CDK4 and leukemia: SU9516 is 3-substituted indolinone reported to bind and selectively inhibit CDK2/Cyclin A and CDK2/Cyclin E activities, as well as CDK1/Cyclin B in an ATP-competitive fashion, but CDK4/Cyclin D1 in an ATP-non-competitive fashion, yet with 45 fold reduced potency compared to CDK2/Cyclin A. SU9516 induces apoptosis in colon carcinoma cells and kills human leukemia cells through inhibition of RNA Pol II CTD phosphorylation [325,326].