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)

Endocrine factors involved in the transcriptional regulation of the oxytocin (OT) gene were investigated in heterologous expression systems. Plasmids having a 5'-flanking region of the rat OT gene (-363/+16) or the human OT gene (-382/+41) cloned in front of the firefly luciferase gene were co-transfected with an expression vector for the rat thyroid hormone receptor alpha in P19 embryonal carcinoma (EC) cells. Thyroid hormone (T3) stimulated the activity of the rat and human OT promoters about 10-fold. In MCF-7 breast tumor cells transfected with the human OT promoter-luciferase fusion gene, T3 stimulation through endogenous thyroid hormone receptors was about 5-fold. Co-transfection experiments in P19EC cells using 5' deletion mutants of the rat OT gene showed that thyroid hormone responsiveness was located in two regions, one located between nucleotides -195 and -172, the other between nucleotides -172 and -148. Each region accounted for about 3-fold T3 stimulation. Gel retardation analysis using extracts from HeLa cells over-producing the c-erbA/TR alpha protein showed specific binding to the -172/-148 element, while no binding occurred on the -195/-172 element. The -172/-148 element which contains the imperfect estrogen response element, GGTGACCTTGACC, has inverted as well as direct repeats of the TGACC motif. Mutagenesis of TGACC motifs separately reduced thyroid hormone responsiveness by about 50%. However, simultaneous mutation of two TGACC motifs abolished the responsiveness to T3 completely. There was no cooperativity between the activated thyroid hormone and estrogen receptors in transfected MCF-7 cells nor in thyroid hormone receptor and estrogen receptor co-transfected P19EC cells. Negative interactions between these two receptors were observed and gel retardation assays showed interaction between the two receptors proteins. It was shown in an in vivo experiment that treatment of rats with thyroid hormone increased hypothalamic OT mRNA levels, the pituitary OT content, as well as OT levels in blood. The results reveal thyroid hormone as a physiological regulator of OT gene expression, which stimulates OT promoter activity directly through interaction with a thyroid hormone-response element in the OT gene.
 ...
PMID:Thyroid hormone regulates the oxytocin gene. 137 Dec 78

Proliferation-competent and differentiation-competent adult rat hepatocytes in primary culture were investigated for their ability to express reporter genes (firefly luciferase, bacterial chloramphenicol acetyltransferase, and bacterial beta-galactosidase) driven by tumor virus or eucaryotic promoters that vary in transcriptional efficiency and tissue specificity. Supercoiled plasmid DNA molecules were introduced into the cells by the calcium phosphate coprecipitation protocol of C. Chen and H. Okayama (Mol. Cell. Biol. 7:2745-2752, 1987). Reporter gene expression was virtually restricted to hepatocytes and was efficient (2 to 20% of the cells). The patterns and absolute levels of reporter gene expression depended on assay conditions employed (plasmid concentration [optimal at 2.4 micrograms of DNA per ml] and duration of exposure [optimal between 5 and 10 h]), culture growth cycle stages (lag, log, or stationary phase), properties and tissue specificity of the promoter(s) tested, and composition (and timing of fluid change) of the culture medium with or without the hepatocyte mitogen human transforming growth factor-alpha. Initial observations suggest that during hepatocellular growth transitions, human transforming growth factor-alpha differentially regulates exogenously introduced promoters associated with hepatocyte-specific function and proliferation. These findings provide a simple, fast, and powerful approach to analyzing the molecular and cellular biology of hepatocyte growth control.
 ...
PMID:DNA-mediated gene transfer into adult rat hepatocytes in primary culture. 210 58

In TtT 97 cells, a thyrotropin-producing mouse pituitary tumor, thyroid hormone rapidly inhibits the transcription rate of both the thyrotropin alpha- and beta-subunit (TSH beta) genes, and this closely parallels the increase in nuclear thyroid hormone receptor occupancy. In this study, we have identified regions of the mouse TSH beta gene which are involved in mediating tissue-specific and thyroid hormone-regulated expression. Transient expression studies were performed using a series of chimeric plasmids in which 5'-flanking DNA was ligated to the firefly luciferase gene. Following transfection by electroporation, efficient expression of TSH beta 5'-flanking luciferase constructs occurred only in cells derived from TtT 97 tumors which express the endogenous TSH beta gene. Deletion analysis demonstrated that the region of the 5'-flanking DNA between positions -271 and -80 relative to the major transcriptional start site is important for TSH beta promoter activity in thyrotropes. No expression was measurable in mouse L cells, a fibroblast line, whereas a low level of expression was seen in MGH 101A cells derived from a thyrotropic tumor which no longer expresses the TSH beta gene. Reduced expression of TSH beta constructs was also found in GH3 and GH4 pituitary tumor lines. Addition of thyroid hormone effectively inhibited the level of transient TSH beta promoter activity in TtT 97 cells in a dose-dependent manner. The inhibitory effect was more pronounced and more accurately reflected the transcription rate data when transfected cells were derived from tumors treated with thyroid hormone for 5 days prior to transfection. Deletion of all but 46 base pairs of TSH beta gene 5'-flanking DNA and 3 base pairs of the first exon had no effect on thyroid hormone inhibition. This indicates that signals sufficient for transcriptional regulation of the TSH beta gene by thyroid hormone reside in the vicinity of the proximal promoter and may act by interfering with basal transcriptional factors.
 ...
PMID:Thyroid hormone regulates the mouse thyrotropin beta-subunit gene promoter in transfected primary thyrotropes. 276 43

Direct in vivo transfection of tumor nodules in situ via liposome-DNA complexes has been employed as a strategy to accomplish antitumor immunization. To circumvent the potential safety hazards associated with systemic localization of delivered DNA, the utility of mRNA transcript-mediated gene delivery was explored. Capped, polyadenylated mRNA transcripts encoding the firefly luciferase and Escherichia coli lacZ reporter genes were derived by in vitro transcription. Transfection of the human breast cancer cell line MDA-MB-435 in vitro was accomplished employing cationic liposome-mRNA complexes. Evaluation of a panel of cationic liposome preparations demonstrated significant differences in the capacity of the various preparations to accomplish mRNA-mediated transfection. Quantitative evaluation of in vitro transfection demonstrated that target cells could be transfected at a high level of efficiency. The mRNA liposome-complexes were evaluated for in vivo transfection of tumor nodules in human xenografts in athymic nude mice. It could be demonstrated the liposome-mRNA complexes were comparable in efficacy to liposome-DNA complexes in accomplishing in situ tumor transfection. Thus, mRNA may be considered as an alternative to plasmid DNA as a gene transfer vector for genetic immunopotentiation applications.
 ...
PMID:Optimization of methods to achieve mRNA-mediated transfection of tumor cells in vitro and in vivo employing cationic liposome vectors. 762 14

Mouse Leydig MA-10 tumor cells are a good model of testicular steroidogenesis. The endogenous murine P450scc mRNA in these cells accumulated in response to 8-bromo-cAMP, forskolin, cholera toxin, and 1-methyl-3-isobutylxanthine, but not in response to 1,9-dideoxyforskolin, indicating that this accumulation was stimulated by the protein kinase-A pathway. Inhibiting transcription with actinomycin-D showed that the half-life of cytochrome P450scc mRNA in these cells was not altered by cAMP, consistent with earlier nuclear run-on data showing that the effect of cAMP on P450scc is at the transcriptional level. A series of 17 fragments of 5'-flanking DNA from the human P450scc gene were fused to the gene for firefly luciferase and transiently transfected into MA-10 cells. The longest construct, containing 2327 basepairs of 5'-flanking DNA, responded 4-fold to forskolin and, hence, was used to optimize the forskolin dose response, showing that 30 microM forskolin elicited a 90% maximal effect. Examination of the activity of the deletion constructs located basal and cAMP-responsive sequences. Constructions containing 79 basepairs of 5'-flanking DNA had basal activity; adding sequences between -79 and -110 had minimal effect, but adding sequences between -110 and -127 increased basal activity 3-fold. Adding sequences beyond -127 did not increase basal transcription further, indicating the presence of a basal transcription element between -110 and -127. These serial deletion mutants were used similarly to locate cAMP responsiveness between -1620 and -1676, indicating the presence of a cAMP response element in this region. The locations of these basal and cAMP-responsive sequences correspond well with those previously identified when human P450scc promoter/reporter constructions were transfected into mouse adrenocortical Y-1 cells, but differ from those identified when such constructions were transfected into human JEG-3 choriocarcinoma cells.
 ...
PMID:Basal transcriptional activity and cyclic adenosine 3',5'-monophosphate responsiveness of the human cytochrome P450scc promoter transfected into MA-10 Leydig cells. 767 94

The cytotoxic efficacy of antitumor drugs targeted at DNA topoisomerase II (topo II) in many cases varies in direct proportion to cellular topo II content. To investigate the transcriptional control of the predominant alpha form of topo II, the 5' flanking region of the human topo II alpha gene (positions -562 to +90) was subcloned into a firefly luciferase reporter plasmid and transiently transfected into HL-60 human leukemia cells, a line capable of monocytic differentiation after treatment with various agents. Early in phorbol-12-myristate-13-acetate (30 nM)-induced differentiation (18-24 hr after treatment), an unexpected 3-5-fold activation of topo II alpha gene promoter activity was observed. Activation was observed in HL-60 cells and U-937 cells, but not in HeLa human cervical carcinoma cells. Sodium butyrate (NaB) (0.4 mM) also led to activation (4-17-fold) of the topo II alpha promoter in HL-60 and U-937 cells. Promoter sequences between position -90 and position +90 mediated the inducing effects of NaB. This NaB-dependent promoter-reporter induction was partly mirrored by a transient approximately 2-fold increase in endogenous topo II alpha enzyme. The stimulus for promoter activation could be partly attributed to a 2-fold increase in DNA synthesis at 16 hr for NaB, but not phorbol-12-myristate-13-acetate. Regardless of the primary stimulus for topo II alpha promoter trans-activation, it could be bypassed by treatment of HL-60 cells with NaB for 48 hr before transfection, revealing the expected 60-70% suppression of topo II alpha promoter activity. Further study of topo II alpha promoter down-regulation later in monocytic differentiation may serve as a model for elucidating the transcriptional mechanisms that may also be exploited by tumor cells expressing intrinsic or acquired resistance to topo II-directed drugs.
 ...
PMID:Topoisomerase II alpha promoter trans-activation early in monocytic differentiation of HL-60 human leukemia cells. 772 30

WERI-Rb27 human retinoblastoma cells were reconstituted with an intact RB gene by retrovirus-mediated gene transfer, in order to study the phenotypic effects of the protein in vitro and in vivo. Extensive morphological changes were observed, dominated by the formation of multinucleated giant cells. Six weeks after retroviral infection, the giant cells began to die and small cells emerged, resembling the parental non-reconstituted line. They expressed RB and continued to grow, although they showed an increased sensitivity to serum starvation. The original RB-negative cells grew progressively after subcutaneous inoculation into SCID mice, whereas the reconstituted cells failed to grow. RB-positive cells grew progressively in the corpus vitreum of the eye and in the brain, however. The RB-reconstituted cells grew more slowly and were less invasive than the parental cells and cells infected with a firefly luciferase (LUX) gene carrying retrovirus, used as controls. RB-reconstituted cells re-explanted from the intraocular and intracranial tumors continued to express full-length RB protein. RBeye2, an RB-positive cell line established from an eye tumor, was still unable to grow subcutaneously. The reduced tumorigenicity of the RB-reconstituted cells in the subcutaneous space may be due to the influence of locally acting growth-controlling signals or the absence of microenvironment-specific trophic factors. Alternatively, it may reflect the action of residual immune effectors in the SCID mice. If this is the case, these would have to be more effective at the subcutaneous site than in the eye or brain.
 ...
PMID:RB-reconstituted human retinoblastoma cells form RB-positive intraocular and intracerebral but not subcutaneous tumors in SCID mice. 776 42

The gene encoding firefly luciferase has been used as a reporter gene for the study of gene function. The luciferase catalyzes its substrate and subsequently produces luminescence. In addition, it is not present in mammalian cells. We have therefore explored its use in monitoring the growth of tumors in vivo. The luciferase gene was transfected into two murine tumor lines, i.e. c162 melanoma and M109 lung carcinoma, and the luciferase activity associated with the cells was determined by a rapid chemiluminescent reaction. Luciferase activity was well-correlated with the number of tumor cells in vitro. Luciferase activity also correlated with the tumor burden in vivo, as well as with the effect of an adoptive T cell transfer therapy in the syngeneic C3H/HeN mice experimental tumor model. This assay offers the advantage of being quantitative, rapid, and reliable for the detection of tumor burden and for the evaluation of the effect of antineoplastic therapy.
 ...
PMID:Luciferase activity as a marker of tumor burden and as an indicator of tumor response to antineoplastic therapy in vivo. 830 31

Anti-gene is a potent inhibitor of transcriptional promoter activity and subsequent gene expression. This property has been exploited to suppress the expression of a variety of oncogenes for regulating tumor proliferation or viral activities. In this paper, we describe a novel retroviral vector designed to express human c-erbB anti-gene RNA and to reduce the promoter activity in the cells. Mouse fibroblast NIH3T3 cells were stably transfected with an expression construct containing a truncated human c-erbB gene promoter fused to the firefly luciferase reporter gene. Infection into these cells of the c-erbB anti-gene retroviral vector targeted to the 26 bp pyrimidine-rich element in the human c-erbB gene promoter resulted in a dose-dependent decrease in the luciferase activity of the cells. Retroviral vector expressing anti-gene RNA may be useful as an alternative program of gene regulation in the cells.
 ...
PMID:Inhibition of gene expression from the human c-erbB gene promoter by a retroviral vector expressing anti-gene RNA. 936 10

The expression of the Epstein-Barr virus (EBV) latent membrane protein 1 (LMP1) oncogene is tightly regulated by viral and cellular factors. LMP1 is present in the majority of nasopharyngeal carcinoma tumor cells and in Reed-Sternberg cells from Hodgkin's lymphoma, in which the only EBV nuclear antigen detected is EBNA1. The aim of this study was to test whether mutations affecting LMP1 gene expression were present in lymphoproliferative disorders, and, if so, whether their presence correlated with the clinical course of the disease. For this purpose we characterized the LMP1 promoter region from seven cases including two patients with aggressive Hodgkin's disease and two with atypical lymphoproliferative syndromes. Our results show that the sequences -298 to +29 relative to the transcription start site diverged up to 9.3% when compared with the prototype EBV strain B95-8. The cAMP responsive-like element (CRE), located at positions -37 to -44, was found to be mutated in 3 of the 7 cases. Functional analysis of transfected human embryonic kidney 293 cells using the firefly luciferase reporter gene revealed that mutations within the CRE site led to a 70% mean decrease in reporter activity. Our analysis indicates that in lymphoproliferative disorders, naturally occurring LMP1 variants that exhibit weak promoter activity are still associated with clinically progressive disease.
 ...
PMID:Molecular and functional analysis of the Epstein-Barr virus LMP1 oncogene promoter in lymphoproliferative diseases. 940 91


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