Jiangsu Key Laboratory of Bioactive Natural Product Research and State Key Laboratory of Natural Medicines, China Pharmaceutical University, Nanjing, China.
J Cell Physiol. 2019 Aug;234(8):13191-13208. doi: 10.1002/jcp.27991. Epub 2018 Dec 17.
Osteosarcoma is the most frequent malignant primary bone tumor, and it generally develops a multidrug resistance. Chrysanthemulide A (CA) is a sesquiterpenoid from the herb Chrysanthemum indicum that has demonstrated a great anti-osteosarcoma potential. In this study, CA-induced apoptotic cell death resulted in the activation of the caspase-8-mediated caspase cascade, as evidenced by the cleavage of the substrate protein Bid and the caspase-8 inhibitor Z-VAD-FMK. The CA treatment upregulated the expression of death receptor 5 (DR5) in both whole cells and the cell membrane. Blocking DR5 expression by the small interfering RNA (siRNA) treatment decreased the caspase-8-mediated caspase cascade and efficiently attenuated CA-induced apoptosis, suggesting the critical role of DR5 in CA-induced apoptotic cell death. CA-induced upregulation of the DR5 protein was accompanied by the accumulation of LC3B-II, indicating the formation of autophagosomes. Importantly, DR5 upregulation was mediated by transcriptionally controlled autophagosome accumulation, as blockade of autophagosomes by LC3B or ATG-5 siRNA substantially decreased DR5 upregulation. Furthermore, CA activated the c-Jun N-terminal kinase (JNK) signaling pathway, and treatment with JNK siRNAs or inhibitor SP600125 significantly attenuated CA-mediated autophagosome accumulation and DR5-mediated cell apoptosis. Finally, CA sensitized the osteosarcoma cells to the DR5 ligand tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced apoptotic cell death. Above all, these results suggest that CA induces apoptosis through upregulating DR5 via JNK-mediated autophagosome accumulation and that combined treatment with CA and TRAIL might be a promising therapy for osteosarcoma.
骨肉瘤是最常见的恶性原发性骨肿瘤，通常会产生多药耐药性。菊花内酯 A（CA）是一种来自菊花的倍半萜烯，已证明具有很强的抗骨肉瘤潜力。在这项研究中，CA 诱导的细胞凋亡导致 caspase-8 介导的 caspase 级联反应的激活，这表现为底物蛋白 Bid 和 caspase-8 抑制剂 Z-VAD-FMK 的裂解。CA 处理上调了整个细胞和细胞膜中死亡受体 5（DR5）的表达。通过小干扰 RNA（siRNA）处理阻断 DR5 表达可减少 caspase-8 介导的 caspase 级联反应，并有效地抑制 CA 诱导的细胞凋亡，表明 DR5 在 CA 诱导的细胞凋亡中起关键作用。CA 诱导的 DR5 蛋白上调伴随着 LC3B-II 的积累，表明自噬体的形成。重要的是，DR5 的上调是由转录控制的自噬体积累介导的，因为 LC3B 或 ATG-5 siRNA 阻断自噬体可显著减少 DR5 的上调。此外，CA 激活了 c-Jun N-末端激酶（JNK）信号通路，并用 JNK siRNAs 或抑制剂 SP600125 处理可显著减弱 CA 介导的自噬体积累和 DR5 介导的细胞凋亡。最后，CA 使骨肉瘤细胞对 DR5 配体肿瘤坏死因子相关凋亡诱导配体（TRAIL）诱导的细胞凋亡敏感。综上所述，这些结果表明 CA 通过 JNK 介导的自噬体积累上调 DR5 诱导细胞凋亡，并且 CA 和 TRAIL 的联合治疗可能是骨肉瘤有前途的治疗方法。
