Down-regulation of C/EBPalpha in breast cancer cells by hypoxia-estrogen combination is mainly due to hypoxia.
CCAAT/enhancer binding protein-alpha (C/EBPalpha) is involved in the control of cell differentiation and proliferation. It has been previously shown that hypoxia (H) down-regulates C/EBPalpha in breast cancer cells; here the effect of estrogen (E(2)) during H on C/EBPalpha in T-47D cell line was examined. By quantitative RT-PCR the C/EBPalpha mRNA stability was analyzed at 21% O(2) and 1% O(2) under E(2). The H-E(2) combination but not E(2) alone reduced the half-life of the C/EBPalpha mRNA. C/EBPalpha promoter activity studies covering -576 bp do not show any effect of E(2); a significant decrease of C/EBPalpha transcriptional activity was found in the C/EBPalpha promoter between -576/416 bp as previously observed when cells were treated with hypoxia alone. By immunocytochemistry, H-E(2) combination alters the cellular distribution of C/EBPalpha in T-47D cells and locates this protein mainly at the cytosol. Therefore, the observed down-regulation of C/EBPalpha by the H-E(2) combination in T-47D cells is mainly due to the hypoxia effect.
INSERM U747, Universite Paris Descartes, Paris, France.
Ramzi
R
Seifeddine
Marie-Claude
MC
Fulchignoni-Lataud
Liliane
L
Massaad-Massade
D001943:Breast Neoplasms / Q000235:genetics* / Q000473:pathology; D022762:CCAAT-Enhancer-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D015536:Down-Regulation; D004967:Estrogens / Q000494:pharmacology*; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D006207:Half-Life; D006801:Humans; D000860:Hypoxia / Q000235:genetics*; D007124:Immunoenzyme Techniques; D011401:Promoter Regions, Genetic / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015533:Transcriptional Activation; D014407:Tumor Cells, Cultured
D022762:CCAAT-Enhancer-Binding Proteins; C515848:CEBPA protein, human; D004967:Estrogens; D012333:RNA, Messenger