Cancer Research Institute, Xiangya School of Medicine, Central South University, Changsha, Hunan 410078, PR China.
Eur J Cancer. 2011 Jan;47(2):316-25. doi: 10.1016/j.ejca.2010.09.021. Epub 2010 Oct 11.
Grifolin, a secondary metabolite isolated from the fresh fruiting bodies of the mushroom Albatrellus confluens, has been shown to inhibit the growth of some cancer cell lines in vitro by induction of apoptosis in previous studies of our group. However, the mechanisms of action are not completely understood. An apoptosis-related gene expression profiling analysis provided a clue that death-associated protein kinase 1 (dapk1) gene was upregulated at least twofold in response to grifolin treatment in nasopharyngeal carcinoma cell CNE1. Here, we further investigated the role of DAPK1 in apoptotic effect induced by grifolin. We observed that protein as well as mRNA level of DAPK1 was induced by grifolin in a dose-dependent manner in nasopharyngeal carcinoma cell CNE1. We found that grifolin increased both Ser392 and Ser20 phosphorylation levels of transcription factor p53 protein, which could promote its transcriptional activity. Moreover, induced by grifolin, the recruitment of p53 to dapk1 gene promoter was confirmed to enhance markedly using EMSA and ChIP assays analysis. The involvement of DAPK1 in grifolin-induced apoptosis was supported by the studies that introducing siRNA targeting DAPK1 to CNE1 cells remarkably interfered grifolin-caused apoptotic effect as well as the activation of caspase-3. Grifolin induced upregulation of DAPK1 via p53 was also observed in tumour cells derived from human breast cancer and human colon cancer. The findings suggest that upregulation of DAPK1 via p53-DAPK1 pathway is an important mechanism of grifolin contributing to its ability to induce apoptotic effect. Since growing evidence found a significant loss of DAPK1 expression in a large variety of tumour types, grifolin may represent a promising candidate in the intervention of cancer via targeting DAPK1.
从白毒鹅膏菌新鲜子实体中分离得到的次生代谢产物姬松茸，在我们之前的研究中已被证明能够通过诱导细胞凋亡来抑制某些癌细胞系的体外生长。然而，其作用机制尚不完全清楚。一项与细胞凋亡相关的基因表达谱分析提供了一个线索，即在鼻咽癌细胞株 CNE1 中，死亡相关蛋白激酶 1（DAPK1）基因在受到姬松茸处理后至少上调了两倍。在这里，我们进一步研究了 DAPK1 在姬松茸诱导的凋亡效应中的作用。我们观察到，在鼻咽癌细胞株 CNE1 中，DAPK1 的蛋白和 mRNA 水平均呈剂量依赖性地被姬松茸诱导上调。我们发现，姬松茸增加了转录因子 p53 蛋白的 Ser392 和 Ser20 磷酸化水平，这可以促进其转录活性。此外，通过 EMSA 和 ChIP 分析证实，在姬松茸诱导下，p53 被招募到 dapk1 基因启动子，显著增强。通过向 CNE1 细胞引入靶向 DAPK1 的 siRNA 的研究表明，DAPK1 的诱导参与了姬松茸诱导的细胞凋亡，同时也激活了 caspase-3。在来源于人乳腺癌和人结肠癌的肿瘤细胞中，也观察到了 DAPK1 通过 p53 诱导的姬松茸。这些发现表明，p53-DAPK1 通路上调 DAPK1 是姬松茸诱导凋亡效应的一个重要机制。由于越来越多的证据表明在多种肿瘤类型中 DAPK1 的表达显著丢失，因此，通过靶向 DAPK1，姬松茸可能成为癌症干预的一个有前途的候选药物。
