Moreover, the literature shows that several neurotransmitters (epinephrine, norepinephrine, dopamine, serotonine, acetylcholine, glutamate, gamma-aminobutyric acid) and neuropeptides (neuropeptide Y, neurohypophyseal, corticotropin-releasing factor, opioid, secretin, somatostatin, tachykinin) are similarly involved in tumor progression, mainly by stimulating the proliferation or migration ability of cancer cells, a key event in metastasis (131). Here, NPY is linked to cancer.