The Prognostic Significance And Mechanism Between LGR5and Regulatory T Cells In Gastric Cancer

[Purpose]The concept that cancer stem cells (CSCs) are one of the key centers to cure neoplastic disease has drawn an increasing attention recent years. Leucine rich repeat containing G protein coupled receptor5(LGR5) is a well-established target gene of the Wnt pathway and is known as a potential marker of CSCs. Regulatory T cells (Tregs), a group of immune cells with tumor-promoting effect, exert their function through inhibition of effector T cells and regulation of the tumor microenvironment by producing a series of soluble factors. The present study investigated whether LGR5expression and Tregs number correlated with clinical outcome in patients with gastric cancer and researched the inductive mechanism of LGR5expression in cultured gastric cancer cells under the effect of Tregs.[Methods]In total,100patients who underwent curative resection between February2009and March2010in our hospital were enrolled. Immunohistochemistry was used to evaluate the expression of LGR5and the distribution of FoxP3+Tregs in different microanatomical areas. T tests were used to compare the distribution of FoxP3+Tregs in tumor tissues. Survival function was determined by Kaplan-Meier analysis and log-rank test. Multivariate analysis was performed by Cox proportional hazards models with the backward likelihood stepwise procedures. Cytometric Bead Array was used to detect cytokines of Thl/Th2in tumor tissues, including IL-2, IL-4, IL-6, IL-10, TNF, IFN-γ. ELISA was used to analyze the expression of TGF-β in tumor tissues. LGR5and β-catenin in cultured gastric cancer cells were detected by Q-PCR and Western Blot.[Results]The results showed that increasing intratumor FoxP3+Tregs and high level of LGR5in tumor tissues were significantly associated with worse overall survival (P=0.039,0.004; respectively). Multivariate analysis revealed that expression of LGR5in tumor tissue was independent prognostic factors (P=0.0045), similar to conventional clinicopathological features, such as degree TNM stage (P=0.0003). Significant positive correlations were detected between Tregs number and LGR5expression (P<0.0001). There is no obvious correlations between LGR5expression and cytokines of Thl/Th2in tumor tissues. However, LGR5expression was positively correlated with TGF-β. Meanwhile, the expression of LGR5was up-regulated in gastric cancer cells when co-cultured with exogenous TGF-β1. The LGR5induced by TGF-β1could be partially inhibited by the TGF-β/ALK5/Smad2signaling antagonist SB431542.[Conclusions]In conclusion, LGR5may serve as a potential biomarker for survival prognosis in gastric cancer patients and Tregs may promote the high expression of LGR5in gastric cancer cells, most likely through the co-regulation of TGF-β1and Wnt signaling pathway.