Butadiene and Styrene Risks

The control of cell proliferation by gastrin has been investigated in a rat pancreatic tumour cell line, AR4-2J. Exogenous gastrin, 10-12 to 10-8 M, stimulated cell growth of thymidine-synchronised AR4-2J cells cultured over 48 h in serum-free medium. Cell lysates of AR4-2J cells contained an average of 4.5 and 3.5 pg gastrin per 106 cells, when grown in serum-supplemented or serum-free media, respectively, as revealed by radioimmunoassay. In serum-free medium, AR4-2J secrete 34ngl 10-6 cells of gastrin over 48h. Addition of an anti-gastrin immunoglobulin preparation, but not control immunoglobulins, caused a maximum 52% reduction in cell growth. These data are consistent with an autocrine role for gastrin in the control of AR4-2J cell growth. These results were supported by studies with gastrin/CCK receptor antagonists. Six non-peptide gastrin/CCK receptor antagonists inhibited AR4-2J cell growth in a concentration-related manner. The concentration required for 50% inhibition (IC50) of cell growth by the amino acid-derived antagonists proglumide (3.5 x 10M), benzotript (1.8 x 10-3 M), loxiglumide (1.1 x 10-4 M) and lorglumide (6.7 x 10-5 M) were of the same order and significantly correlated with their IC50 for inhibition of 1251-gastrin binding to AR4-2J cells. Inhibition of cell growth by these antagonists was partially reversed by the addition of exogenous gastrin. In contrast, the ICm for inhibition of cell growth with two benzodiazepine-derived antagonists, the CCK-B receptor antagonist L-365,260 (4.6 x 10-5 M) and the CCK-A receptor antagonist devazepide (1.7 x 10-' M) were two-three orders of magnitude greater than those required to inhibit gastrin binding (10-8-10-7 M). The growth inhibitory effects of L-365,260 and devazepide were not reversed by exogenous gastrin suggesting these benzodiazepine-derived antagonists do not inhibit cell growth by interaction with gastrin receptors. The results are consistent with gastrin being an autocrine growth factor in AR4-2J cells, and that stimulation of cell growth is due to stimulation of the gastrin, rather than CCK-B, receptor sub-type. This study highlights that gastrin receptor antagonists warrant further investigation as agents to control growth of tumours, such as those from the gastrointestinal tract, which express gastrin receptors.