From the Cytokine Research Laboratory, Department of Experimental Therapeutics, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030,; the Cancer Institute, University of Mississippi Medical Center, Jackson, Mississippi 39216.
the Organic Chemistry Section, National Institute for Interdisciplinary Science and Technology (CSIR), Trivandrum, 695 019 Kerala, India.
J Biol Chem. 2013 Nov 8;288(45):32343-32356. doi: 10.1074/jbc.M113.455188. Epub 2013 Sep 27.
Although tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has shown efficacy in a phase 2 clinical trial, development of resistance to TRAIL by tumor cells is a major roadblock. We investigated whether azadirone, a limonoidal tetranortriterpene, can sensitize human tumor cells to TRAIL. Results indicate that azadirone sensitized cancer cells to TRAIL. The limonoid induced expression of death receptor (DR) 5 and DR4 but did not affect expression of decoy receptors in cancer cells. The induction of DRs was mediated through activation of ERK and through up-regulation of a transcription factor CCAAT enhancer-binding protein homologous protein (CHOP) as silencing of these signaling molecules abrogated the effect of azadirone. These effects of azadirone were cancer cell-specific. The CHOP binding site on the DR5 gene was required for induction of DR5 by azadirone. Up-regulation of DRs was mediated through the generation of reactive oxygen species (ROS) as ROS scavengers reduced the effect of azadirone on ERK activation, CHOP up-regulation, DR induction, and TRAIL sensitization. The induction of DRs by this limonoid was independent of p53, but sensitization to TRAIL was p53-dependent. The limonoid down-regulated the expression of cell survival proteins and up-regulated the proapoptotic proteins. The combination of azadirone with TRAIL was found to be additive at concentrations lower than IC50, whereas at higher concentrations, the combination was synergistic. Overall, this study indicates that azadirone can sensitize cancer cells to TRAIL through ROS-ERK-CHOP-mediated up-regulation of DR5 and DR4 signaling, down-regulation of cell survival proteins, and up-regulation of proapoptotic proteins.
尽管肿瘤坏死因子相关凋亡诱导配体（TRAIL）在 2 期临床试验中显示出疗效，但肿瘤细胞对 TRAIL 的耐药性是一个主要障碍。我们研究了 limonoidal tetranortriterpene 八角枫酮是否可以使人类肿瘤细胞对 TRAIL 敏感。结果表明，八角枫酮使癌细胞对 TRAIL 敏感。该 limonoid 诱导了死亡受体（DR）5 和 DR4 的表达，但不影响癌细胞中诱饵受体的表达。DR 的诱导是通过 ERK 的激活以及通过上调转录因子 CCAAT 增强子结合蛋白同源蛋白（CHOP）介导的，因为这些信号分子的沉默消除了八角枫酮的作用。八角枫酮的这些作用是癌细胞特异性的。DR5 基因上的 CHOP 结合位点是八角枫酮诱导 DR5 的必需条件。DRs 的上调是通过活性氧（ROS）的产生介导的，因为 ROS 清除剂降低了八角枫酮对 ERK 激活、CHOP 上调、DR 诱导和 TRAIL 增敏的作用。这种 limonoid 诱导 DRs 的作用独立于 p53，但对 TRAIL 的敏感性依赖于 p53。该 limonoid 下调细胞存活蛋白的表达并上调促凋亡蛋白。发现八角枫酮与 TRAIL 的组合在低于 IC50 的浓度下是相加的，而在较高浓度下则是协同的。总的来说，这项研究表明，八角枫酮可以通过 ROS-ERK-CHOP 介导的 DR5 和 DR4 信号的上调、细胞存活蛋白的下调和促凋亡蛋白的上调，使癌细胞对 TRAIL 敏感。
