Oncolytic adenovirus delivering herpes simplex virus thymidine kinase suicide gene reduces the growth of human retinoblastoma in an in vivo mouse model

A laser-activated multifunctional targeted nanoagent for imaging and gene therapy in a mouse xenograft model with retinoblastoma Y79 cells

Retinoblastoma (RB) is the most common intraocular malignancy of childhood that urgently needs early detection and effective therapy methods. The use of nanosized gene delivery systems is appealing because of their highly adjustable structure to carry both therapeutic and imaging agents. Herein, we report a folic acid (FA)-modified phase-changeable cationic nanoparticle encapsulating liquid perfluoropentane (PFP) and indocyanine green (ICG) (FA-CN-PFP-ICG, FCNPI) with good plasmid DNA (pDNA) carrying capacity, favorable biocompatibility, excellent photoacoustic (PA) and ultrasound (US) contrast, enhanced gene transfection efficiency and therapeutic effect. The liquid-gas phase transition of the FCNPI upon laser irradiation has provided splendid contrasts for US/PA dual-modality imaging in vitro as well as in vivo. More importantly, laser-mediated gene transfection with targeted cationic FCNPI nanoparticles demonstrated the best therapeutic effect compared with untargeted cationic nanoparticle (CN-PFP-ICG, CNPI) and neutral nanoparticle (NN-PFP-ICG, NNPI), both in vitro and in vivo. Such a multifunctional nanoagent is expected to combine dual-mode guided imaging with fewer side effects and proper therapeutic efficacy. These results establish an experimental foundation for the clinical detection of and therapy for RB.

STATEMENT OF SIGNIFICANCE

We successfully constructed a multifunctional targeted cationic nanoparticle (FCNPI) and meticulously compared the variations in the plasmid loading capacity and binding to Y79 cells with NNPI, CNPI, and FCNPI. FCNPI exhibited favorable plasmid loading capability, splendid ability for targeting and only it could provide optimal US and PA contrast to background during a considerable long time. The FCNPI/pDNA + Laser system also exhibited the best therapeutic effect in vivo; this finding proposes a potential strategy for the evaluation of an efficient gene delivery nanocarrier for gene targeting therapy of RB tumor. Our study showed that there are great advantages of targeting FCNPI to provide PA/US imaging and to enlighten laser-mediated gene transfection. FCNPI is a very helpful multifunctional agent with potential.

Designing and building oncolytic viruses

Oncolytic viruses (OVs) are engineered and/or evolved to propagate selectively in cancerous tissues. They have a dual mechanism of action; direct killing of infected cancer cells cross-primes anticancer immunity to boost the killing of uninfected cancer cells. The goal of the field is to develop OVs that are easily manufactured, efficiently delivered to disseminated sites of cancer growth, undergo rapid intratumoral spread, selectively kill tumor cells, cause no collateral damage and pose no risk of transmission in the population. Here we discuss the many virus engineering strategies that are being pursued to optimize delivery, intratumoral spread and safety of OVs derived from different virus families. With continued progress, OVs have the potential to transform the paradigm of cancer care.

Overexpression of KAI1 inhibits retinoblastoma metastasis in vitro

The present study aimed to investigate the expression of cluster of differentiation 82 (KAI1), a gene involved in the suppression of tumor metastasis, in human retinoblastoma (RB) tissue and to study the effect of KAI1 expression on RB cell migration and invasion. KAI1 expression was examined in 26 patients with non-invasive and invasive retinoblastoma using reverse transcription-quantitative polymerase chain reaction and western blot analysis. A lentiviral vector containing KAI1 cDNA was used to transfect the two RB cell lines, HXO-Rb44-Gl and Y79. Following successful transfection, the migratory and invasive capacity of the two RB cell lines was evaluated using a Transwell^® migration assay. KAI1 expression was observed to be downregulated in invasive RB compared to non-invasive RB. The migratory and invasive capacities of KAI1 transfected cell lines were significantly decreased compared to those of the control cells. KAI1 may be involved in retinoblastoma metastasis, and increased expression of KAI1 significantly inhibits the metastatic ability of RB cells in vitro.

Virotherapy targeting cyclin E overexpression in tumors with adenovirus-enhanced cancer-selective promoter

Oncolytic virotherapy can selectively destroy cancer cells and is a potential approach in cancer treatment. A strategy to increase tumor-specific selectivity is to control the expression of a key regulatory viral gene with a tumor-specific promoter. We have previously found that cyclin E expression is augmented in cancer cells after adenovirus (Ad) infection. Thus, the cyclin E promoter that is further activated by Ad in cancer cells may have unique properties for enhancing oncolytic viral replication. We have shown that high levels of viral E1a gene expression are achieved in cancer cells infected with Ad-cycE, in which the endogenous Ad E1a promoter was replaced with the cyclin E promoter. Ad-cycE shows markedly selective oncolytic efficacy in vitro and destroys various types of cancer cells, including those resistant to ONYX-015/dl1520. Furthermore, Ad-cycE shows a strong capacity to repress A549 xenograft tumor growth in nude mice and significantly prolongs survival. This study suggests the potential of Ad-cycE in cancer therapy and indicates the advantages of using promoters that can be upregulated by virus infection in cancer cells in development of oncolytic viruses. Key messages: Cyclin E promoter activity is high in cancer cells and enhanced by adenovirus infection. Cyclin E promoter is used to control the E1a gene of a tumor-specific oncolytic adenovirus. Ad-cycE efficiently targets cancer cells and induces oncolysis. Ad-cycE significantly repressed xenograft tumor and prolonged survival.

Multimodality imaging methods for assessing retinoblastoma orthotopic xenograft growth and development

Genomic studies of the pediatric ocular tumor retinoblastoma are paving the way for development of targeted therapies. Robust model systems such as orthotopic xenografts are necessary for testing such therapeutics. One system involves bioluminescence imaging of luciferase-expressing human retinoblastoma cells injected into the vitreous of newborn rat eyes. Although used for several drug studies, the spatial and temporal development of tumors in this model has not been documented. Here, we present a new model to allow analysis of average luciferin flux ([Formula: see text]) through the tumor, a more biologically relevant parameter than peak bioluminescence as traditionally measured. Moreover, we monitored the spatial development of xenografts in the living eye. We engineered Y79 retinoblastoma cells to express a lentivirally-delivered enhanced green fluorescent protein-luciferase fusion protein. In intravitreal xenografts, we assayed bioluminescence and computed [Formula: see text], as well as documented tumor growth by intraocular optical coherence tomography (OCT), brightfield, and fluorescence imaging. In vivo bioluminescence, ex vivo tumor size, and ex vivo fluorescent signal were all highly correlated in orthotopic xenografts. By OCT, xenografts were dense and highly vascularized, with well-defined edges. Small tumors preferentially sat atop the optic nerve head; this morphology was confirmed on histological examination. In vivo, [Formula: see text] in xenografts showed a plateau effect as tumors became bounded by the dimensions of the eye. The combination of [Formula: see text] modeling and in vivo intraocular imaging allows both quantitative and high-resolution, non-invasive spatial analysis of this retinoblastoma model. This technique will be applied to other cell lines and experimental therapeutic trials in the future.

Anti-tumor effects of an oncolytic adenovirus expressing hemagglutinin-neuraminidase of Newcastle disease virus in vitro and in vivo

Oncolytic virotherapy has been an attractive drug platform for targeted therapy of cancer over the past few years. Viral vectors can be used to target and lyse cancer cells, but achieving good efficacy and specificity with this treatment approach is a major challenge. Here, we assessed the ability of a novel dual-specific anti-tumor oncolytic adenovirus, expressing the hemagglutinin-neuraminidase (HN) gene from the Newcastle disease virus under the human telomerase reverse transcriptase (hTERT) promoter (Ad-hTERTp-E1a-HN), to inhibit esophageal cancer EC-109 cells in culture and to reduce tumor burden in xenografted BALB/c nude mice. In vitro, infection with Ad-hTERT-E1a-HN could inhibit the growth of EC-109 cells significantly and also protect normal human liver cell line L02 from growth suppression in 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays. Ad-hTERT-E1a-HN also effectively and selectively decreased the sialic acid level on EC-109 cells, but not on L02 cells. Furthermore, Ad-hTERT-E1a-HN was shown to induce the apoptosis pathway via acridine orange and ethidium bromide staining (AO/EB staining), increase reactive oxygen species (ROS), reduce mitochondrial membrane potential and release cytochrome c. In vivo, xenografted BALB/c nude mice were treated via intratumoral or intravenous injections of Ad-hTERT-E1a-HN. Although both treatments showed an obvious suppression in tumor volume, only Ad-hTERT-E1a-HN delivered via intratumoral injection elicited a complete response to treatment. These results reinforced previous findings and highlighted the potential therapeutic application of Ad-hTERT-E1a-HN for treatment of esophageal cancer in clinical trials.

[Application of gene therapy to oncologic ophthalmology]

Since the discovery of the structure of DNA in 1953 by Watson and Crick, our understanding of the genetic causes and the regulations involved in tumor development have hugely increased. The important amount of research developed since then has led to the development of gene therapy, which specifically targets and treats cancer cells by interacting with, and correcting their genetic material. This study is a review of the most accomplished research using gene therapy aimed at treating malignant ophthalmologic diseases, and focuses more specifically on uveal melanoma and retinoblastoma. Such approaches are remarkable regarding the efficiency and the cellular targeting specificity. However, gene therapy-based treatments are so recent that many long-term interrogations subsist. The majority of the reviewed studies are conducted in vitro or in murine models, thereby requiring several years before the resulting therapies become part of the daily ophthalmologists' arsenal. However, the recent spectacular developments based on advanced scientific knowledge justify an up-to-date review that would benefit the ophthalmologist community.

Targeted expression of suicide gene by tissue-specific promoter and microRNA regulation for cancer gene therapy

In order to realise the full potential of cancer suicide gene therapy that allows the precise expression of suicide gene in cancer cells, we used a tissue specific Epithelial cell adhesion molecule (EpCAM) promoter (EGP-2) that directs transgene Herpes simplex virus–thymidine kinase (HSV-TK) expression preferentially in EpCAM over expressing cancer cells. EpCAM levels are considerably higher in retinoblastoma (RB), a childhood eye cancer with limited expression in normal cells. Use of miRNA regulation, adjacent to the use of the tissue-specific promoter, would provide the second layer of control to the transgene expression only in the tumor cells while sparing the normal cells. To test this hypothesis we cloned let-7b miRNA targets in the 3’UTR region of HSV-TK suicide gene driven by EpCAM promoter because let-7 family miRNAs, including let-7b, were found to be down regulated in the RB tumors and cell lines. We used EpCAM over expressing and let-7 down regulated RB cell lines Y79, WERI-Rb1 (EpCAM ^+ve/let-7b^{down-regulated}), EpCAM down regulated, let-7 over expressing normal retinal Müller glial cell line MIO-M1(EpCAM ^−ve/let-7b^up-regulated), and EpCAM up regulated, let-7b up-regulated normal thyroid cell line N-Thy-Ori-3.1(EpCAM ^+ve/let-7b^up-regulated) in the study. The cell proliferation was measured by MTT assay, apoptosis was measured by probing cleaved Caspase3, EpCAM and TK expression were quantified by Western blot. Our results showed that the EGP2-promoter HSV-TK (EGP2-TK) construct with 2 or 4 copies of let-7b miRNA targets expressed TK gene only in Y79, WERI-Rb-1, while the TK gene did not express in MIO-M1. In summary, we have developed a tissue-specific, miRNA-regulated dual control vector, which selectively expresses the suicide gene in EpCAM over expressing cells.

Combination of oncolytic adenovirus and endostatin inhibits human retinoblastoma in an in vivo mouse model

There is a critical need for new paradigms in retinoblastoma (RB) treatment that would more efficiently inhibit tumor growth while sparing the vision of patients. Oncolytic adenoviruses with the ability to selectively replicate and kill tumor cells are a promising strategy for cancer gene therapy. Exploration of a novel targeting strategy for RB utilizing combined oncolytic adenovirus and anti-angiogenesis therapy was applied over the course of the current study with positive results. The oncolytic adenoviruses Ad-E2F1 p-E1A and Ad-TERT p-E1 were constructed. The E1 region was regulated by the E2F-1 promoter or the human telomerase reverse transcriptase (hTERT) promoter, respectively. Effects on both replication and promotion of enhanced green fluorescent protein (EGFP) expression were observed in the replication-defective adenovirus Ad-EGFP in diverse cancer cell lines, HXO-RB44, Y79, Hep3B, NCIH460, MCF-7 and HLF. The cancer cell death induced by these agents was also explored. The in situ RB model demonstrated that mice with tumors treated with the oncolytic adenovirus and replication-defective adenovirus Ad-endostatin exhibited notable cancer cell death. This anticancer effect was further examined by stereo microscope, and the survival rate of experimental mice was determined. Both Ad-E2F1 p-E1A and Ad-TERT p-E1 replicated specifically in cancer cells in vitro and promoted EGFP expression in Ad-EGFP, although Ad-E2F1 p-E1A demonstrated superior EGFP promotion activity than Ad-TERT p-E1. In Hep3B, NCIH460 and MCF-7 cells, the number of Ad-TERT p-E1 copies was observed to exceed of the number of Ad-E2F1 p-E1A copies by a minimum of 10-fold. Furthermore, Ad-TERT p-E1 demonstrated significantly superior oncolytic effects in the RB mouse model, and Ad-endostatin effectively suppressed tumor growth and extended the overall lifespan of subjects; however, the Ad-E2F1 p-E1A was clearly less effective in attaining these goals. Most notably, the antitumor effect and survival rate of subjects in the combined Ad-TERT p-E1 + Ad-endostatin group were higher than those treated with either single Ad-TERT p-E1 (p=0.097, p=0.022, respectively) or Ad-endostatin (p=0.037, p=0.006, respectively). In conclusion, application of transcription factor E2F-1 and human telomerase reverse transcriptase (hTERT) promoters to control E1 offer some guarantee that not only is RB gene therapy effective, but it is also safe. Combination therapy using the oncolytic adenovirus Ad-TERT p-E1 and replication-defective adenovirus Ad-endostatin demonstrates desirable oncolysis in the in situ RB mouse model. Additionally, E1B19K is important in the RB tumor suppression effect of oncolytic adenoviruses.

Combined treatment with an oncolytic adenovirus and antitumor activity of vincristine against retinoblastoma cells

Treatment trends of retinoblastoma (RB) have gradually evolved from eye enucleation and external radiation to local treatment. Combined treatment with an oncolytic virus and chemotherapy is currently a new method in RB treatment. To investigate the therapeutic effect of oncolytic adenovirus SG600 in combination with vincristine (VCR) on retinoblastoma in vitro, the cell viability, cell cycle effects and apoptotic activity of HXO-RB₄₄ cells treated with SG600, VCR or SG600 plus VCR were measured using a cell counting kit-8-based procedure and flow cytometry. Western blot analysis for Akt, p-Akt, p-p53 and p-Rb protein was performed to investigate the underlying mechanisms of combined therapy. The combination therapy exerted a synergistic antitumor effect via a type of G₂/M and S phase arrest rather than the induction of apoptosis. The combination of VCR and SG600 further reduced Akt phosphorylation compared with cells treated with VCR alone, suggesting that SG600 could overcome chemoresistance, perhaps by down-regulating Akt in RB cells. An increase in the expression of p-p53 and decrease in p-Rb expression in HXO-RB₄₄ after co-treatment might be associated with cell cycle block. Western blot examination revealed that VCR might enhance SG600 replication. These results suggest that viro-chemo combination therapy is a feasible and potentially promising approach for the treatment of retinoblastoma.

Adenovirus-mediated hypoxia-targeted gene therapy using HSV thymidine kinase and bacterial nitroreductase prodrug-activating genes in vitro and in vivo

Hypoxia is an important factor in tumor growth. It is associated with resistance to conventional anticancer treatments. Gene therapy targeting hypoxic tumor cells therefore has the potential to enhance the efficacy of treatment of solid tumors. Transfection of a panel of tumor cell lines with plasmid constructs containing hypoxia-responsive promoter elements from the genes, vascular endothelial growth factor (VEGF) and erythropoietin, linked to the minimal cytomegalovirus (mCMV) or minimal interleukin-2 (mIL-2) promoters showed optimum hypoxia-inducible luciferase reporter gene expression with five repeats of VEGF hypoxic-response element linked to the mCMV promoter. Adenoviral vectors using this hypoxia-inducible promoter to drive therapeutic transgenes produced hypoxia-specific cell kill of HT1080 and HCT116 cells in the presence of prodrug with both herpes simplex virus thymidine kinase/ganciclovir and nitroreductase (NTR)/CB1954 prodrug-activating systems. Significant cytotoxic effects were also observed in patient-derived human ovarian cancer cells. The NTR/CB1954 system provided more readily controllable transgene expression and so was used for in vivo experiments of human HCT116 xenografts in nude mice. Subjects treated intratumorally with Ad-VEGFmCMV-NTR and intraperitoneal injection of CB1954 demonstrated a statistically significant reduction in tumor growth. Immunohistochemistry of treated xenografts showed a good correlation between transgene expression and hypoxic areas. Further investigation of these hypoxia-inducible adenoviral vectors, alone or in combination with existing modalities of cancer therapy, may aid in the future development of successful Gene-Directed Enzyme Prodrug Therapy systems, which are much needed for targeting solid tumors.

Republished review: Gene therapy for ocular diseases

The eye is an easily accessible, highly compartmentalised and immune-privileged organ that offers unique advantages as a gene therapy target. Significant advancements have been made in understanding the genetic pathogenesis of ocular diseases, and gene replacement and gene silencing have been implicated as potentially efficacious therapies. Recent improvements have been made in the safety and specificity of vector-based ocular gene transfer methods. Proof-of-concept for vector-based gene therapies has also been established in several experimental models of human ocular diseases. After nearly two decades of ocular gene therapy research, preliminary successes are now being reported in phase 1 clinical trials for the treatment of Leber congenital amaurosis. This review describes current developments and future prospects for ocular gene therapy. Novel methods are being developed to enhance the performance and regulation of recombinant adeno-associated virus- and lentivirus-mediated ocular gene transfer. Gene therapy prospects have advanced for a variety of retinal disorders, including retinitis pigmentosa, retinoschisis, Stargardt disease and age-related macular degeneration. Advances have also been made using experimental models for non-retinal diseases, such as uveitis and glaucoma. These methodological advancements are critical for the implementation of additional gene-based therapies for human ocular diseases in the near future.

Gene therapy for ocular diseases

The eye is an easily accessible, highly compartmentalised and immune-privileged organ that offers unique advantages as a gene therapy target. Significant advancements have been made in understanding the genetic pathogenesis of ocular diseases, and gene replacement and gene silencing have been implicated as potentially efficacious therapies. Recent improvements have been made in the safety and specificity of vector-based ocular gene transfer methods. Proof-of-concept for vector-based gene therapies has also been established in several experimental models of human ocular diseases. After nearly two decades of ocular gene therapy research, preliminary successes are now being reported in phase 1 clinical trials for the treatment of Leber congenital amaurosis. This review describes current developments and future prospects for ocular gene therapy. Novel methods are being developed to enhance the performance and regulation of recombinant adeno-associated virus- and lentivirus-mediated ocular gene transfer. Gene therapy prospects have advanced for a variety of retinal disorders, including retinitis pigmentosa, retinoschisis, Stargardt disease and age-related macular degeneration. Advances have also been made using experimental models for non-retinal diseases, such as uveitis and glaucoma. These methodological advancements are critical for the implementation of additional gene-based therapies for human ocular diseases in the near future.

Combining conditionally replicating adenovirus-mediated gene therapy with chemotherapy: a novel antitumor approach

Despite significant improvements in diagnosis and innovations in the therapy of specific cancers, effective treatment of neoplastic diseases still presents major challenges. Recent studies have shown that conditionally replicating adenoviruses (CRAds) not only have the ability to destroy cancer cells but may also be potential vectors for the expression of therapeutic genes. Several studies in animal models have demonstrated that the combination of CRAds-mediated gene therapy and chemotherapy has greater therapeutic benefit than either treatment modality alone. In this review, an overview of specifications for a novel antitumor approach combining CRAd-gene therapy and chemotherapy is provided and recent progress in this field is discussed.

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

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

Recombinant baculovirus as a highly potent vector for gene therapy of human colorectal carcinoma: molecular cloning, expression, and in vitro characterization

Present therapeutic strategies for most cancers are restricted mainly to the primary tumors and are also not very effective in controlling metastatic states. Alternatively, gene therapy can be a potential option for treating such cancers. Currently mammalian viral-based cancer gene therapy is the most popular approach, but the efficacy has been shown to be quite low in clinical trials. In this study, for the first time, the insect cell-specific baculovirus Autographa californica multiple nucleopolyhedrovirus (AcMNPV) has been evaluated as a vector for gene delivery to colorectal cancer cells. Experiments involving factorial design were employed to study the individual and combined effects of different parameters such as multiplicity of infection (MOI), viral incubation time and epigenetic factors on transduction efficiency. The results demonstrate that baculovirus gene delivery system holds immense potential for development of a new generation of highly effective virotherapy for colorectal, as well as other major carcinomas (breast, pancreas, and brain), and offers significant benefits to traditional animal virus-based vectors with respect to safety concerns.

Potent anti-tumor activity of telomerase-dependent and HSV-TK armed oncolytic adenovirus for non-small cell lung cancer in vitro and in vivo

BACKGROUND

Non-small cell lung cancer (NSCLC) is the leading cause of cancer related mortality, any improvements in therapeutic strategies are urgently required. In this study we generated a novel 'suicide gene' armed oncolytic adenoviral vector and investigated its antitumor effect both in vitro and in vivo.

METHODS

Since the up-regulated expression of human telomerase reverse transcriptase (hTERT) is a hallmark of alltypes of NSCLC, we chose hTERT promoter to transcriptionally control E1A gene expression to obtain adenoviral replication in NSCLC. In order to further enhance anti-tumor effect of this oncolytic adenoviral vector, we inserted a 'suicide gene' i.e. Herpes Simplex Virus Thymidine Kinase (HSV-TK) into oncolytic adenoviral vector to engineer a novel armed oncolytic adenoviral vector 'Ad.hTERT-E1A-TK'.

RESULTS

Ad.hTERT-E1A-TK efficiently killed different types of tumor cells including two types of NSCLC cells in vitro, causing no damage to normal primary fibroblasts. Furthermore, Ad.hTERT-E1A-TK infection combined with administration of prodrug gancyclovir (GCV) resulted in more potent cytotoxicity on NSCLC cells, and synergistically suppressed human NSCLC tumor growth in nude mice.

CONCLUSION

The results from this study showed that Ad.hTERT-E1A-TK/GCV could be a potent but safe anti-tumor strategy for NSCLC biotherapy.