In order to identify the basis of selectivity of CCI-007 towards a subgroup of MLL-r leukemia cell lines, baseline expression levels of important leukemia associated genes HOXA9, MEIS1, CMYC and BCL2 were determined by quantitative real-time RT-PCR and relative baseline expression levels were compared between CCI-007 sensitive and resistant cell lines. The gene discussed is MEIS1; the disease is leukemia.