CHEMBL3705960

In Vitro Assay: The Cdk4 and Cdk6 inhibitory activity of the compounds is measured with a kinase inhibition assay using recombinant Cdk4/CyclinD1 or Cdk6/CyclinD3 protein complexes. The protein substrate used in the assay is the retinoblastoma protein (Rb). The kinase reactions are carried out in a 96-well filter plate (MSDV N6B50, Millipore). Compounds are serially diluted in kinase buffer (20 mM Tris-HCl, pH 7.4, 50 mM NaCl, 1 mM DTT, 1 mg/ml BSA) and added to the reaction mixture containing 2.5 ng/ml Cdk4/CyclinD1 or Cdk6/CyclinD3, 25 μM ATP, 10 μCi/ml [33P]-ATP, 0.1 μg/ml Rb in the kinase buffer. The mixture is incubated at room temperature for 1 hour and the proteins precipitated with an equal volume of 20% TCA. The plates are washed with 10% TCA according to the manufacturer's instruction and dried at room temperature. The amount of the phosphorylated Rb is determined with a TopCount (PerkinElmer).