An adenovirus with enhanced infectivity mediates molecular chemotherapy of ovarian cancer cells and allows imaging of gene expression

In vitro functional genetic modification of canine adenovirus type 2 genome by CRISPR/Cas9

Genetically modified oncolytic adenoviruses have been proposed as a vehicle for cancer therapy. However, several concerns, such as toxicity to normal cells and organs, lack of suitable cell surface receptors to allow viral entry to the desired cell type(s), and activation of both innate and adaptive immune systems in patients, restrict the successful clinical application of adenoviral-mediated cancer gene therapy. Successful virotherapy will require efficient transductional and transcriptional targeting to enhance therapeutic efficacy by ensuring targeted adenoviral infection, replication, and/or therapeutic transgene expression. Targeted modification of viral components, such as viral capsid, fiber knob, and the insertion of transgenes for expression, are prerequisites for the necessary transductional and transcriptional targeting of adenovirus. However, the conventional approach to modify the adenoviral genome is complex, time consuming, and expensive. It is dependent on the presence of unique restriction enzyme sites that may or may not be present in the target location. Clustered regularly interspaced short palindromic repeat (CRISPR) along with the RNA-guided nuclease Cas9 (CRISPR/Cas9) is one of the most powerful tools that has been adopted for precise genome editing in a variety of cells and organisms. However, the ability of the CRISPR/Cas9 system to precisely and efficiently make genetic modification, as well as introduce gene replacements, in adenoviral genomes, remains essentially unknown. Herein the ability of in vitro CRISPR/CAS9-mediated editing of the canine adenovirus type 2 (CAV2) genome to promote targeted modification of the viral genome was assessed. To demonstrate the feasibility of this goal, CRISPR/Cas9 has been used to successfully insert the RFP (red fluorescent protein) reporter construct into the CAV2 genome. Initial results demonstrated high efficiency and accuracy for in vitro CRISPR-mediated editing of the large CAV2 genome. Furthermore, this application was expanded, using multiple guide RNAs, to conduct gene replacement in the CAV2 genome by substituting a portion of the E3 gene with a construct designed to express a single chain antibody to canine PD-1. Thus, this work provides a significantly improved and efficient method for targeted editing of adenoviruses to generate altered and potentially therapeutic viral genomes in the shortest possible time.

Bacteriophage-mediated therapy of chondrosarcoma by selective delivery of the tumor necrosis factor alpha (TNFα) gene

Chondrosarcoma is a cartilage-forming bone tumor, well known for intrinsic resistance to chemotherapy and radiotherapy. We have designed a targeted chondrosarcoma gene therapy using a bacteriophage (phage) particle to deliver therapeutic genes. Phage has no tropism for mammalian cells, allowing engineered phage to be targeted to specific cell surface receptors in cancer. We modified the phage capsid to display the RGD4C ligand on the pIII minor coat proteins to specifically bind to αvβ3 or αvβ5 integrin receptors. The endosomal escape peptide, H5WYG, was also displayed on recombinant pVIII major coat proteins to enhance gene delivery. Finally, a human tumor necrosis factor alpha (TNFα) therapeutic transgene expression cassette was incorporated into the phage genome. First, we found that human chondrosarcoma cells (SW1353) have high expression of αvβ3, αvβ5 integrin receptors, and both TNFα receptors. Targeted particle encoding a luciferase reporter gene efficiently and selectively mediated gene delivery to these cells. When SW1353 cells were treated with the targeted particle encoding a TNFα transgene, significant cell killing was evident and was associated with high expression of TNFα and apoptosis-related genes. In vivo, mice with established human chondrosarcoma showed suppression of tumors upon repetitive intravenous administrations of the targeted phage. These data show that our phage-based particle is a promising, selective, and efficient tool for targeted chondrosarcoma therapy.

Understanding and addressing barriers to successful adenovirus-based virotherapy for ovarian cancer

Ovarian cancer is the leading cause of death among women with gynecological cancer, with an overall 5-year survival rate below 50% due to a lack of specific symptoms, late stage at time of diagnosis and a high rate of recurrence after standard therapy. A better understanding of heterogeneity, genetic mutations, biological behavior and immunosuppression in the tumor microenvironment have allowed the development of more effective therapies based on anti-angiogenic treatments, PARP and immune checkpoint inhibitors, adoptive cell therapies and oncolytic vectors. Oncolytic adenoviruses are commonly used platforms in cancer gene therapy that selectively replicate in tumor cells and at the same time are able to stimulate the immune system. In addition, they can be genetically modified to enhance their potency and overcome physical and immunological barriers. In this review we highlight the challenges of adenovirus-based oncolytic therapies targeting ovarian cancer and outline recent advances to improve their potential in combination with immunotherapies.

The Continuing Evolution of Molecular Functional Imaging in Clinical Oncology: The Road to Precision Medicine and Radiogenomics (Part I)

The present era of precision medicine sees 'cancer' as a consequence of molecular derangements occurring at the commencement of the disease process, with morphologic changes happening much later in the process of tumorigenesis. Conventional imaging techniques, such as computed tomography (CT), ultrasound, and magnetic resonance imaging (MRI), play an integral role in the detection of disease at a macroscopic level. However, molecular functional imaging (MFI) techniques entail the visualisation and quantification of biochemical and physiological processes occurring during tumorigenesis, and thus has the potential to play a key role in heralding the transition from the concept of 'one size fits all' to 'precision medicine'. Integration of MFI with other fields of tumour biology such as genomics has spawned a novel concept called 'radiogenomics', which could serve as an indispensable tool in translational cancer research. With recent advances in medical image processing, such as texture analysis, deep learning, and artificial intelligence (AI), the future seems promising; however, their clinical utility remains unproven at present. Despite the emergence of novel imaging biomarkers, a majority of these require validation before clinical translation is possible. In this two-part review, we discuss the systematic collaboration across structural, anatomical, and molecular imaging techniques that constitute MFI. Part I reviews positron emission tomography, radiogenomics, AI, and optical imaging, while part II reviews MRI, CT and ultrasound, their current status, and recent advances in the field of precision oncology.

Application of interferon modulators to overcome partial resistance of human ovarian cancers to VSV-GP oncolytic viral therapy

Previously, we described an oncolytic vesicular stomatitis virus variant pseudotyped with the nonneurotropic glycoprotein of the lymphocytic choriomeningitis virus, VSV-GP, which was highly effective in glioblastoma. Here, we tested its potency for the treatment of ovarian cancer, a leading cause of death from gynecological malignancies. Effective oncolytic activity of VSV-GP could be demonstrated in ovarian cancer cell lines and xenografts in mice; however, remission was temporary in most mice. Analysis of the innate immune response revealed that ovarian cancer cell lines were able to respond to and produce type I interferon, inducing an antiviral state upon virus infection. This is in stark contrast to published data for other cancer cell lines, which were mostly found to be interferon incompetent. We showed that in vitro this antiviral state could be reverted by combining VSV-GP with the JAK1/2-inhibitor ruxolitinib. In addition, for the first time, we report the in vivo enhancement of oncolytic virus treatment by ruxolitinib, both in subcutaneous as well as in orthotopic xenograft mouse models, without causing significant additional toxicity. In conclusion, VSV-GP has the potential to be a potent and safe oncolytic virus to treat ovarian cancer, especially when combined with an inhibitor of the interferon response.

Magnetic nanoparticles as a new approach to improve the efficacy of gene therapy against differentiated human uterine fibroid cells and tumor-initiating stem cells

OBJECTIVE

To study whether efficient transduction and subsequent elimination of fibroid tumor-initiating stem cells during debulking of tumor cells will aid in completely eradicating the tumor as well as decreasing the likelihood of recurrence.

DESIGN

Case control study.

SETTING

Research laboratory.

PATIENT(S)

None.

INTERVENTION(S)

Magnetic nanoparticles (MNPs) complexed to adenovirus (Ad-GFP) or (Ad-LacZ) used to transfect differentiated human fibroid cells in vitro.

MAIN OUTCOME MEASURE(S)

Rate of transduction and tumor growth inhibition.

RESULT(S)

We have developed a localized nonsurgical adenovirus-based alternative for the treatment of uterine fibroids that combines viral-based gene delivery with nanotechnology for more efficient targeting. Magnetic nanoparticles complexed to adenovirus, in the presence of an external magnetic field, accelerate adenovirus transduction. We observed a statistically significant increase in transduction efficiency among differentiated human fibroid cells at two different multiplicities of infection (MOI), 1 and 10, respectively, with MNPs as compared with adenovirus alone. Human fibroid stem cells transfected with Ad-LacZ expressed β-galactosidaze at a MOI of 1, 10, and 50 at 19%, 62%, and 90%, respectively, which were statistically significantly enhanced with MNPs.

CONCLUSION(S)

When applied with adenovirus herpes simplex thymidine kinase, magnetofection statistically significantly suppressed proliferation and induced apoptosis in both cell types. Through the use of magnetofection, we will prove that a lower viral dose will effectively increase the overall safety profile of suicide gene therapy against fibroid tumors.

Targeted Adenoviral Vector Demonstrates Enhanced Efficacy for In Vivo Gene Therapy of Uterine Leiomyoma

BACKGROUND

Gene therapy is a potentially effective non-surgical approach for the treatment of uterine leiomyoma. We demonstrated that targeted adenovirus vector, Ad-SSTR-RGD-TK/GCV, was highly effective in selectively inducing apoptosis and inhibiting proliferation of human leiomyoma cells in vitro while sparing normal myometrial cells.

STUDY DESIGN

An in-vivo study, to compare efficacy and safety of modified adenovirus vector Ad-SSTR-RGD-TK/GCV versus untargeted vector for treatment of leiomyoma.

MATERIALS AND METHODS

Female nude mice were implanted with rat leiomyoma cells subcutaneously. Then mice were randomized into three groups. Group 1 received Ad-LacZ (marker gene), Group 2 received untargeted Ad-TK, and Group 3 received the targeted Ad-SSTR-RGD-TK. Tumors were measured weekly for 4 weeks. Then mice were sacrificed and tissue samples were collected. Evaluation of markers of apoptosis, proliferation, extracellular matrix, and angiogenesis was performed using Western Blot & Immunohistochemistry. Statistical analysis was done using ANOVA. Dissemination of adenovirus was assessed by PCR.

RESULTS

In comparison with the untargeted vector, the targeted adenoviral vector significantly shrank leiomyoma size (P < 0.05), reduced expression of proliferation marker (PCNA) (P < 0.05), induced expression of apoptotic protein, c-PARP-1, (P < 0.05) and inhibited expression of extracellular matrix-related genes (TGF beta 3) and angiogenesis-related genes (VEGF & IGF-1) (P < 0.01). There were no detectable adenovirus in tested tissues other than leiomyoma lesions with both targeted and untargeted adenovirus.

CONCLUSION

Targeted adenovirus, effectively reduces tumor size in leiomyoma without dissemination to other organs. Further evaluation of this localized targeted strategy for gene therapy is needed in appropriate preclinical humanoid animal models in preparation for a future pilot human trial.

Somatostatin receptor based imaging and radionuclide therapy

Somatostatin (SST) receptors (SSTRs) belong to the typical 7-transmembrane domain family of G-protein-coupled receptors. Five distinct subtypes (termed SSTR1-5) have been identified, with SSTR2 showing the highest affinity for natural SST and synthetic SST analogs. Most neuroendocrine tumors (NETs) have high expression levels of SSTRs, which opens the possibility for tumor imaging and therapy with radiolabeled SST analogs. A number of tracers have been developed for the diagnosis, staging, and treatment of NETs with impressive results, which facilitates the applications of human SSTR subtype 2 (hSSTr2) reporter gene based imaging and therapy in SSTR negative or weakly positive tumors to provide a novel approach for the management of tumors. The hSSTr2 gene can act as not only a reporter gene for in vivo imaging, but also a therapeutic gene for local radionuclide therapy. Even a second therapeutic gene can be transfected into the same tumor cells together with hSSTr2 reporter gene to obtain a synergistic therapeutic effect. However, additional preclinical and especially translational and clinical researches are needed to confirm the value of hSSTr2 reporter gene based imaging and therapy in tumors.

Disintegrins from snake venoms and their applications in cancer research and therapy

Integrins regulate diverse functions in cancer pathology and in tumor cell development and contribute to important processes such as cell shape, survival, proliferation, transcription, angiogenesis, migration, and invasion. A number of snake venom proteins have the ability to interact with integrins. Among these are the disintegrins, a family of small, non-enzymatic, and cysteine-rich proteins found in the venom of numerous snake families. The venom proteins may have a potential role in terms of novel therapeutic leads for cancer treatment. Disintegrin can target specific integrins and as such it is conceivable that they could interfere in important processes involved in carcinogenesis, tumor growth, invasion and migration. Herein we present a survey of studies involving the use of snake venom disintegrins for cancer detection and treatment. The aim of this review is to highlight the relationship of integrins with cancer and to present examples as to how certain disintegrins can detect and affect biological processes related to cancer. This in turn will illustrate the great potential of these molecules for cancer research. Furthermore, we also outline several new approaches being created to address problems commonly associated with the clinical application of peptide-based drugs such as instability, immunogenicity, and availability.

Targeting adenoviral vectors for enhanced gene therapy of uterine leiomyomas

STUDY QUESTION

Is targeted adenovirus vector, Ad-SSTR-RGD-TK (Adenovirus -human somatostatin receptor subtype 2- arginine, glycine and aspartate-thymidine kinase), given in combination with ganciclovir (GCV) against immortalized human leiomyoma cells (HuLM) a potential therapy for uterine fibroids?

SUMMARY ANSWER

Ad-SSTR-RGD-TK/GCV, a targeted adenovirus, effectively reduces cell growth in HuLM cells and to a significantly greater extent than in human uterine smooth muscle cells (UtSM).

WHAT IS KNOWN ALREADY

Uterine fibroids (leiomyomas), a major cause of morbidity and the most common indication for hysterectomy in premenopausal women, are well-defined tumors, making gene therapy a suitable and potentially effective non-surgical approach for treatment. Transduction of uterine fibroid cells with adenoviral vectors such as Ad-TK/GCV (herpes simplex virus thymidine kinase gene) decreases cell proliferation.

STUDY DESIGN, SIZE, DURATION

An in vitro cell culture method was set up to compare and test the efficacy of a modified adenovirus vector with different multiplicities of infection in two human immortalized cell lines for 5 days.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Immortalized human leiomyoma cells and human uterine smooth muscle cells were infected with different multiplicities of infection (MOI) (5-100 plaque-forming units (pfu)/cell) of a modified Ad-SSTR-RGD-TK vector and subsequently treated with GCV. For comparison, HuLM and UtSM cells were transfected with Ad-TK/GCV and Ad-LacZ/GCV. Cell proliferation was measured using the CyQuant assay in both cell types. Additionally, western blotting was used to assess the expression of proteins responsible for regulating proliferation and apoptosis in the cells.

MAIN RESULTS AND THE ROLE OF CHANCE

Transduction of HuLM cells with Ad-SSTR-RGD-TK/GCV at 5, 10, 50 and 100 pfu/cell decreased cell proliferation by 28, 33, 45, and 84%, respectively (P < 0.05) compared with untransfected cells, whereas cell proliferation in UtSM cells transfected with the same four MOIs of Ad-SSTR-RGD-TK/GCV compared with that of untransfected cells was decreased only by 8, 23, 25, and 28%, respectively (P < 0.01). Western blot analysis showed that, in comparison with the untargeted vector Ad-TK, Ad-SSTR-RGD-TK/GCV more effectively reduced expression of proteins that regulate the cell cycle (Cyclin D1) and proliferation (PCNA, Proliferating Cell Nuclear Antigen), and it induced expression of the apoptotic protein BAX, in HuLM cells.

LIMITATIONS, REASONS FOR CAUTION

Results from this study need to be replicated in an appropriate animal model before testing this adenoviral vector in a human trial.

WIDER IMPLICATIONS OF THE FINDINGS

Effective targeting of gene therapy to leiomyoma cells enhances its potential as a non-invasive treatment of uterine fibroids.

Chapter two--Adenovirus strategies for tissue-specific targeting

Cancer gene therapy approaches have benefited greatly from the utilization of molecular-based therapeutics. Of these, adenovirus-based interventions hold much promise as a platform for targeted therapeutic delivery to tumors. However, a barrier to this progression is the lack of native adenovirus receptor expression on a variety of cancer types. As such, any adenovirus-based cancer therapy must take into consideration retargeting the vector to nonnative cellular surface receptors. Predicated upon the knowledge gained in native adenovirus biology, several strategies to transductionally retarget adenovirus have emerged. Herein, we describe the biological hurdles as well as strategies utilized in adenovirus transductional targeting, covering the progress of both adapter-based and genetic manipulation-based targeting. Additionally, we discuss recent translation of these targeting strategies into a clinical setting.

A phase I clinical trial of Ad5.SSTR/TK.RGD, a novel infectivity-enhanced bicistronic adenovirus, in patients with recurrent gynecologic cancer

PURPOSE

Ad5.SSTR/TK.RGD is an infectivity-enhanced adenovirus expressing a therapeutic thymidine kinase suicide gene and a somatostatin receptor (SSTR) that allows for noninvasive gene transfer imaging. The purpose of this study was to identify the maximum tolerated dose (MTD), toxicities, clinical efficacy, and biologic effects of Ad5.SSTR/TK.RGD in patients with recurrent gynecologic cancer.

EXPERIMENTAL DESIGN

Eligible patients were treated intraperitoneally for 3 days with 1 × 10(9) to 1 × 10(12) vp/dose of Ad5.SSTR/TK.RGD followed by intravenous ganciclovir for 14 days. Toxicity and clinical efficacy were assessed using Common Toxicity Criteria (CTC) Adverse Events grading and Response Evaluation Criteria in Solid Tumors (RECIST) criteria. Imaging using In-111 pentetreotide was obtained before and after treatment. Tissue samples were obtained to evaluate for gene transfer, generation of wild-type virus, viral shedding, and antibody response.

RESULTS

Twelve patients were treated in three cohorts. The most common vector-related clinical toxicities were grade I/II constitutional or pain symptoms, experienced most often in patients treated at the highest dose. MTD was not identified. Five patients showed stable disease; all others experienced progressive disease. One patient with stable disease experienced complete resolution of disease and normalization of CA125 on further follow-up. Imaging detected increased In-111 pentetreotide retention in patients treated at the highest dose. Ancillary studies showed presence of Ad5.SSTR/TK.RGD virus and HSV1-tk expression in ascites samples collected at various time points in most patients treated within the higher dose cohorts.

CONCLUSIONS

This study shows the safety, potential efficacy, and possible gene transfer imaging capacity of Ad5.SSTR/TK.RGD in patients with recurrent gynecologic cancer. Further development of this novel gene therapeutic appears to be warranted.

Oncolytic Viruses to Treat Ovarian Cancer Patients - a Review of Results From Clinical Trials

Oncolytic viruses are replication competent "live" viruses. They infect tumor cells, replicate highly selective inside and thereby destroy them. Because of the enormous advances in the field of genetic engineering and biotechnology during the last decade, virotherapy is increasingly used within clinical trials and proved to be safe and effective. In particular, treatment of ovarian cancer patients is one main focus of research. On the one hand, this is due to the poor prognosis of this dismal entity, resulting in the urgent need for novel therapeutics. On the other hand, as ovarian cancer typically spreads within the peritoneal cavity, intraperitoneal administration of oncolytic viruses is feasible. This paper provides an overview of promising results from clinical trials to treat ovarian cancer patients with oncolytic viruses.

Adenovirus gene transfer to amelogenesis imperfecta ameloblast-like cells

To explore gene therapy strategies for amelogenesis imperfecta (AI), a human ameloblast-like cell population was established from third molars of an AI-affected patient. These cells were characterized by expression of cytokeratin 14, major enamel proteins and alkaline phosphatase staining. Suboptimal transduction of the ameloblast-like cells by an adenovirus type 5 (Ad5) vector was consistent with lower levels of the coxsackie-and-adenovirus receptor (CAR) on those cells relative to CAR-positive A549 cells. To overcome CAR -deficiency, we evaluated capsid-modified Ad5 vectors with various genetic capsid modifications including “pK7” and/or “RGD” motif-containing short peptides incorporated in the capsid protein fiber as well as fiber chimera with the Ad serotype 3 (Ad3) fiber “knob” domain. All fiber modifications provided an augmented transduction of AI-ameloblasts, revealed following vector dose normalization in A549 cells with a superior effect (up to 404-fold) of pK7/RGD double modification. This robust infectivity enhancement occurred through vector binding to both α_vβ3/α_vβ5 integrins and heparan sulfate proteoglycans (HSPGs) highly expressed by AI-ameloblasts as revealed by gene transfer blocking experiments. This work thus not only pioneers establishment of human AI ameloblast-like cell population as a model for in vitro studies but also reveals an optimal infectivity-enhancement strategy for a potential Ad5 vector-mediated gene therapy for AI.

Oncolytic virotherapy of breast cancer

The use of replication competent viruses that selectively target and destroy cancer cells has rapidly evolved over the past decade and numerous innovative oncolytic viruses have been created. Many of these promising anti-cancer agents have recently entered into clinical trials (including those on breast cancer) and demonstrated encouraging safety and efficacy. Virotherapeutic strategies are thus of considerable interest to combat breast cancer in both (i) the primary disease situation in which relapse should be avoided as good as possible and (ii) in the metastatic situation which remains incurable to date. Here, we summarize data from preclinical and clinical trials using oncolytic virotherapy to treat breast cancer. This includes strategies to specifically target breast cancer cells, to arm oncolytic viruses with additional therapeutic transgenes and an outlining of future challenges when translating these promising therapeutics "from bench to bedside".

Treatment of chemotherapy resistant ovarian cancer with a MDR1 targeted oncolytic adenovirus

OBJECTIVE

Multidrug resistance gene 1 (MDR1) mediated resistance to chemotherapeutic agents is a major obstacle for the therapy of various cancer types. The use of conditionally replicating adenoviruses (CRAds) is dependent on molecular differences between tumor cells and non tumor cells. Transcriptional targeting of CRAd replication is an effective way to control replication regulation. The aim of this study was to evaluate the effect of a MDR1 targeted fiber-modified CRAd against chemotherapy resistant ovarian cancer.

METHODS

MDR1 expression was evaluated in chemotherapy naïve and pretreated ovarian cancer cells and various control cells. We constructed 2 variants of a fiber-modified CRAd, Ad5/3MDR1E1 and Ad5/3MDR1E1∆24 containing the MDR1 promoter to control viral replication via the E1A gene. The MDR promoter activity and cell killing efficacy were evaluated in vitro. Orthotopic murine models of peritoneally disseminated ovarian cancer were utilized to evaluate the preclinical efficacy of MDR targeted CRAds in vivo. To evaluate the liver toxicity of MDR1 targeted CRAds, we compared Ad5/3MDR1E1 with Ad5/3∆24, a CRAd that replicates in cancer cells inactive in the Rb/p16 pathway by use of an in vivo hepatotoxicity model.

RESULTS

We demonstrate efficient oncolysis of Ad5/3MDR1E1 in both chemotherapy resistant ovarian cancer cell lines and in primary tumor cells from pretreated patients as well as therapeutic efficacy in an orthotopic mouse model. Ad5/3MDR1E1 demonstrated significantly decreased liver toxicity compared to other 5/3-fiber modified control vectors examined.

CONCLUSIONS

In summary, Ad5/3MDR1E1 is an efficient and safe gene therapy approach for specific targeting of chemotherapy resistant cancer cells.

SSTR2-based reporters for assessing gene transfer into non-small cell lung cancer: evaluation using an intrathoracic mouse model

The most common cause of cancer-related deaths in North America is lung cancer, 85% of which is non-small cell lung cancer (NSCLC). Gene therapy is a promising approach, but has been hindered by lack of methods for localizing and quantifying gene expression in vivo. Human somatostatin receptor subtype-2 (SSTR2)-based reporters can be used to follow gene expression in vivo using ligands with greater affinity for this subtype. NSCLCs can express SSTR subtypes, which may interfere with SSTR2-based reporters. We assessed whether a SSTR2-based reporter can serve as a reporter of gene transfer into NSCLCs. SSTR subtype expression was assessed in NSCLC cell lines A549, H460, and H1299 using RT-PCR. After infection with an adenovirus containing hemagglutinin-A-tagged-SSTR2 (Ad-HA-SSTR2) or control insert, expression was assessed by immunologic techniques and binding to clinically-approved (111)In-octreotide. In vivo, after magnetic resonance (MR) imaging, intrathoracic H460 tumors were injected with Ad-HA-SSTR2 or control virus (n = 6 mice/group) under ultrasound guidance. Intravenous injection of (111)In-octreotide 2 days later was followed by planar and single-photon emission computed tomography (SPECT) imaging. Biodistribution into tumors was assessed in vivo using anatomic MR and functional gamma-camera images and ex vivo using excised organs/tumors. In human lung tumor samples (n = 70), SSTR2 expression was assessed using immunohistochemistry. All three NSCLC cell lines expressed different SSTR subtypes, but none expressed SSTR2. Upon Ad-HA-SSTR2 infection, HA-SSTR2 expression was seen in all three cell lines using antibodies targeting the HA domain or (111)In-octreotide targeting the receptor domain (p < 0.05). Intrathoracic tumors infected with Ad-HA-SSTR2 were clearly visible by gamma-camera imaging; expression was quantified by both in vivo and ex vivo biodistribution analysis and demonstrated greater uptake in tumors infected with Ad-HA-SSTR2 compared with control virus (p < 0.05). Immunohistochemistry found that 78% of NSCLCs are negative for and 13% have low levels of SSTR2 expression. It is concluded that SSTR2-based reporters can serve as reporters of gene transfer into NSCLCs.

A phase I study of a tropism-modified conditionally replicative adenovirus for recurrent malignant gynecologic diseases

PURPOSE

To determine the maximum tolerated dose (MTD), toxicity spectrum, clinical activity, and biological effects of the tropism-modified, infectivity-enhanced conditionally replicative adenovirus (CRAd), Ad5-Δ24-Arg-Gly-Asp (RGD), in patients with malignant gynecologic diseases.

EXPERIMENTAL DESIGN

Cohorts of eligible patients were treated daily for 3 days through an i.p. catheter. Vector doses ranged from 1 × 10(9) to 1 × 10(12) viral particles per day. Toxicity was evaluated using CTCv3.0. CA-125 and Response Evaluation Criteria in Solid Tumors (RECIST) criteria were used to determine clinical efficacy. Corollary biological studies included assessment of CRAd replication, wild-type virus generation, viral shedding, and neutralizing antibody response.

RESULTS

Twenty-one patients were treated. Adverse clinical effects were limited to grade 1/2 fever, fatigue, or abdominal pain. No vector-related grade 3/4 toxicities were noted. No clinically significant laboratory abnormalities were noted. The maximum tolerated dose was not reached. Over a 1 month follow-up, 15 (71%) patients had stable disease and six (29%) had progressive disease. No partial or complete responses were noted. Seven patients had a decrease in CA-125; four had a >20% drop. RGD-specific PCR showed the presence of study vector in ascites of 16 patients. Seven revealed an increase in virus after day 3, suggesting replication of Ad5-Δ24-RGD. Minimal wild-type virus generation was detected. Viral shedding studies showed insignificant shedding in the serum, saliva, and urine. Anti-adenoviral neutralizing antibody effects were prevalent.

CONCLUSIONS

This study, the first to evaluate an infectivity-enhanced CRAd in human cancer, shows the feasibility, safety, potential antitumor response, and biological activity of this approach in ovarian cancer. Further evaluation of infectivity enhanced virotherapy approaches for malignant gynecologic diseases is warranted.

Serotype chimeric human adenoviruses for cancer gene therapy

Cancer gene therapy consists of numerous approaches where the common denominator is utilization of vectors for achieving therapeutic effect. A particularly potent embodiment of the approach is virotherapy, in which the replication potential of an oncolytic virus is directed towards tumor cells to cause lysis, while normal cells are spared. Importantly, the therapeutic effect of the initial viral load is amplified through viral replication cycles and production of progeny virions. All cancer gene therapy approaches rely on a sufficient level of delivery of the anticancer agent into target cells. Thus, enhancement of delivery to target cells, and reduction of delivery to non-target cells, in an approach called transductional targeting, is attractive. Both genetic and non-genetic retargeting strategies have been utilized. However, in the context of oncolytic viruses, it is beneficial to have the specific modification included in progeny virions and hence genetic modification may be preferable. Serotype chimerism utilizes serotype specific differences in receptor usage, liver tropism and seroprevalence in order to gain enhanced infection of target tissue. This review will focus on serotype chimeric adenoviruses for cancer gene therapy applications.

Development of a targeted gene vector platform based on simian adenovirus serotype 24

Efforts to develop adenovirus vectors suitable for genetic interventions in humans have identified three major limitations of the most frequently used vector prototype, human adenovirus serotype 5 (Ad5). These limitations--widespread preexisting anti-Ad5 immunity in humans, the high rate of transduction of normal nontarget tissues, and the lack of target-specific gene delivery--justify the exploration of other Ad serotypes as vector prototypes. In this paper, we describe the development of an alternative vector platform using simian Ad serotype 24 (sAd24). We found that sAd24 virions formed unstable complexes with blood coagulation factor X and, because of that, transduced the liver and other organs at low levels when administered intravenously. The overall pattern of biodistribution of sAd24 particles was similar, however, to that of Ad5, and the intravenously injected sAd24 was cleared by Kupffer cells, leading to their depletion. We modified the virus's fiber protein to design a Her2-specific derivative of sAd24 capable of infecting target human tumor cells in vitro. In the presence of neutralizing anti-Ad5 antibodies, Her2-mediated infection with targeted sAd24 compared favorably to that with the Ad5-derived vector. When used to target Her2-expressing tumors in animals, this fiber-modified vector achieved a higher level of gene transfer to metastasis-containing murine lungs than to tumor-free lungs. In aggregate, these studies provide important insights into sAd24 biology, identify its advantages and limitations as a vector prototype, and are thus essential for further development of an sAd24-based gene delivery platform.

Docetaxel increases antitumor efficacy of oncolytic prostate-restricted replicative adenovirus by enhancing cell killing and virus distribution

BACKGROUND

We explored multiple molecular mechanisms of the combination of docetaxel and an oncolytic prostate-restricted replication competent adenovirus (Ad) (PRRA) in advanced prostate cancer (PCa) models. The combinational therapy has potential to overcome the therapeutic limitations of poor virus distribution inside solid tumors.

METHODS

We evaluated the effect of docetaxel on the antitumor efficacy and efficiency of virus transduction, transgene expression and virus distribution of PRRA in a prostate-specific antigen/prostate-specific membrane antigen-positive tumor xenograft model. We also evaluated the effect of docetaxel on apoptosis induction, cell killing and the efficiency of transgene expression and virus replication in vitro.

RESULTS

Tumor growth inhibition was significantly enhanced when docetaxel was administrated before intratumor injection of PRRA. In vivo dual-photon microscopy and ex vivo fluorescence microscopy and immunohistochemistry showed that docetaxel increased transgene expression and expanded virus distribution. The combination of docetaxel and PRRA also increased cell apoptosis. In vitro, docetaxel significantly increased cell killing in PRRA-treated PCa cells. Docetaxel significantly increased Ad-mediated trangene expression independent of Ad binding receptors and replication capability. Docetaxel increased the activity of cytomegalovirus (CMV) promoter but not of a chimeric prostate-specific enhancer, resulting in higher transgene expression. The enhanced CMV promoter activity resulted from activation of p38 mitogen-activated protein kinase (MAPK) because inhibition of p38 MAPK blocked the docetaxel-induced increase in CMV promoter activity.

CONCLUSIONS

Combining docetaxel with an oncolytic PRRA improved therapeutic potential by expanding virus distribution and enhancing cell apoptosis and killing. These studies suggested a novel mechanism for enhancing the effect of therapeutic genes delivered by a PRRA.

Suppression of ovarian cancer growth via systemic administration with liposome-encapsulated adenovirus-encoding endostatin

Gene therapy using adenoviral vector containing the endostatin gene is a promising strategy for advanced cancers. However, host immune response to adenovirus and the lack of the requisite coxsackie-adenovirus receptor (CAR) in many primary cells limit the in vivo application. Liposome-complexed adenoviral vectors have proven to be useful for enhancing gene delivery in target cells that lack adenoviral receptors and avoiding a neutralizing antibody response. Here, we investigated antitumor effects of intravenous administration with PEG-PE cationic liposome-encapsulated recombinant human endostatin adenovirus (Ad-hEndo) on CAR-negative ovarian cancer. Electron micrography (EM) showed that these liposomes efficiently encapsulated the vectors, allowing CAR-independent adenovector transduction. The results showed that the complex enhanced transfection efficiency of recombinant adenovirus. Prolonged systemic administration was performed in immunocompetent mice and did not induce significant antibody response. The antitumor effect with PEG-PE cationic liposome encapsulated with Ad-hE (Ad-hE/lipo) was evaluated in the human ovarian cancer model. Systemic administration was well tolerated and resulted in marked suppression of tumor growth in an established ovarian cancer model, which was associated with a decreased number of micro-vessels and increased apoptosis of tumor cells. Our study shows that PEG-PE cationic liposome-encapsulated Ad-hE (Ad-hE/Lipo) can be administrated intravenously and lastingly to inhibit angiogenesis, thus showing promising clinical application.

Role of RGD-containing ligands in targeting cellular integrins: Applications for ovarian cancer virotherapy (Review)

The purpose of this article was to review the current strategies of targeted therapy to integrins and define the best course of future research in ovarian cancer targeting. Cell surface integrin targeting has been used as a strategy for targeted therapy of several diseases with some success. The combination of virotherapy and integrin-targeting shows promise as a method for targeting ovarian cancer. More specifically, targeting of ovarian cancer with integrin-directed adenoviruses may lead to therapy with fewer toxicities and side effects. This article offers a review of the benefits of integrin-specific targeted therapy for several diseases and proposes a unique anti-ovarian cancer strategy involving the combination of the above with virotherapy as a potential anti-ovarian cancer treatment.

Efficient delivery of angiostatin K1-5 into tumors following insertion of an NGR peptide into adenovirus capsid

Adenovirus (Ad)-mediated delivery of anti-angiogenic molecules into tumors constitutes an appealing approach for growth inhibition. However, lack of expression on tumors of Ad receptors leads to weak tumor transduction. Therefore, to provide Ad with a new entry pathway into tumors, an NGR peptide was inserted into either fiber (AdFNGR) or hexon (AdHNGR) capsid proteins. This strategy provided Ad with a very efficient entry pathway in both endothelial cells and tumor cells, with the highest efficacy observed for AdHNGR. Using pharmacological, biochemical and genetic approaches, AdHNGR and AdFNGR were shown to bind not only to CD13 receptor, but also to alphavbeta3 integrins. Both vectors were efficient tools to deliver angiostatin K1-5 cDNA into endothelial cells, thus leading to a dramatic inhibition of their proliferation and increased cell death. Although AdHNGR and Adwt were found to display similar gene transduction efficacy in Lewis lung carcinoma (LLC), pseudotyping AdHNGR with an Ad3-fiber unmasked the ability of NGR-peptide to target these tumors. As a result, delivery of angiostatin K1-5 cDNA into highly aggressive tumors translated into a stronger inhibition of their growth. Altogether, our results suggest that NGR-bearing Ad are valuable tools to realize the potential of this anti-angiogenic approach to anti-tumor therapy.

Reduction of nontarget infection and systemic toxicity by targeted delivery of conditionally replicating viruses transported in mesenchymal stem cells

The fiber-modified adenoviral vector Delta-24-RGD (D24RGD) offers vast therapeutic potential. Direct injection of D24RGD has been used to successfully target ovarian tumors in mice. However, systemic toxicity, especially in the liver, profoundly limits the efficacy of direct viral vector delivery. Mesenchymal stem cells (MSC) have the ability to function as a vector for targeted gene therapy because of their preferential engraftment into solid tumors and participation in tumor stroma formation. We show that MSC-guided delivery of D24RGD is specific and efficient and reduces the overall systemic toxicity in mice to negligible levels compared with D24RGD alone. In our model, we found efficient targeted delivery of MSC-D24RGD to both breast and ovarian cell lines. Furthermore, immunohistochemical staining for adenoviral hexon protein confirmed negligible levels of systemic toxicity in mice that were administered MSC-D24RGD compared with those that were administered D24RGD. These data suggest that delivery of D24RGD through MSC not only increases the targeted delivery efficiency, but also reduces the systemic exposure of the virus, thereby reducing overall systemic toxicity to the host and ultimately enhancing its value as an anti-tumor therapeutic candidate.

Identifying the safety profile of Ad5.SSTR/TK.RGD, a novel infectivity-enhanced bicistronic adenovirus, in anticipation of a phase I clinical trial in patients with recurrent ovarian cancer

PURPOSE

The purpose of this study was to evaluate the biodistribution and toxicity of Ad5.SSTR/TK.RGD, an infectivity-enhanced adenovirus expressing a therapeutic suicide gene and somatostatin receptor type 2 (for noninvasive assessment of gene transfer with nuclear imaging) in advance of a planned phase I clinical trial for recurrent ovarian carcinoma.

EXPERIMENTAL DESIGN

Cohorts of Syrian hamsters were treated i.p. for 3 consecutive days with Ad5.SSTR/TK.RGD or control buffer with or without the prodrug ganciclovir (GCV) and euthanized on day 4, 19, or 56. Tissue and serum samples were evaluated for the presence of virus using qPCR analysis and were assessed for vector-related tissue or laboratory effects.

RESULTS

Levels of Ad5.SSTR/TK.RGD in blood and tissues outside of the abdominal cavity were low, indicating minimal systemic absorption. GCV did not affect Ad5.SSTR/TK.RGD biodistribution. The mean Ad5.SSTR/TK.RGD viral level was 100-fold lower on day 19 than day 4, suggesting vector elimination over time. Animals in the Ad5.SSTR/TK.RGD +/- GCV cohort had clinical laboratory parameters and microscopic lesions in the abdominal organs indicative of an inflammatory response. Toxicity in this dose cohort seemed to be reversible over time.

CONCLUSIONS

These studies provide justification for planned dosing of Ad5.SSTR/TK.RGD for a planned phase I clinical trial and insights regarding anticipated toxicity.

Methods to monitor gene therapy with molecular imaging

Recent progress in scientific and clinical research has made gene therapy a promising option for efficient and targeted treatment of several inherited and acquired disorders. One of the most critical issues for ensuring success of gene-based therapies is the development of technologies for non-invasive monitoring of the distribution and kinetics of vector-mediated gene expression. In recent years many molecular imaging techniques for safe, repeated and high-resolution in vivo imaging of gene expression have been developed and successfully used in animals and humans. In this review molecular imaging techniques for monitoring of gene therapy are described and specific use of these methods in the different steps of a gene therapy protocol from gene delivery to assessment of therapy response is illustrated. Linking molecular imaging (MI) to gene therapy will eventually help to improve the efficacy and safety of current gene therapy protocols for human application and support future individualized patient treatment.

Intravascularly administered RGD-displaying measles viruses bind to and infect neovessel endothelial cells in vivo

Systemically administered vectors must cross the endothelial lining of tumor blood vessels to access cancer cells. Vectors that interact with markers on the lumenal surface of these endothelial cells might have enhanced tumor localization. Here, we generated oncolytic measles viruses (MVs) displaying alpha(v)beta(3) integrin-binding peptides, cyclic arginine-glycine-aspartate (RGD) or echistatin, on the measles hemagglutinin protein. Both viruses had expanded tropisms, and efficiently entered target cells via binding to integrins, but also retained their native tropisms for CD46 and signaling lymphocyte activation molecule (SLAM). When fluorescently labeled and injected intravascularly into chick chorioallantoic membranes (CAMs), in contrast to unmodified viruses, the integrin-binding viral particles bound to the lumenal surface of the developing chick neovessels and infected the CAM vascular endothelial cells. In a mouse model of VEGF-induced angiogenesis in the ear pinna, the integrin-binding viruses, but not the parental virus, infected cells at sites of new blood vessel formation. When given intravenously to mice bearing tumor xenografts, the integrin-binding virus infected endothelial cells of tumor neovessels in addition to tumor parenchyma. To our knowledge, this is the first report demonstrating that oncolytic MVs can be engineered to target the lumenal endothelial surface of newly formed blood vessels when administered intravenously in living animals.

Novel adenoviral gene delivery system targeted against head and neck cancer

OBJECTIVES

The clinical applicability of adenovirus-mediated gene therapy is limited by the lack of tumor-targeted strategies. Ubiquitous expression of the coxsackie-adenovirus receptor, the native binding site for adenovirus, broadens viral tropism and increases systemic toxicity. Adenoviruses can be genetically engineered to target tumor-specific cell surface biomarkers. Here, we present a novel recombinant adenovirus vector (Ad5-Flag-LDS) that demonstrated a marked targeting bias against Hsp47, a biomarker for head and neck squamous cell carcinoma (HNSCC).

METHODS

Cell surface expression of Hsp47 was determined in six human HNSCC cell lines and in negative and positive control cells. Colocalization of LDS and Hsp47 was assessed by immunocytochemistry in Ad5-Flag-LDS-transfected cells, and subsequent transgene expression was determined. The contribution of the Hsp47 biomarker in mediating targeted gene transfer was evaluated with a blocking assay. Ad5-Flag-LDS-targeting efficacy in a mixed cell population was determined by immunofluorescence.

RESULTS

HNSCC cells had significantly higher Hsp47 biomarker density than control cell lines. After Ad5-Flag-LDS transfection, significant colocalization was found between the LDS peptide and Hsp47 biomarker, indicating that viral entry occurred via Hsp47-LDS binding. This unique tumor-targeted entry feature significantly enhanced gene transfer relative to an untargeted adenoviral vector. Blockade of Hsp47 biomarkers abrogated transgene expression, indicating that Hsp47 has a dominant role in Ad5-Flag-LDS targeting. Ad5-Flag-LDS-targeting selectivity was maintained in a cell mixture, producing greater transgene expression in Hsp47-expressing cells.

CONCLUSIONS

The enhanced targeting achieved with Ad5-Flag-LDS highlights a potential strategy for clinically applicable targeted gene therapy against HNSCC or any tumor type expressing Hsp47.

Changing the adenovirus fiber for retaining gene delivery efficacy in the presence of neutralizing antibodies

Prior infection has primed most adult humans for a rapid neutralizing antibody (NAb) response when re-exposed to adenovirus. NAb induction can severely limit the efficacy of systemic re-administration of adenoviral gene therapy. We hypothesized that changing the fiber knob could overcome NAb. Immune-competent mice were exposed to serotype 5 adenovirus (Ad5)(GL), Ad5/3luc1, Ad5lucRGD or Ad5pK7(GL). Mice immunized with Ad5(GL) featured reduced intravenous Ad5(GL) gene transfer to most organs, including the liver, lung and spleen. Ad5(GL) gene transfer was affected much less by exposure to capsid-modified viruses. Anti-Ad5(GL) NAb blocked intravenous Ad5(GL) gene transfer to orthotopic lung cancer xenografts, whereas capsid-modified viruses were not affected. When gene transfer to fresh cancer and normal lung explants was analyzed, we found that capsid-modified viruses allowed effective gene delivery to tumors in the presence of anti-Ad5(GL) NAb, whereas Ad5(GL) was blocked. In contrast, crossblocking by NAbs induced by different viruses affected gene delivery to normal human lung explants, suggesting the importance of non-fiber-knob-mediated infection mechanisms. We conclude that changing the adenovirus fiber knob is sufficient to allow a relative degree of escape from preexisting NAb. If confirmed in trials, this approach might improve the efficacy of re-administration of adenoviral gene therapy to humans.

Prostate-restricted replicative adenovirus expressing human endostatin-angiostatin fusion gene exhibiting dramatic antitumor efficacy

PURPOSE

Our previous studies coadministering a replication-deficient adenovirus expressing endostatin and angiostatin fusion gene (EndoAngio) and a prostate-restricted, replication-competent adenovirus (PRRA) showed dramatic antitumor efficacy. This study integrated EndoAngio with an improved PRRA vector to make a single antiangiogenic PRRA, thereby exerting a similarly dramatic antitumor effect with feasibility for future clinical trials.

EXPERIMENTAL DESIGN

We developed an antiangiogenic PRRA with structural improvements. The antitumor efficacy of EndoAngio-PRRA was evaluated in prostate-specific antigen/prostate-specific membrane antigen (PSA/PSMA)-positive, androgen-independent CWR22rv tumor models. The tumor vasculature and cell morphology were observed by dual-photon microscopy. The antiangiogenic effect of EndoAngio delivered by PRRA and the killing activity of EndoAngio-PRRA were evaluated in vitro. Virus-inactivated conditioned media from virus-infected PSA/PSMA-positive cells were tested for apoptosis induction in prostate cancer cells.

RESULTS

Our novel EndoAngio-PRRA is a strong antiangiogenic and antitumor agent. Nine of 10 CWR22rv tumors treated by EndoAngio-PRRA completely regressed, with 1 tumor remaining in a dormant status for 26 weeks after treatment. Dual-photon microscopy revealed that EndoAngio-PRRA not only inhibited the development of tumor vasculature but also induced apoptosis in tumor cells. Subsequent in vitro study indicated that EndoAngio-PRRA exhibited stronger tumor-specific killing activity than enhanced green fluorescent protein-PRRA, which expresses enhanced green fluorescent protein instead of EndoAngio. Virus-inactivated conditioned medium from EndoAngio-PRRA-infected PSA/PSMA-positive cells induced apoptosis in C4-2 and CWR22rv cells.

CONCLUSIONS

EndoAngio-PRRA uniquely combines three distinct antitumor effects to eliminate androgen-independent prostate cancer: antiangiogenesis, viral oncolysis, and apoptosis. This novel antiangiogenic PRRA represents a powerful agent feasible for future clinical trials for prostate cancer therapy.

Treatment of metastatic renal cancer with capsid-modified oncolytic adenoviruses

Renal cancer is a common and deadly disease that lacks curative treatments when metastatic. Here, we have used oncolytic adenoviruses, a promising developmental approach whose safety has recently been validated in clinical trials. Although preliminary clinical efficacy data exist for selected tumor types, potency has generally been less than impressive. One important reason may be that expression of the primary receptor, coxsackie-adenovirus receptor, is often low on many or most advanced tumors, although not evaluated in detail with renal cancer. Here, we tested if fluorescence-assisted cell sorting could be used to predict efficacy of a panel of infectivity-enhanced capsid-modified marker gene expressing adenoviruses in renal cancer cell lines, clinical specimens, and subcutaneous and orthotopic murine models of peritoneally metastatic renal cell cancer. The respective selectively oncolytic adenoviruses were tested for killing of tumor cells in these models, and biodistribution after locoregional delivery was evaluated. In vivo replication was analyzed with noninvasive imaging. Ad5/3-Delta24, Ad5-Delta24RGD, and Ad5.pK7-Delta24 significantly increased survival of mice compared with mock or wild-type virus and 50% of Ad5/3-Delta24 treated mice were alive at 320 days. Because renal tumors are often highly vascularized, we investigated if results could be further improved by adding bevacizumab, a humanized antivascular endothelial growth factor antibody. The combination was well tolerated but did not improve survival, suggesting that the agents may be best used in sequence instead of together. These results set the stage for clinical testing of oncolytic adenoviruses for treatment of metastatic renal cancer currently lacking other treatment options.

Intravenous administration of the conditionally replicative adenovirus Ad5-Delta24RGD induces regression of osteosarcoma lung metastases

Metastatic osteosarcoma (OS) has a very poor prognosis. New treatments are therefore wanted. The conditionally replicative adenovirus Ad5-Δ24RGD has shown promising anti-tumor effects on local cancers, including OS. The purpose of this study was to determine whether intravenous administration of Ad5-Δ24RGD could suppress growth of human OS lung metastases. Mice bearing SaOs-lm7 OS lung metastases were treated with Ad5-Δ24RGD at weeks 1, 2 and 3 or weeks 5, 6 and 7 after tumor cell injection. Virus treatment at weeks 1–3 did not cause a statistically significant effect on lung weight and total body weight. However, the number of macroscopic lung tumor nodules was reduced from a median of >158 in PBS-treated control mice to 58 in Ad5-Δ24RGD-treated mice (p = 0.15). Moreover, mice treated at weeks 5–7 showed a significantly reduced lung weight (decrease of tumor mass, p < 0.05), a significantly increased body weight gain (decrease of disease symptoms, p < 0.005) and a reduced number of macroscopic lung tumor nodules (median 60 versus > 149, p = 0.12) compared to PBS treated control animals. Adenovirus hexon expression was detected in lung tumor nodules at sacrifice three weeks after the last intravenous adenovirus administration, suggesting ongoing viral infection. These findings suggest that systemic administration of Ad5-Δ24RGD might be a promising new treatment strategy for metastatic osteosarcoma.

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.

Fas Ligand Delivery by a Prostate-Restricted Replicative Adenovirus Enhances Safety and Antitumor Efficacy

PURPOSE

Recent studies showed that Fas ligand (FasL) induced apoptosis in tumor cells and suppressed the immune response in several types of tumors. However, the toxicity of FasL limited further administration. This study delivered FasL in prostate cancer cells using an improved prostate-restricted replicative adenovirus (PRRA), thereby improving the antitumor effect while decreasing systemic toxicity.

EXPERIMENTAL DESIGN

We designed a FasL-armed PRRA, called AdIU3, by placing adenoviral E1a and E4 genes, FasL cDNA, and E1b gene under the control of two individual PSES enhancers. Tissue-specific viral replication and FasL expression were analyzed, and the tumor killing effect of AdIU3 was investigated both in vitro and in vivo using androgen-independent CWR22rv s.c. models via local administration and bone models via systemic administration. The safety of systemic administration of AdIU3 was evaluated. AdCMVFasL, in which FasL was controlled by a universal cytomegalovirus (CMV) promoter, was used as a control.

RESULTS

AdIU3 enhanced FasL expression in prostate-specific antigen (PSA)/prostate-specific membrane antigen (PSMA)-positive cells but not in PSA/PMSA-negative cells. It induced apoptosis and killed PSA/PMSA-positive prostate cancer cells but spared normal human fibroblasts, hepatocytes, and negative cells. The increase in killing activity was confirmed to result in part from a bystander killing effect. Furthermore, AdIU3 was more effective than a plain PRRA in inhibiting the growth of androgen-independent prostate cancer xenografts and bone tumor formation. Importantly, systemic administration of AdIU3 resulted in undetectable toxicity, whereas the same doses of AdCMVFasL killed all mice due to multiviscera failure in 16 h.

CONCLUSIONS

AdIU3 decreased the toxicity of FasL by controlling its expression with PSES, with greatly enhanced prostate cancer antitumor efficacy. The results suggested that toxic antitumor factors can be delivered safely by a PRRA.

Utility of TK/GCV in the context of highly effective oncolysis mediated by a serotype 3 receptor targeted oncolytic adenovirus

Arming oncolytic adenoviruses with therapeutic transgenes and enhancing transduction of tumor cells are useful strategies for eradication of advanced tumor masses. Herpes simplex virus thymidine kinase (TK) together with ganciclovir (GCV) has been promising when coupled with viruses featuring low oncolytic potential, but their utility is unknown in the context of highly effective infectivity-enhanced viruses. We constructed Ad5/3-Delta24-TK-GFP, a serotype 3 receptor-targeted, Rb/p16 pathway-selective oncolytic adenovirus, where a fusion gene encoding TK and green fluorescent protein (GFP) was inserted into 6.7K/gp19K-deleted E3 region. Ad5/3-Delta24-TK-GFP killed ovarian cancer cells effectively, which correlated with GFP expression. Delivery of GCV immediately after infection abrogated viral replication, which might have utility as a safety switch. Due to the bystander effect, killing of some cell lines in vitro was enhanced by GCV regardless of timing. In murine models of metastatic ovarian cancer, Ad5/3-Delta24-TK-GFP improved antitumor efficacy over the respective replication-deficient virus with GCV. However, GCV did not further enhance efficacy of Ad5/3-Delta24-TK-GFP in vivo. Simultaneous detection of tumor load and virus replication with bioluminescence and fluorescence imaging provided insight into the in vivo kinetics of oncolysis. In summary, TK/GCV may not add antitumor activity in the context of highly potent oncolysis.

Identification of HI-like loop in CELO adenovirus fiber for incorporation of receptor binding motifs

Vectors based on the chicken embryo lethal orphan (CELO) avian adenovirus (Ad) have two attractive properties for gene transfer applications: resistance to preformed immune responses to human Ads and the ability to grow in chicken embryos, allowing low-cost production of recombinant viruses. However, a major limitation of this technology is that CELO vectors demonstrate decreased efficiency of gene transfer into cells expressing low levels of the coxsackie-Ad receptor (CAR). In order to improve the efficacy of gene transfer into CAR-deficient cells, we modified viral tropism via genetic alteration of the CELO fiber 1 protein. The alphav integrin-binding motif (RGD) was incorporated at two different sites of the fiber 1 knob domain, within an HI-like loop that we identified and at the C terminus. Recombinant fiber-modified CELO viruses were constructed containing secreted alkaline phosphatase (SEAP) and enhanced green fluorescent protein genes as reporter genes. Our data show that insertion of the RGD motif within the HI-like loop of the fiber resulted in significant enhancement of gene transfer into CAR-negative and CAR-deficient cells. In contrast, CELO vectors containing the RGD motif at the fiber 1 C terminus showed reduced transduction of all cell lines. CELO viruses modified with RGD at the HI-like loop transduced the SEAP reporter gene into rabbit mammary gland cells in vivo with an efficiency significantly greater than that of unmodified CELO vector and similar to that of Ad type 5 vector. These results illustrate the potential for efficient CELO-mediated gene transfer into a broad range of cell types through modification of the identified HI-like loop of the fiber 1 protein.

Systemic efficacy of oncolytic adenoviruses in imagable orthotopic models of hormone refractory metastatic breast cancer

Conditionally replicating oncolytic adenoviruses represent a promising developmental strategy for the treatment of cancer refractory to current treatments, such as hormone refractory metastatic breast cancer. In clinical cancer trials, adenoviral agents have been well tolerated, but gene transfer has been insufficient for clinical benefit. One of the main reasons may be the deficiency of the primary adenovirus receptor, and therefore viral capsid modifications have been employed. Another obstacle to systemic delivery is rapid clearance of virus by hepatic Kupffer cells and subsequent inadequate bioavailability. In this study, we compared several capsid-modified oncolytic adenoviruses for the treatment of breast cancer with and without Kupffer cell inactivation. Replication deficient capsid-modified viruses were analyzed for their gene transfer efficacy in vitro in breast cancer cell lines and clinical samples and in vivo in orthotopic models of breast cancer. The effect of Kupffer cell depleting agents on gene transfer efficacy in vivo was evaluated. An aggressive lung metastatic model was developed to study the effect of capsid-modified oncolytic adenoviruses on survival. Capsid-modified viruses displayed increased gene transfer and cancer cell killing in vitro and resulted in increased survival in an orthotopic model of lung metastatic breast cancer in mice. Biodistribution of viruses was favorable, tumor burden and treatment response could be monitored repeatedly. Kuppfer cell inactivation led to enhanced systemic gene delivery, but did not increase the survival of mice. These results facilitate clinical translation of oncolytic adenoviruses for the treatment of hormone refractory metastatic breast cancer.

Human Embryonic Stem Cells and Gene Therapy

Human embryonic stem cells (hESCs) theoretically represent an unlimited supply of normal differentiated cells to engineer diseased tissues to regain normal function. However, before hESCs can be useful as human therapeutics, technologies must be developed to provide them with the specific signals required to differentiate in a controlled fashion, to regulate and/or shut down the growth of hESCs and their progeny once they have been transferred to the recipient, and to circumvent the recognition of non-autologous hESC-derived cells as foreign. In the context that gene therapy technologies represent strategies to deliver biological signals to address all of these challenges, this review sets out a framework for combined gene transfer/hESC therapies. We discuss how hESCs are derived, characterized, and differentiated into specific cell lineages, and we summarize the characteristics of the 500 hESC lines reported to date. The successes and failures of gene transfer to hESCs are reviewed for both non-viral and viral vectors, as are the challenges to successful use of gene transfer in developing hESC therapy. We also consider gene transfer as a means of facilitating growth and isolation of genetically modified hESCs and as a mechanism for mitigating adverse effects associated with administration of hESCs or their derivatives. Finally, we evaluate the challenges that are likely to be encountered in translating the promise of hESCs to the clinic.

Identifying the safety profile of a novel infectivity-enhanced conditionally replicative adenovirus, Ad5-delta24-RGD, in anticipation of a phase I trial for recurrent ovarian cancer

OBJECTIVE

The purpose of this study was to evaluate the biodistribution and toxicity of the tropism-modified infectivity-enhanced conditionally replicative adenovirus, Ad5-delta24-arginine-glycine-aspartate (RGD).

STUDY DESIGN

Cohorts of cotton rats were treated intravenously or intraperitoneally for 3 consecutive days with 5 x 10(8) to 5 x 10(11) particles/kg of Ad5-delta24-RGD or controls and killed on day 8, 17, or 56. For biodistribution studies, tissue samples from 14 organ sites and serum samples were evaluated for the presence of virus with the use of quantitative polymerase chain reaction analysis. For toxicity experiments, tissue samples from more than 30 organ sites and serum samples were obtained for the assessment of vector-related tissue or laboratory effects.

RESULTS

Ad5-delta24-RGD was noted in tested samples at days 8 and 17 in animals that were treated intravenously and intraperitoneally with clearance by day 56. There were lower copies of vector noted in the blood and liver specimens of intraperitoneally treated animals. Mild peritonitis histopathologic findings were noted in rats that were treated intraperitoneally with Ad5-delta24-RGD; pathologic findings did not vary significantly with dose, over time, or in comparison to that noted in animals that were treated with Ad5-delta24.

CONCLUSION

These studies provide critical insights regarding Ad5-delta24-RGD dosing and anticipated toxicity for a planned clinical trial for ovarian cancer.