Tamoxifen induction of CCAAT enhancer-binding protein alpha is required for tamoxifen-induced apoptosis
| Autor: | Jingwei Cheng, David V. Yu, Jian Hua Zhou, David J. Shapiro |
|---|---|
| Rok vydání: | 2007 |
| Předmět: |
Small interfering RNA
genetic structures Apoptosis Biology Biochemistry HeLa RNA interference CCAAT-Enhancer-Binding Protein-alpha Humans RNA Small Interfering Molecular Biology Etoposide Oligonucleotide Array Sequence Analysis Gene knockdown Ccaat-enhancer-binding proteins Gene Expression Profiling Estrogen Antagonists Estrogen Receptor alpha Cell Biology biology.organism_classification Molecular biology Antineoplastic Agents Phytogenic eye diseases Tamoxifen Gene Expression Regulation Cancer cell Mutation Estrogen receptor alpha hormones hormone substitutes and hormone antagonists HeLa Cells |
| Zdroj: | The Journal of biological chemistry. 282(42) |
| ISSN: | 0021-9258 |
| Popis: | Low concentrations of tamoxifen or its active metabolite 4-hydroxytamoxifen (OHT) induce estrogen receptor alpha (ERalpha)-dependent apoptosis. To analyze the pathway of OHT-ERalpha-induced apoptosis, we developed stably transfected lines of HeLa cells expressing wild-type ER and an inactive mutant ERalpha unable to bind estrogen response elements. HeLa cells expressing the mutant ERalpha and HeLa cells expressing wild-type ERalpha in which the ER was knocked down with an ER-specific small interfering RNA were not killed by Tam or OHT, suggesting that estrogen response element-mediated transcription is required for Tam- and OHT-induced apoptosis. Microarray analysis to identify a gene(s) whose expression is important in OHT-ER-mediated apoptosis identified 19 mRNAs that OHT up-regulated by >1.6-fold and 15 down-regulated mRNAs. Gene function and the time course of induction by OHT-ERalpha led us to further investigate CCAAT enhancer-binding protein alpha (C/EBPalpha), which has roles in cell cycle progression and apoptosis, and p21. Quantitative reverse transcription-PCR, Western blot analysis, and RNA interference knockdown suggest that cell cycle arrest resulting from OHT-ERalpha induction of p21 may facilitate apoptosis. OHT-ERalpha, but not E2-ERalpha, induced C/EBPalpha mRNA and protein. RNA interference knockdown of C/EBPalpha nearly abolished OHT-ERalpha-induced apoptosis. We isolated stable cell lines that were resistant to OHT-induced apoptosis, contain full-length functional ERalpha, and undergo apoptosis in response to etoposide. In these OHT-resistant cell lines both before and after OHT treatment, C/EBPalpha levels are much lower than in OHT-sensitive cells. These studies establish a novel molecular site responsible for Tam- and OHT-ERalpha-induced apoptosis of cancer cells. |
| Databáze: | OpenAIRE |
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