A human gastric cancer cell line possesses a functional receptor for gastrin-releasing peptide

Bombesin (BBS) exhibits diverse biological functions including those of neurotransmitter, regulator of gastrointestinal hormone release, and mitogen. Gastrin-releasing peptide (GRP, the mammalian equivalent of BBS) is found in mucosal cells of the gastric fundus and antrum. We determined whether a human gastric cancer cell line (SIIA) expresses a functional GRP-receptor (GRP-R). BBS increased intracellular calcium ([Ca²⁺](i)), and a specific GRP-R antagonist, ([D-Phe⁶, Des-Mef¹⁴]-BBS (6-14)-ethylamide), blocked BBS- induced increase in [Ca²⁺](i). SIIA cells possess GRP-R mRNA by reverse transcriptase-PCR. Furthermore, these cells possess an 80-kDa cell surface protein that specifically binds BBS with two high-binding affinities (K(d1) = 0.6 nM, K(d2) = 6.7 nM). These findings indicate that SIIA cells possess a GRP-R that is capable of physiological signal transduction, though the cellular response remains unknown.