RESUMO
Approximately one-third of estrogen receptor (ER) positive breast tumors fail to respond to or become resistant to hormonal therapy. Although the mechanisms responsible for hormone resistance are not completely understood, resistance is associated with alterations in ERα; overexpression of proteins that interact with the receptor; and hormone-independent activation of the receptor by growth factor signal transduction pathways. Our previous studies show that in estrogen dependent breast cancer cells, activation of the epidermal growth factor signaling pathway increases intracellular calcium which binds to and activates ERα through sites in the ligand-binding domain of the receptor and that treatment with extracellular calcium increases the concentration of intracellular calcium which activates ERα and induces hormone-independent cell growth. The present study asked whether overexpression of calcium channels contributes to the hormone-independent and -resistant phenotype of breast cancer cells and whether clinically used calcium channel blockers reverse hormone independence and resistance. The results show that hormone-independent and -resistant cells overexpress calcium channels, have high concentrations of intracellular calcium, overexpress estrogen responsive genes and, as expected, grow in the absence of estradiol and that treatment with calcium channel blockers decreased the concentration of intracellular calcium, the expression of estrogen responsive genes and cell growth. More importantly, in hormone-resistant cells, treatment that combined a calcium channel blocker with an antiestrogen reversed resistance to the antiestrogen.
Assuntos
Neoplasias da Mama/genética , Cálcio/metabolismo , Resistencia a Medicamentos Antineoplásicos/genética , Estradiol/farmacologia , Regulação Neoplásica da Expressão Gênica/genética , Neoplasias da Mama/metabolismo , Neoplasias da Mama/patologia , Bloqueadores dos Canais de Cálcio/farmacologia , Canais de Cálcio/genética , Canais de Cálcio/metabolismo , Proliferação de Células/efeitos dos fármacos , Proliferação de Células/genética , Resistencia a Medicamentos Antineoplásicos/efeitos dos fármacos , Moduladores de Receptor Estrogênico/farmacologia , Receptor alfa de Estrogênio/genética , Receptor alfa de Estrogênio/metabolismo , Estrogênios/farmacologia , Feminino , Regulação Neoplásica da Expressão Gênica/efeitos dos fármacos , Humanos , Células MCF-7 , Receptores de Progesterona/genética , Receptores de Progesterona/metabolismoRESUMO
Previous studies demonstrate that the heavy metal cadmium and the metalloid arsenite activate estrogen receptor-alpha in breast cancer cells by forming a high-affinity complex with the ligand-binding domain of the receptor and that environmentally relevant doses of cadmium have estrogen-like activity in vivo. The present study showed that in estrogen-receptor positive cells, arsenite and cadmium increased the global expression of estrogen-responsive genes and that an environmentally relevant dose of arsenite also had estrogen-like activity in vivo. Similar to estrogens, exposure of ovariectomized animals to arsenite induced the expression of the progesterone receptor, GREB1, and c-fos in the mammary gland and the expression of complement C3, c-fos, and cyclin D1 in the uterus and the increase was blocked by the antiestrogen ICI-182,780. When virgin female animals were fed a diet, that mimics exposure to either arsenite or cadmium, and challenged with the chemical carcinogen dimethylbenzanthracene, there was an increase in the incidence of mammary tumors and a decrease in the time to tumor onset, but no difference in the total number of tumors, tumor multiplicity, or total tumor volume. Together with published results, these data showed that environmentally relevant amounts of arsenite and cadmium had estrogen-like activity in vivo and promoted mammary tumorigenesis.
Assuntos
Arsenitos/toxicidade , Cádmio/toxicidade , Estrogênios/genética , Neoplasias Mamárias Animais/genética , Animais , Benzo(a)Antracenos/toxicidade , Carcinógenos/toxicidade , Ciclina D1/genética , Receptor alfa de Estrogênio/genética , Estrogênios/metabolismo , Feminino , Humanos , Células MCF-7 , Glândulas Mamárias Humanas/efeitos dos fármacos , Glândulas Mamárias Humanas/patologia , Neoplasias Mamárias Animais/induzido quimicamente , Neoplasias Mamárias Animais/patologia , Proteínas de Neoplasias/genética , Proteínas Proto-Oncogênicas c-fos/genética , Ratos , Receptores de Progesterona/genéticaRESUMO
BACKGROUND: The long time from exposure to potentially harmful chemicals until breast cancer occurrence poses challenges for designing etiologic studies and for implementing successful prevention programs. Growing evidence from animal and human studies indicates that distinct time periods of heightened susceptibility to endocrine disruptors exist throughout the life course. The influence of environmental chemicals on breast cancer risk may be greater during several windows of susceptibility (WOS) in a woman's life, including prenatal development, puberty, pregnancy, and the menopausal transition. These time windows are considered as specific periods of susceptibility for breast cancer because significant structural and functional changes occur in the mammary gland, as well as alterations in the mammary micro-environment and hormone signaling that may influence risk. Breast cancer research focused on these breast cancer WOS will accelerate understanding of disease etiology and prevention. MAIN TEXT: Despite the plausible heightened mechanistic influences of environmental chemicals on breast cancer risk during time periods of change in the mammary gland's structure and function, most human studies of environmental chemicals are not focused on specific WOS. This article reviews studies conducted over the past few decades that have specifically addressed the effect of environmental chemicals and metals on breast cancer risk during at least one of these WOS. In addition to summarizing the broader evidence-base specific to WOS, we include discussion of the NIH-funded Breast Cancer and the Environment Research Program (BCERP) which included population-based and basic science research focused on specific WOS to evaluate associations between breast cancer risk and particular classes of endocrine-disrupting chemicals-including polycyclic aromatic hydrocarbons, perfluorinated compounds, polybrominated diphenyl ethers, and phenols-and metals. We outline ways in which ongoing transdisciplinary BCERP projects incorporate animal research and human epidemiologic studies in close partnership with community organizations and communication scientists to identify research priorities and effectively translate evidence-based findings to the public and policy makers. CONCLUSIONS: An integrative model of breast cancer research is needed to determine the impact and mechanisms of action of endocrine disruptors at different WOS. By focusing on environmental chemical exposure during specific WOS, scientists and their community partners may identify when prevention efforts are likely to be most effective.
Assuntos
Neoplasias da Mama/epidemiologia , Neoplasias da Mama/etiologia , Exposição Ambiental/efeitos adversos , Animais , Neoplasias da Mama/prevenção & controle , Suscetibilidade a Doenças , Feminino , Humanos , Exposição Materna/efeitos adversos , Menopausa , Gravidez , Puberdade , Pesquisa , Fatores de Risco , Fatores de TempoRESUMO
Environmental exposure to estrogens and estrogen like contaminants during early development is thought to contribute to the risk of developing breast cancer primarily due to an early onset of puberty; however, exposure during key developing windows may also influence the risk of developing the disease. The goal of this study was to ask whether in utero exposure to the metalloestrogen cadmium alters mammary gland development due to acceleration of puberty onset or to an effect on early development of the mammary gland. The results show that, in addition to advancing the onset of puberty, in utero exposure to the metalloestrogen cadmium altered mammary gland development prior to its effect on puberty onset. In utero exposure resulted in an expansion of the number of mammosphere-forming cells in the neonatal mammary gland and an increase in branching, epithelial cells, and density in the prepubertal mammary gland. In the postpubertal mammary gland, there was a further expansion of the mammary stem/progenitor cell population and overexpression of estrogen receptor-alpha (ERα) that was due to the overexpression and altered regulation of the ERα transcripts derived from exons O and OT in response to estradiol. These results suggest that in utero exposure to cadmium increases stem/progenitor cells, cell density, and expression of estrogen receptor-alpha that may contribute to the risk of developing breast cancer.
Assuntos
Cádmio/toxicidade , Receptor alfa de Estrogênio/genética , Glândulas Mamárias Humanas/crescimento & desenvolvimento , Exposição Materna/efeitos adversos , Efeitos Tardios da Exposição Pré-Natal/patologia , Animais , Células Cultivadas , Células Epiteliais/citologia , Células Epiteliais/metabolismo , Receptor alfa de Estrogênio/metabolismo , Feminino , Humanos , Glândulas Mamárias Humanas/metabolismo , Glândulas Mamárias Humanas/patologia , Gravidez , Efeitos Tardios da Exposição Pré-Natal/genética , Efeitos Tardios da Exposição Pré-Natal/metabolismo , Ratos , Ratos Sprague-Dawley , Células-Tronco/citologia , Células-Tronco/metabolismoRESUMO
Metalloestrogens are metals that activate the estrogen receptor in the absence of estradiol. The metalloestrogens fall into two subclasses: metal/metalloid anions and bivalent cationic metals. The metal/metalloid anions include compounds such as arsenite, nitrite, selenite, and vanadate while the bivalent cations include metals such as cadmium, calcium, cobalt, copper, nickel, chromium, lead, mercury, and tin. The best studied metalloestrogen is cadmium. It is a heavy metal and a prevalent environmental contaminant with no known physiological function. This review addresses our current understanding of the mechanism by which cadmium and the bivalent cationic metals activate estrogen receptor-α. The review also summarizes the in vitro and in vivo evidence that cadmium functions as an estrogen and the potential role of cadmium in breast cancer.
Assuntos
Neoplasias da Mama/induzido quimicamente , Carcinógenos/toxicidade , Estrogênios/toxicidade , Glândulas Mamárias Humanas/efeitos dos fármacos , Metaloides/toxicidade , Metais/toxicidade , Animais , Neoplasias da Mama/metabolismo , Cádmio/toxicidade , Carcinógenos Ambientais/toxicidade , Exposição Ambiental/efeitos adversos , Receptor alfa de Estrogênio/agonistas , Receptor alfa de Estrogênio/química , Receptor alfa de Estrogênio/metabolismo , Feminino , Humanos , Glândulas Mamárias Animais/efeitos dos fármacos , Glândulas Mamárias Animais/metabolismo , Glândulas Mamárias Humanas/metabolismo , Transdução de Sinais/efeitos dos fármacosRESUMO
BACKGROUND: Since heavy metal cadmium is an endocrine disrupting chemical, we investigated whether maternal exposure to cadmium during the pregnancy alters mammary tumorigenesis among female offspring. METHODS: From gestation day 10 to day 19, pregnant rat dams were fed modified American Institute of Nutrition (AIN93G) diet containing 39% energy from fat (baseline diet), or the baseline diet containing moderate (75 µg/kg of feed) or high (150 µg/kg) cadmium levels. Some dams were injected with 10 µg 17ß-estradiol (E2) daily between gestation days 10 and 19. RESULTS: Rats exposed to a moderate cadmium dose in utero were heavier and exhibited accelerated puberty onset. Both moderate and high cadmium dose led to increased circulating testosterone levels and reduced the expression of androgen receptor in the mammary gland. The moderate cadmium dose mimicked the effects of in utero E2 exposure on mammary gland morphology and increased both the number of terminal end buds and pre-malignant hyperplastic alveolar nodules (HANs), but in contrast to the E2, it did not increase 7, 12-dimethylbenz (a) anthracene-induced mammary tumorigenesis. CONCLUSIONS: The effects of in utero cadmium exposure were dependent on the dose given to pregnant dams: Moderate, but not high, cadmium dose mimicked some of the effects seen in the in utero E2 exposed rats, such as increased HANs in the mammary gland.
RESUMO
The estrogen receptor alpha (ERα) is a steroid receptor that is pivotal in the initiation and progression of most breast cancers. ERα regulates gene transcription through recruitment of essential coregulators, including the steroid receptor coactivator AIB1 (Amplified in Breast Cancer 1). AIB1 itself is an oncogene that is overexpressed in a subset of breast cancers and is known to play a role in tumor progression and resistance to endocrine therapy through multiple mechanisms. Here we review the normal and pathological functions of AIB1 in regard to its ERα-dependent and ERα-independent actions, as well as its genomic conservation and protein evolution. We also outline the efforts to target AIB1 in the treatment of breast cancer.
Assuntos
Receptor alfa de Estrogênio , Neoplasias , Humanos , Receptor alfa de Estrogênio/genética , Oncogenes , Cognição , Genômica , Coativador 3 de Receptor Nuclear/genéticaRESUMO
Background: Although prostate cancer patients initially respond to androgen deprivation therapy, most patients progress to a resistant phenotype. Castration resistance is due, in part, to intratumoral and/or adrenal synthesis of androgens, overexpression or mutation of the androgen receptor (AR), stabilization of AR by chaperones, and ligand-independent activation of AR. Increasing evidence also links disruption of calcium homeostasis to progression of prostate cancer. Our previous study shows that heavy metal cadmium activates the AR through a ligand-independent mechanism. Cadmium mimics calcium in biological systems due to their similar ionic charge and radius. This study determines whether calcium activates AR and whether first- and second-generation antiandrogens block the ability of calcium to activate the receptor. Methods: The expression of androgen-responsive genes and calcium channels was measured in prostate cells using a quantitative real-time polymerase chain reaction assay. Cell growth was measured. Results: To ask whether calcium activates AR, prostate cells were treated with calcium in the absence and presence of the first-generation antiandrogens hydroxyflutamide and bicalutamide and the second-generation antiandrogen enzalutamide, and the expression of androgen-responsive genes and cell growth was measured. In the normal PWR-1E cells and HEK293T cells transiently expressing AR, treatment with calcium increased the expression of androgen-responsive genes by approximately 3-fold. The increase was blocked by enzalutamide but was not consistently blocked by the first-generation antiandrogens. In LNCaP cells which contain a mutant AR, treatment with calcium also increased the expression of androgen-responsive genes by approximately 3-fold, and the increase was more effectively blocked by enzalutamide than by hydroxyflutamide or bicalutamide. Treatment with calcium also increased cell growth that was blocked by enzalutamide. To ask whether dysregulation of calcium channels is associated with castration resistance, calcium channels were measured in the normal PWR-1E prostate cells, the hormone-responsive LNCaP cells, and the castration-resistant VCaP and 22RV1 cells. Compared to normal prostate cells, the hormone-responsive and hormone-resistant cells overexpressed several calcium channels. Conclusions: The results of this study show that calcium activates AR and increases cell growth and that calcium channels are overexpressed in hormone-responsive and hormone-resistant prostate cancer cells. Taken together, the results suggest a novel role of calcium in the castration-resistant phenotype.
RESUMO
It has been suggested that environmental contaminants that mimic the effects of estrogen contribute to disruption of the reproductive systems of animals in the wild, and to the high incidence of hormone-related cancers and diseases in Western populations. Previous studies have shown that functionally, cadmium acts like steroidal estrogens in breast cancer cells as a result of its ability to form a high-affinity complex with the hormone binding domain of the estrogen receptor. The results of the present study show that cadmium also has potent estrogen-like activity in vivo. Exposure to cadmium increased uterine wet weight, promoted growth and development of the mammary glands and induced hormone-regulated genes in ovariectomized animals. In the uterus, the increase in wet weight was accompanied by proliferation of the endometrium and induction of progesterone receptor (PgR) and complement component C3. In the mammary gland, cadmium promoted an increase in the formation of side branches and alveolar buds and the induction of casein, whey acidic protein, PgR and C3. In utero exposure to the metal also mimicked the effects of estrogens. Female offspring experienced an earlier onset of puberty and an increase in the epithelial area and the number of terminal end buds in the mammary gland.
Assuntos
Cádmio/farmacologia , Congêneres do Estradiol/metabolismo , Estradiol/análogos & derivados , Estradiol/farmacologia , Glândulas Mamárias Animais/efeitos dos fármacos , Útero/efeitos dos fármacos , Animais , Cádmio/administração & dosagem , Cádmio/metabolismo , Caseínas/genética , Caseínas/metabolismo , Complemento C3/genética , Complemento C3/metabolismo , Estradiol/metabolismo , Antagonistas de Estrogênios/farmacologia , Feminino , Fulvestranto , Regulação da Expressão Gênica/efeitos dos fármacos , Humanos , Glândulas Mamárias Animais/citologia , Glândulas Mamárias Animais/crescimento & desenvolvimento , Glândulas Mamárias Animais/metabolismo , Proteínas do Leite/genética , Proteínas do Leite/metabolismo , Mimetismo Molecular , Tamanho do Órgão/efeitos dos fármacos , Ovariectomia , Gravidez , Ratos , Ratos Sprague-Dawley , Receptores de Estrogênio/metabolismo , Receptores de Progesterona/genética , Receptores de Progesterona/metabolismo , Maturidade Sexual/efeitos dos fármacos , Útero/citologia , Útero/metabolismoRESUMO
Background: The U.S. Preventive Services Task Force (USPSTF) modified breast cancer screening guidelines in November 2009. The impact has been studied among privately and Medicare insured populations, but not among universally insured women. Materials and Methods: This study compared the proportion of TRICARE beneficiaries aged 40-64 receiving mammograms from fiscal years 2006 to 2015 using an interrupted time series analysis to determine the impact of the 2009 USPSTF guideline changes. Stratified analyses evaluated differences by age (ages 40-49, 50-64), race, care setting, beneficiary type, and military status. Results: The proportion of women receiving mammograms increased from October 2005 through September 2009. A small, but significant decrease of 65-66 fewer women screened per 10,000 occurred in the first quarter of 2010 (October 1 to December 31) following the screening guideline update publication. The proportion screened then remained unchanged through 2015. Comparative analysis revealed no differences in impact between age groups, blacks and whites, or military dependents and active-duty/retirees. Conclusions: This study determined that the USPSTF guideline updates had a small, but immediate and lasting impact that was not different across age groups, beneficiary type, or race. No racial disparities in the proportion screened or in the impact of the guideline change were noted in our universally insured population.
Assuntos
Neoplasias da Mama , Medicare , Adulto , Idoso , Neoplasias da Mama/diagnóstico por imagem , Detecção Precoce de Câncer , Feminino , Humanos , Mamografia , Programas de Rastreamento , Estados UnidosRESUMO
INTRODUCTION: The U.S. Preventive Services Task Force (USPSTF) modified their screening guidelines for breast cancer in November 2009. Previous studies evaluated the impact of these guideline changes among privately and Medicare insured populations. Women in the military form a unique population exposed to many social, environmental, and occupational hazards that may increase breast cancer incidence. By evaluating mammography screening rates among women in the military before and after the USPSTF guideline changes, this study evaluated the impact of the USPSTF breast cancer guideline change on screening mammography use within the military population and determined whether current guidelines were followed for this high-risk population with universal health care access. MATERIALS AND METHODS: This study evaluated the impact of the 2009 guideline changes among the population of universally insured military servicewomen, comparing the proportion of active duty women aged 40 to 64 receiving mammograms from fiscal years 2006 to 2015 using an interrupted time series analysis. Stratified analyses evaluated differences by age (aged 40-49, 50-64), race, military branch, and rank. This research is considered exempt by the Uniformed Services University Institutional Review Board. RESULTS: The proportion of insured military servicewomen receiving mammograms increased from October 2005 through September 2009. A significant decrease occurred in the first quarter of 2010 following the publication of the screening guideline update. From this new baseline, the proportion of women screened increased again through September 2015. Comparative analyses showed more pronounced effects both immediately and over time among the women aged 50 to 64 compared to those aged 40 to 49 years and among older enlisted women compared with their officer counterparts. The patterns were near identical in all subgroups; however, no changes in rate were evident among Air Force and black servicewomen aged 50 to 64 and Army and Navy/Marine Corps servicewomen aged 40 to 49 years. No racial disparities in screening or impact were noted. CONCLUSIONS: The USPSTF guidelines had differential impacts among some subpopulations. While older women, aged 50 to 64 years, had a greater temporary reduction immediately after the guideline change, younger women aged 40 to 49 years had a longer-term reduction in screening following the guideline changes. No racial disparities in the proportion screened or in the impact of the guideline change were noted in this population with universal health coverage. The lack of Department of Defense standard breast cancer screening guidelines was evident from the different patterns of mammography utilization observed among military branches. To completely understand the impact of the updated screening guidelines, future studies must incorporate research focusing on changes in breast cancer morbidity and mortality as well as updated cost-benefit analyses.
Assuntos
Neoplasias da Mama , Militares , Adulto , Neoplasias da Mama/diagnóstico , Detecção Precoce de Câncer , Feminino , Humanos , Mamografia , Programas de Rastreamento , Medicare , Pessoa de Meia-Idade , Estados UnidosRESUMO
Cadmium is a heavy metal that is often referred to as the metal of the 20th century. It is widely used in industry principally in galvanizing and electroplating, in batteries, in electrical conductors, in the manufacture of alloys, pigments, and plastics, and in the stabilization of phosphate fertilizers. As a byproduct of smelters, cadmium is a prevalent environmental contaminant. In the general population, exposure to cadmium occurs primarily through dietary sources, cigarette smoking, and, to a lesser degree, drinking water. Although the metal has no known physiological function, there is evidence to suggest that the cadmium is a potent metallohormone. This review summarizes the increasing evidence that cadmium mimics the function of steroid hormones, addresses our current understanding of the mechanism by which cadmium functions as a hormone, and discusses its potential role in development of the hormone dependent cancers.
Assuntos
Androgênios/toxicidade , Cádmio/toxicidade , Disruptores Endócrinos/toxicidade , Poluentes Ambientais/toxicidade , Estrogênios/toxicidade , Androgênios/metabolismo , Animais , Sítios de Ligação , Cádmio/metabolismo , Disruptores Endócrinos/metabolismo , Poluentes Ambientais/metabolismo , Estrogênios/metabolismo , Humanos , Neoplasias Hormônio-Dependentes/induzido quimicamente , Conformação Proteica , Receptores Androgênicos/efeitos dos fármacos , Receptores Androgênicos/metabolismo , Receptores de Estrogênio/química , Receptores de Estrogênio/efeitos dos fármacos , Receptores de Estrogênio/metabolismo , Medição de Risco , Transdução de Sinais/efeitos dos fármacos , Relação Estrutura-AtividadeAssuntos
Neoplasias da Mama/epidemiologia , Saúde da Mulher , Neoplasias da Mama/induzido quimicamente , Neoplasias da Mama/etiologia , Neoplasias da Mama/prevenção & controle , Suscetibilidade a Doenças , Feminino , Humanos , Glândulas Mamárias Humanas/efeitos dos fármacos , Glândulas Mamárias Humanas/crescimento & desenvolvimento , Glândulas Mamárias Humanas/patologia , Gravidez , Fatores de RiscoRESUMO
BACKGROUND: There is little information about oncotherapy-related dental development in childhood acute lymphoblastic leukaemia (ALL). OBJECTIVE: The objective of this study was to compare bone age (BA) and dental age (DA) to chronological age (CA) in childhood ALL survivors. METHODS: We retrospectively reviewed hand-wrist and panoramic radiographs of patients treated on contemporary single institution protocols for ALL between 1991 and 2004. We recorded patient demographics, therapeutic protocol, CA, DA, and BA. The cohort was divided into three categories based on age at diagnosis (< 6 years, 6-9 years, > 9 years). RESULTS: Of 73 patients, 39 (53.4%) were boys; 55 (75.3%) were Caucasian. Median CA at diagnosis was 4.5 years (range: 0.1-11.0 years); time to study was 4.1 years (range: 0.3-11.4 years). BA was normal in 61 (83.6%), delayed in 10 (13.7%), and advanced in 2 (2.7%). DA was normal in 41 (56.9%), delayed in 8 (11.1%), and advanced in 23 (31.9%). Abnormal BA, abnormal DA, and discrepancy between BA and DA are not statistically significantly associated with investigated patient or treatment factors. CONCLUSIONS: DA may be altered in 43.1% of patients treated for ALL. A large prospective study is warranted to better define our observations and to determine their impact on dental and orthodontic management.
Assuntos
Determinação da Idade pelo Esqueleto , Determinação da Idade pelos Dentes , Desenvolvimento Infantil , Leucemia-Linfoma Linfoblástico de Células Precursoras/fisiopatologia , Sobreviventes/estatística & dados numéricos , Adolescente , Antineoplásicos/uso terapêutico , Criança , Pré-Escolar , Estudos de Coortes , Assistência Odontológica para Crianças , Assistência Odontológica para Doentes Crônicos , Feminino , Humanos , Lactente , Masculino , Leucemia-Linfoma Linfoblástico de Células Precursoras/terapia , Radioterapia , Estudos RetrospectivosRESUMO
Metallo-estrogens are a new class of potent environmental estrogens. This study investigates whether tobacco smoke condensate (TSC), which contains metals and metalloids, elicits estrogen-like effects at environmentally relevant doses. Treatment of human breast cancer cells, MCF-7, with 40 microg/ml TSC resulted in a 2.5-fold stimulation of cell growth. TSC decreased the concentration of estrogen receptor (ER)-alpha protein and mRNA (63 and 62%, respectively), and increased the expression of the estrogen-regulated genes, progesterone receptor and pS2 (5- and 2-fold, respectively). In addition, TSC activated ER-alpha in COS-1 or CHO cells transiently transfected with wild-type ER-alpha and an ERE-CAT or an ERE-luciferase reporter gene (11- and 6-fold, respectively). TSC also activated a chimeric receptor (GAL-ER) containing the hormone binding domain of ER-alpha (3.5-fold). It blocked the binding of estradiol to the receptor without altering the affinity of estradiol (K(d) = 2.2-6.8 x 10(-10) m). Transfection assays with ER-alpha mutants identified C381, C447, H524, N532, E523, and D538 in the hormone binding domain as important for activation by TSC. In ovariectomized rats, low doses of TSC [10 or 20 mg/kg body weight (bw)] increased uterine wet weight (1.7- and 2.1-fold), and induced the expression of progesterone receptor and complement C3 in the uterus (2- and 26-fold) and mammary gland (4.4- and 15-fold). Both the in vitro and in vivo TSC effects were blocked by the antiestrogen ICI 182,780, suggesting the involvement of ER. Collectively, these results provide strong evidence that low doses of TSC, acting through the hormone binding domain, exert estrogen-like effects in cell culture and animals.
Assuntos
Receptor alfa de Estrogênio/genética , Receptor alfa de Estrogênio/metabolismo , Expressão Gênica , Nicotiana , Fumaça , Animais , Neoplasias da Mama/metabolismo , Neoplasias da Mama/patologia , Células CHO , Células COS , Divisão Celular , Linhagem Celular Tumoral , Chlorocebus aethiops , Cricetinae , Cricetulus , Estradiol/metabolismo , Feminino , Homeostase , Humanos , Mutação/fisiologia , Concentração Osmolar , Ovariectomia , RNA Mensageiro/metabolismo , Ratos , Ratos Sprague-Dawley , TransfecçãoRESUMO
Epidermal growth factor (EGF), insulin-like growth factor-I (IGF-I), and heregulin-beta1 (HRG-beta1), can modulate the expression and activity of the estrogen receptor-alpha (ER-alpha) via the phosphatidylinositol 3-kinase (PI 3-K)/Akt pathway in the ER-alpha-positive breast cancer cell line, MCF-7. Estradiol can also rapidly activate PI 3-K/Akt in these cells (nongenomic effect). The recent study examines whether Akt is involved in the ER-alpha regulation by estradiol (genomic effect). Stable transfection of parental MCF-7 cells with a dominant-negative Akt mutant, as well as the PI 3-K inhibitors wortmannin and LY 294,002, blocked the effect of estradiol on ER-alpha expression and activity by 70-80 and 55-63%, respectively. Stable transfection of MCF-7 cells with a constitutively active Akt mimicked the effect of estradiol. The changes in ER-alpha expression and activity were abrogated in response to estradiol by an arginine to cysteine mutation in the pleckstrin homology (PH) domain of Akt (R25C), suggesting the involvement of this amino acid in the interaction between Akt and ER-alpha. Experiments employing selective ErbB inhibitors demonstrate that the effect of estradiol on ER-alpha expression and activity is mediated by ErbB2 and not by EGFR. Moreover, anchorage-dependent and -independent growth assays, cell cycle and membrane ruffling analyses showed that Akt exerts estrogen-like activity on cell growth and membrane ruffling and that a selective ErbB2 inhibitor, but not anti-ErbB2 antibodies directed to the extracellular domain, can block these effects. In the presence of constitutively active Akt, tamoxifen only partially inhibits cell growth. In contrast, in cells stably transfected with either a dominant-negative Akt or with R25C-Akt, as well as in parental cells in the presence of a selective ErbB2 inhibitor, the effect of estradiol on anchorage-dependent and -independent cell growth was inhibited by 50-75 and 100%, respectively. Dominant-negative Akt inhibited membrane ruffling by 54%; however, R25C-Akt did not have any effect, suggesting that kinase activity plays an important role in this process. Scatchard analysis demonstrated a 67% reduction in estrogen-binding capacity in cells transfected with constitutively active Akt. No change in binding affinity of estradiol to the receptor was observed upon transfection with either Akt mutant. Taken together, our results suggest that estradiol treatment results in binding to membrane ER-alpha and interaction with a heterodimer containing ErbB2, leading to tyrosine phosphorylation. This results in the activation of PI 3-K and Akt. Akt, in turn, may interact with nuclear ER-alpha, altering its expression and activity.
Assuntos
Estradiol/farmacologia , Fosfatidilinositol 3-Quinases/metabolismo , Proteínas Serina-Treonina Quinases , Proteínas Proto-Oncogênicas/metabolismo , Receptor ErbB-2/metabolismo , Receptores de Estrogênio/genética , Androstadienos/farmacologia , Anticorpos/farmacologia , Neoplasias da Mama/tratamento farmacológico , Neoplasias da Mama/genética , Neoplasias da Mama/metabolismo , Divisão Celular/efeitos dos fármacos , Divisão Celular/genética , Membrana Celular/efeitos dos fármacos , Membrana Celular/metabolismo , Cromonas/farmacologia , Resistencia a Medicamentos Antineoplásicos/genética , Inibidores Enzimáticos/farmacologia , Receptor alfa de Estrogênio , Feminino , Expressão Gênica/efeitos dos fármacos , Humanos , Morfolinas/farmacologia , Mutação , Fosfatidilinositol 3-Quinases/efeitos dos fármacos , Inibidores de Fosfoinositídeo-3 Quinase , Proteínas Proto-Oncogênicas/efeitos dos fármacos , Proteínas Proto-Oncogênicas/genética , Proteínas Proto-Oncogênicas c-akt , Receptor ErbB-2/antagonistas & inibidores , Receptor ErbB-2/efeitos dos fármacos , Receptor ErbB-2/imunologia , Receptores de Estrogênio/efeitos dos fármacos , Receptores de Estrogênio/metabolismo , Transdução de Sinais , Tamoxifeno/farmacologia , Células Tumorais Cultivadas , Ensaio Tumoral de Célula-Tronco , WortmaninaRESUMO
This study examines whether the serine/threonine protein kinase, Akt, is involved in the crosstalk between the ErbB2 and estrogen receptor-alpha (ER-alpha) pathways. Treatment of MCF-7 cells with 10(-9) M heregulin-beta1 (HRG-beta1) resulted in a rapid phosphorylation of Akt and a 15-fold increase in Akt activity. Akt phosphorylation was blocked by inhibitors of phosphatidylinositol 3-kinase (PI 3-K), by antiestrogens, the protein tyrosine kinase inhibitor, genistein, and by AG825, a selective ErbB2 inhibitor; but not by AG30, a selective EGFR inhibitor. Akt phosphorylation by HRG-beta1 was abrogated by an arginine to cysteine mutation (R25C) in the pleckstrin homology (PH) domain of Akt, and HRG-beta1 did not induce Akt phosphorylation in the ER-negative variant of MCF-7, MCF-7/ADR. Transient transfection of ER-alpha into these cells restored Akt phosphorylation by HRG-beta1, suggesting the requirement of ER-alpha. HRG-beta1 did not activate Akt in MCF-7 cells stably transfected with an anti-ErbB2-targeted ribozyme, further confirming a role for ErbB2. Stable transfection of the cells with a dominant negative Akt or with the R25C-Akt mutant, as well as PI 3-K inhibitors, blocked the effect of HRG-beta1 on ER-alpha expression and activity and on the growth of MCF-7 cells. Stable transfection of MCF-7 cells with a constitutively active Akt mimicked the effect of HRG-beta1. Experiments employing selective ErbB inhibitors demonstrate that the effect of HRG-beta1 on ER-alpha expression and activity is also mediated by ErbB2 and not by EGFR, demonstrating that ErbB2 is the primary mediator of the effects of HRG-beta1 on ER-alpha regulation. Taken together, our data suggest that HRG-beta1, bound to the ErbB2 ErbB3 heterodimer, in the presence of membrane ER-alpha, interacts with and activates PI 3-K/Akt. Akt leads to nuclear ER-alpha phosphorylation, thereby altering its expression and transcriptional activity.
Assuntos
Genes erbB-2 , Neuregulina-1/farmacologia , Proteínas Serina-Treonina Quinases , Proteínas Proto-Oncogênicas/metabolismo , Receptor alfa de Estrogênio , Regulação da Expressão Gênica , Humanos , Fosfatidilinositol 3-Quinases/metabolismo , Fosforilação , Proteínas Proto-Oncogênicas c-akt , Receptores de Estrogênio , Transfecção , Células Tumorais CultivadasRESUMO
Previously, we have demonstrated that the two mitogenic growth factors epidermal growth factor and IGF-I can activate Akt and estrogen receptor-alpha (ERalpha) in the hormone-dependent breast cancer cell line, MCF-7. In this report we now show that estradiol can also rapidly activate phosphatidylinositol 3-kinase (PI 3-K)/Akt and that this effect is mediated by the ErbB2 signaling pathway. Treatment of cells with estradiol resulted in phosphorylation of Akt and a 9-fold increase in Akt activity in 10 min. Akt activation was blocked by wortmannin and LY 294,002, two inhibitors of PI 3-K; by genistein, a protein tyrosine kinase inhibitor and an ER agonist; by AG825, a selective ErbB2 inhibitor; and by the antiestrogens ICI 182,780 and 4-hydroxy-tamoxifen; but not by rapamycin, an inhibitor of the ribosomal protein kinase p70S6K; nor by AG30, a selective epidermal growth factor receptor inhibitor. Akt activation by estradiol was abrogated by an arginine-to-cysteine mutation in the pleckstrin homology domain of Akt (R25C). Growth factors also activated Akt in the ER-negative variant of MCF-7, MCF-7/ADR, but estradiol did not induce Akt activity in these cells. Transient transfection of ERalpha into these cells restored Akt activation by estradiol, suggesting that estradiol activation of Akt requires the ERalpha. Estradiol did not activate Akt in MCF-7 cells stably transfected with an anti-ErbB2-targeted ribozyme, further confirming a role for ErbB2. In vitro kinase assays using immunoprecipitation and anti-Akt1, -Akt2, and -Akt3-specific antibodies demonstrated that Akt1 is activated by estradiol in MCF-7 cells whereas Akt3 is the activated isoform in ER-negative MDA-MB231 cells, implying that selective activation of Akt subtypes plays a role in the actions of estradiol. Taken together, our data suggest that estradiol, bound to membrane ERalpha, interacts with and activates an ErbB dimer containing ErbB2, inducing activation of PI 3-K/Akt.
Assuntos
Estradiol/análogos & derivados , Estradiol/metabolismo , Proteínas Serina-Treonina Quinases , Proteínas Proto-Oncogênicas/metabolismo , Receptor ErbB-2/metabolismo , Transdução de Sinais , Androstadienos/farmacologia , Neoplasias da Mama/metabolismo , Cromonas/farmacologia , Inibidores Enzimáticos/farmacologia , Estradiol/farmacologia , Moduladores de Receptor Estrogênico/farmacologia , Receptor alfa de Estrogênio , Feminino , Fulvestranto , Genisteína/farmacologia , Humanos , Morfolinas/farmacologia , Mutação , Fosfatidilinositol 3-Quinases/metabolismo , Inibidores de Fosfoinositídeo-3 Quinase , Fosforilação , Isoformas de Proteínas , Proteínas Proto-Oncogênicas/efeitos dos fármacos , Proteínas Proto-Oncogênicas/genética , Proteínas Proto-Oncogênicas c-akt , Receptor ErbB-2/efeitos dos fármacos , Receptor ErbB-2/genética , Receptores de Estrogênio/efeitos dos fármacos , Receptores de Estrogênio/genética , Receptores de Estrogênio/metabolismo , Serina/metabolismo , Sirolimo/farmacologia , Células Tumorais Cultivadas , Tirfostinas/farmacologia , WortmaninaRESUMO
Early life exposure to estrogens and estrogen like contaminants in the environment is thought to contribute to the early onset of puberty and consequently increases the risk of developing breast cancer in the exposed female. The results of this study show that in utero exposure to the metalloestrogen arsenite altered mammary gland development prior to its effect on puberty onset. In the prepubertal gland, in utero exposure resulted in an increase in the number of mammosphere-forming cells and an increase in branching, epithelial cells, and density. In the postpubertal gland, in utero exposure resulted in the overexpression of estrogen receptor-alpha (ERα) that was due to the increased and altered response of the ERα transcripts derived from exons O and OT to estradiol. These results suggest that, in addition to advancing puberty onset, in utero exposure to arsenite alters the pre- and postpubertal development of the mammary gland and possibly, the risk of developing breast cancer.
Assuntos
Arsenitos/toxicidade , Poluentes Ambientais/toxicidade , Glândulas Mamárias Animais/efeitos dos fármacos , Exposição Materna/efeitos adversos , Efeitos Tardios da Exposição Pré-Natal , Fatores Etários , Animais , Proliferação de Células/efeitos dos fármacos , Células Cultivadas , Células Epiteliais/efeitos dos fármacos , Células Epiteliais/metabolismo , Células Epiteliais/patologia , Receptor alfa de Estrogênio/efeitos dos fármacos , Receptor alfa de Estrogênio/genética , Receptor alfa de Estrogênio/metabolismo , Feminino , Regulação da Expressão Gênica no Desenvolvimento/efeitos dos fármacos , Idade Gestacional , Hiperplasia , Glândulas Mamárias Animais/crescimento & desenvolvimento , Glândulas Mamárias Animais/metabolismo , Glândulas Mamárias Animais/patologia , Gravidez , RNA Mensageiro/metabolismo , Ratos Sprague-Dawley , Transcrição Gênica/efeitos dos fármacos , Regulação para Cima , Vagina/efeitos dos fármacos , Vagina/crescimento & desenvolvimentoRESUMO
Treatment of human prostate cancer cells, LNCaP, with cadmium stimulated cell growth. There was a 2.4-fold increase in the population of cells in the S + G(2)M phase by d 4 and a 2.7-fold increase in cell number by d 8. The metal decreased the concentration of AR protein and mRNA (80 and 60%, respectively) and increased the expression of prostate-specific antigen and the homeobox gene, NKX 3.1 (6-fold) that was blocked by an antiandrogen. In addition, cadmium activated the AR in mouse L cells containing an MMTV-luciferase reporter gene (4-fold increase) and in COS-1 cells transfected with wild-type AR and an MMTV-CAT reporter gene (7-fold increase). Cadmium also activated a chimeric receptor (GAL-AR) containing the hormone-binding domain of AR. The metal bound to AR with an equilibrium dissociation constant of 1.19 x 10(-10) M. Cadmium blocked the binding of androgen to the receptor but did not alter its affinity (dissociation constant = 2.8 x 10(-10) M), suggesting that the metal is an inhibitor of hormone binding. In castrated animals, a single, low, environmentally relevant dose of cadmium (20 microg/kg body weight) increased the wet weight of the prostate (1.97- to 3-fold) and the seminal vesicle complex (approximately 1.5-fold) and increased the expression of the androgen-regulated gene, probasin (27-fold). The in vivo effects were also blocked by an antiandrogen.