Browsing by Subject "estrogen receptor"
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Item Analysis of some novel uterine extracellular matrix proteins and a growth factor(2009-05-15) Al Ramadan, Saeed YaseenThis dissertation focused on two classes of molecules implicated in processes of implantation and placentation in sheep and pigs. Study one examined the temporal/spatial distribution of several Small Integrin-Binding Ligand, N-Linked Glycoprotein (SIBLING) family members in cyclic and pregnant ovine uterus. Studies two and three evaluated the relationships between progesterone (P4) and estrogen (E2) and their receptors (PGR and ESR1, respectively) on FGF7 mRNA expression within the endometrium and placenta of pigs. Study one showed that dentin sialophosphoprotein (DSPP) was first detected in luminal epithelium (LE) of Day 15 cyclic and pregnant sheep. Stromal expression of DSPP was first detected on Day 20 of pregnancy in stratum compactum and remained prominent in stroma through Day 120. Stromal DSPP protein was positively influenced by the conceptus based upon analysis of a unilaterally pregnant ewe model system. Immunoreactive dentin matrix protein 1 (DMP1), matrix extracellular phospoglycoprotein (MEPE) were localized to the stroma of cyclic and pregnant sheep, however, these proteins appeared to be constitutively expressed. BSP was not detected in ovine endometrium. Study two determined the effects of E2, P4, P4+E2, P4+the PGR antagonist (ZK137, 316), and P4+E2+ZK on FGF7 mRNA expression in uterine LE of ovariectomized pigs. Results indicate that P4 is permissive to FGF7 mRNA expression by down-regulating PGR in LE; P4 stimulates PGR-positive uterine stromal cells to release an as yet unidentified progestamedin that induces FGF7 mRNA expression by LE; E2 and P4 can induce FGF7 mRNA in the absence of PGR rendered nonfunctional by ZK. Study three showed the expression of ESR1, PGR and FGF7 in the uterine and placental tissue of pregnant pigs from Day 20 through 85. Results reveal a positive correlation between stromal cell expression of PGR and FGF7 mRNA which suggests that P4 is permissive to FGF7 mRNA expression by down-regulating PGR in LE. FGF7 mRNA in later pregnancy is maintained by the release of progestamedin from PGR-positive stromal cells. A novel finding was the presence of ESR1 in porcine placenta on Days 20 through Day 85 of pregnancy suggesting that E2 may play important roles in the placental biology of the pig.Item Comparative activation of estrogen receptor alpha (er alpha) by endocrine disruptors(2009-05-15) Wu, FeiEstrogen receptor ? (ER?) is a ligand activated transcription factor. Many widely used synthetic compounds and natural chemicals can activate ER?. The compounds investigated in this study include 17?-estradiol (E2), diethylstilbestrol (DES), antiestrogens ICI 182,780, 4-hydroxytamoxifen, the phytoestrogen resveratrol, and the xenoestrogens bisphenol A (BPA), nonylphenol (NP), octylphenol (OP), endosulfan, kepone, 2,2-bis(p-hydroxyphenyl)-1,1,1- trichloroethane (HPTE) and 2,3,4,5-tetrachlorobiphenylol-4-ol (HO-PCB-Cl4). With the exception of the antiestrogens, all the compounds induced transactivation in MCF-7 or MDA-MB-231 cells transfected with wild-type ER? and a construct (pERE3) containing three tandem estrogen responsive elements (EREs) linked to a luciferase gene. However, these compounds differentially activated C-terminal deletion mutants of ER?. For example, neither E2 nor DES induced transactivation in MCF-7 transfected with ER?(1-537) due to partial deletion of helix 12 of ER?; however, OP, NP, resveratrol, kepone and HPTE induced this ER? mutant, demonstrating that the estrogenic activity of these synthetic compounds do not require activation function 2 (AF-2) of ER?. This study also investigated the effects of xenoestrogens on activation of reporter gene activity in MCF-7 and MDA-MB-231 cells transfected with a construct (pSp13) containing three tandem GC-rich Sp binding sites linked to the luciferase gene. In MCF-7 cells, antiestrogen-induced activation of ER?/Sp1 required the zinc finger motifs of ER?, whereas activation by estrogen and some xenoestrogens activation, such as endosulfan, NP and OP required the H12 of ER?. In contrast, xenoestrogens, such as HPTE, BPA, kepone and HO-PCBCl4, significantly induced transactivation of all four ER? deletion mutants tested in this study. Moreover, RNA interference assays demonstrated structuredependent differences in activation of ER?/Sp1, ER?/Sp3 and ER?/Sp4. The in vivo activities of E2, ICI 182,780, BPA and NP were further investigated in a transgenic mouse model containing pSp13 transgene. All the compounds induced luciferase activity in the mouse uterus; however activities observed in the penis and testis of male and stomach of both male and female mice were structure-dependent,. These results demonstrate that various ER ligands differentially activate ER? in breast cancer cells and transgenic mice, and their activities are dependent on ER? variants, promoter-, cell-context and selective use of different Sp proteins, suggesting these structurally diverse compounds are selective ER modulators (SERMs).Item Inhibitory actions of Ah receptor agonists and indole-containing compounds in breast cancer cell lines and mouse models(Texas A&M University, 2005-08-29) Walker, Kelcey Manae BeckerThe aryl hydrocarbon receptor (AhR) binds synthetic and chemoprotective phytochemicals, and research in this laboratory has developed selective AhR modulators (SAhRMs) for treatment of breast cancer. Activation of the AhR through agonists such as TCDD inhibits hormone activation of several E2-responsive genes in breast cancer cell lines. In this study, inhibition of E2-induced proliferation and gene expression by TCDD has been investigated in the uterus of wildtype, ERKO and AhRKO mice. Cyclin D1, DNA polymerase ?, and VEGF mRNA levels are induced by E2 through ER? in the uterus as determined by in situ hybridization studies. TCDD down-regulated E2-induced cyclin D1 and DNA polymerase ? expression, but not E2-induced VEGF expression, in wild-type mice, but not AhRKO mice, confirming the role of the AhR. Furthermore, protein synthesis was not necessary for induction of cyclin D1 or DNA polymerase ?gene expression by E2 or inhibition of these responses by TCDD. Therefore, AhR-ER? crosstalk directly regulates the expression of genes involved in cell proliferation in vivo. AhR agonists induce down-regulation of ErbB family receptors in multiple tissues/organs suggesting possible inhibitory interactions with chemotherapeutic potential. Recently, it has been reported that the SAhRM 1,1??,2,2??-tetramethyldiindolylmethane inhibited DMBA-induced mammary tumor growth in rats and also inhibited MAPK and PI3-K pathways in human breast cancer cells. BT-474 and MDA-MB-453 cell lines are ErbB2-overexpressing breast cancer cells that express functional AhR and exhibit constitutive activation of MAPK and PI3-K pathways. Therefore, 1,1??,2,2??-tetramethyldiindolylmethane-induced inhibition of ErbB2 signaling was investigated in these cells lines and in the MMTV-c-neu mouse mammary tumor model, which overexpresses ErbB2 in the mammary gland. The growth of ErbB2 overexpressing cell lines and mammary tumors was inhibited by 1,1??,2,2??-tetramethyldiindolylmethane; however, modulation of MAPK or PI3-K pathways and cell cycle proteins nor induction of apoptosis by 1,1',2,2'-tetramethyldiindolylmethane was observed in the ErbB2overexpressing cell lines. Current studies are investigating mitochondrial effects of 1,1??,2,2??-tetramethyldiindolylmethane in the ErbB2-overexpressing cell lines, as well as continuing studies on gene expression profiles in the mammary glands of MMTV-c-neu mice to better understand and identify critical genes that are responsible for ErbB2-mediated transformation and growth of cancer cells/tumors.Item Mechanisms of coactivation of estrogen receptor alpha (ER alpha)- and ER alpha/Sp-mediated gene transactivation by vitamin D receptor interacting protein 205 (DRIP205) in breast cancer cells(2009-05-15) Wu, QianVitamin D interacting protein 205 (DRIP205) is a mediator complex protein that anchors the complex to the estrogen receptor (ER) and other nuclear receptors (NRs). In ZR-75 breast cancer cells treated with 17?-estradiol (E2) and transfected with a construct containing three tandem estrogen responsive elements (pERE3), DRIP205 coactivates ER?-mediated transactivation. DRIP205?587-636 is a DRIP205 mutant in which both NR boxes within amino acids 587-636 have been deleted and, in parallel transfection studies, DRIP205?587-636 also coactivates ER?. Moreover, both wild-type and variant DRIP205 also colocalize with ER? in the nuclei of transfected cells. AF1 and AF2 of ER? are both required for DRIP205 coactivation. Extensive deletion analysis of DRIP205 shows that multiple domains of this protein play a role in coactivation of ER? and in interactions with ER?. On the other hand, both DRIP205 and DRIP205?587-636 coactivate E2-induced transactivation of ER?/Sp1 in cells transfected with a construct containing three GC-rich sites (pSp13). Coactivation of ER?/Sp1 by DRIP205 is dependent on AF1 of ER?. Enhancement of ER? and ER?/Sp1 by DRIP205 does not require NR boxes of DRIP205, and deletion mutants DRIP205 (1-714) and DRIP205 (516-1566) significantly coactivate ER? and ER?/Sp1. RNA interference study showed that DRIP205 coactivation of ER?/Sp was abolished in cells transfected with iSp3 and iSp4, suggesting that Sp3 and Sp4 are required for coactivation of ER?/Sp by DRIP205 in ZR-75 cells.Item The Protective Effects of Estradiol on Sporadic and Inflammation-associated Colon Cancer(2013-11-22) Armstrong, Cameron MichelleEpidemiological studies suggest pre-menopausal women have a reduced risk for sporadic and inflammation-associated colon cancer compared to post-menopausal women and men. The studies presented herein aim to determine the protective mechanisms of estradiol (E2) during sporadic and inflammation-associated colonic carcinogenesis. When investigating the role of E2 and fish oil at the earliest stage of sporadic colon cancer development, E2 had no effect on DNA adduct formation while dietary fish oil significantly reduced DNA adduct formation. Contrarily, E2 significantly induced apoptosis of damaged colonocytes while fish oil was not protective. In an in vivo model of inflammation-associated colon carcinogenesis with E2 administered following induction of DNA damage and initiation of inflammation, E2 treatment was associated with decreased colon tumor size and number in wild type (WT) but not estrogen receptor (ER) ? knockout (ER?KO) mice. Interestingly, apoptosis was reduced and proliferation increased by E2 in these tumors in WT mice. This may be due to the altered ER expression in these tissues as the tumors developed, with ER??expression decreasing concomitantly with ER? expression increasing. Contrary to the protective effect of E2 on inflammation-associated colon tumor formation, which was dependent on ER?, during acute inflammation in the colon E2 was protective against inflammation in both WT and ER?KO mice and injury in ER?KO mice. The protection against inflammation is likely due to the reduction of pro-inflammatory cytokine expression by E2. Apoptosis and proliferation were decreased and increased in the proximal and distal colon respectively in ER?KO mice. In vitro studies further elucidated the roles of ER? and ER? in colonocytes. E2 and ER?, but not ER?, specific agonists reduced cell number and induce apoptosis in nonmalignant colonocytes. This effect was lost in the presence of mutated p53. In ER? overexpressed nonmalignant colonocytes, E2 had no effect on cell number while ER? agonist and ER? agonists decreased and increased cell number respectively. These studies suggest that E2 is protective in the colon and ER? is required for protection against carcinogenesis but not protection against inflammation. Additionally, the protection against colon carcinogenesis is likely p53 mediated.