Receptor subtype expression and responsiveness to bombesin in cultured human bronchial epithelial cells

We detected low level expression of the gastrin-releasing peptide and neuromedin-B receptor mRNAs in cultures of human bronchial epithelium from 4 of 6 individuals. Bombesin receptor subtype-3 mRNA was undetectable in these cells. An elevation of intracellular calcium concentration was observed in response to bradykinin (6 of 6) and neurotensin (1 of 5) but not to bombesin (0 of 6), vasopressin (0 of 6), or cholecystokinin (0 of 3). In contrast, such responses are frequently noted in lung cancer cell lines. Bombesin did not stimulate the in vitro growth of an immortalized human bronchial epithelium cell line expressing low levels of bombesin receptor mRNAs. We conclude that bombesin receptors are expressed at low levels in human bronchial epithelium cells which may acquire greater responsiveness to multiple neuropeptides in the course of multistep carcinogenesis.