Somatostatin, cortistatin and their receptors in tumours.

Somatostatin (SS) and its synthetic analogs have a role in the treatment of neuroendocrine tumours both in terms of symptoms control and antiproliferative activities. These effects are mediated by five SS receptors, widely expressed in both human neuroendocrine and non-neuroendocrine tumours, which were demonstrated to be diagnostically and therapeutically valuable targets. Cortistatin (CST), a brain cortex peptide, partially homologous to SS and having similar functions is also expressed in peripheral tissues and tumours. CST binds all SS receptors, and, differently from SS, also the ghrelin receptor GHSR1a and the CST specific receptor MrgX2. The expression profile of CST is mostly restricted to neuroendocrine tumours (gastrointestinal, pancreas, lung, parathyroid, thyroid, adrenal). In these tumours, CST probably acts via the SS or ghrelin receptor, the MrgX2 receptor being absent. Thus, in comparison to SS analogs, CST synthetic analogs may represent additional diagnostic/therapeutic tools in those tumours expressing the receptors for SS, for ghrelin or for both peptides.