RAS-mutant AML LSCs originate from GMPs and drive clinical resistance to BH3 mimetics [ATAC-Seq]. RAS-mutant AML LSCs originate from GMPs and drive clinical resistance to BH3 mimetics [ATAC-Seq]

Cancer driver mutations often show distinct temporal acquisition patterns, but the biological basis for this, if any, remains unknown. RAS mutations occur invariably late in the course of acute myeloid leukemia (AML), upon progression or relapsed/refractory disease1-6. Here, by employing synthetic leukemogenesis in human cells, we first show that RAS mutations are obligatory late events that need to succeed earlier cooperating mutations. We provide the mechanistic explanation for this in a requirement for mutant RAS to specifically transform committed progenitors of the myelomonocytic lineage (granulocyte-monocyte progenitors, GMPs) harboring previously acquired driver mutations, revealing that advanced leukemic clones originate from a different cell type than more ancestral clones. Furthermore, we demonstrate that RAS-mutant leukemia stem cells (LSCs) give rise to monocytic disease, as frequently observed in patients with poor responses to treatment with the BCL2 inhibitor drug Venetoclax (VEN). We show that this is because RAS-mutant LSCs, in contrast to RAS-WT LSCs, have altered BCL2 family gene expression profiles and are resistant to VEN, driving clinical resistance and relapse with monocytic features. Our findings demonstrate that a specific genetic driver by imposing a specific LSC target cell restriction shapes the non-genetic cellular hierarchy of AML and critically impacts therapeutic outcomes in patients. Overall design: Synthetic leukemogenesis models in human iPSC-HSPCs and primary CB HSPCs

癌症驱动突变通常呈现出独特的时序获得模式，但其背后的生物学基础（若存在的话）仍未明确。RAS突变在急性髓系白血病（acute myeloid leukemia, AML）的病程中始终仅发生于晚期，且多见于疾病进展或复发/难治性阶段1-6。本研究通过在人类细胞中构建人工诱导白血病发生模型，首次证实RAS突变属于必需的晚期事件，其发生需依赖于此前已获得的协同突变。本研究针对该现象给出了机制层面的解释：突变型RAS需特异性转化携带有既往获得驱动突变的髓单核细胞系定向祖细胞（粒细胞-单核细胞祖细胞，granulocyte-monocyte progenitors, GMPs），由此揭示晚期白血病克隆的起源细胞类型与更早期的祖先克隆存在差异。此外，本研究证实携带RAS突变的白血病干细胞（leukemia stem cells, LSCs）可引发单核细胞系疾病，这一现象在BCL2抑制剂维奈克拉（Venetoclax, VEN）治疗应答不佳的患者中尤为常见。我们进一步揭示，相较于野生型RAS的白血病干细胞（LSCs），携带RAS突变的LSCs存在BCL2家族基因表达谱的改变，并对VEN产生耐药性，进而导致临床治疗耐药及伴单核细胞特征的疾病复发。本研究结果表明，特定的遗传驱动因子通过对LSCs的靶细胞范围施加特异性限制，塑造了急性髓系白血病的非遗传细胞层级结构，并对患者的治疗结局产生关键性影响。整体实验设计：在人类诱导多能干细胞-造血干祖细胞（induced pluripotent stem cell-hematopoietic stem and progenitor cells, iPSC-HSPCs）及原代脐带血造血干祖细胞（cord blood hematopoietic stem and progenitor cells, CB HSPCs）中构建人工诱导白血病发生模型。