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Modulation of p53, ErbB1, ErbB2, and Raf-1 expression in lung cancer cells by depsipeptide FR901228
Xiaodan Yu1, Z Sheng Guo, Monica G Marcu
1Thoracic Oncology Section, Surgery Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA.
Background:
Histone deacetylases (HDACs) modulate chromatin structure by regulating acetylation of core histone proteins. HDAC inhibitors, such as depsipeptide FR901228 (FK228), induce growth arrest and apoptosis in a variety of human cancer cells by mechanisms that cannot be attributed solely to histone acetylation. This study evaluated the mechanisms by which FK228 mediates apoptosis in non-small-cell lung cancer (NSCLC) cells.
Methods:
Proliferation and apoptosis were assessed in a panel of NSCLC cell lines that vary in the expression of the growth-regulating proteins p53, pRb, and K-Ras treated with a clinically relevant dose of FK228 (25 ng/mL). Western blot and immunoprecipitation techniques were used to analyze expression of cell-cycle proteins (cyclin A, cyclin E, p53, and p21), signaling-related proteins (ErbB1, ErbB2, and Raf-1), activity of extracellular signal-regulated kinase 1 and 2 (ERK1/2), binding of mutant p53 and Raf-1 to heat shock protein (Hsp)90, and acetylation of Hsp90.
Results:
FK228 treatment inhibited growth and induced apoptosis in NSCLC cells expressing wild-type or mutant p53. FK228 treatment led to altered expression of cyclin A, cyclin E, and p21, and to reduced expression of mutant, but not wild-type, p53. FK228-treated cells also were depleted of ErbB1, ErbB2, and Raf-1 proteins, and exhibited lower ERK1/2 activity. FK228 treatment also inhibited the binding of mutant p53 and Raf-1 to Hsp90; this inhibition was associated with acetylation of Hsp90.
Conclusions:
FK228 depletes the levels of several oncoproteins that are normally stabilized by binding to Hsp90 in cancer cells. The resulting ability of FK228 to diminish signal transduction via pathways involving Raf-1 and ERK may contribute to the potency and specificity of this novel antitumor agent.
Insights
The histone deacetylase inhibitor FK228 induces apoptosis in non-small-cell lung cancer cells by reducing oncoprotein levels and inhibiting key signaling pathways. This mechanism contributes to FK228
Area of Science:
- Molecular Biology
- Cancer Research
- Pharmacology
Background:
- Histone deacetylases (HDACs) regulate chromatin structure via histone acetylation.
- HDAC inhibitors like FK228 induce cancer cell apoptosis through multifaceted mechanisms beyond histone acetylation.
- This study investigates FK228's apoptosis-inducing mechanisms in non-small-cell lung cancer (NSCLC).
Purpose of the Study:
- To elucidate the molecular mechanisms by which FK228 mediates apoptosis in NSCLC cells.
- To analyze the impact of FK228 on cell-cycle proteins, signaling pathways, and heat shock protein 90 (Hsp90) interactions.
Main Methods:
- Assessed proliferation and apoptosis in NSCLC cell lines with varying p53, pRb, and K-Ras expression after FK228 treatment.
- Utilized Western blot and immunoprecipitation to analyze protein expression (cyclins, p53, p21, ErbB1, ErbB2, Raf-1), ERK1/2 activity, and Hsp90 binding/acetylation.
Main Results:
- FK228 inhibited growth and induced apoptosis in NSCLC cells, regardless of p53 status.
- FK228 altered cyclin A, cyclin E, and p21 expression, and reduced mutant p53 levels.
- FK228 depleted ErbB1, ErbB2, and Raf-1, decreased ERK1/2 activity, and inhibited mutant p53/Raf-1 binding to Hsp90, associated with Hsp90 acetylation.
Conclusions:
- FK228 depletes oncoproteins stabilized by Hsp90, impacting cancer cell survival.
- FK228 diminishes signal transduction via Raf-1 and ERK pathways.
- These effects contribute to the potency and specificity of FK228 as an antitumor agent.
