Gene Therapy For Brain Tumors Research Articles

Transferrin receptor targeting segment T7 containing peptide gene delivery vectors for efficient transfection of brain tumor cells

Successful gene therapy for brain tumors are often limited by two important factors, the existence of blood brain barrier (BBB) and inefficient transfection of brain tumor cells. In this study, we designed a series of peptide-based gene delivery vectors decorated with T7 segment for binding the transferrin (Tf) receptors which were highly expressed on brain tumor cells, and evaluated their ability of gene delivery. The physicochemical properties of peptide vectors or peptide/DNA complexes were studied as well. The in vitro transfection efficiency was investigated in normal and glioma cell lines. Among these complexes, PT-02/DNA complexes showed the highest transfection efficiency in glioma cells and low cytotoxicity in normal cell lines, and it could transport DNA across the BBB model in vitro. Furthermore, PT-02/DNA could deliver pIRES2-EGFP into the brain site of zebrafish in vivo. The designed peptide vectors offered a promising way for glioma gene therapy.

Gene Therapy for Brain Tumors: Identification of New Therapeutic Targets Based on RNA Structure

This project is to develop therapies to bypass challenges to effective and continuous drug delivery to the brain, for the treatment of glioblastoma multiforme (GBM). Currently, individuals diagnosed with GBM have a short life expectancy of 12‐14 months. Our approach has the potential to deliver one single dose of gene therapy directly to the GBM tumor environment and block the production of cancer‐driving genes. Epidermal growth factor receptor (EGFR) is dysregulated in 57% of all GBM. Our approach uses an adeno‐associated virus gene transfer vector encoding RNA therapeutics targeting critical elements of the EGFR pre‐mRNA transcript. We have examined the ‘pre‐mRNA structurome’ of EGFR to evaluate the accessibility of targetable regions. To advance our therapeutic strategy, we have analyzed the secondary structure of the EGFR transcript using selective 2’ hydroxyl acylation and primer extension followed by mutational profiling (SHAPE‐MaP). SHAPE‐MaP reactivity profiles were generated revealing the structure of splicing and cryptic polyadenylation signal (PAS) elements within the targeted region. We identified enhancer binding motifs surrounding the 5’ splice site and hidden elements of a cryptic polyadenylation signal. Based on these structural profiles, we generated RNA therapies that interact with structural elements to unravel the hidden polyadenylation signal with the potential to activate expression of the short therapeutic isoform. In this project, we cloned these therapies into our therapeutic delivery platform and tested their efficacy to alter EGFR gene expression in tissue culture cells. Currently, we are evaluating in vitro, the therapeutic RNA interaction with the target sequence of the EGFR pre‐mRNA transcript.

THER-06. THERAPEUTIC EFFICACY OF RRV-MEDIATED PRODRUG ACTIVATOR GENE THERAPY IN CLINICAL TRIALS OF RECURRENT HIGH-GRADE GLIOMA AND IN MURINE ORTHOTOPIC MODELS OF INTRACEREBRAL GLIOMA AND INTRACEREBELLAR MEDULLOBLASTOMA

Toca 511, a clinical-stage tumor-selective retroviral replicating vector (RRV), encodes optimized yeast cytosine deaminase (CD), which converts the prodrug 5-fluorocytosine (5-FC) to the active drug 5-fluorouracil (5-FU) within infected cancer cells. In preclinical models of intracerebral glioblastoma, 5-FU generated locally by Toca 511 (RRV-CD) prodrug activator gene therapy has also been shown to kill immunosuppressive myeloid cells in the tumor microenvironment, leading to anti-cancer immune activation and long-term survival. Early-phase clinical trials of Toca 511 in recurrent high-grade glioma showed highly promising evidence of therapeutic benefit, leading to a Phase III trial completed in late 2019 (n=400 patients, randomized 1:1 vs. standard chemotherapy), which appeared to show negative results overall. However, additional analysis showed possible efficacy in prespecified subgroups, and further clinical investigation is being pursued. In preclinical studies, we have also evaluated RRV for use in medulloblastoma, the most common malignant tumor of the pediatric nervous system. Both established and primary human medulloblastoma cell lines supported efficient RRV replication in vitro, with spread to >90% of cells by day 10 post-inoculation, and RRV-CD-transduced medulloblastoma cells showed significant dose-dependent reduction of viability upon exposure to 5-FC, compared to controls. In an intracerebellar HDMB03 medulloblastoma model, RRV-CD-treated mice exhibited long-term survival while on sequential cycles of 5-FC prodrug, until prodrug treatment was stopped, after which 25% long-term survival was observed (median survival 110 days) as compared to controls (median survival 28 days, 100% lethality) (p=0.00007). These results support further evaluation of RRV-mediated prodrug activator gene therapy for pediatric brain tumors.

Non-adhesive and highly stable biodegradable nanoparticles that provide widespread and safe transgene expression in orthotopic brain tumors.

Several generations of poly(β-amino ester) (PBAE) polymers have been developed for efficient cellular transfection. However, PBAE-based gene vectors, similar to other cationic materials, cannot readily provide widespread gene transfer in the brain due to adhesive interactions with the extracellular matrix (ECM). We thus engineered eight vector candidates using previously identified lead PBAE polymer variants but endowed them with non-adhesive surface coatings to facilitate their spread through brain ECM. Specifically, we screened for the ability to provide widespread gene transfer in tumor spheroids and healthy mouse brains. We then confirmed that a lead formulation provided widespread transgene expression in orthotopically established brain tumor models with an excellent in vivo safety profile. Lastly, we developed a method to store it long-term while fully retaining its brain-penetrating property. This new platform provides a broad utility in evaluating novel genetic targets for gene therapy of brain tumors and neurological disorders in preclinical and clinical settings. Graphical abstract We engineered biodegradable DNA-loaded brain-penetrating nanoparticles (DNA-BPN) possessing small particle diameters (< 70nm) and non-adhesive surface coatings to facilitate their spread through brain tumor extracellular matrix (ECM). These DNA-BPN provide widespread gene transfer in models recapitulating the ECM barrier, including three-dimensional multicellular tumor spheroids and mice with orthotopically established brain tumor.

Angiogenesis-targeting microbubbles combined with ultrasound-mediated gene therapy in brain tumors

The major challenges in gene therapy for brain cancer are poor transgene expression due to the blood-brain barrier (BBB) and neurologic damage caused by conventional intracerebral injection. Non-viral gene delivery using ultrasound-targeted microbubbles (MBs) oscillation via the systematic transvascular route is attractive, but there is currently no high-yielding and targeted gene expression method. In this study, we developed a non-viral and angiogenesis-targeting gene delivery approach for efficient brain tumor gene therapy without brain damage. We developed a VEGFR2-targeted and cationic microbubbles (VCMBs) gene vector for use with transcranial focused ultrasound (FUS) exposure to allow transient gene delivery. The system was tested in a brain tumor model using the firefly luciferase gene and herpes simplex virus type 1 thymidine kinase/ganciclovir (pHSV-TK/GCV) with VCMBs under FUS exposure for transgene expression and anti-tumor effect. In vitro data showed that VCMBs have a high DNA-loading efficiency and high affinity for cancer cells. In vivo data confirmed that this technique enhanced gene delivery into tumor tissues without affecting normal brain tissues. The VCMBs group resulted in higher luciferase expression (3.8 fold) relative to the CMBs group (1.9 fold), and the direct injection group. The tumor volume on day 25 was significantly smaller in rats treated with the pHSV-TK/GCV system using VCMBs under FUS (9.7±5.2mm3) than in the direct injection group (40.1±4.3mm3). We demonstrated the successful use of DNA-loaded VCMBs and FUS for non-viral, non-invasive and targeted gene delivery to brain tumors.

A New Approach in Gene Therapy of Glioblastoma Multiforme: Human Olfactory Ensheathing Cells as a Novel Carrier for Suicide Gene Delivery

Olfactory ensheathing cells (OECs) of human olfactory mucosa are a type of glial-like cells that possess good migratory and tropism properties. We believe that neuronal-derived vehicle may have better capability to receive to the site of injury. In addition to, obtaining of such vehicle from the patient reduces risk of unwanted complications. So, in this study, we investigate whether human olfactory ensheathing cells can be used as a cell source for the first time in gene delivery to assay the tumoricidal effect of herpes simplex virus thymidine kinase gene (HSV-tk) on glioblastoma multiforme (GBM). We obtained OECs from superior turbinate of human nasal cavity mucosa, and cell phenotype was confirmed by the expression of cell-specific antigens including low-affinity nerve growth factor receptor (p75 neurotrophin receptor), microtubule-associated protein-2 (MAP2), and S100 calcium binding protein B (S100-beta) using immunocytochemistry. Then, these cells were transduced by lentiviral vector for transient and stable expression of the herpes simplex virus thymidine kinase gene (OEC-tk). The migratory capacity of OEC-tk, their potency to convert prodrug ganciclovir to toxic form, and cytotoxic effect on astrocyte cells were assayed in vitro. The OECs showed fibroblast-like morphology and expressed specific antigens such as p75 neurotrophin receptor, S100-beta, and MAP2. Our results indicated that OECs-tk were able to migrate toward primary cultured human glioblastoma multiforme and affected survival rate of tumor cells according to exposure time and concentration of ganciclovir. Also, OECs-HSV-tk was capable of inducing apoptosis in tumor cells. Our findings suggest that human OECs could employ as a possible tool to transfer anticancer agent in gene therapy of brain tumor.

Advances in gene therapy and immunotherapy for brain tumors.

Treatments for malignant glioma, the most lethal and common primary brain tumor, are undergoing a dramatic evolution led by biological and technological advancements. This review focuses on developments in novel areas of gene therapy and immunotherapy, particularly vaccine development. Advances in basic research of antigen-presenting cells and applications of cytokines and immunogenic antigens have contributed to recent vaccine development for the treatment of intracranial malignant glioma. We have reviewed various vaccine designs, such as utilization of tumor antigen-loaded dendritic cells. Many immunotherapeutic manipulations require the use of recombinant genetic technologies. Here we present the findings on improved techniques for suicide gene therapy and various oncolytic viral therapies. Some of these constructs have induced an immune response at tumor sites in animal models of glioma. The intense investigation of therapies for glioma has made significant advances in designing diverse therapies with great potential. However, vaccine development has been hampered by the lack of universal tumor-specific antigens and a limited understanding of the mechanisms of tumor-induced immunosuppression. The success of gene therapy is limited by ineffective delivery systems and possible risk of infecting normal cells. As a result of the genetic heterogeneity of glioma cells and their invasive nature, future treatment approaches are likely to combine different agents in synergistic strategies that will hopefully be successful in stopping the growth and recurrence of glioma.

Lentiviral-induced high-grade gliomas in rats: the effects of PDGFB, HRAS-G12V, AKT, and IDH1-R132H.

In human gliomas, the RTK/RAS/PI(3)K signaling pathway is nearly always altered. We present a model of experimental gliomagenesis that elucidates the contributions of genes involved in this pathway (PDGF-B ligand, HRAS-G12V, and AKT). We also examine the effect on gliomagenesis by the potential modifier gene, IDH1-R132H. Injections of lentiviral-encoded oncogenes induce de novo gliomas of varying penetrance, tumor progression, and histological grade depending on the specific oncogenes used. Our model mimics hallmark histological structures of high-grade glioma, such as pseudopalisades, glomeruloid microvascular proliferation, and diffuse tumor invasion. We use our model of gliomagenesis to test the efficacy of an experimental brain tumor gene therapy. Our model allowed us to test the contributions of oncogenes in the RTK/RAS/PI(3)K pathway, and their potential modification by over-expression of mutated IDH1, in glioma development and progression in rats. Our model constitutes a clinically relevant system to study gliomagenesis, the effects of modifier genes, and the efficacy of experimental therapeutics.

Rat Multipotent Mesenchymal Stromal Cells Lack Long-Distance Tropism to 3 Different Rat Glioma Models

Viral gene therapy of malignant brain tumors has been restricted by the limited vector distribution within the tumors. Multipotent mesenchymal stromal cells (MSCs) and other precursor cells have shown tropism for gliomas, and these cells are currently being explored as potential vehicles for gene delivery in glioma gene therapy. To investigate MSC migration in detail after intratumoral and extratumoral implantation through syngeneic and orthotopic glioma models. Adult rat bone marrow-derived MSCs were transduced to express enhanced green fluorescent protein and implanted either directly into or at a distance from rat gliomas. We found no evidence of long-distance MSC migration through the intact striatum toward syngeneic D74(RG2), N32, and N29 gliomas in the ipsilateral hemisphere or across the corpus callosum to gliomas located in the contralateral hemisphere. After intratumoral injection, MSCs migrated extensively, specifically within N32 gliomas. The MSCs did not proliferate within tumors, suggesting a low risk of malignant transformation of in vivo grafted cell vectors. Using a model for surgical glioma resection, we found that intratumorally grafted MSCs migrate efficiently within glioma remnants after partial surgical resection. The findings point to limitations for the use of MSCs as vectors in glioma gene therapy, although intratumoral MSC implantation provides a dense and tumor-specific vector distribution.

Molecular imaging of stem cell therapy in brain tumors: a step towards personalized medicine.

Advances in gene-based medicine since the 1990s have ushered in a new therapeutic strategy of gene therapy for inborn error genetic diseases and also for cancer [1-6]. Personalized treatment strategies using stem, modified or also genetically engineered cells are becoming a reality in clinical medicine. Allogenic or autologous cells can be used for treatment and possibly for early diagnosis of diseases. Hematopoietic, stromal and organ specific stem cells are under evaluation for cell-based therapies, not only for neurological, but also cardiac, pneumological, gynecological, autoimmune and other disorders. Such cell replacement therapy and gene transfer have provided the basis for the development of potentially powerful new therapeutic strategies for a broad spectrum of neurological diseases. However, currently available treatment modalities for brain tumors, including radical surgical resection followed by radiation and chemotherapy, have substantially improved the survival rates [7, 8]; however, a large proportion of patients with brain tumors remain incurable [9]. Therefore, there is substantial need for more effective therapies for patients with malignant brain tumors, and gene therapy targeting brain tumors should fulfill this requirement. Gene therapy for brain tumors includes many therapeutic strategies and these strategies can be subgrouped in two major categories: (i) molecular and (ii) immunologic. The widely used molecular gene therapy approach is suicide gene therapy based on the conversion of non-toxic prodrugs into active anticancer agents via introduction of enzymes, and genetic immunotherapy involves the gene transfer of immune-stimulating cytokines including interleukin (IL)-4, IL-12 and tumor necrosis factor related apoptosis inducing ligand (TRAIL) [10, 11]. For both molecular and immune gene therapy, stem cells can be used as a delivery vehicle of therapeutic genes [12]. Stem cells possess an inherent tumor tropism and have the capacity to target therapeutic genes to tumors, which supports their use as a reliable delivery vehicle to target therapeutic gene products to primary brain tumors and metastatic cancers throughout the brain [13, 14]. The main promise of this emerging technology centers on the potent migratory tropism exhibited by stem cells for disseminated foci of intracranial pathologic findings. This important characteristic, which has been validated in a wide set of preclinical studies, forms a foundation for the use of transplanted stem cell populations as vehicles for the delivery of tumor-toxic molecules to sites of intracranial tumor [9, 14]. The significance of neuronal stem cell (NSC)-based gene therapy for brain tumor is that it is possible to exploit the tumor-tropic Corresponding author: Bernhard Schaller MD, PhD, DSC University of Oradea Romania Phone: 079 666 99 42b E-mail: skull_base-surgery@yahoo.de Editorial

Construction of novel brain‐targeting gene delivery system by natural magnetic nanoparticles

AbstractThe main objective in gene therapy of brain tumors is to develop efficient, low toxic, and brain‐targeting gene delivery systems which can cross the blood‐brain barrier (BBB) and deliver therapeutic gene to the brain cancerous tissues. In this study, we designed and constructed a novel gene delivery systems (Tat‐MS‐PAMAM) by modifying the magnetosome (MS) with polyamidoamine (PAMAM) dendrimers and Tat peptides for the first time. Tat‐MS‐PAMAM readily formed polyplexes with the luciferase reporter plasmid (pGL‐3) and improved plasmid complexation and stability against polyanion and DNase I. Transfection efficiencies of Tat‐MS‐PAMAM polyplexes with pGL‐3 were studied using U251 human glioma cells in vitro. The result showed that the incorporation of external magnetic field and Tat peptides could significantly improve transfection efficiency of delivery system. Furthermore, biodistribution in vivo demonstrated that Tat‐MS‐PAMAM could efficiently transport across the BBB and assemble at brain tissue of rat detected by single photo emission computed tomography. Thus, with the multifunction of magnetic targeting, BBB transporting, and efficient gene transfecting, Tat‐MS‐PAMAM might be a novel nonviral delivery system for gene therapy of brain tumors. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Identification and functional characterization of glioma-specific promoters and their application in suicide gene therapy

Suicide gene therapy has been shown to be effective in inducing tumor regression. In this study, a human brain tumor-specific promoter was identified and used to develop transcriptionally targeted gene therapy. We searched for genes with brain tumor-specific expression. By insilico and reverse-transcription polymerase chain reaction screening, MAGE-A3 and SSX4 were found to be expressed in a tumor-specific manner. SSX4 gene promoter activity was high in human brain tumor cells but not in normal human astrocyte cells, whereas the MAGE-A3 promoter showed activity in both tumor and normal cells. A retrovirus vector carrying a suicide gene, the herpes simplex virus thymidine kinase gene controlled by the SSX4 promoter, was constructed to evaluate the efficacy of the promoter in tumor-specific gene therapy. Glioma and human telomerase catalytic subunit-immortalized fibroblast BJ-5ta cell lines transduced with retrovirus vectors were assayed for killing activity by ganciclovir. Glioma cell lines were effectively killed by ganciclovir in a concentration-dependent manner, whereas BJ-5ta cells were not. By contrast, MAGE-A3 promoter failed to induce cytotoxicity in a brain tumor-specific manner. In addition, mouse glioma RSV-M cells transduced with retrovirus vector also showed suppressed tumor formation activity in syngeneic mice in response to ganciclovir administration. Therefore, the SSX4 promoter is a candidate for brain tumor-specific gene therapy and supports the efficacy and safety of suicide gene therapy for malignant brain tumors.

Adenovirus-mediated antisense Src gene therapy for glioma

Objective To investigate the therapeutic effects and the mechanisms of adenovirusmediated gene transfer of antisense Src for rat C6 glioma. Methods C6 glioma cells were infected with recombinant adenovirus containing antisense Src gene. Cell morphology, cell growth curve and cloning efficiency assay were examined. The intracranial C6 glioma animal model was established in immunocompetent Wistar rats. Recombinant adenoviruses containing antisense Src gene were stereotactically injected into the tumor areas. Tumor volumes were measured. Western blotting was used to detect Src, Ras and MAPK proteins expression. Caspase-3 and Caspase-8 mRNA expression in tumor was quantified by real-time reverse transcription-polymerase chain reaction (RT-PCR). Results Cell growth and cloning efficiency of C6 glioma cells infected with recombinant adenovirus containing antisense Src gene were significantly decreased.In situ injecting recombinant adenovirus containing antisense Src gene suppressed tumor growth. In vivo investigation showed Src, Ras and MAPK proteins were significantly decreased in the recombinant adenovirus containing antisense Src gene-treated group, and Caspase-3 and Caspase-8 expression was increased. Conclusion Adenovirus-mediated gene transfer of antisense Src inhibited C6 glioma cells growth in vivo and in vitro. Src-Ras-MAPK signal pathway played an important role in the progression of glioma. MAPK signal pathway blockade could augment apoptosis proteins Caspase-3 and Caspase-8 expression. Our results suggested adenovirus-mediated gene transfer of antisense Src was a promising target for gene therapy of malignant brain tumors. Key words: Glioma; Gene therapy; Antisense Src; Adenovirus vector

Neural Stem Cell-based Gene Therapy for Brain Tumors

Advances in gene-based medicine since 1990s have ushered in new therapeutic strategy of gene therapy for inborn error genetic diseases and cancer. Malignant brain tumors such as glioblastoma multiforme and medulloblastoma remain virtually untreatable and lethal. Currently available treatment for brain tumors including radical surgical resection followed by radiation and chemotherapy, have substantially improved the survival rate in patients suffering from these brain tumors; however, it remains incurable in large proportion of patients. Therefore, there is substantial need for effective, low-toxicity therapies for patients with malignant brain tumors, and gene therapy targeting brain tumors should fulfill this requirement. Gene therapy for brain tumors includes many therapeutic strategies and these strategies can be grouped in two major categories: molecular and immunologic. The widely used molecular gene therapy approach is suicide gene therapy based on the conversion of non-toxic prodrugs into active anticancer agents via introduction of enzymes and genetic immunotherapy involves the gene transfer of immune-stimulating cytokines including IL-4, IL-12 and TRAIL. For both molecular and immune gene therapy, neural stem cells (NSCs) can be used as delivery vehicle of therapeutic genes. NSCs possess an inherent tumor tropism that supports their use as a reliable delivery vehicle to target therapeutic gene products to primary brain tumors and metastatic cancers throughout the brain. Significance of the NSC-based gene therapy for brain tumor is that it is possible to exploit the tumor-tropic property of NSCs to mediate effective, tumor-selective therapy for primary and metastatic cancers in the brain and outside, for which no tolerated curative treatments are currently available.

846. Exosome-Mediated Suicide Gene Therapy for Brain Tumors

846. Exosome-Mediated Suicide Gene Therapy for Brain Tumors

Tat-BMPs-PAMAM Conjugates Enhance Therapeutic Effect of Small Interference RNA on U251 Glioma Cells In Vitro and In Vivo

Polyamidoamine (PAMAM) dendrimer and Tat peptides were conjugated to bacterial magnetic nanoparticles (BMPs) for the construction of an efficient and targeted gene delivery system with transmembrane ability for the gene therapy of brain tumors. Tat-BMPs-PAMAM was complexed with small interfering RNA expression plasmid (psiRNA) corresponding to the open reading frame of the human epidermal growth factor receptor gene (psiRNA-EGFR) to downregulate the EGFR gene by electrostatic interaction. The antitumor effect of psiRNA-EGFR delivered via Tat-BMPs-PAMAM was assessed both in human glioblastoma U251-MG cells and in nude mouse models. Compared with control groups, Tat-BMPs-PAMAM/psiRNA-EGFR resulted in better suppression of EGFR expression and a more obviously arrested effect on the proliferation and invasion ability of U251 cells in vitro. In addition, the growth rate of tumor in the U251 subcutaneous nude mouse model treated with Tat-BMPs-PAMAM/psiRNA-EGFR was slower than in those treated with phosphate-buffered saline or Lipofectamine 2000/psiRNA-Scr. Also, compared with control groups, the expression of oncoproteins (EGFR, p-AKT, MMP2/9, PCNA, VEGF, Bcl-2, and cyclin D1) was obviously downregulated and the number of apoptotic cells was clearly increased in the Tat-BMPs-PAMAM/psiRNA-EGFR treatment groups. In addition, there was no significant difference between the results in vitro and in vivo for the Tat-BMPs-PAMAM/psiRNA-EGFR treatment groups and those of the Lipofectamine 2000/psiRNA-EGFR treatment groups. These results show that Tat-BMPs-PAMAM, with its targeted delivery and transmembrane ability, may be a novel gene delivery system with potential applications in the targeted gene therapy of brain tumors.

Gene Therapy for High-Grade Glioma

High-grade glioma is the most frequently occurring primary brain tumor and is associated with a poor prognosis. Current treatment regimens have had only a modest effect on the progressive course despite recent advances in surgery, radiotherapy, and chemotherapy. Gene therapy for brain tumors represents a novel and promising therapeutic approach and has been investigated clinically for the last two decades. The strategies of gene therapy include suicide gene therapy, immune gene therapy, oncolytic viral therapy, tumor suppressor gene therapy, and antisense therapy. Here, we review gene therapy approaches considering the clinical results, limitations, and future directions.

Potential adenovirus-mediated gene therapy of glioma cancer

Malignant gliomas are typically characterized by rapid cell proliferation and a marked propensity to invade and damage surrounding tissues. They are the main brain tumors notoriously resistant to currently available therapies, since they fail to undergo apoptosis upon anticancer treatments. With recent advances in neuroscience and improved understanding of the molecular mechanisms of invasive migration, gene therapy provides a new strategy for treating glioma cancer. Brain tumor gene therapy using viral vectors and stem cells has shown promise in animal model and human patient studies. Here, we review recent studies on engineering adenoviral vectors that can be used as therapy for brain tumors. The new findings presented in this study are essential for the further exploration of this cancer and they represent an approach for developing a newer and more effective therapeutic approach in the clinical treatment of human glioma cancer.

Cytosine deaminase‐producing human mesenchymal stem cells mediate an antitumor effect in a mouse xenograft model

Stem cell transplantation offers potential gene therapy for brain tumors. However, this approach has received little attention as a treatment for gastrointestinal tumors. In the present study, we explored the possibility of human bone marrow-derived mesenchymal stem cells (hMSC) producing cytosine deaminase (CD), followed by systemic 5-fluorocytosine (5-FC) administration, showing an antitumor effect on a mouse gastric cancer xenograft. We first explored the ability of hMSC, coated with fluorescent dye, to migrate to human gastric cancer MKN45 cells in vitro and in vivo. We then used hMSC in which a gene expressed the prodrug-activating enzyme CD, which can convert the prodrug 5-FC into the cytotoxic agent 5-fluorouracil (5-FU), and further investigated the potential of these cells to deliver the CD gene and to reduce tumor growth in nude mice. The migratory capacity of hMSC was confirmed by an in vitro migration assay, as well as in an in vivo model of nude mice bearing subcutaneous tumors of MKN45 cells when hMSC were injected. The migration ability of hMSC towards MKN45 cells was confirmed by migration assay. Effective conversion of 5-FC to 5-FU by hMSC transfected with the CD gene (CD-hMSC) showed therapeutic anticancer potential in a MKN45 cell co-culture system, as confirmed by thin layer chromatography. Nude mice bearing MKN45 tumors were intravenously injected with CD-hMSC, followed by systemic 5-FC treatment (500 mg/kg/day) for 7 days. Tumor volumes and weights of mice injected with CD-hMSC decreased significantly after treatment with 5-FC. However, the 5-FC-treated group without CD-hMSC injection showed neither a decrease in tumor volume nor bodyweight loss. The CD-hMSC system showed anticancer therapeutic potential, and minimized the side-effects of 5-FU.

Gene Delivery to the Nervous System: NINDS Workshop on Gene Delivery to the Nervous System Washington, DC, 12–13 November 2007

The National Institute of Neurological Disorders and Stroke (NINDS) sponsored a workshop on gene delivery to the nervous system, which took place on 12–13 November 2007 in Washington, DC. The purpose of the workshop was to convene neuroscientists, molecular virologists/vectorologists, and surgical neurologists to assess the state of the art of gene therapy for neurologic diseases and brain tumors and to address the challenges for advancing promising preclinical studies to the clinic.