotherapy. Improvements in delivery vehicles and in evaluation of gene transfer and viral replication remain important areas of investigation. We highlight the most recent advances in these novel therapeutic approaches for ovarian cancer and include a summary of recent clinical trials.

A conditionally replicative, Wnt/beta-catenin pathway-based adenovirus therapy for anaplastic thyroid cancer

Thyroid cancer affects between 10,000 and 15,000 people per year in the US. Typically, this disease can be controlled with surgical resection and radioiodide treatment. However, resistance to these conventional therapies is observed in some patients, who develop intractable anaplastic thyroid cancer (ATC), for which no effective therapies exist. Recently, a sizable fraction of undifferentiated or poorly differentiated thyroid cancers were shown to contain mutations in beta-catenin, an oncogenic protein involved in the etiology of cancers of many tissues. We developed a conditionally replicative adenovirus (named 'HILMI') which, by virtue of TCF response elements drives E1A and E1B expression, replicates specifically in cells with an active Wnt/beta-catenin pathway. We show that several thyroid cancer cell lines, derived from undifferentiated or anaplastic tissues and possessing an active Wnt/beta-catenin pathway, are susceptible to cell killing by HILMI. Furthermore, viral replication in ATC cells as xenograft tumors in nude mice was observed, and prolonged survival of mice with ATC tumors was observed following administration of the HILMI therapeutic vector. The results warrant further development of this therapeutic approach for ATC patients.

Isolation of targeted AAV2 vectors from novel virus display libraries

Random peptide ligands displayed on viral capsids are emerging tools for selection of targeted gene transfer vectors even without prior knowledge of the potential target cell receptor. We have previously introduced adeno-associated viral (AAV)-displayed peptide libraries that ensure encoding of displayed peptides by the packaged AAV genome. A major limitation of these libraries is their contamination with wild-type (wt) AAV. Here we describe a novel and improved library production system that reliably avoids generation of wt AAV by use of a synthetic cap gene. Selection of targeted AAV vectors from wt-containing and the novel wt-free libraries on cell types with different permissivity for wt AAV2 replication suggested the superiority of the wt-free library. However, from both libraries highly specific peptide sequence motifs were selected which improved transduction of cells with moderate or low permissivity for AAV2 replication. Strong reduction of HeLa cell transduction compared to wt AAV2 and only low level transduction of non-target cells by some selected clones showed that not only the efficiency but also the specificity of gene transfer was improved. In conclusion, our study validates and improves the unique potential of virus display libraries for the development of targeted gene transfer vectors.

Highly efficient and carcinoma-specific adenoviral replication restricted by the EGP-2 promoter

Although some successes have been reported using adenoviral vectors for the treatment of cancer, adenoviral cancer gene therapy is still hampered by the lack of sufficient tumor cell killing. To increase the efficiency, adenoviruses have been modified to replicate specifically in tumor tissues by using tumor specific promoters controlling genes essential for adenoviral replication. However, many conditionally replicating adenoviral vectors replicate in one tumor type only, which limits their application. The epithelial glycoprotein-2 (EGP-2) promoter is active in a broad variety of carcinomas, the most common type of cancer. We utilized this promoter to restrict adenoviral replication. In this report we demonstrate that the potency of the replication-competent adenovirus AdEGP-2-E1 to specifically lyse EGP-2 positive cells is comparable to wild-type adenovirus (AdWT). In addition, we show that in vivo AdEGP-2-E1 replicates as efficient as AdWT in EGP-2 positive tumor cells. On the contrary, in EGP-2 negative cell lines as well as in primary human liver samples, the replication was attenuated up to 4-log in comparison to wild-type virus. This report clearly shows the potency of the EGP-2 promoter to mediate highly efficient and specific adenoviral replication for carcinoma gene therapy.

Cancer-specific targeting of an adenovirus-delivered herpes simplex virus thymidine kinase suicide gene using translational control

Two technical hurdles, gene delivery and target specificity, have hindered the development of effective cancer gene therapies. In order to circumvent the problem of tumor specificity, the suicide gene, HSV-1 thymidine kinase (HSV-Tk), was modified with a complex 5' upstream-untranslated region (5'-UTR) that limits efficient translation to cells expressing high levels of the translation initiation factor, eIF4E. Since previous studies have shown that most tumor cells express elevated levels of eIF4E, tumor-specific gene delivery was optimized by incorporation of the 5'-UTR-modified suicide gene (HSV-UTk) into an adenovirus vector (Ad-CMV-UTk). The efficacy of this novel approach of targeting suicide gene expression and limiting cytotoxicity by means of translational restriction was tested in vitro with the use of the human breast cancer cell lines (MCF-7, MDA-MB435, and ZR-75-1). As controls, normal MCF10A, HMEC, and HMSC cell lines that express relatively low levels of eIF4E were used. Real-time reverse-transcription polymerase chain reaction (RT-PCR) was used to quantify HSV-Tk mRNA for cells infected with Ad-CMV-UTk as well as with Ad-CMV-Tk (a control adenovirus in which HSV-Tk is not regulated at the level of translation). Translation of HSV-Tk in the Ad-infected cells was measured by Western blot analysis. In addition, cytotoxicity was determined following treatment with the pro-drug ganciclovir (GCV) using an MTT viability assay. Finally, microPET imaging was used to assess cancer cell-specific expression of HSV-Tk and expression in normal tissues in vivo after intraperitoneal injection of Ad-CMV-Tk or Ad-CMV-UTk. These data collectively showed enhanced cancer cell-specific gene expression and reduced normal tissue gene expression for the Ad-HSV-UTk compared to the Ad-CMV-Tk, leading to increased cancer cell-enhanced GCV cytotoxicity. These results indicate that translational targeting of suicide gene expression in tumor cells in vitro and in vivo is effective and may provide a platform for enhanced cancer gene therapy specificity.

Targeted and shielded adenovectors for cancer therapy

Conditionally replicative adenovirus (CRAd) vectors are novel vectors with utility as virotherapy agents for alternative cancer therapies. These vectors have already established a broad safety record in humans and overcome some of the limitations of non-replicative adenovirus (Ad) vectors. In addition, one potential problem with these vectors, attainment of tumor or tissue selectivity has widely been addressed. However, two confounding problems limiting efficacy of these drug candidates remains. The paucity of the native Ad receptor on tumor tissues, and host humoral response due to pre-existing titers of neutralizing antibodies against the vector itself in humans have been highlighted in the clinical context. The well-characterized CRAd, AdDelta24-RGD, is infectivity enhanced, thus overcoming the lack of coxsackievirus and adenovirus receptor (CAR), and this agent is already rapidly progressing towards clinical translation. However, the perceived host humoral response potentially will limit gains seen from the infectivity enhancement and therefore a strategy to blunt immunity against the vector is required. On the basis of this caveat a novel strategy, termed shielding, has been developed in which the genetic modification of a virion capsid protein would provide uniformly shielded Ad vectors. The identification of the pIX capsid protein as an ideal locale for genetic incorporation of shielding ligands to conceal the Ad vector from pre-existing neutralizing antibodies is a major progression in the development of shielded CRAds. Preliminary data utilizing an Ad vector with HSV-TK fused to the pIX protein indicates that a shield against neutralizing antibodies can be achieved. The utility of various proteins as shielding molecules is currently being addressed. The creation of AdDelta24S-RGD, an infectivity enhanced and shielded Ad vector will provide the next step in the development of clinically and commercially feasible CRAds that can be dosed multiple times for maximum effectiveness in the fight against cancers in humans.

Efficient gene transfer into hematopoietic cells by a retargeting adenoviral vector system with a chimeric fiber of adenovirus serotype 5 and 11p

OBJECTIVE

Adenoviral vectors (Ad) were widely used in gene therapy and study of gene function, but the commonly used serotype 5 adenovirus-based vectors (Ad5) could poorly transduce hematopoietic cells because of low expression of viral receptors on these cells. To overcome this limitation, we developed a retargeting adenovector with a chimeric fiber of Ad5 and Ad11p (Ad5F11p) and evaluated its gene transfer ability in hematopoietic cells.

MATERIALS AND METHODS

An Ad11p fiber pseudotyped Ad5 vector was generated by modifying the fiber gene of pAdEasy-1 backbone plasmid. Ad5F11p-GFP encoding enhanced green fluorescence protein (GFP) gene was transferred into human leukemic cell lines, primary leukemic cells, and CD34(+) hematopoietic cells. The gene transduction efficiency was determined by fluorescence-activated cell sorting assay.

RESULTS

More than 90% of U937 or K562 cells could be infected by Ad5F11p-GFP at a moderate multiplicity of infection (MOI). Ad5F11p-GFP is also significantly more effective than control Ad5-GFP in infection of primary myeloid leukemic cells. At 200 MOI, GFP-positive percentages of Ad5F11p-GFP transduced myeloid leukemic cells range from 10.58% to 92.63% with a median of 28.65%. Ad5F11p-GFP could transduce about 50% human hematopoietic stem/progenitor (CD34(+)) cells, while Ad5-GFP could transduce <15% at 200 MOI. CD46 was reported to be the receptor of Ad11p. Our data suggest that CD46 participates in the process of Ad5F11p-GFP infection but is not the unique molecule determining its gene transfer efficiency of host cells.

CONCLUSION

We established a retargeting adenovector system, which could infect hematopoietic cells effectively and would benefit research work on Ad tropism.

The carcinoma-specific epithelial glycoprotein-2 promoter controls efficient and selective gene expression in an adenoviral context

Adenoviral vectors are widely used in cancer gene therapy. After systemic administration however, the majority of the virus homes to the liver and the expressed transgene may cause hepatotoxicity. To restrict transgene expression to tumor cells, tumor- or tissue-specific promoters are utilized. The tumor antigen epithelial glycoprotein-2 (EGP-2), also known as Ep-CAM, is expressed in many cancers from different epithelial origins. In this study, the EGP-2 promoter was shown to restrict the expression of luciferase and thymidine kinase in an adenoviral context in different cell lines. In vivo, the EGP-2 promoter mediated efficient expression of luciferase in tumors but showed a 3-log lower activity in liver tissue when compared with the cytomegalovirus (CMV) promoter. Similarly, the EGP-2 promoter mediated specific cell killing after ganciclovir treatment in EGP-2-positive cells. Moreover, in vivo, this treatment regiment did not cause any rise in the liver enzymes aspartate aminotransferase (ASAT) and alanine aminotransferase (ALAT), demonstrating absence of liver toxicity. In contrast, CMV-mediated expression of thymidine kinase in combination with ganciclovir treatment resulted in high ASAT and ALAT values. This study demonstrates the value of the EGP-2 promoter to restrict transgene expression to a broad range of tumor types, thereby preventing liver toxicity.

A heparan sulfate-targeted conditionally replicative adenovirus, Ad5.pk7-Delta24, for the treatment of advanced breast cancer

Conditionally replicating adenoviruses (CRAds) that replicate in tumor but less in normal cells are promising anticancer agents. A major determinant of their potency is their capacity for infecting target cells. The primary receptor for serotype 5 adenovirus (Ad5), the most widely used serotype in gene therapy, is the coxsackie-adenovirus receptor (CAR). CAR is expressed variably and often at low levels in various tumor types including advanced breast cancer. We generated a novel p16/retinoblastoma pathway-dependent CRAd, Ad5.pK7-Delta24, with a polylysine motif in the fiber C-terminus, enabling CAR-independent binding to heparan sulfate proteoglycans (HSPG). Ad5.pK7-Delta24 mediated effective oncolysis of all breast cancer cell lines tested. Further, we utilized noninvasive, fluorescent imaging for analysis of antitumor efficacy in an orthotopic model of advanced hormone refractory breast cancer. A therapeutic benefit was seen following both intratumoral and intravenous delivery. Murine biodistribution similar to Ad5, proven safe in trials, suggests feasibility of clinical safety testing. Interestingly, upregulation of CAR was seen in low-CAR M4A4-LM3 breast cancer cells in vivo, which resulted in better than expected efficacy also with an isogenic CRAd with an unmodified capsid. These results suggest utility of Ad5.pK7-Delta24 and the orthotopic model for further translational studies.

Triple-Targeted Oncolytic Adenoviruses Featuring the Cox2 Promoter, E1A Transcomplementation, and Serotype Chimerism for Enhanced Selectivity for Ovarian Cancer Cells

Conditionally replicating adenoviruses (CRAd's) feature selective replication in and killing of tumor cells. Initial clinical studies with relatively attenuated early generation agents have resulted in promising safety and efficacy data. Nevertheless, increased specificity may be advantageous for an emerging generation of infectivity-enhanced CRAd's. Further, increased specificity could translate into a larger tolerated dose. An approach for increasing specificity is dual control of E1A expression. We constructed six CRAd's featuring two variants of the cyclo-oxygenase 2 (cox2) promoter, combined with three versions of E1A. Transcriptional targeting was supplemented with transductional targeting utilizing the serotype 3 knob. In vivo and in vitro results suggest that cox2 can be utilized for enhancing the specificity of E1A deletion mutants and that combination with the Delta24 mutation increases specificity without reducing potency. Combination with Delta2-Delta24 was specific but somewhat attenuated. The promoter variants behaved similarly, although the longer 1,554-bp version displayed a trend for improved specificity. Transcriptional modifications were compatible with transductional targeting and resulted in up to 100,000-fold increase in the therapeutic window for Ad5/3cox2Ld24 vs wild-type adenovirus. Thus, the proposed triple-targeting strategy may be useful for increasing the safety and efficacy of adenoviral gene therapy for ovarian cancer.

Effective treatment of pancreatic cancer xenografts with a conditionally replicating virus derived from type 2 herpes simplex virus

PURPOSE

Pancreatic cancer is a devastating disease that is almost universally fatal because of the lack of effective treatments. We recently constructed a novel oncolytic virus (FusOn-H2) from the type 2 herpes simplex virus. Because the replication potential of FusOn-H2 depends on the activation of the Ras signaling pathway, we evaluated its antitumor effect against pancreatic cancer, which often harbors K-ras gene mutations.

EXPERIMENTAL DESIGN

Human pancreatic cancer xenografts were established in nude mice either s.c. or orthotopically (n = 8/group). FusOn-H2 was injected either directly (s.c. tumors) or by the i.v. or i.p. route (orthotopic tumors). Tumor volume, weight, and survival time were recorded for each animal. Statistical analyses were done by Student's t test.

RESULTS

A single intratumor injection of FusOn-H2 completely eradicated s.c. pancreatic cancers in all animals. Systemic injection of the oncolytic virus produced clear antitumor effects but did not abolish tumors in any animal. The most striking antitumor effect was seen when the virus was given i.p. Delivery of FusOn-H2 by this route completely eradicated established orthotopic tumors in 75% of the animals and completely prevented local metastases.

CONCLUSIONS

FusOn-H2 has potent activity against human pancreatic cancer xenografts and may be a promising candidate for investigative virotherapy of this malignancy.

Adenovirus: from foe to friend

Human adenoviruses (HAdVs) can cause mild respiratory, gastrointestinal, urogenital and ocular disease. Knowledge about HAdVs has been expanding for more than five decades putting them amongst the most-studied viruses. This continued interest stems, to a great extent, from the fact that these double-stranded DNA viruses have proven to be a versatile tool to probe the basic phenomena of eukaryotic cells. HAdV research has led to the discovery of, for instance, RNA splicing and greatly contributed to our knowledge of processes as fundamental as replication, transcription and translation. Moreover, the transformation of rodent cells by HAdVs has provided a system to unravel the molecular pathways that control cell proliferation. As a result, the genetic organisation of these agents is known in great detail allowing the straightforward manipulation of their genomes. In addition, the virus itself became renowned for its ability to produce large amounts of progeny and to efficiently infect mammalian cells regardless of their cell cycle status. These features contributed to the broad use of recombinant HAdVs as gene carriers particularly in in vivo settings where the vast majority of target cells are post-mitotic. The most advanced type of HAdV vectors can accommodate up to 37 kb of foreign DNA and are devoid of viral genes. With the aid of these high-capacity HAdV vectors large physiologically responsive transcriptional elements and/or genes can be efficiently introduced into target cells while minimising adaptive immune responses against the transduced cells. This article provides information on HAdV especially on the aspects pertinent to the design, production and performance of its recombinant forms. The development and characteristics of the main HAdV-based vector types are also briefly reviewed.

Transgenic mouse for conditional, tissue-specific Cox-2 overexpression

We constructed a cyclooxygenase-2 (Cox-2) conditional overexpression transgenic mouse (Cox-2 COE). The transgene contains a CAG promoter driving the Cox-2 and humanized Renilla luciferase (hRL) coding regions, linked by an internal ribosomal entry site. The promoter is followed by a loxP-flanked sequence containing enhanced green fluorescent protein (EGFP), a neomycin selection cassette, and a transcriptional/translational STOP sequence. In the presence of Cre recombinase the loxP-flanked sequence is excised. Cox-2/hRL expression can be monitored repeatedly and noninvasively in vivo by imaging hRL activity. To demonstrate conditional Cox-2 and hRL expression, a nonreplicating adenovirus carrying Cre recombinase (Ad.CMV.Cre) was injected intravenously; hepatic Cox-2 expression and hRL signal were elevated. Cox-2 COE embryonic fibroblasts express both Cox-2 and hRL following Ad.CMV.Cre infection. PGE(2) production is also increased following Ad.CMV.Cre infection of Cox-2 COE embryo fibroblasts. Cox-2 COE mice should be valuable for the study of Cox-2 overexpression in cardiovascular disease, acute and chronic inflammatory responses, neurodegenerative diseases, and cancer.

Gene therapy and uterine leiomyoma: a review

Leiomyomas (fibroids) are common estrogen-dependent uterine tumours that cause significant morbidity for women and a substantial economic impact on health delivery systems. Currently, there is no effective medical treatment option for this condition-hysterectomy is the mainstay of management. This is not an attractive choice for many women, especially patients desiring to preserve their fertility potential. Gene therapy is becoming a clinical reality, with more than 600 clinical trials worldwide. Researchers have recently attempted to develop a gene-therapy-based approach for the ablation of uterine fibroids. The localized nature of this condition and its accessibility using different imaging or endoscopic techniques make it an attractive target for direct delivery of gene-based vectors. Recent work from our laboratory suggests the potential use of a dominant-negative form of estrogen receptor (ER) to inactivate estrogen signalling in leiomyoma cells and induce apoptosis. Our in vivo data in a mouse model demonstrate the ability of an adenovirus-expressing dominant-negative ER to arrest leiomyoma growth. We and others also have described the utility of the herpes simplex virus-thymidine kinase (HSV-TK) plus ganciclovir (GCV) suicide gene-therapy system to effectively eradicate leiomyoma cells by utilizing the bystandard effect phenomena and the high expression of gap-junction protein in these tumours. Further work on rat models will pave the way for future leiomyoma gene-therapy clinical trials and allow the realization of gene therapy as a viable non-surgical option for this common problem in women's health.

Adenovirus type 5 interactions with human blood cells may compromise systemic delivery

Intravenous delivery of adenovirus vectors requires that the virus is not inactivated in the bloodstream. Serum neutralizing activity is well documented, but we show here that type 5 adenovirus also interacts with human blood cells. Over 90% of a typical virus dose binds to human (but not murine) erythrocytes ex vivo, and samples from a patient administered adenovirus in a clinical trial showed that over 98% of viral DNA in the blood was cell associated. In contrast, nearly all viral genomes in the murine bloodstream are free in the plasma. Adenovirus bound to human blood cells fails to infect A549 lung carcinoma cells, although dilution to below 1.7 x 10(7) blood cells/ml relieves this inhibition. Addition of blood cells can prevent infection by adenovirus that has been prebound to A549 cells. Adenovirus also associates with human neutrophils and monocytes ex vivo, particularly in the presence of autologous plasma, giving dose-dependent transgene expression in CD14-positive monocytes. Finally, although plasma with a high neutralizing titer (defined on A549 cells) inhibits monocyte infection, weakly neutralizing plasma can actually enhance monocyte transduction. This may increase antigen presentation following intravenous injection, while blood cell binding may both decrease access of the virus to extravascular targets and inhibit infection of cells to which the virus does gain access.

Ovarian cancer targeted adenoviral-mediated mda-7/IL-24 gene therapy

OBJECTIVE

We have previously shown that adenoviral-mediated melanoma differentiation-associated gene-7 (Ad.mda-7) therapy induces apoptosis in ovarian cancer cells. However, the apoptosis induction was low and directly correlated with infectivity of Ad.mda-7. The objective of this study was to derive ovarian cancer targeted infectivity-enhanced adenoviral vectors encoding mda-7 and evaluate their enhancement in therapeutic efficacy for ovarian carcinoma.

METHODS

Infectivity-enhanced adenoviral vectors encoding mda-7 Ad.RGD.mda-7 and Ad.RGD.pK7.mda-7 were derived by incorporation of RGD and or RGD and Pk7 motifs in the fiber knobs by genetic modification. Viruses were validated by PCR for presence of mda-7 and by Western blot for expression of MDA-7 protein. To test the enhancement of therapeutic efficacy of these viruses, a panel of human ovarian carcinoma cells, OV-4, HEY, SKOV3, SKOV3.ip1, were infected by either Ad.mda-7 or Ad.RGD.mda-7 and Ad.RGD.pK7.mda-7 or their respective control viruses and the cell killing was evaluated by crystal violet staining in vitro. Further, therapeutic efficacy was evaluated in vivo using human ovarian cancer xenograft mouse models.

RESULTS

Both Ad.RGD.pK7.mda-7 and Ad.RGD.mda-7 showed significant increase in cell killing in vitro compared to unmodified Ad.mda-7 with Ad.RGD.pK7.mda-7 showing highest cell killing. Further, Ad.RGD.pK7.mda-7 showed a significant increase in survival of mice bearing human ovarian cancer xenografts compared to Ad.mda-7 and other control groups.

CONCLUSION

Infectivity-enhanced Ad.RGD.mda-7 and Ad.RGD.pK7.mda-7 viruses significantly enhanced ovarian cancer tumor cell killing in vitro. Significant prolongation of survival by Ad.RGD.pK7.mda-7 in murine ovarian cancer models demonstrates the high clinical translational potential of these viruses for ovarian cancer therapy.

Dynamic monitoring of oncolytic adenovirus in vivo by genetic capsid labeling

BACKGROUND

Conditionally replicative adenoviruses represent a promising strategy to address the limited efficacy and safety issues associated with conventional cancer treatment. Despite rapid translation into human clinical trials and demonstrated safety, the fundamental properties of oncolytic adenovirus replication and spread and host-vector interactions in vivo have not been completely evaluated.

METHODS

We developed a noninvasive dynamic monitoring system to detect adenovirus replication. We constructed capsid-labeled E1/E3-deleted and wild-type adenoviruses (Ad-wt) by fusing the minor capsid protein IX with red fluorescent proteins mRFP1 and tdimer2(12), resulting in Ad-IX-mRFP1, Ad-IX-tdimer2(12), and Ad-wt-IX-mRFP1. Virus DNA replication, encapsidation, cytopathic effect, thermostability, and binding to primary receptor (coxsackie adenovirus receptor) were analyzed using real-time quantitative polymerase chain reaction, cell viability (MTS) assay, and fluorescence microscopy. Athymic mice (n = 4) carrying xenograft tumors that were derived from A549 lung adenocarcinoma cells were intratumorally inoculated with Ad-wt-IX-mRFP1, and adenovirus replication was dynamically monitored with a fluorescence noninvasive imaging system. Correlations between fluorescence signal intensity and viral DNA synthesis and replication were calculated using Pearson's correlation coefficient (r).

RESULTS

The red fluorescence label had little effect on viral DNA replication, encapsidation, cytopathic effect, thermostability, and coxsackie adenovirus receptor binding. The fluorescent signal correlated with viral DNA synthesis and infectious progeny production both in vitro and in vivo (in A549 cells, r = .99 and r = .65; in tumors, r = .93 and r = .92, respectively). The replication efficiency of Ad-wt-IX-mRFP1 in vivo was variable, and replication and viral spreading and persistence were limited, consistent with clinical observations.

CONCLUSIONS

Genetic capsid labeling provides a promising approach for the dynamic assessment of oncolytic adenovirus function in vivo.

Production and formulation of adenovirus vectors

Adenovirus vectors have attracted considerable interest over the past decade, with ongoing clinical development programs for applications ranging from replacement therapy for protein deficiencies to cancer therapeutics to prophylactic vaccines. Consequently, considerable product, process, analytical, and formulation development has been undertaken to support these programs. For example, "gutless" vectors have been developed in order to improve gene transfer capacity and durability of expression; new cell lines have been developed to minimize recombination events; production conditions have been optimized to improve volumetric productivities; analytical techniques and scaleable purification processes have advanced towards the goal of purified adenovirus becoming a "well-characterized biological"; and liquid formulations have been developed which maintain virus infectivity at 2-8 degrees C for over 18 months. These and other advances in the production of adenovirus vectors are discussed in detail in this review. In addition, the needs for the next decade are highlighted.

Viral-based modelling and correction of neurodegenerative diseases by RNA interference

Experimental recapitulation of recessive human genetic neurodegenerative disease in rodents can be classically addressed through genetic disruption of the related gene. Although very informative, this specific gene targeting is restricted to mice and precludes a species scale-up towards non-human primates. Concomitantly, this requirement to silence a specific gene in a broad range of animal models is important in the design of therapeutic approaches to dominantly inherited neurodegenerative diseases. The emergence of RNA interference (RNAi), a highly specific mechanism of post-translational gene silencing, has opened a plethora of biological application ranging from reverse genetic analysis to therapeutic schemes. Recombinant viral vectors, by promoting a long-lasting delivery of genetic instructions in a broad range of cellular types of different species origins, represent potential platforms mandating silencing of specific gene products through RNAi. This review aims at providing an overview of the different viral systems engineered so far for efficient in vitro and in vivo delivery of RNAi instructions. Additionally, the potential of RNAi for functional analysis and therapy for polyglutamine disorders or amyotrophic lateral sclerosis is discussed.

Selective induction of tumor-associated antigens in murine pulmonary vasculature using double-targeted adenoviral vectors

Targeted therapies directed to tumor-associated antigens are being investigated for the treatment of cancer. However, there are few suitable animal models for testing the ability to target these tumor markers. Therefore, we have exploited mice transgenic for the human coxsackie and adenovirus receptor (hCAR) to establish a new model for transient expression of human tumor-associated antigens in the pulmonary vasculature. Systemic administration of Ad in hCAR mice resulted in an increase in transgene expression in the lungs compared to wild-type mice, as determined using a luciferase reporter gene. To reduce transgene expression in the liver, the predominant organ of ectopic Ad localization and transgene expression following systemic administration, we utilized the endothelial-specific flt-1 promoter, which resulted in a further increased lung-to-liver ratio of luciferase expression. Administration of an adenoviral vector encoding the tumor-associated antigen carcinoembryonic antigen (CEA) under transcriptional control of the flt-1 promoter resulted in selective expression of this antigen in the pulmonary vasculature of hCAR mice. Feasibility of targeting to expressed CEA was subsequently demonstrated using adenoviral vectors preincubated with a bifunctional adapter molecule recognizing this tumor-associated antigen, thus demonstrating utility of this transient transgenic animal model.