In human tumors, both NTS and NTSR1 are expressed in 40%, 60%, 65%, and 80 % of breast and lung cancers, mesotheliomas, and head and neck squamous cell carcinomas, respectively, suggesting that autocrine and/or paracrine NTS regulation occurs in tumors [32,45,46]. This evidence concerns the gene NTSR1 and head and neck squamous cell carcinoma.