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Diffuse gliomas are up till now graded based upon morphology. Recent findings indicate that isocitrate dehydrogenase (IDH) mutation status defines biologically distinct groups of tumors. The role of tumor grade and mitotic index in patient outcome has not been evaluated following stratification by IDH mutation status. To address this, we interrogated 558 WHO grade II–III diffuse gliomas for IDH1/2 mutations and investigated the prognostic impact of WHO grade within IDH-mutant and wild-type tumor subsets independently. The prognostic impact of grade was modest in IDH-mutant [hazard ratio (HR)=1.21, 95% confidence interval (CI)=0.91–1.61] compared to IDH-wild type tumors (HR=1.74, 95% CI=0.95–3.16). Using a dichotomized mitotic index cut-off of 4/1000 tumor cells, we found that while mitotic index was significantly associated with outcome in IDH-wild type tumors (log-rank p<0.0001, HR=4.41, 95% CI=2.55–7.63), it was not associated with outcome in IDH-mutant tumors (log-rank p=0.5157, HR=1.10, 95% CI=0.80–1.51), and could demonstrate a statistical interaction (p<0.0001) between IDH mutation and mitotic index (i.e. suggesting that the effect of mitotic index on patient outcome is dependent on IDH mutation status). Patient age, an established prognostic factor in diffuse glioma, was significantly associated with outcome only in the IDH-wild type subset, and consistent with prior data, 1p/19q co-deletion conferred improved outcome in the IDH-mutant cohort. These findings suggest that stratification of grade II–III gliomas into subsets defined by the presence or absence of IDH mutation leads to subgroups with distinct prognostic characteristics. Further evaluation of grading criteria and prognostic markers is warranted within IDH-mutant versus IDH-wild type diffuse grade II–III gliomas as independent entities.

Neurofibromatosis type 1 (NF1) is a common tumor predisposition syndrome in which glioma is one of the prevalent tumors. Gliomagenesis in NF1 results in a heterogeneous spectrum of low- to high-grade neoplasms occurring during the entire lifespan of patients. The pattern of genetic and epigenetic alterations of glioma that develops in NF1 patients and the similarities with sporadic glioma remain unknown. Here, we present the molecular landscape of low- and high-grade gliomas in patients affected by NF1 (NF1-glioma). We found that the predisposing germline mutation of the NF1 gene was frequently converted to homozygosity and the somatic mutational load of NF1-glioma was influenced by age and grade. High-grade tumors harbored genetic alterations of TP53 and CDKN2A, frequent mutations of ATRX associated with Alternative Lengthening of Telomere, and were enriched in genetic alterations of transcription/chromatin regulation and PI3 kinase pathways. Low-grade tumors exhibited fewer mutations that were over-represented in genes of the MAP kinase pathway. Approximately 50% of low-grade NF1-gliomas displayed an immune signature, T lymphocyte infiltrates, and increased neo-antigen load. DNA methylation assigned NF1-glioma to LGm6, a poorly defined Isocitrate Dehydrogenase 1 wild-type subgroup enriched with ATRX mutations. Thus, the profiling of NF1-glioma defined a distinct landscape that recapitulates a subset of sporadic tumors.

Background We sought to ascertain the immune effector function of pembrolizumab within the glioblastoma (GBM) microenvironment during the therapeutic window. Methods In an open-label, single-center, single-arm phase II “window-of-opportunity” trial in 15 patients with recurrent (operable) GBM receiving up to 2 pembrolizumab doses before surgery and every 3 weeks afterward until disease progression or unacceptable toxicities occurred, immune responses were evaluated within the tumor. Results No treatment-related deaths occurred. Overall median follow-up time was 50 months. Of 14 patients monitored, 10 had progressive disease, 3 had a partial response, and 1 had stable disease. Median progression-free survival (PFS) was 4.5 months (95% CI: 2.27, 6.83), and the 6-month PFS rate was 40%. Median overall survival (OS) was 20 months, with an estimated 1-year OS rate of 63%. GBM patients’ recurrent tumors contained few T cells that demonstrated a paucity of immune activation markers, but the tumor microenvironment was markedly enriched for CD68+ macrophages. Conclusions Immune analyses indicated that pembrolizumab anti–programmed cell death 1 (PD-1) monotherapy alone can’t induce effector immunologic response in most GBM patients, probably owing to a scarcity of T cells within the tumor microenvironment and a CD68+ macrophage preponderance.

IntroductionIsocitrate dehydrogenase (IDH) mutation status and grade define subgroups of diffuse gliomas differing based on age, tumor location, presentation, and prognosis. While some biologic differences between IDH mutated (IDHmut) and wild-type (IDHwt) gliomas are clear, the distinct alterations associated with progression of the two subtypes to glioblastoma (GBM, Grade IV) have not been well described. We analyzed copy number alterations (CNAs) across grades (Grade II–III and GBM) in both IDHmut and IDHwt infiltrating gliomas using molecular inversion probe arrays.ResultsNinety four patient samples were divided into four groups: Grade II–III IDHwt (n = 17), Grade II–III IDHmut (n = 28), GBM IDHwt (n = 25), and GBM IDHmut (n = 24). We validated prior observations that IDHwt GBM have a high frequency of chromosome 7 gain (including EGFR) and chromosome 10 loss (including PTEN) compared with IDHmut GBM. Hierarchical clustering of IDHmut gliomas demonstrated distinct CNA patterns distinguishing lower grade gliomas versus GBM. However, similar hierarchical clustering of IDHwt gliomas demonstrated no CNA distinction between lower grade glioma and GBM. Functional analyses showed that IDHwt gliomas had more chromosome gains in regions containing receptor tyrosine kinase pathways. In contrast, IDHmut gliomas more commonly demonstrated amplification of cyclins and cyclin dependent kinase genes. One of the most common alterations associated with transformation of lower grade to GBM IDHmut gliomas was the loss of chromosomal regions surrounding PTEN. IDHmut GBM tumors demonstrated significantly higher levels of overall CNAs compared to lower grade IDHmut tumors and all grades of IDHwt tumors, and IDHmut GBMs also demonstrated significant increase in incidence of chromothripsis.ConclusionsTaken together, these analyses demonstrate distinct molecular ontogeny between IDHwt and IDHmut gliomas. Our data also support the novel findings that malignant progression of IDHmut gliomas to GBM involves increased genomic instability and genomic catastrophe, while IDHwt lower grade tumors are virtually identical to GBMs at the level of DNA copy number alterations.Electronic supplementary materialThe online version of this article (doi:10.1186/s40478-015-0213-3) contains supplementary material, which is available to authorized users.