CD34 and leukemia: Increased in response to imatinib (p210 human CD34+ model), MEK-inhibitor reduces proliferation, synergy with imatinib (40). No Mek inhibition currently in trials for leukemia, phase I study of sorafenib in relapsed leukemia completed (Raf-kinase inhibitor, also inh. VEGFR2/PDGFRβ, NCT00131989)