Tumor immune therapy: lessons from infection and implications for cancer - can IL-7 help overcome immune inhibitory networks?

The complexity that the immune system faces in distinguishing pathogens from self is manifested by the intricate immunological networks involved in initiation, promotion and abrogation of immunity. A substantially more complex algorithm is required to distinguish normal from aberrant self (e.g. in the form of cancers), and this is reflected by the apparent inefficiency of our immune system to eradicate tumors; however, with our expanding insights into the molecular networks that govern immunity, we can now consider therapies that transiently promote immunity and/or antagonize immune inhibitory networks. Cytokines that normally function to regulate immune responses hold much therapeutic promise in this regard. Translating this promise to tangible outcomes will require a thorough analysis of how, when and in what way these cytokines should be used to take advantage of synergistic and complementary effects of current cancer therapeutics. In this review, we focus on IL-7, as much data are emerging on the ability of this unique homeostatic cytokine to augment various anti-tumor immunotherapeutic modalities.