FLT3/ITD突变-HIF1α-DNA甲基化环路诱导AML复发耐药的新机制

Acute myeloid leukemia (AML) patients with FLT3/ITD mutation tend to have a higher risk of drug resistance and relapse, and have a poor prognosis. Effective treatments are still not available in current clinical practice. Clarify the mechanisms of drug resistance and relapse and develop molecular targeted therapies will contribute to improve the efficacy of treatment and the prognosis of patients. We have recently reported a new mechanism that hypoxia inducible factor (HIF) 1α promotes leukemogenesis through inducing DNA methylation. However, its relationship to the drug resistance and relapse in FLT3/ITD AML remains unclear. We conducted preliminary experiments and found that the silence of FLT3/ITD gene expression led to inhibition of HIF1α level, DNA methylation, and leukemia cell proliferation. We therefore hypothesize that DNA methylation through FLT3/ITD-mediated HIF1α activation leads to gene expression silence of tumor suppressors targeting FLT3 and HIF1α, and thereby induces drug resistance and relapse in AML. The present study is designed to demonstrate the regulatory circuit among FLT3/ITD, HIF1αand DNA methylation, investigate the correlation between the aberrant methylation pattern and relapse of FLT3/ITD AML, and test the therapeutic effect of combined targeting inhibition of FLT3/ITD and HIF1αon drug resistance in leukemia. The results will provide mechanistic insights to leukemia relapse and drug resistance from a new angle of genetic/epigenetic interaction and important guide for new targeting therapeutic strategies.

伴FLT3/ITD基因突变的急性髓细胞白血病（AML）患者易耐药复发，预后差，临床尚无有效治疗手段。阐明耐药复发机制、开展分子靶向治疗，对提高疗效、改善患者预后有重要意义。我们最近报道了缺氧诱导因子（HIF）1α诱导DNA甲基化促进白血病发生的新机制，但其与FLT3/ITD AML耐药和复发的关系尚不清楚。我们前期实验发现，沉默FLT3/ITD能抑制HIF1α表达、DNA甲基化及白血病细胞增殖，因此设想FLT3/ITD通过活化HIF1α诱导DNA甲基化，使调控FLT3、HIF1α的抑癌基因被沉默，促进AML耐药复发。本项目拟阐明FLT3/ITD、HIF1α、DNA甲基化三者间的调控环路，观察异常甲基化模式与FLT3/ITD AML复发的关系，验证联合靶向抑制FLT3和HIF1α对耐药白血病的疗效。研究结果有助于从遗传学/表观遗传学交互作用的新视角认识白血病复发耐药机制、开发靶向治疗新策略。

伴FLT3/ITD基因突变的急性髓细胞白血病（AML）患者易耐药复发，预后差，临床尚无有效治疗手段。阐明其分子机制、开展靶向治疗有助于提高疗效、改善患者预后。我们报道了缺氧诱导因子（HIF）1α诱导DNA甲基化促进白血病发生的新机制，但其与FLT3/ITD AML耐药复发的关系未明。本项目发现：1、沉默FLT3/ITD能通过抑制AML细胞HIF1α进而抑制DNA甲基转移酶表达，诱导DNA去甲基化；与FLT3野生型AML相比，抑制HIF1α能更显著的抑制FLT3/ITD AML细胞体外增殖能力并诱导细胞凋亡；故HIF1α-DNA甲基化通路在调控FLT3/ITD AML恶性生物学行为中的起关键作用。2、应用靶向二代基因组测序技术，对初治、难治、复发AML患者基因突变谱分析显示，难治AML患者FLT3/ITD突变频率高于初治AML患者，初治AML患者携带FLT3/ITD时诱导缓解率低，FLT3/ITD、NPM1、DNMT3A三基因突变的初治患者生存率低；故FLT3/ITD AML患者易出现耐药，FLT3/ITD、NPM1和DNMT3A三基因突变的AML初治患者预后差。3、FLT3/ITD抑制剂索拉非尼治疗可提高难治FLT3/ITD AML患者缓解率；异基因外周血造血干细胞移植后应用去甲基化联合预防性供者淋巴细胞输注治疗，可降低FLT3/ITD AML早期复发风险；故靶向抑制DNA甲基化和FLT3/ITD对AML有治疗和预防复发的作用。本项目验证了FLT3/ITD、HIF1α、DNA甲基化三者间的调控关系，明确了FLT3/ITD与AML难治复发的关联，验证了靶向抑制FLT3/ITD和DNA甲基化对AML的疗效。研究结果有助于从遗传学/表观遗传学交互作用的新视角认识白血病复发耐药机制、开发靶向治疗新策略。