Yuan Kaiyu, Yong Sun, Xu Fei, Zhou Tong, McDonald Jay M, Chen Yabing
Department of Pathology, University of Alabama at Birmingham, Alabama 35294, Birmingham, USA.
Department of Medicine, University of Alabama at Birmingham, Alabama 35294, Birmingham, USA.
Oncotarget. 2015 Sep 22;6(28):25308-19. doi: 10.18632/oncotarget.4490.
Pancreatic cancer is highly malignant with limited therapy and a poor prognosis. TRAIL-activating therapy has been promising, however, clinical trials have shown resistance and limited responses of pancreatic cancers. We investigated the effects of calmodulin(CaM) antagonists, trifluoperazine(TFP) and tamoxifen(TMX), on TRA-8-induced apoptosis and tumorigenesis of TRA-8-resistant pancreatic cancer cells, and underlying mechanisms. TFP or TMX alone did not induce apoptosis of resistant PANC-1 cells, while they dose-dependently enhanced TRA-8-induced apoptosis. TMX treatment enhanced efficacy of TRA-8 therapy on tumorigenesis in vivo. Analysis of TRA-8-induced death-inducing-signaling-complex (DISC) identified recruitment of survival signals, CaM/Src, into DR5-associated DISC, which was inhibited by TMX/TFP. In contrast, TMX/TFP increased TRA-8-induced DISC recruitment/activation of caspase-8. Consistently, caspase-8 inhibition blocked the effects of TFP/TMX on TRA-8-induced apoptosis. Moreover, TFP/TMX induced DR5 expression. With a series of deletion/point mutants, we identified CaM antagonist-responsive region in the putative Sp1-binding domain between -295 to -300 base pairs of DR5 gene. Altogether, we have demonstrated that CaM antagonists enhance TRA-8-induced apoptosis of TRA-8-resistant pancreatic cancer cells by increasing DR5 expression and enhancing recruitment of apoptotic signal while decreasing survival signals in DR5-associated DISC. Our studies support the use of these readily available CaM antagonists combined with TRAIL-activating agents for pancreatic cancer therapy.
胰腺癌具有高度恶性，治疗手段有限，预后较差。肿瘤坏死因子相关凋亡诱导配体（TRAIL）激活疗法曾显示出前景，然而，临床试验表明胰腺癌对此存在耐药性且反应有限。我们研究了钙调蛋白（CaM）拮抗剂三氟拉嗪（TFP）和他莫昔芬（TMX）对TRAIL-8诱导的TRAIL-8耐药胰腺癌细胞凋亡及肿瘤发生的影响及其潜在机制。单独使用TFP或TMX不会诱导耐药的胰腺癌细胞PANC-1凋亡，而它们能剂量依赖性地增强TRAIL-8诱导的凋亡。TMX处理增强了TRAIL-8疗法对体内肿瘤发生的疗效。对TRAIL-8诱导的死亡诱导信号复合物（DISC）的分析发现，存活信号CaM/Src募集到了与死亡受体5（DR5）相关的DISC中，而TMX/TFP可抑制这一过程。相反，TMX/TFP增加了TRAIL-8诱导的DISC募集/半胱天冬酶-8的激活。一致地，半胱天冬酶-8抑制阻断了TFP/TMX对TRAIL-8诱导凋亡的作用。此外，TFP/TMX诱导了DR5表达。通过一系列缺失/点突变体，我们在DR5基因-295至-300碱基对之间的假定Sp1结合域中确定了CaM拮抗剂反应区域。总之，我们证明了CaM拮抗剂通过增加DR5表达、增强凋亡信号募集同时减少与DR5相关的DISC中的存活信号，增强TRAIL-8诱导的TRAIL-8耐药胰腺癌细胞凋亡。我们的研究支持将这些易于获得的CaM拮抗剂与TRAIL激活剂联合用于胰腺癌治疗。
