The role of osteopontin in H pylori-induced gastric carcinogenesis and chemoradiation resistance of esophageal squamous cell carcinoma

Abstract

Background: Osteopontin (OPN) is a multifunctional glycophosphoprotein which play important roles in tumor survival and progression We investigated the role of OPN in chemoradiation resistance of esophageal squamous cell carcinoma (ESCC) and H pylori-induced gastric precancer formation Methods: In ESCC cohort the consecutive ESCC patients treated by definitive chemoradiotherapy (CRT) were enrolled The patients’ baseline plasma OPN levels were determined by ELISA and compared to healthy controls In ESCC patients the correlations between OPN level and CRT response and between OPN level and prognosis were evaluated The cell culture experiments were performed to investigate the effect of OPN knockdown on enhancing chemoradiosensitivity and the downstream mechanisms In chronic gastritis cohort OPN expression levels in gastric mucosa and plasma were compared between patients with and without H pylori infection and between H pylori-infected patients with and without gastric precancerous change (intestinal metaplasia IM) The correlations between OPN expression and gastric inflammation and IM were evaluated Patients were followed after H pylori eradication to assess OPN expression change The cell culture experiments were performed to elucidate the upstream mechanisms of OPN induction by H pylori and the downstream pathways involved in IM formation Results: Patients with ESCC had significantly elevated plasma OPN levels than healthy controls (mean OPN level: 133 4 vs 84 6 ng/mL p <0 001) In ESCC patients high baseline plasma OPN level correlated with poor CRT response and prognosis The cell culture experiments confirmed that ESCC cells with high OPN expression were more resistant to irradiation-induced proliferation inhibition OPN knockdown in high-OPN expression ESCC cells enhanced chemoradiosensitivity increased G2/M phase of cell cycle and inhibited expression of DNA damage response genes In chronic gastritis cohort H pylori-infected patients had higher gastric OPN expression than the non-infected controls (p <0 001) For the H pylori-infected patients an increased gastric OPN expression correlated with more severe chronic gastric inflammation (p <0 001) and the presence of IM (OR: 2 6 95% CI: 1 15-5 94 p = 0 02) However the plasma OPN levels were similar between groups After H pylori eradication the gastric OPN expression could be decreased only in areas without IM (p <0 001) Double immunofluorescence stain showed T-cell and macrophage were the main OPN expressing immunocytes H pylori stimulate secretory OPN (sOPN) from monocytes (U937 cell) and intracellular OPN (iOPN) from gastric epithelial cells (MKN45) TLR2 antagonist abolished iOPN expression in MKN45 induced by gastritis strain but not by cancer strain of H pylori The H pylori CagA delivered via type IV secretion system is indispensable for iOPN upregulation H pylori induced beta-catenin accumulation and interleukin-8 secretion in MKN45 whereas OPN knockdown in MKN45 completely abrogated these effects Adding recombinant OPN (sOPN) to GES-1 cell also increased beta-catenin nuclear translocation via AKT-GSK-3beta signal transduction pathways Conclusion: OPN may contribute to chemoradiation resistance of ESCC and gastric IM formation Plasma OPN is a potential marker for prediction of CRT response and prognosis of ESCC Inhibition of OPN may be a promising strategy to improve CRT response of ESCC and prevent formation of gastric cancer

Date of Award	2015 Apr 27
Original language	English
Supervisor	Bor-Shyang Sheu (Supervisor)