MTOR and cancer: TNBC frequently develop resistance to chemotherapy, which can be caused by different factors, including an increased expression of ATP-binding cassette (ABC) transporters, the existence of cancer stem cells, and the activation of multiple signaling pathways, such as the transforming growth factor-β (TGF-β), Notch, Wnt/β-Catenin, Hedgehog, hypoxia, nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), PI3K/AKT/mammalian target of rapamycin (mTOR) pathways, Janus Kinase (JAK)/signal transducer, and activator of transcription (STAT) pathways [99].