Stimulation of the gastrin-cholecystokinin(B) receptor promotes branching morphogenesis in gastric AGS cells.

Epithelial organization is maintained by cell proliferation, migration, and differentiation. In the case of the gastric epithelium, at least some of these events are regulated by the hormone gastrin. In addition, gastric epithelial cells are organized into characteristic tubular structures (the gastric glands), but the cellular mechanisms regulating the organization of tubular structures (sometimes called branching morphogenesis) are uncertain. In the present study, we examined the role of the gastrin-cholecystokinin(B) receptor in promoting branching morphogenesis of gastric epithelial cells. When gastric cancer AGS-G(R) cells were cultured on plastic, gastrin and PMA stimulated cell adhesion, formation of lamellipodia, and extension of long processes in part by activation of protein kinase C (PKC) and phosphatidylinositol (PI)-3 kinase. Branching morphogenesis was not observed in these circumstances. However, when cells were cultured on artificial basement membrane, the same stimuli increased the formation of organized multicellular arrays, exhibiting branching morphogenesis. These effects were reversed by inhibitors of PKC but not of PI-3 kinase. We conclude that, in the presence of basement membrane, activation of PKC by gastrin stimulates branching morphogenesis.

Gastrin-cholecystokinin(B) receptor expression in AGS cells is associated with direct inhibition and indirect stimulation of cell proliferation via paracrine activation of the epidermal growth factor receptor.

BACKGROUND: Activation of the gastrin-cholecystokinin(B) (CCK(B)) receptor stimulates cell proliferation and increases production of ligands for the epidermal growth factor receptor (EGF-R). AIMS: To determine the role of gastrin-CCK(B) activation in stimulation of cell proliferation via paracrine activation of EGF-R. METHODS: AGS cells were transfected with the gastrin-CCK(B) receptor (AGS-G(R) cells) or with green fluorescent protein (AGS-GFP cells). Proliferation was determined by [(3)H] thymidine incorporation, flow cytometry, and cell counting. RESULTS: Gastrin inhibited proliferation of AGS-G(R) cells by delaying entry into S phase. However, when AGS-G(R) cells were cocultured with AGS-GFP cells, gastrin stimulated proliferation of the latter. Immunoneutralisation and pharmacological studies using metalloproteinase and kinase inhibitors indicated that the proliferative response was mediated by paracrine stimulation of EGF-R and activation of the mitogen activated protein kinase pathway through release of heparin binding EGF. CONCLUSIONS: Gastrin can directly inhibit, and indirectly stimulate, proliferation of gastric AGS cells.