IL6 and glioblastoma: Cerebrospinal fluid (CSF) interleukin-6 (IL-6) levels, one of the pleiotropic cytokines that has received attention as a critical factor implicated in the invasion and the angiogenesis of various cancers, are associated with the infiltration rate of GAMs in GBM, indicating that the concentration of CSF IL-6 may be a useful prognostic biomarker for the GBM patients [58].