Expression Of Proto-oncogene C-fos Research Articles

C-FOS Expression Analysis in Pterygia Cell Spot Arrays.

Mechanisms of c-FOS activation in the onset and progression of pterygia remain under investigation. This study aimed to comparatively analyze c-FOS proto-oncogene expression levels in neoplastic pterygia and normal epithelia. We used a liquid-based cytology assay on thirty (n=30) pterygia cell populations and normal epithelia (n=10) extracted by a smooth scraping of conjunctiva epithelia. Applying a cell spot-based technique, we constructed five (n=5) slides, each containing eight (n=8) cell spots. A modified immune-cytochemistry (ICC) assay for c-FOS protein was used. Additionally, digital image analysis was implemented to calculate c-FOS immunostaining intensity levels. High staining intensity levels of c-FOS were detected in 12/30 (40%), whereas the rest 18/30 (60%) demonstrated moderate expression. c-FOS levels were statistically significantly higher in the pterygia compared to control tissues (p=0.001). c-FOS levels in the pterygia were not associated with the sex of patients (p=0.678), the presence of recurrent lesion (p=0.390) or the location of the lesion (p=0.158). The levels of c-FOS, however, were marginally significantly affected by the morphology of the pterygia (p=0.005). More precisely, the c-FOS levels were significantly higher in pterygia with a fleshy morphology. c-FOS over-expression is observed frequently in pterygia. It seems to be critically involved in the molecular mechanism of the lesion by its over-expression affecting partially their morphological features. Cell spot liquid - based array analysis is an innovative, easy to implement technique for simultaneously evaluating a broad spectrum of molecules in multiple specimens on the same slide.

The Effect of Alpha-Tocopherol on Morphine Tolerance-induced Expression of c-fos Proto-oncogene from a Biotechnological Perspective.

The increase of oxidant compounds is the most well-known reasons for the tolerance to the analgesic properties of Morphine. Additionally, the production of proxy-nitrite impairs receptors, proteins and enzymes involved in the signaling pathways of analgesia, apoptosis and necrosis. Also, we revised all patents relating to opioid tolerance control methods. The aim of this study was to assess the effects of Alpha-tocopherol as an anti-oxidant agent to reduce Morphine tolerance. Forty male rats randomly divided into four groups. 10 mg/kg of morphine was injected subcutaneously to create the desired level of tolerance. After modeling, 70 mg/kg Alpha- Tocopherol was injected intraperitoneal. Also, the hot plate recorded pain threshold alterations was used to evaluate the behavioral test. All tissue samples were extracted from the spinal cord, thalamus and frontal cortex for molecular and gene expression evaluations. Also, the effect of Alpha- Tocopherol on the apoptosis and necrosis parameters was analyzed using nissl staining and tunel test. The time latency results showed that there were no significant differences in the different days in groups treated with Morphine plus Alpha-Tocopherol. However, our data highlighted that the pain threshold and their time latency in respond to it had substantially increased in comparison with the control group. Furthermore, we found that the Alpha-Tocopherol obviously decreased c-fos gene expression, especially in the spinal cord. Thus, co-administration of Alpha-Tocopherol with Morphine can decrease the adverse effects of nitrite proxy, which is released due to repeated injections of Morphine.

Differential Expression of c-fos Proto-Oncogene in Normal Oral Mucosa versus Squamous Cell Carcinoma

Background:The c-Fos nuclear protein dimerizes with Jun family proteins to form the transcription factor AP-1 complex which participates in signal transduction and regulation of normal cellular processes. In tumorigenesis, c-Fos promotes invasive growth through down-regulation of tumor suppressor genes but its role in oral carcinogenesis is not clear.Objectives:This study concerned c-fos gene expression in normal and malignant tissues of the oral cavity, with attention to associations between expression status and clinico-pathological profiles of OSCC patients.Method:A total of 65 histopathologically confirmed OSCC tissue samples were included in case group along with an equal number of age and sex-matched normal tissue samples of oral cavity for the control group. c-Fos protein and m-RNA expressions were analyzed using immunohistochemistry and qRT-PCR, respectively.Results:A significant low expression of c-Fos protein was observed in OSCC cases than normal control subjects (p= <0.001). The mean percent positivity of c-Fos protein in cases vs. controls was 24.91± 2.7 vs. 49.68± 2.2 (p= <0.001). Most OSCC tissue samples showed weak or moderate c-Fos expression whereas 53.8% of normal tissue sections presented with strong immunostaining. Moreover, the relative m-RNA expression for the c-fos gene was significantly decreased in case group (0.93± 0.48) as compared to the control group (1.22± 0.87). Majority of c-Fos positive cases were diagnosed with well developed tumor. The mean percent positivity of c-Fos protein was significantly lower in higher grade tumor as compared with normal oral mucosa (p= < 0.001).Conclusion:The present study suggested that the c-fos gene is downregulated in oral carcinomas. The disparity of c-Fos protein levels in different pathological grades of tumor and normal oral tissue samples may indicate that loss of c-Fos expression is related with the progression of OSCC.

Cyclin-dependent kinase 12 increases 3' end processing of growth factor-induced c-FOS transcripts.

Transcriptional cyclin-dependent kinases (CDKs) regulate RNA polymerase II initiation and elongation as well as cotranscriptional mRNA processing. In this report, we describe an important role for CDK12 in the epidermal growth factor (EGF)-induced c-FOS proto-oncogene expression in mammalian cells. This kinase was found in the exon junction complexes (EJC) together with SR proteins and was thus recruited to RNA polymerase II. In cells depleted of CDK12 or eukaryotic translation initiation factor 4A3 (eIF4A3) from the EJC, EGF induced fewer c-FOS transcripts. In these cells, phosphorylation of serines at position 2 in the C-terminal domain (CTD) of RNA polymerase II, as well as levels of cleavage-stimulating factor 64 (Cstf64) and 73-kDa subunit of cleavage and polyadenylation specificity factor (CPSF73), was reduced at the c-FOS gene. These effects impaired 3' end processing of c-FOS transcripts. Mutant CDK12 proteins lacking their Arg-Ser-rich (RS) domain or just the RS domain alone acted as dominant negative proteins. Thus, CDK12 plays an important role in cotranscriptional processing of c-FOS transcripts.

McCune Albright syndrome

Inheritance MAS is not inherited. It is a sporadic genetic disorder, caused by a mutation in the GNAS gene encoding the alpha subunit of the stimulatory G protein (GSalpha), cyclic AMP protein kinase dependent cellular signaling pathway involving G protein coupled receptors. An arginine or occasionally serine, leucine or glycine to histidine transposition at residue 201 attenuates GTpase activity. This results in constitutive activation of adenylyl cyclase. The somatic mutation occurs in early embryogenesis, resulting in widespread tissue distribution of abnormalities. The post zygotic mutation is responsible for the mosaic pattern of tissue distribution and the extreme variability of clinical changes, varying from multi system disease to almost unrecognized disorders with single organ involvement. Increased adenylate cyclase activity in bone from clinical fibrous dysplastic lesions is caused by expression of Cfos proto-oncogene in bone. Recent identification of increased fibroblast growth factor (FGF23) activity in fibrous dysplastic lesions has linked the bony abnormalities to a recognized marker of bone metabolism.

Effects of isorhynchophylline on angiotensin II-induced proliferation in rat vascular smooth muscle cells

Abstract Proliferation of vascular smooth muscle cells (VSMCs) is a crucial event in cardiovascular diseases. Isorhynchophylline, an alkaloid from a traditional Chinese medicine Gambirplant, has been used to treat cardiovascular diseases. The aim of this study was to investigate the effects of isorhynchophylline on angiotensin II (Ang II)-induced proliferation of rat VSMCs. VSMCs were isolated from rat artery and cultured for 14 days before experimentation. The effect of isorhynchophylline on Ang II-induced proliferation was evaluated by cell number, MTT assay and flow cytometry, and nitric oxide (NO) content and activity of NO synthase (NOS) were measured. The expression of proto-oncogene c-fos, osteopontin (OPN) and proliferating cell nuclear antigen (PCNA) mRNAs was measured by real-time RT-PCR. VSMC cultures were verified by morphology and immunostaining with α-smooth muscle actin. Isorhynchophylline (0.1–10.0 μM) was not toxic to VSMCs, but markedly decreased Ang II (1.0 μm)-enhanced cell number and MTT intensity, and blocked cell transition from G0/G1 to S phase. Furthermore, isorhynchophylline increased the NO content and NOS activity, and suppressed Ang II-induced over-expression of c-fos, OPN and PCNA. Thus, isorhynchophylline was effective against Ang-II induced cell proliferation, an effect that appears to be due, at least in part, to increased NO production, regulation of the cell cycle, and depressed expression of c-fos, OPN and PCNA related to VMSC proliferation.

Influence of aflatoxin B1 on mRNA levels of acute-phase proteins and oncoproteins in albino rat liver

Background: The effect of aflatoxin B1 (AFB1) administration on expression of genes coding for acute-phase proteins, and nuclear protooncogenes c-fos and c-jun, and alpha-fetoprotein gene has been studied in rats. Methods: AFB1 was administered to male Albino Oxford (AO) rats as a single intraperitoneal dose (1 mg/kg body weight). The expression of genes for albumin, cystein protease inhibitor, fibrinogen, haptoglobin, a1-acid glycoprotein and for c-Fos, c-Jun and alpha-fetoprotein in rat liver was measured by Northern hybridization. Results: The mild increase in the levels of mRNA for acute-phase proteins after AFB1 administration was observed during the first 24 hours. The exceptions were the mRNA levels in liver for cystein protease inhibitor, which were 50%, decreased as compared to the control values. In addition, mild increase of the expression of c-fos protooncogene with two peaks were noted at three (1.3 fold) and 72 hours (1.5 fold) after injection AFB1 to rats. The expression of nuclear protooncogene c-jun at 1 hour and 72 hour after acute poisoning was 2.6 fold and 3.7 fold increased as compared to control values, respectively. The mRNA levels in liver for the alpha-fetoprotein reached a maximum at 1 hour after AFB1 injection and it was 1.8 times higher than the levels in the livers of nontreated animals. Conclusion: Single administration of AFB1 induced increased transcription of c-jun and c-fos genes while typical acute-phase response was not found.

Effects of isorhynchophylline on angiotensin II-induced proliferation in rat vascular smooth muscle cells

Proliferation of vascular smooth muscle cells (VSMCs) is a crucial event in cardiovascular diseases. Isorhynchophylline, an alkaloid from a traditional Chinese medicine Gambirplant, has been used to treat cardiovascular diseases. The aim of this study was to investigate the effects of isorhynchophylline on angiotensin II (Ang II)-induced proliferation of rat VSMCs. VSMCs were isolated from rat artery and cultured for 14 days before experimentation. The effect of isorhynchophylline on Ang II-induced proliferation was evaluated by cell number, MTT assay and flow cytometry, and nitric oxide (NO) content and activity of NO synthase (NOS) were measured. The expression of proto-oncogene c-fos, osteopontin (OPN) and proliferating cell nuclear antigen (PCNA) mRNAs was measured by real-time RT-PCR. VSMC cultures were verified by morphology and immunostaining with alpha-smooth muscle actin. Isorhynchophylline (0.1-10.0 microM) was not toxic to VSMCs, but markedly decreased Ang II (1.0 microM)-enhanced cell number and MTT intensity, and blocked cell transition from G(0)/G(1) to S phase. Furthermore, isorhynchophylline increased the NO content and NOS activity, and suppressed Ang II-induced over-expression of c-fos, OPN and PCNA. Thus, isorhynchophylline was effective against Ang-II induced cell proliferation, an effect that appears to be due, at least in part, to increased NO production, regulation of the cell cycle, and depressed expression of c-fos, OPN and PCNA related to VMSC proliferation.

Abdominal Radiation Initiates Apoptotic Mechanism in Rat Femur Bone Marrow Cells in vivo that is Reversed by IGF-1 Administration

Radiation induces apoptosis as a result of damage to cellular DNA and RNA. The aim of our work was to study the effect of radiation on rat bone marrow cells (as a neighboring tissue) in the context of a model of experimental radiation enteritis in rats. The effect of systematic administration in irradiated animals of r-IGF-1 and GH was also studied. Wistar type, normal rats, were divided in 4 groups. One control group and the other 3 groups were irradiated in the abdomen. The measured scattered irradiation in the femur ranged from 16.5 to 47.3 cGy. In 2 groups of irradiated animals, rIGF-1 (0.1 microg/g of body weight twice/d) and rGH (0.25 microg/g of body weight /d) were administered. Bone marrow cells were harvested from both femurs. DNA and RNA were analyzed in specific gels. The m-RNA was hybridized for c-fos proto-oncogene expression. The calculated low dose of radiation that affected the femurs of the animals induced reduction in bone marrow cell numbers and endonuclease activation manifested by subsequent fragmentation of DNA and RNA. This phenomenon was reversed by rGH and rIGF-1 administration. The c-fos proto-oncogene expression was upregulated by irradiation. These observations indicate that scattered low dose radiation is capable of initiating apoptosis in rat bone marrow cells and rGH and rIGF-1 administration reverse this process.

17β-Estradiol rapidly stimulates c-fos expression via the MAPK pathway in T84 cells

In this study, we show that 17β-Estradiol (E2) induced the proliferation of T84 colonic carcinoma cells. We, further, investigated the mechanisms underlying this proliferation and show that E2 induced c-fos protooncogene expression in T84 cells in a timescale consistent with a rapid non-genomic action of the hormone. Furthermore, E2 rapidly phosphorylated both CREB and ELK1, transcription factors that bind to the c-fos promoter and stimulate transcription. Pretreatment with PD98059 and H89, mitogen-activated protein kinase (MAPK) pathway and protein kinase A (PKA) inhibitors, respectively showed that phosphorylation of CREB and ELK1 and subsequent c-fos induction was mediated by the MAPK pathway only. Finally, the estrogen receptor (ER) antagonist, ICI 182,780, blocked the activation of MAPK pathway, subsequent CREB and ELK1 phosphorylation and c-fos induction in T84 cells suggesting an ER dependent mechanism. Consistent with this finding, ICI 182,780 caused a substantial reduction in the proliferative effects of E2 on T84 cells.

The G Protein-coupled Receptor GPR30 Mediates c-fos Up-regulation by 17β-Estradiol and Phytoestrogens in Breast Cancer Cells

A growing body of evidence concerning estrogen effects cannot be explained by the classic model of hormone action, which involves the binding to estrogen receptors (ERs) alpha and ERbeta and the interaction of the steroid-receptor complex with specific DNA sequences associated with target genes. Using c-fos proto-oncogene expression as an early molecular sensor of estrogen action in ERalpha-positive MCF7 and ER-negative SKBR3 breast cancer cells, we have discovered that 17beta-estradiol (E2), and the two major phytoestrogens, genistein and quercetin, stimulate c-fos expression through ERalpha as well as through an ER-independent manner via the G protein-coupled receptor homologue GPR30. The c-fos response is repressed in GPR30-expressing SKBR3 cells transfected with an antisense oligonucleotide against GPR30 and reconstituted in GPR30-deficient MDA-MB 231 and BT-20 breast cancer cells transfected with a GPR30 expression vector. GPR30-dependent activation of ERK1/2 by E2 and phytoestrogens occurs via a Gbetagamma-associated pertussis toxin-sensitive pathway that requires both Src-related and EGF receptor tyrosine kinase activities. The ability of E2 and phytoestrogens to regulate the expression of growth-related genes such as c-fos even in the absence of ER has interesting implications for understanding breast cancer progression.

인삼 총 사포닌의 에스트로젠, 안드로젠, 레티노익산 호르몬 수용체에 대한 활성

Alternative or complementary medicine plays an important role in health care system. Ginseng, being one of the most popular oriental herbs, is believed to contain various steroid hormone activity. Ginseng has been demonstrated pharmacological effect in the cardiovascular, endocrine, central nervous, and immune system. Our objective was to study that total saponin might mediate some of their actions by binding to the steroid hormone receptor, as they share many of the actions of steroid hormone in various physiological system. Using total saponin from Panax Ginseng, we have studied the possibility of total saponin being a potential estrogen receptor, androgen receptor, and retinoic acid receptor ligand. Total saponin activated the transcription of both the estrogen and androgen responsive luciferase reporter plasmids at a concentration of 100<TEX>$\mu\textrm{g}$</TEX>/ml in COS cells transiently transfected with the corresponding receptor and hormone responsive receptor plasmids. And total saponin caused a concentration-dependent stimulation of estrogen receptor. Total saponin increased the expression of estrogen responsive c-fos proto-oncogene at the protein level in MCF7 cells at 24 h treatment as examined by Western analysis. The c-fos induction was used as a specific marker of estrogen responsiveness. This activation was inhibited by the specific estrogen receptor antagonist, ICI 182,780. However, total saponin failed to activate the retinoic acid receptor in COS cells transiently transfected with the corresponding receptor and retinoic acid responsive reporter plasmids. These results show that total saponin is capable of activating estrogen and androgen receptors.

Binding of Adenovirus to Its Receptors in Mouse Astrocytes Induces c-fos Proto-Oncogene and Apoptosis

We have demonstrated that Ad.βGal, a broadly used adenoviral vector of serotype 5, binds and induces proto-oncogene c-fos expression in quiescent cultures of mouse brain astrocytes. As observed in Northern blots, the expression of this immediate early gene is induced by viral infection in a dose-dependent manner, peaking at a multiplicity of infection (m.o.i.) of 100. The expression of c-fos is transient, being maximal after 30 min and disappearing 2 h after infection. A previously reported method was used to study the presence of receptors for adenovirus in the cellular membrane of murine astrocytes. After absorption of the virus, rabbit antibodies and 125I-protein A were used to form a sandwich on the cellular surface, and 9000 adenovirus-specific receptors were demonstrated on each astrocytic cell. Binding was temperature dependent and reached a plateau after 60 min. The specificity of c-fos induction is demonstrated by its neutralization by anti-adenovirus-specific antibodies. Although clear apoptosis cannot be demonstrated in vitro by DNA laddering, maybe due to a lack of sensitivity of the method, a statistically significant increase in caspase-3 activity is demonstrated in astrocyte cultures infected at a m.o.i. of 100 by adenovirus. Furthermore, a perfect colocalization is shown in vivo between cells infected with the Ad.βGal vector and apoptotic astrocytes, as demonstrated by TdT-mediated dUTP nick end labeling (TUNEL) staining. The purpose of our study was to ascertain the potential for adenovirus as a gene therapy vector for neural disorders caused by astrocyte dysfunctions.

Fos and nitric oxide synthase in rat brain with chronic mesostriatal dopamine deficiency: effects of nitroglycerin and hypoxia

We found sustained proto-oncogene c-fos expression in neurons of the lateral and medial neostriatum and suppression of this expression in nitric oxide synthase (NOS)-containing cells within the islands of Calleja after lesions of the dopaminergic mesostriatal system induced by 6-hydroxydopamine. Systemic administration of nitroglycerin (NTG) or mild hypoxia resulted in a decreased of c-fos expression in the dorsolateral part of the denervated neostriatum. However, in other brain structures NTG or mild hypoxia evoked sustained c-fos expression in NOS-containing neurons and in the sources catecholaminergic projections involved in the control of cardiovascular function. We propose that the administration of NTG, an NO donor, or hypoxia partially attenuate the consequences of an excessively increased glutamate level in the denervated neostriatum which are manifest in high level of c-fos expression.

Transgenic Mouse Models To Determine the Role of Epidermal Growth Factor Receptor in Epithelial Cell Proliferation, Apoptosis, and Asbestosis

Cell proliferation by asbestos fibers is a consequence of early asbestos-induced injury to pulmonary epithelial and mesothelial cells and may be critical to the development of fibroproliferative diseases.1,2 In mesothelial and alveolar type II epithelial cells, epidermal growth factor (EGF) and crocidolite asbestos are potent mitogens. Asbestos fibers cause aggregation of the EGF receptor (EGFR)3 and increased levels of EGFR steady-state messenger RNA and protein.4 Phosphorylation of the EGFR by asbestos fibers is causally related to increased phosphorylation and activity of extracellular signal-regulated protein kinases (ERKs) 1 and 2 and c-fos protooncogene expression.

Estrogen Receptor-mediated Activation of the Serum Response Element in MCF-7 Cells through MAPK-dependent Phosphorylation of Elk-1

17beta-Estradiol (E2) induces c-fos protooncogene expression in MCF-7 human breast cancer cells, and deletion analysis of the c-fos promoter showed that the serum response element (SRE) at -325 to -296 was E2-responsive. The mechanism of ligand-activated estrogen receptor alpha (ERalpha)-dependent activation of gene expression through the SRE was determined by mutational analysis of the promoter, analysis of mitogen-activated protein kinase (MAPK) pathway activation by E2, and transforming growth factor alpha (TGF-alpha) as a positive control. In addition, ERalpha-negative MDA-MB-231 breast cancer and Chinese hamster ovary cells were used as reference cell lines. The results showed that transcriptional activation of the SRE by E2 was due to ERalpha activation of the MAPK pathway and increased binding of the serum response factor and Elk-1 to the SRE. Subsequent studies with dominant negative Elk-1, wild type, and variant GAL4-Elk-1 fusion proteins confirmed that phosphorylation of Elk-1 at serines 383 and 389 in the C-terminal region of Elk-1 is an important downstream target associated with activation of an SRE by E2. Both E2 (ERalpha-dependent) and growth factors (ERalpha-independent) activated the SRE in breast cancer cells via the Ras/MAPK pathway; however, in ER-negative CHO cells that do not express a receptor for TGF-alpha, only hormone-induced activation was observed in cells transfected with ERalpha.

Specific inhibition of c-fos proto-oncogene expression by triple-helix-forming oligonucleotides.

The promoter region of the c-fos oncogene 5' flanking sequence contains enhancer elements crucial for binding nuclear factors that regulate transcription following cell proliferation and differentiation. Single-stranded deoxyoligonucleotides were chosen for modulation of c-fos protooncogene expression because of their high-affinity binding to specific nucleotide sequences. We designed two oligonucleotides that form a triple-helix complex on the retinoblastoma gene product-responsible element of the c-fos oncogene. Modification of the DNA triplex with dimethyl sulfate and affinity cleaving assays demonstrate that the predicted oligonucleotides form a DNA triplex structure with the c-fos promoter in a sequence-specific manner. Tumorigenic and non-tumorigenic fibroblasts were transiently transfected with fos-CAT plasmid modified with alkylating triplex-forming oligonucleotide reagents. A dramatic depression of CAT activity was found when the cross-linked triple helix complex at the retinoblastoma gene product-related site of the c-fos promoter was used. These experiments suggest that transcription of individual genes can be selectively modulated in cell culture by sequence specific triplex formation in regulatory enhancer sequences.

Renal c-fos expression induced by angiotensin II is enhanced in spontaneously hypertensive rats

We compared the effect of a bolus injection of angiotensin II (Ang II) on the expression of protooncogene c-fos in the renal cortex and medulla of spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats. Intravenous infusion of 5 ng kg body weight of Ang II resulted in an immediate rise in systolic blood pressure (SBP) in both SHR and WKY rats. The percent rise in SBP was similar in both strains. Pretreatment with Ang II type 1 (AT1)-receptor antagonist, L-158, 809 (1 mg kg ) abolished the presser response in both strains. Competitive reverse transcription-polymerase chain reaction (RT-PCR) showed that administration of Ang II increased the expression of c-fos mRNA within 10 min in both the renal cortex and medulla of SHR significantly higher than WKY rats. Moreover, the enhanced c-fos mRNA expression due to Ang II was significantly suppressed by the pretreatment of L-158, 809 in both strains. These findings indicate that c-fos expression in the kidney is mediated by AT1-receptors and that the renal c-fos response to exogenous Ang II was significantly augmented in SHR compared with WKY rats, suggesting that this hyperresponsiveness on renal AT1-action may partly contribute to the progression of renal injury in SHR.

Estrogen-induced c-fos protooncogene expression in MCF-7 human breast cancer cells: role of estrogen receptor Sp1 complex formation.

17Beta-estradiol (E2) induces c-fos protooncogene expression in MCF-7 human breast cancer cells, and previous studies in HeLa cells identified an imperfect palindromic estrogen-responsive element (-1212 to -1200) that was required for trans-activation. In contrast, the estrogen-responsive element was not required for E2 responsiveness in MCF-7 cells, and using a series of constructs containing wild-type (pF1) and mutant 5'-flanking sequences (-1220 to -1155) from the c-fos protooncogene promoter in transient transfection assays, it was shown that a GC-rich motif (5'-GGGGCGTGG) containing an imperfect Sp1-binding site was required for hormone-induced activity. This sequence also bound Sp1 protein in gel mobility shift assays, and coincubation with the estrogen receptor (ER) enhanced Sp1-DNA binding. E2 and 4'-hydroxytamoxifen, but not ICI 164,384, induced reporter gene activity in cells transiently transfected with pF1. E2 induced reporter gene activity in MDA-MB-231 breast cancer cells transiently cotransfected with pF1 and wild-type ER or variant ER in which the DNA-binding domain was deleted (HE11); plasmids expressing N-terminal or C-terminal domains of the ER containing activator function-1 or -2, respectively, were inactive in these assays. In contrast, only wild-type ER mediated 4'-hydroxytamoxifen-induced activity. Induction of c-fos protooncogene expression by E2 in MCF-7 cells is dependent on the formation of a transcriptionally active ER/Sp1 complex that binds to a GC-rich enhancer element.

Estrogen-Induced c-fos Protooncogene Expression in MCF-7 Human Breast Cancer Cells: Role of Estrogen Receptor Sp1 Complex Formation

Estrogen-Induced c-fos Protooncogene Expression in MCF-7 Human Breast Cancer Cells: Role of Estrogen Receptor Sp1 Complex Formation