KRAS and breast cancer: However, based on our data demonstrating that over-expression of activated KRAS in differentiating BC has no effect on expression of SOX2, SOX9 and multiple NOTCH pathway genes, we hypothesize that KRAS regulates differentiation of normal human adult BC into secretory and ciliated cells independent of FOXM1/WNT, SOX2/SOX9 and NOTCH signaling.