Zerp Shuraila F, Stoter Rianne, Kuipers Gitta, Yang Dajun, Lippman Marc E, van Blitterswijk Wim J, Bartelink Harry, Rooswinkel Rogier, Lafleur Vincent, Verheij Marcel
Department of Radiation Oncology, The Netherlands Cancer Institute-Antoni van Leeuwenhoek Hospital, Amsterdam, The Netherlands.
Radiat Oncol. 2009 Oct 23;4:47. doi: 10.1186/1748-717X-4-47.
Gossypol, a naturally occurring polyphenolic compound has been identified as a small molecule inhibitor of anti-apoptotic Bcl-2 family proteins. It induces apoptosis in a wide range of tumor cell lines and enhances chemotherapy- and radiation-induced cytotoxicity both in vitro and in vivo. Bcl-2 and related proteins are important inhibitors of apoptosis and frequently overexpressed in human tumors. Increased levels of these proteins confer radio- and chemoresistance and may be associated with poor prognosis. Consequently, inhibition of the anti-apoptotic functions of Bcl-2 family members represents a promising strategy to overcome resistance to anticancer therapies.
We tested the effect of (-)-gossypol, also denominated as AT-101, radiation and the combination of both on apoptosis induction in human leukemic cells, Jurkat T and U937. Because activation of the SAPK/JNK pathway is important for apoptosis induction by many different stress stimuli, and Bcl-X(L) is known to inhibit activation of SAPK/JNK, we also investigated the role of this signaling cascade in AT-101-induced apoptosis using a pharmacologic and genetic approach.
AT-101 induced apoptosis in a time- and dose-dependent fashion, with ED50 values of 1.9 and 2.4 microM in Jurkat T and U937 cells, respectively. Isobolographic analysis revealed a synergistic interaction between AT-101 and radiation, which also appeared to be sequence-dependent. Like radiation, AT-101 activated SAPK/JNK which was blocked by the kinase inhibitor SP600125. In cells overexpressing a dominant-negative mutant of c-Jun, AT-101-induced apoptosis was significantly reduced.
Our data show that AT-101 strongly enhances radiation-induced apoptosis in human leukemic cells and indicate a requirement for the SAPK/JNK pathway in AT-101-induced apoptosis. This type of apoptosis modulation may overcome treatment resistance and lead to the development of new effective combination therapies.
棉酚是一种天然存在的多酚类化合物，已被确定为抗凋亡Bcl-2家族蛋白的小分子抑制剂。它能在多种肿瘤细胞系中诱导凋亡，并在体外和体内增强化疗和放疗诱导的细胞毒性。Bcl-2及相关蛋白是重要的凋亡抑制剂，在人类肿瘤中经常过度表达。这些蛋白水平的升高赋予了放疗和化疗抗性，可能与预后不良有关。因此，抑制Bcl-2家族成员的抗凋亡功能是克服抗癌治疗抗性的一种有前景的策略。
我们测试了（-）-棉酚（也称为AT-101）、辐射以及两者联合对人白血病细胞Jurkat T和U937凋亡诱导的影响。由于SAPK/JNK途径的激活对于许多不同应激刺激诱导的凋亡很重要，并且已知Bcl-X(L)会抑制SAPK/JNK的激活，我们还使用药理学和遗传学方法研究了该信号级联在AT-101诱导的凋亡中的作用。
AT-101以时间和剂量依赖性方式诱导凋亡，在Jurkat T和U937细胞中的半数有效剂量（ED50）值分别为1.9和2.4 microM。等效线分析显示AT-101与辐射之间存在协同相互作用，这似乎也与顺序有关。与辐射一样，AT-101激活了SAPK/JNK，而这被激酶抑制剂SP600125阻断。在过表达c-Jun显性负性突变体的细胞中，AT-101诱导的凋亡显著减少。
我们的数据表明，AT-101强烈增强人白血病细胞中的辐射诱导凋亡，并表明AT-101诱导的凋亡需要SAPK/JNK途径。这种凋亡调节类型可能克服治疗抗性，并导致开发新的有效联合疗法。
