Here, we review recent and notable experimental studies in this area with a special focus on this adaptive resistance phenomenon to kinase inhibitors targeting the phosphoinositide 3-kinases (PI3Ks)/AKT/mTOR and receptor tyrosine kinase (RTK)/rapidly accelerated fibrosarcoma (RAS)-MAPK signalling pathways in breast cancer (BC). The gene discussed is MTOR; the disease is breast cancer.