AML1-ETO与HIF1a协同调控DNA甲基化促进AML发生/复发的新机制

Although patients with t(8;21) AML have a relatively good prognosis, relapse remains the commonest cause of treatment failure. DNA methylation signatures can identify biologically distinct AML subtypes and predict prognosis. Our results also showed that t(8;21) AML is associated with specific methylation profiles. As AML1-ETO, a fusion protein generated from chromosomal translocation t(8;21), alone is not sufficient to induce leukemogenesis, we hypothesized that AML1-ETO drove the occurrence and relapse of AML by governing DNA methylation program. Hypoxia inducible factor 1a (HIF1a) is a transcription factor which is positively associated relapse in multiple solid tumor types. Our preliminary results showed that HIF1a was selectively up-regulated in t(8;21) AML and correlated with a poor prognosis. AML1-ETO and HIF1a probably constituted a reciprocal regulation loop and thereby increased global DNA methylation..The present study was designed to demonstrate the cooperative nature between AML1-ETO and HIF1a in regulating DNA methylation, investigate a potential mechanistic pathway linking aberrant DNA methylation and leukemia occurrence and relapse, and test the efficiency of targeted agents on blocking the above-mentioned pathway. The results would provide the theoretical and experimental foundation for better understanding the mechanisms of AML occurrence and relapse, and developing new therapeutic targets.

尽管t(8;21)急性髓细胞白血病（AML）患者预后相对较好，复发仍然是导致治疗失败的关键。DNA甲基化谱可区分不同AML亚型并提示预后，我们研究也发现t(8;21) AML呈独特的DNA甲基化模式。由于t(8;21)产生的AML1-ETO融合蛋白不能单独引发白血病，我们设想AML1-ETO可能通过调控DNA甲基化促进白血病发生/复发。缺氧诱导因子1a（HIF1a）是与多种实体瘤复发相关的转录因子，我们前期研究证实HIF1a在t(8;21) AML中选择性高表达，并与患者预后不良相关，AML1-ETO与HIF1a可能互为调控并可促进DNA甲基化。.本项目拟阐明AML1-ETO与HIF1a协同调控DNA甲基化的分子网络，分析异常DNA甲基化与AML发生/复发的关系，观察靶向药物对上述通路异常活化的抑制效应。研究结果有助于深入认识AML发生/复发机制，也为开发治疗新靶点提供实验基础和理论依据。

尽管t(8;21)急性髓细胞白血病（AML）患者预后相对较好，复发仍然是导致治疗失败的关键。DNA甲基化谱可区分不同AML亚型并提示预后，我们研究也发现t(8;21) AML呈独特的DNA甲基化模式。由于t(8;21)产生的AML1-ETO融合蛋白不能单独引发白血病，我们设想AML1-ETO可能通过调控DNA甲基化促进白血病发生。缺氧诱导因子1a（HIF1a）是与多种实体瘤复发相关的转录因子，我们前期研究证实HIF1a在t(8;21) AML中选择性高表达，并与患者预后不良相关，AML1-ETO与HIF1a可能互为调控并可促进DNA甲基化。本项目研究了AML1-ETO与HIF1a协同调控DNA甲基化的分子网络，分析了异常DNA甲基化与AML发生的关系，观察了靶向药物对上述通路异常活化的抑制效应。结果发现，AML1-ETO与HIF1a之间的相互作用能够促进白血病细胞增殖，HIF1a在AML1-ETO阳性AML患者中高表达并与患者预后不良相关，且其对预后的影响不依赖于基因突变的存在。在白血病细胞中共表达AML1-ETO与HIF1a能够促进白血病细胞的体外和小鼠模型体内的增殖能力。机制研究发现，AML1-ETO与HIF1a之间存在正反馈调控环路，二者协同活化DNA甲基转移酶3a（DNMT3a），促进DNA高甲基化。通过靶向药物或基因干扰AML1-ETO-HIF1a调控环路，能够导致DNA去甲基化，进而使因甲基化而被沉默的白血病抑癌基因p15INK4b再表达，同时白血病细胞的增殖受到抑制。因此，HIF1a高表达可作为AML1-ETO阳性AML患者的预后基因标记及潜在治疗靶点。本研究结果有助于深入认识AML发生机制，也为开发治疗新靶点提供实验基础和理论依据。