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Query: UMLS:C0027651 (tumor)
 685,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Human T-cell lymphotropic/leukemia virus type I (HTLV-I) is associated with T-cell transformation both in vivo and in vitro. Although some of the mechanisms responsible for transformation remain unknown, increasing evidence supports a direct role of viral as well as dysregulated cellular proteins in transformation. We investigated the potential role of the tumor suppressor gene p53 and of the p53-regulated gene, p21waf1/cip1 (wild-type p53 activated fragment 1/cycling dependent kinases [cdks] interacting protein 1), in HTLV-I-infected T cells. We have found that the majority of HTLV-I-infected T cells have the wild-type p53 gene. However, its function in HTLV-I-transformed cells appears to be impaired, as shown by the lack of appropriate p53-mediated responses to ionizing radiation (IR). Interestingly, the expression of the p53 inducible gene, p21waf1/cip1, is elevated at the messenger ribonucleic acid and protein levels in all HTLV-I-infected T-cell lines examined as well as in Taxl-1, a human T-cell line stably expressing Tax. Additionally, Tax induces upregulation of a p21waf1/cip1 promoter-driven luciferase gene in p53 null cells, and increases p21waf1/cip1 expression in Jurkat T cells. These findings suggest that the Tax protein is at least partially responsible for the p53-independent expression of p21waf1/cip1 in HTLV-I-infected cells. Dysregulation of p53 and p21waf1/cip1 proteins regulating cell-cycle progression, may represent an important step in HTLV-I-induced T-cell transformation.
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PMID:p53 functional impairment and high p21waf1/cip1 expression in human T-cell lymphotropic/leukemia virus type I-transformed T cells. 878 9

Recombinant adenovirus (AdV) vectors are highly efficient at in vitro and in vivo gene delivery. In vivo therapy of established murine fibrosarcoma and mammary carcinomas was attempted with intratumoral injections of a recombinant AdV vector in which the human interleukin-2 (IL-2) gene was driven by the cytomegalovirus enhancer/promoter. Delayed growth and rejection of some tumors could be achieved with a cumulative virus dose of 2 to 6 x 10(9) plaque-forming units in two or three divided doses. Lower viral doses were ineffective, and higher doses resulted in animal death due to IL-2 toxicity. Using AdV vectors with the marker genes beta-galactosidase and luciferase, it is clear that even small volume (10 to 20 microL) intratumoral injections result in substantial systemic delivery of a portion of the virus dose. These findings define the potential and limitations of in vivo AdV-based cancer gene therapy and provide support for strategies to develop tumor-specific vectors.
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PMID:In vivo cancer gene therapy with a recombinant interleukin-2 adenovirus vector. 878 5

To establish the expression of the herpes simplex virus thymidine kinase (HSV-TK) gene in tumor cells, we analyzed the promoter function of the SV40 promoter and the nucleotide sequence (CACGTG) to which Myc-Max heterodimers (Myc/Max) were capable of binding in four kinds of cell lines: COLO320 DM, A-431, KF, and Nakajima. When luciferase reporter plasmid under the control of SV40 promoter was transfected into tumor cells in vitro, a high level of luciferase activity was observed in all kinds of cell lines. However, by transfection of the luciferase gene promoted by the Myc/Max binding sequence, accelerated luciferase expression was observed in COLO320 DM and A-431 cells with high expression of c-myc, but not in KF and Nakajima cells, which showed low expression of c-myc. The repeated transfection of the liposome-conjugated HSV-TK gene regulated by the SV40 promoter and cultivation in 100 micrograms/ml of aciclovir for 5 days in vitro demonstrated growth inhibition for all four kinds of cell lines. However, cell toxicity was observed only in COLO320 DM and A-431 cells when the HSV-TK gene promoted by the Myc/Max binding sequence was introduced. (The survival rate to 100 micrograms/ml of aciclovir concentration in COLO320 DM, A-431, KF, and Nakajima cells was 59%, 53%, 74%, and 79%, respectively.) In vivo direct injection of the liposome-conjugated HSV-TK gene regulated by the SV40 promoter into established tumors and aciclovir administration for 10 days into the mice resulted in significant tumor volume reduction in three tested tumor cells. However, injection of the HSV-TK gene promoted by the Myc/Max binding sequence and aciclovir administration into mice could achieve significant tumor regression only in COLO320 DM and A-431 cells. These results suggest that gene therapy using the HSV-TK gene promoted by the Myc/Max binding sequence can be an attractive approach for treatment against tumor cells expressing high levels of c-myc.
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PMID:Inhibition of tumor growth by direct intratumoral gene transfer of herpes simplex virus thymidine kinase gene with DNA-liposome complexes. 878 73

Nutritional deprivation in the early postnatal period severely inhibits cerebellar growth and development, which is related in part to reduced levels of growth factors. Cyclin D1 encodes a growth factor-inducible regulatory subunit of a serine/thereonine kinase that is capable of phosphorylating the tumor suppressor pRB, thereby allowing normal progression through the G1 phase of the cell-cycle. Because the abundance of cyclin D1 is rate limiting in this progression, we examined the regulation of cyclin D1 expression in vivo, using a model of nutritional deprivation. Cyclin D1 expression in cerebella of fed control rats was detected in the external granular layer and was associated with cellular proliferation within this layer. Nutritional deprivation of rats reduced cerebellar weight, as well as the thickness of the molecular layer that largely consists of cells migrating from the external granular layer. Refeeding partially restored cerebellar weight, molecular layer thickness and increased external granular layer cyclin D1 immunostaining. Since nutritional deprivation is accompanied by lower levels of circulating insulin-like growth factor-I (IGF-I), we determined whether IGF-I directly stimulated the cyclin D1 promoter. The human cyclin D1 promoter linked to the luciferase reporter gene was stably integrated into PC12 cells. IGF-I stimulated cyclin D1 promoter activity 4- to 6-fold at 6 hours (h). These findings are consistent with the notion that nutritional deprivation may affect proliferative growth by altering expression of cyclin D1 in the germinal cell layer and that regulation of cyclin D1 expression by growth factors may contribute to normal neonatal cerebellar development. The reduction in cyclin D1 expression as cells differentiate in the cerebellum is consistent with a potential role for cyclin D1 in this process.
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PMID:Reduced cyclin D1 expression in the cerebella of nutritionally deprived rats correlates with developmental delay and decreased cellular DNA synthesis. 880 97

The transcriptional activity of various lengths of the 5'-untranslated region (UTR) of the murine LH receptor (R) gene were studied using the luciferase reporter gene in transiently transfected mouse Leydig tumor cells (mLTC-1). Chinese hamster ovarian (CHO) and HeLa cells were used as controls. The basal transcriptional promoter activity in mLTC-1 cells resided within the first 173 base pairs (bp) of the 5'-UTR. Placing an LHR promoter fragment (bases -715/ -56) in front of the Herpes simplex virus thymidine kinase (TK) minimal promoter resulted in a 7-fold increase in luciferase activity. Deletion of bases -56 to -173 of the above construct totally abolished the increased luciferase activity, brought about by the LHR promoter sequences. Basically similar results on LHR promoter function were observed using CHO cells. In contrast, no LHR promoter activity was detected in HeLa cells, indicating a cell specific nature of its function. The first 173 bp promoter domain is GC-rich, with several SP-1 binding domains, and it bound specifically nuclear proteins isolated from mLTC-1 and HeLa cells. RNAse protection assays reconfirmed the presence of several transcription initiation sites within the first 310 bp of the 5'-UTR, also in the absence of the cognate LHR coding sequences. The most distal site at bp -310 did not function in the absence of the first 173 bp of the 5'-UTR. Other transcription initiation sites were identified closer to the translation initiation site. hCG (50 micrograms/l), 8-bromo (Br)-cAMP (100 mumol/l) and cholera toxin (100 microgram/l) displayed qualitatively similar negative effects on the LHR promoter activity in the transfected mLTC-1 cells when the constructs containing at least the first 565 bp of the LHR 5'-UTR were used, but the inhibitory effects were greatly decreased in constructs containing < or = 304 bp of the promoter region. Hence, the hCG/cAMP associated inhibitory effects interact with region(s) located mainly between bp -565 and -305 of the LHR promoter. The inhibitory role of cAMP on LHR gene expression was also confirmed at the level of hCO-binding and hCG stimulated cAMP production of mLTC-1 cells. In conclusion, the current results elucidate the cis- and trans-acting elements in the regulation of expression of the murine LHR gene in cultured mouse Leydig cells. The minimal basal promoter activity is within the first 173 nucleotides of the 5'-UTR and the structural elements of the negative LHR regulation by the cognate hormone and elevated cAMP levels are mainly located within nucleotides -305 to -565 of the 5'-UTR. The function of the murine LHR promoter is similar to, though not identical with that of the rat, but at variance with that of the human LHR gene.
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PMID:Regulation of function of the murine luteinizing hormone receptor promoter by cis- and trans-acting elements in mouse Leydig tumor cells. 880 40

The authors constructed recombinant adenoviral vectors to investigate their potential for gene therapy treatment of leptomeningeal metastases. Several human cell lines that were derived from tumors occurring as leptomeningeal metastases and that were infected in vitro with major late promoter recombinant adenovirus containing the luciferase (luc) gene (IG.Ad.MLP.luc) showed high levels of expression. When these human tumor cell lines were infected in vitro with recombinant adenovirus harboring the herpes simplex virus-thymidine kinase (HSV-tk) gene (IG.Ad.MLP.TK), they were highly sensitive to the killing effects of ganciclovir (GCV). Transduction efficiency of leptomeningeal tumor cells in vivo was assessed by injecting 9-L rat brain tumor cells into the cerebrospinal fluid of Fischer rats via the cisterna magna. After 3 days, recombinant adenovirus containing the lacZ reporter gene (IG.Ad.MLP.lacZ) was injected via the same route. Six days after tumor cell injection, expression of the reporter gene was observed in tumor cells along the total neural axis. Subsequently, rats with leptomeningeal metastases were treated 3 days after tumor cell injection with HSV-tk. Beginning on the next day, GCV was injected intraperitoneally for 10 days. The rats that developed neurological symptoms were killed immediately. The symptom-free latency of every rat was determined. The rats treated with HSV-tk and subsequent GCV had significantly longer (p < 0.01) symptom-free latency than all control groups. This study demonstrates the feasibility and efficacy of this therapeutic approach in a rat model. Clinically, it should be used in the palliative treatment of patients with leptomeningeal metastases.
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PMID:Treatment of leptomeningeal metastases in a rat model using a recombinant adenovirus containing the HSV-tk gene. 881 69

To target expression of toxic genes to Epstein-Barr virus (EBV)-associated tumor cells, we have developed an EBV-driven enzyme prodrug system (EDEPS) that takes advantage of the trans-activating properties of EBNA1, a latent protein expressed in all EBV-containing cells, to direct expression of cytosine deaminase (CD) at high levels in those cells only. Plasmids were constructed in which the CD gene or a luciferase reporter gene were cloned downstream of the herpes simplex virus thymidine kinase (tk) promoter and the family of repeats (FR) sequence from the oriP region of EBV. Analysis of luciferase activity after transient transfection into a panel of EBV-negative or -positive human cell lines showed that the presence of the FR element enhanced transcription from the tk promoter in all EBV-positive cell lines, whereas transcription from tk was repressed in all EBV-negative cell lines, including B, T, and fibroblast cell lines. In clonogenicity assays following transfection with the CD vector, the presence of 5-fluorocytosine (5-FC) in the culture medium completely abolished cell growth in EBV-positive cell lines, but did not affect the growth of EBV-negative cell lines. This vector system should have wide applicability in that it allows targeted expression of any gene of interest to tumors that carry EBV, irrespective of the role EBV plays in their pathogenesis.
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PMID:Use of Epstein-Barr virus nuclear antigen-1 in targeted therapy of EBV-associated neoplasia. 884 90

Achieving limited recombinant viral replication may provide a means of amplifying viral-mediated gene transfer in vivo. We have previously shown that cotransduction of an E1-defective adenovirus with a plasmid containing the deleted E1 functions into prostate carcinoma cells resulted in E1-defective virus production by those cells. The studies described here have extended these findings to more firmly establish the capacity of the trans complementation approach to achieve amplification of recombinant viral transgene expression. The recombinant virus used for all the studies was AdCMV-luc which contained a luciferase expression cassette; the replication-enabling plasmid, pE1, encoded the E1 functions deleted from AdCMV-luc. Quantitative in vitro studies with the HeLa cell line showed that for each plaque forming unit of AdCMV-luc originally exposed to the cells, 0.54 x 10(3) new replication-defective viruses were detected in supernatants and lysates over the following 4 days. Multiple cell lines were shown to support new virus production following cotransduction of AdCMV-luc and pE1. Small numbers of replication-competent viruses were detected in the lysates and supernatants from the cotransduced cells such that for every 10(5) replication-defective viruses approximately two replication-competent viruses were produced. Tumor nodules produced by engrafting a mixture of AdCMV-luc/pE1-cotransduced HeLa cells with uninfected HeLa cells yielded much higher levels of luciferase expression than control tumors containing mixtures of cells infected with AdCMV-luc alone. In total, these results demonstrate new virus production by cells receiving a replication-defective adenovirus and a replication-enabling plasmid are capable of amplifying recombinant viral transgene expression in vivo.
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PMID:Quantitative and in vivo activity of adenoviral-producing cells made by cotransduction of a replication-defective adenovirus and a replication-enabling plasmid. 885 47

The necessity for prolonged tissue culture manipulations limits the clinical application of many form of gene therapy in patients with malignancies. We hypothesized that granulocyte-macrophage colony-stimulating factor (GM-CSF) cDNA in a plasmid expression vector could be effectively introduced into resting tumor cells, without the need for tissue culture propagation prior to or following transfection, and that efficient expression of transgenic GM-CSF by the transfected tumor cells would confer an effective immune response against tumors. GM-CSF cDNA in expression vectors was coated onto gold particles and accelerated with a gene gun device into mouse and human tumor cells. Human tumor tissue transfected within 4 hr of surgery produced significant levels of transgenic human GM-CSF protein in vitro. Human GM-CSF was readily detectable in serum and at the injection site following subcutaneous implantation of these transfected tumor cells into nude mice. Transfected and irradiated murine B16 melanoma cells produced > or = 100 ng/ml murine GM-CSF/10(6) cells per 24 hr in vitro for at least 10 days. The antitumor efficacy of this nonviral approach was tested using irradiated B16 tumor cells that were transfected with mGM-CSF cDNA and injected into mice as tumor "vaccine". Subsequent challenge of these mice with nonirradiated, nontransfected B16 tumor cells showed that 58% of the animals wer protected from the tumor by the prior vaccine treatment. In contrast, only 2% of control animals were protected by prior treatment with irradiated B16 cells transfected with the vector containing the luciferase gene. These results suggest that particle-mediated transfection of fresh tumor explants with cytokine cDNA is an effective and clinically attractive approach for cancer therapy.
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PMID:Particle-mediated gene transfer of granulocyte-macrophage colony-stimulating factor cDNA to tumor cells: implications for a clinically relevant tumor vaccine. 886 54

THe insulin-like growth factor I receptor (IGF-I-R) has been implicated in the etiology and/or progression of Wilms' tumor, or nephroblastoma, a pediatric neoplasm of the kidney that is often associated with deletion or mutation of the WT1 tumor suppressor gene. The levels of IGF-I-R mRNA in the tumors were sixfold higher than in normal adjacent kidney tissue and were inversely correlated to the levels of WT1 mRNA, suggesting that the expression of the IGF-I-R gene is under inhibitory control by WT1. Cotransfection of an IGF-I-R promoter-luciferase reporter construct together with a WT1 expression vector resulted in a dose-dependent suppression of promoter activity. Multiple WT1 binding sites were mapped in the 5'-flanking and 5'-untranslated regions of the IGF-I-R gene using gel retardation and DNaseI footprinting assays. Thus, suppression of the IGF-I-R promoter by WT1 involves multiple interactions of its zinc finger domain with sites located both upstream and downstream of the transcription initiation site. Finally, we showed that expression of the endogenous IGF-I-R gene is decreased in G401 cells stably transfected with a WT1 expression vector. Reduction in expression of the IGF-I-R gene is associated with a decrease in a number of IGF-I-mediated biological effects. Thus, deletion or mutation of the WT1 gene in Wilms' tumor and other malignancies can result in overexpression of the receptor, with enhanced autocrine/paracrine activation by locally produced or circulating IGFs.
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PMID:Regulation of insulin-like growth factor I receptor gene expression by the Wilms' tumor suppressor WT1. 887 95


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