HOXA9 is required for survival in human MLL rearranged acute leukemias

Leukemias that harbor translocations involving the mixed lineage leukemia gene (MLL) possess unique biological characteristics and often have an unfavorable prognosis. Gene expression analyses demonstrate a distinct profile for MLL-rearranged leukemias with consistent high-level expression of select Homeobox genes including HOXA9. Here, we investigated the effects of HOXA9 suppression in MLL-rearranged and MLL-germline leukemias utilizing RNAi. Gene expression profiling after HOXA9 suppression demonstrated co-downregulation of a program highly expressed in human MLL-AML (this study) and murine MLL-leukemia (Krivtsov et al. 2006) stem cells including HOXA10, MEIS1, PBX3 and MEF2C. Our data indicates an important role for HOXA9 in human MLL-rearranged leukemias, and suggests targeting HOXA9 or downstream programs may be a novel therapeutic option. RNA was purified from t(9;11) MOLM-14 AML cells 44h after transduction in triplicates with 2 of the two most effective HOXA9shRNA constructs (3 x 1F3-HOXA9shRNA; 3 x 2A5-HOXA9shRNA) or GFP-controlshRNA (6x).