Genetic Alterations in Gliosarcoma and Giant Cell Glioblastoma

Molecular characterization of gliosarcoma reveals prognostic biomarkers and clinical parallels with glioblastoma

PURPOSE

Gliosarcoma is a rare histopathological variant of glioblastoma, but it is unclear whether distinct clinical or molecular features distinguish it from other glioblastomas. The purpose of this study was to characterize common genomic alterations of gliosarcoma, compare them to that of glioblastoma, and correlate them with prognosis.

METHODS

This was a single-institution, retrospective cohort study of patients seen between 11/1/2017 to 1/28/2024. Clinical and genomic data were obtained from the medical record. Results were validated using data from AACR Project GENIE (v15.1-public).

RESULTS

We identified 87 gliosarcoma patients in the institutional cohort. Compared to a contemporary cohort of 492 glioblastoma, there was no difference in overall survival, though progression free survival was inferior for patients with gliosarcoma (p = 0.01). Several of the most-commonly altered genes in gliosarcoma were more frequently altered than in glioblastoma (NF1, PTEN, TP53), while others were less frequently altered than in glioblastoma (EGFR). CDKN2A/CDKN2B/MTAP alterations were associated with inferior survival on univariate Cox (HR = 5.4, p = 0.023). When pooled with 93 patients from the GENIE cohort, CDKN2A/B (HR = 1.75, p = 0.039), RB1 (HR = 0.51, p = 0.016), LRP1B (p = 0.050, HR = 2.0), and TSC2 (HR = 0.31, p = 0.048) alterations or loss were significantly associated with survival. These effects remained when controlled for age, sex, and cohort of origin with multivariate Cox.

CONCLUSION

Gliosarcoma has a similar overall survival but worse response to treatment and different mutational profile than glioblastoma. CDKN2A/B loss and LRP1B alterations were associated with inferior prognosis, while RB1 or TSC2 alterations were associated with improved outcomes. These findings may have implications for clinical management and therapeutic selection in this patient population.

Gliosarcoma: A Multi-Institutional Analysis on Clinical Outcomes and Prognostic Factors

PURPOSE

This study describes oncological outcomes and investigates prognostic factors for patients with gliosarcomas (GSM).

METHODS

Histopathologically confirmed GSM patients who underwent treatment at five European institutions were retrospectively analyzed.

RESULTS

We analyzed 170 patients with a median clinical follow-up time of 9.2 months. The majority received surgery (94.1%), postoperative radiotherapy (pRT, 81.8%), and temozolomide (TMZ)-based postoperative chemotherapy (66.5%). The median overall survival (OS) and progression-free survival (PFS) were 12.3 and 6.6 months, respectively. In the multivariable Cox regression analysis (MVA), the following factors were significantly associated with OS: age per year (hazard ratio (HR): 1.03, p < 0.001), subtotal resection (STR) versus biopsy only (HR: 0.15, p = 0.018), gross total resection (GTR) versus biopsy only (HR: 0.13, p = 0.011), pRT versus no pRT (HR: 0.20, p < 0.001), postoperative TMZ-based chemotherapy versus no postoperative chemotherapy (HR: 0.44, p = 0.003), MGMT promoter non-methylated versus methylated (HR: 1.79, p = 0.05), and tumor diameter per cm (HR: 1.15, p = 0.046). For PFS, the following factors were significantly associated in the MVA: GTR versus biopsy only (HR: 0.19, p = 0.026), pRT versus no pRT (HR: 0.36, p = 0.006), postoperative TMZ-based chemotherapy vs. no postoperative chemotherapy (HR: 0.39, p < 0.001), MGMT promoter status unknown versus methylated (HR: 1.69, p = 0.034), and tumor diameter per cm (HR: 1.18, p = 0.016). Sex, primary or secondary GSM, and TP53 mutational status were not significantly associated with OS or PFS.

CONCLUSIONS

Trimodal therapy comprising surgical resection, pRT and TMZ-based chemotherapy appears to have the most beneficial effect on survival in GSM patients. Smaller tumor size, younger age and methylated MGMT promoters are associated with improved survival. To our knowledge, this is the largest multi-institutional cohort study investigating outcomes and prognostic factors for GSM.

Giant cell glioblastoma with lipogenic differentiation in a patient with neurofibromatosis type 1: A case report

A 45-year-old woman with neurofibromatosis type 1 (NF1) developed a tumor in the left frontal lobe that showed features of giant cell glioblastoma (GC-GB). In addition to the typical GC-GB features, the tumor showed lipogenic differentiation, with many atypical lipoblasts and mature adipocytes. Tumor cells, including the lipogenic cells, were immunoreactive for GFAP, S-100 protein, ATRX, and p53. They were negative for IDH1-R132H, BRAF V600E, synaptophysin, NeuN, p16, mismatch repair proteins, and CD34. The patient is free from recurrence at approximately two years postoperatively. This is the fifth reported case of NF1-associated GC-GB (the second adult case). NF1 gene mutation might have played a role in the pathogenesis of lipogenic differentiation of GC-GB. The differential diagnosis of lipidized GC-GB from gliosarcoma or anaplastic pleomorphic xanthoastrocytoma is briefly discussed.

Primary and secondary gliosarcoma: differences in treatment and outcome

INTRODUCTION

There are only few studies comparing differences in the outcome of primary versus secondary gliosarcoma. This study aimed to review the outcome and survival of patients with primary or secondary gliosarcoma following surgical resection and adjuvant treatment. The data were also matched with data of patients with primary and secondary glioblastoma (GBM).

PATIENTS AND METHODS

Treatment histories of 10 patients with primary gliosarcoma and 10 patients with secondary gliosarcoma were analysed and compared. Additionally, data of 20 patients with primary and 20 patients with secondary GBM were analysed and compared. All patients underwent surgical resection of the tumour in our department. Follow-up data, progression-free survival (PFS), and median overall survival (mOS) were evaluated.

RESULTS

The median PFS in patients with primary gliosarcoma was significantly higher than in patients with secondary gliosarcoma (p = 0.037). The 6-month PFS rates were 80.0% in patients with primary and 30.0% in patients with secondary gliosarcoma. Upon recurrence, five patients with primary gliosarcoma and four patients with secondary gliosarcoma underwent repeat surgical resection. The mOS of patients with primary gliosarcoma was significantly higher than that of patients with secondary gliosarcoma (p = 0.031). The percentage of patients surviving at 1-year/2-year follow-up in primary gliosarcoma was 70%/20%, while it was only 10%/10% in secondary gliosarcoma. When PFS and mOS of primary gliosarcoma was compared to primary GBM, there were no statistically differences (p = 0.509; p = 0.435). The PFS and mOS of secondary gliosarcoma and secondary GBM were also comparable (p = 0.290 and p = 0.390).

CONCLUSION

Patients with primary gliosarcoma have a higher PFS and mOS compared to those with secondary gliosarcoma. In the case of tumour recurrence, patients with secondary gliosarcoma harbour an unfavourable prognosis with limited further options. The outcome of patients with primary or secondary gliosarcoma is comparable to that of patients with primary or secondary GBM.

TGF-β and BMP signaling are associated with the transformation of glioblastoma to gliosarcoma and then osteosarcoma

Background

Gliosarcoma, an isocitrate dehydrogenase wildtype (IDH-WT) variant of glioblastoma, is defined by clonal biphasic differentiation into gliomatous and sarcomatous components. While the transformation from a glioblastoma to gliosarcoma is uncommon, the subsequent transformation to osteosarcoma is rare but may provide additional insights into the biology of these typically distinct cancers. We observed a patient initially diagnosed with glioblastoma, that differentiated into gliosarcoma at recurrence, and further evolved to osteosarcoma at the second relapse. Our objective was to characterize the molecular mechanisms of tumor progression associated with this phenotypic transformation.

Methods

Tumor samples were collected at all 3 stages of disease and RNA sequencing was performed to capture their transcriptomic profiles. Sequential clonal evolution was confirmed by the maintenance of an identical PTEN mutation throughout the tumor differentiation using the TSO500 gene panel. Publicly available datasets and the Nanostring nCounter technology were used to validate the results.

Results

The glioblastoma tumor from this patient possessed mixed features of all 3 TCGA-defined transcriptomic subtypes of an IDH-WT glioblastoma and a proportion of osteosarcoma signatures were upregulated in the original tumor. Analysis showed that enhanced transforming growth factor-β (TGF-β) and bone morphogenic protein signaling was associated with tumor transformation. Regulatory network analysis revealed that TGF-β family signaling committed the lineage tumor to osteogenesis by stimulating the expression of runt-related transcription factor 2 (RUNX2), a master regulator of bone formation.

Conclusions

This unusual clinical case provided an opportunity to explore the modulators of longitudinal sarcomatous transformation, potentially uncovering markers indicating predisposition to this change and identification of novel therapeutic targets.

Primary Intracranial Gliosarcoma: Is It Really a Variant of Glioblastoma? An Update of the Clinical, Radiological, and Biomolecular Characteristics

Gliosarcomas (GS) are sporadic malignant tumors classified as a Glioblastoma (GBM) variant with IDH-wild type phenotype. It appears as a well-circumscribed lesion with a biphasic, glial, and metaplastic mesenchymal component. The current knowledge about GS comes from the limited literature. Furthermore, recent studies describe peculiar characteristics of GS, such as hypothesizing that it could be a clinical-pathological entity different from GBM. Here, we review radiological, biomolecular, and clinical data to describe the peculiar characteristics of PGS, treatment options, and outcomes in light of the most recent literature. A comprehensive literature review of PubMed and Web of Science databases was conducted for articles written in English focused on gliosarcoma until 2023. We include relevant data from a few case series and only a single meta-analysis. Recent evidence describes peculiar characteristics of PGS, suggesting that it might be a specific clinical-pathological entity different from GBM. This review facilitates our understanding of this rare malignant brain tumor. However, in the future we recommend multi-center studies and large-scale metanalyses to clarify the biomolecular pathways of PGS to develop new specific therapeutic protocols, different from conventional GBM therapy in light of the new therapeutic opportunities.

Standardizing analysis of intra-tumoral heterogeneity with computational pathology

Many malignant cancers like glioblastoma are highly adaptive diseases that dynamically change their regional biology to survive and thrive under diverse microenvironmental and therapeutic pressures. While the concept of intra-tumoral heterogeneity has become a major paradigm in cancer research and care, systematic approaches to assess and document bio-variation in cancer are still in their infancy. Here we discuss existing approaches and challenges to documenting intra-tumoral heterogeneity and emerging computational approaches that leverage artificial intelligence to begin to overcome these limitations. We propose how these emerging techniques can be coupled with a diversity of molecular tools to address intra-tumoral heterogeneity more systematically in research and in practice, especially across larger specimens and longitudinal analyses. Systematic documentation and characterization of heterogeneity across entire tumor specimens and their longitudinal evolution has the potential to improve our understanding and treatment of cancer.

Gliosarcoma with extensive extracranial metastatic spread and familial coincidence: A case report

Gliosarcoma is a rare histopathological subtype of glioblastoma. Metastatic spreading is unusual. In this report, we illustrate a case of gliosarcoma with extensive extracranial metastases with confirmation of histological and molecular concordance between the primary tumor and a metastatic lesion of the lung. Only the autopsy revealed the extent of metastatic spread and the hematogenous pattern of metastatic dissemination. Moreover, the case bared a familial coincidence of malignant glial tumors as the patient's son was diagnosed with a high-grade glioma shortly after the patient's death. By molecular analysis (Sanger and next generation panel sequencing), we could confirm that both patient's tumors carried mutations in the TP53 gene. Interestingly, the detected mutations were located in different exons. Altogether, this case draws attention to the fact that sudden clinical aggravation could be caused by the rare phenomenon of metastatic spread and should therefore be always taken into consideration, even at an early disease stage. Furthermore, the presented case highlights the contemporary value of autoptic pathological examination.

Prognostic Factors of Gliosarcoma in the Real World: A Retrospective Cohort Study

Purpose

Gliosarcoma is a histopathological variant of glioblastoma, which is characterized by a biphasic growth pattern consisting of glial and sarcoma components. Owing to its scarcity, data regarding the impact of available treatments on the clinical outcomes of gliosarcoma are inadequate. The purpose of this retrospective cohort study was to analyze the prognostic factors of gliosarcoma.

Methods

By screening the clinical database of neurosurgical cases at a single center, patients with gliosarcoma diagnosed histologically from 2013 to 2021 were identified. Clinical, pathological, and molecular data were gathered founded on medical records and follow-up interviews. Prognostic factors were derived using the Cox proportional hazards model with backward stepwise regression analysis.

Results

Forty-five GSM patients were included. Median overall survival was 25.6 months (95% CI 8.0-43.1), and median relapse-free survival was 15.2 months (95% CI 9.7-20.8). In multivariable analysis, total resection (p = 0.023, HR = 0.192, 95% CI 0.046-0.797) indicated an improved prognosis. And low expression of Ki-67 (p = 0.059, HR = 2.803, 95% CI 0.963-8.162) would be likely to show statistical significance. However, there might be no statistically significant survival benefit from radiotherapy with concurrent temozolomide (n = 33, 73.3%, log-rank p = 0.99) or adjuvant temozolomide (n = 32, 71.1%, log-rank p = 0.74).

Conclusion

This single-center retrospective study with a limited cohort size has demonstrated the treatment of gross total resection and low expression of Ki-67 which are beneficial for patients with GSM, while radiotherapy or temozolomide is not.

Morphogenetic and Imaging Characteristics in Giant Cell Glioblastoma

Giant cell glioblastoma is a rare tumor entity of IDH-wildtype glioblastoma. It is usually found in the pediatric population. We describe a particular case of a female patient diagnosed histopathologically with giant cell glioblastoma, who had two recurrences in different lobes of the same cerebral hemisphere, despite positive prognostic factors and appropriate treatment. We performed an immunohistochemical characterization of giant cell glioblastoma as well as an analysis of its aggressiveness using the cytogenetic markers TP53, CDKN2A, and TP73 using the FISH technique. The clinical picture was inconsistant, the suspicion being completely different initially. Paraclinical examination and imaging initially suggested a metastasis to the insular lobe. After surgery, histopathological and immunohistochemical examinations were the basis for the diagnosis. Despite the prognostic factors known so far in the literature, the aggressiveness denoted by multiple relapses and morphogenetic tests particularizes the case and improves the literature by bringing new information about this rare neoplasm of the central nervous system.

Gliosarcoma: The Distinct Genomic Alterations Identified by Comprehensive Analysis of Copy Number Variations

Gliosarcoma (GSM), a histologic variant of glioblastoma (GBM), carries a poor prognosis with less than one year of median survival. Though GSM is similar with GBM in most clinical and pathological symptoms, GBM has unique molecular and histological features. However, as the rarity of GSM samples, the genetic information of this tumor is still lacking. Here, we take a comprehensive analysis of DNA copy number variations (CNV) in GBM and GSM. Whole genome sequencing was performed on 21 cases of GBM and 15 cases of GSM. CNVKIT is used for CNV calling. Our data showed that chromosomes 7, 8, 9, and 10 were the regions where CNV frequently happened in both GBM and GSM. There was a distinct CNV signal in chromosome 2 especially in GSM. The pathway enrichment of genes with CNV was suggested that the GBM and GSM shared the similar mechanism of tumor development. However, the CNV of some screened genes displayed a disparate form between GBM and GSM, such as AMP, BEND2, HDAC6, FOXP3, ZBTB33, TFE3, and VEGFD. It meant that GSM was a distinct subgroup possessing typical biomarkers. The pathways and copy number alterations detected in this study may represent key drivers in gliosarcoma oncogenesis and may provide a starting point toward targeted oncologic analysis with therapeutic potential.

Pediatric Giant Cell Glioblastoma Presenting with Intracranial Dissemination at Diagnosis: A Case Report

Giant cell glioblastoma (GCG) is a rare subtype of glioblastoma multiforme (GBM), and it often occurs in younger patients; however, its onset in children is extremely noticeable. A 7-year-old girl presented with a headache and restlessness. A giant tumor that was 7 cm in diameter was found by magnetic resonance imaging (MRI) in the left frontal lobe with intracranial dissemination. Because the tumor had extended to the lateral ventricles and occluded the foramen of Monro causing hydrocephalus, she underwent ventricular drainage and neuro-endoscopic biopsy from the left posterior horn of the lateral ventricle. The initial pathological diagnosis was an atypical teratoid/rhabdoid tumor (AT/RT). When the dissemination subsided after the first chemotherapy with vincristine, doxorubicin, and cyclophosphamide, she underwent the first tumor resection via a left frontal transcortical approach. After surgery, the second chemotherapy with ifosfamide, cisplatin, and etoposide was not effective for the residual tumor and intracranial dissemination. The second surgery via a transcallosal approach achieved nearly total resection leading to an improvement of the hydrocephalus. The definitive pathological diagnosis was GCG. Despite chemo-radiation therapy, the dissemination in the basal cistern reappeared and the hydrocephalus worsened. She was obliged to receive a ventriculo-peritoneal (VP) shunt and palliative care at home; however, her poor condition prevented her discharge. Ten months after admission, she died of tumor progression. The peritoneal dissemination was demonstrated by cytology of ascites. In conclusion, although unusual, pediatric GCG may be disseminated at diagnosis, in which case both tumor and hydrocephalus control need to be considered.

IDH-wild type glioblastomas featuring at least 30% giant cells are characterized by frequent RB1 and NF1 alterations and hypermutation

Giant cell glioblastoma (GC-GBM) is a rare variant of IDH-wt GBM histologically characterized by the presence of numerous multinucleated giant cells and molecularly considered a hybrid between IDH-wt and IDH-mutant GBM. The lack of an objective definition, specifying the percentage of giant cells required for this diagnosis, may account for the absence of a definite molecular profile of this variant. This study aimed to clarify the molecular landscape of GC-GBM, exploring the mutations and copy number variations of 458 cancer-related genes, tumor mutational burden (TMB), and microsatellite instability (MSI) in 39 GBMs dichotomized into having 30-49% (15 cases) or ≥ 50% (24 cases) GCs. The type and prevalence of the genetic alterations in this series was not associated with the GCs content (< 50% or ≥ 50%). Most cases (82% and 51.2%) had impairment in TP53/MDM2 and PTEN/PI3K pathways, but a high proportion also featured TERT promoter mutations (61.5%) and RB1 (25.6%) or NF1 (25.6%) alterations. EGFR amplification was detected in 18% cases in association with a shorter overall survival (P = 0.004). Sixteen (41%) cases had a TMB > 10 mut/Mb, including two (5%) that harbored MSI and one with a POLE mutation. The frequency of RB1 and NF1 alterations and TMB counts were significantly higher compared to 567 IDH wild type (P < 0.0001; P = 0.0003; P < 0.0001) and 26 IDH-mutant (P < 0.0001; P = 0.0227; P < 0.0001) GBMs in the TCGA PanCancer Atlas cohort. These findings demonstrate that the molecular landscape of GBMs with at least 30% giant cells is dominated by the impairment of TP53/MDM2 and PTEN/PI3K pathways, and additionally characterized by frequent RB1 alterations and hypermutation and by EGFR amplification in more aggressive cases. The high frequency of hypermutated cases suggests that GC-GBMs might be candidates for immune check-point inhibitors clinical trials.

SMARCAL1 loss and alternative lengthening of telomeres (ALT) are enriched in giant cell glioblastoma

Subsets of high-grade gliomas, including glioblastoma (GBM), are known to utilize the alternative lengthening of telomeres (ALT) pathway for telomere length maintenance. However, the telomere maintenance profile of one subtype of GBM-giant cell GBM-has not been extensively studied. Here, we investigated the prevalence of ALT, as well as ATRX and SMARCAL1 protein loss, in a cohort of classic giant cell GBM and GBM with giant cell features. To determine the presence of ALT, a telomere-specific fluorescence in situ hybridization assay was performed on 15 cases of classic giant cell GBM, 28 additional GBMs found to have giant cell features, and 1 anaplastic astrocytoma with giant cell features. ATRX, SMARCAL1, and IDH1 protein status were assessed in a proportion of cases by immunohistochemistry and were compared to clinical-pathologic and molecular characteristics. In the overall cohort of 44 cases, 19 (43%) showed evidence of ALT. Intriguingly, of the ALT-positive cases, only 9 (47.4%) displayed loss of the ALT suppressor ATRX by immunohistochemistry. Since inactivating mutations in SMARCAL1 have been identified in ATRX wild-type ALT-positive gliomas, we developed an immunohistochemistry assay for SMARCAL1 protein expression using genetically validated controls. Of the 19 ALT-positive cases, 6 (31.5%) showed loss or mis-localization of SMARCAL1 by immunohistochemistry. Of these cases, four retained ATRX protein expression, while two cases also displayed ATRX loss. Additionally, we assessed five cases from which multiple temporal samples were available and ALT status was concordant between both tumor biopsies. In summary, we have identified a subset of giant cell GBM that utilize the ALT telomere maintenance mechanism. Importantly, in addition to ATRX loss, ALT-positive tumors harboring SMARCAL1 alterations are prevalent in giant cell GBM.

Nuclear receptor NR5A2 negatively regulates cell proliferation and tumor growth in nervous system malignancies

Nervous system malignancies are characterized by rapid progression and poor survival rates. These clinical observations underscore the need for novel therapeutic insights and pharmacological targets. To this end, here, we identify the orphan nuclear receptor NR5A2/LRH1 as a negative regulator of cancer cell proliferation and promising pharmacological target for nervous system-related tumors. In particular, clinical data from publicly available databases suggest that high expression levels of NR5A2 are associated with favorable prognosis in patients with glioblastoma and neuroblastoma tumors. Consistently, we experimentally show that NR5A2 is sufficient to strongly suppress proliferation of both human and mouse glioblastoma and neuroblastoma cells without inducing apoptosis. Moreover, short hairpin RNA-mediated knockdown of the basal expression levels of NR5A2 in glioblastoma cells promotes their cell cycle progression. The antiproliferative effect of NR5A2 is mediated by the transcriptional induction of negative regulators of the cell cycle, CDKN1A (encoding for p21cip1), CDKN1B (encoding for p27kip1) and Prox1 Interestingly, two well-established agonists of NR5A2, dilauroyl phosphatidylcholine (DLPC) and diundecanoyl phosphatidylcholine, are able to mimic the antiproliferative action of NR5A2 in human glioblastoma cells via the induction of the same critical genes. Most importantly, treatment with DLPC inhibits glioblastoma tumor growth in vivo in heterotopic and orthotopic xenograft mouse models. These data indicate a tumor suppressor role of NR5A2 in the nervous system and render this nuclear receptor a potential pharmacological target for the treatment of nervous tissue-related tumors.

Do gliosarcomas have distinct imaging features on routine MRI?

PURPOSE

The aim of this study was the development and external validation of a logistic regression model to differentiate gliosarcoma (GSC) and glioblastoma multiforme (GBM) on standard MR imaging.

METHODS

A univariate and multivariate analysis was carried out of a logistic regression model to discriminate patients histologically diagnosed with primary GSC and an age and sex-matched group of patients with primary GBM on presurgical MRI with external validation.

RESULTS

In total, 56 patients with GSC and 56 patients with GBM were included. Evidence of haemorrhage suggested the diagnosis of GSC, whereas cystic components and pial as well as ependymal invasion were more commonly observed in GBM patients. The logistic regression model yielded a mean area under the curve (AUC) of 0.919 on the training dataset and of 0.746 on the validation dataset. The accuracy in the validation dataset was 0.67 with a sensitivity of 0.85 and a specificity of 0.5.

CONCLUSIONS

Although some imaging criteria suggest the diagnosis of GSC or GBM, differentiation between these two tumour entities on standard MRI alone is not feasible.

TERT Promoter Alterations in Glioblastoma: A Systematic Review

Simple Summary

Glioblastoma is the most common malignant primary brain tumor in adults. Glioblastoma accounts for 2 to 3 cases per 100,000 persons in North America and Europe. Glioblastoma classification is now based on histopathological and molecular features including isocitrate dehydrogenase (IDH) mutations. At the end of the 2000s, genome-wide sequencing of glioblastoma identified recurrent somatic genetic alterations involved in oncogenesis. Among them, the alterations in the promoter region of the telomerase reverse transcriptase (TERTp) gene are highly recurrent and occur in 70% to 80% of all glioblastomas, including glioblastoma IDH wild type and glioblastoma IDH mutated. This review focuses on recent advances related to physiopathological mechanisms, diagnosis, and clinical implications.

Abstract

Glioblastoma, the most frequent and aggressive primary malignant tumor, often presents with alterations in the telomerase reverse transcriptase promoter. Telomerase is responsible for the maintenance of telomere length to avoid cell death. Telomere lengthening is required for cancer cell survival and has led to the investigation of telomerase activity as a potential mechanism that enables cancer growth. The aim of this systematic review is to provide an overview of the available data concerning TERT alterations and glioblastoma in terms of incidence, physiopathological understanding, and potential therapeutic implications.

IDH1-mutant primary intraventricular gliosarcoma: Case report and systematic review of a rare location and molecular profile

Background:

Gliosarcoma (GS) is classified as an IDH-wild-type variant of glioblastoma (GBM). While GS is already an unusual presentation of GBM, IDH1-mutant cases are especially rare. We present an IDH1-mutant primary intraventricular GS case report and a systematic review of the molecular profile in GS correlating to the prognostic and pathogenesis of IDH1/2 mutations.

Case Description:

A 44-years-old man presented with ongoing fatigue symptoms and a new-onset intense occipital headache. The patient complained of memory loss, dyscalculia, and concentration difficulties. An MRI revealed a bihemispheric intraventricular mass crossing the midline through the corpus callosum and infiltrating the trigone of the lateral ventricles, hypointense, and hyperintense on the T1- and T2-weighted image. We performed a microsurgical resection with a transparietal transsulcal approach; however, the contralateral mass was attached to vascular structures and we decided to reoperate the patient in another moment. The histopathological study showed a Grade IV tumor and the immunohistochemistry confirmed the diagnosis of GS. The patient presented progressive neurologic decline and died 45 days after the surgical approach.

Conclusion:

We did two systematic reviews studies from PubMed, EMBASE, MEDLINE, Cochrane, and SCOPUS databases, and included molecular and intraventricular studies of GS. We performed further meta-analysis using OpenMetaAnalyst™ software. We conducted a forest plot with the molecular profile of GS. When correlated IDH1 mutation versus tp53 mutation, we found an odds ratio (OR) of 0.018 (0.005–0.064) and P < 0.001. Moreover, we compared IDH1 mutation versus MGMT methylation (P = 0.006; OR = 0.138 [0.034–0.562]). The studies evaluating the molecular profile in GS prognostics are often extended from all GBMs despite specifics GBM variants (i.e., GS). We found a correlation between IDH1 mutation expression with tp53 and MGMT expression in GS, and future studies exploring this molecular profile in GS are strongly encouraged.

Demographic, radiographic, molecular and clinical characteristics of primary gliosarcoma and differences to glioblastoma

OBJECTIVE

Gliosarcoma (GSC) is a rare histological variant of glioblastoma (GBM). Due to limited evidence regarding clinical, genetic and radiographic characteristics of GSC, this study aimed to analyze independent outcome predictors of GSC, and to address the differences between GSC and GBM concerning the baseline characteristics and patients' survival.

METHODS

Patients treated between 2001 and 2018 for the diagnosis of GBM and GSC were included in this study. Patients' records were reviewed for demographic, clinical, genetic and radiographic characteristics. Univariate, multivariate and propensity score matched analyses were performed.

RESULTS

In the GSC sub-cohort (N = 56), patients' age, preoperative clinical status, midline tumor location and tumor size were found to be independently associated with overall survival. As compared to GBM individuals (N = 1249), a temporal location (p = 0.002), presence of eccentric tumor cysts (p < 0.001), a higher ratio of TP53 staining (p = 0.002) and a lower ratio of GFAP staining (p = 0.005) were characteristic for GSC. The diagnosis of GSC was associated with a poorer survival (p = 0.002) independently of the patients' age, sex, clinical status and extent of resection, However, this association was no more significant, when enhancing the multivariate analysis with molecular-genetic characteristics (IDH1 mutation and MGMT promotor methylation status).

DISCUSSION

Certain radiographic and molecular-genetic patterns present the distinct characteristics of GSC. There is an association between the diagnosis of GSC and a poorer outcome. This difference might be linked to different genetic alterations in GBM and GSC. Prospective studies are needed to further elucidate the characteristics of GSC and develop targeted treatment approaches for this rare variant.

Molecular Features and Prognostic Factors of Pleomorphic Xanthoastrocytoma: A Collaborative Investigation of the Tohoku Brain Tumor Study Group

Pleomorphic xanthoastrocytoma (PXA) is a rare glial tumor, however, its histological differentiation from high-grade gliomas is often difficult. Molecular characteristics may contribute to a better diagnostic discrimination. Prognostic factors of PXA are also important but few relevant reports have been published. This study investigated the molecular features and prognostic factors of PXAs. Seven university hospitals participated in this study by providing retrospective clinical data and tumor samples of PXA cases between 1993 and 2014. Tumor samples were analyzed for immunohistochemical (IHC) neuronal and glial markers along with Ki67. The status of the BRAF and TERT promoter (TERTp) mutation was also evaluated using the same samples, followed by feature extraction of PXA and survival analyses. In all, 19 primary cases (17 PXA and 2 anaplastic PXA) were included. IHC examination revealed the stable staining of nestin and the close association of synaptophysin to NFP. Of the PXA cases, 57% had the BRAF mutation and only 7% had the TERTp mutation. On univariate analysis, age (≥60 years), preoperative Karnofsky performance status (KPS) (≤80%), and marked peritumoral edema were significantly associated with progression-free survival (PFS). No independent factor was indicated by the multivariate analysis. In conclusion, PXA was characterized by positive nestin staining and a few TERTp mutations. The neuronal differential marker and BRAF status may help in diagnosis. Patient age, preoperative KPS, and marked perifocal edema were associated with PFS. The present study is limited because of small number of cases and its retrospective nature. Further clinical study is needed.

Beyond IDH-Mutation: Emerging Molecular Diagnostic and Prognostic Features in Adult Diffuse Gliomas

Diffuse gliomas are among the most common adult central nervous system tumors with an annual incidence of more than 16,000 cases in the United States. Until very recently, the diagnosis of these tumors was based solely on morphologic features, however, with the publication of the WHO Classification of Tumours of the Central Nervous System, revised 4th edition in 2016, certain molecular features are now included in the official diagnostic and grading system. One of the most significant of these changes has been the division of adult astrocytomas into IDH-wildtype and IDH-mutant categories in addition to histologic grade as part of the main-line diagnosis, although a great deal of heterogeneity in the clinical outcome still remains to be explained within these categories. Since then, numerous groups have been working to identify additional biomarkers and prognostic factors in diffuse gliomas to help further stratify these tumors in hopes of producing a more complete grading system, as well as understanding the underlying biology that results in differing outcomes. The field of neuro-oncology is currently in the midst of a "molecular revolution" in which increasing emphasis is being placed on genetic and epigenetic features driving current diagnostic, prognostic, and predictive considerations. In this review, we focus on recent advances in adult diffuse glioma biomarkers and prognostic factors and summarize the state of the field.

Giants and monsters: Unexpected characters in the story of cancer recurrence

Polyploid giant cancer cells (PGCC) constitute a dangerous subpopulation of cancer cells and are a driving force in cancer recurrence. These unique cells arise from diploid tumor cells in response to stress encountered in the tumor microenvironment or during cancer therapy. PGCC are greatly dedifferentiated, acquire pluripotency, and are able to replicate through a form of asymmetric division called neosis, which results in new populations that are themselves able to differentiate into new cell types or to re-establish tumors. Progeny tend to be more genetically unstable than the founding population due to the dysregulation required to transition through a PGCC state. Therefore, cancers that escape stressors through this mechanism tend to re-emerge with a more aggressive phenotype that is therapy resistant. This review focuses on the clinical significance of PGCC, the need for standardized nomenclature and molecular markers, as well as possible avenues to develop therapies aimed at PGCC and the process of neosis. The biology underlying the development of PGCC including cell cycle checkpoint dysregulation, stress responses, dedifferentiation, stemness and epithelial-mesenchymal transition is discussed.

Advances in Diagnostic Immunohistochemistry for Primary Tumors of the Central Nervous System

As genomic characterization becomes increasingly necessary for accurate diagnosis of tumors of the central nervous system, identification of rapidly assessible biomarkers is equally important to avoid excessive cost and delay in initiation of therapy. This article reviews novel immunohistochemical markers that may be used to determine mutation status, activation of signaling pathways, druggable targets, and cell lineage in many diverse tumor types. In particular, recently added entities to the 2016 WHO classification of central nervous system tumors will be addressed, including IDH-mutant gliomas, diffuse midline glioma, epithelioid glioblastoma, angiocentric glioma, RELA-rearranged ependymoma, embryonal tumors (medulloblastoma, atypical teratoid/rhabdoid tumor, pineoblastoma, embryonal tumor with multilayered rosettes, and other genetically defined high-grade neuroepithelial tumors), and meningiomas associated with germline alterations.

TP53, ATRX alterations, and low tumor mutation load feature IDH-wildtype giant cell glioblastoma despite exceptional ultra-mutated tumors

Background

Giant cell glioblastoma (gcGBM) is a rare morphological variant of IDH-wildtype (IDHwt) GBM that occurs in young adults and have a slightly better prognosis than "classic" IDHwt GBM.

Methods

We studied 36 GBMs, 14 with a histopathological diagnosis of gcGBM and 22 with a giant cell component. We analyzed the genetic profile of the most frequently mutated genes in gliomas and assessed the tumor mutation load (TML) by gene-targeted next-generation sequencing. We validated our findings using The Cancer Genome Atlas (TCGA) data.

Results

p53 was altered by gene mutation or protein overexpression in all cases, while driver IDH1, IDH2, BRAF, or H3F3A mutations were infrequent or absent. Compared to IDHwt GBMs, gcGBMs had a significant higher frequency of TP53, ATRX, RB1, and NF1 mutations, while lower frequency of EGFR amplification, CDKN2A deletion, and TERT promoter mutation. Almost all tumors had low TML values. The high TML observed in only 2 tumors was consistent with POLE and MSH2 mutations. In the histopathological review of TCGA IDHwt, TP53-mutant tumors identified giant cells in 37% of the cases. Considering our series and that of the TCGA, patients with TP53-mutant gcGBMs had better overall survival than those with TP53wt GBMs (log-rank test, P < .002).

Conclusions

gcGBMs have molecular features that contrast to "classic" IDHwt GBMs: unusually frequent ATRX mutations and few EGFR amplifications and CDKN2A deletions, especially in tumors with a high number of giant cells. TML is frequently low, although exceptional high TML suggests a potential for immune checkpoint therapy in some cases, which may be relevant for personalized medicine.

Giant cell glioblastoma is a distinctive subtype of glioma characterized by vulnerability to DNA damage

Giant cell glioblastoma (GC-GBM) consists of large cells with pleomorphic nuclei. As a contrast to GC-GBM, we defined monotonous small GBM (MS-GBM) as GBM that consists of small cells with monotonous small nuclei, and compared the DNA damage as well as other pathological features. GC-GBM showed minimal invasion (< 2 mm) and focal sarcomatous areas. TERTp was wild type in GC-GBM but mutant in MS-GBM. OLIG2 expression was significantly higher in MS-GBM (P < 0.01) (77% in MS-GBM and 7% in GC-GBM). GC-GBM showed significantly higher DNA double-strand breaks (DSBs) compared with MS-GBM (P < 0.01) (76% in GC-GBM and 15% in MS-GBM). Nearly, all large cells in GC-GBM underwent DSBs. Thus, significant DSBs in GC-GBM might be induced by an innate lesser stemness characteristic and be followed by mitotic slippage, resulting in polyploidization and the large pleomorphic nuclei. We conclude that GC-GBM is a distinctive subtype of glioma characterized by its vulnerability to DNA damage and that wild-type TERTp and lower OLIG2 function might induce this feature. Notably, even large pleomorphic nuclei with severe DSBs demonstrated Ki67 positivity, which alerts pathologists to the interpretation of Ki67 positivity, because cells with large nuclei undergoing severe DSBs cannot be recognized as proliferating cells that contribute to tumor aggressiveness.

Clinical Characteristics of Gliosarcoma and Outcomes From Standardized Treatment Relative to Conventional Glioblastoma

Background: Gliosarcoma (GS) is a rare histopathologic variant of glioblastoma (GBM) characterized by a biphasic growth pattern consisting of both glial and sarcomatous components. Reports regarding its relative prognosis compared to conventional GBM are conflicting and although GS is treated as conventional GBM, supporting evidence is lacking. The aim of this study was to characterize demographic trends, clinical outcomes and prognostic variables of GS patients receiving standardized therapy and compare these to conventional GBM. Methods: Six hundred and eighty GBM patients, treated with maximal safe resection followed by radiotherapy with concomitant and adjuvant temozolomide at a single institution, were retrospectively reevaluated by reviewing histopathological records and tumor tissue for identification of GS patients. Clinico-pathological- and tumor growth characteristics were obtained via assessment of medical records and imaging analysis. Kaplan-Meier survival estimates were compared with log-rank testing, while Cox-regression modeling was tested for prognostic factors in GS patients. Results: The cohort included 26 primary gliosarcoma (PGS) patients (3.8%) and 7 secondary gliosarcoma (SGS) patients (1.0%). Compared to conventional GBM tumors, PGS tumors were significantly more often MGMT-unmethylated (73.9%) and located in the temporal lobe (57.7%). GS tumors often presented dural contact, while extracranial metastasis was only found in 1 patient. No significant differences were found between PGS and conventional GBM in progression-free-survival (6.8 and 7.6 months, respectively, p = 0.105) and in overall survival (13.4 and 15.7 months, respectively, p = 0.201). Survival following recurrence was not significantly different between PGS, SGS, and GBM. Temporal tumor location and MGMT status were found associated with PGS survival (p = 0.036 and p = 0.022, respectively). Conclusion: Despite histopathological and location difference between GS and GBM tumors, the patients present similar survival outcome from standardized treatment. These findings support continued practice of radiation and temozolomide for GS patients.

Whole-exome sequencing revealed mutational profiles of giant cell glioblastomas

Giant cell glioblastoma (gcGBM) is a rare histological variant of GBM, accounting for about 1% of all GBM. The prognosis is poor generally though gcGBM does slightly better than the other IDH-wild-type GBM. Because of the rarity of the cases, there has been no comprehensive molecular analysis of gcGBM. Previously, single-gene study identified genetic changes in TP53, PTEN and TERT promoter mutation in gcGBM. In this report, we performed whole-exome sequencing (WES) to identify somatically acquired mutations and copy number variations (CNVs) in 10 gcGBM genomes. We also examined TERT promoter mutation and MGMT methylation in our cohort. On top of the reported mutations, WES revealed ATRX, PIK3R1, RB1 and SETD2 as the recurrent mutations in gcGBM. Notably, one tumor harbored a mutation in MutS homolog 6 (MSH6) that is a key mismatch repair (MMR) gene. This tumor demonstrated hypermutation phenotype and showed an increased number of somatic mutations. TERT promoter mutation and MGMT methylation were observed in 20% and 40% of our samples, respectively. In conclusion, we described relevant mutation profiling for developing future targeted therapies in gcGBM.

Molecular Study of Long-Term Survivors of Glioblastoma by Gene-Targeted Next-Generation Sequencing

Glioblastoma (GBM) is the most common malignant adult primary brain tumor. Despite its high lethality, a small proportion of patients have a relatively long overall survival (OS). Here we report a study of a series of 74 GBM samples from 29 long-term survivors ([LTS] OS ≥36 months) and 45 non-LTS. Using next-generation sequencing, we analyzed genetic alterations in the genes most frequently altered in gliomas. Approximately 20% of LTS had a mutation in the IDH1 or IDH2 (IDH) genes, denoting the relevance of this molecular prognostic factor. A new molecular group of GBMs harbored alterations in ATRX or DAXX genes in the absence of driver IDH or H3F3A mutations. These patients tended to have a slightly better prognosis, to be younger at diagnosis, and to present frontal or temporal tumors, and, morphologically, to present giant tumor cells. A significant fraction of LTS GBM patients had tumors with 1 or more alterations in the relevant GBM signaling pathways (RTK/PI3K, TP53 and RB1). In these patients, the PDGFRA alteration is suggested to be a favorable molecular factor. Our findings here are relevant for developing future targeted therapies and for identifying molecular prognostic factors in GBM patients.

Ultra-Mutation in IDH Wild-Type Glioblastomas of Patients Younger than 55 Years is Associated with Defective Mismatch Repair, Microsatellite Instability, and Giant Cell Enrichment

Background: Glioblastomas (GBMs) are classified into isocitrate dehydrogenase (IDH) mutants and IDH wild-types (IDH-wt). This study aimed at identifying the mutational assets of IDH-wt GBMs in patients aged 18–54 years for which limited data are available. Methods: Sixteen IDH-wt GBMs from adults < 55 years old were explored for mutations, copy number variations, tumour mutational load (TML), and mutational spectrum by a 409 genes TML panel. Results: Eight (50%) IDH-wt GBMs were hypermutated (TML > 9 mutations/Mb) and two (12.5%) were ultra-mutated (TML > 100 mutations/Mb). One ultra-mutated GBM had microsatellite instability (MSI), a somatic MSH6 mutation, and a germline POLE mutation. The other ultra-mutated GBMs had MSI and two somatic mutations in MSH2. Both ultra-mutated GBMs featured at least 25% giant cells. The overall survival of eight patients with hypermutated GBMs was significantly longer than that of patients with non-hypermutated GBMs (p = 0.04). Conclusions: We identified a hyper-mutated subgroup among IDH-wt GBMs in adults < 55 years that had improved prognosis. Two cases were ultra-mutated and characterized by the presence of at least 25% giant cells, MMR mutations, and MSI. Since high TML has been associated with response to immune checkpoint inhibition in paediatric gliomas, the identification of a subtype of ultra-mutated IDH-wt GBM may have implications for immunotherapy.

High FREM2 Gene and Protein Expression Are Associated with Favorable Prognosis of IDH-WT Glioblastomas

World Health Organization grade IV diffuse gliomas, known as glioblastomas, are the most common malignant brain tumors, and they show poor prognosis. Multimodal treatment of surgery followed by radiation and chemotherapy is not sufficient to increase patient survival, which is 12 to 18 months after diagnosis. Despite extensive research, patient life expectancy has not significantly improved over the last decade. Previously, we identified FREM2 and SPRY1 as genes with differential expression in glioblastoma cell lines compared to nonmalignant astrocytes. In addition, the FREM2 and SPRY1 proteins show specific localization on the surface of glioblastoma cells. In this study, we explored the roles of the FREM2 and SPRY1 genes and their proteins in glioblastoma pathology using human tissue samples. We used proteomic, transcriptomic, and bioinformatics approaches to detect changes at different molecular levels. We demonstrate increased FREM2 protein expression levels in glioblastomas compared to reference samples. At the transcriptomic level, both FREM2 and SPRY1 show increased expression in tissue samples of different glioma grades compared to nonmalignant brain tissue. To broaden our experimental findings, we analyzed The Cancer Genome Atlas glioblastoma patient datasets. We discovered higher FREM2 and SPRY1 gene expression levels in glioblastomas compared to lower grade gliomas and reference samples. In addition, we observed that low FREM2 expression was associated with progression of IDH-mutant low-grade glioma patients. Multivariate analysis showed positive association between FREM2 and favorable prognosis of IDH-wild type glioblastoma. We conclude that FREM2 has an important role in malignant progression of glioblastoma, and we suggest deeper analysis to determine its involvement in glioblastoma pathology.

Gliosarcoma in a Young Filipino Woman: A Case Report and Review of the Literature

Patient: Female, 28

Final Diagnosis: Gliosarcoma

Symptoms: Foot drop

Medication: —

Clinical Procedure: —

Specialty: Neurosurgery

Gliosarcoma Is Driven by Alterations in PI3K/Akt, RAS/MAPK Pathways and Characterized by Collagen Gene Expression Signature

Gliosarcoma is a very rare brain tumor reported to be a variant of glioblastoma (GBM), IDH-wildtype. While differences in molecular and histological features between gliosarcoma and GBM were reported, detailed information on the genetic background of this tumor is lacking. We intend to fill in this knowledge gap by the complex analysis of somatic mutations, indels, copy number variations, translocations and gene expression patterns in gliosarcomas. Using next generation sequencing, we determined somatic mutations, copy number variations (CNVs) and translocations in 10 gliosarcomas. Six tumors have been further subjected to RNA sequencing analysis and gene expression patterns have been compared to those of GBMs. We demonstrate that gliosarcoma bears somatic alterations in gene coding for PI3K/Akt (PTEN, PI3K) and RAS/MAPK (NF1, BRAF) signaling pathways that are crucial for tumor growth. Interestingly, the frequency of PTEN alterations in gliosarcomas was much higher than in GBMs. Aberrations of PTEN were the most frequent and occurred in 70% of samples. We identified genes differentially expressed in gliosarcoma compared to GBM (including collagen signature) and confirmed a difference in the protein level by immunohistochemistry. We found several novel translocations (including translocations in the RABGEF1 gene) creating potentially unfavorable combinations. Collected results on genetic alterations and transcriptomic profiles offer new insights into gliosarcoma pathobiology, highlight differences in gliosarcoma and GBM genetic backgrounds and point out to distinct molecular cues for targeted treatment.

Glioblastoma in the setting of prior lower grade gliomas - insights from SEER database

Introduction

Secondary glioblastomas (GBs) constitute a small subset of all GBs and tend to arise after a lower grade glioma. Though knowledge regarding this subset has gained traction in recent years, its definition continues to evolve, complicating its clinical management. Investigation of epidemiology and survival patterns may help provide needed insights.

Results

The age at GB diagnosis is significantly lower (46.22 vs 60.25 years) for group B. The distribution among type of GB (glioblastoma, giant cell glioblastoma, or gliosarcoma) was significantly different, with no diagnosis of giant cell GB in Group B. Compared to Group A, Group B exhibited a higher proportion of females, not married, smaller tumors, no GTR, and no radiation (all p < 0.05). GB-related observed survivals were comparable. Cox regression with inclusion of co-variates reveal no significant influence of GB group on observed survival. Regarding group B, mean age was 40.197 for diagnosis of initial lower grade glioma. The most common initial ICD-O-3 pathology was oligodendroglioma, NOS; astrocytoma, NOS; astrocytoma, anaplastic; and mixed glioma.

Methods

The SEER-18 registry was queried for patients with GBs. Patients were further classified into two GB groups: Group A – those with GB as the only primary tumor, and Group B – those with GB as a 2^nd primary or subsequent tumor and with history of lower grade gliomas. Demographics and clinical factors were compared between group A and B. Appropriate statistics were employed to calculate incidences and differences among factors and GB-related survivals between the groups.

Conclusions

Overall, Group B develops GBs at an earlier age, but observed survival remains similar to those with GBs as the only primary. Moreover, this subset also exhibit different proportions of the types of GBs, and well as differences in other key clinical factors (namely, gender and tumor size at presentation). Prior treatments for lower grade gliomas likely explain some of the differences noted regarding management course after diagnosis of GB.

Repurposing drugs for glioblastoma: From bench to bedside

Glioblastoma multiforme is the most common, aggressive and lethal type of brain tumor. It is a stage IV cancer disease with a poor prognosis, as the current therapeutic options (surgery, radiotherapy and chemotherapy) are not able to eradicate tumor cells. The approach to treat glioblastoma has not suffered major changes over the last decade and temozolomide (TMZ) remains the mainstay for chemotherapy. However, resistance mechanisms to TMZ and other chemotherapeutic agents are becoming more frequent. The lack of effective options is a reality that may be counterbalanced by repositioning known and commonly used drugs for other diseases. This approach takes into consideration the available pharmacokinetic, pharmacodynamic, toxicity and safety data, and allows a much faster and less expensive drug and product development process. In this review, an extensive literature search is conducted aiming to list drugs with repurposing usage, based on their preferential damage in glioblastoma cells through various mechanisms. Some of these drugs have already entered clinical trials, exhibiting favorable outcomes, which sparks their potential application in glioblastoma treatment.

Incorporating Advances in Molecular Pathology Into Brain Tumor Diagnostics

Recent advances in molecular pathology have reshaped the practice of brain tumor diagnostics. The classification of gliomas has been restructured with the discovery of isocitrate dehydrogenase (IDH) 1/2 mutations in the vast majority of lower grade infiltrating gliomas and secondary glioblastomas (GBM), with IDH-mutant astrocytomas further characterized by TP53 and ATRX mutations. Whole-arm 1p/19q codeletion in conjunction with IDH mutations now define oligodendrogliomas, which are also enriched for CIC, FUBP1, PI3K, NOTCH1, and TERT-p mutations. IDH-wild-type (wt) infiltrating astrocytomas are mostly primary GBMs and are characterized by EGFR, PTEN, TP53, NF1, RB1, PDGFRA, and CDKN2A/B alterations, TERT-p mutations, and characteristic copy number alterations including gains of chromosome 7 and losses of 10. Other clinically and genetically distinct infiltrating astrocytomas include the aggressive H3K27M-mutant midline gliomas, and smaller subsets that occur in the setting of NF1 or have BRAF V600E mutations. Low-grade pediatric gliomas are both genetically and biologically distinct from their adult counterparts and often harbor a single driver event often involving BRAF, FGFR1, or MYB/MYBL1 genes. Large scale genomic and epigenomic analyses have identified distinct subgroups of ependymomas tightly linked to tumor location and clinical behavior. The diagnosis of embryonal neoplasms also integrates molecular testing: (I) 4 molecularly defined, biologically distinct subtypes of medulloblastomas are now recognized; (II) 3 histologic entities have now been reclassified under a diagnosis of "embryonal tumor with multilayered rosettes (ETMR), C19MC-altered"; and (III) atypical teratoid/rhabdoid tumors (AT/RT) now require SMARCB1 (INI1) or SMARCA4 (BRG1) alterations for their diagnosis. We discuss the practical use of contemporary biomarkers for an integrative diagnosis of central nervous system neoplasia.

Gliosarcoma with primitive neuronal, chondroid, osteoid and ependymal elements

A 51-year-old man presented with a 2-week history of malaise. MRI revealed a large solid and cystic lesion with ring enhancement measuring 6.5 cm in diameter in the right frontal lobe. Histologically, the tumor consisted of various components: diffuse growth of atypical astrocytic cells consistent with glioblastoma, fascicular proliferation of atypical spindle cells such as fibrosarcoma, clusters of primitive neuronal cells, and foci of ependymal cells. The sarcomatous component also focally exhibited chondroid and osteoid differentiation. Immunohistochemically, tumor cells in the primitive neuronal component were immunoreactive for synaptophysin and CD56. The spindle cells were immunopositive for Slug and Twist, regulators of epithelial-mesenchymal transition. Direct DNA sequencing demonstrated C228T mutation in the TERT promoter in astrocytic, sarcomatous and primitive neuronal components, suggesting their identical origin. Although a few cases of gliosarcoma with primitive neuronal differentiation have previously been described, the finding that neuronal, glial and sarcomatous components share an identical mutation of the TERT promoter has not been reported. The tumor recurred at the original site 11 months after the first surgery. Interestingly, the recurrent tumor was composed exclusively of a glioblastomatous component, unlike past cases of recurrent gliosarcoma.

Treatment-associated TP53 DNA-binding domain missense mutations in the pathogenesis of secondary gliosarcoma

Background

Gliosarcoma is a rare variant of glioblastoma (GBM) that exhibits frequent mutations in TP53 and can develop in a secondary fashion after chemoradiation of a primary GBM. Whether temozolomide (TMZ)-induced mutagenesis of the TP53 DNA-binding domain (DBD) can drive the pathogenesis of gliosarcoma is unclear.

Methods

We identified a case of a primary GBM that rapidly progressed into secondary gliosarcoma shortly after chemoradiation was initiated. Bulk tumor was collected and gliomasphere cultures derived from both the pre- and post-treatment tumors. We performed targeted DNA sequencing and transcriptome analyses of the specimens to understand their phylogenetic relationship and identify differentially expressed gene pathways. Gliomaspheres from the primary GBM were treated with TMZ and then analyzed to compare patterns of mutagenesis in vivo and ex vivo.

Results

The pre- and post-treatment tumors shared EGFR, CDKN2A, and PTEN mutations, but only the secondary gliosarcoma exhibited TP53 DBD missense mutations. Two mutations, R110C, and R175H, were identified, each in distinct clones. Both were base transitions characteristic of TMZ mutagenesis. Gene expression analysis identified increased JAK-STAT signaling in the gliosarcoma, together with reduced expression of microRNAs known to regulate epithelial-mesenchymal transition. Ex vivo treatment of the GBM spheres with TMZ generated numerous variants in cancer driver genes, including TP53 and CDH1, which were mutated in the post-treatment tumor.

Conclusions

TMZ-induced TP53 gain-of-function mutations can have a driving role in secondary gliosarcoma pathogenesis. Analysis of variants identified in ex vivo TMZ-treated gliomaspheres may have utility in predicting GBM evolutionary trajectories in vivo during standard chemoradiation.

Primary Gliosarcoma of the Optic Nerve: A Unique Adult Optic Pathway Glioma

A 90-year-old woman presented with 1-year history of right-sided progressive proptosis, neovascular glaucoma, blindness, and worsening ocular pain. No funduscopic examination was possible because of a corneal opacity. Head CT scan without contrast demonstrated a heterogeneous 4.1 cm (anterior-posterior) by 1.7 cm (transverse) cylindrical mass arising in the right optic nerve and extending from the retrobulbar globe to the optic canal. She underwent palliative enucleation with subtotal resection of the orbital optic nerve and tumor. Pathological examination showed effacement of the optic nerve by an infiltrative high-grade glial neoplasm with biphasic sarcomeric differentiation. Invasion into the uvea and retina was present. The neoplasm was negative for melan-A, HMB45, tyrosinase, synaptophysin, smooth muscle actin, and epithelial membrane antigen. The glioma had strongly intense, but patchy immunopositivity for glial fibrillary acidic protein. Multiple foci of neoplastic cells had pericellular reticulin staining. The overall features were diagnostic of a gliosarcoma (World Health Organization grade IV) of the optic nerve. Postoperative MRI demonstrated postsurgical changes and residual gliosarcoma with extension into the optic chiasm. The patient died 2 and a half months after her enucleation surgery at her nursing home. Autopsy was unavailable due to the caregiver wishes, making a definitive cause of death unknown. Gliosarcoma is a rare variant of glioblastoma, and this is the first documented case presenting as a primary neoplasm of the optic nerve.

Gliosarcomas with the BRAF V600E mutation: a report of two cases and review of the literature

Gliosarcoma, which is regarded as a variant of glioblastoma, is a rare malignant neoplasm of the central nervous system. Both its sarcomatous component and glial component are reported to share significant clinical and genetic similarities. However, gliosarcomas are considered to be characterised by a lack of the BRAF V600E mutation. Here, we report two cases of gliosarcoma harbouring the BRAF V600E mutation, of which one case appears to have arisen de novo, while the other likely arose from ganglioglioma. Interestingly, the BRAF V600E mutation was detected only in the glial component in the first case, but was present in both the glial and the sarcomatous components in the recurrent gliosarcoma. Furthermore, the different mutation state of BRAF V600E in our two cases suggests that the malignant transformation of gliosarcoma might have different underlying genetic alterations and mechanisms in de novo versus recurrent gliosarcoma.

Retrospective Analysis of Molecular and Immunohistochemical Characterization of 381 Primary Brain Tumors

The classification of brain tumors has traditionally depended on microscopic examination of hematoxylin and eosin-stained tissue sections. The increased understanding of clinically relevant genetic alterations has led to the incorporation of molecular signatures as part of the diagnosis of brain malignancies. Advances in sequencing technologies have facilitated the use of next-generation sequencing (NGS) assays in clinical laboratories. We performed a retrospective analysis of sequencing results for 381 brain tumors tested by NGS at our institution using a validated, commercially available panel. The results of the NGS assay were analyzed in conjunction with the results of immunohistochemical stains. A genetic alteration was detected in approximately two thirds of the cases. The most commonly mutated genes were TP53 (37.2%), IDH1 (29.4%), PIK3CA (8%), PTEN (8%), and EGFR (7.5%). BRAF mutations were detected in ∼3% of the cases, including 50% of gangliogliomas and ∼20% of gliosarcomas. No mutations were detected in 6 medulloblastomas. PIK3CA and CTNNB1 mutations were detected in 1 rosette-forming glioneuronal tumor and 1 adamantinomatous craniopharyngioma, respectively. Approximately 23% of cases showed amplification of 1 or more of the genes included in the NGS panel. This analysis demonstrates the utility of NGS for detecting genetic alterations in brain tumors in the clinical setting.

Insights From Molecular Profiling of Adult Glioma

The comprehensive molecular profiling of cancer has resulted in new insights into the biology and classification of numerous tumor types. In the case of primary brain tumors that commonly affect adults, an emerging set of disease-defining biomarker sets is reshaping existing diagnostic entities that had previously been defined on the basis of their microscopic appearance. Substantial progress has been made in this regard for common primary brain tumors in adults, especially diffuse gliomas, where large-scale profiling efforts have led to the incorporation of highly prevalent molecular alterations that promote a biologically based classification as an adjunct to the traditional histopathologic approach. The growing awareness that histologically indistinguishable tumors can be divided into more precise and biologically relevant subgroups has demanded a more global routine approach to biomarker assessment. These considerations have begun to intersect with the decreasing costs and availability of genome-wide analysis tools and, thus, incorporation into routine practice. We review how molecular profiling already has led to an evolution in the classification of brain tumors. In addition, we discuss the likely trajectory of incorporation of global molecular profiling platforms into the routine clinical classification of adult brain tumors.

High prevalence of TP53 mutations is associated with poor survival and an EMT signature in gliosarcoma patients

Gliosarcoma (GS) is a rare variant (2%) of glioblastoma (GBM) that poses clinical genomic challenges because of its poor prognosis and limited genomic information. To gain a comprehensive view of the genomic alterations in GS and to understand the molecular etiology of GS, we applied whole-exome sequencing analyses for 28 GS cases (6 blood-matched fresh-frozen tissues for the discovery set, 22 formalin-fixed paraffin-embedded tissues for the validation set) and copy-number variation microarrays for 5 blood-matched fresh-frozen tissues. TP53 mutations were more prevalent in the GS cases (20/28, 70%) compared to the GBM cases (29/90, 32%), and the GS patients with TP53 mutations showed a significantly shorter survival (multivariate Cox analysis, hazard ratio=23.9, 95% confidence interval, 2.87-199.63, P=0.003). A pathway analysis showed recurrent alterations in MAPK signaling (EGFR, RASGRF2 and TP53), phosphatidylinositol/calcium signaling (CACNA1s, PLCs and ITPRs) and focal adhesion/tight junction (PTEN and PAK3) pathways. Genomic profiling of the matched recurrent GS cases detected the occurrence of TP53 mutations in two recurrent GS cases, which suggests that TP53 mutations play a role in treatment resistance. Functionally, we found that TP53 mutations are associated with the epithelial-mesenchymal transition (EMT) process of sarcomatous components of GS. We provide the first comprehensive genome-wide genetic alternation profiling of GS, which suggests novel prognostic subgroups in GS patients based on their TP53 mutation status and provides new insight in the pathogenesis and targeted treatment of GS.

Recurrent copy number alterations in low-grade and anaplastic pleomorphic xanthoastrocytoma with and without BRAF V600E mutation

Pleomorphic xanthoastrocytoma (PXA) is a rare localized glioma characterized by frequent BRAF V600E mutation and CDKN2A/B deletion. We explored the association of copy-number variants (CNVs) with BRAF mutations, tumor grade, and patient survival in a cohort of 41 PXA patients using OncoScan chromosomal microarray. Primary resection specimens were available in 38 cases, including 24 PXA and 14 anaplastic PXA (A-PXA), 23 BRAF V600E mutant tumors (61%). CNVs were identified in all cases and most frequently involved chromosome 9 with homozygous CDKN2A/B deletion (n = 33, 87%), a higher proportion than previously detected by comparative genomic hybridization (50%-60%) (37). CDKN2A/B deletion was present in similar proportion of PXA (83%), A-PXA (93%), BRAF V600E (87%), and wild-type (87%) tumors. Whole chromosome gains/losses were frequent, including gains +7 (n = 15), +2 (n = 11), +5 (n = 10), +21 (n = 10), +20 (n = 9), +12 (n = 8), +15 (n = 8), and losses -22 (n = 11), -14 (n = 7), -13 (n = 5). Losses and copy-neutral loss of heterozygosity were significantly more common in A-PXA, involving chromosomes 22 (P = 0.009) and 14 (P = 0.03). Amplification of 8p and 12q was identified in a single tumor. Histologic grade was a robust predictor of overall survival (P = 0.003), while other copy-number changes, including CDKN2A/B deletion, did not show significant association with survival. Distinct histologic patterns of anaplasia included increased mitotic activity in an otherwise classic PXA or associated with small cell, fibrillary, or epithelioid morphology, with loss of SMARCB1 expression in one case. In 10 cases, matched specimens were compared, including A-PXA with areas of distinct low- and high-grade morphology (n = 2), matched primary/tumor recurrence (n = 7), or both (n = 1). Copy-number changes on recurrence/anaplastic transformation were complex and highly variable, from nearly identical profiles to numerous copy-number changes. Overall, we confirm CDKN2A/B deletion as key a feature of PXA not associated with tumor grade or BRAF mutation, but central to the underlying genetics of PXA.

Glioma Subclassifications and Their Clinical Significance

The impact of targeted therapies in glioma has been modest. All the therapies that have demonstrated a significant survival benefit for gliomas in Phase III trials, including radiation, chemotherapy (temozolomide and PCV [procarbazine, lomustine, vincristine]), and tumor-treating fields, are based on nonspecific targeting of proliferating cells. Recent advances in the molecular understanding of gliomas suggest some potential reasons for the failure of more targeted therapies in gliomas. Specifically, the histologic-based glioma classification is composed of multiple different molecular subtypes with distinct biology, natural history, and prognosis. As a result of these insights, the diagnosis and classification of gliomas have recently been updated by the World Health Organization. However, these changes and other novel observations regarding glioma biomarkers and subtypes highlight several clinical challenges. First, the field is faced with the difficulty of reinterpreting the results of prior studies and retrospective data using the new classifications to clarify prognostic assessments and treatment recommendations for patients. Second, the new classifications and insights require rethinking the design and stratification of future clinical trials. Last, these observations provide the essential framework for the development and testing of new specific targeted therapies for particular glioma subtypes. This review aims to summarize the current literature regarding glioma subclassifications and their clinical relevance in this evolving field.

Gliosarcoma with Primary Skull Base Invasion

Gliosarcoma is an uncommon variant of glioblastoma, which commonly demonstrates dural attachment. However, skull base invasion is rarely seen with this entity. Herein, we report a 44-year-old female patient diagnosed with primary intracranial gliosarcoma extensively invading the skull base and muscles of mastication. She presented to our institution with a three-month history of difficult right jaw opening and retro-orbital pressure and one week of severe right-sided postauricular headache. Head CT demonstrated a 6 cm mass with marked bony erosion. Brain MRI at a one-week interval more clearly characterized tumor extension through the right orbit and muscles of mastication, with overall growth to 7 cm and worsening midline shift. The patient underwent a right frontotemporal craniotomy for gross total resection. Pathology confirmed the diagnosis of gliosarcoma, IDH-wildtype (WHO grade IV). Her postoperative course was uneventful and she was discharged at preoperative neurologic baseline. To our knowledge, this is the third reported case of a primary intracranial gliosarcoma with direct invasion of skull base, brain parenchyma, and extracranial compartment. However, this is the first report case of primary GS invading the surrounding musculature and orbit. This case report highlights the rapid aggressiveness of gliosarcomas and further a prior undescribed radiographic and anatomic finding of skull base invasion with this entity.

Transcription Regulation of the Human Telomerase Reverse Transcriptase (hTERT) Gene

Embryonic stem cells and induced pluripotent stem cells have the ability to maintain their telomere length via expression of an enzymatic complex called telomerase. Similarly, more than 85%–90% of cancer cells are found to upregulate the expression of telomerase, conferring them with the potential to proliferate indefinitely. Telomerase Reverse Transcriptase (TERT), the catalytic subunit of telomerase holoenzyme, is the rate-limiting factor in reconstituting telomerase activity in vivo. To date, the expression and function of the human Telomerase Reverse Transcriptase (hTERT) gene are known to be regulated at various molecular levels (including genetic, mRNA, protein and subcellular localization) by a number of diverse factors. Among these means of regulation, transcription modulation is the most important, as evident in its tight regulation in cancer cell survival as well as pluripotent stem cell maintenance and differentiation. Here, we discuss how hTERT gene transcription is regulated, mainly focusing on the contribution of trans-acting factors such as transcription factors and epigenetic modifiers, as well as genetic alterations in hTERT proximal promoter.