MTOR and breast cancer: Carracedo et al. simultaneously reported that combined MEK and mTOR inhibition was also effective in tumor xenografts generated using the PTEN-competent breast cancer cell line MCF7; however, the increase in apoptotic index and the decrease in the percentage of Ki67-positive cells in the combined treatment group was barely additive, as compared with PD0325901- and Everolimus- single-treatment groups, in such PTEN wild-type context24.