PTEN and breast cancer: Indeed, stratified trials are needed to develop biomarkers that can predict response to mTOR inhibition as well as other breast cancer treatments, and our results suggest that the same suggestion for future stratification in clinical trials holds for a variety of cancer types, e.g. the several tumor sample types which had mutations in both PIK3CA and PTEN genes and also displayed mTOR-pathway activation, and the higher percentages of PIK3CA mutations that were observed in colorectal-cancer samples with than without mTOR-pathway activation.