Department of Human and Molecular Genetics, Virginia Commonwealth University, School of Medicine, Richmond, VA, USA.
Hepatology. 2011 May;53(5):1538-48. doi: 10.1002/hep.24216.
There is virtually no effective treatment for advanced hepatocellular carcinoma (HCC) and novel targets need to be identified to develop effective treatment. We recently documented that the oncogene Astrocyte elevated gene-1 (AEG-1) plays a seminal role in hepatocarcinogenesis. Employing yeast two-hybrid assay and coimmunoprecipitation followed by mass spectrometry, we identified staphylococcal nuclease domain containing 1 (SND1), a nuclease in the RNA-induced silencing complex (RISC) facilitating RNAi-mediated gene silencing, as an AEG-1 interacting protein. Coimmunoprecipitation and colocalization studies confirmed that AEG-1 is also a component of RISC and both AEG-1 and SND1 are required for optimum RISC activity facilitating small interfering RNA (siRNA) and micro RNA (miRNA)-mediated silencing of luciferase reporter gene. In 109 human HCC samples SND1 was overexpressed in ≈74% cases compared to normal liver. Correspondingly, significantly higher RISC activity was observed in human HCC cells compared to immortal normal hepatocytes. Increased RISC activity, conferred by AEG-1 or SND1, resulted in increased degradation of tumor suppressor messenger RNAs (mRNAs) that are target of oncomiRs. Inhibition of enzymatic activity of SND1 significantly inhibited proliferation of human HCC cells. As a corollary, stable overexpression of SND1 augmented and siRNA-mediated inhibition of SND1 abrogated growth of human HCC cells in vitro and in vivo, thus revealing a potential role of SND1 in hepatocarcinogenesis.
We unravel a novel mechanism that overexpression of AEG-1 and SND1 leading to increased RISC activity might contribute to hepatocarcinogenesis. Targeted inhibition of SND1 enzymatic activity might be developed as an effective therapy for HCC.
晚期肝细胞癌（HCC）几乎没有有效的治疗方法，需要确定新的靶点以开发有效的治疗方法。我们最近的研究表明，癌基因星形细胞瘤升高基因-1（AEG-1）在肝癌发生中起重要作用。我们采用酵母双杂交测定法、免疫共沉淀和质谱分析，鉴定出含葡萄球菌核酸酶结构域蛋白 1（SND1），这是 RNA 诱导沉默复合物（RISC）中的一种核酸酶，可促进 RNA 干扰介导的基因沉默，是 AEG-1 的相互作用蛋白。免疫共沉淀和共定位研究证实，AEG-1 也是 RISC 的组成部分，AEG-1 和 SND1 都是 RISC 最佳活性所必需的，可促进小干扰 RNA（siRNA）和微 RNA（miRNA）介导的荧光素酶报告基因沉默。在 109 个人 HCC 样本中，与正常肝组织相比，SND1 在 ≈74%的病例中过表达。相应地，与永生化正常肝细胞相比，人 HCC 细胞中的 RISC 活性明显更高。由 AEG-1 或 SND1 赋予的增加的 RISC 活性导致肿瘤抑制信使 RNA（mRNA）的降解增加，这些 mRNA 是致癌 miRNA 的靶标。SND1 的酶活性抑制显著抑制了人 HCC 细胞的增殖。作为推论，SND1 的稳定过表达增强了人 HCC 细胞的体外和体内生长，而 siRNA 介导的 SND1 抑制则消除了这种生长，从而揭示了 SND1 在肝癌发生中的潜在作用。
我们揭示了一种新的机制，即 AEG-1 和 SND1 的过表达导致 RISC 活性增加可能有助于肝癌的发生。靶向抑制 SND1 的酶活性可能被开发为 HCC 的有效治疗方法。
