Estrogen Resistance Research Articles

Analysis of transcription and estrogen insensitivity in the female mouse after targeted disruption of the estrogen receptor gene.

We employed homologous recombination in mouse embryonic stem cells to disrupt the estrogen receptor (ER) gene. Subsequently generated mice that are homozygous for the gene disruption, termed ERKO, possess no demonstrable wild-type ER by Western blot analysis. However, the presence of residual high affinity binding, as detected by [3H]estradiol binding assays and sucrose gradients in uterine extracts from ERKO females prompted further investigation of transcription and translation products from the disrupted ER gene. Analysis of ERKO uterine messenger RNA (mRNA) by reverse transcriptase-polymerase chain reaction demonstrated that although no full-length wild-type ER mRNA was present, two smaller transcripts, labeled E1 and E2, were identified and partially sequenced. Both ERKO transcripts are splicing variants that result in the disrupting NEO sequence being partially or completely removed from the mRNA. In the ERKO-E2 variant, this results in a frame shift and the creation of at least two stop codons downstream. In the ERKO-E1 variant, the ER reading frame is preserved and encodes for a smaller mutant ER that could be the source of the residual estradiol binding. When this mutant form is overexpressed and characterized in vitro, it results in a smaller protein of the predicted size that possesses significantly reduced estrogen-dependent transcriptional activity compared with that of the wild-type ER. Despite residual amounts of an impaired ER variant, estrogen insensitivity in the female ERKOs was confirmed by the failure of estrogen treatment to induce known uterine markers of estrogen action, such as increased DNA synthesis, and transcription of the progesterone receptor, lactoferrin, and glucose-6-phosphate dehydrogenase genes. Furthermore, serum levels of estradiol in the ERKO female are more than 10-fold higher than those in the wild type, consistent with a syndrome of hormone insensitivity.

Analysis of transcription and estrogen insensitivity in the female mouse after targeted disruption of the estrogen receptor gene

Analysis of transcription and estrogen insensitivity in the female mouse after targeted disruption of the estrogen receptor gene

The role of estrogen in pubertal skeletal physiology: epiphyseal maturation and mineralization of the skeleton.

The year 1994 is likely to be remembered by many endocrinologists as the year in which dramatic new light was shed on the role played by estrogen in human skeletal physiology. It was in 1994 that two new syndromes were described, each representing a human model in which estrogen action was lacking. The first case was a female with an aromatase defect and a resultant inability to synthesize estrogen, and the second case was a man with an estrogen receptor gene defect that resulted in a non-functioning estrogen receptor and complete estrogen resistance. By examining the phenotypes of these two individuals, we were able, for the first time, to see what pubertal skeletal changes occur in the absence of estrogen action and directly extrapolate the role of estrogen in skeletal physiology. What has become abundantly clear is that it is estrogen and not androgen that is responsible for pubertal epiphyseal maturation and skeletal mineralization.

Estrogen Resistance Caused by a Mutation in the Estrogen-Receptor Gene in a Man

Smith, Eric P.; Boyd, Jeff; Frank, Graeme R.; Takahashi, Hiroyuki; Cohen, Robert M.; Specker, Bonny; Williams, Timothy C.; Lubahn, Dennis B.; Korach, Kenneth S.Author Information

Estrogen Resistance Caused by a Mutation in the Estrogen-Receptor Gene in a Man

Estrogen Resistance Caused by a Mutation in the Estrogen-Receptor Gene in a Man

Estrogen Resistance Caused by a Mutation in the Estrogen-Receptor Gene in a Man

Mutations in the estrogen-receptor gene have been thought to be lethal. A 28-year-old man whose estrogen resistance was caused by a disruptive mutation in the estrogen-receptor gene underwent studies of pituitary-gonadal function and bone density and received transdermal estrogen for six months. Estrogen-receptor DNA, extracted from lymphocytes, was evaluated by analysis of single-strand-conformation polymorphisms and by direct sequencing. The patient was tall (204 cm [80.3 in.]) and had incomplete epiphyseal closure, with a history of continued linear growth into adulthood despite otherwise normal pubertal development. He was normally masculinized and had bilateral axillary acanthosis nigricans. Serum estradiol and estrone concentrations were elevated, and serum testosterone concentrations were normal. Serum follicle-stimulating hormone and luteinizing hormone concentrations were increased. Glucose tolerance was impaired, and hyperinsulinemia was present. The bone mineral density of the lumbar spine was 0.745 g per square centimeter, 3.1 SD below the mean for age-matched normal women; there was biochemical evidence of increased bone turnover. The patient had no detectable response to estrogen administration, despite a 10-fold increase in the serum free estradiol concentration. Conformation analysis of his estrogen-receptor gene revealed a variant banding pattern in exon 2. Direct sequencing of exon 2 revealed a cytosine-to-thymine transition at codon 157 of both alleles, resulting in a premature stop codon. The patient's parents were heterozygous carriers of this mutation, and pedigree analysis revealed consanguinity. Disruption of the estrogen receptor in humans need not be lethal. Estrogen is important for bone maturation and mineralization in men as well as women.

Biology of breast cancer and its clinical implications.

Several established prognostic factors are used routinely in the clinical management of breast cancer. These factors include extent of axillary lymph node involvement, tumor size, histologic differentiation, and estrogen and progesterone receptor status. Unfortunately, these factors are not perfect predictors of outcome for the individual patient. This review highlights recent advances in the field of breast cancer biology that may ultimately improve our ability to predict prognosis more accurately, select therapy more appropriately, and possibly identify women who are at high risk for breast cancer development. In particular, studies addressing mechanisms of estrogen and antiestrogen resistance, clinical utility of flow cytometry, roles of certain oncogenes and tumor suppressor genes in breast cancer growth, and biologic factors involved in invasion and metastases are reviewed.

Differential initiation of translation of a single estrogen receptor mRNA could explain some estradiol resistance cases.

Cell response to steroid stimulation is generally acknowledged to be mediated by an intracellular protein known as a receptor. Response intensity is related to the affinity of the receptor and to the number of sites occupied by its specific ligand. Although verified in the majority of experimental and clinical studies, certain phenomena of steroid hormone resistance would seem to challenge this assertion. Application of gene molecular biology to determine the action mechanisms of steroid hormones has partially explained cell resistance in terms of genetic modifications. The work presented here shows that in certain cases, estrogen resistance could be explained by regulation of translation of the single messenger RNA coding for the receptor.

Sex Steroid Modulation of Gonadotropins in Normal Men and in Androgen Insensitivity Syndrome*

Abstract The respective roles of androgens and estrogens in the modulation of LH and FSH secretion in men have not been clearly defined. In this study, we compared gonadotropins basally and after stimulation with gonadotropin-releasing hormone in four states characterized by different sensitivity to sex steroids: 1) in five normal men (intact sensitivity to both androgens and estrogens), 2) in two patients with complete androgen insensitivity syndrome (AIS; selective androgen insensitivity), 3) in normal men treated with clomiphene citrate (selective estrogen insensitivity), and 4) in AIS patients treated with clomiphene (combined androgen and estrogen insensitivity). Basal LH levels were increased in selective androgen and selective estrogen insensitivities; LH levels were elevated further in combined androgen and estrogen insensitivities. The elevated LH levels in AIS were suppressible by exogenous administration of estradiol benzoate. Basal FSH was not increased in selective androgen insensitivity, but...