BDNF and glioma: Brain-derived neurotrophic factor (BDNF), an endogenous signaling molecule, is involved in the carcinogenesis of glioma (Zheng and Chen, 2020), especially in tumor growth and metastasis in neuroblastoma (Chen et al., 2016), whereas a precursor of BDNF (proBDNF) plays a role in the modulation of cell apoptosis (Xiong et al., 2013).