激活 FLT3 和 RAS 突变通常发生在伴有 KMT2A 基因重排 (KMT2A-r) 的白血病中。然而，这些突变如何与 KMT2A-r 合作重塑表观遗传景观尚不清楚。使用由 KMT2A::MLLT3 驱动的逆转录病毒急性髓系白血病 (AML) 小鼠模型，我们发现 FLT3 ITD 、 FLT3 N676K 和 NRAS G12D 重塑了染色质可及性景观和相关转录网络。尽管激活突变共享染色质变化的共同核心，但每个突变都表现出独特的特征，其中大多数开放峰与内含子或基因间区域的增强子相关。具体来说，FLT3 N676K 和 NRAS G12D 重新连接了类似的染色质和转录网络，与 FLT3 ITD 介导的网络不同。基序分析揭示了 AP-1 转录因子家族在带有 FLT3 N676K 和 NRAS G12D 的 KMT2A::MLLT3 白血病中的作用，而 Runx1 和 Stat5a/Stat5b 在 FLT3 ITD 存在时活跃。此外，在表达 NRAS G12D 或 FLT3 N676K 的 KMT2A-r AML 中，与免疫细胞调节相关的转录程序被激活，并且 KMT2A-r 细胞上 NKG2D 配体的表达使它们对 CAR T 细胞介导的杀伤敏感。通过组蛋白脱乙酰酶抑制剂 LBH589（帕比司他）治疗，人 KMT2A-r AML 细胞可以在药理学上对 NKG2D-CAR T 细胞敏感，从而导致 NKG2D 配体水平上调。 LBH589 和 NKG2D-CAR T 细胞共同治疗可实现强有力的 AML 细胞杀伤，并且在表达 NRAS G12D 的细胞中观察到最强的效果。最后，结果得到验证并扩展到婴儿期急性白血病。综合起来，激活突变会诱导表观遗传景观中的突变特异性变化，从而导致由特定转录因子网络精心策划的转录程序发生变化。© 2024 作者。约翰·威利 (John Wiley) 出版的 HemaSphere

Activating FLT3 and RAS mutations commonly occur in leukemia with KMT2A-gene rearrangements (KMT2A-r). However, how these mutations cooperate with the KMT2A-r to remodel the epigenetic landscape is unknown. Using a retroviral acute myeloid leukemia (AML) mouse model driven by KMT2A::MLLT3, we show that FLT3 ITD , FLT3 N676K , and NRAS G12D remodeled the chromatin accessibility landscape and associated transcriptional networks. Although the activating mutations shared a common core of chromatin changes, each mutation exhibits unique profiles with most opened peaks associating with enhancers in intronic or intergenic regions. Specifically, FLT3 N676K and NRAS G12D rewired similar chromatin and transcriptional networks, distinct from those mediated by FLT3 ITD . Motif analysis uncovered a role for the AP-1 family of transcription factors in KMT2A::MLLT3 leukemia with FLT3 N676K and NRAS G12D , whereas Runx1 and Stat5a/Stat5b were active in the presence of FLT3 ITD . Furthermore, transcriptional programs linked to immune cell regulation were activated in KMT2A-r AML expressing NRAS G12D or FLT3 N676K , and the expression of NKG2D-ligands on KMT2A-r cells rendered them sensitive to CAR T cell-mediated killing. Human KMT2A-r AML cells could be pharmacologically sensitized to NKG2D-CAR T cells by treatment with the histone deacetylase inhibitor LBH589 (panobinostat) which caused upregulation of NKG2D-ligand levels. Co-treatment with LBH589 and NKG2D-CAR T cells enabled robust AML cell killing, and the strongest effect was observed for cells expressing NRAS G12D . Finally, the results were validated and extended to acute leukemia in infancy. Combined, activating mutations induced mutation-specific changes in the epigenetic landscape, leading to changes in transcriptional programs orchestrated by specific transcription factor networks.© 2024 The Author(s). HemaSphere published by John Wiley & Sons Ltd on behalf of European Hematology Association.