GDNF and neoplasm: Increased invasion of the tumor cells into the normal tissue occurs under the action of TGF-α, sphingosine-1-phosphate, stromal cell-derived factor 1 (SDF1/CXCL12), and GDNF, which are encoded by the genes with increased expression and are in the peritumoral brain zone promoting tumor mass enlargement [7, 80–83].