MTOR and breast cancer: Increasing evidence suggests that abnormal activation of the phosphatidylinositol-3-kinase (PI3K), AKT, and mammalian target of rapamycin (mTOR) pathway is a frequent event in numerous malignant tumors, including prostate cancer [15], gastrointestinal cancer [16], breast cancer [17], non-small cell lung cancer [18], acute myeloid leukemia [19], and liver cancer [20].