MTOR and breast cancer: Subsequently, we obtained paraffin sections from 58 breast cancer patients who received endocrine therapy and trastuzumab combined with sirolimus or everolimus, an mTOR inhibitor approved for the treatment of metastatic renal cell carcinoma and breast cancer patients,[21a] and performed IHC staining to analyze the relationship between the cytoplasmic level of MTA1 and the response to mTOR inhibitors.