Abstract 1724: Role of GSK-3beta in gastrin-induced migration of gastric cancer cells

Abstract Background: Gastric cancers are a leading cause of death worldwide, mainly due to late detection and lack of effective therapeutic strategies. An immediate first step towards designing a safe and targeted therapeutic strategy would be to gain a better understanding of the pathobiology of these cancers. Of the different etiologic risk factors contributing to gastric cancer, Helicobacter pylori infection is the most recognized. The gastrointestinal peptide hormone gastrin also plays a significant role in mediating gastric cancer pathogenesis. Our earlier studies showed that amidated gastrin (G17) can induce proliferation in gastric cancer cells, via involvement of β-catenin and CREB. Our more recent work has been focused on elucidating the signaling mechanism by which G17 induces migratory responses in gastric cancer cells. These studies revealed that G17-induced migration is mediated via activation of JNK/MAPKinase pathway. To understand the role of other signaling molecules in mediating these responses, studies were designed here with the serine/threonine kinase Glycogen Synthase Kinase-3beta (GSK3β), which is known to regulate migratory pathways, via regulating expression of snail. Aim: These studies were undertaken to (i) determine any effect of G17 on GSK3β pathway, (ii) identify the downstream target of GSK3β and (iii) understand whether GSK3β plays any role in G17-induced migration. Methods: To address these, studies were designed with human gastric cancer cells (AGSE), overexpressing the gastrin CCKB receptor following incubation with G17. Wherever necessary, cells were pretreated with GSK3β specific inhibitor (AR-A014418) or transiently transfected with different GSK3β expression vectors or luciferase vectors. Changes in protein expression were estimated by Western Blot analysis utilizing appropriate antibodies, and the degree of changes in luciferase activity was estimated by luciferase assays. Results: Stimulation of AGSE cells with G17 resulted in a transient increase in GSK3βser9 phosphorylation (inactivation) associated with a parallel increase in AKTSer473 phosphorylation. G17 treatment also resulted in an increase in snail protein expression (GSK3β downstream) and promoter activation. Pharmacological inhibition of GSK3β with AR-A014418 increased snail expression in the absence of G17 and overexpression of phosphorylation deficient mutant of GSK3β (S9A) antagonized G17-induced snail promoter induction. In addition, ectopic overexpression of GSK3β-S9A antagonized G17-induced cell migration and MMP-7 promoter activation, with synergistic effects when overexpressed with a kinase deficient mutant of GSK3β (K/A). Conclusion: These studies indicate that GSK3β might be playing an important role in G17-induced migratory events via regulating snail and MMP7 expression. This pathway can be exploited further for developing anticancer therapies to target gastrin-related cancer pathways. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1724.