Among them, mitogen‐activated protein kinase 4 (MAP4K4) was identified, which is a serine/threonine protein kinase and has been reported to play a critical role in inflammation, cardiovascular diseases, and cancer.[25, 26, 27] Importantly, MAP4K4 contributes to tumorigenesis and tumor progression.[25, 28] To validate the proteomic results, we determined the protein levels of MAP4K4 in stable PEPT1‐overexpressing and PEPT1‐knockdown cell lines. Here, SLC15A1 is linked to cancer.