| The growth factor-like or growth-inhibitory effects of some gastro-intestinal(GI) hormones have been recently noticed. Bombesin is a 14 amino acid Gl peptide which was reported as growth factor-like peptide and plays an autocrine regultory role in the growth of human small cell lung cancer cell. The aim of this study was to investigate the growth regulatory effect of bombesin on gastric cancer cell line SGC7901 and and immortalized and phenotypically normal human gastric epithelial cell line GES-1. Experimental design and methods: (1) The effects of bombesin (BOM), BOM-antagonist (BOM-A) and PKC antagonist (staurosporine) on the growth of human gastric cancer cell line SGC7901 and immortalized human gastric epithelial cell GES-1 were studied, using ~3H-thymidine(~3H-TdR) uptake and thiazolyl blue (MTT) assay as parametesr of cell growth. (2) RT- PCR and Southern blot hybridization were performed for detection of GRP-R mRNA, covalent cross- linking study with biotinyl- BOM and Enhanced Chemoluminescence (ECL) and cytochemistry were performed to identify GRP-R at protein levels in SGC7901 and GES-1. (3) The effects of BOM on intracellular IP3 in SGC7901 and GES-1 cells and on the activation of protein kinase C in GES-1 were investigated in order to clarify, at lease in part.the cellular mechanisms of BOM. (4)To identify if there is an autocrine regulation loop in SGC7901 cells, the effect of BOM-A on the growth of this cell was observed. The expression of GRP-R mRNA in GES-1 cells was illustrated by RT-PCR and Southern blot hybridation.
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