IL18 and melanoma: IL-18 is expressed and secreted by immune cells and directly activates NK cells by regulating interferon (IFN)-γ promoter activity [5, 6]; however, in some cancers, such as melanoma and pancreatic cancer, IL-18 is secreted, and high levels of serum IL-18 are correlated with poor prognosis in multiple cancer types [7, 8].