GDNF and cancer: Activated SCs modify their secretome, e.g., chemokine ligand-2 (CCL2), matrix metalloproteinase-2 (MMP-2), interleukin (IL-)8, IL-6, IL-1β, and glial-derived neurotrophic factor (GDNF), to propagate repair; however, cancer cells may exploit these signals to enhance PNI [4, 5].