BDNF and small cell lung carcinoma: Odate et al. [92] also found that the expression of the tropomyosin-related kinase (Trk) and brain-derived neurotrophic factor (BDNF) in LCNEC patients were higher than that in the control SCLC group, suggesting that BDNF/TrkB pathway may be a potential therapeutic target for LCNEC.