Yu Xiaodan, Guo Z Sheng, Marcu Monica G, Neckers Len, Nguyen Dao M, Chen G Aaron, Schrump David S
Thoracic Oncology Section, Surgery Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA.
J Natl Cancer Inst. 2002 Apr 3;94(7):504-13. doi: 10.1093/jnci/94.7.504.
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.
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.
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.
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.
组蛋白去乙酰化酶（HDACs）通过调节核心组蛋白的乙酰化来调控染色质结构。HDAC抑制剂，如缩肽FR901228（FK228），通过一些不能仅仅归因于组蛋白乙酰化的机制，在多种人类癌细胞中诱导生长停滞和凋亡。本研究评估了FK228介导非小细胞肺癌（NSCLC）细胞凋亡的机制。
在用临床相关剂量的FK228（25 ng/mL）处理的一组NSCLC细胞系中评估增殖和凋亡情况，这些细胞系在生长调节蛋白p53、pRb和K-Ras的表达上存在差异。采用蛋白质印迹和免疫沉淀技术分析细胞周期蛋白（细胞周期蛋白A、细胞周期蛋白E、p53和p21）、信号相关蛋白（表皮生长因子受体1、表皮生长因子受体2和Raf-1）的表达，细胞外信号调节激酶1和2（ERK1/2）的活性，突变型p53和Raf-1与热休克蛋白（Hsp）90的结合，以及Hsp90的乙酰化。
FK228处理抑制了表达野生型或突变型p53的NSCLC细胞的生长并诱导其凋亡。FK228处理导致细胞周期蛋白A、细胞周期蛋白E和p21的表达改变，且突变型p53（而非野生型p53）的表达降低。FK228处理的细胞中表皮生长因子受体1、表皮生长因子受体2和Raf-1蛋白也减少，并表现出较低的ERK1/2活性。FK228处理还抑制了突变型p53和Raf-1与Hsp90的结合；这种抑制与Hsp90的乙酰化有关。
FK228降低了癌细胞中几种通常通过与Hsp90结合而稳定的癌蛋白水平。FK228由此通过涉及Raf-1和ERK的途径减少信号转导的能力，可能有助于这种新型抗肿瘤药物的效力和特异性。
