Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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

The present study addresses the capacity of heregulin (HRG), a ligand of type I receptor tyrosine kinases, to transactivate the progesterone receptor (PR). For this purpose, we studied, on the one hand, an experimental model of hormonal carcinogenesis in which the synthetic progestin medroxyprogesterone acetate (MPA) induced mammary adenocarcinomas in female BALB/c mice and, on the other hand, the human breast cancer cell line T47D. HRG was able to exquisitely regulate biochemical attributes of PR in a way that mimicked PR activation by progestins. Thus, HRG treatment of primary cultures of epithelial cells of the progestin-dependent C4HD murine mammary tumor line and of T47D cells induced a decrease of protein levels of PRA and -B isoforms and the downregulation of progesterone-binding sites. HRG also promoted a significant increase in the percentage of PR localized in the nucleus in both cell types. DNA mobility shift assay revealed that HRG was able to induce PR binding to a progesterone response element (PRE) in C4HD and T47D cells. Transient transfections of C4HD and T47D cells with a plasmid containing a PRE upstream of a chloramphenicol acetyltransferase (CAT) gene demonstrated that HRG promoted a significant increase in CAT activity. In order to assess the molecular mechanisms underlying PR transactivation by HRG, we blocked ErbB-2 expression in C4HD and T47D cells by using antisense oligodeoxynucleotides to ErbB-2 mRNA, which resulted in the abolishment of HRG's capacity to induce PR binding to a PRE, as well as CAT activity in the transient-transfection assays. Although the inhibition of HRG binding to ErbB-3 by an anti-ErbB-3 monoclonal antibody suppressed HRG-induced PR activation, the abolishment of HRG binding to ErbB-4 had no effect on HRG activation of PR. To investigate the role of mitogen-activated protein kinases (MAPKs), we used the selective MEK1/MAPK inhibitor PD98059. Blockage of MAPK activation resulted in complete abrogation of HRG's capacity to induce PR binding to a PRE, as well as CAT activity. Finally, we demonstrate here for the first time that HRG-activated MAPK can phosphorylate both human and mouse PR in vitro.
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PMID:Heregulin induces transcriptional activation of the progesterone receptor by a mechanism that requires functional ErbB-2 and mitogen-activated protein kinase activation in breast cancer cells. 1252 13

It has been reported that overexpression of the epidermal growth factor receptor (erbB1) or its homologous receptor, HER2 (erbB2), can confer antiestrogen resistance to estrogen receptor (ER)-positive human breast cancer cells. Aberrant signaling by receptors of the erbB network up-regulates a number of signaling pathways, which include phospholipase C-gamma1, Ras-Raf-mitogen-activated protein/extracellular signal-regulated kinase kinase-mitogen-activated protein kinase, phosphatidylinositol 3'-kinase and its target, the serine/threonine kinase Akt, stress-activated protein kinases, signal transducers and activators of transcription, and c-Jun-NH(2)-terminal kinase (JNK). Akt has been reported to induce estrogen-independent transcription of ER. Here we show that transfection of ER-positive, HER2 gene-amplified BT-74 cells with an expression vector encoding dominant-negative (K179M) Akt1 partially restored the ability of tamoxifen to inhibit estradiol-stimulated ER reporter activity. Infection of MCF-7 cells with an adenovirus encoding myristoylated, constitutively active Akt induced ER reporter activity in the absence of estradiol and resulted in tamoxifen resistance of these cells in culture. Data will be presented to suggest that, in addition to mitogen-activated protein kinase, Akt is an important mediator of HER2-mediated antiestrogen resistance in human breast cancer cells.
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PMID:ErbB (HER) receptors can abrogate antiestrogen action in human breast cancer by multiple signaling mechanisms. 1253 8

Recent evidence suggests that common molecular adaptations occur during resistance to both tamoxifen and estrogen deprivation that use various signal transduction pathways, often involving cross-talk with a retained and functional estrogen receptor (ER) protein. There appear to be several different levels at which this cross-talk may occur, including peptide growth factor signaling via the type 1 tyrosine kinase growth factor receptor family [epidermal growth factor receptor (EGFR) and HER2], which may become up-regulated during endocrine treatment, ultimately being harnessed by cells to allow them hormone-independent growth. ER may remain involved in cell growth with ligand-independent phosphorylation and activation via different intracellular mitogen-activated protein kinases. ER may also become involved in non-nuclear estrogen-dependent signaling via interaction with the phosphatidylinositol 3'-kinase/Akt cell survival pathway or may interact with the stress-activated protein kinase/c-Jun-NH(2)-terminal kinase pathway. Understanding these mechanisms will permit the optimal integration of new signal transduction inhibitors (STIs) into breast cancer therapy. Preclinical approaches that have shown promise include the use of EGFR tyrosine kinase inhibitors for hormone-resistant breast cancer cells that are dependent on either EGFR or HER2 signaling. Likewise, farnesyl transferase inhibitors, mitogen-activated protein kinase inhibitors, and cell cycle inhibitors have all shown activity in experimental breast cancer models. Emerging data suggest that STIs may be more effective when given in combination with endocrine therapy either to overcome resistance or to prevent/delay emergence of the resistance phenotype. Clinical trials are in progress to determine the safety and optimal schedule for each of the various STIs, and studies of STIs in combination with aromatase inhibitors have commenced in breast cancer to see whether the therapeutic response to endocrine therapy can be enhanced further.
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PMID:Integration of signal transduction inhibitors with endocrine therapy: an approach to overcoming hormone resistance in breast cancer. 1253 10

Experiments were carried out to determine the role of Raf-1 kinase in the development of drug resistance and apoptosis induced by paclitaxel. In the present study, paclitaxel sensitivity, Raf-1 activity and mitogen-activated protein kinases activation were compared in two cell lines: parental human breast cancer cells and its drug resistant variant (MCF-7/Adr) cells. Paclitaxel treatment of parental MCF-7 cells caused a marked inhibition of Raf-1 kinase activity, concomitant with its mobility shift after 18 h exposure. In addition, paclitaxel greatly increased c-Jun N-terminal protein kinase (JNK) activity whereas showing a small enhancing effect on extracellular-regulated kinases (ERK) activity. Interestingly, MCF-7/Adr cells have lower basal Raf-1 activity, yet have much higher basal ERK activity than parental cells. However, it appeared that PD 98059, which turns off ERK through mitogen-activated protein kinase kinase (MEK) inhibition, enhanced basal Raf-1 kinase activity in MCF-7/Adr cells. Thus, the findings suggest that paclitaxel-induced apoptosis is mediated by JNK and occurs in parallel with suppression of the Raf-1 kinase activity in parental MCF-7 cells. In addition, down-regulation of Raf-1 kinase, which can be induced through the sustained ERK activation, may contribute to the development of acquired resistance in MCF-7/Adr cells.
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PMID:Down-regulation of Raf-1 kinase is associated with paclitaxel resistance in human breast cancer MCF-7/Adr cells. 1269 24

The negative-regulatory feedback loop between p53 and hdm2 forms part of a finely balanced regulatory network of proteins that controls cell cycle progression and commitment to apoptosis. Expression of hdm2, and its mouse orthologue mdm2, is known to be induced by p53, but recent evidence has demonstrated mdm2 expression can also be regulated via p53-independent pathways. However the p53 independent mechanisms that control transcription of the human hdm2 gene have not been studied. Differential levels of hdm2 mRNA and protein expression have been reported in several types of human malignancy, including breast cancers in which hdm2 expression correlates with positive estrogen receptor alpha (ERalpha) status. Experimental models have demonstrated that hdm2 overexpression can promote breast cancer development. Here, we show that the elevated level of hdm2 protein in ERalpha(+ve) breast cancer cell lines such as MCF-7 and T47D is because of transcription from the p53-inducible P2 promoter of hdm2. The P2 promoter is inactive in ERalpha(-ve) cell lines such as SKBr3. Hdm2-P2 promoter activity in T47D cells is independent of p53, as well as of known regulators of the mouse mdm2-P2 promoter, including ERalpha and ras-raf-mitogen-activated protein/extracellular signal-regulated kinase (MEK) mitogen-activated protein kinase (MAPK) signaling. We show that hdm2-P2 activity in T47D cells is dependent on the integrity of both an evolutionarily conserved composite binding site for AP1 and ETS family transcription factors (AP1-ETS) and a nonconserved upstream (nnGGGGC)(5) repeat sequence. Lack of hdm2-P2 activity in ERalpha(-ve) cells is shown to be a consequence of reduced transcriptional activation through the AP1-ETS element. Overexpression of ETS2 in SKBr3 cells reconstitutes AP1-ETS element-dependent hdm2-P2 promoter activity, resulting in increased levels of hdm2 protein in the cells. Our findings support the hypothesis that the elevated levels of hdm2 expression reported in cancers such as ERalpha(+ve) breast tumors play an important role in the development of these tumors.
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PMID:p53-independent activation of the hdm2-P2 promoter through multiple transcription factor response elements results in elevated hdm2 expression in estrogen receptor alpha-positive breast cancer cells. 1275 Feb 88

Aromatase plays a critical role in breast cancer development by converting androgen to estrogen. In this report, results are presented to demonstrate that estrogen, the product of aromatase, can up-regulate its expression. Estrogen receptor (ER) transient transfection experiments were performed using the SK-BR-3 breast cancer cell line, which is ER negative and expresses aromatase. When SK-BR-3 cells were transfected with the expression plasmid pCI-ER alpha, but not pCI-ER beta, aromatase activity was elevated by 17beta-estradiol (E(2)) in a dose-dependent manner. The E(2) induction could be enhanced by cotransfection with the coactivator GRIP1 and suppressed by antiestrogens such as tamoxifen and ICI 182,780. The aromatase activity in the ER alpha-transfected SK-BR-3 cells could also be induced by environmental chemicals that were known to have an estrogen-like activity. Using aromatase gene exon Is-specific reverse transcription-PCR, the level of promoter I.1-driven transcripts was found to be elevated in E(2)-treated ER alpha-transfected cells. This suggested that E(2) induced aromatase expression through the up-regulation of promoter I.1. Using DNA deletion analysis of the 5'-flanking region of promoter I.1, the section between -300 and -280 bp upstream from exon I.1 was identified to be important for mediating E(2) induction. However, a direct binding of ER alpha to this 20-bp region could not be demonstrated. It was found that E(2) induction could be suppressed by the mitogen-activated protein/extracellular signal-regulated kinase kinase inhibitor, PD98059, and the epidermal growth factor receptor tyrosine kinase inhibitor, PD153035 hydrochloride. A significant induction of aromatase expression was also detected in ER-positive MCF-7 breast cancer cells after transfection with pCI-ER alpha and E(2) treatment. Furthermore, after ER alpha transfection and E(2) treatment, the aromatase activity in Her-2-overexpressing MCF-7 cells was drastically higher than that of the wild-type MCF-7 cells. In addition, aromatase induction in MCF-7 cells could also be suppressed by PD153035 hydrochloride. These results suggest that E(2) up-regulates aromatase expression by a nongenomic action of ER alpha via cross-talk with growth factor-mediated pathways.
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PMID:Induction of aromatase (CYP19) expression in breast cancer cells through a nongenomic action of estrogen receptor alpha. 1283 40

Interleukin-6 (IL-6) and interleukin-11 (IL-11) are frequently produced by breast cancer cells. These interleukins promote osteoclast formation and may mediate osteolysis at the site of breast cancer bone metastases. Transforming growth factor-beta (TGF-beta), tumor necrosis factor-alpha (TNF-alpha) and interleukin-1beta (IL-1beta) up-regulate IL-6 and IL-11 production in a cytokine-dependent fashion in breast cancer cells, but very little is known about their intracellular signaling pathways in breast cancer cells. To study TGF-beta, TNF-alpha and IL-1beta regulation of IL-6 and IL-11 production in human MDA-MB-231 breast cancer cells, we established single cell clones stably expressing dominant negative (DN) forms of the mitogen-activated protein kinases p38 (p38/AF) or ERK1 (ERK1K71R). We show here, that while basal, TGF-beta and IL-1beta induced IL-6 production was similar in parental cells and in pcDNA3 control, ERK1K71R and p38/AF clones, TNF-alpha induced IL-6 production was blunted in the ERK1K71R clones. TGF-beta and IL-1beta, but not TNF-alpha, induced IL-11 production in parental MDA-MB-231 cells. Similar findings were detected in clones stably expressing p38/AF and ERK1K71R, which did not change basal IL-11 production either. In conclusion, TNF-alpha induced IL-6 production is mediated via ERK1 activation in MDA-MB-231 cells. These observations may be helpful in designing new anti-osteolytic therapies.
Breast Cancer Res Treat 2003 Jul
PMID:Tumor necrosis factor-alpha induces interleukin-6 production via extracellular-regulated kinase 1 activation in breast cancer cells. 1288

Tamoxifen, a selective estrogen-receptor modulator, is effective in the treatment and prevention of breast cancer, but therapeutic resistance is common. Pure steroidal antiestrogens are efficacious in tamoxifen-resistant disease and, unlike tamoxifen, arrest cells in a state of quiescence from which they cannot reenter the cell cycle after growth factor stimulation. We now show that in hydroxytamoxifen-treated cells, transduction of the cell cycle inhibitor p27(Kip1) induces quiescence and insensitivity to growth stimulation by insulin/insulin-like growth factor I and epidermal growth factor/transforming growth factor alpha. Furthermore, reinitiation of cell cycle progression by insulin/insulin-like growth factor I in hydroxytamoxifen-arrested cells involves dissociation of the corepressors nuclear receptor corepressor (N-CoR) and silencing mediator for retinoid and thyroid hormone receptor (SMRT) from nuclear estrogen receptor alpha and redistribution to the cytoplasm, a process that is inhibited by mitogen-activated protein/extracellular signal-regulated kinase, but not phosphatidylinositol 3'-kinase, inhibitors. These data suggest that agents that up-regulate p27(Kip1) or inhibit growth factor signaling via the extracellular signal-regulated kinases should be tested as therapeutic strategies in tamoxifen-resistant breast cancer.
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PMID:p27(Kip1) induces quiescence and growth factor insensitivity in tamoxifen-treated breast cancer cells. 1290 98

Ras expression has been suggested as a marker for tumor aggressiveness of breast cancer,including the degrees of invasion and tumor recurrence.We showed previously that H-ras, but not N-ras, up-regulates matrix metalloproteinase 2 expression and induces invasive phenotype in MCF10A human breast epithelial cells (A. Moon, et al. Int. J. Cancer, 85: 176-181, 2000). In this study, we show that H-ras also promotes cell motility more effectively than N-ras in MCF10A cells. We have investigated H-ras-specific signaling pathway(s) critical for H-ras-mediated cell motility and invasive phenotype. Whereas neither H-ras nor N-ras activated c-Jun NH(2)-terminal kinase 1, both H-ras and N-ras effectively activated extracellular signal-regulated protein kinase (ERK) -1,2. Importantly, prominent activation of p38 mitogen-activated protein kinase was shown only in H-ras-activated cells but not in N-ras-activated MCF10A cells. Functional significance of H-ras-activated p38 in invasiveness and cell motility was evidenced by studies using SB203580, a chemical inhibitor of p38, and a dominant-negative construct of p38. Whereas inhibition of c-Jun NH(2)-terminal kinase 1 activity had no effect on H-ras-induced MCF10A cell invasion and motility, the inhibition of the ERK pathway using a chemical inhibitor PD98059 or dominant-negative mutant of mitogen-activated protein/ERK kinase 1, an activator of ERKs, significantly reduced H-ras-induced invasion and migration. We also provide evidence that p38 and, to a lesser degree, ERKs, are critical for H-ras-mediated up-regulation of matrix metalloproteinase 2. Taken together, the present study shows that H-ras activation of both p38 and ERKs induces cell invasion and motility, whereas N-ras activation of ERKs alone is not sufficient. This study reveals the p38 kinase as a key signaling molecule differentially regulated by H-ras and N-ras, leading to H-ras-specific cell invasive and migrative phenotypes in human breast epithelial cells.
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PMID:p38 kinase is a key signaling molecule for H-Ras-induced cell motility and invasive phenotype in human breast epithelial cells. 1450 Mar 81

The effects of hormone and growth factor signaling on gene expression contribute significantly to breast tumorigenesis and disease progression; however, the targets of signaling networks associated with deregulated growth are not well understood. We defined the dynamic transcriptional effects elicited in MCF7, T-47D, and MDA-MB-436 breast cancer cell lines by nine regulators of growth and differentiation (17beta-estradiol, antiestrogens fulvestrant and tamoxifen, progestin R5020, antiprogestin RU486, all-trans-retinoic acid, epidermal growth factor, mitogen-activated protein/extracellular signal-regulated kinase 1/2 inhibitor U0126 and phorbol ester 12-O-tetradecanoylphorbol-13-acetate) and compared the patterns of gene regulation to published tumor expression profiles. The complex pattern of response to these agents revealed unexpected relationships between their effects, including a profound overlap in genes regulated by both steroids and epidermal growth factor, and striking overlaps between fulvestrant and all-trans-retinoic acid. Estrogen-responsive genes could be divided into two major clusters, only one of which is associated with cell proliferation. Gene ontology analysis was used to highlight functionally distinct biological responses to different mitogens. Significant correlations were identified between several clusters of drug-responsive genes and genes that discriminate estrogen receptor status or disease outcome in patient samples. The majority of estrogen receptor status discriminators were not responsive in our dataset and are therefore likely to reflect underlying differences in histogenesis and disease progression rather than growth factor signaling. This article highlights the overall impact at the gene expression level of diverse regulators of breast cancer growth and links the behavior of breast cancer cells in culture to important clinical properties of human breast tumors.
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PMID:The gene expression response of breast cancer to growth regulators: patterns and correlation with tumor expression profiles. 1461 9


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