CDK4 and acute lymphoblastic leukemia: Four genes (two upregulated, PLK3 and GADD45a; two downregulated, Chk2 and CDK4), which have been chosen on their biological relevance in the Chk1 pathway, were validated on B-/T-ALL cell lines treated for 24 h with or without PF-00477736 (IC50) (Additional file 1: Figure S8-C).