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. Overall design: 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.