NTSR1 and cancer: Two of these proteins, NTSR1 and NTSR2, are GPCRs, whereas NTSR3/sortilin, which has a single transmembrane domain, plays a major role as a sorting receptor.10 NTSR1 drives homeostatic processes in the nervous and gastrointestinal systems, but is also actively involved in overexpression of anti-apoptotic proteins and chemotherapy resistance in cancer.11, 12