p53: a gene for all tumours?
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Cell Transformation, Neoplastic↗
Biomedical subjects
R G Vile
Publications and source records attributed to R G Vile.
Use of tissue-specific expression of the herpes simplex virus thymidine kinase gene to inhibit growth of established murine melanomas following direct intratumoral injection of DNA.
We report here the use of the 5' flanking region of the murine tyrosinase gene to direct expression of the herpes simplex virus thymidine kinase (tk) gene specifically to murine melanoma cells, whilst not permitting expression in a range of other cell types. Expression of the herpes simplex virus tk gene from the tyrosinase promoter in melanoma cells rendered them sensitive to killing by ganciclovir (100% cell death of a tk-expressing B16 clone after 12 days in culture at 1 microgram/ml ganciclovir). We also observed a substantial bystander killing effect when expressing cells were mixed with nontransfected parental B16 cells. When transfected murine melanoma cells expressing tk were injected into syngeneic mice both their tumorigenicity and experimental metastatic potential were abrogated completely when the mice were treated with ganciclovir (27 of 28 mice treated with water developed progressively growing tumors versus 1 of 30 in the ganciclovir-treated group). Direct injection of the tk gene under control of the tyrosinase promoter into established tumors in mice, followed by treatment with ganciclovir, led to significant reductions in resultant tumor size relative to the size of tumor developing in mice treated with water (median tumor weight, 1.65 g versus 2.75 g). Therefore, direct transfer of recombinant genes by injection of DNA can significantly reduce established tumor burden in vivo.
Animals↗
In vitro and in vivo targeting of gene expression to melanoma cells.
Gene therapy protocols for cancer usually involve removal of tumor cells, culture in vitro to allow gene transfer, and subsequent reintroduction in vivo. Targeting therapeutic genes to tumor cells in situ requires an accuracy of gene delivery that currently is not possible with the use of existing techniques. To overcome these limitations we have used two promoters, which are preferentially active in melanocytic cells, to direct gene expression specifically to melanoma cells both in vitro and in vivo. Here we describe experiments showing that as little as 769 base pairs of the 5'-flanking regions of the tyrosinase, and 1.4 kilobase pair of the tyrosinase-related protein 1, genes are sufficient to direct expression of the beta-galactosidase gene to both human and murine melanoma cells and melanocytes, while not permitting expression in a range of other cell types in vitro. These promoters showed high levels of activity in 12 of 14 murine and human melanoma cell lines tested but showed only basal levels of activity, similar to that of a promoterless construct, in a range of 12 other cell types. Cell type specificity is maintained when the construct is delivered to cells either by physical means or by inclusion of the cell type-specific expression cassette into a retroviral vector. Direct injection of DNA, encoding the beta-galactosidase gene expressed from either promoter, into established B16 melanomas or Colo 26 tumors in syngeneic mice resulted in extensive transduction of tumor cells in the B16 melanomas (approximately 10% of tumor cells expressing 10 days after DNA injection), whereas no blue-staining cells were seen in the Colo 26 tumors. The reporter gene was expressed in melanoma cells and in some normal melanocytes but not in other surrounding normal tissue. We propose that the combination of a tissue-specific promoter driving a therapeutic gene, with delivery of such a construct directly to sites of tumor growth in vivo, either by direct DNA injection or by retroviral infection, may provide significantly enhanced safety for gene therapy for solid tumors.
Animals↗
Gene transfer therapy in cancer.
Gene transfer techniques have now achieved clinical realization in the wake of recent advances in recombinant DNA technology, together with increased understanding of the molecular biology and immunology of cancer. These novel treatments, and their applications and limitations merit intensive study.
Animals↗
Retroviral pseudotypes produced by rescue of a Moloney murine leukemia virus vector by C-type, but not D-type, retroviruses.
Human HOS cells containing a Moloney murine leukemia virus (Mo-MLV) recombinant genome were infected by a panel of retroviruses. The C-type viruses simian sarcoma associated virus, feline leukemia virus subgroup B, and the feline endogenous virus RD114 were able to form pseudotypes with the Mo-MLV genome, which transferred a selectable marker gene to target cells; however, Human T cell leukemia virus-1 and the D-type viruses Mason-Pfizer monkey virus and simian retrovirus-1 failed to rescue the Mo-MLV vector. Further characterization of the RD114 pseudotype demonstrated that it retained the receptor specificity of RD114 and will therefore prove useful in receptor characterization.
Animals↗
Identification of a generalised packaging sequence for D-type retroviruses and generation of a D-type retroviral vector.
In order to construct vectors based upon D-type, rather than C-type, retroviruses, we have identified a 624-bp fragment of Mason-Pfizer monkey virus (MPMV) which constitutes a packaging sequence for at least two D-type retroviruses. When this fragment was included in an extensively deleted D-type vector genome, the D-type viruses MPMV and SRV-5, but not the C-type viruses MLV-A or MLV-E, rescued the vector RNA from HeLa cells. The recombinant virus stocks have the host range of the rescuing D-type virus as shown by expression of an internal (SV40-puromycin) cassette replacing the retroviral structural genes. The recombinant MPMV was specifically neutralized by anti-MPMV serum and receptor interference was demonstrated when it was plated on cells productively infected with wild type MPMV. When the putative D-type packaging sequence was removed from the vector genome, even though the other sequence elements required for efficient reverse transcription remained, the vector was no longer rescued from HeLa cells. These results complement the recent demonstration of broad specificity of rescue of a C-type vector (carrying only the packaging sequence of Mo-MLV) by several different C-type, but not D-type, viruses. Replacement of the D-type packaging sequence by most of the extended packaging sequence of Mo-MLV prevented the otherwise D-type vector from being rescued by D-type viruses and did not allow it to be rescued by C-type viruses. This was probably because of the incompatibility of the D-type vector sequences with the C-type retroviral proteins involved in viral reverse transcription and integration. Hence, we have localized a packaging sequence that is recognized by D-type, but not by C-type, retroviruses and have constructed a D-type vector which may be useful in gene transfer experiments.
Betaretrovirus↗
Feline leukemia virus subgroup B uses the same cell surface receptor as gibbon ape leukemia virus.
Pseudotypes of gibbon ape leukemia virus/simian sarcoma-associated virus (GALV/SSAV) and feline leukemia virus subgroup B (FeLV-B) have been constructed by rescuing a Moloney murine leukemia virus vector genome with wild-type GALV/SSAV or FeLV-B. The resulting recombinant viruses utilized core and envelope proteins from the wild-type virus and conferred resistance to growth in L-histidinol upon infected cells by virtue of the HisD gene encoded by the vector genome. They displayed the host range specificity of the rescuing viruses and could be neutralized by virus-specific antisera. Receptor cross-interference was observed when the GALV/SSAV or FeLV-B pseudotypes were used to superinfect cells productively infected with either GALV/SSAV or FeLV-B. Although murine cells are resistant to FeLV-B infection, murine cells expressing the human gene for the GALV/SSAV receptor became susceptible to FeLV-B infection. Therefore GALV/SSAV and FeLV-B utilize the same cell surface receptor.
3T3 Cells↗
Cell biology. Virus receptors as permeases.
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Animals↗
A murine cell line producing HTLV-I pseudotype virions carrying a selectable marker gene.
A murine cell line, EH, expressing the gag and pol proteins of Moloney murine leukemia virus (Mo-MLV) as well as an Mo-MLV recombinant genome with a selectable marker (histidinol dehydrogenase), was transfected with a plasmid coding for the gene of the human T-cell leukemia virus type I (HTLV-I) envelope precursor (gp62), placed under the control of the human cytomegalovirus immediate early promoter. One clone, T. 14, was recovered, in which gp62 RNA and protein were detected. Supernatant from this clone transferred the HisD gene to a panel of cell lines which express receptors for HTLV-I, but was unable to pass the marker gene to cells which do not express receptors. The colony-forming units were sensitive to HTLV-I receptor interference and to specific neutralization by anti-HTLV-I serum. These data show that hybrid virions were produced in which the envelope proteins of HTLV-I had pseudotyped Mo-MLV capside particles containing a selectable recombinant viral genome.
Animals↗
Different approaches in the gene therapy of cancer.
The requirements of gene therapy for cancer are distinct from those of gene therapy for hereditary monogenic diseases. In cancer the aim is to kill, not cure tumour cells. Also issues such as duration of gene expression and immunogenicity of vector systems are of less relevance than efficiency of delivery to all tumour cells. In this light, we discuss the vector systems currently available and the methods to target transgenes to tumour cells. In view of the current limitations in both vector systems and targeting of tumours, we discuss the strategies that may be applied to increase the effectiveness of inefficient delivery, such as immune activation, bystander cytotoxicity and replication-competent viruses.
Cytotoxicity, Immunologic↗