Newman Robert A, Kondo Yasuko, Yokoyama Tomohisa, Dixon Susan, Cartwright Carrie, Chan Diana, Johansen Mary, Yang Peiying
Department of Experimental Therapeutics, University of Texas M. D. Anderson Cancer Center, Houston, Texas 77054, USA.
Integr Cancer Ther. 2007 Dec;6(4):354-64. doi: 10.1177/1534735407309623.
Lipid-soluble cardiac glycosides such as bufalin, oleandrin, and digitoxin have been suggested as potent agents that might be useful as anticancer agents. Past research with oleandrin, a principle cardiac glycoside in Nerium oleander L. (Apocynaceae), has been shown to induce cell death through induction of apoptosis. In PANC-1 cells, a human pancreatic cancer cell line, cell death occurs not through apoptosis but rather through autophagy. Oleandrin at low nanomolar concentrations potently inhibited cell proliferation associated with induction of a profound G(2)/M cell cycle arrest. Inhibition of cell cycle was not accompanied by any significant sub G1 accumulation of cells, suggesting a nonapoptotic mechanism. Oleandrin-treated cells exhibited time- and concentration-dependent staining with acridine orange, a lysosomal stain. Subcellular changes within PANC-1 cells included mitochondrial condensation and translocation to a perinuclear position accompanied by vacuoles. Use of a fluorescent oleandrin analog (BODIPY-oleandrin) revealed co-localization of the drug within cell mitochondria. Damaged mitochondria were found within autophagosome structures. Formation of autophagosomes was confirmed through electron microscopy and detection of green fluorescent protein-labeled light chain 3 association with autophagosome membranes. Also observed was a drug-mediated inhibition of pAkt formation and up-regulation of pERK. Transfection of Akt into PANC-1 cells or inhibition of pERK activation by MAPK inhibitor abrogated oleandrin-mediated inhibition of cell growth, suggesting that the reduction of pAkt and increased pERK are important to oleandrin's ability to inhibit tumor cell proliferation. The data provide insight into the mechanisms and role of a potent, lipid-soluble cardiac glycoside (oleandrin) in control of human pancreatic cancer proliferation.
脂溶性强心苷，如蟾毒灵、夹竹桃苷和洋地黄毒苷，被认为是可能用作抗癌剂的强效药物。过去对夹竹桃苷（夹竹桃科夹竹桃属植物中的一种主要强心苷）的研究表明，它可通过诱导细胞凋亡来诱导细胞死亡。在人胰腺癌细胞系PANC-1细胞中，细胞死亡并非通过凋亡发生，而是通过自噬。低纳摩尔浓度的夹竹桃苷能有效抑制细胞增殖，并诱导深度的G(2)/M期细胞周期阻滞。细胞周期的抑制并未伴随着细胞显著的亚G1期积累，这表明其作用机制并非凋亡。经夹竹桃苷处理的细胞用吖啶橙（一种溶酶体染料）染色呈现出时间和浓度依赖性。PANC-1细胞内的亚细胞变化包括线粒体凝聚并转移至核周位置，同时伴有液泡形成。使用荧光夹竹桃苷类似物（BODIPY-夹竹桃苷）显示该药物与细胞线粒体内共定位。在自噬体结构中发现了受损的线粒体。通过电子显微镜以及检测绿色荧光蛋白标记的轻链3与自噬体膜的结合，证实了自噬体的形成。还观察到药物介导的pAkt形成抑制和pERK上调。将Akt转染到PANC-1细胞中或用MAPK抑制剂抑制pERK激活可消除夹竹桃苷介导的细胞生长抑制，这表明pAkt的减少和pERK的增加对夹竹桃苷抑制肿瘤细胞增殖的能力很重要。这些数据为一种强效脂溶性强心苷（夹竹桃苷）在控制人胰腺癌增殖中的机制和作用提供了见解。
