ZBTB18 hinders cytokine expression to impair microglia and macrophage recruitment and the establishment of a tumor-supportive microenvironment in glioblastoma

Background. Glioma associated macrophages/microglia (GAMs) are massively recruited to the tumor site where they commit to a tumor promoting phenotype, driving glioblastoma progression. GAMs secrete several factors that facilitate tumor proliferation and invasion, and prevent an effective immune response against glioblastoma. Here, we investigate how the tumor suppressor ZBTB18 affects GAMs and ultimately shapes the tumor microenvironment. Methods. The regulation of cytokine expression and secretion was assessed by gene expression and cytokine arrays. The effect of ZBTB18 expression on microglia properties was investigated in vivo in mouse xenografts and by RNAseq of microglia cells conditioned with the medium of ZBTB18-expressing patient-derived GBM cells. The analysis was further extended to TAM scRNAseq data (GBMap). Results. Here, we demonstrate that ZBTB18, a transcriptional repressor with tumor suppressive function in glioblastoma, impairs the production of key chemokines responsible for GAM recruitment. Consistently, we observe a reduced migration of GAMs towards ZBTB18-expressing glioblastoma cells, both in cell culture and in vivo experiments. Moreover, RNA sequencing analysis shows that the presence of ZBTB18 in glioblastoma cells alters the commitment of conditioned microglia, suggesting the loss of the immunosuppressive phenotype. Conclusions. Our data indicate that, by blocking the release of key cytokines, ZBTB18 modifies microglia behavior, counteracting their tumor-promoting function. Thus, therapeutic approaches to increase ZBTB18 expression in glioblastoma cells could represent an effective adjuvant to immunotherapy in the treatment of this kind of tumor.