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1.
Free Radic Biol Med ; 50(12): 1771-9, 2011 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-21419216

RESUMO

A high basal expression of manganese superoxide dismutase (MnSOD) has been reported in aggressive breast cancer cells, according to an unknown mechanism, and contributes to their invasive abilities. Here, we report the involvement of Sp1 and nuclear factor-κB (NF-κB) transcription factors in this high basal expression of MnSOD in aggressive breast cancer cells. Suppression or inactivation of Sp1 showed that it plays an essential role in the high MnSOD expression in aggressive breast cancer cells through a unique binding site identified by chromatin immunoprecipitation (ChIP) assay and functional analysis of the MnSOD proximal promoter. Treatment of cells with a specific NF-κB inhibitor peptide decreased significantly high basal MnSOD expression. A ChIP assay showed binding of a constitutive p50/p65 NF-κB complex to the MnSOD intronic enhancer element, associated with hyperacetylation of the H3 histone. Finally, high basal expression of MnSOD resulted in the lack of expression of Damaged DNA binding 2 (DDB2) protein in aggressive breast cancer cells. DDB2 overexpression prevented the binding of Sp1 as well as of NF-κB to their respective elements on the MnSOD gene. These results contribute to a better understanding of MnSOD up-regulation, which may be clinically important in the prediction of breast tumor progression.


Assuntos
Neoplasias da Mama/genética , Proteínas de Ligação a DNA/metabolismo , NF-kappa B/genética , NF-kappa B/metabolismo , Fator de Transcrição Sp1/metabolismo , Superóxido Dismutase/genética , Acetilação , Sequência de Bases , Neoplasias da Mama/metabolismo , Neoplasias da Mama/patologia , Linhagem Celular Tumoral , Elementos Facilitadores Genéticos , Feminino , Radicais Livres , Histonas/genética , Histonas/metabolismo , Humanos , Dados de Sequência Molecular , Regiões Promotoras Genéticas , Estudos Retrospectivos , Fator de Transcrição Sp1/genética , Superóxido Dismutase/biossíntese , Superóxido Dismutase/metabolismo , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , Regulação para Cima
2.
J Biol Chem ; 284(21): 14165-76, 2009 May 22.
Artigo em Inglês | MEDLINE | ID: mdl-19339246

RESUMO

Manganese superoxide dismutase plays a role in breast tumor cell growth, which depends on its constitutive expression. However, the mechanisms responsible for the regulation of constitutive SOD2 gene expression at different malignant phenotype in breast cancers remain to be determined. The present study reports the identification and characterization of a DNA sequence located in the proximal promoter of the SOD2 gene, which forms a complex with a nuclear protein from breast tumor MCF-7 cells. Purification of this complex showed that it contained DDB2 (damaged DNA binding 2), a well known protein involved in nucleotide excision DNA repair and cell cycle regulation. Functional analysis of the proximal promoter of the SOD2 gene or modulation of DDB2 expression allowed us to demonstrate that DDB2 regulates negatively the constitutive expression of the SOD2 gene in breast cancer cells. We demonstrate that the binding of DDB2 was associated with the loss of acetylated H3 histones and the decrease in the binding of Sp1 but not AP-2alpha transcription factors to the SOD2 proximal promoter. In addition, we show that DDB2 exerts, at least in part, a control of breast cancer cell growth through its negative regulation of constitutive expression of the SOD2 gene. For the first time, these data give supporting evidence that DDB2 is a new transcriptional regulator, and they provide insight into the molecular function of breast cancer cell growth, which will have an important clinical interest.


Assuntos
Neoplasias da Mama/enzimologia , Neoplasias da Mama/genética , Proteínas de Ligação a DNA/metabolismo , Regulação Neoplásica da Expressão Gênica , Superóxido Dismutase/genética , Transcrição Genética , Sequência de Bases , Neoplasias da Mama/patologia , Linhagem Celular Tumoral , Proliferação de Células , DNA de Neoplasias/metabolismo , Proteínas de Ligação a DNA/isolamento & purificação , Feminino , Técnicas de Silenciamento de Genes , Histonas/metabolismo , Humanos , Dados de Sequência Molecular , Regiões Promotoras Genéticas/genética , Ligação Proteica , Processamento de Proteína Pós-Traducional , Superóxido Dismutase/metabolismo , Fatores de Transcrição/metabolismo
3.
Breast Cancer Res Treat ; 108(2): 203-15, 2008 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-17473980

RESUMO

Manganese superoxide dismutase (MnSOD) is known to play a role in cancer. MnSOD exerts a tumor suppressive effect in estrogen-dependent human breast cancer cells. In the present study we investigated the in vitro role of MnSOD in the growth of some aggressive and highly metastatic estrogen-independent breast cancer cells, i.e., MDA-MB231 and SKBR3 cells. We show that estrogen-independent cells expressed a significantly higher basal MnSOD level compared to estrogen-dependent human breast cancer cell lines (MCF-7 and T47D). For MDA-MB231 cells, the high-MnSOD level was accompanied by an overproduction of intracellular hydrogen peroxide (H2O2) and by a low expression of the major H2O2-detoxifying enzymes, catalase, and peroxiredoxin 3, compared to MCF-7 cells. Suppression of MnSOD expression by antisense RNA was associated with a decrease of H2O2 content and caused a stimulation of growth with a reduced cell doubling time but induced a decrease of colony formation. Furthermore, treatment of MDA-MB231 cells with H2O2 scavengers markedly reduced tumor cell growth and colony formation. In addition, MnSOD suppression or treatment with H2O2 scavengers reduced the invasive properties of MDA-MB231 cells up to 43%, with a concomitant decrease of metalloproteinase-9 activity. We conclude that MnSOD plays a role in regulating tumor cell growth and invasive properties of estrogen-independent metastatic breast cancer cells. These action are mediated by MnSOD-dependent H2O2 production. In addition, these results suggest that MnSOD up-regulation may be one mechanism that contributes to the development of metastatic breast cancers.


Assuntos
Neoplasias da Mama/enzimologia , Movimento Celular , Proliferação de Células , Superóxido Dismutase/metabolismo , Antioxidantes/farmacologia , Neoplasias da Mama/genética , Neoplasias da Mama/patologia , Catalase/metabolismo , Linhagem Celular Tumoral , Movimento Celular/efeitos dos fármacos , Proliferação de Células/efeitos dos fármacos , Regulação para Baixo , Estrogênios/metabolismo , Feminino , Regulação Enzimológica da Expressão Gênica , Regulação Neoplásica da Expressão Gênica , Humanos , Peróxido de Hidrogênio/metabolismo , Metaloproteinase 9 da Matriz/metabolismo , Invasividade Neoplásica , Peroxirredoxina III , Peroxirredoxinas/metabolismo , RNA Antissenso/metabolismo , Superóxido Dismutase/genética , Fatores de Tempo , Transfecção
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