To biochemically characterize mammary tumors from p53fl/fl;KrasG12D and p53fl/fl;KrasG12D;myr-p110αwt/fl, we tested the PI3K pathway activation status of the mammary tumors by analyzing the levels of p110α, AKT, p-AKT, p85α, PTEN and p-PTEN. The gene discussed is PTEN; the disease is breast cancer.