Inhibiting CDK9 or CDK12/13 induced the rapid downregulation of the short-lived, anti-apoptotic Bcl-2 proteins Mcl1 and A1/Bfl1 in Jurkat leukemia cells and SUDHL1 lymphoma cells, whereas the expression of Bcl-2 and Bcl-xL remained unaffected. This evidence concerns the gene BCL2 and leukemia.