Selective receptor modulators have been developed for steroid hormone receptors as a new class of mechanism-based drugs for treatment of hormone related diseases. We investigated an alternative mechanism-based strategy for treating various cancers with selective aryl hydrocarbon receptor modulators (SAhRMs), such as diindolylmetane/(DIM), 2,3,7,8-tetrachlorodibenzo-pdioxin/( TCDD), and 6-6-methyl-1,3,8-trichlorodibenzofuran/(MCDF) that exhibit antiproliferative activity in several cancer cell lines. MDA-MB-453 and BT-474 are estrogen receptor/(ER) negative breast cancer cell lines that express a functional aryl hydrocarbon receptor/(AhR) and treatment with SAhRMs significantly inhibited MDA-MB-453/BT-474 cell proliferation but did not significantly affect the percent distribution of cells in G0/G1/S/G2/M phases of cell cycle. TCDD and the SAhRMs had minimal effects on the expression of various cellular kinases. These data coupled with results obtained for other activated kinase pathways demonstrate that TCDD and SAhRMs uniquely inhibit growth of ER-negative MDA-MB 453/BT-474 breast cancer cells through kinase independent pathways. However, the SAhRMs induced HES-1, an antiproliferative transcription factor, in both cell lines and this might represent a possible mechanism for the growth inhibitory effects observed with these compounds. We proved that ring substituted DIMs exhibit androgenic/antiandrogenic activities in androgen receptor/(AR)-positive LNCaP/22RV1 prostate cancer cell lines resulting in antiproliferative activities. These antiproliferative activities were accompanied by antiandrogenic activity and structure-dependent down regulation of AR. The ring-substituted DIMs also induced both non-steroidal anti-inflamatory drug-induced gene-1/(NAG-1) and activating transcription factor 3/(ATF-3), two anti-proliferative/apoptotic genes which are responsible in part for the inhibitory effects of these compounds on the proliferation of prostate cancer cells.

Insulin-like growth factor-I (IGF-I) is a mitogenic polypeptide that induces proliferation and activation of kinase pathways in MCF-7 breast cancer cells. The role of estrogen receptor α (ERα) in mediating responses induced by IGF-I was investigated in cells transfected with small inhibitory RNA for ERα (iERα) or cotreated with the pure antiestrogen ICI 182780. The results showed that IGF-I-dependent phosphorylation of Akt and MAPK, induction of G1–S-phase progression and enhanced expression of cyclin D1 and cyclin E were dependent on ERα. Moreover, these IGF-I-induced responses were also inhibited by the antiestrogen ICI 182780, suggesting that the effects of ICI 182780 as an inhibitor of IGF-I induced responses in breast cancer cells are primarily related to downregulation of ERα. Chemoprotective phytochemicals exhibit multiple activities and interact with several cellular receptors, including the aryl hydrocarbon receptor (AhR). We investigated the AhR agonist/antagonist activities of the following flavonoids: chrysin, phloretin, kaempferol, galangin, naringenin, genistein, quercetin, myricetin, luteolin, baicalein, daidzein, apigenin, and diosmin, in MCF-7 breast cancer cells, HepG2 human liver cells and mouse Hepa-1 cells. The dietary phytochemicals exhibited substantial cell context–dependent AhR agonist as well as antagonist activities, and these are factors that must be considered in risk assessment of overall exposures to AhR agonists. Halogenated aromatic hydrocarbons (HAHs) such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), 1,2,3,7,8- pentachlorodibenzo-p-dioxin (PeCDD), 3,3’,4,4’,5-pentachlorobiphenyl (PCBP), 2,3,7,8- tetrachlorodibenzofuran (TCDF) and 2,3,4,7,8-pentachlorodibenzofuran (PeCDF) bind and activate the aryl hydrocarbon receptor (AhR). It has been assumed that these compounds only differ in their potencies. The SAhRM-like activity of the 5 HAHs was investigated by determining ligand structure dependent differences in their induction of CYP1A1 and interactions of the AhR with a series of coactivators in a mammalian two-hybrid assay in three AhR-responsive cell lines, including mouse Hepa-1, Human HEK293 and human Panc1 cells. There were multiple structure-dependent differences in activation of luciferase activity in these cell lines transfected with VP-AhR and six different GAL4-coactivator chimeras and a GAL4-response element-luciferase promoter construct. The results show that HAHs selectively interact with coactivators and these interactions are dependent on cell-context, and even among HAHs, these compounds exhibit selective receptor modulator activity.

17β-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 α (ERα)/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 ERα-positive ZR-75 cells; however, further analysis of the promoter showed that cooperative ERα/Sp1/NFY interactions were not necessary for hormone-induced transactivation in ZR-75 cells. The upstream GC-rich motifs are activated independently by ERα/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 ERα-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-ERα 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 ERα 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, ERα and Sp1 plasmids E2 induced transactivation in cells cotransfected with AhR/Arnt expression plasmids suggesting that the AhR complex suppressed ERα/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. 17β-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 α (ERα)/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 ERα-positive ZR-75 cells; however, further analysis of the promoter showed that cooperative ERα/Sp1/NFY interactions were not necessary for hormone-induced transactivation in ZR-75 cells. The upstream GC-rich motifs are activated independently by ERα/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 ERα-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-ERα 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 ERα 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, ERα and Sp1 plasmids E2 induced transactivation in cells cotransfected with AhR/Arnt expression plasmids suggesting that the AhR complex suppressed ERα/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.

Breast 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.

The 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.

Breast cancer is the fifth most common cause of cancer death in the worldwide. In the past decades, tamoxifen has been used for clinical treatment for breast cancers. The derivatives of compound thiazolidinedione (TZDs) including troglitazone (rezulin) and rosiglitazone (avandia) are also in the stages of clinical trials. But in the earlier research, some studies reported that the use of these drugs was associated with some serious side effects. Cyclin D1 plays an important role in G1/S phase cell cycle progression and in growth factor- or estrogen-induced mammary epithelial cell proliferation. Cyclin D1 overexpression is also found in high percentage (over 30%) of human breast cancers, correlating with poor prognosis. In this study, we used a cyclin D1-ablative drug VGH No.47 to reduce the expression of cyclin D1 in human breast adenocarcinoma cell line MCF-7 (ER-positive) and MDA-MB-231 (ER-negative) and to study its effect on cell proliferation. Our results demonstrated that VGH No.47 decreased the protein stability of cyclin D1. Conversely, VGH No.47 reduced cyclin D1 at both transcriptional level and protein stability in ER-negative MDA-MB-231 cells. We found that VGH No.47 caused G2/M arrested in both breast cancer cell lines. In addition, we tested whether cyclin D1-ablative drug could sensitize breast cancer cells to tamoxifen and TZDs. We expect to lower the dose of tamoxifen, troglitazone or rosiglitazone to reduce the side effects, but the results do not meet our expectation and do not exhibit synergistic effect.

Thesis (M. Med. Sc.)--University of Hong Kong, 2001. / Includes bibliographical references (leaves 61-66).

Thesis (Ph. D.)--Rutgers University, 2009. / "Graduate Program in Planning and Public Policy." Includes bibliographical references (p. 170-184).

Thesis (Ph. D.)--University of Washington, 2004. / Vita. Includes bibliographical references (leaves 35-43).

Thesis (M. Phil.)--University of Hong Kong, 2010. / Includes bibliographical references (p. 85-93). Also available in print.