In one hallmark study of mammary tumor-type etiology, primary epithelia from breast reductions were dissociated then transduced with lentiviral vectors that expressed either (i) mutant p53, cyclin D1, K-ras, and myristolated PI3K, or (ii) SV40 and K-ras, then were sorted into EpCAM+ or CD10+ subpopulations prior to orthotopic injection into mouse hosts (Keller et al., 2012). This evidence concerns the gene KRAS and breast cancer.