NTRK2 and neuroblastoma: NPY expression is increased in neuroblastoma cells treated with valproate [187]; brain-derived neurotrophic factor (BDNF) promoted NPY/Y5R expression/NPY release and, in neuroblastoma cells, the expression of both NPY/Y5R has been positively correlated with the expressions of BDNF and its tropomyosin-related kinase B (TrkB) receptor [10,185].