Bombesin stimulation of DNA synthesis and cell division in cultures of Swiss 3T3 cells.

Abstract

Bombesin is shown to be a potent mitogen for Swiss 3T3 cells. At nanomolar concentrations the peptide markedly enhances the ability of fresh serum to stimulate DNA synthesis in confluent and quiescent cultures of these cells. In the presence of a low concentration (3.5%) of serum, bombesin stimulates 3T3 cell proliferation. In serum-free medium, bombesin induces DNA synthesis in the absence of any other added growth factor; halfmaximal effect is obtained at 1 nM. The mitogenic effect of bombesin is dependent on dose and time, is mimicked by litorin, and is markedly potentiated by insulin, colchicine, platelet-derived growth factor, and fibroblast-derived growth factor. These mitogens increase the maximal response elicited by bombesin and decrease the bombesin concentration required to produce halfmaximal effect (from 1 nM to 0.3 nM). In contrast, vasopressin, phorbol esters, or cAMP increasing agents fail to enhance the maximal level of DNA synthesis induced by bombesin. Bombesin and litorin may provide useful model peptides for studies on the mechanism(s) by which extracellular ligands control cell proliferation.In recent years, a considerable number of new regulatory peptides have been identified in the brain, gastrointestinal tract, and other tissues (1-3). Bombesin, a tetradecapeptide originally isolated from frog skin (4), and bombesin-like peptides have been detected in mammalian brain (5, 6), gut (5, 7), and lung (8,9). This peptide has potent pharmacological effects on the central nervous system (10-12) and elicits the release of other peptide hormones including insulin (13,14), glucagon (13,14), gastrin (5,7,14), cholecystokinin (14), and prolactin and growth hormone (15,16). Bombesin binds to specific surface receptors in pancreatic acinar cells (17) and stimulates ion fluxes (17,18) and enzyme secretion (17,18) Recently, several reports demonstrated the presence of high concentrations of bombesin in human pulmonary tumors (19)(20)(21). This observation and the report that repeated administration of bombesin induced pancreatic hyperplasia in the rat (22) raises the possibility that bombesin could participate in the control of cell proliferation, a proposition that hitherto remained unproven. Indeed, it is difficult to obtain unambiguous evidence for a direct growth-promoting activity of bombesin in vivo because the administration of this peptide stimulates the release of many other biologically active peptides (see above) which could act as proximal effectors of the action of bombesin.Cultured cells provide a useful experimental system for elucidating the extracellular factors that control cell proliferation without the many complexities of whole animal experimentation. Many mammalian cells in culture, and Swiss 3T3 cells in particular, cease to proliferate and become arrested in the G1/ Go phase of the cell cycle when they deplete the nutrient medium of its growth-promoting activity (23). Addition of fresh serum or defined growth-promoting factors to such quiescent cells stimulates reinitiati...

Protein kinase C-mediated negative-feedback inhibition of unstimulated and bombesin-stimulated polyphosphoinositide hydrolysis in Swiss-mouse 3T3 cells

“…Bombesin stimulates DNA synthesis in Swiss 3T3 cells with a half-maximal response at peptide concentrations of 0.1-0.3 nm and a maximal response at 1-3 nm (Rozengurt & Sinnett-Smith, 1983;Corps et al, 1985). Over a similar concentration range, bombesin and related mammalian peptides stimulated a rapid but transient increase in the release of 45Ca2+ from pre-labelled cells (Fig.…”

“…Bombesin and gastrin-releasing peptide have been shown to be potent mitogens for some cell types in culture, including Swiss-mouse 3T3 cells (Rozengurt & Sinnett-Smith, 1983), normal bronchial epithelial cells (Willey et al, 1984) and cell lines derived from small-cell cancer of the lung (SCCL) (Cuttitta et al, 1985;Weber et al, 1985). Since human SCCL and SCCL-derived cell lines are known to synthesize and secrete bombesin-like peptides (Erisman et al, 1982;Moody et al, 1983;Sorenson et al, 1982), it is possible that these peptides may function as autocrine growth factors involved in the abnormal growth of the tumours.…”

Mitogenic effects of gastrin-releasing peptide in head and neck squamous cancer cells are mediated by activation of the epidermal growth factor receptor

“…Bombesin, an analog of GRP that acts through the GRPR, was found to stimulate mitogenesis in the absence of serum or any other added growth factors (Rozengurt and Sinnett-Smith, 1998;Rozengurt, 1986). Neither agents that increase cyclic AMP nor those that activate protein kinase C (PKC) enhanced the mitogenic effects of bombesin in Swiss 3T3 cells (Rozengurt, 1986;Rozengurt and Sinnett-Smith, 1983). In contrast, EGF required the presence of bombesin, insulin, or an agent that stimulates PKC to confer a mitogenic response.…”

Unliganded thyroid hormone receptor β1 inhibits proliferation of murine fibroblasts by delaying the onset of the G1 cell-cycle signals

“…Even more, almost nothing is known with regard to the possible role of the receptors on cell proliferation in the absence of ligand. To address the question whether the major TRs affect cell growth, and to gain insight into the distinct physiological functions displayed by these two isoforms, we have expressed TRa1 and TRb1 separately in Swiss 3T3 fibroblasts, a cell system widely used for proliferation studies (Rozengurt and Sinnett-Smith, 1983). Our results indicate that TR expression attenuates the growth of serum-stimulated fibroblasts, with a striking effect of the b1 isoform.…”