ANPEP and cancer: In laboratory research, APN has reportedly exhibited an anti-cancer effect through anti-proliferative action and insulin resistance.5 In the low concentration range, APN might exert an anti-cancer effect as the concentration increases, whereas in the high concentration range, a higher concentration of APN might indicate APN resistance that eventually leads to compensatory upregulation and an increased risk of death.13,21,31 A direct effect of APN on cancer prognosis might be considered,22 but further studies are needed.