The acute myeloid leukemia associated AML1-ETO fusion protein alters the transcriptome and cellular progression in a single-oncogene expressing in vitro induced pluripotent stem cell based granulocyte differentiation model

Acute myeloid leukemia (AML) is characterized by recurrent mutations that affect normal hematopoiesis. The analysis of human AMLs has mostly been performed using end-point materials, such as cell lines and patient derived AMLs that also carry additional contributing mutations. The molecular effects of a single oncogenic hit, such as expression of the AML associated oncoprotein AML1-ETO on hematopoietic development and transformation into a (pre-) leukemic state still needs further investigation. Here we describe the development and characterization of an induced pluripotent stem cell (iPSC) system that allows in vitro differentiation towards different mature myeloid cell types such as monocytes and granulocytes. During in vitro differentiation we expressed the AML1-ETO fusion protein and examined the effects of the oncoprotein on differentiation and the underlying alterations in the gene program at 8 different time points. Our analysis revealed that AML1-ETO as a single oncogenic hit in a non-mutated background blocks granulocytic differentiation, deregulates the gene program via altering the acetylome of the differentiating granulocytic cells, and induces t(8;21) AML associated leukemic characteristics. Together, these results reveal that inducible oncogene expression during in vitro differentiation of iPS cells provides a valuable platform for analysis of aberrant regulation in disease.

急性髓系白血病（Acute myeloid leukemia, AML）以累及正常造血过程的复发性突变为主要特征。目前针对人类AML的研究分析大多采用终末样本，例如细胞系与携带额外促癌突变的患者来源AML样本。单一致癌性突变事件（例如AML相关癌蛋白AML1-ETO的表达）对造血发育以及向（白血病前期）恶性转化状态的分子调控效应，仍有待进一步研究。本研究介绍了一种诱导多能干细胞（induced pluripotent stem cell, iPSC）模型的构建与表征，该模型可体外诱导分化为单核细胞、粒细胞等不同成熟髓系细胞类型。本研究在体外分化过程中表达AML1-ETO融合蛋白，并在8个不同时间点检测了该癌蛋白对细胞分化的影响，以及基因表达程序的潜在调控变化。分析结果显示，在无额外突变的遗传背景中，AML1-ETO作为单一致癌性突变事件可阻断粒细胞分化，通过改变分化中粒细胞的乙酰化修饰组紊乱基因表达程序，并诱导出t(8;21)易位相关AML的白血病表型。综上，本研究结果表明，在iPSC体外分化过程中实现可诱导癌基因表达，可为疾病异常调控机制的研究提供极具价值的实验平台。