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Chegini N, Kornberg L. Gonadotropin Releasing Hormone Analogue Therapy Alters Signal Transduction Pathways Involving Mitogen-Activated Protein and Focal Adhesion Kinases in Leiomyoma. ACTA ACUST UNITED AC 2016. [DOI: 10.1177/107155760301000105] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Affiliation(s)
- Nasser Chegini
- Departments of Obstetrics and Gynecology and Otolaryngology, University of Florida, Gainesville, Florida; Department of OB/GYN, University of Florida, Box 100294, Gainesville, FL 32610
| | - Lori Kornberg
- Departments of Obstetrics and Gynecology and Otolaryngology, University of Florida, Gainesville, Florida
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Slattery ML, Lundgreen A, John EM, Torres-Mejia G, Hines L, Giuliano AR, Baumgartner KB, Stern MC, Wolff RK. MAPK genes interact with diet and lifestyle factors to alter risk of breast cancer: the Breast Cancer Health Disparities Study. Nutr Cancer 2015; 67:292-304. [PMID: 25629224 DOI: 10.1080/01635581.2015.990568] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Mitogen-activated protein kinases (MAPK) are integration points for multiple biochemical signals. We evaluated 13 MAPK genes with breast cancer risk and determined if diet and lifestyle factors mediated risk. Data from 3 population-based case-control studies conducted in Southwestern United States, California, and Mexico included 4183 controls and 3592 cases. Percent Indigenous American (IA) ancestry was determined from 104 ancestry informative markers. The adaptive rank truncated product (ARTP) was used to determine the significance of each gene and the pathway with breast cancer risk, by menopausal status, genetic ancestry level, and estrogen receptor (ER)/progesterone receptor (PR) strata. MAP3K9 was associated with breast cancer overall (P(ARTP) = 0.02) with strongest association among women with the highest IA ancestry (P(ARTP) = 0.04). Several SNPs in MAP3K9 were associated with ER+/PR+ tumors and interacted with dietary oxidative balance score (DOBS), dietary folate, body mass index (BMI), alcohol consumption, cigarette smoking, and a history of diabetes. DUSP4 and MAPK8 interacted with calories to alter breast cancer risk; MAPK1 interacted with DOBS, dietary fiber, folate, and BMI; MAP3K2 interacted with dietary fat; and MAPK14 interacted with dietary folate and BMI. The patterns of association across diet and lifestyle factors with similar biological properties for the same SNPs within genes provide support for associations.
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Affiliation(s)
- Martha L Slattery
- a Department of Medicine , University of Utah , Salt Lake City , Utah , USA
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quốc Lu’o’ng KV, Nguyễn LTH. The roles of beta-adrenergic receptors in tumorigenesis and the possible use of beta-adrenergic blockers for cancer treatment: possible genetic and cell-signaling mechanisms. Cancer Manag Res 2012; 4:431-45. [PMID: 23293538 PMCID: PMC3534394 DOI: 10.2147/cmar.s39153] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Cancer is the leading cause of death in the USA, and the incidence of cancer increases dramatically with age. Beta-adrenergic blockers appear to have a beneficial clinical effect in cancer patients. In this paper, we review the evidence of an association between β-adrenergic blockade and cancer. Genetic studies have provided the opportunity to determine which proteins link β-adrenergic blockade to cancer pathology. In particular, this link involves the major histocompatibility complex class II molecules, the renin-angiotensin system, transcription factor nuclear factor-kappa-light-chain-enhancer of activated B cells, poly(ADP-ribose) polymerase-1, vascular endothelial growth factor, and the reduced form of nicotinamide adenine dinucleotide phosphate oxidase. Beta-adrenergic blockers also exert anticancer effects through non-genomic factors, including matrix metalloproteinase, mitogen-activated protein kinase pathways, prostaglandins, cyclooxygenase-2, oxidative stress, and nitric oxide synthase. In conclusion, β-adrenergic blockade may play a beneficial role in cancer treatment. Additional investigations that examine β-adrenergic blockers as cancer therapeutics are required to further elucidate this role.
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Tanic M, Zajac M, Gómez-López G, Benítez J, Martínez-Delgado B. Integration of BRCA1-mediated miRNA and mRNA profiles reveals microRNA regulation of TRAF2 and NFκB pathway. Breast Cancer Res Treat 2011; 134:41-51. [DOI: 10.1007/s10549-011-1905-4] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2011] [Accepted: 11/29/2011] [Indexed: 12/18/2022]
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Ripple MO, Kalmadi S, Eastman A. Inhibition of either phosphatidylinositol 3-kinase/Akt or the mitogen/extracellular-regulated kinase, MEK/ERK, signaling pathways suppress growth of breast cancer cell lines, but MEK/ERK signaling is critical for cell survival. Breast Cancer Res Treat 2006; 93:177-88. [PMID: 16187238 DOI: 10.1007/s10549-005-4794-6] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The phosphatidylinositol 3-kinase (PI3K)/Akt and mitogen/extracellular signal-regulated kinase (MEK)/extracellular signal-regulated kinase (ERK) signaling pathways are important integrators of growth and survival signals originating from extracellular stimuli. We assessed the importance of these signaling pathways in the growth and survival of 8 breast cell lines (MCF10A, an immortalized line; and 7 cancer cell lines). The cell lines expressed variable levels of both phosphorylated ERK and phosphorylated Akt, but these were unchanged by incubation in serum-free medium. Despite continued activity of these pathways, the cells arrested growth in the absence of serum demonstrating that additional pathways are required for growth. Incubation with the PI3K inhibitor LY294002 suppressed growth of all cell lines, but most remained viable for at least 7-14 days. This long-term survival may be attributable to recovery of phospho-Akt by 24-48 h despite the continued presence of active LY294002, suggesting that alternate pathways may be activating Akt. In contrast, incubation with the MEK inhibitor U0126 not only arrested growth, but also killed all the cell lines within 2-4 days in the absence of serum; the presence of serum only slighted extended viability, except in MCF10A and MDA-MB-468 cells, in which serum provided significantly greater protection. It is likely that these signaling pathways control the level of pro-and anti-apoptotic proteins, yet assessment of Bcl-2 and Bcl-X showed dramatic reduction in level only when large numbers of cells were dead suggesting this may be a consequence rather than cause of death. Overall, the results demonstrate that the MEK/ERK pathway represents the more critical pathway for cell survival of these breast cancer cell lines, and suggest this pathways represents the better target for cancer therapy.
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Affiliation(s)
- Maureen O Ripple
- Department of Pharmacology and Toxicology, Dartmouth Medical School, Dartmouth Hitchcock Medical Center, Lebanon, NH 03756, USA
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Colombara M, Antonini V, Riviera AP, Mainiero F, Strippoli R, Merola M, Fracasso G, Poffe O, Brutti N, Tridente G, Colombatti M, Ramarli D. Constitutive activation of p38 and ERK1/2 MAPKs in epithelial cells of myasthenic thymus leads to IL-6 and RANTES overexpression: effects on survival and migration of peripheral T and B cells. THE JOURNAL OF IMMUNOLOGY 2006; 175:7021-8. [PMID: 16272363 DOI: 10.4049/jimmunol.175.10.7021] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Myasthenia gravis (MG) is an autoimmune disease of neuromuscular junctions where thymus plays a pathogenetic role. Thymectomy benefits patients, and thymic hyperplasia, a lymphoid infiltration of perivascular spaces becoming site of autoantibody production, is recurrently observed. Cytokines and chemokines, produced by thymic epithelium and supporting survival and migration of T and B cells, are likely to be of great relevance in pathogenesis of thymic hyperplasia. In thymic epithelial cell (TEC) cultures derived "in vitro" from normal or hyperplastic age-matched MG thymuses, we demonstrate by gene profiling analysis that MG-TEC basally overexpress genes coding for p38 and ERK1/2 MAPKs and for components of their signaling pathways. Immunoblotting experiments confirmed that p38 and ERK1/2 proteins were overexpressed in MG-TEC and, in addition, constitutively activated. Pharmacological blockage with specific inhibitors confirmed their role in the control of IL-6 and RANTES gene expression. According to our results, IL-6 and RANTES levels were abnormally augmented in MG-TEC, either basally or upon induction by adhesion-related stimuli. The finding that IL-6 and RANTES modulate, respectively, survival and migration of peripheral lymphocytes of myasthenic patients point to MAPK transcriptional and posttranscriptional abnormalities of MG-TEC as a key step in the pathological remodelling of myasthenic thymus.
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Affiliation(s)
- Michaela Colombara
- Section of Immunology, Department of Pathology, University of Verona, Italy
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Tosi L, Rinaldi E, Carinci F, Farina A, Pastore A, Pelucchi S, Cassano L, Evangelisti R, Carinci P, Volinia S. Akt, protein kinase C, and mitogen-activated protein kinase phosphorylation status in head and neck squamous cell carcinoma. Head Neck 2005; 27:130-7. [PMID: 15641106 DOI: 10.1002/hed.20120] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
BACKGROUND To detect epigenetic changes in head and neck squamous cell carcinoma (HNSCC) and between metastatic and nonmetastatic tumors, we performed a systematic phosphorylation screening on different protein kinases. METHODS The phosphorylation levels of the serine-threonine kinase Akt, of mitogen-activated protein kinase (MAPK), and of protein kinase C (PKC) beta and epsilon were measured in a series of 94 biopsy specimens, corresponding to 47 HNSCCs and paired controls taken from clinically uninvolved tissue of the same patients. RESULTS Akt and MAPK were significantly underphosphorylated (two-sided p < .004) in tumors, whereas PKCs showed no differences from control samples.Second, although in control tissue there was a significant correlation between phosphorylation levels of Akt, MAPK, and PKC (all two-sided p < .05), many correlated activations were lost in tumors and even more in lymph node-positive tumors. Finally, p44 MAPK and Akt pThr308 were phosphorylated in a coordinated fashion only in lymph node-positive tumors (two-sided p < .01). CONCLUSIONS This novel evidence documents important changes in the phosphorylation program during cancer progression of HNSCC.
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Affiliation(s)
- Lara Tosi
- Dipartimento di Morfologia ed Embriologia, Università di Ferrara, Fossato di Mortara, 64/b, 44100 Ferrara, Italy
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Esteva FJ, Sahin AA, Smith TL, Yang Y, Pusztai L, Nahta R, Buchholz TA, Buzdar AU, Hortobagyi GN, Bacus SS. Prognostic significance of phosphorylated P38 mitogen-activated protein kinase and HER-2 expression in lymph node-positive breast carcinoma. Cancer 2004; 100:499-506. [PMID: 14745865 DOI: 10.1002/cncr.11940] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
BACKGROUND Chemotherapy-induced p38 mitogen-activated protein kinase (MAPK) phosphorylation reportedly leads to increased apoptosis in breast carcinoma cells. The goals of the current study were to assess the incidence of activated phosphorylated p38 MAPK (P-p38) expression in invasive breast carcinoma, correlate expression of P-p38 MAPK with HER-2, and estimate the prognostic value of this marker in patients with lymph node-positive breast carcinoma treated with adjuvant chemotherapy. METHODS P-p38, HER-2, and Ki-67 were measured using immunohistochemistry (peroxidase method) in 96 patients with lymph node-positive breast carcinoma treated with adjuvant fluorouracil, doxorubicin, and cyclophosphamide chemotherapy. All markers were measured in the primary tumors, before the initiation of adjuvant chemotherapy. The median follow-up period was 11 years after initial cancer surgery. P-p38 MAPK expression was scored visually and quantified using an image analyzer. RESULTS The rate of P-p38 MAPK expression ranged from 19-24%, depending on the scoring system used. There was a trend toward shorter progression-free survival (PFS) for patients whose tumors expressed high levels of P-p38 MAPK, although the difference was not statistically significant (P=0.39). PFS was shorter in patients whose tumors overexpressed P-p38 MAPK and had a high level of Ki-67 (P=0.04). In HER-2-negative patients, P-p38 MAPK overexpression was associated with a shorter PFS (P=0.05). CONCLUSIONS P38 MAPK phosphorylation occurred in 20% of primary breast carcinomas and may be associated with poor outcome in patients with lymph node-positive breast carcinoma. Further studies are needed to define the interaction between P-p38 MAPK and HER-2 expression in breast carcinoma.
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Affiliation(s)
- Francisco J Esteva
- Department of Breast Medical Oncology, The University of Texas M D Anderson Cancer Center, Houston, Texas 77030, USA.
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Wang HY, Cheng Z, Malbon CC. Overexpression of mitogen-activated protein kinase phosphatases MKP1, MKP2 in human breast cancer. Cancer Lett 2003; 191:229-37. [PMID: 12618338 DOI: 10.1016/s0304-3835(02)00612-2] [Citation(s) in RCA: 144] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Expression and activity of c-Jun N-terminal and p38 protein kinases were explored in malignant and non-malignant tissue samples from patients with primary breast cancer. Differential expression was observed for p38 and c-Jun N-terminal protein kinases (JNK) in samples from 14 patients in whom there were sufficient malignant and non-malignant tissue to perform the entire assays. As previously noted, Erk1,2 expression and activity were increased sharply in the malignant tissue. The p38 kinase expression and activity were increased 3-fold in breast cancer. The expression of c-Jun N-terminal protein kinase JNK1, but not JNK2, was increased 2.5-fold in malignant as compared to normal breast tissue. Immunohistochemical analysis in situ with antibodies to JNK1 revealed intense staining in samples of cancerous epithelium. In spite of a 3-fold increase in expression, malignant samples displayed a 35% decrease in the activity of this pro-apoptotic protein kinase. The expression of mitogen and extracellularly-activated protein kinase kinase (MEK)2 and MEK3, upstream protein kinases of Erkl,2 and p38, respectively, was elevated 4- to 5-fold. The upstream regulator of JNK (e.g., MEK4), however, displayed normal levels of expression, providing no basis for the reduction in JNK activity observed for breast cancer. Mitogen-activated protein kinase phosphatases (MKP)1 and MKP2 were assayed and the expression was found to be increased 5-fold and 3-fold, respectively, in malignant as compared to non-malignant samples. The reduced activity of JNK1, in spite of its overexpression, appears to reflect increased MKP activity associated with primary breast cancer. Suppression of MKP activity therapeutically may enable the expression of the pro-apoptotic signals from JNK in malignant cells.
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Affiliation(s)
- Hsien-yu Wang
- Department of Physiology & Biophysics, University Medical Center, SUNY/Stony Brook, Stony Brook, NY 11794-8661, USA.
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Shen Q, Brown PH. Novel agents for the prevention of breast cancer: targeting transcription factors and signal transduction pathways. J Mammary Gland Biol Neoplasia 2003; 8:45-73. [PMID: 14587863 DOI: 10.1023/a:1025783221557] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Transformation of breast cells occurs through loss or mutation of tumor suppressor genes, or activation or amplification of oncogenes, leading to deregulation of signal transduction pathways, abnormal amplification of growth signals, and aberrant expression of genes that ultimately transform the cells into invasive cancer. The goal of cancer preventive therapy, or "chemoprevention," is to eliminate premalignant cells or to block the progression of normal cells into cancer. Multiple alterations in signal pathways and transcription factors are observed in mammary gland tumorigenesis. In particular, estrogen receptor (ER) deregulation plays a critical role in breast cancer development and progress, and targeting ER with selective ER modulators (SERMs) has achieved significant reduction of breast cancer incidence in women at high risk for breast cancer. However, not all breast cancer is prevented by SERMs, because 30-40% of the tumors are ER-negative. Other receptors for retinoids, vitamin D analogs and peroxisome proliferator-activiator, along with transcription factors such as AP-1, NF-kappaB, and STATs (signal transducers and activators of transcription) affect breast tumorigenesis. This is also true for the signal transduction pathways, for example cyclooxygenase 2 (Cox-2), HER2/neu, mitogen-activated protein kinase (MAPK), and PI3K/Akt. Therefore, proteins in pathways that are altered during the process of mammary tumorigenesis may be promising targets of future chemopreventive drugs. Many newly-developed synthetic or natural compounds/agents are now under testing in preclinical studies and clinical trials. Receptor selective retinoids, receptor tyrosine kinase inhibitors (TKIs), SERMs, Cox-2 inhibitors, and others are some of the promising novel agents for the prevention of breast cancer. The chemopreventive activity of these agents and other novel signal transduction inhibitors are discussed in this chapter.
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Affiliation(s)
- Qiang Shen
- Breast Center, Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, Texas, USA
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Yoo J, Park SY, Robinson RA, Kang SJ, Ahn WS, Kang CS. ras Gene mutations and expression of Ras signal transduction mediators in gastric adenocarcinomas. Arch Pathol Lab Med 2002; 126:1096-100. [PMID: 12204060 DOI: 10.5858/2002-126-1096-rgmaeo] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
OBJECTIVE To investigate ras gene alteration in human gastric adenocarcinomas and its potential relationship to ras signal transduction mediators. DESIGN Genomic DNA from 104 gastric tumors were analyzed by sequencing of polymerase chain reaction-amplified products for the presence of ras mutations. All the samples were further investigated with the use of immunohistochemical analysis for ERK1 and ERK2. SETTING Tertiary care teaching hospital. PATIENTS Seventy patients from a Korean population and 34 from a Midwestern US population composed of white Americans and African Americans. RESULTS Fifteen tumors (14%) were positive for either H-ras or K-ras mutation: 9 (13%) of 70 Korean patients and 6 (18%) of 34 US patients. Seven (78%) of the 9 mutated tumors from Korean patients and all 6 (100%) from the US patients were intestinal-type lesions. Either ERK1 and/or ERK2 was overexpressed in 68 samples (65%). No association was established between ras mutations and overexpression of ERK1/2. However, the correlation between ERK1/2 and progression (early vs late) was statistically significant (P =.007). CONCLUSIONS These data suggest that ras mutations are uncommon in gastric adenocarcinomas and that differing racial and/or geographic mechanisms may not underlie ras gene alteration. Most ras mutations were, however, observed in the group of intestinal-type samples, supporting the different genetic mechanisms of carcinogenesis between the intestinal- and diffuse-type tumors. It is noteworthy that enhanced ERK1/2 activity could be one of the characteristics of tumor invasiveness in gastric cancers.
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Affiliation(s)
- Jinyoung Yoo
- Department of Pathology, St Vincent's Hospital, Catholic University, Suwon, Kyungkido, South Korea
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Rahman KMW, Sarkar FH. Steroid hormone mimics: molecular mechanisms of cell growth and apoptosis in normal and malignant mammary epithelial cells. J Steroid Biochem Mol Biol 2002; 80:191-201. [PMID: 11897503 DOI: 10.1016/s0960-0760(01)00186-8] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Anti-estrogen (anti-E2) therapy with E2 receptor antagonists has a significant benefit in women with breast cancer, but it may also increase the risk for developing hormone-independent breast cancer for which there is no therapy similar to that used in hormone-dependent breast cancer. Therefore, there is a significant interest in the development of compounds that may provide therapeutic benefit for hormone-independent breast cancer without untoward risks and adverse effects. The estrogen receptor (ER) modulators with both agonistic as well as antagonistic properties may, thus, be exploited for the development of the next generation of compounds for the prevention and/or treatment of breast cancer. In this article, we have discussed the clinical indications, risks, benefits and mechanisms of action of ER modulators and related compounds, particularly indole-3-carbinol (I3C), which may open new avenues for the prevention and/or treatment of breast cancer.
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Affiliation(s)
- K M Wahidur Rahman
- Department of Pathology, Barbara Ann Karmanos Cancer Institute, Wayne State University School of Medicine, 9374 Scott Hall, 540 E. Canfield Avenue, Detroit, MI 48201, USA
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Haynes MP, Li L, Russell KS, Bender JR. Rapid vascular cell responses to estrogen and membrane receptors. Vascul Pharmacol 2002; 38:99-108. [PMID: 12379956 DOI: 10.1016/s0306-3623(02)00133-7] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
There is a growing interest in the effects of estrogen on the vascular wall, due to the marked gender difference in the incidence of clinically apparent coronary heart disease, when comparing premenopausal women with age-matched males. Estrogen has numerous effects on vascular endothelial and smooth muscle cells, both of which express estrogen receptors (ERs). Although ERs are classically defined as ligand-activated transcription factors, it has become increasingly clear that estrogen-stimulated, ER-dependent cellular responses can be rapid consequences of signal transduction cascades. The cellular localization and molecular form of the ER(s) which mediates rapid signaling are poorly defined. In this review, we describe the mounting evidence for membrane-localized ERs that vary in structure from classical forms. We also discuss ER-catalyzed molecular complex formations and a variety of estrogen-triggered signal transduction cascades, including those involving phosphatidylinositol 3-kinase/Akt, MAP kinase and G-protein-coupled receptors, all of which may induce "protective" profiles in vascular cells.
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Affiliation(s)
- M Page Haynes
- Sections of Cardiovascular Medicine and Immunobiology, Boyer Center for Molecular Medicine, Yale University School of Medicine, New Haven, CT 06536, USA
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Donovan JC, Milic A, Slingerland JM. Constitutive MEK/MAPK activation leads to p27(Kip1) deregulation and antiestrogen resistance in human breast cancer cells. J Biol Chem 2001; 276:40888-95. [PMID: 11527971 DOI: 10.1074/jbc.m106448200] [Citation(s) in RCA: 100] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Antiestrogens, such as the drug tamoxifen, inhibit breast cancer growth by inducing cell cycle arrest. Antiestrogens require action of the cell cycle inhibitor p27(Kip1) to mediate G1 arrest in estrogen receptor-positive breast cancer cells. We report that constitutive activation of the mitogen-activated protein kinase (MAPK) pathway alters p27 phosphorylation, reduces p27 protein levels, reduces the cdk2 inhibitory activity of the remaining p27, and contributes to antiestrogen resistance. In two antiestrogen-resistant cell lines that showed increased MAPK activation, inhibition of the MAPK kinase (MEK) by addition of U0126 changed p27 phosphorylation and restored p27 inhibitory function and sensitivity to antiestrogens. Using antisense p27 oligonucleotides, we demonstrated that this restoration of antiestrogen-mediated cell cycle arrest required p27 function. These data suggest that oncogene-mediated MAPK activation, frequently observed in human breast cancers, contributes to antiestrogen resistance through p27 deregulation.
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Affiliation(s)
- J C Donovan
- Molecular and Cell Biology, Sunnybrook and Women's College Health Science Centre, Toronto, Ontario M4N 3M5, Canada
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