Of the antidiabetic drugs, such as insulin, sulfonylureas, dipeptidyl peptidase-4 (DPP4) inhibitors, metformin (MET), and analogs of the insulinotropic GLP-1, the oral antidiabetic drug, MET (1,1-dimethylbiguanide), is the most promising therapeutic for the prevention and treatment of cancer in patients with diabetes, and as a stand-alone anticancer drug [216,217,218,219]. Here, DPP4 is linked to diabetes mellitus.