DHX9调控骨髓增生异常综合征(MDS)白血病转化的分子机制

RNA helicase DHX9 plays an important role in various biological processes such as DNA replication and gene transcription, and its abnormality is closely related to tumorigenesis in multiple cancers.However, the role of DHX9 in pathogenesis of myelodysplastic syndromes (MDS) is still unknown. Our previous work has shown that DHX9 was obviously overexpressed in MDS, and overexpression of DHX9 predicts high leukemic transformation. In in vitro experiments, knockdown of DHX9 significantly induces cell apoptosis and inhibits cell growth in MDS/leukemia cell lines. Integrated analysis of gene expression profile and bioinformation reveals that IGF1R-PI3K-AKT signaling pathway may be a critical target of DHX9. Based on these data, we speculate DHX9 as a potential oncogene. DHX9 induces apoptosis resistance and excessive proliferation through activation of IGF1R-PI3K-AKT signaling, and then drive MDS progression to leukemia. In this project, we will perform a series of experiments such as RNAi/ectopic expression, ChIP/ChIP-sequencing and cell functional assays to confirm our hypothesis. The purpose of this project is to investigate the molecular mechanism of DHX9 driving leukemia transformation in MDS, and to discuss the possibility of targeted intervention. Finally, this project can provide some novel findings in MDS pathogenesis and scientific evidence for novel targeted therapy.

RNA解螺旋酶DHX9调节DNA复制和基因转录，其功能异常促进肿瘤发生。然而，DHX9在MDS发病机制中的作用尚无报道。申请人前期研究显示MDS患者DHX9高表达预示着增加的白血病转化风险，DHX9敲低诱导MDS/白血病细胞增殖抑制和凋亡增加。进一步的基因表达谱及生物信息分析提示IGF1R-PI3K-AKT信号可能是DHX9的靶向。基于前期研究，申请人推测DHX9在MDS中作为一个原癌基因通过激活IGF1R-PI3K-AKT信号来诱导MDS克隆细胞的凋亡抵抗和过度增殖，进而推动疾病向白血病转化。本研究在前期工作基础上，采用病毒介导干扰/过表达、RNA-seq、ChIP/ChIP-seq技术以及细胞功能实验，探讨DHX9调控MDS白血病转化分子机制，探讨影响DHX9表达和功能的靶向干预价值。该项目有助于拓宽MDS疾病进展的机制研究，为拓展新的靶向治疗提供策略。

RNA解螺旋酶DHX9调节DNA复制和基因转录，其功能异常促进肿瘤发生。然而，DHX9在骨髓增生异常综合征(MDS)发病机制中的作用尚无报道。在本项目中，我们应用二代测序对 320 名 MDS 患者测序DHX9 突变，检测到 35名DHX9突变患者 (10.9%)。DHX9突变模式包括胚系(77.1%, 27/35)和体细胞突变(22.9%, 8/35)。 所有类型的DHX9突变少有与其他 RNA剪接基因突变共存。胚系DHX9突变很少与其他突变和异常核型共存，而体细胞 DHX9突变反之。与无DHX9突变的患者相比，具有DHX9突变的患者更可能被归类为较低风险亚组，具有更严重的全血细胞减少，并且具有更低的白血病转化。在体外试验中，DHX9抑制导致 MDS/白血病细胞系中G2/M期的细胞增殖减少、细胞凋亡增加和细胞周期停滞。基因表达谱 (GEP) 和功能实验表明，DHX9敲低激活了TP53/P21介导的细胞凋亡程序，同时抑制了IGF1R-PI3K-AKT介导的细胞增殖信号通路。此外，GEP和染色质免疫沉淀的综合分析显示DHX9对于BCL-2的转录激活是必不可少的，提示BCL-2可能是DHX9的靶点。该项目分析显示DHX9突变是MDS频繁发生的分子异常。由于DHX9功能丧失导致恶性克隆细胞无法增殖，这可能是MDS患者亚群中骨髓衰竭和白血病转化率降低的原因。这些研究探讨了DHX9在MDS发病机制中的作用，揭示了DHX9通过TP53/P21和IGF1R-PI3K-AKT信号通路调控克隆细胞生物学行为，丰富了MDS发病机制研究。