Browsing by Subject "Breast Cancer"
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Item Magazine coverage of breast cancer in 1993 and 2003: a qualitative content analysis(Texas A&M University, 2005-08-29) Reyes, Naomi LouiseBreast cancer has touched the lives of countless people, yet many women have misconceptions about the disease. One of the most common sources for breast cancer information used by American women is popular magazines. The current study sought to describe the content of magazine articles on breast cancer from 1993 and 2003 in an attempt to determine whether article content differed, and if so, in what ways and for what reasons. Topical theme, identification of risk factors, preventive measures, and sources mentioned were categories developed to determine possible differences in content between the two years. Twice as many articles on breast cancer appeared in 1993 as in 2003. In 1993, living with breast cancer was a theme of many articles, while in 2003, hormone replacement therapy was a dominant theme. Family history was emphasized as a risk factor in articles from 1993, while long-term hormone-replacement therapy was emphasized in 2003. In general, articles in 2003 focused on overall health practices in the possible prevention of breast cancer. Social, political, and scientific occurrences relating to breast cancer that took place from the early 1990s through 2003 were considered when analyzing content. Most of the differences in content appeared to reflect such occurrences.Item Mechanisms of hormonal regulation of CAD gene expression and inhibition by Aryl hydrocarbon receptor agonist in human breast cancer cells(Texas A&M University, 2007-04-25) Khan, Shaheen Munawar AliThe CAD gene is trifunctional and expresses carbamoylphosphate synthetase/aspartate carbamyltransferase/dihydroorotase, which are required for pyrimidine biosynthesis. CAD gene activities are induced in MCF-7 human breast cancer cells, and treatment of MCF-7 or ZR-75 cells with 17b-estradiol (E2) resulted in a 3-5 fold increase in CAD mRNA levels in both cell lines. E2 induced reporter gene activity in MCF-7 and ZR-75 cells transfected with a construct containing the growth-responsive -90/+115 (pCAD1) region of the CAD gene promoter, which contains three upstream GC-rich and two downstream E-box motifs. Deletion and mutation analysis of the CAD gene promoter demonstrated that only the GC boxes that bind Sp1 protein were required for E2-responsiveness. Results of gel shift and chromatin immunoprecipitation (CHIP) assays show that both Sp1 and estrogen receptor a (ERa) interact with the GC-rich region of the CAD gene promoter. Moreover, hormone-induced transactivation of pCAD1 was inhibited by cotransfection with dominant-negative Sp1 expression plasmid and small inhibitory RNA for Sp1. These results demonstrate that, in common with many other genes involved in E2-induced cell proliferation, the CAD gene is also regulated by a nonclassical ERa/Sp1-mediated pathway. 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) and other aryl hydrocarbon receptor (AhR) ligands suppress several E2-induced responses in the rodent uterus and mammary tumors and in human breast cancer cells. TCDD inhibited hormone-induced activation of CAD mRNA levels and reporter gene activity in MCF-7 and ZR-75 cells transfected with E2-responsive pCAD promoter constructs. E2-mediated transactivation of pCAD constructs with a mutant inhibitory dioxin responsive element DRE (iDRE) were also inhibited by TCDD suggesting that inhibitory AhR-ERa/Sp1 crosstalk was iDRE-independent. It was not possible to determine whether the levels of ERa in cells cotreated with E2 plus TCDD were limiting since the proteasome inhibitor MG132 itself directly decreased CAD mRNA levels. Using fluorescence resonance energy transfer (FRET), it was shown that both E2 and TCDD enhanced AhR-ERa interactions. E2 also induced interactions between ERa and Sp1. However cotreatment with TCDD abrogated this effect. Results of this study demonstrate a unique model of AhR-ERa crosstalk where the liganded AhR inhibits ERa-Sp1 interactions and also recruits ERa to Ahresponsive gene promoters such as CYP1A1.Item Regulation of E2F-1 gene expression in human breast cancer cells(Texas A&M University, 2005-08-29) Ngwenya, Sharon Khethiwe17?-Estradiol induces E2F-1 gene expression in ZR-75 and MCF-7 human breast cancer cells. Analysis of the E2F-1 gene promoter in MCF-7 cells previously showed that hormone-induced transactivation required interactions between estrogen receptor ? (ER?)/Sp1 bound to upstream GC-rich sites and NFYA bound to downstream CCAAT sites within the -169 to -54 promoter region. This promoter region was also E2-responsive in ER?-positive ZR-75 cells; however, further analysis of the promoter showed that cooperative ER?/Sp1/NFY interactions were not necessary for hormone-induced transactivation in ZR-75 cells. The upstream GC-rich motifs are activated independently by ER?/Sp1 in ZR-75 but not MCF-7 cells, and the downstream CCAAT sites were also E2-responsive. E2 also induced reporter gene activity in ZR-75 cells transfected with an expression plasmid containing the yeast GAL4 DNA binding domain fused to pM-NFYA and a construct containing five tandem GAL4 response elements. Subsequent studies showed that hormonal activation of pE2F-1jm1 and pM-NFYA are dependent on non-genomic pathways in which E2 activates cAMP/protein kinase A. Hormone-dependent regulation of E2F-1 gene expression in ZR-75 and MCF-7 involves different mechanisms, demonstrating the importance of cell context on transactivation pathways, even among ER-positive breast cancer cell lines. TCDD inhibited ER?-mediated responses in MCF-7 and ZR-75 cells. E2- induced E2F-1protein and mRNA levels in MCF-7 and ZR-75 cells and this response was inhibited by TCDD. Constructs containing GC-rich sites alone or in combination with the downstream NFY sites were used in transactivation studies to investigate the mechanism of inhibitory AhR-ER? crosstalk. Although TCDD inhibited E2-induced mRNA, protein and reporter gene actitivity, it was not possible to determine if the inhibitory response was due to limiting ER? protein levels due to proteasome degradation since proteaome inhibitors alone blocke hormone-dependent responses. TCDD also inhibited the cAMP/PKA pathway by inhibiting adenyl cyclase activity. In Drosophila SL-2 cells cotransfected with the GC-rich -169 to -54 region, ER? and Sp1 plasmids E2 induced transactivation in cells cotransfected with AhR/Arnt expression plasmids suggesting that the AhR complex suppressed ER?/Sp1 action. These results demonstrate that TCDD inhibits E2-dependent activation of both non-genomic and genomic pathways of ER-mediated E2F-1 gene expression. 17?-Estradiol induces E2F-1 gene expression in ZR-75 and MCF-7 human breast cancer cells. Analysis of the E2F-1 gene promoter in MCF-7 cells previously showed that hormone-induced transactivation required interactions between estrogen receptor ? (ER?)/Sp1 bound to upstream GC-rich sites and NFYA bound to downstream CCAAT sites within the -169 to -54 promoter region. This promoter region was also E2-responsive in ER?-positive ZR-75 cells; however, further analysis of the promoter showed that cooperative ER?/Sp1/NFY interactions were not necessary for hormone-induced transactivation in ZR-75 cells. The upstream GC-rich motifs are activated independently by ER?/Sp1 in ZR-75 but not MCF-7 cells, and the downstream CCAAT sites were also E2-responsive. E2 also induced reporter gene activity in ZR-75 cells transfected with an expression plasmid containing the yeast GAL4 DNA binding domain fused to pM-NFYA and a construct containing five tandem GAL4 response elements. Subsequent studies showed that hormonal activation of pE2F-1jm1 and pM-NFYA are dependent on non-genomic pathways in which E2 activates cAMP/protein kinase A. Hormone-dependent regulation of E2F-1 gene expression in ZR-75 and MCF-7 involves different mechanisms, demonstrating the importance of cell context on transactivation pathways, even among ER-positive breast cancer cell lines. TCDD inhibited ER?-mediated responses in MCF-7 and ZR-75 cells. E2- induced E2F-1protein and mRNA levels in MCF-7 and ZR-75 cells and this response was inhibited by TCDD. Constructs containing GC-rich sites alone or in combination with the downstream NFY sites were used in transactivation studies to investigate the mechanism of inhibitory AhR-ER? crosstalk. Although TCDD inhibited E2-induced mRNA, protein and reporter gene actitivity, it was not possible to determine if the inhibitory response was due to limiting ER? protein levels due to proteasome degradation since proteaome inhibitors alone blocke hormone-dependent responses. TCDD also inhibited the cAMP/PKA pathway by inhibiting adenyl cyclase activity. In Drosophila SL-2 cells cotransfected with the GC-rich -169 to -54 region, ER? and Sp1 plasmids E2 induced transactivation in cells cotransfected with AhR/Arnt expression plasmids suggesting that the AhR complex suppressed ER?/Sp1 action. These results demonstrate that TCDD inhibits E2-dependent activation of both non-genomic and genomic pathways of ER-mediated E2F-1 gene expression.Item Regulation of Mammary cell Differentiation and Metabolism by Singleminded-2s(2013-05-21) Scribner, Kelly CDuctal carcinoma in situ (DCIS) has been shown to be a precursor to invasive ductal cancer (IDC). Though the progression of DCIS to IDC is believed to be an important aspect of tumor aggressiveness, prognosis and molecular markers that predict progression are poorly understood. Therefore, determining the mechanisms by which some DCIS progress is critical for future breast cancer diagnostics and treatment. Singleminded-2s (SIM2s) is a member of the bHLH/PAS family of transcription factors and a key regulator of differentiation. SIM2s is highly expressed in mammary epithelial cells and lost in breast cancer. Loss of Sim2s causes aberrant mouse mammary development with features suggestive of malignant transformation, whereas over-expression of Sim2s promotes precocious alveolar differentiation, suggesting that Sim2s is required for establishing and enhancing mammary gland differentiation. We hypothesize that SIM2s expression must be lost in premalignant lesions for breast cancer to develop. We first analyzed Sim2s in the involuting mammary gland, which is a highly tumorpromoting environment. Sim2s is down-regulated during involution, and forced expression delays involution. We then analyzed SIM2s expression in human breast cancer samples and found that SIM2s is lost with progression from DCIS to IDC, and this loss correlates with metastasis. SIM2s expression in DCIS promoted a differentiated phenotype and suppressed genes associated with de-differentiation. Furthermore, loss of SIM2s expression in DCIS xenografts increased metastasis likely due to an increase in hedgehog signaling and matrix metalloproteinase expression. Interestingly, we found metabolic shifts with gain and loss of SIM2s in not only DCIS cells, but also MCF7 and SUM159 cells. SIM2s expression decreased aerobic glycolysis and promoted oxidative phosphorylation through direct upregulation of CDKN1a and senescence. Loss of SIM2s, conversely, promotes mitochondrial dysfunction and induction of the Warburg effect. This is the first time CDKN1a and cellular senescence have been indicated as causative to metabolic shifts within cancer cells. These studies show a new role for SIM2s in metabolic homeostasis, and this regulation is lost during tumorigenesis. These data indicate SIM2s is at the apex where aging, metabolism, and disease meet ? regulating the delicate relationship between the three.