Cancer immunoresistance and immune escape may play important roles in tumor progression and pose obstacles for immunotherapy. Expression of the immunosuppressive protein B7 homolog 1 (B7-H1), also known as programmed death ligand-1 (PD-L1), is increased in many pathological conditions, including cancer. Here we show that expression of the gene encoding B7-H1 increases post transcriptionally in human glioma after loss of phosphatase and tensin homolog (PTEN) and activation of the phosphatidylinositol-3-OH kinase (PI(3)K) pathway. Tumor specimens from individuals with glioblastoma multiforme (GBM) had levels of B7-H1 protein that correlated with PTEN loss, and tumor-specific T cells lysed human glioma targets expressing wild-type PTEN more effectively than those expressing mutant PTEN. These data identify a previously unrecognized mechanism linking loss of the tumor suppressor PTEN with immunoresistance, mediated in part by B7-H1.

Purpose Gliomas are known to induce local and systemic immunosuppression, inhibiting T cell-mediated cytotoxic responses to tumor growth. Tumor-associated macrophages are a significant component of the immune infiltrate in gliomas and may express immunosuppressive surface ligands, such as B7-H1. Experimental Design Tumor and peripheral blood samples from patients with glioblastoma (GBM) were analyzed by flow cytometry to evaluate the expression of B7-H1 in circulating and tumor-infiltrating macrophages. Human monocytes from healthy patients were stimulated with conditioned media from glioma cells to evaluate B7-H1 expression. Production of IL-10 by stimulated monocytes was measured by ELISA, and stimulation with IL-10 alone was evaluated for the ability to induce B7-H1 expression. The effect of inhibiting IL-10 and its receptor on glioma-induced B7-H1 expression in monocytes was evaluated. Results Circulating monocytes in patients with GBM had significantly increased expression of B7-H1 compared to healthy control patients. Tumor-associated macrophages from matched GBM tissue had even greater B7-H1 expression. Treatment of normal monocytes with glioma conditioned media could significantly increase B7-H1 expression. Stimulation of monocytes with conditioned media resulted in substantial production of IL-10 and upregulation of the IL-10 receptor. Stimulation of monocytes with IL-10 alone could significantly increase B7-H1 expression, sufficient to induce T cell apoptosis when co-cultured with stimulated monocytes. Inhibition of IL-10 and the IL-10 receptor could knock down the effect of glioma media on B7-H1 by greater than 50%. Conclusions Gliomas can upregulate B7-H1 expression in circulating monocytes and tumor-infiltrative macrophages through modulation of autocrine/paracrine IL-10 signaling, resulting in an immunosuppressive phenotype.

Purpose BRAF V600E is a potentially highly targetable mutation detected in a subset of pediatric low-grade gliomas (PLGGs). Its biologic and clinical effect within this diverse group of tumors remains unknown. Patients and MethodsA combined clinical and genetic institutional study of patients with PLGGs with long-term follow-up was performed (N = 510). Clinical and treatment data of patients with BRAF V600E mutated PLGG (n = 99) were compared with a large international independent cohort of patients with BRAF V600E mutated-PLGG (n = 180).Results BRAF V600E mutation was detected in 69 of 405 patients (17%) with PLGG across a broad spectrum of histologies and sites, including midline locations, which are not often routinely biopsied in clinical practice. Patients with BRAF V600E PLGG exhibited poor outcomes after chemotherapy and radiation therapies that resulted in a 10-year progression-free survival of 27% (95% CI, 12.1% to 41.9%) and 60.2% (95% CI, 53.3% to 67.1%) for BRAF V600E and wild-type PLGG, respectively (P , .001). Additional multivariable clinical and molecular stratification revealed that the extent of resection and CDKN2A deletion contributed independently to poor outcome in BRAF V600E PLGG. A similar independent role for CDKN2A and resection on outcome were observed in the independent cohort. Quantitative imaging analysis revealed progressive disease and a lack of response to conventional chemotherapy in most patients with BRAF V600E PLGG. ConclusionBRAF V600E PLGG constitutes a distinct entity with poor prognosis when treated with current adjuvant therapy. response to therapy and clinical outcome is still not known. As a result, as far as nonsurgical treatment is concerned, all patients with PLGGs receive similar treatment independent of their tumor's molecular alterations. 6 For deeply located tumors, such as hypothalamic/chiasmatic LGGs, the need for biopsy before treatment decisions are made for these children is still debated.The BRAF V600E mutation, which is observed in a variety of adult 7 and pediatric neoplasms, is thought to be present in only a small percentage of PLGGs.8 Controversy still exists as to whether BRAF V600E-mutant PLGG constitutes a unique subgroup with respect to natural history and outcome. 9,10 We have previously reported that PLGGs that transform to high-grade gliomas have a high incidence of BRAF V600E mutations in combination with CDKN2A deletion.11 CDKN2A is a tumor suppressor gene and a key regulator of the cell cycle. CDKN2A alterations act as a secondary hit, which allows for escape from cell cycle regulation and malignant behavior in multiple cancer types. 12,13 In PLGGs, CDKN2A loss has been reported to be associated with escape from oncogene-induced senescence, 14 especially when combined with BRAF mutations.To better define the clinical significance of BRAF V600E in these tumors, we performed a combined clinical and genetic analysis in an institutional discovery cohort of patients with PLGG who were diagnosed and treated in southern Ontario. 15 We then asse...