The Role of IL-15 in Human Cancer: Friend or Foe?

IL-15 is a member of the family of IL-2 cytokines. This family of cytokines activates signaling pathways leading to cellular activation, proliferation and survival. IL-15 exhibits broad activity and induces the differentiation and proliferation of NK, T and B cells. Furthermore, IL-15 protects T-effector cells from the action of T Regulatory cells and reverses tolerance to tumor associated antigens. Thus, IL-15 potentiates the immune system which is important in immunosurveillance against cancer. However, IL-15 may be also involved in the pathogenesis of hematological malignancies and mediates the processes of tumor progression and metastasis, becoming a growth factor for cancer cells. In pre-clinical studies, administration of IL-15 in several tumors potentiated antitumor effects alone or in combination with other anti-cancer treatments. To date, there are some phase I clinical trials to test the effective role of IL-15 in human cancer. Thus, according to its pleiotropic and wide involvement in human cancer pathogenesis, it is still under discussion if IL-15 will be friend or foe. The discussion of these issues is the aim of the present review.