Orexins, by binding OX1R or OX2R, can cause massive apoptosis and a reduction in cell growth in several cancer cell lines, such as human colon cancer cells (40, 41), human neuroblastoma cells (40), rat pancreatic tumor cells (42), rat C6 glioma cells (43), and Chinese hamster ovary (CHO) cells transfected with OX1R cDNA. This evidence concerns the gene HCRTR2 and central nervous system cancer.