In contrast, the 232-gene breast cancer signature and the 108-gene cell cycle pathway have a 25-gene overlap including several cyclins (cyclin B1, B2, D1, E1, E2), cyclin-dependent kinases (CDK2, CDK4), tumor suppressors p53 and RB1, and the proliferation marker Ki-67, suggesting that predictive power of the control breast cancer signature may be due to the presence of these cell cycle related genes. This evidence concerns the gene CCNB1 and breast cancer.