Cytokines and their role in the activation of the immune response to tumors

Cytokines represent the major mediators of host defenses against infectious agents and tumors in that they control both innate and adaptive immunity, by regulating the communication between T cells, antigen-presenting cells and other immune cells in the course of an immune response. It is generally accepted that the cytokine repertoire present at the tumor site dictates the type of host response toward tumors. immunosuppressive cytokines secreted by tumor cells can impair the host antitumor response, whereas cytokines promoting the development of T cell-mediated immunity [especially those favoring the generation of a T helper 1 type of immune response) can induce or potentiate antitumor immunity. Systemic administration of some cytokines (especially IL-2 and interferon-alpha (IFN-alpha)] has been used with some success in the immunotherapy of certain cancer patients, even though some relevant side effects have been often observed. Recently, the local secretion of cytokines at the tumor site by gene transfer approaches has been regarded as an attractive and more physiological alternative to systemic administration of cytokines for the induction of a more effective antitumor immune response. As new activities of cytokines are being identified, the understanding of their role in the regulation of the complex interactions between tumor cells and immune system represents a crucial issue for the identification of a more effective and selective use of cytokines in the immunotherapy of cancer.