Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0027651 (tumor)
 685,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The p53 tumor suppressor gene product is known to be active in mediating radiation-induced G1-S cell cycle arrest and apoptosis in a number of normal cell lines. These functions are compromised by inactivation of p53, which promotes tumor progression. Because the p53 gene appears to play an important role in the cellular response to radiation, wild-type p53 gene replacement might be expected to increase the sensitivity of malignant cells with mutant p53 to the cytotoxic effects of ionizing radiation. This study demonstrates that adenovirus (AdV)-mediated transfer and expression of the wild-type p53 in malignant cells lacking the p53 gene results in an increase in cellular radiosensitivity in vitro and tumor radioresponsiveness in vivo. Cultures of the p53 double deletion mutant ovarian cell line SK-OV-3 were infected with nonreplicative adenoviral vectors containing either the wild-type p53 gene (AdVp53) or the luciferase gene (AdVluc). Cultures infected with AdVp53 efficiently expressed wild-type p53 protein and were more sensitive to radiation than uninfected cultures or cultures infected with AdVluc. The ability of AdVp53 to radiosensitize tumors in vivo was tested using SK-OV-3 tumors growing in the flanks of severe combined immune-deficient mice. Intratumoral injection with AdVp53, but not AdVluc, led to enhanced radioresponsiveness and 45% long-term tumor control. These studies demonstrate the ability of AdVp53 to effectively transfer and express p53 protein in established tumors with a resultant increase in radiation responsiveness.
 ...
PMID:Adenovirus-based transfer of wild-type p53 gene increases ovarian tumor radiosensitivity. 889 40

Overexpression of P-glycoprotein in tumor cells can represent a severe drawback for cancer chemotherapy. P-glycoprotein acts as an efflux transporter for a variety of chemotherapeutic agents. It is encoded by multidrug resistance (mdr) genes of the subfamily 1 in humans (MDR1) and rodents (mdr1a and 1b). Because mdr1 gene expression is inducible in cultured rat hepatocytes and in rat liver with chemical carcinogens such as 2-acetylaminofluorene or aflatoxin B1, which form DNA-binding electrophiles during their metabolism, we investigated whether the DNA-damaging chemotherapeutic drug mitoxantrone may induce multidrug resistance in rodents and in hepatocytes in primary culture. In H4IIE rat hepatoma cells stably transfected with a luciferase construct containing the rat mdr1b promoter, mitoxantrone caused a concentration-dependent increase in promoter activity. Mdr1 gene expression in cultured rat hepatocytes was enhanced at mitoxantrone concentrations greater than or equal to 0.1 microM and in mouse hepatocytes at 5 microM. In hepatocytes from both species, a correlation was found between mdr1 induction and the inhibition of protein synthesis. In vivo, mitoxantrone was a very powerful inducer of mdr1 gene expression in rat liver and small intestine. In rat kidney, induction of mRNA was lower, and a marginal effect was seen in lung. In contrast with rats, no significant induction of mdr1 gene expression was obtained in mouse liver. Probably as a consequence of inhibition of protein synthesis, mitoxantrone did not lead to a pronounced elevation of P-glycoprotein levels in rat liver and kidney.
 ...
PMID:Multidrug resistance gene expression in rodents and rodent hepatocytes treated with mitoxantrone. 893 57

DNA topoisomerase II (topo II) is an essential nuclear enzyme involved in major cellular functions such as DNA replication, transcription, recombination, and mitosis. While an elevated level of topo II alpha is associated with cell proliferation, wild-type (wt) p53 inhibits the expression of various growth-stimulatory genes. To determine if p53 downregulates topo II alpha gene expression, a murine cell line, (10)1val, that expresses a temperature-sensitive p53 was utilized. The (10)1val cells had significantly lower levels of topo II alpha mRNA and protein following incubation for 24 h at 32 degrees C (p53 with wt conformation) than at 39 degrees C (p53 with mutant conformation). The effect of p53 on the human topo II alpha gene promoter was determined by using luciferase reporter plasmids containing varying lengths of the topo II alpha promoter transiently cotransfected into p53-deficient (10)1 cells together with wt or mutant p53 expression plasmids. Transcription from the full-length (bp -557 to +90) topo II alpha promoter was decreased 15-fold by wt p53 in a concentration-dependent manner, whereas mutant p53 exerted much weaker inhibition. Consecutive deletion of the five inverted CCAAT elements (ICEs) from the topo II alpha promoter reduced both the basal promoter activity and wt p53-induced suppression. Transcription of the minimal promoter (-32 to +90), which contains no ICE, was slightly stimulated by wt or mutant p53 expression. When point mutations were introduced into the most proximal ICE (-68), the inhibitory effect of wt p53 was alleviated and stimulation of topo II alpha expression resulted. Our study suggests that wt p53 functions as a transcriptional repressor of topo II alpha gene expression, possibly through a functional interaction with specific ICEs. Inactivation of wt p53 may reduce normal regulatory suppression of topo II alpha and contribute to abortive cell cycle checkpoints, accelerated cell proliferation, and alterations in genomic stability associated with neoplasia.
 ...
PMID:Inhibition of DNA topoisomerase II alpha gene expression by the p53 tumor suppressor. 897 19

The targeted introduction of therapeutic genes into malignant cells based on receptor mediated endocytosis of ligand-DNA conjugates recently was established as a transfection system and provides a promising strategy for cancer therapy. Antiidiotype antibodies could be of particular interest for this approach because their immunoglobulin receptor idiotypes represent highly specific tumor markers. Their safe and specific applicability in vivo, alone or as immunotoxins, has been proven in clinical trials for passive immunotherapy and vaccination strategies. For these reasons we have explored the utility of antiidiotype antibodies for gene delivery systems using the reporter genes beta-galactosidase and luciferase. Two monoclonal antibodies, SIC5 and 5D10, specific for B-lymphoma cell lines, which represent models for murine plasmacytoma (38C13) and human non-Hodgkin's lymphoma (SU-DHL-4) have been covalently linked to polylysine via the heterobifunctional cross-linker SPDP. Highly efficient uptake and internalization of the immunoconjugates have been shown by fluorescence microscopy and fluorescence-activated cell sorting (FACS) analysis. Successful transfections have been shown at the RNA and the reporter gene level (beta-galactosidase, luciferase) using different promoter/enhancer systems. Beta-galactosidase activity was detected by flow cytometry (FACS-gal) analysis for both cell lines, and SU-DHL-4 cells showed significant luciferase activity.
 ...
PMID:Antibody-mediated gene delivery for B-cell lymphoma in vitro. 898 39

In this study, we investigated whether the regulation and the copy number of the herpes simplex virus thymidine kinase (HSVtk) gene increased the sensitization to ganciclovir (GCV) of glioma cell lines (Rat C6 and human U118-MG) using liposome-mediated gene transfer. Three recombinant plasmids carrying the HSVtk gene driven by the thymidine kinase promoter in single (pAGo) and double copy (pYED) or by the human cytomegalovirus promoter (pCMVtk) were used for the transfection. The DNA delivery was optimized by screening a panel of cationic liposomes using Lac-Z and luciferase as reporter genes. The efficiency of transfection reached 33% to 36% in vitro but only 18.6% in vivo after an intratumoral injection of DNA-liposome complexes. Moreover, after transfection of the three plasmids, the cell-killing effect of GCV was evaluated. A significant enhancement (four- to fivefold) of the cell sensitivity to GCV was shown in pCMVtk and pYED as compared with pAGo-transfected cells in both cell lines. According to the plasmid, the effect of the HSVtk/GCV system was confirmed by in vivo experiments and was objectified by a higher tumor weight reduction with pCMVtk (49%) than pAGo (27%). From these results, we conclude that (1) the gene transfer can be achieved by cationic liposomes both in vitro and in vivo and that (2) using this type of vector, the antitumor effect of the HSVtk/GCV system could be potentiated by the up-regulation of HSVtk gene duplication.
 ...
PMID:Liposomal delivery of the herpes simplex virus thymidine kinase gene in glioma: improvement of cell sensitization to ganciclovir. 898 41

Human papillomavirus (HPV) infection is believed to play a central role in cervical carcinogenesis. Specifically, two viral oncoproteins, E6 and E7, possess transforming ability and have been shown to interact with the cellular tumor suppressors p53 and p105, the retinoblastoma (Rb) gene product. To test the hypothesis that E6 and E7 play an active role in the maintenance of the malignant phenotype and may be ideal targets for antigene therapy, we tested the antiproliferative effects of phosphorothioate oligodeoxynucleotides (oligos) targeting HPV-16 E6 and E7 in cervical cancer cell lines and primary tumor explants. The ATP cell viability assay was used to measure growth effects of 27-mer antisense oligos targeting the ATG translational start region of HPV-16 E6 and E7 sequences in HPV-16-positive cell lines SiHa and CaSki and four advanced, primary cervical tumor explants. A random oligo sequence, an HPV-18-positive and HPV-negative cell line, one histologically confirmed endometrial and two ovarian tumors were used as negative controls. HPV type was confirmed by hybrid capture techniques. Cell lines and sterile (staging laparotomy) tumor cells were plated at 5000 cells/0.1 ml and 100,000 cells/0.5 ml in 96-well plates or soft agar, respectively, and incubated at 37 degrees C with a single treatment of oligos at 0-16 microM. E6/E7 combinations at a fixed ratio of 1:1 were used at 0-8 microM for each oligo. Cellular ATP was measured by luciferin/luciferase fluorescence on Day 6. HPV-16 E6 and E7 oligos showed antiproliferative effects in all HPV-16-positive cell lines and primary tumor explants (IC50s 6.9-9.5 microM for cell lines, 9.1-12.1 microM primary cervical tumors), while the HPV-negative C33-A cell line and HPV-18-positive cell line HeLa were relatively insensitive to the HPV-16 oligos (IC50s > 30 microM extrapolated). The endometrial and two ovarian primary tumors were also insensitive to the HPV E6 and E7 oligos (IC50s > 25 microM extrapolated). Random oligos had little effect on cell growth at concentrations up to 16 microM (< 25% inhibition), except in CaSki (@50% inhibition at 16 microM). Combinations of E6 and E7 demonstrated mixed synergistic and antagonistic effects as determined by combination indices (CI) derived from median effect parameters. In the HPV-16-positive primary cervical tumors and the cell line SiHa, E6/E7 combinations were synergistic at low doses (< 25% growth inhibitory dose range) and antagonistic at doses above this. For the HPV-16-positive cell line CaSki, however, E6/E7 combinations were antagonistic at all dose ranges. Phosphorothioate oligos directed against the viral oncogenes E6 and E7 were shown to have antiproliferative effects specific to HPV-containing cancer cells. These specific antiproliferative effects suggest that HPV-16 E6 and E7 sequences play an active role in the malignant growth properties of cervical cancer cells and may be ideal targets for antigene therapy.
 ...
PMID:In vitro antigene therapy targeting HPV-16 E6 and E7 in cervical carcinoma. 899 42

Dendritic cells (DCs) are the most potent antigen-presenting cells (APCs) for the initiation of antigen-specific T-cell activation. DCs may be highly enriched from peripheral blood-adherent leukocytes by short-term (7-day) culture in the presence of interleukin (IL)-4 and granulocyte-macrophage colony-stimulating factor. Various methods of gene transfer were studied, including DNA/liposome complexes, electroporation, CaPO4 precipitation, and recombinant adenovirus (AdV) vectors. Low levels of expression were obtained with the physical methods tested. In contrast, AdV vectors expressing luciferase, beta-galactosidase, IL-2, and IL-7 all readily transduced human DCs. Increasing levels of gene expression were observed over a range of multiplicity of infection (MOI) of 10:1 to 10,000:1, with transduction efficiencies exceeding 95% at higher MOI. Although levels of maximal gene expression in DCs were significantly lower than those obtained using human tumor cell lines, IL-2 and IL-7 production of up to 5 x 10(2) ng/10(6) DC were achieved. These results suggest that AdV vectors are a promising vehicle for genetically engineering human DCs.
 ...
PMID:A comparison of gene transfer methods in human dendritic cells. 901 47

The current study tested the hypothesis that hypoxia stimulates atrial natriuretic peptide (ANP) gene expression and secretion in cultured atrial myocytes (AT-1 cells). AT-1 cells were obtained from a transplantable mouse atrial cardiomyocyte tumor lineage. Confluent AT-1 cells were exposed to hypoxia (1% oxygen) or normoxia (21% oxygen) as controls for 6 hours to 7 days. Medium ANP levels were measured by radioimmunoassay, and intracellular ANP gene transcripts were quantified by Northern and slot blot analyses. Exposure to hypoxia resulted in a significant increase in cellular ANP mRNA levels within 36 hours, which peaked (3.6-fold increase) at 2 days after hypoxic exposure, and produced a time-dependent increase in the release of ANP from AT-1 cells for 2 to 7 days. Transfection studies with recombinant DNA constructs that contained fragments of the -3003/+62 sequence of the ANP promoter and the luciferase reporter gene revealed that the regulatory sequences that mediate the hypoxia-induced increase in transcription are located within a region that extends from -638 to -518 bp to the transcriptional start site of the ANP gene. Gel mobility shift assays demonstrated that hypoxia-inducible nuclear proteins that bound to the 120-bp putative hypoxia-responsive elements of the ANP gene were produced during hypoxic exposure. We have thus defined a 120-bp region within the ANP gene promoter that contains hypoxia-responsive elements that might be responsible for the enhancement of ANP gene expression in atrial myocytes during hypoxic exposure.
 ...
PMID:Hypoxia stimulates atrial natriuretic peptide gene expression in cultured atrial cardiocytes. 903 84

DNA topoisomerase IIalpha (topo IIalpha) is an essential proliferation-dependent nuclear enzyme which has been exploited as an anti-tumor drug target. Since the proliferative status of human leukemia cells is associated with expression of the c-myb proto-oncogene, c-Myb was investigated as a trans-activator of the topo IIalpha gene. Using topo IIalpha promoter-luciferase reporter plasmids, c-myb expression caused trans-activation of the topo IIalpha promoter a maximum of approximately 4.5-fold over basal levels in HL-60 human promyelocytic leukemia cells. Trans-activation was submaximal with higher levels of c-myb expression plasmid but a Myb protein lacking its negative regulatory domain resulted in approximately 19-fold trans-activation. Mutagenesis and 5'-deletion studies revealed that Myb trans-activation was mediated via a Myb-binding site at positions -16 to -11 and that this region governed the bulk of basal topo IIalpha promoter activity in human leukemia cells. Trans-activation of topo IIalpha by c-Myb was lymphoid- or myeloid-dependent. However, B-Myb, a more widely-expressed Myb family member, caused topo IIalpha trans-activation in both HL-60 cells and HeLa epithelial cervical carcinoma cells. These data provide evidence for a new Myb-responsive gene which is directly linked to and required for cellular proliferation.
 ...
PMID:c-Myb trans-activates the human DNA topoisomerase IIalpha gene promoter. 904 45

The cyclopentenone PGs (PGA and PGJ series) inhibit tumor cell proliferation in vitro and tumorigenesis in vivo via mechanisms that are at present poorly understood. The C6 rat glioma cell line synthesizes and secretes insulin-like growth factor-I (IGF-I), which is believed to act as an autocrine factor for these cells. PGA2 inhibits the proliferation of the C6 cells and causes an increase in the fraction of cells in the G1 phase of the cell cycle. The inhibition of cell proliferation by PGA2 is accompanied by a decrease in the abundance of IGF-I messenger RNA (mRNA). This regulation of IGF-I gene expression is specific, as the abundance of hypoxanthine-guanine phosphoribosyl transferase (HPRT) and ubiquitin mRNA is not significantly affected by PGA2. The repression of IGF-I gene expression is observed at PGA2 concentrations as low as 10 microM and is evident within 4 h after treatment of the C6 cells with PGA2. In addition to specifically regulating the expression of the IGF-I gene, PGA2 also decreases the abundance of cyclin D1 mRNA and increases the abundance of Waf1 mRNA. The inhibition of cell proliferation by PGA2 is partially reversed by coaddition of IGF-I, indicating partial dominance of IGF-I action over PGA2 action. To investigate the molecular basis for the regulation of IGF-I gene expression by PGA2, we developed a sensitive RT-PCR assay for IGF-I nuclear transcripts. A similar assay was developed for quantifying HPRT transcripts, which were used as a control. Treatment of the C6 cells with 20 microM PGA2 resulted in approximately a 6-fold decrease in IGF-I mRNA and IGF-I nuclear transcripts. In contrast, HPRT mRNA and nuclear transcript levels were not significantly affected by PGA2. These results indicate that the decrease in IGF-I mRNA abundance that occurs in response to PGA2 is caused largely by a decrease in IGF-I nuclear transcript levels. To identify the cis-acting element that mediates the effect of PGA2 on IGF-I transcription, C6 cells were transiently transfected with IGF-I/luciferase expression constructs in which luciferase transcription is driven by IGF-I P1 promoter fragments extending from -1711 to -328 or from -1114 to +328 relative to the beginning of exon 1. Treatment of cells with PGA2 in these transient transfection assays did not decrease luciferase activity. These results suggest that the cis-acting regulatory element required for the response to PGA2 is located outside the -1711 to +328 promoter interval.
 ...
PMID:Prostaglandin A2 specifically represses insulin-like growth factor-I gene expression in C6 rat glioma cells. 904 99


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>