Prospects for cytokine and chemokine biotherapy

Cytokines with immunostimulating effects have the capacity to induce tumor immunity in animal models, whereas some cytokines interfere with tumor growth based on their angiostatic effects. Despite these capabilities, cytokines, such as IFN-α, IFN-γ, tumor necrosis factor, interleukin (IL)- 1, and IL-2, have had limited clinical efficacy and many undesirable side effects. In preclinical models, cytokines can even promote tumor growth and increase metastatic spread. Although chemokines have had limited clinical evaluation, studies of animal models show that they can also have tumor- suppressive or tumor-enhancing effects. In mice, chemokines, such as IP-10, RANTES, and TCA3, have resulted in tumor regression and immunity to subsequent tumor challenge. Those chemokines that are angiostatic (e.g., PF4, IP-10, and MIG) can also induce tumor regression by reducing the tumor blood supply. Conversely, IL-8, which is angiogenic, can promote tumor growth. Our studies show that nasopharyngeal cell line cells (FADU) show a chemotactic as well as a proliferative response to MCP-1. In addition, a variant murine T cell lymphoma cell line Esb-MP, unlike the parental variant Esb, was selectively chemoattracted by murine MCP-I/JE. When injected s.c. into mice, the Esb-MP variant metastasized to the kidney with much higher frequency than the Esb variant. Both cultured kidneys from normal mice and a mesangial cell line constitutively produced chemoattractants that acted on Esb-MP but not Esb parental cells. Purification to homogeneity of these chemoattractants led to the identification of RANTES and JE. These results demonstrate that some chemokines may promote tumor growth and organ-specific metastatic spread of those tumors that have adapted and become responsive to chemokines. Finally, tumors appear to use numerous adaptive mechanisms to subvert and suppress the immune system. More effective therapy with cytokines and chemokines will require better characterization of the means by which tumors develop resistance to cytokines and overcome the immune system. Only then can we develop appropriate therapeutic approaches to antagonize cancer-induced immunosuppression.