Possible prognostic role of IL-17R in osteosarcoma. An intense vascularization of primary tumor mass is associated with a fatal outcome in various types of invasive solid tumors. Interleukin 17 (IL-17), a CD4+ T-cell-derived cytokine, stimulates some tumor cells to secrete angiogenic factors, among which venous endothelial growth factor (VEGF). We assessed whether the expression of IL-17 receptor (IL-17R) represents a marker for the metastasizing ability of osteosarcoma (OS), a very malignant bone tumor.We immunoassayed the amount of VEGF secreted by three OS cell lines expressing IL-17R in differing amounts: HOS, MG63 and U-2 OS, and their sensitivity to IL-17 stimulation to secrete VEGF.U-2 OS, which best expresses IL-17R, secreted the highest amounts of VEGF and was the most sensitive to IL-17, whereas MG63 expressed the lowest level of IL-17R, secreted the lowest amount of VEGF and was not sensitive to IL-17. IL-17R expression correlated with VEGF secretion and IL-17 sensitivity. U-2 OS expressed the most dedifferentiated phenotype, which is associated with tumor malignancy.These results suggest that IL-17R in OS might represent a marker of tumor metastasis potential.