Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P04637 (p53)
 77,613 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Previous clinical experience shows that the efficacy of suicide gene transfer in tumor therapy is limited, resulting from inefficient gene transfer or alternatively, from intrinsic resistance of the tumor in vivo. Herpes simplex virus thymidine kinase/ganciclovir (TK/GCV), a paradigmatic suicide gene therapy system, has been described to exert its cytotoxic effect, at least in part, by inducing apoptosis in target cells. Here, we report that mitochondria amplify TK/GCV-induced apoptosis by regulating p53 accumulation and the effector phase of apoptosis. Treatment with TK/GCV led to mitochondrial perturbations including loss of the mitochondrial membrane potential and release of cytochrome c from mitochondria into the cytosol, inducing caspase activation and nuclear fragmentation. Inhibition of TK/GCV-induced mitochondrial perturbations by Bcl-2 overexpression or by the mitochondrion-specific inhibitor bongkrekic acid also strongly inhibited TK/GCV-induced activation of caspases and apoptosis. TK/GCV-induced mitochondrial perturbations depended on caspase activity possibly initiated by death receptor signaling. Perturbation of mitochondrial function mediated accumulation of wild-type p53 protein, since Bcl-2 overexpression, bongkrekic acid, or inhibition of mitochondrial protein synthesis with chloramphenicol strongly reduced TK/GCV-induced accumulation of wild-type p53 protein. These findings suggest that TK/GCV therapy may be less efficient in tumors in which the mitochondrial amplification of TK/GCV-induced apoptosis is blocked, e.g., by Bcl-2 overexpression. Given the low efficacy of currently used gene therapy systems, our data on molecular mechanisms that regulate sensitivity or resistance toward TK/GCV-induced cytotoxicity might have important implications to improve the clinical application of suicide gene therapy.
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PMID:Mitochondrial amplification of death signals determines thymidine kinase/ganciclovir-triggered activation of apoptosis. 1086 13

Normally, thyroid cancer is a disease with a good prognosis, but about 30% of the tumours dedifferentiate and may finally develop into highly malignant anaplastic thyroid carcinomas with a mean survival time of less than 8 months. Due to the loss of thyroid-specific functions associated with dedifferentiation, these tumours are inaccessible to standard therapeutic procedures such as radioiodide therapy and thyroxine-mediated thyrotrophin suppression. Medullary thyroid carcinomas are also highly aggressive. Here, therapy is limited to surgery, and no alternative is left if patients do not respond to this standard procedure. Obviously, new approaches would be desirable. Several novel approaches are currently being tested for the treatment of thyroid cancer. Many of them utilise methods of gene therapy, but follow different strategies: (1) reintroduction of the tumour suppressor p53 into a background lacking functional p53; (2) suicide gene therapy with ganciclovir and a transduced gene for herpes simplex virus thymidine kinase controlled by the thyroglobulin promoter; (3) strengthening of the antitumour immune response by expression of an adenovirus-delivered interleukin-2 (IL-2) gene; (4) induction of an immune response by DNA vaccination against the tumour marker calcitonin; (5) transduction of the thyroid sodium/iodide transporter gene to make tissues that do not accumulate iodide treatable by radioiodide therapy; (6) blocking of the expression of the oncogene c-myc by antisense oligonucleotides. While these approaches are still tested in vitro or in animal models, first results from pilot studies concerning other novel treatment modalities are available: (7) radioimmunotherapy exploits the carcinoembryonic antigen expressed on medullary thyroid carcinomas to target a radiolabelled antibody to the tumour; and (8) retinoic acid is used for a redifferentiation therapy in the case of thyroid cancer. Hopefully, one or the other of these novel strategies may probably extend after some time the current therapeutic repertoire for thyroid cancers and provide a perspective for otherwise untreatable patients.
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PMID:Innovative strategies for the treatment of thyroid cancer. 1087 26

In this study, we evaluated three herpes simplex virus-1 thymidine kinase (HSV-tk) carrying replication-competent adenoviral vectors with and without the Ad5 E1B 55 kDa gene to assess whether this gene product has an influence on their antitumor efficacy, replication kinetics, and potential hepatotoxicity. Furthermore, we assessed the efficacy of these vectors in combination with ganciclovir (GCV). When compared with wild-type adenovirus, the recombinant vectors, in particular the E1B 55 kDa-deleted vector Ad.TK(RC)(II), generated a more efficiently cytopathic effect in proliferating cells, independently of their p53 phenotype. In a s.c. A549 lung cancer xenograft model, the cytoreductive effect of Ad.TK(RC)(II) was enhanced when followed by GCV treatment. In contrast, the efficacy of both E1B 55 kDa-positive vectors could not be further improved by GCV. In an i.p. MDAH 2774 ovarian cancer xenograft tumor model, the survival of animals treated with a prototypical replication-deficient adenovirus expressing HSV-tk (Ad.TK) was improved compared to controls when followed by GCV. In contrast, the cytoreductive efficacy of the replication-competent vectors was diminished when combined with the virostatic GCV. However, the antitumor effect of all replication-competent vectors was superior to combination chemotherapy with paclitaxel and carboplatin. In both tumor models, the oncolytic effect of the E1B 55 kDa-positive vectors was greater than that of Ad.TK(RC)(II). In an attempt to assess the toxicity of these vectors in a nonpermissive host, the viruses were administered systemically to immunocompetent and immunodeficient mice. Greater hepatotoxicity was seen with i.v. administration of the replication-competent viruses than with Ad.TK and in immunocompetent hosts, suggesting involvement of the immune system in the induction of tissue damage. The E1B 55 kDa gene had no significant influence on the liver toxicity of the vectors in this system. At therapeutic doses, intratumoral or i.p. injection of all vectors was well tolerated. Importantly, these replication-competent HSV-tk-expressing vectors were highly susceptible to GCV, representing an effective fail-safe mechanism to abolish viral replication in a clinical setting. Controllable intratumoral viral replication holds promise as a new treatment modality for cancer.
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PMID:The role of the E1B 55 kDa gene product in oncolytic adenoviral vectors expressing herpes simplex virus-tk: assessment of antitumor efficacy and toxicity. 1094 25

Chromosomal double-strand breaks (DSBs) occurring in mammalian cells can initiate genomic instability, and their misrepairs result in chromosomal deletion, amplification, and translocation, common findings in human tumors. The tumor-suppressor protein p53 is involved in maintaining genomic stability. In this study, we demonstrate that the deficiency of wild-type p53 protein may allow unrepaired DSBs to initiate chromosomal instability. The human lymphoblastoid cell line TK6-E6 was established by transfection with human papilloma virus 16 (HPV16) E6 cDNA into parental TK6 cells via a retroviral vector. Abrogation of p53 function by E6 resulted in an increase in the spontaneous mutation frequencies at the heterozygous thymidine kinase (TK) locus but not at the hemizygous hypoxanthine phosphoribosyl transferase (HPRT) locus. Almost all TK-deficient mutants from TK6-E6 cells exhibited loss of heterozygosity (LOH) with the hemizygous TK allele. LOH analysis with microsatellite loci spanning the long arm of chromosome 17, which harbors the TK locus, showed that LOH extended over half of 17q toward the terminal end. Cytogenetic analysis of LOH mutants by chromosome painting indicated a mosaic of chromosomal aberrations involving chromosome 17, in which partial chromosome deletions, amplifications, and multiple translocations appeared heterogeneously in a single mutant. We speculate that spontaneous DSBs trigger the breakage-fusion bridge cycle leading to such multiple chromosome aberrations. In contrast, no chromosomal alterations were observed in TK-deficient mutants from TK6-20C cells expressing wild-type p53. In wild-type p53 cells, spontaneous DSBs appear to be promptly repaired through recombination between homologous chromosomes. These results support a model in which p53 protein contributes to the maintenance of genomic integrity through recombinational repair.
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PMID:Requirement of wild-type p53 protein for maintenance of chromosomal integrity. 1097 90

We examined whether antitumor effect could be produced by retrovirally expressed interleukin-2(IL-2) gene, glanulocyte macrophage-colony stimulating factor(GM-CSF) gene, herpes simplex virus-thymidine kinase(HSV-tk) gene and p53 gene in human esophageal cancer cells using nude mice. Loss of tumorigenicity of IL-2 or GM-CSF producing cancer cells were observed. The antitumor effect was also evidenced by the injection of these cells into established tumors of wild-type cells. In suicide gene therapy on esophageal cancer, the growth suppression of esophageal cancer cells transducing HSV-tk gene tumors in nude mice induced by ganciclovir treatment and all the tumors disappeared. The wild-type p53 transduced tumor cells became markedly susceptible to irradiation and anticancer agents. Administration of cisplatine noticeably suppressed the growth of p53 transduced tumors inoculated in nude mice. We established the clinical protocol of gene therapy for esophageal cancer using wild-type p53 gene with adenovirus vector. In this autumn we are going to start this clinical trial.
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PMID:[The protocol of clinical trial and basic experiments for esophageal cancer using gene transduction]. 1100 29

The p53 tumor suppressor protein functions as an activator and also as a repressor of gene transcription. Currently, the mechanism of transcriptional repression by p53 remains poorly understood. To help clarify this mechanism, we carried out studies designed to identify the minimal repression domain that inhibits p53 transcriptional activities. We found only eight amino acids (339) of the COOH-terminal domain (termed P53MRD) that possess activities of repression. The exact location of this minimal domain is on the E6-binding region, and it lacks the ability of tetramerization. P53MRD is able to repress the transcription of p53 while not affecting VP16. The mutants (amino acids M340P and F341D) of native p53 also lost transcriptional repression of the thymidine kinase chloramphenicol acetyltransferase promoter. These results suggest that this eight-amino acid element is required for the repression of p53.
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PMID:p53 amino acids 339-346 represent the minimal p53 repression domain. 1100

Allelic loss is an important mutational mechanism in human carcinogenesis. Loss of heterozygosity (LOH) at an autosomal locus is one outcome of the repair of DNA double-strand breaks (DSBs) and can occur by deletion or by mitotic recombination. We report that mitotic recombination between homologous chromosomes occurred in human lymphoid cells exposed to densely ionizing radiation. We used cells derived from the same donor that express either normal TP53 (TK6 cells) or homozygous mutant TP53 (WTK1 cells) to assess the influence of TP53 on radiation-induced mutagenesis. Expression of mutant TP53 (Met 237 Ile) was associated with a small increase in mutation frequencies at the hemizygous HPRT (hypoxanthine phosphoribosyl transferase) locus, but the mutation spectra were unaffected at this locus. In contrast, WTK1 cells (mutant TP53) were 30-fold more susceptible than TK6 cells (wild-type TP53) to radiation-induced mutagenesis at the TK1 (thymidine kinase) locus. Gene dosage analysis combined with microsatellite marker analysis showed that the increase in TK1 mutagenesis in WTK1 cells could be attributed, in part, to mitotic recombination. The microsatellite marker analysis over a 64-cM region on chromosome 17q indicated that the recombinational events could initiate at different positions between the TK1 locus and the centromere. Virtually all of the recombinational LOH events extended beyond the TK1 locus to the most telomeric marker. In general, longer LOH tracts were observed in mutants from WTK1 cells than in mutants from TK6 cells. Taken together, the results demonstrate that the incidence of radi-ation-induced mutations is dependent on the genetic background of the cell at risk, on the locus examined, and on the mechanisms for mutation available at the locus of interest.
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PMID:Different mechanisms of radiation-induced loss of heterozygosity in two human lymphoid cell lines from a single donor. 1122 43

Suicide gene therapy using viral transfer of herpes simplex virus type I (HSV-1) thymidine kinase (TK) and subsequent ganciclovir (GCV) chemotherapy was the first approach used in clinical trials of somatic gene therapy for glioblastoma. The molecular pathways mediating TK/GCV-induced cell death remain to be elucidated. Here, we report that adenoviral (Ad)-TK/GCV-induced death is p53-independent and does not involve altered CD95 or CD95L expression. Ectopic expression of the preferential caspase 8 inhibitor, crm-A, inhibits Ad-CD95L-induced cell death but has no effect on TK/GCV cytotoxicity. LN-18 glioma cells selected for resistance to death receptor-mediated cell death do not acquire cross-resistance to TK/GCV. TK/GCV triggers mitochondrial cytochrome c release and activation of caspases 3, 7, 8 and 9 in a death receptor-independent manner. These events are associated with the loss of BCL-X(L). Forced expression of a BCL-X(L) transgene, or co-exposure to a pseudosubstrate caspase inhibitor, zVAD-fmk, inhibit TK/GCV cytotoxicity. Double-transfected cell lines expressing crm-A and enhanced green fluorescent protein (eGFP) show that the bystander effect in vitro is also death receptor- and caspase 8-independent. TK/GCV therapy does not kill glioma cells in synergy with cancer chemotherapy drugs, including lomustine, temozolomide and topotecan. In contrast, there is strong synergy of TK/GCV and CD95L. Thus, TK/GCV-induced cell death involves a mitochondria-dependent loop of caspase acvtivation that can be synergistically enhanced by death receptor agonists such as CD95L. TK/GCV-mediated sensitization of glioma cells to CD95L expressed on immune effector cells or parenchymal brain cells might account for the immune system's and bystander effects of TK/GCV therapy observed in rodent glioma models in vivo.
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PMID:Death receptor-independent cytochrome c release and caspase activation mediate thymidine kinase plus ganciclovir-mediated cytotoxicity in LN-18 and LN-229 human malignant glioma cells. 1131 26

We used a murine tumor progression model for the evaluation of potential proliferation markers using positron emission tomography (PET). 5-[(18)F]-2'-deoxyuridine ([(18)F]FdUrd) was synthesized with >98% radiochemical purity and investigated in a pancreatic cancer model, transforming growth factor alpha transgenic mice crossbred to p53 deficient mice. Thymidylate synthase was increased already in premalignant lesions, whereas thymidine kinase 1 mRNA levels were up-regulated 4-fold in the pancreatic cancer specimen of these mice. PET imaging was performed after injection of 1 MBq of [(18)F]FdUrd and 1 MBq of [(18)F]fluoro-deoxyglucose. Animals with pancreatic cancer displayed focal uptake of both tracers. The [(18)F]FdUrd uptake ratio closely correlated with the proliferation index as evaluated in morphometric and fluorescence-activated cell sorter analysis. These results indicate the potential of our tumor model for the evaluation of PET tracers and suggest [(18)F]FdUrd as a tracer for the assessment of proliferation in vivo.
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PMID:In vivo evaluation of 5-[(18)F]fluoro-2'-deoxyuridine as tracer for positron emission tomography in a murine pancreatic cancer model. 1135 95

The herpes simplex virus 1 (HSV-1) tegument protein VP22 has been utilised as a vehicle for trafficking proteins. It has a remarkable property of exiting the cell that is producing it and entering the neighbouring cells, which has been used to deliver therapeutic proteins, p53 and herpes simplex virus thymidine kinase (tk). It has a complex pattern of expression and subcellular localisation. Functions of VP22 include intercellular transport, binding to and bundling of microfilaments, inducing cytoskeleton collapse, nuclear translocation during mitosis, and binding to chromatin and nuclear membrane. The regions of VP22 which contain each of these functions have not been characterised. Finding the region carrying the property of intercellular spread would facilitate enhancement of transport function. By constructing a series of deletion constructs of VP22 tagged by the green fluorescent protein (GFP) we have mapped the functions of VP22 to specific regions in the polypeptide as follows: intercellular transport - aa 81-195; binding and reorganisation of cytoskeleton - aa 159-267; nuclear targeting, inhibition of cytoskeleton collapse - aa 81-121; and nuclear targeting and facilitation of intercellular transport - aa 267-301. Separation of VP22 functions enables focus on the mechanism of VP22-mediated transport and improve the transportation efficiency of VP22.
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PMID:Mapping of herpes simplex virus-1 VP22 functional domains for inter- and subcellular protein targeting. 1152 52


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