Leucine-rich repeats and immunoglobulin-like domains 2 promoted the cell cycle progression of glioblastoma cells through modulating the platelet-derived growth factor receptor β signaling pathways

Abstract

Objective To investigate the effects of leucine-rich repeats and immunoglobulin-like domains 2 (LRIG2) protein on the cell cycle progression of glioblastoma cells and the underlying mechanisms. Methods Tumors tissues were subjected to immunohistochemical staining to detect the protein expression levels.Flow cytometric analysis was used to detect the in vitro cell cycle progression, respectively. Subcutaneous tumor formation in nude mice was performed to investigate the tumor growth in vivo. Immunofluorescence and co-immunoprecipitation (Co-IP) were used to detect the protein interaction, and western blotting was used to examine the signaling pathway proteins. Results Protein expression level of LRIG2 positively correlated with the level of platelet-derived growth factor receptor β (PDGFRβ) in human glioblastoma (χ2=6.411, P<0.05). The percentage of cells in S or G2/M phase dramatically increased in the platelet derived growth factor-BB (PDGF-BB)-induced LRIG2-overexpressing U87 cells, compared with the control cells [(22.74±1.23)% vs. (11.60±0.82)%, t=13.052, P<0.05; (19.06±1.04)% vs. (9.36±0.65)%, t=13.699, P<0.05]. The volume of tumor xenografts at the terminal experiments were significantly increased in the mice injected with LRIG2-overexpressing U87 cells [(1 372.56±167.88) mm3 vs. (413.34±76.79) mm3,t=11.619, P<0.05]. LRIG2 and PDGFRβ were co-expressed and physically interacted in glioblastoma cells. The levels of PDGF-BB-induced phosphorylated PDGFRβ (p-PDGFRβ), phosphorylated protein kinase B (p-Akt), phosphorylated signal transducer and activators of transcription 3 (p-STAT3), Cyclin B1 and Cyclin D1 were markedly increased in LRIG2-overexpressing cells. Conclusion LRIG2 promoted the cell cycle progression of glioblastoma cells, which validated LRIG2 as a promising potential therapeutic target for treatment of glioblastoma. Key words: Leucine-rich repeats and immunoglobulin-like domains 2; Glioblastoma multiforme; Platelet-derived growth factor receptor β; Cell cycle