NPY and central nervous system neoplasm: Moreover, numerous researchers have investigated the plasma concentrations of various biomarkers in plasma, e.g. glial cell line-derived neurotrophic factor (GDNF), brain-derived neurotrophic factor (BDNF), glial fibrillary acidic protein (GFAP), neuropeptide Y (NPY, placental growth factor (PlGF), S100B, and interleukin 8 (IL-8) in patients diagnosed with diverse forms of CNS tumors (22).