AKT1 and breast cancer: The differential activation of the PI3K/AKT pathway exhibited by the ex vivo EGFP+ and EGFP− tumor cells thus clearly illustrates the phenotypic differences between these two ex-vivo derived populations of breast cancer cells localized in two different compartments of the TME, which is consistent with their corresponding CSC-like characteristic shown in Figs. 2, 3, 4 and 5.