CDK4 and neoplasm: Moreover, the cell cycle is an essential factor of cell growth; the cell cycle is regulated by complexes of cyclins and cyclin-dependent kinases during cell division (Lim and Kaldis, 2013), Cyclin D1 (Liu Y. et al., 2016), CDK1, CDK2, and CDK4 are often upregulated in tumor cells (Lee et al., 2011; Cho and Park, 2013).