They secrete factors that support tumor growth (e.g. insulin-like growth factor (IGF-1), epidermal growth factor (EGF), platelet-derived growth factor (PDG-F)), as well as anti-inflammatory cytokines (e.g. interleukin-6 (IL-6), IL-10, transforming growth factor beta (TGF-β)), promoting the malignant phenotype of glioblastoma and contributing to the permeability of the BBB (52). The gene discussed is IL6; the disease is glioblastoma.