Yamaguchi Yumi, Shiraki Katsuya, Fuke Hiroyuki, Inoue Tomoko, Miyashita Kazumi, Yamanaka Yutaka, Saitou Yukiko, Sugimoto Kazushi, Nakano Takeshi
First Department of Internal Medicine, Mie University School of Medicine, Edobashi 2-174, Tsu, Mie 514-8507, Japan.
Oncol Rep. 2005 Nov;14(5):1311-6.
The inhibitors of apoptosis (IAPs) family regulate apoptosis by preventing the action of the central execution phase, and function as mediators and regulators of the anti-apoptotic activity of the v-Rel and NF-kappaB transcription factor families. The targeting of IAPs may be a promising strategy, but it is not well elucidated in human hepatocellular carcinomas (HCCs). We have therefore investigated the effects of the down-regulation of IAPs (XIAP or survivin) on the TNF-related apoptosis-inducing ligand (TRAIL) and chemotherapeutic agents that induced apoptosis in human HCC cells. To inhibit the IAPs gene expression, we designed small interfering RNA (siRNA) against the X-chromosome-linked IAP (XIAP) or survivin and investigated their efficacy in the suppression of the XIAP or survivin expression in two HCC cells (SK-Hep1 and HLE), and their consequent antitumor potential. We found that the designed siRNAs against the XIAP and survivin downregulated the protein expression of respective genes by almost 50%. The suppression of IAPs resulted in a significant decrease in procaspase-3 levels, especially by suppression of the XIAP. The apoptosis cell count was small in cells transfected with control siRNA and siRNA against the XIAP or survivin, but after treatment with 10 ng/ml of TRAIL, the apoptosis cells increased 2-3 times by the suppression of IAPs as control. The cytotoxicity of doxorubicin and camptothecin was augmented by the suppression of the XIAP in SK-Hep1 cells, whereas the suppression of survivin did not affect cytotoxicity. In conclusion, downregulation of the XIAP or survivin enhances cell death by TRAIL and increases sensitivity against some chemotherapeutic agents in HCC cells. In particular, the XIAP may be a potential target to increase therapeutic sensitivity.
凋亡抑制蛋白（IAPs）家族通过阻止核心执行阶段的作用来调节细胞凋亡，并作为v-Rel和NF-κB转录因子家族抗凋亡活性的介质和调节剂发挥作用。靶向IAPs可能是一种有前景的策略，但在人类肝细胞癌（HCC）中尚未得到充分阐明。因此，我们研究了IAPs（X连锁凋亡抑制蛋白（XIAP）或生存素）下调对肿瘤坏死因子相关凋亡诱导配体（TRAIL）和诱导人类肝癌细胞凋亡的化疗药物的影响。为了抑制IAPs基因表达，我们设计了针对X染色体连锁IAP（XIAP）或生存素的小干扰RNA（siRNA），并研究了它们在两种肝癌细胞（SK-Hep1和HLE）中抑制XIAP或生存素表达的效果及其随后的抗肿瘤潜力。我们发现，针对XIAP和生存素设计的siRNAs分别使各自基因的蛋白表达下调了近50%。IAPs的抑制导致procaspase-3水平显著降低，尤其是通过抑制XIAP。用对照siRNA和针对XIAP或生存素的siRNA转染的细胞中凋亡细胞数量较少，但在用10 ng/ml的TRAIL处理后，与对照相比，通过抑制IAPs，凋亡细胞增加了2至3倍。在SK-Hep1细胞中，阿霉素和喜树碱的细胞毒性因XIAP的抑制而增强，而生存素的抑制不影响细胞毒性。总之，XIAP或生存素的下调增强了TRAIL诱导的细胞死亡，并增加了肝癌细胞对某些化疗药物的敏感性。特别是，XIAP可能是提高治疗敏感性的潜在靶点。
