BDNF and non-small cell lung carcinoma: We selected a range of neurotrophic factors known to enhance the survival, differentiation, and functional maintenance of neural cells, including NGF, brain-derived neurotrophic factor (BDNF), glial cell line-derived neurotrophic factor (GDNF), neurotrophin-3 (NT-3), and neurotrophin-4 (NT-4) [22], and evaluated their expression levels in NSCLC cells.