Li Ling, Han Weidong, Gu Ying, Qiu Shuang, Lu Qinghua, Jin Jie, Luo Jianhong, Hu Xun
Cancer Institute, The Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China.
Cancer Res. 2007 May 15;67(10):4894-903. doi: 10.1158/0008-5472.CAN-06-3818.
Previous reports have shown that honokiol induces apoptosis in numerous cancer cell lines and showed preclinical efficacies against apoptosis-resistant B-cell chronic lymphocytic leukemia and multiple myeloma cells from relapse-refractory patients. Here, we show that honokiol can induce a cell death distinct from apoptosis in HL60, MCF-7, and HEK293 cell lines. The death was characterized by a rapid loss of integrity of plasma membrane without externalization of phosphatidyl serine. The broad caspase inhibitor z-VAD-fmk failed to prevent this cell death. Consistently, caspase activation and DNA laddering were not observed. The death was paralleled by a rapid loss of mitochondrial membrane potential, which was mechanistically associated with the mitochondrial permeability transition pore regulated by cyclophilin D (CypD) based on the following evidence: (a) cyclosporin A, an inhibitor of CypD (an essential component of the mitochondrial permeability transition pore), effectively prevented honokiol-induced cell death and loss of mitochondrial membrane potential; (b) inhibition of CypD by RNA interference blocked honokiol-induced cell death; (c) CypD up-regulated by honokiol was correlated with the death rates in HL60, but not in K562 cells, which underwent apoptosis after being exposed to honokiol. We further showed that honokiol induced a CypD-regulated death in primary human acute myelogenous leukemia cells, overcame Bcl-2 and Bcl-X(L)-mediated apoptotic resistance, and was effective against HL60 cells in a pilot in vivo study. To the best of our knowledge, this is the first report to document an induction of mitochondrial permeability transition pore-associated cell death by honokiol.
先前的报告表明，厚朴酚可诱导多种癌细胞系凋亡，并在临床前研究中显示出对复发难治患者的凋亡抗性B细胞慢性淋巴细胞白血病和多发性骨髓瘤细胞有效。在此，我们表明厚朴酚可在HL60、MCF-7和HEK293细胞系中诱导一种不同于凋亡的细胞死亡。这种死亡的特征是质膜完整性迅速丧失，而磷脂酰丝氨酸没有外翻。广谱半胱天冬酶抑制剂z-VAD-fmk未能阻止这种细胞死亡。一致地，未观察到半胱天冬酶激活和DNA梯状条带。这种死亡与线粒体膜电位的迅速丧失同时发生，基于以下证据，其机制与亲环蛋白D（CypD）调节的线粒体通透性转换孔有关：（a）环孢素A，一种CypD（线粒体通透性转换孔的必需成分）的抑制剂，有效地阻止了厚朴酚诱导的细胞死亡和线粒体膜电位丧失；（b）通过RNA干扰抑制CypD可阻断厚朴酚诱导的细胞死亡；（c）厚朴酚上调的CypD与HL60细胞的死亡率相关，但与K562细胞无关，K562细胞在暴露于厚朴酚后发生凋亡。我们进一步表明，厚朴酚在原代人急性髓性白血病细胞中诱导CypD调节的死亡，克服了Bcl-2和Bcl-X(L)介导的凋亡抗性，并且在一项初步体内研究中对HL60细胞有效。据我们所知，这是第一份记录厚朴酚诱导线粒体通透性转换孔相关细胞死亡的报告。
