Among the astrocyte-secreted molecules, IL6 enhances GBM cell invasion by upregulating MMP activity and favoring ECM, and glial cell-line derived neurotrophic factor (GDNF) promotes GBM cell invasion by upregulation of RET, MAPK, and PI3K/Akt signaling pathways [65,118]. This evidence concerns the gene RET and glioblastoma.