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Biomedical subjects

E A Chiocca

Publications and source records attributed to E A Chiocca.

At least 55 records · Page 3Linked to original sources
PubMed1999

Inhibition of NF2-negative and NF2-positive primary human meningioma cell proliferation by overexpression of merlin due to vector-mediated gene transfer.

OBJECT: The absence of in vitro models of neurofibromatosis Type 2 (NF2)-defective meningiomas has limited investigative efforts to study the biological effects of this gene in the pathogenesis of these tumors. The goals of this report are to show that gene transfer vectors can efficiently express the wild-type NF2 transgene into primary meningioma cells and to determine effects on cellular proliferation. METHODS: In this study, the authors have compared the transducing capacities of a retrovirus, an adenovirus, and a herpes simplex virus amplicon vector for use in primary human meningioma cells harvested from human tumors excised from patients with and without NF2. Transduction efficiencies with the latter vector approached 100% and it was selected to transfer the wild-type NF2 transgene into these cells. Western blot analysis confirmed that vector-mediated gene transfer mediated the expression of the NF2-encoded polypeptide merlin. Overexpression of merlin significantly inhibited the proliferation of both NF2-negative and NF2-positive human meningioma cells when compared to the proliferation of cells transduced with a control vector. CONCLUSIONS: This study demonstrates the feasibility of using vector-mediated gene transfer to study wild-type NF2 gene function in short-term cultures of primary human meningioma cells.

Apoptosis↗
PubMed1999

A review of gene therapy for the treatment of central nervous system tumors.

The transfer of genes into tumors of the central nervous system has been touted as a novel treatment. However, several scientific and technological hurdles will have to be resolved before such strategies become useful clinical tools. This review summarizes the current knowledge in the field. Some of the gene delivery vectors employed both preclinically and clinically are those based on retroviruses, herpes simplex viruses, adenoviruses, adeno-associated viruses, and reoviruses. Cells such as fibroblasts and neural progenitor cells may also provide therapeutic value. These vectors are used to deliver into the tumor cell a variety of anticancer genes, such as those that activate chemotherapy agents, increase tumor immunogenicity, modulate tumor apoptosis and/or angiogenesis. One of the issues confronting such therapeutic strategies revolves around the blood-brain-barrier that may limit the penetration of vectors and genes form the circulation into the tumor. Results from a variety of clinical trials are becoming available. While the safety of this treatment strategy appears to have been established, therapeutic efficacy has been lacking. Additional refinements in the basic technology of vector construction and further understanding of the basic biology of gene transfer and expression will help in establishing gene therapy as clinically useful against brain tumors.

Animals↗
PubMed1998

Herpes simplex virus type 1 DNA amplified as bacterial artificial chromosome in Escherichia coli: rescue of replication-competent virus progeny and packaging of amplicon vectors.

Herpes simplex virus type 1 (HSV-1)-based amplicon vectors contain only approximately 1% of the 152-kb HSV-1 genome, and consequently, replication and packaging into virions depends on helper functions. These helper functions have been provided conventionally by a helper virus, usually a replication-defective mutant of HSV-1, or more recently, by a set of five cosmids that overlap and represent the genome of HSV-1 deleted for DNA cleavage/packaging signals (pac). In the absence of pac signals, potential HSV-1 genomes that are reconstituted from the cosmids via homologous recombination are not packageable. The resulting amplicon stocks are, therefore, virtually free of contaminating helper virus. To simplify this packing system, the HSV-1 genome was cloned and maintained stably as a single-copy, F plasmid-based bacterial artificial chromosome in E. coli. Such a plasmid containing the HSV-1 genome deleted for the pac signals (fHSV delta pac) did not generate replication-competent progeny virus on transfection into mammalian cells, but rather, it was able to support the packaging of cotransfected amplicon DNA that contained a functional pac signal. The resulting amplicon vector stocks had titers of up to 10(7) transducing units per milliliter of culture medium and efficiently transduced neural cells in the rat brain, as well as hepatocytes in the rat. The capacity of generating infectious and replication-competent HSV-1 progeny following transfection into mammalian cells was restored after insertion of a pac signal into fHSV delta pac.

Animals↗
PubMed1998

New prodrug activation gene therapy for cancer using cytochrome P450 4B1 and 2-aminoanthracene/4-ipomeanol.

Vector-mediated transfer of prodrug-activating genes provides a promising means of cancer gene therapy. In a search for more selective and more potent bioactivating enzymes for gene therapy of malignant brain tumors, the toxicity-generating capacity of the rabbit cytochrome P450 isozyme CYP4B1 was investigated. Rabbit CYP4B1, but not rat or human isozymes, efficiently converts the inert prodrugs, 2-aminoanthracene (2-AA) and 4-ipomeanol (4-IM), into highly toxic alkylating metabolites. Toxicity of these two prodrugs was evaluated in culture in parental and genetically modified rodent (9L) and human (U87) glioma cell lines stably expressing CYP4B1, and in vivo in a subcutaneous 9L tumor model in nude mice. The most sensitive CYP4B1-expressing glioma clone, 9L4B1-60, displayed an LD50 of 2.5 microM for 2-AA and 4-IM after 48 h of prodrug incubation, whereas 20 times higher prodrug concentrations did not cause any significant toxicity to control cells. Substantial killing of control tumor cells by 2-AA was achieved by co-culturing these cells with CYP4B1-expressing cells at a ratio of 100:1, and toxic metabolites could be transferred through medium. In both CYP4B1-expressing cells and co-cultured control cells, prodrug bioactivation was associated with DNA fragmentation, as assayed by fluorescent TUNEL assays and by annexin V staining. Alkaline elution of cellular DNA after exposure to 4-IM revealed extensive protein-DNA crosslinking with single-strand breakage. Growth of 9L-4B1 tumors in nude mice was inhibited by intraperitoneal injection of 4-IM with minimal side effects. Potential advantages of the CYP4B1 gene therapy paradigm include: the low concentrations of prodrug needed to kill sensitized tumor cells; low prodrug conversion by human isozymes, thus reducing toxicity to normal cells; a tumor-killing bystander effect that can occur even without cell-to-cell contact; and the utilization of lipophilic prodrugs that can penetrate the blood-brain barrier.

Animals↗
PubMed1998

Measuring transferrin receptor gene expression by NMR imaging.

The human transferrin receptor (hTfR) has been used as a model molecular target to direct therapeutic agents to tumor cells and to shuttle drugs across the blood-brain-barrier. We show in the current study that receptor expression and regulation can be visualized by NMR imaging, when the receptor is probed with a sterically protected iron containing magnetic hTfR probe. We were able to demonstrate that the novel receptor probe was an iron source that could enter the cells via the hTfR but did not play an immediate role in iron downregulation of hTfR within incubation times tested. Using genetically engineered rat 9L gliosarcoma cell lines with three different forms of the hTfR, we also demonstrated that receptor expression and regulation can be visualized by NMR imaging using the probe. This research provides proof of the principle that it is possible to image receptor gene expression and regulation and it demonstrates that it may be possible to image gene transfer in vivo.

Animals↗
PubMed1998

Synergistic anticancer effects of ganciclovir/thymidine kinase and 5-fluorocytosine/cytosine deaminase gene therapies.

BACKGROUND: A bacterial enzyme, Escherichia coli cytosine deaminase, which converts the prodrug 5-fluorocytosine into the toxic drug 5-fluorouracil, and a viral enzyme, herpes simplex virus thymidine kinase, which converts ganciclovir from an inactive prodrug to a cytotoxic agent by phosphorylation, are being actively investigated for use in gene therapy for cancer. The purpose of this study was to determine whether combining these prodrug-activating gene therapies might result in enhanced anticancer effects. METHODS: Rat 9L gliosarcoma cells were transfected with plasmids containing the E. coli cytosine deaminase gene (9L/CD cells), with plasmids containing the herpes simplex virus thymidine kinase gene (9L/TK cells), or with both expression plasmids (9L/CD-TK cells). The drug sensitivities of the cell lines were evaluated; in addition, the sensitivities of 9L and 9L/CD-TK cells mixed in varied proportions were measured. The effects of prodrug treatment on 9L/CD-TK tumor growth (i.e., size and volume) in nude mice were monitored. The isobologram method of Loewe and the multiple drug-effect analysis method of Chou-Talalay were used to measure the interaction between the two prodrug-activating gene therapies. To elucidate the mechanism of interaction, the phosphorylation of ganciclovir in 9L/CD-TK cells after varying prodrug treatments was studied. RESULTS AND CONCLUSIONS: The presence of transfected cytosine deaminase and thymidine kinase genes in 9L gliosarcoma cells reduced cell survival, both in vitro and in vivo, following treatment with the relevant prodrugs; the effects of the two components appeared to be synergistic and related mechanistically to the enhancement of ganciclovir phosphorylation by thymidine kinase following 5-fluorouracil treatment.

Animals↗
PubMed1998

A chimeric fusion protein of cytochrome CYP4B1 and green fluorescent protein for detection of pro-drug activating gene delivery and for gene therapy in malignant glioma.

Quantity and distribution of transgene-expressing tumor cells are central issues in cancer gene therapy. These are critical for the efficiency of tumor killing and for the bystander effect. In an attempt to combine the advantages of a potent bioactivating "suicide" gene with a marker gene for living cells, cDNA encoding cytochrome CYP4B1 was fused to the green fluorescent protein (GFP) cDNA. The resulting chimeric fusion protein, 4B1EGFP, was expressed in rodent and human glioma cell lines in culture. The ability of this recombinant enzyme to destroy tumor cells by converting the prodrug 4-ipomeanol (4-IM) into alkylating metabolites was evaluated in comparison with the cytotoxicity of the native CYP4B1 enzyme. The most sensitive 4B1EGFP-expressing glioma cell clone had a LD50 of 0.75 microgram/ml for 4-IM, as compared to a 4-IM LD50 of 0.5 microgram/ml in glioma cells expressing the native CYP4B1. A strong bystander effect mediated by cell-to-cell contact was present in the 4B1EGFP clones, allowing for more than 50% bystander kill at a ratio of expressing to non-expressing cells of 1:100. A herpes-simplex amplicon (pHSVPrPUC delta Hind) was constructed with the 4B1EGFP fusion protein, and recombinant helper-free HSV particles were packaged in Vero cells. Fisher 344 rats were inoculated with 4 x 10(5) 9L tumor cells to produce epidural tumor. Recombinant HSV particles were injected into the tumor at a dose of 1 x 10(7) pfu. Tumor was resected in living anesthetized animals 24, 48, and 72 hours after virus injection, and cryostat sections were evaluated by fluorescent microscopy. HSV-mediated delivery of the fusion protein to tumor cells was successfully demonstrated. In conclusion, the chimeric fusion protein 4B1EGFP retains essentially all features of the native CYP4B1 enzyme, and, moreover, offers advantages in terms of gene transfer visualization, which may lead to improvement of gene transfer strategies.

Animals↗
PubMed1998

Co-expression of Fas and Fas ligand in malignant glial tumors and cell lines.

Fas ligand (FasL) is involved in tumor evasion from the immune system. We analyzed 22 human gliomas for expression of FasL and its receptor, Fas. Positive FasL and Fas immunoreactivity was detected in 13 out of 22 tumors by Western blotting and in 15 out of 22 tumors by immunohistochemistry. Immunohistochemistry also showed that Fas and FasL expression was confined to tumor cells. Co-expression of these molecules was confirmed by Western blotting and immunohistochemistry in 4 of 7 glioma cell lines. Co-expression of FasL and Fas within tumor cells suggests that their contribution in vivo to the process of immune system evasion and tumor cell apoptosis is complex and probably involves additional factors.

Astrocytoma↗
PubMed1998

An oncolytic viral mutant that delivers the CYP2B1 transgene and augments cyclophosphamide chemotherapy.

Herpes simplex viruses type 1 (HSV-1) with an inactivated viral ribonucleotide reductase (Hsrr, ICP6) were designed to target tumor cells with upregulated mammalian ribonucleotide reductase (mRR), an enzyme whose expression is regulated by the p16/pRB tumor suppressor pathway. A recombinant HSV-1 was generated by knock-out of Hsrr and insertion of the rat CYP2B1 transgene responsible for the bioactivation of the prodrugs, cyclophosphamide and ifosfamide. The mutant virus replicated selectively in rat and human tumor cells that express mRR. Addition of cyclophosphamide potentiated oncolytic effects against cultured tumor cells and subcutaneous tumor xenografts established in athymic mice.

Animals↗
PubMed1998

Pre-existing herpes simplex virus 1 (HSV-1) immunity decreases, but does not abolish, gene transfer to experimental brain tumors by a HSV-1 vector.

The influence of pre-existing anti-herpes simplex type 1 (HSV-1) immunity on HSV-1 vector-mediated gene transfer to glioma cells was analyzed in this gene marking study using intracranial D74 gliomas in syngeneic Fischer rats. The HSV-1 mutant virus used, hrR3, is defective in ribonucleotide reductase and bears the marker genes E. coli lacZ and HSV-1 thymidine kinase (HSVtk). Initial marker gene expression in tumors 12 h after direct virus injection was reduced in immunized animals to about 15% of that in nonimmunized animals. Marker gene expression in both sets stayed at initial levels for 2 days after intratumoral injection and declined markedly on day 5. Inflammatory infiltrates in the tumor were more prominent in HSV-1-immunized, as compared with nonimmunized animals, at 12 and 24 h, but appeared similar at 2-5 days after injection. By day 10, the immune reaction had subsided in immunized animals and macrophages remained only in nonimmunized animals. In conclusion, gene transfer to brain tumors using a HSV-1 vector was greatly reduced, but not completely abolished, under pre-immunization conditions. Pre-existing antibodies to HSV-1 may also serve a positive role in providing an increased margin of safety in intracranial application of HSV-1 vectors by limiting spread of the virus within the brain and to other tissues.

Animals↗
PubMed1998

Cancer gene therapy using a replication-competent herpes simplex virus type 1 vector.

OBJECTIVE: The authors investigate the efficacy of hrR3, a viral vector derived from herpes simplex virus type 1 (HSV 1), in destroying colon carcinoma cells in vitro and in vivo. The effect of adding the prodrug ganciclovir in combination with hrR3 infection also is assessed. SUMMARY BACKGROUND DATA: Most cancer gene therapy strategies use viral vectors that are incapable of replication. The HSV 1 vector hrR3 is capable of replication, and its replication is cytotoxic to cells. hrR3 also possesses the HSV-thymidine kinase gene, which converts ganciclovir into a toxic metabolite. Thus, the addition of ganciclovir to hrR3-infected cells may enhance the ability of hrR3 to destroy tumor cells. To increase specificity for tumor cells, hrR3 has a mutated ribonucleotide reductase gene and replicates selectively in cells with high levels of endogenous rbonucleotide reductase. Actively dividing cells such as tumor cells have high levels of endogenous ribonucleotide reductase for synthesis of DNA precursors. The authors are interested in the use of HSV 1 vectors to treat liver metastases from colorectal cancer. METHODS: Ribonucleotide reductase expression in several colon carcinoma cell lines and in primary cultures of human hepatocytes was determined by Western blot analysis. hrR3-mediated cytotoxicity in the colon carcinoma cell lines was determined using an in vitro assay. The human colon carcinoma cell line HT29 was injected into the flanks of nude mice followed by intratumoral injection of hrR3. Tumor growth rate was assessed with and without the addition of intraperitoneal ganciclovir. RESULTS: Ribonucleotide reductase levels in colon carcinoma cell lines are much higher than in primary cultures of human hepatocytes. hrR3 efficiently destroys colon carcinoma cell lines in vitro. A single intratumoral injection of hrR3 into HT29 flank tumors significantly reduces tumor growth rate, and the administration of ganciclovir has no additive effect. CONCLUSIONS: The inherent cytotoxicity of hrR3 replication effectively destroys colon carcinoma cells in vitro and in vivo. This cytotoxicity is not enhanced in vivo by the addition of ganciclovir. In the future, more efficacious and selective HSV 1 vectors may be useful in the treatment of cancer.

Animals↗
PubMed1998

Marker gene transfer and oncolysis of human Y79 retinoblastoma cells mediated by herpes simplex virus mutants.

Three different herpes simplex virus (HSV) mutants, designated hrR3, MGH-1 and R3616, were used to infect Y79 retinoblastoma cells grown in suspension. Two parameters were assayed: (a) vector-mediated gene expression, measured by histochemical staining of a transferred LacZ transgene, and (b) virus-mediated oncolysis, determined by the inability of infected cells to exclude trypan blue dye. The tested HSV mutants were found to infect cells grown in suspension at a relatively low multiplicity of infection (MOI = 0.01) and were capable of transferring the LacZ gene as early as 2 days after infection. Furthermore, differences in oncolytic activity were observed amongst the tested viruses: MGH-1 and R3616 exhibited 50% cell kill at a MOI of 0.1 over a period of 6 days, whereas hrR3-mediated oncolysis appeared less efficient. These studies provide a rationale for further exploitation of oncolytic herpes viruses as a potential treatment of intraocular tumors.

Cell Death↗
PubMed1998

Effects on brain tumor cell proliferation by an adenovirus vector that bears the interleukin-4 gene.

A recombinant adenovirus vector bearing the IL-4 gene (AD-IL-4) was used to infect rat glioma C6 cells in culture at multiplicity of infections (MOI) from 50 to 1800. C6 cell proliferation was not altered significantly by adenoviral infection. However, IL-4 production increased in a dose-dependent manner. To ascertain effects on in vivo cell proliferation, a subcutaneous tumor model was used. Rat C6 glioma cells alone or C6 mixed with the control virus bearing the LacZ gene (Ad-LacZ) produced tumors that measured an average of approximately 3000 mm3 35 days after implantation. In contrast, C6 cells mixed with Ad-IL-4 produced significant inhibition of tumor growth (P=0.035 compared to C6 tumor; P=0.023 compared to C6+Ad-LacZ tumor. Student's ttest). IL-4 levels in mice serum were measured by ELISA and reached a peak of approximately 700 pg/ml at 14 days. These preliminary results showed that adenovirus-mediated delivery of the IL-4 gene may result in a significant inhibition of rat C6 cell tumor growth. Further studies will be necessary to refine this anti-tumor effect for as a potential therapy for cancer.

Adenoviridae↗
PubMed1998

Gene therapy for tumors of the central nervous system.

Primary central nervous system tumors, consisting mainly of malignant gliomas, represent a unique system for the study of gene transfer techniques. Exogenous transgenes have been delivered using retroviral, adenoviral, and herpes simplex virus vectors. A number of strategies have been developed, including: (1) delivery of prodrug activating genes, (2) replacement of tumor suppressor genes, (3) cytokine-mediated enhancement of antitumor immune responses, and (4) antisense cDNA delivery to block the action of growth factors, cell cycle proteins, and drug resistance mechanisms. Efforts to disrupt the blood brain barrier may facilitate tumor gene delivery.

Central Nervous System Neoplasms↗
PubMed1997

Regression of experimental brain tumors with 6-thioxanthine and Escherichia coli gpt gene therapy.

The identification of transgenes with antitumor activity is critical to the development of gene therapy of cancer. Retrovirus-mediated transfer of the Escherichia coli gpt gene into rat C6 glioma cells without subsequent selection still inhibited the proliferation of this mixed polyclonal population upon addition of the prodrug, 6-thioxanthine, with an ID50 of 4.1 microM, whereas parental C6 cells were not affected at a concentration of 500 microM. In a time-course assay, effects of the prodrug on the mixed polyclonal cell proliferation required at least 10 days of exposure. In mixed co-cultures, a bystander effect was not present over the first 4 days of prodrug exposure, but required trypsinization of the co-cultures and replating at lower densities. This "modified" bystander assay thus revealed a 50% decrease in C6 cell proliferation, even when the initial ratio of gpt-expressing to parental C6 cells was as low as 1:19. In a nude mouse model of subcutaneous tumors, co-grafts of C6 glioma and gpt-retrovirus producer cells displayed retarded growth upon exposure to 6-thioxanthine (6-TX). In a nude mouse model of intracerebral tumors, grafting of the gpt-retrovirus producer cells leads to an 80% reduction in intracerebral tumor volumes after 6-TX treatment. This reduction results in a 28% increase in the mean time of survival of animals that harbor intracerebral tumors (p < 0.0005). These antitumor effects indicate that the gpt/6-TX enzyme/prodrug pair is a promising alternative to the thymidine kinase gene and ganciclovir combination in the gene therapy of cancer.

Animals↗
PubMed1997

Therapeutic efficiency and safety of a second-generation replication-conditional HSV1 vector for brain tumor gene therapy.

A second-generation replication-conditional herpes simplex virus type 1 (HSV) vector defective for both ribonucleotide reductase (RR) and the neurovirulence factor gamma34.5 was generated and tested for therapeutic safety and efficiency in two different experimental brain tumor models. In culture, cytotoxic activity of this double mutant HSV vector, MGH-1, for 9L gliosarcoma cells was similar to that of the HSV mutant, R3616, which is defective only for gamma34.5, but was significantly weaker than that of the HSV mutant hrR3, which is defective only for RR. The diminished tumoricidal effect of the gamma34.5 mutants could be accounted for by their reduced ability to replicate in 9L cells. The MGH-1 vector did not achieve significant prolongation of survival in vivo in the syngeneic 9L rat gliosarcoma model for either single brain tumor focus or multiple intracerebral and leptomeningeal tumors, when the vector was applied intratumorally or intrathecally, respectively, and with or without subsequent ganciclovir (GCV) treatment. In identical 9L brain tumor models with single and multiple foci, application of hrR3 with or without GCV was previously shown to result in marked long-term survival. Contrary to the findings with intrathecal injection of hrR3, no vector-related mortality was observed in any animals treated with MGH-1. Thus, in these rat brain tumor models, the double mutant, replication-conditional HSV vector MGH-1 showed a higher therapeutic safety than the RR-minus vector, hrR3, but had clearly decreased therapeutic efficiency compared to hrR3. The development of new HSV vectors for brain tumor gene therapy will require a balance between maximizing therapeutic efficacy and minimizing toxicity to the brain. Standardized application in brain tumor models as presented here will help to screen new HSV vectors for these requirements.

Animals↗