Nar isolated from Thymus vulgaris upregulated pro-apoptotic markers, p18, p19, p21, Bax and Bak, and downregulated anti-apoptotic markers, Cdk4, Cdk6, Cdk7, and Bcl-2 in human colorectal and breast cancer cells leading to apoptosis (Abaza et al., 2015). Here, CDK4 is linked to breast cancer.