B7-H4(B7x)–Mediated Cross-talk between Glioma-Initiating Cells and Macrophages via the IL6/JAK/STAT3 Pathway Lead to Poor Prognosis in Glioma Patients

Abstract

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 prognostic value of B7-H4. Cytokines from CD133+ cells to stimulate the expression of B7-H4 on human Mφs were investigated by FACS, neutralizing antibodies and transwell chemotaxis assay. shRNA, reporter vector and ChIP were used to determine the binding of STAT3 to the B7-H4 promoter. The function of B7-H4+ Mφs in vitro was evaluated through phagocytosis, T cell proliferation/apoptosis and cytokine production as well as in 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 macrophages/microglia co-interaction activated expression of B7-H4 via IL-6 and IL-10 in both tumor cells and microenvironment supporting cells. IL-6-activated STAT3 bound to the promoter of B7-H4 gene and enhanced B7-H4 expression. Furthermore, CD133+ cells mediated immunosuppression through B7-H4 expression on macrophages/microglia by silencing of B7-H4 expression on these cells which led to increased microenvironment T cell function and tumor regression in the xenograft glioma mouse model. Conclusion We have identified B7-H4 activation on macrophages/microglia in the microenvironment of gliomas as an important immunosuppressive event blocking effective T-cell immune responses.

The third group of the B7‐CD28 immune checkpoint family: HHLA2, TMIGD2, B7x, and B7‐H3

“…Stimulation of IL‐6‐mediated phosphorylation of STAT3 upregulated B7‐H4 promoter activity, which was abrogated by knockdown of STAT3 with shRNA. This shows that STAT3 upregulates B7x transcription via its promoter and represents one mechanism of B7x regulation …”

“…The functional mechanisms of upregulation of B7x in glioma cells were explored . IL‐6 potently upregulated B7x expression in glioma cell lines.…”

New B7 Family Checkpoints in Human Cancers

“…B7-H4 expression is significantly associated with poor outcome in patients with RCC (65), lung cancer (66), CRC (67), cholangiocarcinoma (68), glioma (69), pancreatic cancer (70), oral squamous cell carcinoma (71), esophageal squamous cell carcinoma (72), gallbladder cancer (35), ovarian serous carcinoma (73) and gastric cancer (74). B7-H4 expression in RCC is associated with adverse clinical and pathologic features, including constitutional symptoms, tumor necrosis, and advanced tumor size, stage, and grade.…”

Oxaliplatin disrupts pathological features of glioma cells and associated macrophages independent of apoptosis induction

“…Infiltrating monocytes from the circulation and the brain resident macrophage–microglia—are the primary non-neoplastic cells in gliomas and these two immune cell populations compose as much as 30% of the tumor mass [16–18]. Factors released within the tumor microenvironment recruit and alter the phenotype and function of these myeloid cells, resulting in their polarization to a tumor supporting, pro-tumorigenic state [16–18, 31–33]. A major transcription factor controlling the co-option of tumor infiltrating myeloid cells is STAT3 [31–33].…”

“…Factors released within the tumor microenvironment recruit and alter the phenotype and function of these myeloid cells, resulting in their polarization to a tumor supporting, pro-tumorigenic state [16–18, 31–33]. A major transcription factor controlling the co-option of tumor infiltrating myeloid cells is STAT3 [31–33]. We therefore sought to determine the impact of OXA on BMDM STAT3 phosphorylation and polarization after exposure to glioma conditioned media (GCM).…”