Differential regulation of vascular endothelial growth factor (VEGF) gene expression by 17β-estradiol in human breast and endometrial cancer cell lines /
Vascular endothelial growth factor (VEGF) is expressed in multiple hormone-dependent cancer cells and tumors in response to hypoxia, hypoglycemia, growth factors and hormones. Treatment of HEC1A endometrial cancer cells with 10 nM 17β-estradiol (E2) resulted in decreased VEGF mRNA expression, while...
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
2002.
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| Subjects: | |
| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=726462381&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | Vascular endothelial growth factor (VEGF) is expressed in multiple hormone-dependent cancer cells and tumors in response to hypoxia, hypoglycemia, growth factors and hormones. Treatment of HEC1A endometrial cancer cells with 10 nM 17β-estradiol (E2) resulted in decreased VEGF mRNA expression, while treatment of ZR-75 human breast cancer cells with E2 resulted in increased VEGF mRNA levels. Similar responses were observed in each cell line following transient transfection with pVEGF1, a plasmid containing the -2018/+50 VEGF promoter upstream of luciferase. Deletion and mutation analysis revealed that a guanine/cytosine (GC)-rich element at -66/-47 was the minimal E2-responsive element required in both cell lines, and the -66/-47 oligonucleotide bound Sp1 and Sp3 proteins in E2-treated nuclear extracts from HEC1A or ZR-75 cells. Downregulation of VEGF by E2 in HEC1A cells was attributed to a novel ER[]/Sp3 protein complex formation, and this interaction was confirmed in co-immunoprecipitation, GST pull-down, in vitro footprinting assays, and by overexpression of dominant negative Sp3. Upregulation of VEGF in ZR-75 cells depended on Sp1 and Sp3 proteins, as demonstrated by cotransfection of antisense or dominant negative Sp1/Sp3 plasmids, and chromatin immunoprecipitation (ChIP) assays. Furthermore, the pure antiestrogen ICI 182,780 and selective arylhydrocarbon receptor (AhR) modulator (SAhRM) 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) decreased E2-induced VEGF promoter activity in cells transfected with the minimal -66/-47 element. The antiestrogenic effect of TCDD was observed under normoxic conditions, was blocked under hypoxic conditions and required overexpression of AhR protein to restore downregulation by TCDD. Lastly, treatment of ZR-75 cells with E2, TCDD or hypoxia resulted in decreased levels of ER[] protein by Western blot and immunohistochemistry analyses, and this degradation of ER[] was attributed to increased proteasome activity. Decreased ER[] levels resulted in loss of basal and inducible binding to a consensus estrogen response element (ERE), and decreased activation of E2-inducible gene, pS2 or p(ERE)₃Luc reporter plasmid. Treatment of hypoxic cells with proteasome inhibitor MG132 reversed hypoxic downregulation of ER[] protein levels, while treatment with a protease inhibitor CAL2 did not. E2, hypoxia and TCDD modulate levels of VEGF and ER[] in tumor cells, and this may have implications for clinical treatment of hormone-dependent cancers. |
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| Item Description: | Vita. "Major Subject: Toxicology". |
| Physical Description: | xv, 255 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilm Inc. |
| Bibliography: | Includes bibliographical references (leaves 190-254). |