CDK9 and B-cell chronic lymphocytic leukemia: 2 h of treatment of the cell lines HL-60 and MV4-11 (AML) and MEC-1 (CLL) did not affect the phosphorylation of CDK9 at T186 and RNAP II at S5; XIAP and BCL-2 levels but inhibited pS2 (EC50 < 100 nM), MCL-1 and cMYC levels, in a dose-dependent manner.