The p53fl/fl;myr-p110αwt/fl mammary tumors also displayed significantly increased total protein levels of p85α (1.9-fold), PTEN (1.3-fold) and p-PTEN (1.7-fold; Figures 1e and f), suggesting naturally occurring negative feedback mechanisms to inhibit abnormal PI3K activity driven by myr-p110α. Here, PIK3CA is linked to breast cancer.