Deletion of the Hoxa Cluster in MLL-AF9 Is Incompatible with Leukemia Maintenance: RNAseq-based Quantitative Analysis of Wild Type and Hoxa-del Transcriptomes

High HOXA expression correlates with poor clinical outcome in AML, particularly those harboring MLL rearrangements (MLLr). The necessity of the HOXA cluster for the maintenance of MLLr-leukemia has not been elucidated. Primary leukemias were generated by transduction of MLL-AF9 (MA9) into hematopoietic stem and progenitor cells from compound Cre responsive transgenic mice for conditional deletion of the Hoxa locus. Hoxa deletion resulted in reduced proliferation, colony formation and repopulating ability in transplanted mice in which surviving leukemic cells retained at least one copy of the Hoxa cluster (Hoxa-del). Comparative RNA-seq analysis of leukemic MA9-Hoxa-wild type (WT) and MA9-Hoxa-del cells identified a unique gene signature. RNA profiles obtained from leukemic (MA9) stem and progenitor cells in wild type (WT), Hoxa cluster floxed (Hoxa-flox) or Hoxa cluster deleted (Hoxa-del) backgrounds.

HOXA基因高表达与急性髓系白血病（Acute Myeloid Leukemia, AML）患者的不良临床结局显著相关，尤其在携带MLL重排（MLL rearrangements, MLLr）的AML患者中。目前，HOXA基因簇对于维持MLLr白血病存活的必要性尚未阐明。本研究通过将MLL-AF9（简称MA9）转导至可条件性敲除Hoxa基因座的复合Cre响应转基因小鼠的造血干细胞和祖细胞中，构建原代白血病模型。Hoxa基因座敲除后，移植小鼠体内的白血病细胞增殖能力、集落形成能力及重建造血能力均出现下降，且存活的白血病细胞至少保留一个Hoxa基因簇拷贝（Hoxa-del）。对白血病MA9-Hoxa野生型（Wild Type, 简称WT）细胞与MA9-Hoxa-del细胞进行比较RNA测序（RNA-seq）分析，成功鉴定出一组独特的基因特征谱。本研究同时获取了野生型（WT）、Hoxa基因簇loxP侧翼（Hoxa-flox）或Hoxa基因座敲除（Hoxa-del）背景下的白血病（MA9）干细胞及祖细胞的RNA表达谱。