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Query: UMLS:C0006142 (breast cancer)
 160,383 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Estrogen receptor (ER) status is an important parameter in breast cancer management. In this study, ER protein contents established by two conventional techniques were confronted to ER mRNA level, to analyze whether the latter may be introduced in routine assay. Eighty-seven breast tumor samples were examined. ER amounts were determined by ligand-binding assay (LBA) and by computer-assisted immunocytochemical assay (ICA), ER mRNA was analysed and quantified by northern blot. Seventy-seven percent of tumor samples examined were positive for ER mRNA and they all expressed the 6.7-kb receptor signal. No trace of small-sized ER mRNA variants was detected in any sample. Following akaike information criterion (AIC) discriminant analysis, a simple linear correlation was found between ER mRNA levels and ER amounts provided by LBA. This was not observed when either mRNA or LBA values were compared to ICA values. These latter were found to rapidly reach a plateau at increasing mRNA or LBA values. In conclusion, our data points to the linear correlation between ER amounts determined in breast tumors at both protein and mRNA levels by quantitative methods; they also indicate that the semi-quantitative computer-associated ICA may complement rather than replace these quantitative methods.
Breast Cancer Res Treat 2001 Jun
PMID:Estrogen receptor analysis in primary breast tumors by ligand-binding assay, immunocytochemical assay, and northern blot: a comparison. 1156 72

Formation of transcriptional repression complexes such as DNA methyltransferase (DNMT) 1/histone deacetylase (HDAC) or methyl-CpG binding protein/HDAC is emerging as an important mechanism in silencing a variety of methylated tissue-specific and imprinted genes. Our previous studies showed that treatment of estrogen receptor (ER)-alpha-negative human breast cancer cells with the DNMT inhibitor 5-aza-2'-deoxycytidine (5-aza-dC) led to ER mRNA and protein re-expression. Also, the HDAC inhibitor trichostatin A (TSA) could induce ER transcript about 5-fold. Here we show that 5-aza-dC alone induced ER transcript about 30-40-fold, and the addition of TSA elevated ER mRNA expression about 10-fold more in the human ER-negative breast cancer cell lines MDA-MB-231 and MDA-MB-435. Overall, the combination of 5-aza-dC and TSA induced a 300-400-fold increase in ER transcript. Restoration of estrogen responsiveness was demonstrated by the ability of the induced ER protein to elicit estrogen response element-regulated reporter activity from an exogenous plasmid as well as induce expression of the ER target gene, progesterone receptor. The synergistic activation of ER occurs concomitantly with markedly reduced soluble DNMT1 expression and activity, partial demethylation of the ER CpG island, and increased acetylation of histones H(3) and H(4). These data suggest that the activities of both DNMT1 and HDAC are key regulators of methylation-mediated ER gene silencing.
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PMID:Synergistic activation of functional estrogen receptor (ER)-alpha by DNA methyltransferase and histone deacetylase inhibition in human ER-alpha-negative breast cancer cells. 1158 28

Most mammary carcinomas contain estrogen receptors (ER), which are an important factor in diagnosis and prognosis, and in deciding on the type of therapy. ER-positive tumors are most commonly treated with the antiestrogen tamoxifen or with a combination of chemotherapeutic drugs. An important aspect for further treatment and anticipating possible side effects is the fate of the ER during the course of therapy. To study the effect of drug-induced growth inhibition on ER expression and binding properties. human breast cancer MCF-7 cells were treated with tamoxifen and cisplatin. and also estradiol (E2) for 5 days. Following this incubation, intact cells were incubated with [3H]E2 to determine the dissociation constant (KD) and maximal number of binding sites (Bmax) of the ER. The amount of ER protein per cell was quantified using anti-ER antibodies. For analysis of ER mRNA, total cellular RNA was subjected to Northern blotting. The 5-day treatment with E2 reduced Bmax and the amount of ER protein by about 70%, while the cellular level of ER mRNA was reduced by 40%. Treatment with E2 did not affect the subsequent growth inhibitory response to tamoxifen or cisplatin. In contrast, tamoxifen reduced the capacity for E2 binding; it caused about a 30-fold increase in the KD value. At the same time, Bmax and ER protein content were increased (about 3.5- and 2-fold, respectively), but the cellular level of ER mRNA was again reduced by 40%. The growth of tamoxifen-treated cells remained sensitive to subsequent treatment with estradiol, tamoxifen or cisplatin. Treatment of MCF-7 cells with cisplatin likewise reduced E2 binding due to a 20-fold increase in KD value. In this case, both Bmax and the amount of ER protein were decreased when calculated per milligram of protein, but were increased on a cellular basis due to an increase in cell size. The ER mRNA content was not altered in cisplatin-treated cells. Growth of these cells also remained sensitive to tamoxifen and cisplatin. In conclusion, drug-induced changes in ER expression and binding capacity do not necessarily indicate a loss of sensitivity of breast cancer cells to a subsequent chemotherapeutic treatment.
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PMID:Changes in the expression and binding properties of the estrogen receptor in MCF-7 breast cancer cells during growth inhibition by tamoxifen and cisplatin. 1171 Jun 31

Antiestrogens block the function of estrogen receptor (ER) by binding and misfolding the AF-2 transcriptional activation region in the ligand-binding domain, inhibiting or altering its association with coactivator proteins. We describe a novel assay uniquely configured to identify aberrations in this function that may lead to antiestrogen resistance. The identification of mutations of ER that affect its function is important to current breast cancer therapies. Standard methods to detect these mutations are cumbersome and the number of described mutations is limited, reflecting this difficulty. Conventional ER analysis in the clinic demonstrates the presence of antigenic determinants of the receptor protein or estrogenic ligand binding without reflection on the critical ability of the liganded receptor to interact with transcription cofactors. Here, we describe the use of estrogenic regulation of a site-specific recombinase activity, measuring deletion of a color marker gene via FLP-ER fusion proteins, to detect functional changes in ER protein folding that affects the site where cofactors interact. The assay provides a method to readily detect single amino acid changes in ER, some with biologically important consequences. Without such a functional assay as described, phenotypic changes are likely to remain undetected and under-evaluated. It is probable that some human tumors have antihormone resistance resulting from ER mutations that either block antihormone binding or transmit antihormone binding as a positive transcriptional signal via cofactor interaction. An assay to evaluate functional ER will lead to better predictive tests of treatment modalities.
Breast Cancer Res Treat 2002 Mar
PMID:Functional mutations of estrogen receptor protein: assay for detection. 1200 7

The estrogen receptor (ER)-alpha protein and ER mRNA were measured in 314 primary breast cancer patients by enzyme immunoassay (EIA) and reverse-transcription polymerase chain reaction (RT-PCR) assay, respectively. The positivity of ER protein was 53% while of ER mRNA was 37.6%. A significant positive association between ER phenotype and ER mRNA was observed (r = 0.40, p < 0.0001) with a positive-negative agreement between them of 71.8%. The percentage of ER-negative, progesterone receptor (PR)-positive breast tumors was 1.9% by EIA and 7% by RT-PCR assay. This may indicate a difference in ER variants in these studied patients. The ER protein and ER mRNA status were inversely related to tumor size and p53 positivity. Also, ER protein was frequently positive in patients with a higher number of lymph node invasions, well to moderate nuclear differentiated tumor cells and negative c-erbB-2 status. The difference of the ER or ER mRNA status regarding ages, menopausal status, tumor stages and histological types was not shown. In the present study, ER mRNA did not demonstrate a closer relationship to prognostic indicators of breast cancer than ER protein. Before including the ER mRNA assessment in routine investigations of breast cancer, its relationship to prognostic factors and survival outcome should be further assessed with a higher number of patients and a longer follow-up time.
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PMID:Estrogen receptor-alpha mRNA in primary breast cancer: relationship to estrogen and progesterone receptor proteins and other prognostic factors. 1212 13

Since its introduction more than 30 years ago, tamoxifen has been the most widely used endocrine therapy for the treatment of women with advanced breast cancer. More recently, a number of alternative endocrine treatments have been developed, including several selective estrogen receptor modulators (SERMs), aromatase inhibitors (AIs) and, most recently, fulvestrant ('Faslodex'). Fulvestrant is an estrogen receptor (ER) antagonist, which, unlike the SERMs, has no known agonist (estrogenic) effect and downregulates the ER protein. Tamoxifen is effective and well tolerated, although the non-steroidal AIs, anastrozole and letrozole, are more effective treatments for advanced disease than tamoxifen. Fulvestrant has recently gained US Food and Drug Administration approval for the treatment of hormone receptor-positive metastatic breast cancer in postmenopausal women with disease progression following antiestrogen therapy. In two global phase III clinical trials fulvestrant was at least as effective and as equally well tolerated as anastrozole for the treatment of postmenopausal women with advanced and metastatic breast cancer. In a retrospective analysis of the combined data from these trials, mean duration of response was significantly greater for fulvestrant compared with anastrozole. These new hormonal treatments expand the choice of endocrine therapy for women with advanced breast cancer and offer new options for sequencing and combining treatments.
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PMID:Fulvestrant ('Faslodex')--a new treatment option for patients progressing on prior endocrine therapy. 1254 3

Resveratrol (Res) is a phytoestrogen found in grapes and present in red wine. Res has been shown to function as an estrogen receptor (ER) agonist, but it remains unclear whether it may also exert antagonist activity. Our aim was to study the effects of Res at both the molecular (TGFalpha gene activation) and the cellular (cell growth) levels in breast cancer cells stably transfected with wild-type (wt) ER(D351) and mutant (mut) ER (D351Y). TGFalpha mRNA induction was used as a specific marker of estradiol (E(2)) responsiveness. Res caused a concentration-dependent (10(-8)-10(-4) M) stimulation of TGFalpha mRNA, indicating that it acts as an estrogen agonist in these cell lines. The pure antiestrogen ICI 182,780 (ICI) blocked Res-induced activation of TGFalpha, consistent with action through an ER-mediated pathway. Further studies that combined treatments with E(2) and Res showed that Res does not act as an antagonist in the presence of various (10(-11)-10(-8) M) concentrations of E(2). To determine whether Res can be classified as a type I or type II estrogen (Jordan et al., Cancer Res 2001;61:6619-23,), we examined Res with the D351G ER in the TGFalpha assay and found that Res belongs to the type I estrogens. Both Res and E(2) had concentration-dependent growth inhibitory effects in cells expressing wtER and D351Y ER. Although the pure antiestrogen ICI blocked the growth inhibitory effects of E(2), it did not block the inhibitory effects of Res, suggesting that the antiproliferative effects of Res also involve ER-independent pathways. Interestingly, Res differentially affected the levels of ER protein in these 2 cell lines: Res down-regulated wtER levels while significantly up-regulating the amount of mutD351Y ER. Co-treatment with ICI resulted in strongly reduced ER levels in both cell lines. Gene array studies revealed Res-induced up-regulation of more than 80 genes, among them a profound activation of p21(CIP1)/WAF1, a gene associated with growth arrest. The p21(CIP1)/WAF1 protein levels measured by Western blotting confirmed Res-induced significant up-regulation of this protein in both cell lines. In summary, Res acts as an ER agonist at low doses but also activates ER-independent pathways, some of which inhibit cell growth.
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PMID:Resveratrol acts as an estrogen receptor (ER) agonist in breast cancer cells stably transfected with ER alpha. 1259 13

Oxidant-induced structural modifications within the cysteine-rich DNA-binding domain (DBD) of the overexpressed estrogen receptor (ER) likely contribute to its loss of DNA-binding function and altered transcriptional activity during human breast cancer development. Using recombinant ER protein as a model, procedures to detect such endogenously produced structural changes in the two Cys(4)-type zinc fingers within the DBD of ER extracted from breast cancer cells are being developed. Unfortunately, ex vivo oxidation of these ER-DBD cysteine residues can occur during routine ER purification and preparation procedures. Also, cysteine residues readily undergo thiol-disulfide exchange reactions that can result in artificial oxidation and incorrect disulfide bond assignments. These problems can be circumvented by an initial irreversible alkylation of all free thiols followed by reduction of any disulfides and treatment with a second alkylating agent, prior to proteolysis and high-performance liquid chromatography mass spectrometry analysis of peptides in the doubly alkylated ER digest, to differentiate between the originally free and the disulfide-bonded cysteine residues. Although the use of chemically identical but isotopically different alkylating agents was more effective than the use of chemically different alkylating agents, subsequent problems were encountered with incomplete alkylation of particular Cys residues in the native ER protein. To overcome this limitation, the initial alkylation was accompanied by denaturation and the second alkylation was carried out during the proteolytic digestion. These improved analytical strategies should facilitate the monitoring of structurally altered endogenous ER produced within oxidant-stressed human breast cancer cells.
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PMID:Essential cysteine-alkylation strategies to monitor structurally altered estrogen receptor as found in oxidant-stressed breast cancers. 1289 66

Oestrogen receptor (ER) levels are usually maintained on acquisition of tamoxifen resistance in the clinic, however, tumour re-growth is associated with increased expression of epidermal growth factor receptor (EGFR) and activation of the mitogen activated protein kinase (MAPK) pathway. In the present study we have used the ER down-regulator fulvestrant ('Faslodex') to investigate the influence of the ER on growth of a tamoxifen-resistant (TAM-R) human breast cancer cell line. Expression levels of ER mRNA and protein were equivalent in parental wild-type MCF-7 (WT) and TAM-R cells. Fulvestrant eliminated ER protein expression and inhibited proliferation in both cell lines. The growth inhibitory effects of fulvestrant were associated with a decrease in basal EGFR, c-erbB2 and ERK1/2 activity in TAM-R but not WT cells. ER functionality as determined by oestrogen response element (ERE)-luciferase reporter activity and expression of PgR, pS2 and transforming growth factor alpha (TGFalpha) was significantly reduced in TAM-R compared to WT cells and was further decreased by fulvestrant treatment in both cell lines. Epidermal growth factor (EGF) and TGFalpha significantly increased EGFR/MAPK pathway activity in both cell lines. Ligand-induced EGFR/MAPK activation promoted TAM-R cell growth in both the absence and presence of fulvestrant, whereas no proliferative activity was observed under the same conditions in WT cells. These results suggest that the ER modulates EGFR/MAPK signalling efficiency in TAM-R cells possibly through the regulation of TGFalpha availability. This effect may be overcome by the action of exogenous EGFR ligands, which strengthen EGFR/MAPK signalling activity to generate endocrine-insensitive cell growth.
Breast Cancer Res Treat 2003 Sep
PMID:Oestrogen receptor-mediated modulation of the EGFR/MAPK pathway in tamoxifen-resistant MCF-7 cells. 1453

The use of adjuvant endocrine therapy in the treatment of hormone receptor-positive, early breast cancer has become important in both pre- and postmenopausal women. Tamoxifen has been the principal adjuvant hormonal therapy in pre- and postmenopausal women with hormone receptor-positive breast cancer for nearly 20 years. Recent data in premenopausal women suggest benefit from ovarian ablation with or without tamoxifen. Early results from the 'Arimidex', Tamoxifen, Alone or in Combination (ATAC) trial have demonstrated that the third-generation, selective aromatase inhibitor (AI) anastrozole ('Arimidex') is a suitable alternative adjuvant therapy for postmenopausal women with hormone receptor-positive disease. After recurrence or relapse on adjuvant endocrine therapy, responses to the sequential use of additional endocrine agents are common. The increase in the number of options now available for adjuvant therapy will have important implications for the selection of the optimal sequence of endocrine agents in the treatment of recurrent breast cancer. Menopausal status is an important factor in determining the endocrine therapy that a patient receives. For premenopausal women, tamoxifen and/or a luteinizing hormone-releasing hormone agonist such as goserelin ('Zoladex') are both options for adjuvant endocrine treatment. After progression on adjuvant and first-line tamoxifen, ovarian ablation is an appropriate second-line therapy. For premenopausal women who have undergone ovarian ablation, the use of third-line therapy with an AI becomes possible. For postmenopausal women, a wide choice of endocrine treatment options is available and an optimal sequence has yet to be determined. Options for first-line therapy of metastatic disease include an AI for women who have received adjuvant tamoxifen or tamoxifen for patients who have received adjuvant anastrozole. In addition, data suggest that fulvestrant ('Faslodex'), a novel estrogen receptor (ER) antagonist that downregulates the ER protein and has no known agonist effects, is a promising therapeutic option that has shown efficacy in the treatment of postmenopausal women with advanced breast cancer. Other agents that may be used in the sequence include the steroidal AI exemestane and the progestin megestrol acetate. The widening range of adjuvant endocrine options therefore represents an opportunity to prolong patient benefits in the treatment of hormone receptor-positive breast cancer, and will require the further refinement of the optimal sequence of endocrine agents for the treatment of recurrent breast cancer.
Breast Cancer Res Treat 2003
PMID:Sequential hormonal therapy for metastatic breast cancer after adjuvant tamoxifen or anastrozole. 1453 31


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