HIF1a通过调控RNA甲基化(m6A)活化KIT通路促进AML发生的新机制

The KIT mutated patients with t(8;21) acute myeloid leukemia (AML) have a poor prognosis. Hypoxia inducible factor 1a (HIF1a) was highly expressed in t(8;21) AML. Our preliminary results showed that downregulation of HIF1a expression could inhibit the expression of KIT and cellular proliferation. But the underlying mechanism remains unknown. Wilms’ tumor 1-associating protein (WTAP), a key regulatory subunit of the RNA N6-methyladenosine (m6A) methyltransferase, has a close relationship with leukemogenesis. We found that WTAP mRNA expression in t(8;21) AML patients was positively correlated with the mRNA expression levels of HIF1a and KIT, suggesting a potential regulatory relationship among these genes. Because WTAP was selectively up-regulated in t(8;21) AML and correlated with a poor prognosis, we hypothesized that HIF1a facilitated to drive the occurrence of t(8;21) AML by governing WTAP-mediated RNA methylation program and its downstream KIT signaling pathway..The present study was designed to demonstrate the molecular interaction between HIF1a and WTAP-m6A in regulating KIT activation, investigate a potential mechanistic pathway linking aberrant RNA methylation pattern and leukemia occurrence, 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 occurrence of t(8;21) AML and developing new therapeutic targets.

携带KIT突变的t(8;21)AML预后不良，我们前期发现抑制t(8;21)AML中异常高表达的缺氧诱导因子1a（HIF1a）能抑制KIT表达及细胞增殖，机制未明。Wilms’瘤1-关联蛋白（WTAP）是关键的RNA甲基化（m6A）修饰酶之一，与白血病发生关系密切。我们发现，t(8;21)AML患者中WTAP分别与HIF1a、KIT基因表达呈正相关，故三者之间可能存在调控关系；且由于WTAP高表达的t(8;21)AML患者生存期短，我们设想HIF1a可能通过调控WTAP介导的RNA甲基化分布间接活化KIT信号通路促进白血病发生。.本项目拟阐明HIF1a通过WTAP-m6A激活KIT信号通路的分子网络，分析异常RNA甲基化分布促进白血病发生的潜在机制，观察靶向药物对上述通路异常活化的抑制效应。研究结果有助于加深对t(8;21)AML发病机制的认识，也为开发治疗新靶点提供实验基础和理论依据。

缺氧诱导因子1a（HIF1a）在携带t(8;21)染色体易位的急性髓系白血病（AML）中异常高表达，并通过促进DNA甲基转移酶3a表达而导致DNA高甲基化，进而发挥致癌基因的功能。然而，目前尚不清楚HIF1a是否影响RNA N6-甲基腺苷（m6A）甲基转移酶的表达。在本研究中，我们发现HIF1a促进了Wilms肿瘤1相关蛋白（WTAP）的表达，而WTAP是m6A甲基转移酶复合体的主要组分。WTAP的高表达显著改变了t(8;21) AML中转录组范围内m6A的分布并促进了AML细胞的增殖。首先，WTAP在t(8;21) AML患者中过表达并预示预后不良。其次，敲低WTAP可以抑制白血病细胞生长，诱导白血病细胞凋亡和分化。在机制上，HIF1a通过直接结合WTAP启动子区域的缺氧反应元件来激活WTAP基因表达。靶向沉默HIF1a-WTAP调控轴可使赖氨酸去甲基化酶4B（KDM4B）转录本上的m6A水平降低，从而促进KDM4B mRNA降解。因此，HIF1a介导的WTAP高表达通过可能通过促进m6A依赖的KDM4B翻译增强了白血病细胞的恶性行为。本研究结果有助于加深对t(8;21) AML发病机制的认识，也为开发治疗新靶点提供实验基础和理论依据。