NGF and neoplasm: In particular, it has been demonstrated that the p75 neurotrophin receptor, the low-affinity receptor of nerve growth factor (NGF), is abnormally expressed in HNC patients and is related to NGF-independent therapy resistance, while high-affinity NGF receptor (tropomyosin receptor kinase A, TrkA) might transduce a survival signal of NGF, stimulating tumor cell survival after cell cycle arrest [161,162,163,164].