Bombesin

Bombesin is a peptide originally isolated from the skin of the European fire-bellied toad Bombina bombina. It is the prototypical member of the bombesin/GRP family, which also includes gastrin-releasing peptide (GRP) and neuromedin B (NMB). Bombesin is a 14‑amino-acid peptide in which the C-terminal region is essential for its biological activity.

In mammals, bombesin acts through a family of G protein–coupled receptors known as bombesin receptors, currently categorized into three subtypes: GRPR (BB1), NMBR (BB2), and BRS-3 (BB3). These receptors are expressed in various brain regions and peripheral tissues, and their activation influences neural and endocrine signaling. Bombesin stimulates gastrin release from the stomach, promotes pancreatic and biliary secretions, can induce smooth muscle contraction, and is involved in feeding regulation and energy balance. It also modulates the release of other neuroendocrine mediators.

Clinical and research significance: Bombesin-like peptides and their receptors are overexpressed in several cancers, notably some neuroendocrine tumors and small cell lung carcinoma, making GRPR-targeted imaging and therapy an area of active investigation. Radiolabeled bombesin analogs are used for tumor visualization in research contexts, and receptor antagonists are explored for potential anti-titumor effects. Beyond oncology, bombesin signaling has been studied in appetite control and neuroendocrine regulation, reflecting its broader role in mammalian physiology.