Cyclin-dependent kinases (CDKs) 4 & 6 play a key in breast cancer. Cyclin D1-CDK4/6 complexes are critical regulators of the cell cycle transition from the G1 to S phase. To proceed through these phases, a cell must pass a restrictive checkpoint, tightly regulated in this case by the retinoblastoma tumor suppressor protein (Rb). Palbociclib is a small molecule kinase inhibitor that blocks Cyclin D1-CDK4/6 mediated phosphorylation of the Rb protein to prevent E2F driven transcription of genes that commit the cell to DNA replication and cell division.

In this application note, you will learn:

• The effect of palbociclib treatment in two breast cancer cell lines
• How to monitor the amount of phospho-Rb and Cyclin D1 protein levels with HTRF®^® immunoassays to examine the effect of CDK4/6 inhibition and Cyclin D1 regulation

For research use only. Not for use in diagnostic procedures.