4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone or nicotine-derived nitrosamine ketone (NNK) is a tobacco-specific nitrosamine. NNK is considered to be a carcinogen. NNK induces deleterious mutations in oncogenes and tumor suppression genes by forming DNA adducts, which could be considered as tumor initiation. Meanwhile, the binding of NNK to the nicotinic acetylcholine receptor promotes tumor growth by enhancing and deregulating cell proliferation, survival, migration, and invasion, thereby creating a microenvironment for tumor growth.