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PubMed2003

Development of genetically engineered human intestinal cells for regulated insulin secretion using rAAV-mediated gene transfer.

Cell-based therapies for treating insulin-dependent diabetes (IDD) can provide a more physiologic regulation of blood glucose levels in a less invasive fashion than daily insulin injections. Promising cells include intestinal enteroendocrine cells genetically engineered to secrete insulin in response to physiologic stimuli; responsiveness occurs at the exocytosis level to regulate the acute release of recombinant insulin. In this work, we established a human cellular model to demonstrate that meat hydrolysate can simultaneously stimulate glucagon-like peptide-1 (GLP-1, an enteroendocrine cell-derived incretin hormone) and recombinant insulin secretion from the engineered human NCI-H716 intestinal cell line. Cells were genetically modified using the recombinant adeno-associated virus (rAAV)-mediated insulin gene transfer. Recombinant cells were then differentiated to display endocrine features, in particular the formation of granule-like compartments. A fusion protein of insulin and enhanced green fluorescence protein (EGFP) was designed to reveal the compartments of localization of the fusion protein and assess its co-localization with endogenous GLP-1. Our work provides a unique human cellular model for regulated insulin release through genetic engineering of GLP-1-secreting intestinal cells, which is expected to be useful for cell-based therapies of IDD.

Cell Line↗

PubMed1998

Artificial cells with emphasis on cell encapsulation of genetically engineered cells.

Artificial cells are prepared in the laboratory for medical and biotechnological applications. Encapsulated cells are being studied for the treatment of diabetes, liver failure, and other conditions. More recently, there have been extensive studies into the use of encapsulated genetically engineered cells for gene therapy. We recently found that daily orally administered artificial cells, each containing a genetically engineered microorganism, can lower the elevated urea level in uremic rats to normal levels. This may solve the final obstacle of the lack of an effective oral urea removal system for the simple and inexpensive oral treatment of uremia. This is important because 85% of the world's uremic population cannot afford standard dialysis. Other areas of artificial cell application include use in hemoperfusion. Red blood cell substitutes based on modified hemoglobin are already in Phase 3 clinical trials in patients. Artificial cells containing enzymes are being developed for clinical trial in hereditary enzyme deficiency disease and other diseases. They are also being investigated for drug delivery and for use in other applications in biotechnology, chemical engineering, and medicine.

Administration, Oral↗

PubMed2000

Genetic engineering of the Fusarium solani pisi lipase cutinase for enhanced partitioning in PEG-phosphate aqueous two-phase systems.

The Fusarium solani pisi lipase cutinase has been genetically engineered to investigate the influence of C-terminal peptide extensions on the partitioning of the enzyme in PEG-salt based aqueous two-phase bioseparation systems. Seven different cutinase lipase variants were constructed containing various C-terminal peptide extensions including tryptophan rich peptide tags ((WP)(2) and (WP)(4)), positively ((RP)(4)) and negatively ((DP)(4)) charged tags as well as combined tags with tryptophan together with either positively ((WPR)(4)) or negatively ((WPD)(4)) charged amino acids. The modified cutinase variants were stably produced in Escherichia coli as secreted to the periplasm from which they were efficiently purified by IgG-affinity chromatography employing an introduced N-terminal IgG-binding ZZ affinity fusion partner present in all variants. Partitioning experiments performed in a PEG 4000/sodium phosphate aqueous two-phase system showed that for variants containing either (WP)(2) or (WP)(4) peptide extensions, 10- to 70-fold increases in the partitioning to the PEG rich top-phase were obtained, when compared to the wild type enzyme. An increased partitioning was also seen for cutinase variants tagged with both tryptophans and charged amino acids, whereas the effect of solely charged peptide extensions was relatively small. In addition, when performing partitioning experiments from cell disintegrates, the (WP)(4)-tagged cutinase showed a similarly high PEG-phase partitioning, indicating that the effect from the peptide tag was unaffected by the background of the host proteins. Taken together, the results show that the partitioning of the recombinantly produced cutinase model enzyme could be significantly improved by relatively minor genetic engineering and that the effects observed for purified proteins are retained also in an authentic whole cell disintegrate system. The results presented should be of general interest also for the improvement of the partitioning properties of other industrially interesting proteins including bulk enzymes.

Base Sequence↗

PubMed1990

Transport of a genetically engineered Pseudomonas fluorescens strain through a soil microcosm.

Vertical soil microcosms flushed with groundwater were used to study the influence of water movement on survival and transport of a genetically engineered Pseudomonas fluorescens C5t strain through a loamy sand and a loam soil. Transport of cells introduced into the top 1 cm of the vertical soil microcosms was dependent on the flow rate of water and the number of times microcosms were flushed with groundwater. The presence of wheat roots growing downward in the microcosms contributed only slightly to the movement of P. fluorescens C5t cells to lower soil regions of the loamy sand microcosms, but enhanced downward transport in the loam microcosms. Furthermore, the introduced P. fluorescens C5t cells were detected in the effluent water samples even after three flushes of groundwater and 10 days of incubation. As evidenced by a comparison of counts from immunofluorescence and selective plating, nonculturable C5t cells occurred in day 10 soil and percolated water samples, primarily of the loamy sand microcosms. Vertical soil microcosms that use water movement may be useful in studying the survival and transport of genetically engineered bacteria in soil under a variety of conditions prior to field testing.

Colony Count, Microbial↗

PubMed1998

Genetic engineering of Serratia marcescens with bacterial hemoglobin gene: effects on growth, oxygen utilization, and cell size.

The bacterial hemoglobin from Vitreoscilla has been shown to increase growth yield and yield of genetically engineered product in Escherichia coli. To test the generality of this phenomenon, the approximately 560-bp bacterial (Vitreoscilla) hemoglobin gene (vgb) (including the native promoter), cloned into the vector pUC8 in two constructs containing about 1650 and 850 bp, respectively, of Vitreoscilla DNA downstream of vgb, was transformed into Serratia marcescens. After several transfers of the transformants on selective media, both plasmids became stable in this host and the resulting strains produced hemoglobin. Both transformants were compared, regarding growth in liquid Luria-Bertani (LB) medium, with untransformed S. marcescens and S. marcescens transformed with pUC8. The vgb-bearing strains had about 5 times lower maximum viable cell numbers than the strains without hemoglobin, but the former also had late log or early stationary phase cells that were 5-10 times larger than those of the latter. Further, on a dry cell mass basis the presence of vgb inhibited cell growth in liquid media. In contrast, growth of the vgb-bearing strains on LB plates based on cell mass (determined from colony size) was markedly enhanced compared with that of the pUC8 transformant. Respiration of the vgb-bearing strains was lower than that of the strains without vgb on a cell mass basis. These results show that the presence of vgb can have idiosyncratic effects and is not always an aid to cell growth so that its use for genetic engineering must be tested on a case by case basis.

Bacterial Proteins↗

PubMed1991

The use of genetically engineered V79 Chinese hamster cultures expressing rat liver CYP1A1, 1A2 and 2B1 cDNAs in micronucleus assays.

We have undertaken a comparative study of the bioactivation of a panel of promutagens by V79 Chinese hamster cells genetically engineered to metabolic competence. In vitro micronucleus assays of the test agents in V79 cultures in the presence of an Aroclor induced rat S9 yielded positive results. In the genetically engineered cell lines, benzo[a]pyrene was metabolized specifically by the 3-methylcholanthrene inducible rat liver CYP1A1 (cell line XEM2) whereas cyclophosphamide increased the micronucleus frequency only in cultures expressing the phenobarbital inducible CYP2B1 (SD1). Following exposure to the mycotoxin sterigmatocystin, elevated frequencies of micronucleated cells were recorded in XEM2, SD1 and XEMd-MZ (expresses the isosafrole inducible CYP1A2) cells. The aromatic amine 2-amino-anthracene elicited a weak response in the cell line XEMd-MZ which expressed CYP1A2. This response was enhanced when this cDNA was expressed in a V79 variant cell strain which also possessed endogenous acetyltransferase activity. Upon exposure to tobacco particulate matter, a greater induction of micronuclei was observed in the XEM2 cell line compared to V79 cultures, implicating polycyclic aromatic hydrocarbons in addition to direct-acting compounds as causal agents in the genotoxicity of tobacco particulate matter. The cytokinesis blocked in vitro micronucleus assay provides a faster, simpler alternative to metaphase analysis, and kinetochore labelling techniques enable the discernment of both structural and numerical chromosome changes. The inclusion of metabolically competent test strains in the in vitro micronucleus assay therefore creates a powerful system for detecting genotoxins and may be extended to elucidate both mechanisms of bioactivation and modes of genotoxic insult.

Animals↗

PubMed2005

Science, law, and politics in FDA's genetically engineered foods policy: scientific concerns and uncertainties.

The Food and Drug Administration's (FDA's) 1992 policy statement granted genetically engineered foods presumptive GRAS (generally recognized as safe) status. Since then, divergent views have been expressed concerning the scientific support for this policy. This paper examines four sources to better understand the basis for these claims: 1) internal FDA correspondence; 2) reports from the National Academy of Sciences; 3) research funded by US Department of Agriculture from 1981 to 2002; and 4) FDA's proposed rules issued in 2001. These sources reveal that little research has been conducted on unintended compositional changes from genetic engineering. Profiling techniques now make this feasible, but the new debate centers on the functional meaning of compositional changes.

Consumer Product Safety↗

PubMed2005

Bystander effect-mediated gene therapy of gliomas using genetically engineered neural stem cells.

Since neural stem cells (NSCs) have the ability to migrate toward a tumor mass, genetically engineered NSCs were used for the treatment of gliomas. We first evaluated the "bystander effect" between NSCs transduced with the herpes simplex virus-thymidine kinase (HSVtk) gene (NSCtk) and C6 rat glioma cells under both in vitro and in vivo conditions. A potent bystander effect was observed in co-culture experiments of NSCtk and C6 cells. In the intracranial co-implantation experiments in athymic nude mice and Sprague-Dawley rats, the animals co-implanted with NSCtk and C6 cells and treated with ganciclovir (GCV) showed no intracranial tumors and survived more than 100 days, while those treated with physiological saline (PS) died of tumor progression. We next injected NSCtk cells into the pre-existing C6 tumor in rats and treated them with GCV or PS. The tumor volume was serially measured by magnetic resonance imaging. The tumor disappeared in six out of nine rats in the NSCtk/GCV group, while all the rats treated with PS died of tumor progression by day 21. The results indicate the feasibility of a novel gene therapy strategy for gliomas through a bystander effect generated by intratumoral injection of NSCtk cells and systemic GCV administration.

Animals↗

PubMed2002

Improving the pathogenicity of a nematode-trapping fungus by genetic engineering of a subtilisin with nematotoxic activity.

Nematophagous fungi are soil-living fungi that are used as biological control agents of plant and animal parasitic nematodes. Their potential could be improved by genetic engineering, but the lack of information about the molecular background of the infection has precluded this development. In this paper we report that a subtilisin-like extracellular serine protease designated PII is an important pathogenicity factor in the common nematode-trapping fungus Arthrobotrys oligospora. The transcript of PII was not detected during the early stages of infection (adhesion and penetration), but high levels were expressed concurrent with the killing and colonization of the nematode. Disruption of the PII gene by homologous recombination had a limited effect on the pathogenicity of the fungus. However, mutants containing additional copies of the PII gene developed a higher number of infection structures and had an increased speed of capturing and killing nematodes compared to the wild type. The paralyzing activity of PII was verified by demonstrating that a heterologous-produced PII (in Aspergillus niger) had a nematotoxic activity when added to free-living nematodes. The toxic activity of PII was significantly higher than that of other commercially available serine proteases. This is the first report showing that genetic engineering can be used to improve the pathogenicity of a nematode-trapping fungus. In the future it should be possible to express recombinant subtilisins with nematicidal activity in other organisms that are present in the habitat of parasitic nematodes (e.g., host plant).

Animals↗

PubMed2003

Genetically engineered tumor cell vaccine in a head and neck cancer model.

OBJECTIVES: Using a murine model, a novel tumor vaccine for head and neck squamous cell carcinoma expressing the granulocyte-macrophage colony stimulating factor (GM-CSF) gene was evaluated for its ability to protect against tumor challenge. STUDY DESIGN: Mice vaccinated in the floor of the mouth with the GM-CSF tumor cell vaccine were challenged with parental tumor cells, and subsequent tumor development was monitored. Specificity of the antitumor response was demonstrated by vaccinating the mice and then challenging them with an unrelated but syngeneic radiation-induced fibrosarcoma tumor cell line, RIF. Irradiated (only) tumor cells were used as a control to see whether an augmented antitumor response was attributable to possible increased immunogenicity that could theoretically be induced by the irradiation. METHODS: The GM-CSF gene was transduced into tumor cells via a retroviral vector. The tumor cells were irradiated to prevent replication in vivo. GM-CSF concentrations were determined using ELISA, and physiological activity was confirmed using a biological assay with a GM-CSF-dependent cell line. RESULTS: Vaccination with genetically engineered tumor cells significantly protected against subsequent tumor challenge (5% level) when compared to control groups. Mice were not protected when vaccinated and challenged with the unrelated tumor cell line, RIF. Mice vaccinated with irradiated (only) tumor cells were not protected, either. CONCLUSIONS: Vaccination with genetically engineered tumor cells offers significant protection from later tumor challenge. The response is systemic and tumor specific, not due to an inflammatory response. Irradiation of the tumor cells does not account for the augmented antitumor response. This work supports the continued investigation of the GM-CSF tumor vaccine for the treatment of head and neck squamous cell carcinoma.

Animals↗

PubMed2004

Genetically engineered mouse models for drug discovery: new chemical genetic approaches.

While standard transgenic and knockout mouse technologies have provided a wealth of information for target selection and validation, there have been great advances in using more sophisticated modeling techniques to achieve temporal and spatial regulation of individual genes in adult animals. Recent developments in RNA interference (RNAi) technology in in vivo models promise to further improve upon the static and irreversible features of gene knockouts. Chemical genetic approaches create novel functional alleles of targets and allow fine modulation of protein function in vivo by small molecules, providing the most pharmacologically relevant target validation. Using these advanced models, one can not only ask whether the function of the target is critical for the initiation and maintenance of the disease, but also whether therapies designed to alter the function of the target would be safe and efficacious. In this review, we describe various in vivo tools for target validation in mouse models, discuss advantages and disadvantages of each approach, and give examples of their impact on drug discovery.

Animals↗

PubMedDate not supplied

[An computer information system for genetic engineering].

The article describes the vectors data base and the software for its use (the VECTOR-PC system). At present the prototype versions of data base and VECTOR-PC exist and are in test exploitation. The original data base entry format contains 17 main fields for specific genetic engineering information. The VECTOR-PC system includes programs for data base search and support, and also the "genetic engineering designer", which allows the user to design his own hypothetic structures from the objects of data base and to receive detailed information about them. The system is destined for IBM PC or compatible computers.

Genetic Engineering↗

PubMed2001

Comparative effects of a genetically engineered insect virus and a growth-regulating insecticide on microbial communities in aquatic microcosms.

The effects of a genetically engineered insect baculovirus on indigenous aquatic microbial communities were determined in closed, recirculating aquatic microcosms, and compared with the effects of a natural strain of the virus and of a growth-regulating insecticide, Dimilin. The recombinant virus was a nuclear polyhedrosis virus (NPV) of the spruce budworm (Choristoneura fumiferana (Cf)) with a lacZ marker gene inserted into the egt region of the CfNPV. The natural virus was Ireland strain CfNPV. Microbial measurement endpoints included decomposition activity (mass loss of organic material), respiration on two different substrates (O2 consumption), heterotrophic bacterial abundance (plate counts), and microbial community metabolic profiles (carbon source utilization patterns in Biolog GN microplates). Viral DNA of both the natural strain and the recombinant viruses, detected by polymerase chain reaction techniques, settled out of the microcosm water and accumulated on bottom substrates within 3 days of the microcosm inoculations. The viral DNA persisted in bottom substrates for the duration of the 21-day experimental period, although there was some evidence that the recombinant virus was less stable than the natural strain in particulate organic matter. No significant changes in microbial decomposition or respiration activity, bacterial abundance, or average metabolic responses were detected by a time trend analysis in microcosms inoculated with either the lacZ recombinant virus or the natural Ireland strain CfNPV. Significant effects on microbial decomposition and respiration activity were detected in microcosms treated with the growth-regulating insecticide at, and above, the expected environmental concentrations. Despite significant effects on microbial community functional attributes in Dimilin-treated microcosms, there were no detectable changes in community structure in terms of metabolic profiles or bacterial abundance.

DNA, Viral↗

PubMedDate not supplied

Utilization of an alternative carbon source for efficient production of human alpha(1)-antitrypsin by genetically engineered rice cell culture.

Human alpha(1)-antitrypsin was produced by genetically engineered rice cells using promoter and signal peptide of a rice alpha-amylase isozyme. Batch and continuous cultures were employed to investigate the effects of alternative carbon sources on the alpha(1)-antitrypsin production. While this expression system is inducible by sugar depletion, we have found that the productivity of alpha(1)-antitrypsin increased 2.4- to 3.4-fold, compared with the control medium without carbon source, in medium containing an alternative carbon source, such as pyruvic acid and glyoxylic acid. The accumulated alpha(1)-antitrypsin in the medium containing pyruvic acid reached 18.2-24.2 mg/g-dry cell in 50-70 h by batch culture.

Carbon↗

PubMed1994

Human tumor vaccines and genetic engineering of tumors with cytokine and histocompatibility genes to enhance immunogenicity.

Genetically engineered tumor cells can be used as vaccines in order to stimulate an immune response. To date, tumor cells have been modified in vitro so that they secrete cytokines or express histocompatibility molecules that they naturally fail to express. These tumor cells differ in the types of immune responses they induce and in whether the responses have local or systemic efficacy. Many questions have been raised during the past year, including whether allogeneic or autologous tumor cells should be employed and whether there may be a risk of inducing autoimmune disease along with the antitumor response. Nevertheless, because of the paucity of available therapies for patients with advanced cancer, investigators must attempt to refine the approaches used in order to minimize patient risk while maximizing tumor cell destruction.

Cytokines↗

PubMed1995

Genetically engineered mammalian cells and applications.

In general, cells genetically engineered for stable and defined expression of xenobiotic-metabolizing enzymes are useful tools whenever a metabolism-related problem in toxicology and pharmacology is to be solved. It is the genetic and phenotypic nature of a given cell that determines its applicability. Mammalian cells have useful characteristics not given in bacterial, yeast or insect cells, which also may express xenobiotic-metabolizing enzymes. It is the problem to be solved and the question to be answered which determine the optimal choice for the best-suited expression system. There may even be subtle differences between mammalian cells of different species and organ origin, which might play a role in choosing a mammalian expression system. Thus, the level and specificity of the xenobiotic-metabolizing enzyme, the experimental testing conditions, and the biological endpoints present in a chosen cell are the most important criteria to be observed in the application of the mammalian expression systems.

Animals↗

PubMed1999

Modelling of genetically engineered microorganisms introduction in closed artificial microcosms.

The possibility of introducing genetically engineered microorganisms (GEM) into simple biotic cycles of laboratory water microcosms was investigated. The survival of the recombinant strain Escherichia coli Z905 (Apr, Lux+) in microcosms depends on the type of model ecosystems. During the absence of algae blooming in the model ecosystem, the part of plasmid-containing cells E. coli decreased fast, and the structure of the plasmid was also modified. In conditions of algae blooming (Ankistrodesmus sp.) an almost total maintenance of plasmid-containing cells was observed in E. coli population. A mathematics model of GEM's behavior in water ecosystems with different level of complexity has been formulated. Mechanisms causing the difference in luminescent exhibition of different species are discussed, and attempts are made to forecast the GEM's behavior in water ecosystems.

Animals↗

PubMed2006

Using genetically engineered mouse models of cancer to aid drug development: an industry perspective.

Recent developments in the generation and characterization of genetically engineered mouse models of human cancer have resulted in notable improvements in these models as platforms for preclinical target validation and experimental therapeutics. In this review, we enumerate the criteria used to assess the accuracy of various models with respect to human disease and provide some examples of their prognostic and therapeutic utility, focusing on models for cancers that affect the largest populations. Technological advancements that allow greater exploitation of genetically engineered mouse models, such as RNA interference in vivo, are described in the context of target and drug validation. Finally, this review discusses stratagems for, and obstacles to, the application of these models in the drug development process.

Algorithms↗