CHEK1 and acute lymphoblastic leukemia: Recently, we published on the effectiveness of targeting CHK1/CHK2 kinase as a single agent in ALL models [29] and based on that, the most sensitive (RPMI-8402) and the less sensitive (NALM-6) cell lines to the CHK1/CHK2 inhibitor PF-00477736 were selected as models for the present study.