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)

Estrogen rapidly induces expression of the proto-oncogene c-myc. c-Myc is required for estrogen-stimulated proliferation of breast cancer cells, and deregulated c-Myc expression has been implicated in antiestrogen resistance. In this report, we investigate the mechanism(s) by which c-Myc mediates estrogen-stimulated proliferation and contributes to cell cycle progression in the presence of antiestrogen. The MCF-7 cell line is a model of estrogen-dependent, antiestrogen-sensitive human breast cancer. Using stable MCF-7 derivatives with inducible c-Myc expression, we demonstrated that in antiestrogen-treated cells, the elevated mRNA and protein levels of p21(WAF1/CIP1), a cell cycle inhibitor, decreased upon either c-Myc induction or estrogen treatment. Expression of p21 blocked c-Myc-mediated cell cycle progression in the presence of antiestrogen, suggesting that the decrease in p21 is necessary for this process. Using RNA interference to suppress c-Myc expression, we further established that c-Myc is required for estrogen-mediated decreases in p21(WAF1/CIP1). Finally, we observed that neither c-Myc nor p21(WAF1/CIP1) is regulated by estrogen or antiestrogen in an antiestrogen-resistant MCF-7 derivative. The p21 levels in the antiestrogen-resistant cells increased when c-Myc expression was suppressed, suggesting that loss of p21 regulation was a consequence of constitutive c-Myc expression. Together, these studies implicate p21(WAF1/CIP1) as an important target of c-Myc in breast cancer cells and provide a link between estrogen, c-Myc, and the cell cycle machinery. They further suggest that aberrant c-Myc expression, which is frequently observed in human breast cancers, can contribute to antiestrogen resistance by altering p21(WAF1/CIP1) regulation.
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PMID:c-Myc suppresses p21WAF1/CIP1 expression during estrogen signaling and antiestrogen resistance in human breast cancer cells. 1575 89

Constitutively activated STAT3 is involved in the formation of multiple types of tumors including breast cancer. We examined the effects of Stat3 protein knockdown by RNA interference using a dicistronic lentivirus small hairpin (shRNA) delivery system on the growth of mammary tumors in BALB/c mice induced by the 4T1 cell line. A single exposure of 4T1 cells to shRNA/STAT3 lentivirus transduced 75% of the cells with green fluorescent protein (GFP) within 96 hours. In cells selected for GFP expression, neither Stat3 protein nor phosphotyrosine Stat3 was detected. Tumor formation induced by injecting 4T1 cells into the mammary fat pad was blocked by expression of the shRNA for STAT3 whereas all mice injected with 4T1 cells expressing only GFP efficiently formed tumors. c-Myc expression was reduced 75% in cells expressing greatly reduced levels of Stat3 compared with the GFP control. Of interest, the level of activated Src, which is known to activate Stat3, was virtually eliminated but the level of the Src protein itself remained the same. Importantly, expression of Twist protein, a metastatic regulator, was eliminated in STAT3 knockdown cells. Invasion activity of STAT3 knockdown cells was strongly inhibited. However, the proliferation rate of cells in Stat3 knockdown cells was similar to that of the GFP control; the cell cycle was also not affected. We conclude from these studies that activated Stat3 protein plays a critical role in the induction of breast tumors induced by 4T1 cells by enhancing the expression of several important genes including c-Myc and the metastatic regulator Twist. These studies suggest that stable expression of small interfering RNA for STAT3 has potential as a therapeutic strategy for breast cancer.
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PMID:Knockdown of STAT3 expression by RNA interference inhibits the induction of breast tumors in immunocompetent mice. 1580 44

Using microarray gene analysis, we found that carboxyl-terminal Src kinase homologous kinase (CHK) regulated the expression of the chemokine receptor, CXCR4. Northern blot and fluorescence-activated cell-sorting analyses showed that CHK down-regulated CXCR4 mRNA and protein levels, respectively. Mutated CHK, which contains a mutation within the ATP binding site of CHK, failed to inhibit CXCR4 expression, thus suggesting that CHK kinase activity is involved in the regulation of CXCR4. Results from gel shift analysis indicated that CHK regulates CXCR4 transcriptional activity by altering YY1 binding to the CXCR4 promoter. Whereas CHK had no significant effects on the expression of YY1, c-Myc, Max, and other YY1-binding proteins, CHK was found to modulate the YY1/c-Myc association. Furthermore, CHK inhibited CXCR4-positive breast cancer cell migration. Taken together, these studies show a novel mechanism by which CHK down-regulates CXCR4 through the YY1 transcription factor, leading to decreased CXCR4-mediated breast cancer cell motility and migration.
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PMID:Carboxyl-terminal Src kinase homologous kinase negatively regulates the chemokine receptor CXCR4 through YY1 and impairs CXCR4/CXCL12 (SDF-1alpha)-mediated breast cancer cell migration. 1580 85

Traditionally, gene signatures are statistically deduced from large gene expression and proteomics datasets and have been applied as an experimental molecular diagnostic technique that is sensitive to experimental design and statistical treatment. We have developed and applied the approach of "signature networks" which overcomes some of the drawbacks of clustering methods. We have demonstrated signature network assembly, functional analysis and logical operations on the networks that can be generated. In addition, we have used this technique in a proof of concept study to compare the effect of differential drug treatment using 4-hydroxytamoxifen and estrogen on the MCF-7 breast cancer cell line from a previously published study. We have shown that the two compounds can be differentiated by the networks of interacting genes. Both networks consist of a core module of genes including c-Fos as part of c-Fos/c-Jun heterodimer and c-Myc which is clearly visible. Using algorithms in our MetaCore software we are able to subtract the 4-hydroxytamoxifen and estrogen networks to further understand differences between these two treatments and show that the estrogen network is assembled around the core with other modules essential for all phases of the cell cycle. For example, Cyclin D1 is present in networks for the estrogen treated cells from two separate studies. These signature networks represent an approach to identify biomarkers and a general approach for discovering new relationships in complex high throughput toxicology data.
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PMID:A novel method for generation of signature networks as biomarkers from complex high throughput data. 1587 13

The epithelial cell adhesion molecule, EpCAM, is a transmembrane glycoprotein associated with both benign and malignant proliferation. In cancer cells, expression levels of this tumour-associated antigen correlate positively with the grade of dysplasia and are also a negative prognostic factor for breast cancer patients. De novo expression of EpCAM resulted in the rapid upregulation of the proto-oncogene c-Myc along with enhanced cell proliferation and metabolism. Here, we analyzed the effects of EpCAM onto the proteome of epithelial cells. The epidermal fatty acid binding protein, E-FABP, was identified as a new EpCAM-regulated protein. E-FABP is a major target of c-Myc and was rapidly upregulated upon induction of EpCAM. Additionally, E-FABP levels correlated with the amount of EpCAM in permanent squamous cell carcinoma lines and in vivo in primary head and neck carcinomas. Taken together, these results provide further evidence for the direct involvement of EpCAM in signalling processes, gene regulation, and cellular metabolism supporting its important role in tumour biology.
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PMID:The tumour-associated antigen EpCAM upregulates the fatty acid binding protein E-FABP. 1592 67

The constitutive activation of signal transducer and activator of transcription 3 (Stat3) is frequently detected in breast cancer tissues and cell lines. Stat3 has been classified as a proto-oncogene, because an activated form of Stat3 can mediate oncogenic transformation in cultured cells and tumor formation in nude mice. Since Stat3 may play an important role in breast cancer, it is of interest to investigate the expression of phosphorylated Stat3, an activated form of Stat3, and its downstream mediators specifically in breast cancer, and to explore the possible mechanisms of Stat3 signaling pathway in oncogenesis of breast cancer. We analyzed Stat3 phosphorylation and expression of Stat3-regulated genes in breast cancer cell lines as well as invasive breast cancer tissues using tissue microarray slides. Our results showed that elevated levels of phosphorylation of Stat3 protein (Tyr705) were detected in 48 out of total 136 invasive breast tumors (35%) whereas normal breast tissues express much lower levels of Stat3 phosphorylation. The increased levels of Stat3 phosphorylation were associated with the metastasis in regional lymph nodes (P=0.042) and the expression of progesterone receptor (P=0.028) but not with distant metastasis, nor the expression of estrogen receptor. Our results also indicate that elevated levels of Stat3 phosphorylation were significantly associated with increased expression of potential downstream targets of Stat3 which include apoptosis inhibitors (Survivin, Mcl-1, HSP27, Adrenomedullin, and Bcl-xL), cell-cycle regulators (c-Fos, MEK5, and c-Myc), and inducer of tumor angiogenesis (VEGF, COX-2, MMP-2, MMP-10, and MMP-1) in invasive breast cancer tissues. Therefore, our findings suggest that constitutive Stat3 signaling may be one of the key upstream regulators to induce these downstream proteins, which may play important roles in Stat3-mediated oncogenesis in breast cancer.
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PMID:Evaluation of potential Stat3-regulated genes in human breast cancer. 1608 Oct 48

The aryl hydrocarbon receptor (AhR) is an environmental carcinogen-activated transcription factor associated with tumorigenesis. High levels of apparently active AhR characterize a variety of tumors, even in the absence of environmental ligands. Despite this association between transformation and AhR upregulation, little is known of the transcriptional consequences of constitutive AhR activation. Here, the effects of constitutively active and environmental ligand-induced AhR on c-myc, an oncogene whose promoter contains six AhR-binding sites (AhREs (aryl hydrocarbon response elements)), were investigated. A reporter containing the human c-myc promoter, with its six AhREs and two NF-kappaB-binding sites, was constructed. This vector, and variants with deletions in the NF-kappaB and/or AhR-binding sites, was transfected into a human breast cancer cell line, Hs578T, which expresses high levels of apparently active, nuclear AhR. Results indicate that: (1) the AhR constitutively binds the c-myc promoter; (2) there is a low but significant baseline level of c-myc promoter activity, which is not regulated by NF-kappaB and is not affected by an environmental AhR ligand; (3) deletion of any one of the AhREs has no effect on constitutive reporter activity, while deletion of all six increases reporter activity approximately fivefold; (4) a similar increase in reporter activity occurs when constitutively active AhR is suppressed by transfection with an AhR repressor plasmid (AhRR); (5) AhRR transfection significantly increases background levels of endogenous c-myc mRNA and c-Myc protein. These results suggest that the AhR influences the expression of c-Myc, a protein critical to malignant transformation.
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PMID:The aryl hydrocarbon receptor constitutively represses c-myc transcription in human mammary tumor cells. 1609 46

Antioestrogen therapy is a highly effective treatment for patients with oestrogen-receptor (ER)-positive breast cancer, emphasising the central role of oestrogen action in the development and progression of this disease. However, effective antioestrogen treatment is often compromised by acquired endocrine resistance, prompting the need for a greater understanding of the down-stream mediators of oestrogen action that may contribute to this effect. Recent studies have demonstrated a critical link between oestrogen's mitogenic effects and cell cycle progression, particularly at the G1 to S transition where key effectors of oestrogen action are c-Myc and cyclin D1, which converge on the activation of cyclin E-cdk2. These components are rapidly upregulated in response to oestrogen, and can mimic its actions on cell cycle progression, including re-initiating cell proliferation in antioestrogen-arrested cells. Here we review the roles of c-Myc, cyclin D1 and cyclin E in oestrogen action and endocrine resistance, and identify their potential as markers of disease progression and endocrine responsiveness, and as novel therapeutic targets in endocrine-resistant breast cancer.
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PMID:Downstream targets of growth factor and oestrogen signalling and endocrine resistance: the potential roles of c-Myc, cyclin D1 and cyclin E. 1611 99

Currently, there is no effective therapy for metastatic breast cancer after surgery, radiation, and chemotherapy have been used against the primary tumor. Because curcumin suppresses nuclear factor-kappaB (NF-kappaB) activation and most chemotherapeutic agents activate NF-kappaB that mediates cell survival, proliferation, invasion, and metastasis, we hypothesized that curcumin would potentiate the effect of chemotherapy in advanced breast cancer and inhibit lung metastasis. We tested this hypothesis using paclitaxel (Taxol)-resistant breast cancer cells and a human breast cancer xenograft model. As examined by electrophoretic mobility gel shift assay, paclitaxel activated NF-kappaB in breast cancer cells and curcumin inhibited it; this inhibition was mediated through inhibition of IkappaBalpha kinase activation and IkappaBalpha phosphorylation and degradation. Curcumin also suppressed the paclitaxel-induced expression of antiapoptotic (XIAP, IAP-1, IAP-2, Bcl-2, and Bcl-xL), proliferative (cyclooxygenase 2, c-Myc, and cyclin D1), and metastatic proteins (vascular endothelial growth factor, matrix metalloproteinase-9, and intercellular adhesion molecule-1). It also enhanced apoptosis. In a human breast cancer xenograft model, dietary administration of curcumin significantly decreased the incidence of breast cancer metastasis to the lung and suppressed the expression of NF-kappaB, cyclooxygenase 2, and matrix metalloproteinase-9. Overall, our results indicate that curcumin, which is a pharmacologically safe compound, has a therapeutic potential in preventing breast cancer metastasis possibly through suppression of NF-kappaB and NF-kappaB-regulated gene products.
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PMID:Curcumin suppresses the paclitaxel-induced nuclear factor-kappaB pathway in breast cancer cells and inhibits lung metastasis of human breast cancer in nude mice. 1624 23

Classical NF-kappaB (p65/p50) transcription factors display dynamic induction in the mammary gland during pregnancy. To further elucidate the role of NF-kappaB factors in breast development, we generated a transgenic mouse expressing the IkappaB-alpha S32/36A superrepressor (SR) protein under control of the mouse mammary tumor virus (MMTV) long terminal repeat promoter. A transient delay in mammary ductal branching was observed in MMTV-SR-IkappaB-alpha mice early during pregnancy at day 5.5 (d5.5) and d7.5; however, development recovered by mid- to late pregnancy (d14.5). Recovery correlated with induction of nuclear cyclin D1 and RelB/p52 NF-kappaB complexes. RelB/p52 complexes induced cyclin D1 and c-myc promoter activities and failed in electrophoretic mobility shift assay to interact with IkappaB-alpha-glutathione S-transferase, indicating that their weak interaction with IkappaB-alpha can account for the observed recovery of mammary gland development. Activation of IKKalpha and NF-kappaB-inducing kinase was detected by d5.5, implicating the alternative NF-kappaB signaling pathway in RelB/p52 induction. Constitutively active IKKalpha induced p52, RelB, and cyclin D1 in untransformed mammary epithelial cells. Moreover, mouse mammary tumors induced by 7,12-dimethylbenz(a)anthracene treatment displayed increased RelB/p52 activity. Inhibition of RelB in breast cancer cells repressed cyclin D1 and c-Myc levels and growth in soft agar. These results implicate RelB/p52 complexes in mammary gland development and carcinogenesis.
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PMID:RelB/p52 NF-kappaB complexes rescue an early delay in mammary gland development in transgenic mice with targeted superrepressor IkappaB-alpha expression and promote carcinogenesis of the mammary gland. 1626 Jun 26


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