SSTR
Somatostatin receptor (SSTR) refers to a family of five G protein-coupled receptors (SSTR1–SSTR5) that bind the neuropeptide somatostatin and, to a lesser extent, cortistatin. They couple to Gi/o proteins, inhibiting adenylyl cyclase, reducing cyclic AMP, modulating calcium channels, and suppressing secretion in target cells. SSTRs are expressed in a wide range of tissues, including the pituitary, brain, gastrointestinal tract, and pancreas. Among the subtypes, SSTR2 is commonly the most abundant in neuroendocrine tumors and is a primary target for imaging and therapy, while SSTR1, SSTR3, SSTR4, and SSTR5 have more variable tissue distributions.
In clinical practice, SSTR expression is used for diagnostic and therapeutic purposes. Diagnostic imaging employs radiolabeled
Limitations include variability in receptor expression and tumor biology; not all tumors express SSTRs, and responses