INSERM U 837 Faculté de médecine, 1, place Verdun F- 59045 Lille Cedex France.
Mol Cancer Ther. 2009 Dec;8(12):3307-17. doi: 10.1158/1535-7163.MCT-09-0639.
Lamellarin D, a potent cytotoxic marine alkaloid, exerts its antitumor action through two complementary pathways: a nuclear route via topoisomerase I inhibition and a mitochondrial targeting. The present study was designed to investigate the contribution of these two pathways for apoptosis in cancer cells. Lamellarin D promoted nuclear apoptosis in leukemia cells without prominent cell cycle arrest. Signals transmitted by lamellarin D initiated apoptosis via the intrinsic apoptotic pathway. The drug induced conformational activation of Bax and decreased the expression levels of antiapoptotic proteins Bcl-2 and cIAP2 in association with activation of caspase-9 and caspase-3. Upon lamellarin D exposure, Fas and Fas-L expression was not modified in leukemia cells. Moreover, leukemia cells deficient in caspase-8 or Fas-associated protein with death domain underwent apoptosis through the typical mitochondrial apoptotic cascade, indicating that cell death induced by lamellarin D was independent of the extrinsic apoptotic pathway. Lamellarin D also exerted a topoisomerase I-mediated DNA damage response resulting in H2AX phosphorylation, and the upregulation of the DNA repair protein Rad51 and of p53, as well as the phosphorylation of p53 at serine 15. However, lamellarin D killed efficiently mutated p53 or p53 null cancer cells, and sensitivity to lamellarin D was abrogated neither by cycloheximide nor in enucleated cells. Lamellarin D-induced cytochrome c release occurs independently of nuclear factors in a cell-free system. These results suggest that lamellarin D exerts its cytotoxic effects primarily by inducing mitochondrial apoptosis independently of nuclear signaling. Thus, lamellarin D constitutes a new proapoptotic agent that may bypass certain forms of apoptosis resistance that occur in tumor cells.
拉米林 D 是一种有效的细胞毒性海洋生物碱，通过两种互补途径发挥其抗肿瘤作用：一种是通过拓扑异构酶 I 抑制的核途径，另一种是靶向线粒体。本研究旨在探讨这两种途径在癌细胞凋亡中的作用。拉米林 D 促进白血病细胞中的核凋亡，而不会明显引起细胞周期停滞。拉米林 D 传递的信号通过内在凋亡途径引发凋亡。该药物诱导 Bax 的构象激活，并降低抗凋亡蛋白 Bcl-2 和 cIAP2 的表达水平，同时激活 caspase-9 和 caspase-3。在拉米林 D 暴露下，白血病细胞中的 Fas 和 Fas-L 表达没有改变。此外，缺乏 caspase-8 或 Fas 相关死亡结构域蛋白的白血病细胞通过典型的线粒体凋亡级联反应发生凋亡，表明拉米林 D 诱导的细胞死亡不依赖于外在凋亡途径。拉米林 D 还发挥拓扑异构酶 I 介导的 DNA 损伤反应，导致 H2AX 磷酸化，以及 DNA 修复蛋白 Rad51 和 p53 的上调，以及 p53 在丝氨酸 15 位的磷酸化。然而，拉米林 D 有效地杀死了突变型 p53 或 p53 缺失的癌细胞，并且环已酰亚胺或去核细胞都不能消除对拉米林 D 的敏感性。拉米林 D 诱导的细胞色素 c 释放发生在无核细胞的细胞外系统中，不依赖于核因子。这些结果表明，拉米林 D 主要通过诱导线粒体凋亡发挥其细胞毒性作用，而不依赖于核信号。因此，拉米林 D 构成了一种新的促凋亡剂，可能绕过肿瘤细胞中发生的某些形式的凋亡抵抗。
