In vivo selection of retrovirally transduced hematopoietic stem cells (original) (raw)
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Journal of Pharmacology and Experimental Therapeutics, 2002
Currently, low levels of stable gene transfer into hematopoietic tissues of large animals and humans continues to limit the clinical application of gene therapy. One strategy for overcoming this problem is to selectively expand, in vivo, the population of successfully gene-modified cells. Recent work has shown that nucleoside transport inhibition in combination with antifolates can be used to select in vivo for hematopoietic stem cells expressing drug-resistant dihydrofolate reductase (DHFR). In this study we investigated whether trimetrexate (TMTX) and the nucleoside transport inhibitor prodrug nitrobenzylmercaptopurine ribose phosphate (NBMPR-P) can be used to select for tyr22-variant DHFR expressing transgenic hematopoietic cells in a murine bone marrow transplant model. Our results indicate that 40 mg/kg TMTX and 20 mg/kg NBMPR-P can be used in
Gene Therapy, 2009
Human embryonic stem cells (hESCs) provide a novel source of hematopoietic and other cell populations suitable for gene therapy applications. Preclinical studies to evaluate engraftment of hESC-derived hematopoietic cells transplanted into immunodeficient mice demonstrate only limited repopulation. Expression of a drug-resistance gene, such as Tyr22-dihydrofolate reductase (Tyr22-DHFR), coupled to methotrexate (MTX) chemotherapy has the potential to selectively increase the engraftment of gene-modified, hESC-derived cells in mouse xenografts. Here, we describe the generation of Tyr22-DHFR-GFP-expressing hESCs that maintain pluripotency, produce teratomas and can differentiate into MTXr-hemato-endothelial cells. We demonstrate that MTX administered to nonobese diabetic/severe combined immunodeficient/IL-2Rgc null (NSG) mice after injection of Tyr22-DHFR-hESC-derived cells significantly increases human CD34 + and CD45 + cell engraftment in the bone marrow (BM) and peripheral blood of transplanted MTXtreated mice. These results demonstrate that MTX treatment supports selective, long-term engraftment of Tyr22-DHFR cells in vivo, and provides a novel approach for combined human cell and gene therapy.
Improved Retroviral Vectors for Hematopoietic Stem Cell Protection andIn VivoSelection
Journal of Hematotherapy, 1996
Therapeutic gene transfer into hematopoietic cells is critically dependent on the evolution of methods that allow ex vivo expansion, high-frequency transduction, and selection of gene-modified longterm repopulating cells. Progress in this area needs elaboration of defined culture and transduction conditions for long-term repopulating cells and improvement of gene transfer systems. We have optimized retroviral vector constructions based on murine leukemia viruses (MuLV) to overcome the transcriptional repression encountered with the use of conventional Moloney MuLV (MoMuLV) vectors in early hematopoietic progenitor cells (HPC). Novel retroviral vectors, termed FMEV (for Friend-MCF/MESV hybrid vectors), were cloned that mediate greatly improved gene expression in the myeloerythroid compartment. Transfer of the selectable marker multidrug resistance 1 (mdrl), FMEV, in contrast to conventional MoMuLV-related vectors currently in use for clinical protocols, mediated background-free selectability of transduced human HPC in the presence of myeloablative doses of the cytostatic agent paclitaxel in vitro. Furthermore, FMEV also greatly improved chemoprotection of hematopoietic progenitor cells in a murine model system in vivo. Finally, when a second gene was transferred along with mdrl in an FMEV-backbone, close to 100% coexpression was observed in multidrug-resistant colonies. These observations have significant consequences for a number of ongoing and planned gene therapy trials, for example, stem cell protection to reduce the myelotoxic side effects of anticancer chemotherapy, correction of inherited disorders involving hematopoietic cells, and antagonism of HIV infection.
Restoration of Transgene Expression in Hematopoietic Cells with Drug-Selectable Marker Genes
Current Gene Therapy, 2002
Somatic gene therapy is supposed to cure life-threatening hematopoietic disorders but is limited by unstable transgene expression. Efficient gene transfer to hematopoietic progenitor cells does not ensure long-term gene expression. It would therefore be advantageous if the expression of transgenes could be restored in bone marrow. Transfer of drug resistance genes such as the multidrug resistance (MDR1) or mutated dihydrofolate reductase (DHFR) genes to hematopoietic cells protects them from the toxicity of anticancer drugs. In addition, transduced cells obtain a selective growth advantage in the presence of anticancer drugs. This can be used to introduce and enrich otherwise non-selectable genes by cotransfer to target cells. Bicistronic vectors have been constructed for coexpression of drug resistance genes and non-selectable, therapeutic genes with the use of an internal ribosomal entry-site (IRES). With the use of bicistronic vectors, expression and function of therapeutic genes have been increased in tissue culture and in animal models. Further preclinical investigations are needed to identify optimal conditions for selection.
Hematopoietic stem cell gene therapy with drug resistance genes: an update
Cancer gene therapy, 2005
Transfer of drug resistance genes into hematopoietic stem cells (HSCs) has promise for the treatment of a variety of inherited, that is, X-linked severe combined immune deficiency, adenosine deaminase deficiency, thalassemia, and acquired disorders, that is, breast cancer, lymphomas, brain tumors, and testicular cancer. Drug resistance genes are transferred into HSCs either for providing myeloprotection against chemotherapy-induced myelosuppression or for selecting HSCs that are concomitantly transduced with another gene for correction of an inherited disorder. In this review, we describe ongoing experimental approaches, observations from clinical trials, and safety concerns related to the drug resistance gene transfer.
Non-Myelotoxic Agents as a Preparatory Regimen for Hematopoietic Stem Cell Gene Therapy
Research Square (Research Square), 2023
RAG2 deficiency is characterized by a lack of B and T lymphocytes, causing severe lethal infections. Currently, RAG2 deficiency is treated with a Hematopoietic Stem Cell transplantation (HSCT). Most conditioning regimens used before HSCT consist of alkylating myelotoxic agents with or without irradiation and affect growth and development of pediatric patients. Here, we developed a non-myelotoxic regimen using G-CSF, VLA-4I or AMD3100. These agents are known HSC mobilizers or affect bone marrow (BM) permeability and may support the homing of HSCs to the BM, without inducing major side effects. Female Rag2-/mice were pre-treated with Busulfan (BU), G-CSF, VLA-4I or AMD3100 and transplanted with male BM cells transduced with a lentiviral vector carrying codon optimized human RAG2 (RAG2co). Peripheral blood cell counts increased significantly after G-CSF, VLA-4I and AMD3100 treatment, but not after BU. Reconstitution of PB lymphocytes was comparable for all groups with full immune reconstitution at 6 months post transplantation, despite different methods of conditioning. Survival of mice pre-treated with non-myelotoxic agents was significantly higher than after BU treatment. Here we show that the nonmyelotoxic agents G-CSF, VLA-4I, and AMD3100 are highly effective as conditioning regimen before HSC gene therapy and can be used instead of BU.