Background and objective Tumor necrosis factor-related apoptosis-inducting ligand (TRAIL) can in-duce apoptosis of tumor cells, however, various of tumor cells may survive because of resistance to TRAIL-mediated apoptosis. This study is to observe the proliferation inhibition effect of TRAIL sensitized by thioridazine on PC9 cells through endoplas-mic reticulum (ER) stress mediated up-regulation of death receptor 5 (DR5) and investigate its mechanism.Methods PC9 cells were treated with different concentrations of thioridazine and TRAIL alone or in combination. Cell proliferation was mea-sured by MTT assay, and cell apoptosis and cell-surface DR5 were detected by flow cytometry. Western blotting was utilized to measure the expressions of ER stress-related proteins glucose regulated protein 78 (GRP78), C/EBP homologous protein (CHOP), p-PKR-like ER kinase (PERK), p-eukaryotic initiation factor-2α (eIF2α), activating transcription factor 4 (ATF4) and apoptosis-related proteins caspase-3, caspase-9, caspase-8, PARP, DR5.Results Thioridazine inhibited the proliferation of PC9 cells in a dose-dependent manner (P<0.05). Thioridazine increased the inhibition and apoptosis of PC9 cells and up-regulated the expression of cell-surface DR5 induced by TRAIL. Flow cytometry showed that compared with TRAIL group,combination group of TRAIL and thioridazine increased cell apoptotic rates significantly (P<0.05). Western blotting indicated that compared with TRAIL group, expressions of Cleaved-caspase-8, Cleaved-PARP and DR5 increased significantly in combi-nation group of TRAIL and thioridazine. The induction of DR5 and pro-apoptotic effect were mediated through activation of ER stress accompanying by increased synthesis of GRP78 and CHOP, which can be blocked by adding of ER stress inhibitor 4-PBA.Conclusion Thioridazine enhanced proliferation inhibition effect of TRAIL in PC9 cells may be facilitated through ER stress mediated upregulation of DR5.%背景与目的 肿瘤坏死因子相关凋亡诱导配体(tumor necrosis factor-related apoptosis-inducting li-gand,TRAIL)可诱导肿瘤细胞发生凋亡,然而相当数量的肿瘤细胞可耐受TRAIL诱导的凋亡而得以存活.本实验观察硫利达嗪(thioridazine,THZ)通过诱导内质网应激(endoplasmic reticulum stress,ER stress)介导的死亡受体5(death receptor 5,DR5)表达上调,继而增敏TRAIL对肺腺癌细胞PC9的生长抑制及凋亡诱导效应,探讨其机制.方法 不同浓度硫利达嗪及TRAIL单独或联合处理PC9细胞,MTT法检测细胞活性变化,流式细胞术检测细胞表面DR5表达及细胞凋亡率,Western blotting检测内质网应激相关蛋白GRP78(glucose regu-lated protein 78)、C/EBP环磷酸腺苷反应元件结合转录因子同源蛋白(C/EBP homologous protein,CHOP)、p-PERK(PKR-like ER kinase)、p-eIF2α(eukaryotic initiation factor-2α,eIF2α)、ATF4(activating transcription fac-tor 4,ATF4)及凋亡相关蛋白Caspase-3、Caspase-9、Caspase-8、PARP、DR5表达变化.结果 硫利达嗪对PC9细胞的增殖抑制效应呈浓度依赖性(P<0.05),硫利达嗪可增加TRAIL对PC9细胞的抑制作用及凋亡诱导作用且可上调PC9细胞表面DR5表达水平,流式细胞术结果显示:TRAIL联合硫利达嗪组细胞凋亡率较单独TRAIL组显著增加(P<0.05),Western blotting结果显示:TRAIL联合硫利达嗪组细胞Cleaved-caspase-8、Cleaved-PARP、DR5表达水平较单独TRAIL组明显上调.DR5表达上调及促凋亡效应是通过诱导内质网应激发生,并伴随着GRP78及CHOP表达上调发生的,且该效应可被4-苯基丁酸(4-phenylbutyric acid,4-PBA)可抑制(P<0.05).结论 硫利达嗪增敏TRAIL对PC9细胞的增殖抑制效应显著,其机制可能与硫利达嗪内质网应激介导的DR5上调有关.
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