All mammary cancers that developed in diverse genetically engineered mouse models as well as a subset of human breast cancer cell lines and primary breast cancers exhibited a much higher expression of AKT1m. AKT1 is generally viewed as a persistently active house-keeping gene, but the existence of an alternative promoter within this gene locus may provide a mechanism by which the levels of AKT1 can be temporally and spatially regulated at particular physiological states, such as cancer, where a heightened activity of this kinase is required. Here, AKT1 is linked to breast cancer.