In contrast, whereas a 70 % decrease in S6 phosphorylation at Ser235/236 was observed in parental cell lines, a smaller 20 % decrease occurred in resistant cells (Fig. 1d; see also Additional file 1B) suggesting that sustained mTOR activity leads to BYL719 resistance in PIK3CA mutant breast cancer cells. The gene discussed is MTOR; the disease is breast cancer.