Pramanik Kartick C, Fofaria Neel M, Gupta Parul, Srivastava Sanjay K
Corresponding Author: Sanjay K. Srivastava, Department of Biomedical Sciences, Suite 1103, Texas Tech University Health Sciences Center, 1406 Coulter Drive, Amarillo, TX 79106.
Mol Cancer Ther. 2014 Mar;13(3):687-98. doi: 10.1158/1535-7163.MCT-13-0863. Epub 2014 Jan 13.
Here, we investigated the potential mechanism of capsaicin-mediated apoptosis in pancreatic cancer cells. Capsaicin treatment phosphorylated c-jun-NH2-kinase (JNK); forkhead box transcription factor, class O (FOXO1); and BIM in BxPC-3, AsPC-1, and L3.6PL cells. The expression of BIM increased in response to capsaicin treatment. Capsaicin treatment caused cleavage of caspase-3 and PARP, indicating apoptosis. Antioxidants tiron and PEG-catalase blocked capsaicin-mediated JNK/FOXO/BIM activation and protected the cells from apoptosis. Furthermore, capsaicin treatment caused a steady increase in the nuclear expression of FOXO-1, leading to increased DNA binding. Capsaicin-mediated expression of BIM was found to be directly dependent on the acetylation of FOXO-1. The expression of CREB-binding protein (CBP) was increased, whereas SirT-1 was reduced by capsaicin treatment. Using acetylation mimic or defective mutants, our result demonstrated that phosphorylation of FOXO-1 was mediated through acetylation by capsaicin treatment. JNK inhibitor attenuated the phosphorylation of FOXO-1, activation of BIM, and abrogated capsaicin-induced apoptosis. Moreover, silencing FOXO1 by siRNA blocked capsaicin-mediated activation of BIM and apoptosis, whereas overexpression of FOXO-1 augmented its effects. Silencing Bim drastically reduced capsaicin-mediated cleavage of caspase-3 and PARP, indicating the role of BIM in apoptosis. Oral administration of 5 mg/kg capsaicin substantially suppressed the growth of BxPC-3 tumor xenografts in athymic nude mice. Tumors from capsaicin-treated mice showed an increase in the phosphorylation of JNK, FOXO-1, BIM, and levels of CBP, cleavage of caspase-3, PARP, and decreased SirT-1 expression. Taken together, our results suggest that capsaicin activated JNK and FOXO-1, leading to the acetylation of FOXO-1 through CBP and SirT-1. Acetylated FOXO1 induced apoptosis in pancreatic cancer cells through BIM activation.
在此，我们研究了辣椒素介导胰腺癌细胞凋亡的潜在机制。辣椒素处理使BxPC-3、AsPC-1和L3.6PL细胞中的c-jun氨基末端激酶（JNK）、叉头框转录因子O类（FOXO1）和BIM发生磷酸化。响应辣椒素处理，BIM的表达增加。辣椒素处理导致半胱天冬酶-3和聚（ADP-核糖）聚合酶（PARP）的裂解，表明发生了凋亡。抗氧化剂钛铁试剂和聚乙二醇化过氧化氢酶阻断了辣椒素介导的JNK/FOXO/BIM激活，并保护细胞免于凋亡。此外，辣椒素处理导致FOXO-1的核表达稳步增加，导致DNA结合增加。发现辣椒素介导的BIM表达直接依赖于FOXO-1的乙酰化。辣椒素处理使CREB结合蛋白（CBP）的表达增加，而沉默调节蛋白1（SirT-1）的表达降低。使用乙酰化模拟物或缺陷突变体，我们的结果表明，辣椒素处理通过乙酰化介导FOXO-1的磷酸化。JNK抑制剂减弱了FOXO-1的磷酸化、BIM的激活，并消除了辣椒素诱导的凋亡。此外，通过小干扰RNA（siRNA）沉默FOXO1可阻断辣椒素介导的BIM激活和凋亡，而FOXO-1的过表达增强了其作用。沉默Bim可显著降低辣椒素介导的半胱天冬酶-3和PARP的裂解，表明BIM在凋亡中的作用。口服5 mg/kg辣椒素可显著抑制无胸腺裸鼠体内BxPC-3肿瘤异种移植物的生长。来自辣椒素处理小鼠的肿瘤显示JNK、FOXO-1、BIM的磷酸化增加，CBP水平升高，半胱天冬酶-3、PARP裂解增加，SirT-1表达降低。综上所述，我们的结果表明，辣椒素激活JNK和FOXO-1，导致FOXO-1通过CBP和SirT-1发生乙酰化。乙酰化的FOXO1通过激活BIM诱导胰腺癌细胞凋亡。
