Interestingly, it is apparent that SET-2 myeloproliferative disorder-derived megakaryoblastic leukemia cells expressing JAK2V617F undergo rapid ruxolitinib-mediated apoptosis (Geron et al. 2008; Wernig et al. 2008) as opposed to the mild suppression in cell growth seen in ruxolitinib-treated CRLF2/JAK2 mutant B-ALL cells that we demonstrated here. This evidence concerns the gene JAK2 and adult acute megakaryoblastic leukemia.