Because anti-estrogen therapy results in a reduction in cyclin D1 levels and p21Waf1/Cip1/p27Kip1-mediated inhibition of CDK2/1 activity, we sought to determine the ability of novel guanine-based CDK2/1 inhibitors NU2058 and NU6102 to target CDK2 and CDK1, and assess their therapeutic potential as alternatives to hormonal therapy in breast cancer. This evidence concerns the gene CDK1 and breast cancer.