Moreover, bidirectional communication between neurons and cancer cells accelerates tumor development and progression.295–297 Specifically, cancer cells induce the outgrowth of nerves in the tumor microenvironment through paracrine-acting neurotrophic factors (e.g., NGF, BDNF) and axon guidance molecules, and in turn, nerves release neurotransmitters in the tumor microenvironment that stimulate cancer cell proliferation, invasion, and metastasis. This evidence concerns the gene BDNF and neoplasm.