Our recent finding showed that Saxagliptin (Sax) and Sitagliptin (Sit), two common antidiabetic dipeptidyl peptidase-4 inhibitors (DPP-4i) compounds, promoted murine BC 4T1 metastasis via a ROS–NRF2–HO-1 axis in nonobese diabetic–severe combined immunodeficiency (NOD-SCID) mice. The gene discussed is HMOX1; the disease is breast cancer.