Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0017636 (glioblastoma)
 18,345 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Genetically engineered, conditionally replicating herpes simplex viruses type 1 (HSV-1) are promising therapeutic agents for cancer. They can replicate in situ, spread, and exhibit oncolytic activity via a direct cytocidal effect. In addition, oncolytic HSV-1 can transfer and express foreign genes in host cells. The phase I clinical study with G207, a double-mutated HSV-1, in recurrent malignant glioma patients has shown that oncolytic HSV-1 can be safely administered into human brains. The therapeutic benefits of oncolytic HSV-1 depend on the extent of both intratumoral viral replication and induction of host antitumor immune responses. We develop new-generation oncolytic HSV-1 by enhancing these properties while retaining the safety features. G47delta was created from G207 by introducing another genetic mutation. Compared with G207, G47delta showed 1) better stimulation of human antitumor immune cells, 2) better growth properties leading to higher virus yields and increased cytopathic effect in vitro, 3) better antitumor efficacy in both immuno-competent and -incompetent animals, and 4) preserved safety in the brain of HSV-1-sensitive mice. Preparation is under way for a clinical trial using G47delta in progressive glioblastoma patients. G47delta is also suited as a backbone vector for expressing foreign molecules. Using bacterial artificial chromosome and two DNA recombinases, we have created an "armed" oncolytic HSV-1 generation system that allows insertion of transgene(s) into the genome of G47delta in a rapid and accurate manner. We found that expression of immunostimulatory molecules can significantly enhance the antitumor efficacy of G47delta. Based on these advances, we anticipate that oncolytic virus therapy using oncolytic HSV-1 will soon be established as an important modality of cancer treatment.
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PMID:Oncolytic virus therapy using genetically engineered herpes simplex viruses. 1798 91

We have examined the spread and antitumor efficacy of an oncolytic herpes simplex virus-1-based vector (G207) in glioblastoma biopsy spheroids in vitro and in vivo after local delivery to corresponding intracranial xenografts. Spheroids from three patients were infected with increasing doses of G207 and transgene expression was quantified. Other infected spheroids were followed for 10 days to assess cytotoxic effects. For the in vivo study, spheroids were grafted intracerebrally into Rowett nude rats. The resulting highly infiltrative xenografts were injected with 3.4 x 10(6) plaque-forming units (penetration study) or 6.8 x 10(6) plaque-forming units (therapeutic study) of G207 using microprocessor-controlled stereotaxic delivery. Vector spread was tracked by histochemical staining. In the therapeutic study, tumor volumes were monitored weekly by magnetic resonance imaging, and survival data were collected. In vitro, lacZ expression was seen at the spheroid surfaces 24 h postinfection, whereas the spheroid cores were transgene positive after 96 h. Cytotoxic susceptibility varied between the patients, showing a 36% to 95% lysis 10 days postinfection. Local delivery of G207 into intracranial xenografts resulted in extensive vector spread throughout the lesions. In the therapeutic study, G207 application reduced tumor volumes compared with controls, but did not significantly improve survival of the animals. Histologic analysis revealed infection of host structures such as the ventricular and choroid plexus ependyma. In conclusion, G207 replicates in patient-derived glioblastoma multiforme xenografts and tumor volumes are reduced after intratumoral delivery; however, the survival data suggest that the therapeutic effect could be improved by repeated vector application or through combination with other treatment modalities.
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PMID:Oncolytic herpes simplex virus type-1 therapy in a highly infiltrative animal model of human glioblastoma. 1831 82

Herpes simplex virus thymidine kinase (TK) gene transfer followed by ganciclovir (GCV) administration is an approach investigated for glioblastoma treatment. The bystander effect (BE) enhances the cytotoxic effect of this strategy by allowing the diffusion of phosphorylated GCV from TK-expressing cells toward neighboring TK negative cells. This transfer of toxic metabolites is mainly mediated via gap junctions that are composed of connexins. Downregulation and/or cytoplasmic localization of connexins are common in tumors, and should be detrimental to the success of the TK/GCV strategy. In this study, we investigated the level of expression, the localization and the functionality of connexin43 (Cx43) in three glioblastoma cell lines. We showed that Cx43 was predominantly located in lysosomes and late endosomes, with only few gap junctions present at the cell surface. Surprisingly, the gap-junctional intercellular communication (GJIC) and the BE capacity were preserved, and in two of the cell lines analyzed, it was at least twice as high as compared to a control HeLa transfectant that expresses high levels of Cx43 at the cell membrane. Experiments performed in the presence of alpha-glycyrrhetinic acid or small interfering RNA confirmed that Cx43 was responsible for the GJIC and the BE. Our results indicate for the first time that the very limited numbers of gap junctions present in glioblastoma cells are highly functional. We thus conclude that the TK/GCV strategy is still a valuable therapeutic option to be developed for the treatment of glioblastoma patients.
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PMID:Bystander effect in glioblastoma cells with a predominant cytoplasmic localization of connexin43. 1860 Feb 56

Hypoxia contributes to the resistance of tumors to conventional therapies. We hypothesized that their replication in hypoxic environments like brain or oral mucosa would make oncolytic herpes simplex viruses (HSVs) such as G207 (which has undergone clinical trials) replicate to a greater extent in hypoxic tumors like glioblastoma. Hypoxic cultured U87 cells yielded 4% more wild-type HSV (P = 0.04) and 3.6-fold more G207 (P = 0.001) after 48 hours of infection when compared with normoxic cells. Real-time RT-PCR confirmed a fivefold hypoxia-induced U87 upregulation of GADD34 mRNA, a factor complementing the gamma34.5 gene deletion in G207. The viral yield under conditions of hypoxia, as against normoxia, in GADD34 siRNA-treated U87 cells was 65% of that in control siRNA-treated cells. Treating subcutaneous U87 tumors in athymic mice with erythropoietin lowered the tumoral hypoxic fraction from 57.5 to 24.5%. Tumoral hypoxia dropped to 2.5% during 4 hours/day of hyperbaric chamber treatment. Each tumor-oxygenating maneuver reduced the G207 yield fourfold (P = 0.0001). Oncolytic HSV G207 exhibited enhanced replication in hypoxic environments, partly on account of increased GADD34 expression in hypoxic cells. The unique tropism of oncolytic HSVs for hypoxic environments contrasts with the hypoxia-mediated impairment of standard (radiation, chemotherapy) and other experimental therapies, and enhances HSV's appeal and efficacy in treating tumors like glioblastoma.
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PMID:Hypoxia enhances the replication of oncolytic herpes simplex virus. 1895 63

Transcriptional targeting of viral genes is a promising strategy to achieve tumor-specific replication of oncolytic viruses. Due to its natural tropism, herpes simplex virus type 1 (HSV-1) may be an ideal tool for oncolytic therapy of brain tumors such as malignant glioblastoma. To study whether glioma-specific gene expression can be accomplished within the HSV-1 genome, four cellular regulatory elements were exemplarily studied. Whereas the human telomerase reverse transcriptase (hTERT) and survivin promoters and the nestin and vascular endothelial growth factor A (VEGF-A) enhancers displayed pronounced glioma specificity after plasmid transfection, only the nestin enhancer conferred a certain selectivity for glioma cells and notable activity when transferred into the viral genome. The nestin enhancer was also found to be highly useful for tumor cell-specific expression of a therapeutically relevant gene (interleukin-2) when tested in combination with the hTERT or simian virus 40 (SV40) early promoter in the HSV-1 genome. Because activity of the chosen promoter in a tumor is a prerequisite for the successful application of an oncolytic virus, we examined whether the activity of a promoter can be deduced from the amounts of cellular mRNA or protein expressed under its control. We found little correlation between promoter activity and mRNA levels of the corresponding gene, whereas protein expression was more closely related to promoter activity. We conclude that the cellular elements are differently regulated in the viral and cellular genomes. Mechanistic insight into the differential regulation is required to improve and refine the design of transcriptionally targeted HSV vectors.
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PMID:Tumor-specific activity of cellular regulatory elements is down-regulated upon insertion into the herpes simplex virus genome. 1897 78

Achievement of specific tumor cell targeting remains a challenge for glioma gene therapy. We observed that the human high mobility group box2 (HMGB2) gene had a low level of expression in normal human brain tissues, but was significantly upregulated in glioblastoma tissues. With progressive truncation of a 5'-upstream sequence of the HMGB2 gene, we identified a 0.5-kb fragment displaying a high transcriptional activity in glioblastoma cells, but a low activity in normal brain cells. To test the feasibility of using the HMGB2 promoter sequence in targeted cancer therapy, we constructed a baculoviral vector expressing the herpes simplex virus thymidine kinase (HSVtk) gene driven by the HMGB2 promoter. Transduction with the viral vector induced cell death in glioblastoma cell lines in the presence of ganciclovir (GCV), but did not affect the survival of human astrocytes and neurons. In a mouse xenograft model, intratumor injection of the baculoviral vector suppressed the growth of human glioblastoma cells and prolonged the survival of tumor-bearing mice. Our results suggest that the novel 5' sequence of HMGB2 gene has a potential to be used as an efficient, tumor-selective promoter in targeted vectors for glioblastoma gene therapy.
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PMID:High mobility group box2 promoter-controlled suicide gene expression enables targeted glioblastoma treatment. 1924 Jun 92

Suicide gene therapy with herpes simplex virus thymidine kinase (HSV-TK) and ganciclovir (GCV) is notable for producing multi-log cytotoxicity in a unique pattern of delayed cytotoxicity in S-phase. As hydroxyurea, a ribonucleotide reductase inhibitor that activates mismatch repair, can increase sensitivity to GCV, we evaluated the role of MLH1, an essential mismatch repair protein, in GCV cytotoxicity. Using HCT116TK (HSV-TK-expressing) colon carcinoma cells that express or lack MLH1, cell-survival studies demonstrated greater GCV sensitivity in the MLH1-deficient cells, primarily at high concentrations. This could not be explained by differences in GCV metabolism, as the less sensitive MLH1-expresssing cells accumulated more GCV triphosphate and incorporated more of the analog into DNA. SiRNA suppression of MLH1 in U251 glioblastoma or SW480 colon carcinoma cells also enhanced sensitivity to high concentrations of GCV. Studies in a pa nel of yeast deletion mutants confirmed the results with MLH1, and further suggested a role for homologous recombination repair and several cell-cycle checkpoint proteins in GCV cytotoxicity. These data suggest that MLH1 can prevent cytotoxicity with GCV. Targeting mismatch repair-deficient tumors may increase efficacy of this suicide gene therapy approach to cancer treatment.
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PMID:MLH1 deficiency enhances tumor cell sensitivity to ganciclovir. 1930 Apr 72

Glioblastoma multiforme is one of the most common human brain tumors. The tumor is generally highly infiltrative, making it extremely difficult to treat by surgical resection or radiotherapy. This feature contributes to recurrence and a very poor prognosis. Few anticancer drugs have been shown to alter rapid tumor growth and none are ultimately effective. Oncolytic vectors have been employed as a treatment alternative based on the ability to tailor virus replication to tumor cells. The human neurotropic herpes simplex virus (HSV) is especially attractive for development of oncolytic vectors (oHSV) because this virus is highly infectious, replicates rapidly and can be readily modified to achieve vector attenuation in normal brain tissue. Tumor specificity can be achieved by deleting viral genes that are only required for virus replication in normal cells and permit mutant virus replication selectively in tumor cells. The anti-tumor activity of oHSV can be enhanced by arming the vector with genes that either activate chemotherapeutic drugs within the tumor tissue or promote anti-tumor immunity. In this review, we describe current designs of oHSV and the experience thus far with their potential utility for glioblastoma therapy. In addition, we discuss the impediments to vector effectiveness and describe our view of future developments in vector improvement.
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PMID:Design and application of oncolytic HSV vectors for glioblastoma therapy. 1934 2

Glioblastoma, the most malignant type of primary brain tumor, is one of the solid cancers where cancer stem cells have been isolated, and studies have suggested resistance of those cells to chemotherapy and radiotherapy. Here, we report the establishment of CSC-enriched cultures derived from human glioblastoma specimens. They grew as neurospheres in serum-free medium with epidermal growth factor and fibroblast growth factor 2, varied in the level of CD133 expression and very efficiently formed highly invasive and/or vascular tumors upon intracerebral implantation into immunodeficient mice. As a novel therapeutic strategy for glioblastoma-derived cancer stem-like cells (GBM-SC), we have tested oncolytic herpes simplex virus (oHSV) vectors. We show that although ICP6 (UL39)-deleted mutants kill GBM-SCs as efficiently as wild-type HSV, the deletion of gamma34.5 significantly attenuated the vectors due to poor replication. However, this was significantly reversed by the additional deletion of alpha47. Infection with oHSV G47Delta (ICP6(-), gamma34.5(-), alpha47(-)) not only killed GBM-SCs but also inhibited their self-renewal as evidenced by the inability of viable cells to form secondary tumor spheres. Importantly, despite the highly invasive nature of the intracerebral tumors generated by GBM-SCs, intratumoral injection of G47Delta significantly prolonged survival. These results for the first time show the efficacy of oHSV against human GBM-SCs, and correlate this cytotoxic property with specific oHSV mutations. This is important for designing new oHSV vectors and clinical trials. Moreover, the new glioma models described in this study provide powerful tools for testing experimental therapeutics and studying invasion and angiogenesis.
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PMID:Human glioblastoma-derived cancer stem cells: establishment of invasive glioma models and treatment with oncolytic herpes simplex virus vectors. 1935 38

Mesenchymal stem cells (MSCs) have been expected to become useful gene delivery vehicles against human malignant gliomas when coupled with an appropriate vector system, because they migrate towards the lesion. Human artificial chromosomes (HACs) are non-integrating vectors with several advantages for gene therapy, namely, no limitations on the size and number of genes that can be inserted. We investigated the migration of human immortalized MSCs bearing a HAC vector containing the herpes simplex virus thymidine kinase gene (HAC-tk-hiMSCs) towards malignant gliomas in vivo. Red fluorescence protein-labeled human glioblastoma HTB14 cells were implanted into a subcortical region in nude mice. Four days later, green fluorescence protein-labeled HAC-tk-hiMSCs were injected into a contralateral subcortical region (the HTB14/HAC-tk-hiMSC injection model). Tropism to the glioma mass and the route of migration were visualized by fluorescence microscopy and immunohistochemical staining. HAC-tk-hiMSCs began to migrate toward the HTB14 glioma area via the corpus callosum on day 4, and gathered around the HTB14 glioma mass on day 7. To test whether the delivered gene could effectively treat glioblastoma in vivo, HTB14/HAC-tk-hiMSC injected mice were treated with ganciclovir (GCV) or PBS. The HTB14 glioma mass was significantly reduced by GCV treatment in mice injected with HAC-tk-hiMSCs. It was confirmed that gene delivery by our HAC-hiMSC system was effective after migration of MSCs to the glioma mass in vivo. Therefore, MSCs containing HACs carrying an anticancer gene or genes may provide a new tool for the treatment of malignant gliomas and possibly of other tumor types.
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PMID:A gene delivery system with a human artificial chromosome vector based on migration of mesenchymal stem cells towards human glioblastoma HTB14 cells. 1958 5


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