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Analysis of leukemogenic mechanism of MLL-AF4 family and development of new therapeutic strategy of MLL-rearranged acute leukemia

MLL-AF4家族致白血病机制分析及MLL重排急性白血病治疗新策略开发

基本信息

批准号：
21791000
负责人：
IMAMURA Toshihiko
金额：
$ 2.75万
依托单位：
Kyoto Prefectural University of Medicine
依托单位国家：
日本
项目类别：
Grant-in-Aid for Young Scientists (B)
财政年份：
2009
资助国家：
日本
起止时间：
2009 至 2010
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-21791000/
关键词：
小児血液学 MLL AF4 白血病発症機序レトロウイルス乳児白血病

项目摘要

Because the prognosis of MLL-AF4-positive acute lymphoblastic leukemia is still extremely poor, understanding of leukemogenic mechanism of MLL-Af4 fusion gene is important for the development of new treatments. We analyzed the leukemogenic mechanism of MLL-AF4 fusion gene using retroviral gene expression system. As a result of myeloid transformation assay, we revealed that MLL-murine Af4 (mAf4) could immortalize murine linenage-depleted bone marrow (Lin-BM) cells. Using a series of hybrid mutants of human AF4/mAf4, we found that amino acids 1026 to 1177 of mAf4 are essential for the leukemogenesis of MLL-mAf4 fusion gene. Overexpression of HoxA9, A10, and Meis1 was confirmed by quantitative RT-PCR analysis of the transduced Lin-BM cells. Chromatin immunoprecipitation (ChIP) assay demonstrated histone H3 lysine79 (H3K79) dimethylation was occurred in promoter regions of HoxA9. Based on these results, we considered that MLL-mAf4 immortalized murine Lin-BM cells by induction of the overexpression of HoxA genes through H3K79 dimethylation in promoter regions of these genes. Our mouse model expressing MLL-mAf4 reproduces well the leukemogenic mechanism of human MLL-AF4-positive leukemias, it is expected to be a good model for the development of new treatments.

由于MLL-AF4阳性的急性淋巴细胞白血病预后极差，了解MLL-AF4融合基因的致病机制对开发新的治疗方法具有重要意义。我们利用逆转录病毒基因表达系统分析了MLL-AF4融合基因的致白血病机制。通过髓系转化实验，我们发现MLL-小鼠Af4(MAf4)能使小鼠骨髓(Lin-BM)细胞永生化。利用人AF4/mAf4的一系列杂交突变体，我们发现mAf4的1026-1177位氨基酸是MLL-mAf4融合基因发生白血病所必需的。通过对转导的LIN-BM细胞进行定量RT-PCR分析，证实了HoxA9、A10和Meis1的高表达。染色质免疫沉淀(ChIP)分析表明，组蛋白H3K79(H3K79)在HoxA9启动子区域发生了二甲基化。基于这些结果，我们认为MLL-mAf4通过H3K79启动子区域的H3K79二甲基化诱导HoxA基因的过度表达而使小鼠LIN-BM细胞永生化。我们的表达MLL-mAf4的小鼠模型很好地再现了人类MLL-AF4阳性白血病的致病机制，有望成为开发新的治疗方法的良好模型。