The molecular landscape of ETMR at diagnosis and relapse.

Embryonal tumours with multilayered rosettes (ETMRs) are aggressive paediatric embryonal brain tumours with a universally poor prognosis1. Here we collected 193 primary ETMRs and 23 matched relapse samples to investigate the genomic landscape of this distinct tumour type. We found that patients with tumours in which the proposed driver C19MC2-4 was not amplified frequently had germline mutations in DICER1 or other microRNA-related aberrations such as somatic amplification of miR-17-92 (also known as MIR17HG). Whole-genome sequencing revealed that tumours had an overall low recurrence of single-nucleotide variants (SNVs), but showed prevalent genomic instability caused by widespread occurrence of R-loop structures. We show that R-loop-associated chromosomal instability can be induced by the loss of DICER1 function. Comparison of primary tumours and matched relapse samples showed a strong conservation of structural variants, but low conservation of SNVs. Moreover, many newly acquired SNVs are associated with a mutational signature related to cisplatin treatment. Finally, we show that targeting R-loops with topoisomerase and PARP inhibitors might be an effective treatment strategy for this deadly disease.

GluK2 Is a Target for Gene Therapy in Drug-Resistant Temporal Lobe Epilepsy.

OBJECTIVE: Temporal lobe epilepsy (TLE) is characterized by recurrent seizures generated in the limbic system, particularly in the hippocampus. In TLE, recurrent mossy fiber sprouting from dentate gyrus granule cells (DGCs) crea an aberrant epileptogenic network between DGCs which operates via ectopically expressed GluK2/GluK5-containing kainate receptors (KARs). TLE patients are often resistant to anti-seizure medications and suffer significant comorbidities; hence, there is an urgent need for novel therapies. Previously, we have shown that GluK2 knockout mice are protected from seizures. This study aims at providing evidence that downregulating KARs in the hippocampus using gene therapy reduces chronic epileptic discharges in TLE. METHODS: We combined molecular biology and electrophysiology in rodent models of TLE and in hippocampal slices surgically resected from patients with drug-resistant TLE. RESULTS: Here, we confirmed the translational potential of KAR suppression using a non-selective KAR antagonist that markedly attenuated interictal-like epileptiform discharges (IEDs) in TLE patient-derived hippocampal slices. An adeno-associated virus (AAV) serotype-9 vector expressing anti-grik2 miRNA was engineered to specifically downregulate GluK2 expression. Direct delivery of AAV9-anti grik2 miRNA into the hippocampus of TLE mice led to a marked reduction in seizure activity. Transduction of TLE patient hippocampal slices reduced levels of GluK2 protein and, most importantly, significantly reduced IEDs. INTERPRETATION: Our gene silencing strategy to knock down aberrant GluK2 expression demonstrates inhibition of chronic seizure in a mouse TLE model and IEDs in cultured slices derived from TLE patients. These results provide proof-of-concept for a gene therapy approach targeting GluK2 KARs for drug-resistant TLE patients. ANN NEUROL 2023;94:745-761.

Descriptive epidemiology of 30,223 histopathologically confirmed meningiomas in France: 2006-2015.

BACKGROUND AND OBJECTIVES: Meningioma is one of the most common neoplasm of the central nervous system. To describe the epidemiology of meningioma operated in France and, to assess grading and histopathological variability among the different neurosurgical centres. METHODS: We processed the French Brain Tumour Database (FBTDB) to conduct a nationwide population-based study of all histopathologically confirmed meningiomas between 2006 and 2015. RESULTS: 30,223 meningiomas cases were operated on 28,424 patients, in 61 centres. The average number of meningioma operated per year in France was 3,022 (SD ± 122). Meningioma was 3 times more common in women (74.1% vs. 25.9%). The incidence of meningioma increased with age and, mean age at surgery was 58.5 ± 13.9 years. Grade 1, 2, and 3 meningiomas accounted for 83.9%, 13.91% and, 2.19% respectively. There was a significant variability of meningioma grading by institutions, especially for grade 2 which spanned from 5.1% up to 22.4% (p < 0.001). Moreover, the proportion of grade 2 significantly grew over the study period (p < 0.001). There was also a significant variation in grade 1 subtypes diagnosis among the institutions (p < 0.001). 89.05% of the patients had solely one meningioma surgery, 8.52% two and, 2.43% three or more. The number of surgeries was associated to the grade of malignancy (p < 0.001). CONCLUSION: The incidence of meningioma surgery increased with age and, peaked at 58.5 years. They were predominantly benign with meningothelial subtype being the most common. However, there was a significant variation of grade 1 subtypes diagnosis among the centres involved. The proportion of grade 2 meningioma significantly grew over the study time, on contrary to malignant meningioma proportion, which remained rare and, stable over time around 2%. Likewise, there was a significant variability of grade 2 meningioma rate among the institutions.

Pediatric spinal pilocytic astrocytomas form a distinct epigenetic subclass from pilocytic astrocytomas of other locations and diffuse leptomeningeal glioneuronal tumours.

Pediatric spinal low-grade glioma (LGG) and glioneuronal tumours are rare, accounting for less 2.8-5.2% of pediatric LGG. New tumour types frequently found in spinal location such as diffuse leptomeningeal glioneuronal tumours (DLGNT) have been added to the World Health Organization (WHO) classification of tumours of the central nervous system since 2016, but their distinction from others gliomas and particularly from pilocytic astrocytoma (PA) are poorly defined. Most large studies on this subject were published before the era of the molecular diagnosis and did not address the differential diagnosis between PAs and DLGNTs in this peculiar location. Our study retrospectively examined a cohort of 28 children with LGGs and glioneuronal intramedullary tumours using detailed radiological, clinico-pathological and molecular analysis. 25% of spinal PAs were reclassified as DLGNTs. PA and DLGNT are nearly indistinguishable in histopathology or neuroradiology. 83% of spinal DLGNTs presented first without leptomeningeal contrast enhancement. Unsupervised t-distributed stochastic neighbor embedding (t-SNE) analysis of DNA methylation profiles showed that spinal PAs formed a unique methylation cluster distinct from reference midline and posterior fossa PAs, whereas spinal DLGNTs clustered with reference DLGNT cohort. FGFR1 alterations were found in 36% of spinal tumours and were restricted to PAs. Spinal PAs affected significantly younger patients (median age 2 years old) than DLGNTs (median age 8.2 years old). Progression-free survival was similar among the two groups. In this location, histopathology and radiology are of limited interest, but molecular data (methyloma, 1p and FGFR1 status) represent important tools differentiating these two mitogen-activated protein kinase (MAPK) altered tumour types, PA and DLGNT. Thus, these molecular alterations should systematically be explored in this type of tumour in a spinal location.

Amplification of the PLAG-family genes-PLAGL1 and PLAGL2-is a key feature of the novel tumor type CNS embryonal tumor with PLAGL amplification.

Pediatric central nervous system (CNS) tumors represent the most common cause of cancer-related death in children aged 0-14 years. They differ from their adult counterparts, showing extensive clinical and molecular heterogeneity as well as a challenging histopathological spectrum that often impairs accurate diagnosis. Here, we use DNA methylation-based CNS tumor classification in combination with copy number, RNA-seq, and ChIP-seq analysis to characterize a newly identified CNS tumor type. In addition, we report histology, patient characteristics, and survival data in this tumor type. We describe a biologically distinct pediatric CNS tumor type (n = 31 cases) that is characterized by focal high-level amplification and resultant overexpression of either PLAGL1 or PLAGL2, and an absence of recurrent genetic alterations characteristic of other pediatric CNS tumor types. Both genes act as transcription factors for a regulatory subset of imprinted genes (IGs), components of the Wnt/ß-Catenin pathway, and the potential drug targets RET and CYP2W1, which are also specifically overexpressed in this tumor type. A derived PLAGL-specific gene expression signature indicates dysregulation of imprinting control and differentiation/development. These tumors occurred throughout the neuroaxis including the cerebral hemispheres, cerebellum, and brainstem, and were predominantly composed of primitive embryonal-like cells lacking robust expression of markers of glial or neuronal differentiation (e.g., GFAP, OLIG2, and synaptophysin). Tumors with PLAGL1 amplification were typically diagnosed during adolescence (median age 10.5 years), whereas those with PLAGL2 amplification were diagnosed during early childhood (median age 2 years). The 10-year overall survival was 66% for PLAGL1-amplified tumors, 25% for PLAGL2-amplified tumors, 18% for male patients, and 82% for female patients. In summary, we describe a new type of biologically distinct CNS tumor characterized by PLAGL1/2 amplification that occurs predominantly in infants and toddlers (PLAGL2) or adolescents (PLAGL1) which we consider best classified as a CNS embryonal tumor and which is associated with intermediate survival. The cell of origin and optimal treatment strategies remain to be defined.

Natural history of spinal cord metastasis from brain glioblastomas.

BACKGROUND AND OBJECTIVES: Spinal cord metastasis arising from an intracranial glioblastoma is a rare and late event during the natural course of the disease. These pathological entities remain poorly characterized. This study aimed to identify and investigate the timeline, clinical and imaging findings, and prognostic factors of spinal cord metastasis from a glioblastoma. METHODS: Consecutive histopathological cases of spinal cord metastasis from glioblastomas in adults entered in the French nationwide database between January 2004 and 2016 were screened. RESULTS: Overall, 14 adult patients with a brain glioblastoma (median age 55.2 years) and harboring a spinal cord metastasis were included. The median overall survival as 16.0 months (range, 9.8-22.2). The median spinal cord Metastasis Free Survival (time interval between the glioblastoma diagnosis and the spinal cord metastasis diagnosis) was 13.6 months (range, 0.0-27.9). The occurrence of a spinal cord metastasis diagnosis greatly impacted neurological status: 57.2% of patients were not ambulatory, which contributed to dramatically decreased Karnofsky Performance Status (KPS) scores (12/14, 85.7% with a KPS score ≤ 70). The median overall survival following spinal cord metastasis was 3.3 months (range, 1.3-5.3). Patients with a cerebral ventricle effraction during the initial brain surgery had a shorter spinal cord Metastasis Free Survival (6.6 vs 18.3 months, p = 0.023). Out of the 14 patients, eleven (78.6%) had a brain IDH-wildtype glioblastoma. CONCLUSIONS: Spinal cord metastasis from a brain IDH-wildtype glioblastoma has a poor prognosis. Spinal MRI can be proposed during the follow-up of glioblastoma patients especially those who have benefited from cerebral surgical resection with opening of the cerebral ventricles.

T2-Fluid-attenuated inversion recovery (FLAIR) pseudoprogression in patients with anaplastic oligodendrogliomas treated with procarbazine, lomustine and vincristine (PCV) chemotherapy alone.

BACKGROUND: Pseudoprogression in gliomas has been extensively described after radiotherapy with or without chemotherapy, but not after chemotherapy alone. Here we describe the occurrence of pseudoprogression in patients with anaplastic oligodendrogliomas treated with postoperative procarbazine, lomustine and vincristine (PCV) chemotherapy alone. METHODS: We retrospectively reviewed the medical and radiological files of patients with 1p/19q codeleted, IDH-mutant anaplastic oligodendrogliomas treated with PCV chemotherapy alone who presented magnetic resonance imaging (MRI) modifications suggestive of tumour progression and in whom the final diagnosis was a pseudoprogression. RESULTS: We identified six patients. All patients underwent a surgical resection and were treated with PCV chemotherapy without radiotherapy. After a median of 11 months following the initiation of chemotherapy (range: 3-49 months), the patients developed asymptomatic white matter MRI modifications around the surgical cavity leading to the suspicion of a tumour progression. These modifications appeared as hyperintense on T2-fluid-attenuated inversion recovery (FLAIR) sequence, hypointense on T1 sequence, and lacked mass effect (0/6), contrast enhancement (0/6), restriction on diffusion-weighted imaging (0/4), relative cerebral blood volume (rCBV) increase on perfusion MRI (0/4), and hypermetabolism on 18 F-fluoro-L-dopa positron emission tomography (18 F-DOPA PET) scan (0/3). One patient underwent a surgical resection demonstrating no tumour recurrence; the five other patients were considered as having post-therapeutic modifications based on imaging characteristics. After a median follow-up of 4 years all patients were progression-free. CONCLUSIONS: Anaplastic oligodendroglioma patients treated with postoperative PCV chemotherapy alone occasionally develop T2/FLAIR hyperintensities around the surgical cavity that can wrongly suggest tumour progression. Multimodal imaging and close follow-up should be considered in this situation.

Deciphering the Action of Neuraminidase in Glioblastoma Models.

Glioblastoma (GBM) contains cancer stem cells (CSC) that are resistant to treatment. GBM CSC expresses glycolipids recognized by the A2B5 antibody. A2B5, induced by the enzyme ST8 alpha-N-acetyl-neuraminide alpha-2,8-sialyl transferase 3 (ST8Sia3), plays a crucial role in the proliferation, migration, clonogenicity and tumorigenesis of GBM CSC. Our aim was to characterize the resulting effects of neuraminidase that removes A2B5 in order to target GBM CSC. To this end, we set up a GBM organotypic slice model; quantified A2B5 expression by flow cytometry in U87-MG, U87-ST8Sia3 and GBM CSC lines, treated or not by neuraminidase; performed RNAseq and DNA methylation profiling; and analyzed the ganglioside expression by liquid chromatography-mass spectrometry in these cell lines, treated or not with neuraminidase. Results demonstrated that neuraminidase decreased A2B5 expression, tumor size and regrowth after surgical removal in the organotypic slice model but did not induce a distinct transcriptomic or epigenetic signature in GBM CSC lines. RNAseq analysis revealed that OLIG2, CHI3L1, TIMP3, TNFAIP2, and TNFAIP6 transcripts were significantly overexpressed in U87-ST8Sia3 compared to U87-MG. RT-qPCR confirmed these results and demonstrated that neuraminidase decreased gene expression in GBM CSC lines. Moreover, neuraminidase drastically reduced ganglioside expression in GBM CSC lines. Neuraminidase, by its pleiotropic action, is an attractive local treatment against GBM.

Characteristics of Anaplastic Oligodendrogliomas Short-Term Survivors: A POLA Network Study.

BACKGROUND: Anaplastic oligodendrogliomas IDH-mutant and 1p/19q codeleted (AO) occasionally have a poor outcome. Herein we aimed at analyzing their characteristics. METHODS: We retrospectively analyzed the characteristics of 44 AO patients with a cancer-specific survival <5 years (short-term survivors, STS) and compared them with those of 146 AO patients with a survival ≥5 years (classical survivors, CS) included in the POLA network. RESULTS: Compared to CS, STS were older (P = .0001), less frequently presented with isolated seizures (P < .0001), more frequently presented with cognitive dysfunction (P < .0001), had larger tumors (P = .= .003), a higher proliferative index (P = .= .0003), and a higher number of chromosomal arm abnormalities (P = .= .02). Regarding treatment, STS less frequently underwent a surgical resection than CS (P = .= .0001) and were more frequently treated with chemotherapy alone (P = .= .009) or with radiotherapy plus temozolomide (P = .= .05). Characteristics independently associated with STS in multivariate analysis were cognitive dysfunction, a number of mitosis > 8, and the absence of tumor resection. Based on cognitive dysfunction, type of surgery, and number of mitosis, patients could be classified into groups of standard (18%) and high (62%) risk of <5 year survival. CONCLUSION: The present study suggests that although STS poor outcome appears to largely result from a more advanced disease at diagnosis, surgical resection may be particularly important in this population.

Low-grade epilepsy-associated neuroepithelial tumours with a prominent oligodendroglioma-like component: The diagnostic challenges.

AIMS: We searched for recurrent pathological features and molecular alterations in a retrospective series of 72 low-grade epilepsy-associated neuroepithelial tumours (LEATs) with a prominent oligodendroglioma-like component, in order to classify them according to the 2021 World Health Organization (WHO) classification of central nervous system (CNS) tumours. METHODS: Centralised pathological examination was performed as well as targeted molecular analysis of v-Raf murine sarcoma viral oncogene homologue B (BRAF) and fibroblast growth factor receptor 1 (FGFR1) by multiplexed digital polymerase chain reaction (mdPCR). DNA methylation profiling was performed in cases with sufficient DNA. In cases with no genetic alteration by mdPCR and sufficient material, RNA sequencing was done. RESULTS: We first reclassified our cohort into three groups: ganglioglioma (GG, n = 14), dysembryoplastic neuroepithelial tumours (DNTs, n = 19) and glioneuronal tumours/paediatric-type low-grade glioma (LGG) not otherwise specified (GNT/PLGG NOS, n = 39). mdPCR found an alteration in 38/72 cases. Subsequent RNA sequencing revealed a fusion transcript involving BRAF, FGFR1/2/3 or neurotrophic tyrosine kinase receptor type 2 [NTRK2] in 9/25 cases. DNA methylation profiling found 12/46 cases with a calibrated score ≥0.9. Unsupervised hierarchical clustering revealed two clusters: Cluster 1 was enriched with cases classified as DNT at histology, belonging to the LGG-DNT methylation class (MC), with haematopoietic progenitor cell antigen (CD34) negativity and FGRF1 alterations; Cluster 2 was enriched with cases classified at histology as GG, belonging to the LGG-GG MC MC, with BRAF V600E mutation and CD34 positivity. The tumours reclassified as GNT/PLGG NOS were equally distributed across both clusters. Interestingly, all polymorphous low-grade neuroepithelial tumour of the young belonged to Cluster 2, whereas diffuse LGG mitogen-activated protein kinase (MAPK) pathway-altered were equally distributed among the two clusters. This led us to build an algorithm to classify LEATs with a prominent oligodendroglioma-like component. CONCLUSIONS: Integrated histomolecular diagnosis of LEATs with a prominent oligodendroglioma-like component remains challenging. Because these tumours can be split into two major clusters of biological significance, the clinicopathological relevance of the four types recognised by the WHO CNS5 within this spectrum of tumours is questionable.

The genomic landscape of dysembryoplastic neuroepithelial tumours and a comprehensive analysis of recurrent cases.

AIMS: Dysembryoplastic neuroepithelial tumour (DNT) is a glioneuronal tumour that is challenging to diagnose, with a wide spectrum of histological features. Three histopathological patterns have been described: specific DNTs (both the simple form and the complex form) comprising the specific glioneuronal element, and also the non-specific/diffuse form which lacks it, and has unclear phenotype-genotype correlations with numerous differential diagnoses. METHODS: We used targeted methods (immunohistochemistry, fluorescence in situ hybridisation and targeted sequencing) and large-scale genomic methodologies including DNA methylation profiling to perform an integrative analysis to better characterise a large retrospective cohort of 82 DNTs, enriched for tumours that showed progression on imaging. RESULTS: We confirmed that specific DNTs are characterised by a single driver event with a high frequency of FGFR1 variants. However, a subset of DNA methylation-confirmed DNTs harbour alternative genomic alterations to FGFR1 duplication/mutation. We also demonstrated that a subset of DNTs sharing the same FGFR1 alterations can show in situ progression. In contrast to the specific forms, "non-specific/diffuse DNTs" corresponded to a heterogeneous molecular group encompassing diverse, newly-described, molecularly distinct entities. CONCLUSIONS: Specific DNT is a homogeneous group of tumours sharing characteristics of paediatric low-grade gliomas: a quiet genome with a recurrent genomic alteration in the RAS-MAPK signalling pathway, a distinct DNA methylation profile and a good prognosis but showing progression in some cases. The "non-specific/diffuse DNTs" subgroup encompasses various recently described histomolecular entities, such as PLNTY and diffuse astrocytoma, MYB or MYBL1 altered.

Rosette-forming glioneuronal tumours are midline, FGFR1-mutated tumours.

AIM: Rosette-forming glioneuronal tumour (RGNT) is a rare central nervous system (CNS) World Health Organization (WHO) grade 1 brain neoplasm. According to the WHO 2021, essential diagnostic criteria are a 'biphasic histomorphology with neurocytic and a glial component, and uniform neurocytes forming rosettes and/or perivascular pseudorosettes associated with synaptophysin expression' and/or DNA methylation profile of RGNT whereas 'FGFR1 mutation with co-occurring PIK3CA and/or NF1 mutation' are desirable criteria. MATERIAL AND METHODS: We report a series of 46 cases fulfilling the essential pathological diagnostic criteria for RGNT. FGFR1 and PIK3CA hotspot mutations were searched for by multiplexed digital PCR in all cases, whereas DNA methylation profiling and/or PIK3R1 and NF1 alterations were analysed in a subset of cases. RESULTS: Three groups were observed. The first one included 21 intracranial midline tumours demonstrating FGFR1 mutation associated with PIK3CA or PIK3R1 (n = 19) or NF1 (n = 1) or PIK3CA and NF1 (n = 1) mutation. By DNA methylation profiling, eight cases were classified as RGNT (they demonstrated FGFR1 and PIK3CA or PIK3R1 mutations). Group 2 comprised 11 cases associated with one single FGFR1 mutation. Group 3 included six cases classified as low-grade glioma (LGG) other than RGNT (one-sixth showed FGFR1 mutation and one a FGFR1 and NF1 mutation) and eight cases without FGFR1 mutation. Groups 2 and 3 were enriched in lateral and spinal cases. CONCLUSIONS: We suggest adding FGFR1 mutation and intracranial midline location as essential diagnostic criteria. When DNA methylation profiling is not available, a RGNT diagnosis remains certain in cases demonstrating characteristic pathological features and FGFR1 mutation associated with either PIK3CA or PIK3R1 mutation.

Adult H3K27M mutated thalamic glioma patients display a better prognosis than unmutated patients.

BACKGROUND: Adult thalamic gliomas are a rare entity whose management is challenging for physicians. The aim of this study is to describe the characteristics and prognostic factors of thalamic gliomas in adult patients. METHODS: We retrospectively analyzed the clinical, neuro-radiological, histological, and molecular characteristics of all cases of adult thalamic glioma in our regional center. RESULTS: We included 38 adult patients. Median age at diagnosis was 56.5 years old (range, 24-80). Median KPS at diagnosis was 70%. Two-thirds of patients presented with tumor necrosis on MRI. Bithalamic lesions were present in four patients. The median volume of enhancement associated with lesions was relatively small (14 mm3). Two patients had undergone partial surgical resection. All other patients underwent biopsy. Median PFS was 7.1 months (95% CI [3.7-10.5]) and median OS was 15.6 months (95% CI [11.7-19.6]). Among 20 patients with available tumor samples for molecular analyses, only 4 (20%) presented with H3K27M mutation. Patients with H3K27M mutation had longer survival compared to those without. Finally, we identified a long-term survivor population characterized by a younger age, no cognitive impairment, low steroid dose treatment and the presence of H3K27M mutation. CONCLUSION: Thalamic adult glioma differs from bithalamic glioma in children with regards to its clinical, radiological and molecular profiles. Long-term survival is observed in young patients with limited symptoms and H3K27M mutation. A larger prospective cohort is needed to validate these findings.

The role of irinotecan-bevacizumab as rescue regimen in children with low-grade gliomas: a retrospective nationwide study in 72 patients.

INTRODUCTION: At least half of children with low-grade glioma (LGG) treated with first line chemotherapy experience a relapse/progression and may therefore need a second-line chemotherapy. Irinotecan-bevacizumab has been recommended in this setting in France after encouraging results of pilot studies. We performed a retrospective analysis to define the efficacy, toxicity and predictors for response to the combination on a larger cohort. METHODS: We reviewed the files from children < 19 years of age with progressive or refractory LGG treated between 2009 and 2016 in 7 French centers with this combination. RESULTS: 72 patients (median age 7.8 years [range 1-19]) received a median of 16 courses (range 3-30). The median duration of treatment was 9 months (range 1.4-16.2). 96% of patients experienced at least disease stabilization. The 6-month and 2-year progression-free survivals (PFS) were 91.7% [IC 95% 85.5-98.3] and 38.2% [IC 95% 28.2-51.8] respectively. No progression occurred after treatment in 18 patients with a median follow-up of 35.6 months (range 7.6-75.9 months). Younger patients had a worse PFS (p = 0.005). Prior chemoresistance, NF1 status, duration of treatment, histopathology or radiologic response did not predict response. The most frequent toxicities related to bevacizumab included grades 1-2 proteinuria in 21, epistaxis in 10, fatigue in 12 and hypertension in 8 while gastro-intestinal toxicity was the most frequent side effect related to irinotecan. CONCLUSIONS: Bevacizumab-irinotecan has the potential of disease control clinically and radiographically in children with recurrent LGG whatever their previous characteristics; in many cases however these responses are not sustained, especially in younger children.

A2B5 Expression in Central Nervous System and Gliomas.

A2B5 IgM recognizes c-series gangliosides with three sialic acids. The aim of this review was to focus on A2B5 expression in the central nervous system and gliomas. In brain development, A2B5+ cells are recorded in areas containing multipotent neural stem cells (NSC). In adults, A2B5+ cells persist in neurogenic areas and in white matter where it identifies oligodendrocyte precursor cells (OPCs) but also cells with NSC properties. Although the expression of A2B5 has been widely studied in culture, where it characterizes bipotential glial progenitor cells, its expression in vivo is less characterized mainly because of technical issues. A new interest was given to the NSCs and OPCs since the discovery of cancer stem cells (CSC) in gliomas. Among other cell surface molecules, A2B5 has been identified as an accurate marker to identify glioma CSCs. We and others have shown that all types of gliomas express A2B5, and that only A2B5+ cells, and not A2B5- cells, can generate a tumor after orthotopic implantation in immunocompromised animals. Moreover, A2B5 epitope expression is positively correlated with stemness and tumor growth. This review highlights that A2B5 is an attractive target to tackle glioma CSCs, and a better characterization of its expression in the developing and adult CNS will benefit to a better understanding of gliomagenesis.

[The 2021 WHO classification of tumours of the central nervous system]. / La classification de l'OMS 2021 des tumeurs du système nerveux central.

Rapid technical advances in molecular biology allowed for the identification of key genetic alterations in central nervous system (CNS) tumors. Our ever-expanding knowledge of brain tumor genetics and the development of new technologies, such as DNA-methylation profiling, required an update of the 2016 fourth edition of the WHO classification of CNS tumors. Updates were regularly published by the Consortium to Inform Molecular Practical Approaches to CNS Tumor Taxonomy-Not Official WHO (c-IMPACT-NOW) until the publication of the fifth edition of the WHO classification of CNS tumors in 2021. In that edition, new types and subtypes are introduced and criteria for histo-molecular diagnostic and grading are refined, especially for diffuse gliomas. The definition of a broad category "diffuse glioma, pediatric subtype" (low or high grade) is a major improvement of the classification. Moreover, the nomenclature was simplified and aligned with that of other blue books. The 2021 edition truly advances the role of molecular diagnostics in CNS tumor classification. Methyloma profiling may become a cornerstone of CNS tumor diagnostic. The new WHO classification will lead to better management of brain tumor patients.

Radiotherapy Plus Procarbazine, Lomustine, and Vincristine Versus Radiotherapy Plus Temozolomide for IDH-Mutant Anaplastic Astrocytoma: A Retrospective Multicenter Analysis of the French POLA Cohort.

BACKGROUND: IDH-mutant anaplastic astrocytomas (AAs) are chemosensitive tumors for which the best choice of adjuvant chemotherapy between procarbazine, lomustine, and vincristine (PCV) or temozolomide (TMZ) after radiotherapy (RT) remains unclear. METHODS: In a large cohort of patients with histologically proven 2016 World Health Organization classification AA with IDH1/2 mutations included in the French national POLA cohort (n = 355), the primary objective was to compare progression-free survival (PFS) between the two treatment regimens (n = 311). Secondary endpoints were overall survival (OS), progression type, pseudoprogression rate, and toxicity. RESULTS: The 4-year PFS in the RT + PCV arm was 70.8% versus 53.5% in the RT + TMZ arm, with a hazard ratio (HR) of 0.58 (95% confidence interval [CI], 0.38-0.87; p = .0074) in univariable analysis and 0.63 (95% CI, 0.41-0.97; p = .0348) in multivariable analysis. The 4-year OS in the RT + PCV arm was 84.3% versus 76.6% in the RT + TMZ arm, with an HR of 0.57 (95% CI, 0.30-1.05; p = .0675) in univariable analysis. Toxicity was significantly higher in the RT + PCV arm with more grade ≥3 toxicity (46.7% vs. 8.6%, p < .0001). CONCLUSION: RT + PCV significantly improved PFS compared with RT + TMZ for IDH-mutant AA. However, RT + TMZ was better tolerated. IMPLICATIONS FOR PRACTICE: In the absence of fully conducted randomized trials comparing procarbazine, lomustine, and vincristine (PCV) with temozolomide (TMZ) in adjuvant treatment after radiotherapy (RT) for the management of IDH-mutant anaplastic astrocytoma (AA) and a similar level of evidence, these two chemotherapies are both equally recommended in international guidelines. This study in a national cohort of IDH-mutant AA defined according the 2016 World Health Organization (WHO) classification shows for the first time that the RT + PCV regimen significantly improves progression-free survival in comparison with the RT + TMZ regimen. Even if at the time of analysis the difference in overall survival was not significant, this result provides new evidence for the debate about the chemotherapy regimen to prescribe in adjuvant treatment to RT for WHO 2016 IDH-mutant AA.

TEMOBIC: Phase II Trial of Neoadjuvant Chemotherapy for Unresectable Anaplastic Gliomas: An ANOCEF Study.

LESSONS LEARNED: Treatment with temozolomide and BCNU was associated with substantial response and survival rates for patients with unresectable anaplastic glioma, suggesting potential therapeutic alternative for these patients. The optimal treatment for unresectable large anaplastic gliomas remains debated. BACKGROUND: The optimal treatment for unresectable large anaplastic gliomas remains debated. METHODS: Adult patients with histologically proven unresectable anaplastic oligodendroglioma or mixed gliomas (World Health Organization [WHO] 2007) were eligible. Treatment consisted of BCNU (150 mg/m2 ) and temozolomide (110 mg/m2 for 5 days) every 6 weeks for six cycles before radiotherapy. RESULTS: Between December 2005 and December 2009, 55 patients (median age of 53.1 years; range, 20.5-70.2) were included. Forty percent of patients presented with wild-type IDH1 gliomas, and 30% presented with methylated MGMT promoter. Median progression-free survival (PFS), centralized PFS, and overall survival (OS) were 16.6 (95% confidence interval [CI], 12.8-20.3), 15.4 (95% CI, 10.0-20.8), and 25.4 (95% CI, 17.5-33.2) months, respectively. Complete and partial responses under chemotherapy were observed for 28.3% and 17% of patients, respectively. Radiotherapy completion was achieved for 75% of patients. Preservation of functional status and self-care capability (Karnofsky performance status [KPS] ≥70) were preserved until disease progression for 69% of patients. Grade ≥ 3 toxicities were reported for 52% of patients, and three deaths were related to treatment. By multivariate analyses including age and KPS, IDH mutation was associated with better prognostic for both PFS and OS, whereas MGMT promoter methylation was associated with better OS. CONCLUSION: The association of BCNU and temozolomide upfront is active for patients with unresectable anaplastic gliomas, but toxicity limits its use.

Characterization of the ability of a, second-generation SST-DA chimeric molecule, TBR-065, to suppress GH secretion from human GH-secreting adenoma cells.

CONTEXT: Somatostatin (SST) and dopamine (DA) inhibit growth hormone (GH) secretion and proliferation of GH-secreting pituitary adenomas (GHomas) through binding to SSTR2 and D2R receptors. Chimeric SST-DA compounds (Dopastatins) display increased potency in inhibiting GH secretion, as compared with individual SST or DA analogs (alone or combined). OBJECTIVE: To assess the efficacy of a second-generation dopastatin, TBR-065, in suppressing GH secretion from human GH- and GH/prolactin(PRL)-omas. DESIGN: We compared the ability of TBR-065 to inhibit GH secretion from primary cultures of human GH- or GH/PRLoma cells to that of the first generation dopastatin, TBR-760 (formerly BIM-23A760), octreotide (OCT) and cabergoline (CAB), the later either alone or combined. We investigated whether there was any impact of BIM-133, the metabolite of TBR-065, on the ability of TBR-065 to inhibit GH in these cultures. METHODS: 17 GH- and GH/PRLomas were included in this study. Inhibition of GH secretion by TBR-065, TBR-760, OCT and CAB (0.1 pM to 0.1 µM) was assessed over a period of 8 h. RESULTS: All tumors expressed SSTR2 and D2R mRNAs. GH suppression was higher with TBR-065 as compared with TBR-760 (Emax = 57 ± 5.6% vs. 41.1 ± 12.5%, respectively, p < 0.001) or with OCT + CAB (Emax = 56.8 ± 7.2% vs. 44.4 ± 9.4%, p < 0.001). BIM-133 did not have any impact on the activity of TBR-065. CONCLUSION: TBR-065 has significantly improved efficacy in suppressing GH secretion as compared to current available therapies and may represent a new promising option for the treatment of acromegaly.

Somatotroph Tumors and the Epigenetic Status of the GNAS Locus.

Forty percent of somatotroph tumors harbor recurrent activating GNAS mutations, historically called the gsp oncogene. In gsp-negative somatotroph tumors, GNAS expression itself is highly variable; those with GNAS overexpression most resemble phenotypically those carrying the gsp oncogene. GNAS is monoallelically expressed in the normal pituitary due to methylation-based imprinting. We hypothesize that changes in GNAS imprinting of gsp-negative tumors affect GNAS expression levels and tumorigenesis. We characterized the GNAS locus in two independent somatotroph tumor cohorts: one of 23 tumors previously published (PMID: 31883967) and classified by pan-genomic analysis, and a second with 82 tumors. Multi-omics analysis of the first cohort identified a significant difference between gsp-negative and gsp-positive tumors in the methylation index at the known differentially methylated region (DMR) of the GNAS A/B transcript promoter, which was confirmed in the larger series of 82 tumors. GNAS allelic expression was analyzed using a polymorphic Fok1 cleavage site in 32 heterozygous gsp-negative tumors. GNAS expression was significantly reduced in the 14 tumors with relaxed GNAS imprinting and biallelic expression, compared to 18 tumors with monoallelic expression. Tumors with relaxed GNAS imprinting showed significantly lower SSTR2 and AIP expression levels. Altered A/B DMR methylation was found exclusively in gsp-negative somatotroph tumors. 43% of gsp-negative tumors showed GNAS imprinting relaxation, which correlated with lower GNAS, SSTR2 and AIP expression, indicating lower sensitivity to somatostatin analogues and potentially aggressive behavior.