GDNF and central nervous system cancer: In our group of glioma patients, seven markers showed an interesting positive correlation with the serum level of sαKL, namely, angiogenic VEGF (p = 0.0008), CX3CL1 chemokine fractalkine (p = 0.0009), IFNγ (p = 0.003; main sustaining Th1 cytokine; role in anti-tumor immunity), GDNF (p = 0.0268), IL-6 (p = 0.0347), IL-4 (p = 0.0037) and IL-13 (p = 0.0004).