Cytokine Research Laboratory, Department of Experimental Therapeutics, The University of Texas M.D. Anderson Cancer Center, Houston, TX 77030, USA.
Free Radic Biol Med. 2012 Nov 15;53(10):1977-87. doi: 10.1016/j.freeradbiomed.2012.08.012. Epub 2012 Aug 15.
A major problem in clinical trials of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) as cancer therapy is the development of resistance to TRAIL. Therefore, agents that can overcome TRAIL resistance have great therapeutic potential. In this study, we evaluated capsazepine, a TRPV1 antagonist, for its ability to sensitize human colon cancer cells to TRAIL-induced apoptosis. Capsazepine potentiated the effect of TRAIL, as shown by its effect on intracellular esterase activity; activation of caspase-8,-9, and -3; and colony-formation assay. Capsazepine induced death receptors (DRs) DR5 and DR4, but not decoy receptors, at the transcriptional level and in a non-cell-type-specific manner. DR induction was dependent on CCAAT/enhancer-binding protein homologous protein (CHOP), as shown by (a) the induction of CHOP by capsazepine and (b) the abolition of DR- and potentiation of TRAIL-induced apoptosis by CHOP gene silencing. CHOP induction was also reactive oxygen species (ROS)-dependent, as shown by capsazepine's ability to induce ROS and by the quenching of ROS by N-acetylcysteine or glutathione, which prevented induction of CHOP and DR5 and consequent sensitization to TRAIL. Capsazepine's effects appeared to be mediated via JNK, as shown by capsazepine's ability to induce JNK and by the suppression of both CHOP and DR5 activation by inhibition of JNK. Furthermore, ROS sequestration abrogated the activation of JNK. Finally, capsazepine downregulated the expression of various antiapoptotic proteins (e.g., cFLIP and survivin) and increased the expression of proapoptotic proteins (e.g., Bax and p53). Together, our results indicate that capsazepine potentiates the apoptotic effects of TRAIL through downregulation of cell survival proteins and upregulation of death receptors via the ROS-JNK-CHOP-mediated pathway.
肿瘤坏死因子相关凋亡诱导配体（TRAIL）作为癌症治疗的临床试验中的一个主要问题是对 TRAIL 产生耐药性。因此，能够克服 TRAIL 耐药性的药物具有很大的治疗潜力。在这项研究中，我们评估了辣椒素，一种 TRPV1 拮抗剂，其对 TRAIL 诱导的人结肠癌细胞凋亡的增敏作用。辣椒素增强了 TRAIL 的作用，表现在细胞内酯酶活性、半胱天冬酶-8、-9 和 -3 的激活以及集落形成试验。辣椒素在转录水平上诱导死亡受体（DR）DR5 和 DR4，但不诱导诱饵受体，并且以非细胞类型特异性的方式诱导。DR 诱导依赖于 CCAAT/增强子结合蛋白同源蛋白（CHOP），如辣椒素诱导 CHOP 和 CHOP 基因沉默消除 DR 并增强 TRAIL 诱导的细胞凋亡所示。CHOP 诱导也依赖于活性氧（ROS），如辣椒素诱导 ROS 的能力以及 N-乙酰半胱氨酸或谷胱甘肽对 ROS 的淬灭能力所示，这阻止了 CHOP 和 DR5 的诱导以及随后对 TRAIL 的敏感性。辣椒素的作用似乎是通过 JNK 介导的，如辣椒素诱导 JNK 的能力以及抑制 JNK 抑制 CHOP 和 DR5 激活的能力所示。此外，ROS 隔离消除了 JNK 的激活。最后，辣椒素下调了各种抗凋亡蛋白（如 cFLIP 和 survivin）的表达，并增加了促凋亡蛋白（如 Bax 和 p53）的表达。总之，我们的结果表明，辣椒素通过下调细胞存活蛋白和上调死亡受体，通过 ROS-JNK-CHOP 介导的途径增强 TRAIL 的凋亡作用。
