MTOR and breast cancer: Regarding the pleiotropic effects of DPP-4 inhibitors on cancer biology, we have previously shown that DPP-4 suppression accelerates breast cancer metastasis by inducing EMT through C-X-C motif chemokine 12 (CXCL12)/C-X-C receptor 4 (CXCR4)-mediated mTOR activation [19].