Abstract 5195: Shh/Gli signaling pathway promotes tumor metastasis and lymphangiogenesis via activation of PI3K/Akt and Erk pathway in gastric cancer

Abstract

Abstract The activation of Sonic hedgehog (Shh)/Gli signaling is involved in the progression and invasion of various tumors types, including gastric carcinoma. Epithelial-mesenchymal transition (EMT) and matrix metalloproteinases (MMPs) have been implicated in facilitating the invasion and metastatsis. Herein, we investigated the impact of phosphoinositide 3-kinase (PI3K)/Akt and Erk pathway and MMPs activity on the Shh/Gli-mediated EMT and invasion of gastric cancer cells. We found that overexpression of Shh significantly enhanced cellular motility/invasiveness, lymphangiogenesis, and metastatic ability of tumor cells in gastric cancer cell lines and mice. Stimulation of Shh in gastric cancer cells also induced a full EMT process (characterized by Snail induction and E-cadherin down-regulation) and expression and activity of MMP-9. Meanwhile, blockade of Shh/Gli signaling by Cyclopamine (a Shh signaling inhibitor), anti-Shh neutralizing antibodies, or Gli siRNA inhibited Shh-induced motility/invasiveness and lymphangiogenesis in gastric cancer by subsequently restoring these changes of EMT markers and activity of MMP-9. The phosphorylation of Akt and Erk was also enhanced by treatment with Shh, but not cyclopamine, anti-Shh neutralizing antibodies, or Gli siRNA. Blockade of the Akt and MEK kinase using kinase-dead Akt, LY294002, or PD98059 significantly inhibited the Shh-induced EMT, activity of MMP-9, lymphangiogenesis, and metastasis in tumor cell lines and mice over-expressing Shh. Furthermore, knock-down of MMP-9 by its siRNA results in an decrease in invasiveness of gastric cancer cells treatment with Shh. Immunohistochemistry on gastric tumor biopsies showed that the levels of Gli, E-cadherin, MMP-9, D2-40 (lymphangiogenic factor), and phospho-Akt expression were enhanced in cases of metastatic gastric cancer than in cases of primary gastric cancer. Moreover, the strong correlation between Gli and E-cadherin, MMP-9, D2-40, phospho-Akt, or phospho-Erk expression was also observed in lymph node metastasis specimens. These data indicate that Shh/Gli signaling pathway promotes tumor metastasis in gastric cancer through activation of PI3K/Akt and Erk pathway followed by up-regulation of EMT, MMP-9, and lymphangiogenesis, which results in the stimulation of invasiveness of tumor cells. 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 5195.