在正常细胞里，早期的致癌变异会诱导不可逆转的停止分裂状态，即致癌基因诱导的细胞早衰（OIS）。OIS具有肿瘤抑制作用，是一种细胞自身的抗癌机制。申请人长期致力于细胞衰老及调控机理的研究。在前期的研究中我们筛选到在人类肿瘤中过表达 miR-30，通过抑制它的靶点基因TNRC6A的表达来阻断致癌基因ras诱导的OIS。同时发现ras可能通过p38抑制miR-30的表达，从而诱导OIS，说明miR-30是细胞早衰信号通道中的重要部分。我们拟在前期工作的基础上开展以下研究：1）验证miR-30通过抑制TNRC6A阻断ras诱导的DNA损伤反应，从而阻断OIS。2）进一步研究ras-p38信号通道抑制miR-30表达的分子机制。3）最后，检测miR-30过表达和TNRC6A低表达在人类肿瘤样品中的相相关性。这些研究将增进我们对细胞内肿瘤抑制功能的分子机制的理解，并为研发抗癌药物提供新的靶点。

In normal mammalian cells, oncogene activation triggers an irreversible cell cycle arrest called oncogene-induced senescence (OIS). OIS is a tumor supressing defense mechanism, which needs to be abrogated by additional oncogenic mutations before cancer can develop. The applicant has been commitment to research on cellular senescence and its underlying mechanism. In our previous study, by using a genetic screen, we found that miR-30, a microRNA freqently overexpressed in cancer, disrupts oncogenic ras-induced OIS by suppressing the expression of a target gene TNRC6A. TNRC6A is a component of the microRNA processing machinery that has recently been implicated in DNA damage responses， which is an essential step towards OIS induction. In addition, our preliminary studies indicate that oncogenic ras suppresses miR-30 expression possibly through the p38 MAPK, to induce senescence, suggesting that miR-30 is an integral component in the senescence-inducing pathway. In this grant, We proposed to carry out the following studies based on previous work： 1）We will test the hypothesis that miR-30 disrupts oncogenic ras-induced OIS by suppressing TNRC6A-mediated DNA damage responses. 2）We will examine the mechanism by which the ras-p38 pathway supresses miR-30 expression in senescent cells. 3) We will try to establish that the ability of miR-30 to target TNRC6A contributes to human cancer development, by examining the correlation between miR-30 overexpresion and reduced TNRC6A expression in human tumor samples. These studies will advance our understanding of the signal transduction pathway that mediates oncogene-induced senescence. In addition, our work will shed light on the mechansim underlying the oncogenic activity of miR-30, and provide biological basis for cancer therapies targeting miR-30.

在本项目中，我们探讨了miR-30阻断致癌基因ras诱导细胞早衰（OIS）的具体机制。具体研究工作包括：1）验证了miR-30通过抑制TNRC6A阻断ras诱导的DNA损伤反应从而阻断OIS，并探讨了其内在分子机制；2）进一步研究了ras抑制miR-30表达的分子机制；3）检测了miR-30过表达和TNRC6A低表达在人类肿瘤样品中的相关性。我们通过研究发现miR-30的靶基因TNRC6A为ras诱导及γ射线诱导的DNA损伤反应所必需，参与了DNA损伤反应触发的p53活化反应，进而在细胞早衰的过程中发挥重要作用，而miR-30能够通过抑制TNRC6A抑制DNA损伤反应及其触发的p53活化反应；另一方面，ras通过激活p38γ抑制miR-30基因转录水平，进而抑制miR-30的表达。另外，我们还发现在多种不同人类癌症中中miR-30过表达和TNRC6A低表达具有一定相关性。我们的工作增强了对致癌基因诱导的细胞早衰的分子机制的理解，为以 miR-30为靶点的癌症治疗提供可行性研究及生物学基础。