These findings indicate that resistance to CCI-007 within the broad leukemia panel is brought about by different mechanisms for MLL-r and MLL-wt leukemia cells and indeed, the expression levels of HOXA9, MEIS1, CMYC and BCL2 responded differently upon CCI-007 treatment of sensitive MLL-r versus resistant MLL-r and resistant wt-MLL leukemia cells. The gene discussed is MEIS1; the disease is leukemia.