Keyomarsi et al., found that cyclin E expression plays a strong role in human breast cancer tumors and the cyclin E-CDK2 complex remains active throughout the cell-cycle suggesting the now established hypothesis that truncated (deregulated) cyclin E variants were responsible for the constitutive function of cyclin E-CDK2 in breast cancer tumors [72], [73]. The gene discussed is CCNE1; the disease is breast cancer.