LGR5, a novel functional glioma stem cell marker, promotes EMT by activating the Wnt/β-catenin pathway and predicts poor survival of glioma patients

Background: Tumor recurrence, the chief reason for poor prognosis of glioma, is largely attributed to gliorna stem cells (GSCs) and epithelial-mesenchymal transition (EMT). However, the mechanisms among them remain unknown. Here, we determined whether leucine-rich repeat-containing G protein-coupled receptor 5 (LGR5), known as a stem cell marker for colon cancer and gastric cancer, can serve as a novel GSC marker involved in EMT and a therapeutic target in glioma. Methods: Stemness properties were examined in FACS-isolated LGR5(+)/LGR5(-) cells. Reported stem cell markers, EMT and the Wnt/beta-catenin pathway were examined in stable LGR5 knockdown or overexpressed GSCs by Western Blot. The treatment experiment was performed in an intracranial orthotopic xenograft model by knockdown of LGR5 or by using the Wnt/beta-catenin pathway inhibitor Wnt-059. LGR5 expression was determined in 268 glioma specimens by immunohistochemistry. Results: LGR5(+) cells possessed stronger stemness properties compared to LGR5(+) cells. The expression of SOX2, Nanog, CD133, CD44, CD24 and EpCAM was modulated by LGR5. Both LGR5 knockdown and Wnt-059 reduced tumor invasion and migration and blocked EMT by inhibiting the Wnt/beta-catenin pathway in vitro and suppressed the intracranial orthotopic xenograft growth and prolonged the survival of xenograft mice in vivo. Moreover, LGR5 was positively correlated with Ki67, N-cadherin and WHO grade and negatively correlated with IDH1. Glioma patients with high expression of LGR5 showed significantly poorer prognosis. Conclusions: LGR5 is a new functional GSC marker and prognostic indicator that can promote EMT by activating the Wnt/beta-catenin pathway and would thus be a novel therapeutic target for glioma.