DOT1L结合的lncRNA介导自噬通路在小儿MLL-r白血病融合蛋白降解中的作用

The presence of MLL rearrangements，characterized by an exceptionally high incidence of chromosomal translocations affecting the MLL gene is the most important independent predictor of adverse outcome in pediatric leukemia, and the disease often presented as poor prognosis and high mortality. Thus, the distinct mechanisms of disease must be explored to develop a rational basis for the design of novel therapies for the treatment of this disease. LncRNAs have been recently demonstrated as key regulators in cancer progression. We previously carried out a genome-wide lncRNA expression study in MLL-r leukemia patients. A distinct set of lncRNAs associated with the pathways involved in the biological processes of MLL-r leukemia progression were identified. Specifically, we identified a lncRNA, named as LAMP5-AS1 was more highly expressed in pediatric MLL-r leukemia patients and all MLL-r cell lines, suggesting that the lncRNA was apparently associated with the MLL- fusion protein. Based on previous findings, in this study, following studies are initiated: (1) To investigate the role of LAMP5-AS1 in MLL-r leukemia progression and fusion proteindegradation; (2) To figure out the mechanism how LAMP5-AS1 affects the degradation of MLL fusion protein through regulating LAMP5, an autophage associated protein; (3) To investigate the interactions between the lncRNA and DOT1L, a histone H3 methyltransferase, and the the epigenetic mechanisms of LAMP5-AS1/DOT1L mediated in MLL-r leukemogenesis. The study would provide new theoretical basis and therapeutic target for diagnosis and treatment of pediatric MLL-r leukemia.

MLL白血病（MLL-r) 是小儿白血病中的高危病种，存活率低, 寻找早期诊断与新的治疗方法对提高其存活率具有重要的意义。我们前期开展了小儿MLL-r白血病的lncRNA表达谱研究，发现一个在小儿MLL-r患者中表达上调最多的一个lncRNA--LAMP5-AS1。重要的是其表达量与MLL融合蛋白表达量相关，提示LAMP5-AS1很可能是一个核心分子参与到MLL-r 白血病发生的通路中。本项目拟在此基础上开展以下研究：（1）解析LAMP5-AS1在MLL-r 小儿白血病患者中的表达差异及对MLL-r 白血病的发病的影响；（2）阐明LAMP5-AS1如何通过调控自噬相关基因LAMP5影响了MLL融合蛋白的降解；（3）揭示DOT1L结合LAMP5-AS1所介导的表观遗传机制。该项目的完成可为小儿MLL-r白血病的发病机制及针对MLL融合基因的治疗提供新的潜在靶点，具有重要的理论和应用意义 。

MLL白血病（MLL-r) 是小儿白血病中的高危病种，存活率低, 寻找早期诊断与新的治疗方 法对提高其存活率具有重要的意义。该项目在前期发现一个在小儿MLL-r患者中表达上调最多的一个lncRNA--LAMP5-AS1的基础上开展了以下研究：（1）解析了LAMP5-AS1在MLL-r 小儿白血病患者中的表 达差异，生存曲线分析显示高表达的LAMP5-AS1组病人的五年生存率显著降低，预示着LAMP5-AS1具有作为MLL-融合基因的分类器及预后指示器的潜在临床作用；（2）我们进一步探索了特异性高表达的LAMP5-AS1在MLL-r白血病中的功能及其参与疾病发生发展的分子机制。功能分析显示，敲低LAMP5-AS1能够显著抑制MLL-r白血病原代CD34+细胞的干性维持，而且极大的促进细胞的分化水平；（3）阐明了LAMP5-AS1通过调控自噬相关基因LAMP 5影响了MLL融合蛋白的降解；机制研究发现，LAMP5-AS1通过与DOT1L结合从而直接调控了下游基因座位的H3K79甲基化水平，从而影响下游基因的表达，其中一个重要的基因为LAMP5; (4)LAMP5-AS1通过直接调控自噬抑制基因LAMP5的表达，从而抑制MLL-融合基因的选择性自噬降解;（5）揭示DOT1L结合LAMP5-AS1所介导的表观遗传机制，LAMP5-AS1通过结合DOT1L的酶活性中心区域，调控其H3K79甲基化修饰酶活性。该项目的成果可为小儿MLL-r白血病的发病机制及针对MLL融合基因的治疗提供新的潜在靶点，具有重 要的理论和应用意义 。项目实施阶段，在国际期刊发表论文6篇，其中影响因子大于10的大类一区论文6篇，包括Blood、Molecular Cancer、Clinical Cancer Research 等，培养博士生6人，其中2人已毕业，博士后3人（2人已经顺利出站）。申请国家发明专利2项；对照项目合同书，本项目研究目标已达到，很好完成项目计划内容。