CDK4 and head and neck squamous cell carcinoma: In addition to breast cancer, melanoma, non-small cell lung cancers, lymphomas, ovarian cancers, and liposarcomas are currently being treated with CDK4/6 inhibitors in clinical trials [25-30], with two clinical trials in progress for SCCHN [NCT00824343; NCT00899054] using the CDK inhibitor P276-00 (predominantly targets CDK4, CDK2 and CDK9; [31]).