Background: Glioblastoma (GBM) is the most common primary malignant brain cancer in adults, with very limited therapeutic options. It is characterized by a severe immunosuppressive milieu mostly triggered by suppressive CD163⁺ tumor-associated macrophages (TAMs). The efficacy of immune checkpoint inhibitor interventions aimed at rescuing anti-tumor immunity has not been proved to date. Thus, it is critically important to investigate the immunomodulatory mechanisms acting within the GBM microenvironment for the better design of immunotherapeutic strategies. Methods: The immunohistochemical analysis of a panel of immune biomarkers (CD3, FoxP3, CD163, IDO, PDL-1, PD-1 and TIGIT) was performed in paired samples of the tumor core (TC) and peritumoral area (PTA) of nine GBM patients. Results: CD163⁺ cells were the most common cell type in both the PTA and TC. IDO and PDL-1 were expressed in most of the TC samples, frequently accompanied by TIGIT expression; on the contrary, they were almost absent in the PTA. CD3⁺ cells were present in both the TC and PTA, to a lesser extent than CD163⁺ cells; they often were accompanied by PD-1 expression, especially in the TC. FoxP3 was scarcely present. Conclusion: Distinct inhibitory mechanisms can act simultaneously in both the TC and PTA to contribute to the strong immunosuppression observed within the GBM microenvironment. Nevertheless, the PTA shows strongly reduced immunosuppression when compared to the TC, thus representing a potential target for immunotherapies. Moreover, our results support the working hypothesis that immunosuppression and T-cell exhaustion can be simultaneously targeted to rescue anti-tumor immunity in GBM patients.

Background: A prospective 2002–2014 study stratified 160 patients by resection extent and histological grade, reporting results in 2016. We re-analyzed the series after a median of 119 months, adding retrospectively patients’ molecular features.Methods: Follow-up of all patients was updated. DNA copy number analysis and gene-fusion detection could be completed for 94/160 patients, methylation classification for 68.Results: Progression-free survival (PFS) and overall survival (OS) at 5/10 years were 66/58%, and 80/73%. Ten patients had late relapses (range 66–126 mo), surviving after relapse no longer than those relapsing earlier (0–5 y). On multivariable analysis a better PFS was associated with grade II tumor and complete surgery at diagnosis and/or at radiotherapy; female sex and complete resection showed a positive association with OS. Posterior fossa (PF) tumors scoring ≥0.80 on DNA methylation analysis were classified as PFA (n = 41) and PFB (n = 9). PFB patients had better PFS and OS. Eighteen/32 supratentorial tumors were classified as RELA, and 3 as other molecular entities (anaplastic PXA, LGG MYB, HGNET). RELA had no prognostic impact. Patients with 1q gain or cyclin-dependent kinase inhibitor 2A (CDKN2A) loss had worse outcomes, included significantly more patients >3 years old (P = 0.050) and cases of dissemination at relapse (P = 0.007).Conclusions: Previously described prognostic factors were confirmed at 10-year follow-up. Late relapses occurred in 6.2% of patients. Specific molecular features may affect outcome: PFB patients had a very good prognosis; 1q gain and CDKN2A loss were associated with dissemination. To draw reliable conclusions, modern ependymoma trials need to combine diagnostics with molecular risk stratification and long-term follow-up.

Purpose: The maintenance of telomere length prevents cancer cell senescence and occurs via two mutually exclusive mechanisms: (a) reactivation of telomerase expression and (b) activation of alternative lengthening of telomeres (ALT). ALT is frequently related to alterations on ATRX, a chromatin-remodelling protein. Recent data have identified different molecular subgroups of paediatric high-grade glioma (pHGG) with mutations of H3F3A, TERTp and ATRX; however, differences in telomere length among these molecular subgroups were not thoroughly examined. Methods: We investigated which genetic alterations trigger the ALT mechanism in 52 IDH-wildtype, 1p/19q-wildtype pHGG. Samples were analysed for telomere length using Tel-FISH. ATRX nuclear loss of expression was assessed by IHC, H3F3A and TERTp mutations by DNA sequencing, and TERTp methylation by MS-PCR. Results: Mutant H3.3 was found in 21 cases (40.3%): 19.2% with K27M mutation and 21.1% with G34R mutation. All H3.3G34R-mutated cases showed the ALT phenotype (100%); on the opposite, only 40% of the H3.3K27M-mutated showed ALT activation. ATRX nuclear loss was seen in 16 cases (30.7%), associated sometimes with the G34R mutation, and never with the K27M mutation. ATRX nuclear loss was always related to telomere elongation. TERTp C250T mutations were rare (5.4%) and were not associated with high intensity Tel-FISH signals, as TERTp hyper-methylation detected in 21% of the cases. H3.3/ATRX/TERTp-wildtype pHGG revealed all basal levels of telomere length. Conclusion: Our results show a strong association between H3.3 mutations and ALT, and highlight the different telomeric profiles in histone-defined subgroups: H3.3-G34R mutants always trigger ALT to maintain telomere length, irrespective of ATRX status, whereas only some H3.3-K27M tumours activate ALT. These findings suggest that acquiring the gly34 mutation on H3.3 might suffice to trigger the ALT mechanism.

Recurrent glycine-to-arginine/valine alterations at codon 34 (G34R/V) within H3F3A gene characterize a subset of hemispheric high-grade gliomas (HGG) affecting children and young adults. These tumors, defined as G34R/V-mutant gliomas, are histologically heterogenous, with microscopic features of either HGG or embryonal tumors (primitve neuroectodermal tumor-like features). To assess the value of immunohistochemistry (IHC) to detect G34R/V-mutated cases, we tested anti-histone G34V (clone 329E5) and anti-histone G34R (clone RM240) antibodies in a series of 28 formalin-fixed and paraffin-embedded samples. A total of 28 cases of hemispheric, IDH-wt HGG mainly affecting children and young adults were evaluated by IHC and by sequencing. The median age of patients at diagnosis was 17 years (0.1 to 26 y). By IHC, 10 of the 28 cases showed nuclear positivity for G34R and 3 of the 28 cases for G34V. Molecular analysis of G34R/V-mutation status was successful in 24 of the 28 cases. Mutation at glycine 34 of the H3F3A gene was identified in 9 of the 24 tumors (37%) by direct sequencing, revealing 7 of 9 positive case by sequencing and 2 of 9 false negative cases by IHC. Two of 15 negative case by sequencing demonstrated a false positivity by IHC. In total, in 4 (16.6%) of 24 cases, IHC and mutational results were discordant: 2 tumors were negative by IHC (false negative) but harbored G34R mutation by sequencing, and 2 cases were positive by IHC (false positive by IHC) but wild type by sequencing. Moreover, most mutated cases showed loss of ATRX expression and/or p53 expression. The positivity by IHC with specific antibody tested is not highly predictive for presence of G34R/V mutation, but confirmation by sequencing is mandatory; G34R/V mutations should be suspected in all hemispheric tumor IDH1/2 wild type, showing loss of OLIG2 and ATRX and/or p53 expression.