NUP98重排白血病的致病机制研究

Rearrangements of 11p15 involving NUP98 gene are common chromosomal abnormalities in hematologic malignancies including de novo and therapy-related acute myeloid leukemia (AML), acute lymphoblastic leukemia (ALL), myelodysplastic syndromes（MDS） and advanced stages of chronic myeloid leukemia (CML). The NUP98 gene locates at 11p15 and encodes the nup98 (nucleoporin 98 kDa) protein, a mobile component of the nuclear pore, which involved in nucleocytoplasmic trafficking and transcriptionally active of chromatin. The partner genes of NUP98 is diverse, located at many chromosomes, among which homeobox genes are identified as the most common and important partners, such as NUP98-HOXA9, NUP98-HOXC13 and NUP98-HOXD11. Recently, we fortunately found the leukemia with NUP98 rearrangements represents a group AML similiar with the inv(3)(q21q26.2) which has distinct mutation spectrum and expression profile by exon capture sequencing and expression profile analysis in 56 cases with NUP98 rearrangements. There are many mutations of transcription factors and MECOM gene up-regulation. In addition, the biological and characteristics of NUP98 fusion gene in hematologic malignancies remains unclear. We plan to determine the role of Nup fusion genes in leukemogenesis using multiple in vivo and in vitro techniques, such as gene expression microarray, gene transfection, DNA editor, and animal models. This study will provide more details on the pathogenesis and target treatment in hematologic malignancies harboring NUP98 rearrangements.

11p15 重排是恶性血液病中常见的一种染色体易位， 可见于急性髓细胞白血病、急性淋巴细胞白血病、慢性髓细胞白血病急变及骨髓增生异常综合征中。受累基因为 NUP98，该基因编码蛋白为核孔蛋白复合体的重要组成部分，对手基因多变，以同源盒（ HOX）家族基因最为常见，如 NUP98-HOXA9、 NUP98-HOXC13和 NUP98-HOXD11等。申请人前期筛选到了56例伴NUP98重排病例，通过外显子测序和表达谱分析发现伴NUP98重排病例是一群具有独特的表达谱特征和突变图谱的AML，常伴有转录因子突变，MECOM基因的上调与inv(3)(q21q26.2)极为相似，本课题拟在前期工作基础上采用基因转染、基因编辑和小鼠动物模型等手段，从体内外两方面阐述伴NUP98重排白血病的疾病特点及致病机制，为深入理解该类疾病的发病机制、寻找新的靶向治疗提供理论和实验依据。

11p15/NUP98基因重排见于多种血液系统恶性肿瘤，尤其在急性髓系白血病（AML）中是最为常见。其基因组遗传学特征和发病机制尚未完全清楚。本项目通过多种组学研究以及体内外动物和细胞分子生物学实验研究从8000多例初诊恶性血液病患者中，筛选到79例11p15/NUP98基因重排患者，鉴定了19种NUP98融合伙伴，包括一例新NUP98融合伙伴基因HOXD8，其中以NUP98-HOXA9最为常见。通过靶向382个基因的外显子测序分析，发现其中93%（53/57）存在突变，而以N-RAS（33.3%）、FLT3-ITD（31.6%）、WT1（22.8%）、K-RAS（21.1%）、GATA2（21.1%）、RUNX1（17.5%）、EP300（15.8%）和FLT3-TKD（10.5%）的突变频率较高。且75.4%的突变为激活RAS/受体酪氨酸激酶（RTK）信号通路的基因突变，而66.7%的转录因子突变，包括GATA2。GATA2突变多位于C-末端锌指结构域，且突变体多影响GATA2的蛋白结构导致其与DNA的结合能力下降，导致突变体转录活性的下将，并在体外荧光素酶报告实验中得到证实。而且NUP98重排AML预后相对较差， 3年总体生存率只有18%，中位复发时间只需要6个月。表达谱分析结果显示NUP98重排AML中MECOM（EVI1）表达显著上调，并经定量PCR以及体外细胞实验得以证实，同时发现NUP98融合蛋白是通过其第二个FG重复结构域以及上调NF-kB信号通路来调节EVI1的表达。转基因小鼠实验证实过表达EVI1可以显著缩短NUP98重排（NUP98-HOXD13）白血病小鼠的总体生存时间。以上的结果提示EVI1是NUP98重排致白血病的机制之一。本研究结果系统阐述了NUP98重排致白血病的分子遗传学特征以及表达谱特征，为其精准诊断提供依据。并阐明其部分发病分子机制，为其靶向治疗提供了新的思路。