Tumor-associated macrophage related interleukin-6 in cerebrospinal fluid as a prognostic marker for glioblastoma.

Interleukin-6 (IL-6) is one of the pleiotropic cytokines and has received attention as a critical factor implicated in the invasion and the angiogenesis of various cancers. In glioma, IL-6 is known to be associated with the prognosis; however, the roles of IL-6 in cerebrospinal fluid (CSF) has not been studied sufficiently. We examined the concentration of CSF IL-6 using 75 CSF samples of glioma (54 glioblastomas (GBMs) and 21 other grades of gliomas) and analyzed the association CSF IL-6 with infiltration levels of tumor-associated macrophages (TAMs) and prognosis. The concentration of CSF IL-6 in GBM patients was significantly higher than that in other grades of gliomas. CSF IL-6 levels were associated with the infiltration rate of TAMs in GBMs, and IL-6 levels were increased in the GBM cells co-cultured with TAM-like macrophages. The CSF of GBM patients, which contained high concentration of IL-6, promoted the migration ability of GBM cells, and neutralization antibodies of IL-6 inhibited its migration ability. Finally, in both univariate and multivariate analysis, higher CSF IL-6 levels were associated with poorer prognosis in GBM patients. These results indicated that the concentration of CSF IL-6 is associated with TAMs' infiltration level and may be a useful prognostic biomarker for the GBM patients.