Fig. 5

Targeting IGFBP3 therapy efficiently suppresses glioblastoma invasion in vitro and tumor growth in vivo via reducing PD-L1 expression. A Immunoblotting analysis of IGFBP3 expression in GL261 cell infected with sh-IGFBP3 and sh-con. B Immunofluorescence was used to examine IGFBP3 expression in GL261 cell infected with sh-IGFBP3 and sh-con. C Left: Representative image of brain orthotopic tumor. Right: HE stained representative image of brain tumor section. D Kaplan–Meier plots for GL261-shcon and GL261-shIGFBP3 groups, and statistical significance was assessed using the log-rank test. E Immunohistochemical representative images of IGFBP3, PD-L1 and CD31 in the GL261-shcon and GL261-shIGFBP3 groups. F IGFBP3 up-regulates the expression of PD-L1 by activating JAK2/STAT3 signaling pathway. PD-L1 binds to T cell–derived PD-1 to promote T cell apoptosis and immunosuppression. Data are expressed as mean ± SD. **P < 0.01; ***P < 0.001, Student t test