BDNF and neoplasm: Stem cell reprogramming enhances the efficacy of stem cell transplantation by secreting beneficial cytokines, such as brain‐derived neurotrophic factor (BDNF),54 glial cell line‐derived neurotrophic factor (GDNF),55, 56 vascular endothelial growth factor (VEGF),57 hepatocyte growth factor (HGF),58 placental growth factor (PIGF),59 and angiopoietin‐1 (ANG‐1),60 or contribute to reducing the risk of tumor formation61 and regulating differentiation.62, 63, 64