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dc.contributor.advisorSafe, Stephen H.en_US
dc.creatorAbdel Rahim, Ma'en Ahmaden_US
dc.date.accessioned2004-09-30T01:46:37Z
dc.date.available2004-09-30T01:46:37Z
dc.date.created2004-05en_US
dc.date.issued2004-09-30
dc.identifier.urihttp://hdl.handle.net/1969.1/218
dc.description.abstractSequence-specific small interfering RNA (siRNA) duplexes can be used for gene silencing in mammalian cells and as mechanistic probes for determining gene function. Transfection of siRNA for specificity protein 1 (Sp1) in MCF-7 or ZR-75 cells decreased Sp1 protein in nuclear extracts, and immunohistochemical analysis showed that Sp1 protein in transfected MCF-7 cells was barely detectable. Decreased Sp1 protein in MCF-7 was accompanied by a decrease in basal and estrogen-induced transactivation and cell cycle progression. These results clearly demonstrate the key role of Sp1 protein in regulating growth and gene expression of breast cancer cells. The aryl hydrocarbon (AhR) is a ligand-activated nuclear transcription factor. siRNA for the AhR decreased TCDD-induced CYP1A1 protein, CYP1A1dependent activity, and luciferase activity in cells transfected with an Ah-responsive construct. 17β-Estradiol (E2) induces proliferation of MCF-7 cells, and this response is inhibited in cells cotreated with E2 plus TCDD. The effects of TCDD on E2-induced cell cycle progression were partially blocked in MCF-7 cells transfected with siRNA for AhR. The decrease in AhR protein in MCF-7 cells was also accompanied by increased G0/G1 → S phase progression. Surprisingly, TCDD alone induced G0/G1 → S phase progression and exhibited estrogenic activity in MCF-7 cells transfected with siRNA for the AhR. In contrast, degradation of the AhR in HepG2 liver cancer cells resulted in decreased G0/G1 → S phase progression, and this was accompanied by decreased expression of cyclin D1, cyclin E, cdk2 and cdk4. In the absence of ligand, the AhR exhibits growth inhibitory (MCF-7) and growth promoting (HepG2) activity that is cell context-dependent. Sp family proteins play a complex role in regulation of pancreatic cancer cells growth and expression of genes required for growth, angiogenesis and apoptosis. Sp1, Sp3 and Sp4 cooperatively activate VEGF promoter constructs in these cells; however, only Sp3 regulates cell proliferation. siRNA for Sp3 inhibits phosphorylation of retinoblastoma protein, blocks G0/G1 → S phase progression of Panc-1 cells, and upregulates p27 protein/promoter activity. Thus, Sp3 plays a critical role in angiogenesis (VEGF upregulation) and the proliferation of Panc-1 cells by a novel mechanism of Sp3-dependent suppression of the cyclin-dependent kinase inhibitor p27.en_US
dc.format.extent7592584 bytes
dc.format.extent333636 bytes
dc.format.mediumelectronicen_US
dc.format.mimetypeapplication/pdf
dc.format.mimetypetext/plain
dc.language.isoen_USen_US
dc.publisherTexas A&M Universityen_US
dc.subjectRNAien_US
dc.subjectsiRNAen_US
dc.subjectSp proteinsen_US
dc.subjectTCDDen_US
dc.subjectAhRen_US
dc.subjectARNTen_US
dc.subjectVEGFen_US
dc.subjectbreast canceren_US
dc.subjectpancreatic cancer.en_US
dc.titleGene silencing in cancer cells using siRNA : genetic and functional studiesen_US
dc.typeBooken
dc.typeThesisen
thesis.degree.departmentVeterinary Physiology and Pharmacologyen_US
thesis.degree.disciplineToxicologyen_US
thesis.degree.grantorTexas A&M Universityen_US
thesis.degree.nameDoctor of Philosophyen_US
thesis.degree.levelDoctoralen_US
dc.contributor.committeeMemberPhillips, Timothy D.en_US
dc.contributor.committeeMemberPorter, Weston W.en_US
dc.contributor.committeeMemberDonnelly, Kirby C.en_US
dc.type.genreElectronic Dissertationen_US
dc.type.materialtexten_US
dc.format.digitalOriginborn digitalen_US


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