Restoration of tumor immunosurveillance via targeting of interleukin-13 receptor-α2

Abstract

In previous studies, we described a "counter-immunosurveillance" mechanism initiated by tumor-activated, interleukin-13 (IL-13)-producing natural killer T cells that signal Gr-1+ cells to produce transforming growth factor-β1 (TGF-β1), a cytokine that suppresses the activity of tumor-inhibiting cytolytic CD8+ T cells. Here, we show that in two tumor models (the CT-26 metastatic colon cancer and the 15-12RM fibrosarcoma regressor models), this counter-surveillance mechanism requires the expression of a novel IL-13 receptor, IL-13Rα2, on Gr-1intermediate cells, because downregulation of IL-13Rα2 expression or the activator protein-1 signal generated by the receptor via in vivo administration of specific small interfering RNA or decoy oligonucleotides leads to loss of TGF-β1 production. Furthermore, acting on prior studies showing that IL-13Rα2 expression is induced (in part) by tumor necrosis factor-α (TNF-α), we show that receptor expression and TGF-β1 production is inhibited by administration of a TNF-α-neutralizing substance, TNF-αR-Fc (etanercept). Taking advantage of this latter fact, we then show in the CT-26 model that counter-immunosurveillance can be inhibited, anti-CT-26-specific CD8+ cytolytic activity can be restored, and CT-26 metastatic tumor nodules can be greatly decreased by administration of TNF-αR-Fc. Corroborative data were obtained using the 15-12RM fibrosarcoma model. These studies point to the prevention of metastatic cancer with an available agent with already known clinically acceptable adverse effects and toxicity. ©2008 American Association for Cancer Research.