MTOR and breast cancer: Metformin can significantly enhance BC cell sensitivity to TNF-related apoptosis-inducing ligand (TRAIL) by inhibiting the mTOR/ribosomal protein S6 kinase B1 (S6K1) signaling pathway and then downregulating the expression of the cell-type FAS-associated death domain (FADD)-like interleukin-1β-converting enzyme (FLICE) inhibitory protein (c-FLIP), which significantly increases the apoptosis of BC cells.[71]