KMT2A::MLLT3 acute myelomonocytic leukemia (AML) comes in two clinically and biologically different subtypes. One is characterized by inferior outcome, older age, and MECOM oncogene expression. The other is mainly observed in children and young adults, associates with better clinical outcome, but lacks MECOM. To identify cell fate determining transcription factors downstream of KMT2A::MLLT3, we applied a bioinformatic algorithm that integrates gene and enhancer expression from primary MECOM-positive and -negative KMT2A::MLLT3 AML samples. This identified MECOM to be most influential in the MECOM-positive group, while neuronal transcription factor HMX3 was most influential in the MECOM-negative group. In large AML cohorts, HMX3 expression associated with a unique gene expression profile, younger age (p < 0.002) and KMT2A-rearranged and KAT6A-CREBBP leukemia (p < 0.00001). HMX3 was not expressed in other major genetic risk groups and healthy blood cells. RNA-sequencing analyses following forced HMX3 expression in healthy CD34+ cells and its silencing in KMT2A::MLT3 cells showed that HMX3 drives cancer-associated E2F and MYC gene programs (p < 0.001). HMX3 expression in healthy CD34+ cells blocked monocytic but not granulocytic colony formation. Strikingly, HMX3 silencing in KMT2A::MLLT3 patient cells resulted in cell cycle arrest, monocytic differentiation and apoptosis. Thus, the neuronal transcription factor HMX3 is a leukemia-specific vulnerability in KMT2A::MLLT3 AML.

KMT2A：：MLLT3 急性粒单核细胞白血病 （AML） 有两种临床和生物学上不同的亚型。一种的特点是结果较差、年龄较大和 MECOM 癌基因表达。另一种主要见于儿童和年轻人，临床结局较好，但缺乏 MECOM。为了确定 KMT2A：：MLLT3 下游决定转录因子的细胞命运，我们应用了一种生物信息学算法，该算法整合了来自原发性 MECOM 阳性和阴性 KMT2A：：MLLT3 AML 样本的基因和增强子表达。这确定 MECOM 在 MECOM 阳性组中最具影响力，而神经元转录因子 HMX3 在 MECOM 阴性组中最具影响力。在大型 AML 队列中，HMX3 表达与独特的基因表达谱、年龄较小 （p < 0.002） 和 KMT2A 重排和 KAT6A-CREBBP 白血病 （p < 0.00001） 相关。HMX3 在其他主要遗传风险组和健康血细胞中不表达。在健康 CD34+ 细胞中强制表达及其在 KMT2A：：MLT3 细胞中沉默后的 RNA 测序分析表明，HMX3 驱动癌症相关的 E2F 和 MYC 基因程序 （p < 0.001）。HMX3 在健康 CD34 + 细胞中的表达阻断了单核细胞而非粒细胞集落的形成。引人注目的是，KMT2A：：MLLT3 患者细胞中的 HMX3 沉默导致细胞周期停滞、单核细胞分化和细胞凋亡。因此，神经元转录因子 HMX3 是 KMT2A：：MLLT3 AML 中的白血病特异性脆弱性。