From a broad perspective, neuroactive molecules released by the nerves involved in tumor–nerve interaction can be divided into three main families as follows: (i) neurotropic factors, such as nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), glial cell line-derived neurotrophic factor, and others; (ii) axon guidance molecules, such as CCL2, CX3CL1, EphA2, Slit, etc.; and (iii) neurotransmitters, including Ach, glutamate, glycine, epinephrine, norepinephrine, dopamine, etc.8,59. This evidence concerns the gene BDNF and neoplasm.