Purpose: Upregulation of programmed death-ligand 1 (PD-L1) on circulating and tumor-infiltrating myeloid cells is a critical component of GBM-mediated immunosuppression that has been associated with diminished response to vaccine immunotherapy and poor survival. Although GBM-derived soluble factors have been implicated in myeloid PD-L1 expression, the identity of such factors has remained unknown. This study aimed to identify factors responsible for myeloid PD-L1 upregulation as potential targets for immune modulation.Experimental Design: Conditioned media from patientderived GBM explant cell cultures was assessed for cytokine expression and utilized to stimulate na€ ve myeloid cells. Myeloid PD-L1 induction was quantified by flow cytometry. Candidate cytokines correlated with PD-L1 induction were evaluated in tumor sections and plasma for relationships with survival and myeloid PD-L1 expression. The role of identified cytokines on immunosuppression and survival was investigated in vivo utilizing immunocompetent C57BL/6 mice bearing syngeneic GL261 and CT-2A tumors.Results: GBM-derived IL6 was identified as a cytokine that is necessary and sufficient for myeloid PD-L1 induction in GBM through a STAT3-dependent mechanism. Inhibition of IL6 signaling in orthotopic murine glioma models was associated with reduced myeloid PD-L1 expression, diminished tumor growth, and increased survival. The therapeutic benefit of anti-IL6 therapy proved to be CD8 þ T-cell dependent, and the antitumor activity was additive with that provided by programmed death-1 (PD-1)-targeted immunotherapy.Conclusions: Our findings suggest that disruption of IL6 signaling in GBM reduces local and systemic myeloid-driven immunosuppression and enhances immune-mediated antitumor responses against GBM. Ã , P < 0.05; ÃÃ , P < 0.01; ÃÃÃ , P < 0.001; ÃÃÃÃ , P < 0.0001.Lamano et al. Analysis and interpretation of data (e.g., statistical analysis, biostatistics, computational analysis):

Purpose: Gliomas with isocitrate dehydrogenase 1 mutations (IDH1 mut) are less aggressive than IDH1 wild-type (IDH1 wt) gliomas and have global genomic hypermethylation. Yet it is unclear how specific hypermethylation events contribute to the IDH1 mut phenotype. Previously, we showed that the gene encoding the procoagulant tissue factor (TF), F3, is among the most hypermethylated and downregulated genes in IDH1 mut gliomas, correlating with greatly reduced thrombosis in patients with IDH1 mut glioma. Because TF also increases the aggressiveness of many cancers, the current study explored the contribution of TF suppression to the reduced malignancy of IDH1 mut gliomas. Experimental Design: TF expression was manipulated in patient-derived IDH1 mut and IDH1 wt glioma cells, followed by evaluation of in vitro and in vivo behavior and analyses of cell signaling pathways. Results: A demethylating agent, decitabine, increased F3 transcription and TF-dependent coagulative activity in IDH1 mut cells, but not in IDH1 wt cells. TF induction enhanced the proliferation, invasion, and colony formation of IDH1 mut cells, and increased the intracranial engraftment of IDH1 mut GBM164 from 0% to 100% (P ¼ 0.0001). Conversely, TF knockdown doubled the median survival of mice engrafted with IDH1 wt /EGFRvIII amp GBM6, and caused complete regression of IDH1 wt /EGFR amp GBM12 (P ¼ 0.001). In vitro and in vivo effects were linked to activation of receptor tyrosine kinases (RTK) by TF through a Src-dependent intracellular pathway, even when extracellular RTK stimulation was blocked. TF stimulated invasion predominately through upregulation of b-catenin. Conclusions: These data show that TF suppression is a component of IDH1 mut glioma behavior, and that it may therefore be an attractive target against IDH1 wt gliomas.

BackgroundPilocytic astrocytomas (PAs) are the most common pediatric central nervous system neoplasms. In the majority of cases these tumors are benign and receive favorable prognosis following gross total surgical resection. In patients with progressive or symptomatic tumors, aggressive surgical resection is generally not feasible, thus radiation or chemotherapy are accepted initial or adjuvant interventions. Due to serious long-lasting side-effects, radiation is limited in young children; therefore, chemotherapy is widely practiced as an adjuvant treatment for these patients. However, chemotherapy can promote the emergence of multidrug resistant tumor cells that are more malignant than those of the original tumor. CD133, a putative stem cell marker in normal tissue and malignant brain tumors, enhances multidrug resistant gene 1 (MDR1) expression following chemotherapy in adult malignant glioblastomas. This study examines the relationship between CD133 and MDR1 in pediatric PAs exposed to chemotherapy, with the goal of identifying therapeutic targets that manifest as a result of chemotherapy.MethodsSlides were obtained for 15 recurrent PAs, seven of which had received chemotherapy prior to surgical treatment for the recurrent tumor. These samples, as well as primary tumor tissue slides from the same patients were used to investigate CD133 and MDR1 expression via immunofluorescence. Archived frozen tissue samples from the same patients were used to examine CD133, MDR1 and PI3K-Akt-NF-κB signaling mediators, via western blot. Two drug resistant pediatric PA cell lines Res186 and Res199 were also used to evaluate the role of CD133 on cell response to cytotoxic therapy.ResultsCD133 and MDR1 were co-expressed and their expression was elevated in recurrent PAs from patients that had received chemotherapy, compared to patients that had not received chemotherapy. PI3K-Akt-NF-κB signaling mediator expression was also elevated in recurrent, chemotherapy-treated PA. Suppressing CD133 expression with siCD133 decreased levels of PI3K-Akt-NF-κB signaling mediators and MDR1, while increasing cell chemosensitivity, as indicated by quantification of apoptotic cells following chemotherapy.ConclusionsCD133 contributes to multidrug resistance by regulating MDR1 levels via the PI3K-Akt-NF-κB signal pathway not only in adult glioblastomas, but also in pediatric PAs. Targeting CD133, adjuvant to conventional chemotherapy may improve outcomes for children with recurrent PA.Electronic supplementary materialThe online version of this article (doi:10.1186/s12943-017-0593-z) contains supplementary material, which is available to authorized users.