Purpose: The objective of this study was to evaluate clinical significance and immunosuppressive mechanisms of B7-H4 (B7x/B7S1), a B7 family member, in glioma. Experimental Design: B7-H4 levels in glioma tissue/cerebral spinal fluid (CSF) were compared between different grades of glioma patients. Survival data were analyzed with Kaplan-Meier to determine the prognostic value of B7-H4. Cytokines from CD133 cells to stimulate the expression of B7-H4 on human macrophages (Mjs) were investigated by FACS, neutralizing antibodies, and Transwell chemotaxis assay. shRNA, reporter vector, and chromatin immunoprecipitation were used to determine the binding of STAT3 to the B7-H4 promoter. The function of B7-H4 Mjs in vitro was evaluated through phagocytosis, T-cell proliferation/ apoptosis, and cytokine production as well as in the xenografted model for in vivo analysis. Results: We found that B7-H4 expression in tumors was associated with prognosis of human glioblastoma and correlated directly with malignant grades. Mechanistically, glioma initiating CD133 cells and Mjs/microglia cointeraction activated expression of B7-H4 via IL6 and IL10 in both tumor cells and microenvironment supporting cells. IL6-activated STAT3 bound to the promoter of B7-H4 gene and enhanced B7-H4 expression. Furthermore, CD133 cells mediated immunosuppression through B7-H4 expression onMjs/microglia by silencing of B7-H4 expression on these cells, which led to increased microenvironment Tcell function and tumor regression in the xenograft glioma mouse model. Conclusions: We have identified B7-H4 activation on Mjs/ microglia in the microenvironment of gliomas as an important immunosuppressive event blocking effective T-cell immune responses.
Bibliographical noteFunding Information:
This work was supported by the National Science Foundation for Distinguished Young Scholars of China (grant no. 81025013; to Y. Mao), the National Natural Science Foundation of China (grant no. 81372708 and 81272797; to Y. Yao), the Project for National 985 Engineering of China (No.985-YFX0102; to Y. Mao), the "Dawn Tracking" Program of Shanghai Education Commission, and China grant 10GG01 (to Y. Mao),the Project for Science and Technology Commission of Shanghai Municipality grant 13JC1408000 (to L. Zhou), innovation Program of Shanghai Municipal Education Commission (grant no. 13ZZ010; to Y. Yao).
© 2016 American Association for Cancer Research.