RESUMO
Erythropoietin (EPO) stimulates the growth of erythroblasts in the bone marrow (C. Lacombe and P. Mayeux, NEPHROL: DIAL: TRANSPLANT:, 14 (SUPPL: 2): 22-28, 1999). We report basal and hypoxia-stimulated expression of EPO and its receptor, EPOR, in human breast cancer cells, and we demonstrate EPO-stimulated tyrosine phosphorylation and the proliferation of these cells in vitro. In 50 clinical specimens of breast carcinoma, we report high levels of EPO and EPOR associated with malignant cells and tumor vasculature but not with normal breast, benign papilloma, or fibrocystic tissue. Hypoxic tumor regions display the highest levels of EPO and EPOR expression. Enhanced EPO signaling may contribute to the promotion of human cancer by tissue hypoxia.
Assuntos
Neoplasias da Mama/metabolismo , Eritropoetina/biossíntese , Receptores da Eritropoetina/biossíntese , Biópsia , Western Blotting , Neoplasias da Mama/genética , Neoplasias da Mama/patologia , Eritropoetina/genética , Expressão Gênica , Humanos , Imuno-Histoquímica , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Receptores da Eritropoetina/genética , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Células Tumorais CultivadasRESUMO
The cytokine ciliary neurotrophic factor (CNTF) and transforming growth factor-beta (TGF-beta) both induce transcription of the vasoactive intestinal peptide (VIP) gene through a 180-base pair cytokine response element (CyRE) in the VIP promoter. While CNTF induces STAT and AP-1 proteins to bind to cognate sites in the VIP CyRE, the mechanism through which TGF-beta acts to induce VIP gene transcription is not known. Here we show that Smad3 and Smad4 proteins can bind to two distinct sites within the VIP CyRE. These sites are absolutely required for the induction of VIP CyRE transcription by TGF-beta. TGF-beta induces endogenous Smad-containing complexes to bind to these sites in human neuroblastoma cells. CNTF and TGF-beta synergize to induce VIP mRNA expression and transcription through the VIP CyRE. This synergy is dependent on the Smad, STAT, and AP-1 sites, suggesting that these two independent cytokine pathways synergize through the cooperation of pathway-specific transcription factors binding to distinct sites within the VIP CyRE.
Assuntos
Fator Neurotrófico Ciliar/fisiologia , Regulação da Expressão Gênica/fisiologia , Fatores de Transcrição/fisiologia , Transcrição Gênica/fisiologia , Fator de Crescimento Transformador beta/fisiologia , Peptídeo Intestinal Vasoativo/genética , Animais , Sequência de Bases , Linhagem Celular , Primers do DNARESUMO
Activin, a member of the transforming growth factor-beta superfamily, can regulate neuropeptide gene expression in the nervous system and in neuroblastoma cells. Among the neuropeptide genes whose expression can be regulated by activin is the gene encoding the neuropeptide vasoactive intestinal peptide (VIP). To investigate the molecular mechanisms by which activin regulates neuronal gene expression, we have examined activin's regulation of VIP gene expression in NBFL neuroblastoma cells. We report here that NBFL cells respond to activin by increasing expression of VIP mRNA. Activin regulates VIP gene transcription in NBFL cells through a 180-bp element in the VIP promoter that was previously characterized to be necessary and sufficient to mediate the induction of VIP by the neuropoietic cytokines and termed the cytokine response element (CyRE). We find that the VIP CyRE is necessary and sufficient to mediate the transcriptional response to activin. In addition, ciliary neurotrophic factor (CNTF), a neuropoietic cytokine, synergizes with activin to increase VIP mRNA expression and transcription through the VIP CyRE. Mutations in either the Stat (signal transducer and activator of transcription) or AP-1 sites within the CyRE that reduce the response to CNTF, also reduce the response to activin. However, mutating both the Stat and AP-1 sites within the wild-type CyRE, while reducing the separate responses to either activin or CNTF, eliminates the synergy between them. These data suggest that activin and CNTF, two factors that appear to signal though distinct pathways, activate VIP gene transcription through a common transcriptional element, the VIP CyRE.
Assuntos
Fator Neurotrófico Ciliar/farmacologia , Regulação da Expressão Gênica/efeitos dos fármacos , Inibinas/farmacologia , Sequências Reguladoras de Ácido Nucleico , Transdução de Sinais/efeitos dos fármacos , Peptídeo Intestinal Vasoativo/biossíntese , Ativinas , Animais , Sítios de Ligação/genética , Galinhas , Proteínas de Ligação a DNA/metabolismo , Sinergismo Farmacológico , Humanos , Mutação , Proteínas de Neoplasias/biossíntese , Proteínas de Neoplasias/genética , Neuroblastoma/metabolismo , Neuroblastoma/patologia , Regiões Promotoras Genéticas , Proteínas Recombinantes de Fusão/biossíntese , Fator de Transcrição STAT1 , Transativadores/metabolismo , Fator de Transcrição AP-1/metabolismo , Transfecção , Fator de Crescimento Transformador beta/farmacologia , Células Tumorais Cultivadas/efeitos dos fármacos , Peptídeo Intestinal Vasoativo/genéticaRESUMO
Eighteen men aged 18 to 32 with rapidly progressive male pattern baldness had serum dehydroepiandrosterone sulfate and testosterone measured. Dehydroepiandrosterone sulfate levels were elevated in all patients, ranging from 340 to 730 micrograms/dl. The patients were otherwise healthy and serum testosterone levels were within normal limits. A control group of men of similar age without hair loss had lower dehydroepiandrosterone sulfate levels ranging from 124 to 300 micrograms/dl (p less than 0.005). The biochemistry of androgens, particularly dehydroepiandrosterone sulfate, suggests that adrenal hyperactivity may initiate alopecia in young men who are genetically susceptible.