Importantly, the combination of metformin with sitagliptin showed a greater reduction in the number of metastatic lung nodules than treatment with metformin or sitagliptin alone.10 In the mouse xenograft model with papillary thyroid cancer, sitagliptin use was associated with reduced tumor growth, with the transforming growth factor‐β signaling pathway being potentially involved.5 In contradiction to these findings, Wang et al11 demonstrated in an in‐vivo study that use of DPP4 inhibitors increased the risk of metastasis in colon, hepatic, lung, ovary, and melanoma cell lines. This evidence concerns the gene DPP4 and melanoma.