CCNE2 and breast cancer: Furthermore, we observed that CCNE2 was closely associated with cancer driver genes (AKT serine/threonine kinase 1 (AKT1) and KRAS proto-oncogene, GTPase (KRAS)) and high mutation frequency gene (tumor protein p53 (TP53) and phosphatase and tensin homolog (PTEN)) in breast cancer patients.