De novo activating mutations drive clonal evolution and enhance clonal fitness in KMT2A-rearranged leukemia

Activating signaling mutations are common in acute leukemia with KMT2A (previously MLL) rearrangements (KMT2A-R). These mutations are often subclonal and their biological impact remains unclear. Using a retroviral acute myeloid mouse leukemia model, we demonstrate that FLT3ITD, FLT3N676K, and NRAS G12D accelerate KMT2A-MLLT3 leukemia onset. Subclonal FLT3N676K mutations also accelerate disease, possibly by providing stimulatory factors such as Mif. Acquired de novo mutations in Braf, Cbl, Kras, and Ptpn11 were identified in KMT2A-MLLT3 leukemia cells and favored clonal expansion. During clonal evolution, serial genetic changes at the KrasG12D locus was observed, consistent with a strong selective advantage of additional KrasG12D. KMT2A-MLLT3 leukemias with signaling mutations enforced Myc- and Myb transcriptional modules. Our results provide new insight into the biology of KMT2A-R leukemia with subclonal signaling mutations and highlights the importance of activated signaling as a contributing driver in this disease. mRNA sequencing of KMT2A-MLLT3 leukemias with or without activating mutations generated using Illumina NextSeq 500.

KMT2A（既往称MLL）重排（KMT2A-R）型急性白血病中，激活型信号突变较为常见。这类突变常呈亚克隆状态，其生物学效应迄今尚未明确。本研究采用逆转录病毒构建的小鼠急性髓系白血病模型，证实FLT3ITD、FLT3N676K及NRAS G12D可加速KMT2A-MLLT3白血病的发病进程。亚克隆型FLT3N676K突变同样可促进疾病进展，其机制可能与分泌Mif等促增殖因子相关。研究人员在KMT2A-MLLT3白血病细胞中鉴定出Braf、Cbl、Kras及Ptpn11的新发获得性突变，上述突变可推动克隆扩增。在克隆进化过程中，观察到KrasG12D位点发生一系列遗传改变，这与额外KrasG12D突变所带来的显著选择优势相符。携带信号突变的KMT2A-MLLT3白血病可强化Myc与Myb转录调控模块。本研究结果为携带亚克隆信号突变的KMT2A-R白血病的生物学特性提供了全新见解，并凸显了激活型信号通路作为该病致病驱动因素的重要性。本研究通过Illumina NextSeq 500平台，对携带或不携带激活突变的KMT2A-MLLT3白血病细胞完成了mRNA测序。