Paradoxical Roles of IL-4 in Tumor Immunity

Interleukin(IL)-4 is a crucial cytokine in tumor immunology.In the initial murine experiments,IL-4 exhibited potent anti-tumor ability.Tumors genetically modified to produce IL-4 were rejected,while parental tumors grew progressively.Mice rejected IL-4-producing tumors got long-lasting anti-tumor immunity.The comparative study showed that IL-4 induced the most effective immune response among several cytokines in both prophylactic and therapeutic models.All of these indicate IL-4 has strong potential as a tumor therapy agent.However,contrary evidence indeed exists,and is becoming more and more abundant which shows IL-4 is a tumor-promoting molecule.IL-4 amounts are usually elevated in human cancer patients.IL-4 knockout mice are more resistant to tumor challenge than IL-4 competent mice.Furthermore,tumor cells of various histological origins often express increased levels of IL-4 receptor in comparison to their normal counterparts.By carefully examining presently available data,we found the effects of IL-4 in tumor immunity are closely related to its sources,expressing time and dose,as well as the molecular and cellular environments.In this mini-review,we concentrate on illustrating the paradoxical roles and underlying mechanisms of IL-4 in tumor immunity and try to understand how one molecule has opposite effects.