Here were evaluated the AEB071 (SotrastaurinTM) treatment efficiency of breast cancer cell lines derived from estrogen receptor positive (T-47D), estrogen/HER2 receptor positive (BT474), and triple negative (HCC1806) breast cancer cells under 2D (monolayer) and 3D (multicellular tumor spheroids) culture conditions. This evidence concerns the gene ESR1 and breast cancer.