It is important to consider not only the qualitative but also the quantitative expression of NK-1 receptors by tumor cells, since it has been demonstrated that NK-1 receptor expression is increased 25–36-fold in human pancreatic cancer cell lines in comparison with normal controls, and that tumor samples from patients with advanced tumor stages exhibit significantly higher NK-1 receptor levels [55]. This evidence concerns the gene TACR1 and familial pancreatic carcinoma.