Experimental Tumorpathology, Department of Pathology, University of Erlangen-Nürnberg, Universitätsstr. 22, 91054 Erlangen, Germany.
Apoptosis. 2012 Dec;17(12):1300-15. doi: 10.1007/s10495-012-0757-7.
The histone deacetylase inhibitor (HDACi) LBH589 has been verified as an effective anticancer agent. The identification and characterization of new targets for LBH589 action would further enhance our understanding of the molecular mechanisms involved in HDACi therapy. The role of the tumor suppressor death-associated protein kinase (DAPK) in LBH589-induced cytotoxicity has not been investigated to date. Stable DAPK knockdown (shRNA) and DAPK overexpressing (DAPK+++) cell lines were generated from HCT116 wildtype colon cancer cells. LBH589 inhibited cell proliferation, reduced the long-term survival, and up-regulated and activated DAPK in colorectal cancer cells. Moreover, LBH589 significantly suppressed the growth of colon tumor xenografts and in accordance with the in vitro studies, increased DAPK levels were detected immunohistochemically. LBH589 induced a DAPK-dependent autophagy as assessed by punctuate accumulation of LC3-II, the formation of acidic vesicular organelles, and degradation of p62 protein. LBH589-induced autophagy seems to be predominantly caused by DAPK protein interactions than by its kinase activity. Caspase inhibitor zVAD increased autophagosome formation, decreased the cleavage of caspase 3 and PARP but didn't rescue the cells from LBH589-induced cell death in crystal violet staining suggesting both caspase-dependent as well as caspase-independent apoptosis pathways. Pre-treatment with the autophagy inhibitor Bafilomycin A1 caused caspase 3-mediated apoptosis in a DAPK-dependent manner. Altogether our data suggest that DAPK induces autophagy in response to HDACi-treatment. In autophagy deficient cells, DAPK plays an essential role in committing cells to HDACi-induced apoptosis.
组蛋白去乙酰化酶抑制剂(HDACi)LBH589 已被证实为一种有效的抗癌药物。鉴定和描述 LBH589 作用的新靶点将进一步增强我们对 HDACi 治疗中涉及的分子机制的理解。迄今为止,尚未研究肿瘤抑制因子死亡相关蛋白激酶(DAPK)在 LBH589 诱导的细胞毒性中的作用。从 HCT116 野生型结肠癌细胞中生成了稳定的 DAPK 敲低(shRNA)和 DAPK 过表达(DAPK+++)细胞系。LBH589 抑制结肠癌细胞的增殖,降低长期存活率,并在上调和激活 DAPK。此外,LBH589 显著抑制结肠肿瘤异种移植物的生长,并且与体外研究一致,免疫组织化学检测到 DAPK 水平增加。LBH589 诱导 DAPK 依赖性自噬,表现为 LC3-II 点状积累、酸性囊泡细胞器的形成和 p62 蛋白的降解。LBH589 诱导的自噬似乎主要是由 DAPK 蛋白相互作用引起的,而不是由其激酶活性引起的。半胱天冬酶抑制剂 zVAD 增加自噬体的形成,减少 caspase 3 和 PARP 的切割,但不能挽救细胞免受 LBH589 诱导的结晶紫染色中的细胞死亡,这表明存在 caspase 依赖性和 caspase 非依赖性凋亡途径。用自噬抑制剂 Bafilomycin A1 预处理导致 caspase 3 介导的 DAPK 依赖性凋亡。总的来说,我们的数据表明 DAPK 诱导自噬以响应 HDACi 治疗。在自噬缺陷细胞中,DAPK 在将细胞定向到 HDACi 诱导的凋亡中起着至关重要的作用。