CDK1 and breast cancer: In breast cancer cells, features of cell cycle arrest induced by cannabinoid treatment include blockade of the G1/S transition through downregulation of cyclin-dependent kinase 1 (CDK1), induction of p21 [49], or induction of p27kip1, decrease in cyclin (CCN) A and E, degradation of cell division cycle 25 A (CDC25A) and inactivation of CDK2 [50].