Gastrin-releasing peptide, a mammalian analog of bombesin, is present in human neuroendocrine lung tumors.

Several reports have indicated that the amphibian peptide bombesin is present in oat-cell carcinoma of the human lung. The recent observation that gastrin-releasing peptide (GRP), a 27-amino acid peptide isolated from porcine intestine, may be the mammalian analog of bombesin led the authors to look for this peptide in human pulmonary tumors. Examination of 36 human lung tumors (8 carcinoids, 8 oat-cell carcinomas, and 20 non-oat-cell carcinomas) by immunohistochemistry and radioimmunoassay demonstrated the presence of high, although variable, levels of GRP in neuroendocrine tumors, and not in other histologic types. These findings indicate that bombesin immunoreactivity in human lung tumors should be attributed to GRP or GRP-like molecules and that GRP may be a useful marker of neuroendocrine differentiation.