In this respect, it has been demonstrated that SP acts through the NK-1 receptor as a mitogen in several human cancer cell lines, including astrocytoma, melanoma, neuroblastoma, glioma, retinoblastoma as well as pancreatic, larynx, colon, and gastric carcinoma, leukemia, and breast cancer [17–25]. Here, TACR1 is linked to retinoblastoma.