NGF and neoplasm: Acidosis, which is caused mainly by tumor cells and osteoclasts, activates the above-mentioned channels (TRPV1, ASICS3) and stimulates stromal cells to produce and release not only growth factors (e.g., NGF, brain-derived neurotrophic factor (BDNF)) but also pro-inflammatory mediators (e.g., IL1β, IL6, IL15, CCL5) [12].