CDKN2A mutations have equivalent prognostic significance to homozygous deletion in IDH-mutant astrocytoma.

Homozygous deletion of CDKN2A/B is currently considered a molecular signature for grade 4 in IDH-mutant astrocytomas, irrespective of tumor histomorphology. The 2021 WHO Classification of CNS Tumors does not currently include grading recommendations for histologically lower-grade (grade 2-3) IDH-mutant astrocytoma with CDKN2A mutation or other CDKN2A alterations, and little is currently known about the prognostic implications of these alternative CDKN2A inactivating mechanisms. To address this, we evaluated a cohort of institutional and publicly available IDH-mutant astrocytomas, 15 with pathogenic mutations in CDKN2A, 47 with homozygous CDKN2A deletion, and 401 with retained/wildtype CDKN2A. The IDH-mutant astrocytomas with mutant and deleted CDKN2A had significantly higher overall copy number variation compared to those with retained/wildtype CDKN2A, consistent with more aggressive behavior. Astrocytoma patients with CDKN2A mutation had significantly worse progression-free (p = 0.0025) and overall survival (p < 0.0001) compared to grade-matched patients with wildtype CDKN2A, but statistically equivalent progression-free survival and overall survival outcomes to patients with CDKN2A deletion. No significant survival difference was identified between CDKN2A mutant cases with or without loss of the second allele. These findings suggest that CDKN2A mutation has a detrimental effect on survival in otherwise lower-grade IDH-mutant astrocytomas, similar to homozygous CDKN2A deletion, and should be considered for future grading schemes.

The prognostic impact of subclonal IDH1 mutation in grade 2-4 astrocytomas.

Background: Isocitrate dehydrogenase (IDH) mutations are thought to represent an early oncogenic event in glioma evolution, found with high penetrance across tumor cells; however, in rare cases, IDH mutation may exist only in a small subset of the total tumor cells (subclonal IDH mutation). Methods: We present 2 institutional cases with subclonal IDH1 R132H mutation. In addition, 2 large publicly available cohorts of IDH-mutant astrocytomas were mined for cases harboring subclonal IDH mutations (defined as tumor cell fraction with IDH mutation ≤0.67) and the clinical and molecular features of these subclonal cases were compared to clonal IDH-mutant astrocytomas. Results: Immunohistochemistry (IHC) performed on 2 institutional World Health Organization grade 4 IDH-mutant astrocytomas revealed only a minority of tumor cells in each case with IDH1 R132H mutant protein, and next-generation sequencing (NGS) revealed remarkably low IDH1 variant allele frequencies compared to other pathogenic mutations, including TP53 and/or ATRX. DNA methylation classified the first tumor as high-grade IDH-mutant astrocytoma with high confidence (0.98 scores). In the publicly available datasets, subclonal IDH mutation was present in 3.9% of IDH-mutant astrocytomas (18/466 tumors). Compared to clonal IDH-mutant astrocytomas (n = 156), subclonal cases demonstrated worse overall survival in grades 3 (P = .0106) and 4 (P = .0184). Conclusions: While rare, subclonal IDH1 mutations are present in a subset of IDH-mutant astrocytomas of all grades, which may lead to a mismatch between IHC results and genetic/epigenetic classification. These findings suggest a possible prognostic role of IDH mutation subclonality, and highlight the potential clinical utility of quantitative IDH1 mutation evaluation by IHC and NGS.

A Phase I Trial of VEGF-A Inhibition Combined with PD-L1 Blockade for Recurrent Glioblastoma.

Purpose: The treatment of glioblastoma (GBM) poses challenges. The use of immune checkpoint inhibition (ICI) has been disappointing as GBM is characterized by low mutational burden and low T-cell infiltration. The combination of ICI with other treatment modalities may improve efficacy. Patient and Methods: Patients with recurrent GBM were treated with avelumab, a human IgG1 antibody directed against PD-L1 (part A), or avelumab within a week after laser interstitial thermal therapy (LITT) and continuation of avelumab (part B). Bevacizumab was allowed to be combined with ICI to spare steroid use. The primary objective was to characterize the tolerability and safety of the regimens. The secondary objectives included overall survival, progression-free survival (PFS), signatures of plasma analytes, and immune cells. Results: A total of 12 patients (median age 64; range, 37-73) enrolled, five in part A and seven in part B. Two serious adverse events occurred in the same patient, LITT treated, not leading to death. The median survival from enrollment was 13 months [95% confidence interval (CI), 4-16 months] with no differences for part A or B. The median PFS was 3 months (95% CI, 1.5-4.5 months). The decrease in MICA/MICB, γδT cells, and CD4+ T cell EMRA correlated with prolonged survival. Conclusions: Avelumab was generally well tolerated. Adding bevacizumab to ICI may be beneficial by lowering cytokine and immune cell expression. The development of this combinatorial treatment warrants further investigation. Exploring the modulation of adaptive and innate immune cells and plasma analytes as biomarker signatures may instruct future studies in this dismal refractory disease. Significance: Our phase I of PD-L1 inhibition combined with LITT and using bevacizumab to spare steroids had a good safety profile for recurrent GBM. Developing combinatory treatment may help outcomes. In addition, we found significant immune modulation of cytokines and immune cells by bevacizumab, which may enhance the effect of ICI.

Utility of liquid biopsy in diagnosing isolated cerebral phaeohyphomycosis: illustrative case.

BACKGROUND: Cladophialophora bantiana is a dematiaceous, saprophytic fungus and a rare but reported cause of intracranial abscesses due to its strong neurotropism. Although it predominantly affects immunocompetent individuals with environmental exposure, more recently, its significance as a highly lethal opportunistic infection in transplant recipients has been recognized. Successful treatment requires timely but often challenging diagnosis, followed by complete surgical excision. Next-generation sequencing of microbial cell-free DNA (cfDNA) from plasma is a novel diagnostic method with the potential to identify invasive fungal infections more rapidly and less invasively than conventional microbiological testing, including brain biopsy. OBSERVATIONS: The authors described the case of a recipient of a liver transplant who presented with seizures and was found to have innumerable ring-enhancing intracranial lesions. The Karius Test, a commercially available method of next-generation sequencing of cfDNA, was used to determine the causative organism. Samples from the patient's plasma identified C. bantiana 6 days before culture results of the surgical specimen, allowing optimization of the empirical antifungal regimen, which led to a reduction in the size of the abscesses. LESSONS: The authors' findings suggest that microbial cfDNA sequencing may be particularly impactful in improving the management of brain abscesses in which the differential diagnosis is wide because of immunosuppression.

Critical assessment of DNA adenine methylation in eukaryotes using quantitative deconvolution.

The discovery of N6-methyldeoxyadenine (6mA) across eukaryotes led to a search for additional epigenetic mechanisms. However, some studies have highlighted confounding factors that challenge the prevalence of 6mA in eukaryotes. We developed a metagenomic method to quantitatively deconvolve 6mA events from a genomic DNA sample into species of interest, genomic regions, and sources of contamination. Applying this method, we observed high-resolution 6mA deposition in two protozoa. We found that commensal or soil bacteria explained the vast majority of 6mA in insect and plant samples. We found no evidence of high abundance of 6mA in Drosophila, Arabidopsis, or humans. Plasmids used for genetic manipulation, even those from Dam methyltransferase mutant Escherichia coli, could carry abundant 6mA, confounding the evaluation of candidate 6mA methyltransferases and demethylases. On the basis of this work, we advocate for a reassessment of 6mA in eukaryotes.

Anti-invasive efficacy and survival benefit of the YAP-TEAD inhibitor verteporfin in preclinical glioblastoma models.

BACKGROUND: Glioblastoma (GBM) remains a largely incurable disease as current therapy fails to target the invasive nature of glioma growth in disease progression and recurrence. Here, we use the FDA-approved drug and small molecule Hippo inhibitor Verteporfin (VP) to target YAP-TEAD activity, known to mediate convergent aspects of tumor invasion/metastasis, and assess the drug's efficacy and survival benefit in GBM models. METHODS: Up to 8 low-passage patient-derived GBM cell lines with distinct genomic drivers, including 3 primary/recurrent pairs, were treated with VP or vehicle (VEH) to assess in vitro effects on proliferation, migration, invasion, YAP-TEAD activity, and transcriptomics. Patient-derived orthotopic xenograft (PDX) models were used to assess VP's brain penetrance and effects on tumor burden and survival. RESULTS: VP treatment disturbed YAP/TAZ-TEAD activity; disrupted transcriptome signatures related to invasion, epithelial-to-mesenchymal, and proneural-to-mesenchymal transition, phenocopying TEAD1-knockout effects; and impaired tumor migration/invasion dynamics across primary and recurrent GBM lines. In an aggressive orthotopic PDX GBM model, short-term VP treatment consistently diminished core and infiltrative tumor burden, which was associated with decreased tumor expression of Ki67, nuclear YAP, TEAD1, and TEAD-associated targets EGFR, CDH2, and ITGB1. Finally, long-term VP treatment appeared nontoxic and conferred survival benefit compared to VEH in 2 PDX models: as monotherapy in primary (de novo) GBM and in combination with Temozolomide chemoradiation in recurrent GBM, where VP treatment associated with increased MGMT methylation. CONCLUSIONS: We demonstrate combined anti-invasive and anti-proliferative efficacy for VP with survival benefit in preclinical GBM models, indicating potential therapeutic value of this already FDA-approved drug if repurposed for GBM patients.

5-Aminolevulinic acid for enhanced surgical visualization of high-grade gliomas: a prospective, multicenter study.

OBJECTIVE: Greater extent of resection (EOR) is associated with longer overall survival in patients with high-grade gliomas (HGGs). 5-Aminolevulinic acid (5-ALA) can increase EOR by improving intraoperative visualization of contrast-enhancing tumor during fluorescence-guided surgery (FGS). When administered orally, 5-ALA is converted by glioma cells into protoporphyrin IX (PPIX), which fluoresces under blue 400-nm light. 5-ALA has been available for use in Europe since 2010, but only recently gained FDA approval as an intraoperative imaging agent for HGG tissue. In this first-ever, to the authors' knowledge, multicenter 5-ALA FGS study conducted in the United States, the primary objectives were the following: 1) assess the diagnostic accuracy of 5-ALA-induced PPIX fluorescence for HGG histopathology across diverse centers and surgeons; and 2) assess the safety profile of 5-ALA FGS, with particular attention to neurological morbidity. METHODS: This single-arm, multicenter, prospective study included adults aged 18-80 years with Karnofsky Performance Status (KPS) score > 60 and an MRI diagnosis of suspected new or recurrent resectable HGG. Intraoperatively, 3-5 samples per tumor were taken and their fluorescence status was recorded by the surgeon. Specimens were submitted for histopathological analysis. Patients were followed for 6 weeks postoperatively for adverse events, changes in the neurological exam, and KPS score. Multivariate analyses were performed of the outcomes of KPS decline, EOR, and residual enhancing tumor volume to identify predictive patient and intraoperative variables. RESULTS: Sixty-nine patients underwent 5-ALA FGS, providing 275 tumor samples for analysis. PPIX fluorescence had a sensitivity of 96.5%, specificity of 29.4%, positive predictive value (PPV) for HGG histopathology of 95.4%, and diagnostic accuracy of 92.4%. Drug-related adverse events occurred at a rate of 22%. Serious adverse events due to intraoperative neurological injury, which may have resulted from FGS, occurred at a rate of 4.3%. There were 2 deaths unrelated to FGS. Compared to preoperative KPS scores, postoperative KPS scores were significantly lower at 48 hours and 2 weeks but were not different at 6 weeks postoperatively. Complete resection of enhancing tumor occurred in 51.9% of patients. Smaller preoperative tumor volume and use of intraoperative MRI predicted lower residual tumor volume. CONCLUSIONS: PPIX fluorescence, as judged by the surgeon, has a high sensitivity and PPV for HGG. 5-ALA was well tolerated in terms of drug-related adverse events, and its application by trained surgeons in FGS for HGGs was not associated with any excess neurological morbidity.

Teaching quality in neurosurgery: quantitating outcomes over time.

OBJECTIVE: High-quality neurosurgery resident training is essential to developing competent neurosurgeons. Validated formative tools to assess faculty teaching performance exist, but are not used widely among Accreditation Council for Graduate Medical Education (ACGME) residency programs in the United States. Furthermore, their longer-term impact on teaching performance improvement and educational outcomes remains unclear. The goal of this study was to assess the impact of implementing an evaluation system to provide faculty with feedback on teaching performance in a neurosurgery residency training program over a 4-year period. METHODS: The authors performed a prospective cohort study in which a modified version of the System for Evaluation of Teaching Qualities (SETQ) instrument was administered to neurosurgical trainees in their department regularly every 6 months. The authors analyzed subscale score dynamics to identify the strongest correlates of faculty teaching performance improvement. ACGME program survey results and trainee performance on written board examinations were compared for the 3 years before and after SETQ implementation. RESULTS: The overall response rate among trainees was 91.8%, with 1044 surveys completed for 41 faculty. Performance scores improved progressively from cycle 1 to cycle 6. The strongest correlate of overall performance was providing positive feedback to trainees. Compared to the 3 years prior, the 3 years following SETQ implementation saw significant increases in written board examination and ACGME resident survey scores compared to the national mean. CONCLUSIONS: Implementation of SETQ was associated with significant improvements in faculty teaching performance as judged by trainees over a 4-year period, and guided curricular changes in the authors' training program that resulted in improved educational outcomes.

The Neurosurgeon's Armamentarium for Gliomas: An Update on Intraoperative Technologies to Improve Extent of Resection.

Maximal safe resection is the standard of care in the neurosurgical treatment of high-grade gliomas. To aid surgeons in the operating room, adjuvant techniques and technologies centered around improving intraoperative visualization of tumor tissue have been developed. In this review, we will discuss the most advanced technologies, specifically fluorescence-guided surgery, intraoperative imaging, neuromonitoring modalities, and microscopic imaging techniques. The goal of these technologies is to improve detection of tumor tissue beyond what conventional microsurgery has permitted. We describe the various advances, the current state of the literature that have tested the utility of the different adjuvants in clinical practice, and future directions for improving intraoperative technologies.

Epigenetic preconditioning with decitabine sensitizes glioblastoma to temozolomide via induction of MLH1.

INTRODUCTION: To improve the standard treatment paradigm for glioblastoma (GBM), efforts have been made to explore the efficacy of epigenetic agents as chemosensitizers. Recent data suggest possible synergy between decitabine (DAC), a DNA hypomethylating agent, and temozolomide (TMZ) in GBM, but the mechanism remains unclear. The objective of this study was to determine the effects of DAC on TMZ sensitization in a consecutively derived set of primary GBM cultures, with a focus on mismatch repair (MMR) proteins. METHODS: Half maximal inhibitory concentrations (IC50) of TMZ were calculated in eleven consecutive patient-derived GBM cell lines before and after preconditioning with DAC. MMR protein expression changes were determined by quantitative immunoblots and qPCR arrays. Single-molecule real-time (SMRT) sequencing of bisulfite (BS)-converted PCR amplicons of the MLH1 promoter was performed to determine methylation status. RESULTS: TMZ IC50 significantly changed in 6 of 11 GBM lines of varying MGMT promoter methylation status in response to DAC preconditioning. Knockdown of MLH1 after preconditioning reversed TMZ sensitization. SMRT-BS sequencing of the MLH1 promoter region revealed higher levels of baseline methylation at proximal CpGs in desensitized lines compared to sensitized lines. CONCLUSIONS: DAC enhances TMZ cytotoxicity in a subset of GBM cell lines, comprising lines both MGMT methylated and unmethylated tumors. This effect may be driven by levels of MLH1 via E2F1 transcription factor binding. Using unbiased long-range next-generation bisulfite-sequencing, we identified a region of the proximal MLH1 promoter with differential methylation patterns that has potential utility as a clinical biomarker for TMZ sensitization.

Widely metastatic glioblastoma with BRCA1 and ARID1A mutations: a case report.

BACKGROUND: Glioblastoma (GBM) is a highly malignant brain neoplasm with poor survival. Despite its aggressive nature, metastatic spread of GBM is identified only rarely. While the molecular alterations associated with GBM and its subtypes are well-described, there remains a gap in understanding which alterations may predispose towards metastasis. In this report, we present a case of GBM with multi-organ metastases and discuss its genomic alterations. CASE PRESENTATION: A 74-year-old woman was diagnosed with left occipital glioblastoma (IDH-wildtype, MGMT-unmethylated), for which she underwent resection, standard chemoradiation, and then stereotactic radiosurgery (SRS) for local recurrence. One month after SRS, work-up for a pathologic hip fracture revealed a left breast mass, lytic lesions involving pelvic bones, and multiple pulmonary and hepatic lesions. Biopsies of the breast and bone lesions both demonstrated metastatic IDH-wildtype GBM. For worsening neurologic symptoms, the patient underwent debulking of a large right temporal lobe recurrence and expired shortly thereafter. Autopsy confirmed metastatic GBM in multiple systemic sites, including bilateral lungs, heart, liver, thyroid, left breast, small bowel, omentum, peritoneal surfaces, visceral surfaces, left pelvic bone, and hilar lymph nodes. Targeted sequencing was performed on tissue samples obtained pre- and postmortem, as well as on cell cultures and an orthotopic mouse xenograft derived from premortem surgical specimens. A BRCA1 mutation (p.I571T) was the only variant found in common among the primary, recurrence, and metastatic specimens, suggesting its likely status as an early driver mutation. Multiple subclonal ARID1A mutations, which promote genomic instability through impairment of DNA mismatch repair, were identified only in the recurrence. Mutational spectrum analysis demonstrated a high percentage of C:G to T:A transitions in the post-treatment samples but not in the primary tumor. CONCLUSION: This case report examines a rare case of widely metastatic IDH-wildtype GBM with a clonal somatic mutation in BRCA1. Post-treatment recurrent tumor in the brain and in multiple systemic organs exhibited evidence of acquired DNA mismatch repair deficiency, which may be explained by functional loss of ARID1A. We identify a potential role for immune checkpoint and PARP inhibitors in the treatment of metastatic GBM.

Tumoral and immune heterogeneity in an anti-PD-1-responsive glioblastoma: a case study.

Clinical benefit of immune checkpoint blockade in glioblastoma (GBM) is rare, and we hypothesize that tumor clonal evolution and the immune microenvironment are key determinants of response. Here, we present a detailed molecular characterization of the intratumoral and immune heterogeneity in an IDH wild-type, MGMT-negative GBM patient who plausibly benefited from anti-PD-1 therapy with an unusually long 25-mo overall survival time. We leveraged multiplex immunohistochemistry, RNA-seq, and whole-exome data from the primary tumor and three resected regions of recurrent disease to survey regional tumor-immune interactions, genomic instability, mutation burden, and expression profiles. We found significant regional heterogeneity in the neoantigenic and immune landscape, with a differential T-cell signature among recurrent sectors, a uniform loss of focal amplifications in EGFR, and a novel subclonal EGFR mutation. Comparisons with recently reported correlates of checkpoint blockade in GBM and with TCGA-GBM revealed appreciable intratumoral heterogeneity that may have contributed to a differential PD-1 blockade response.

Clinical impact of intraoperative hyperlactatemia during craniotomy.

OBJECT: Patients often develop markedly elevated serum lactate levels during craniotomy although the reason for this is not entirely understood. Elevated lactate levels have been associated with poor outcomes in critically ill septic shock patients, as well as patients undergoing abdominal and cardiac surgeries. We investigated whether elevated lactate in craniotomy patients is associated with neurologic complications (new neurological deficits) as well as systemic complications. METHODS: We performed a cohort study of elective craniotomy patients. Demographic and intraoperative data were collected, as well as three timed intraoperative arterial lactate values. Additional lactate, creatinine and troponin values were collected immediately postoperatively as well as 12 and 24 hours postoperatively. Assessment for neurologic deficit was performed at 6 hours and 2 weeks postoperatively. Hospital length-of-stay and 30-day mortality were collected. RESULTS: Interim analysis of 81 patients showed that no patient had postoperative myocardial infarction, renal failure, or mortality within 30 days of surgery. There was no difference in the incidence of new neurologic deficit in patients with or without elevated lactate (10/26, 38.5% vs. 15/55 27.3%, p = 0.31). Median length of stay was significantly longer in patients with elevated lactate (6.5 vs. 3 days, p = 0.003). Study enrollment was terminated early due to futility (futility index 0.16). CONCLUSION: Elevated intraoperative serum lactate was not associated with new postoperative neurologic deficits, other end organ events, or 30 day mortality. Serum lactate was related to longer hospital stay.

Comparison of glioblastoma (GBM) molecular classification methods.

Glioblastoma (GBM) is the most aggressive and common form of brain cancer in adults. GBM is characterized by poor survival and remarkably high tumors heterogeneity (both intertumoral and intratumoral), and lack of effective therapies. Recent high-throughput data revealed heterogeneous genetic/genomic/epigenetic features and led to multiple methods aiming to classify tumors according to the key molecular events that drive the most aggressive cellular components so that targeted therapies can be developed for individual subtypes. However, GBM molecular subtypes have not led to improvement of patients outcomes. Targeted or tailored therapies for specific mutations or subtypes largely failed due to the complexities arising from intratumoral molecular heterogeneity. Most tumors develop resistance to treatment and soon recur. GBM stem cells (GSCs) have been identified. Recent single cell sequencing studies of GBM suggest that intratumoral cellular heterogeneity can be partially explained by tumor cell hierarchy arising from GBM stem cells. Therefore, the molecular subtypes based on patient derived GSCs may potentially lead to more effective subtype-specific treatments. In this paper, we review the molecular alterations of GBM and molecular subtyping methods as well as subtype plasticity in primary and recurrent tumors emphasizing the clinical relevance of potential targets for further drug development.

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.

Sensitivity to BUB1B Inhibition Defines an Alternative Classification of Glioblastoma.

Glioblastoma multiforme (GBM) remains a mainly incurable disease in desperate need of more effective treatments. In this study, we develop evidence that the mitotic spindle checkpoint molecule BUB1B may offer a predictive marker for aggressiveness and effective drug response. A subset of GBM tumor isolates requires BUB1B to suppress lethal kinetochore-microtubule attachment defects. Using gene expression data from GBM stem-like cells, astrocytes, and neural progenitor cells that are sensitive or resistant to BUB1B inhibition, we created a computational framework to predict sensitivity to BUB1B inhibition. Applying this framework to tumor expression data from patients, we stratified tumors into BUB1B-sensitive (BUB1BS) or BUB1B-resistant (BUB1BR) subtypes. Through this effort, we found that BUB1BS patients have a significantly worse prognosis regardless of tumor development subtype (i.e., classical, mesenchymal, neural, proneural). Functional genomic profiling of BUB1BR versus BUB1BS isolates revealed a differential reliance of genes enriched in the BUB1BS classifier, including those involved in mitotic cell cycle, microtubule organization, and chromosome segregation. By comparing drug sensitivity profiles, we predicted BUB1BS cells to be more sensitive to type I and II topoisomerase inhibitors, Raf inhibitors, and other drugs, and experimentally validated some of these predictions. Taken together, the results show that our BUB1BR/S classification of GBM tumors can predict clinical course and sensitivity to drug treatment. Cancer Res; 77(20); 5518-29. ©2017 AACR.

Prospective Isolation and Comparison of Human Germinal Matrix and Glioblastoma EGFR+ Populations with Stem Cell Properties.

Characterization of non-neoplastic and malignant human stem cell populations in their native state can provide new insights into gliomagenesis. Here we developed a purification strategy to directly isolate EGFR+/- populations from human germinal matrix (GM) and adult subventricular zone autopsy tissues, and from de novo glioblastoma (GBM) resections, enriching for cells capable of binding EGF ligand (LBEGFR+), and uniquely compared their functional and molecular properties. LBEGFR+ populations in both GM and GBM encompassed all sphere-forming cells and displayed proliferative stem cell properties in vitro. In xenografts, LBEGFR+ GBM cells showed robust tumor initiation and progression to high-grade, infiltrative gliomas. Whole-transcriptome sequencing analysis confirmed enrichment of proliferative pathways in both developing and neoplastic freshly isolated EGFR+ populations, and identified both unique and shared sets of genes. The ability to prospectively isolate stem cell populations using native ligand-binding capacity opens new doors onto understanding both normal human development and tumor cell biology.

PTEN Regulates Glutamine Flux to Pyrimidine Synthesis and Sensitivity to Dihydroorotate Dehydrogenase Inhibition.

Metabolic changes induced by oncogenic drivers of cancer contribute to tumor growth and are attractive targets for cancer treatment. Here, we found that increased growth of PTEN-mutant cells was dependent on glutamine flux through the de novo pyrimidine synthesis pathway, which created sensitivity to the inhibition of dihydroorotate dehydrogenase, a rate-limiting enzyme for pyrimidine ring synthesis. S-phase PTEN-mutant cells showed increased numbers of replication forks, and inhibitors of dihydroorotate dehydrogenase led to chromosome breaks and cell death due to inadequate ATR activation and DNA damage at replication forks. Our findings indicate that enhanced glutamine flux generates vulnerability to dihydroorotate dehydrogenase inhibition, which then causes synthetic lethality in PTEN-deficient cells due to inherent defects in ATR activation. Inhibition of dihydroorotate dehydrogenase could thus be a promising therapy for patients with PTEN-mutant cancers.Significance: We have found a prospective targeted therapy for PTEN-deficient tumors, with efficacy in vitro and in vivo in tumors derived from different tissues. This is based upon the changes in glutamine metabolism, DNA replication, and DNA damage response which are consequences of inactivation of PTENCancer Discov; 7(4); 380-90. ©2017 AACR.See related article by Brown et al., p. 391This article is highlighted in the In This Issue feature, p. 339.

Emerging interplay of genetics and epigenetics in gliomas: a new hope for targeted therapy.

Diffusely infiltrating gliomas are inherently heterogeneous tumors, and there are ongoing efforts to establish a classification scheme that incorporates new molecular and traditional histologic features. In less than a decade, high-throughput sequencing of gliomas has transformed the field, uncovering several pivotal, highly prevalent genetic alterations that stratify patients into different prognostic and treatment-response categories. We highlight the genetic aberrations recently discovered in isocitrate dehydrogenase, alpha thalassemia/mental retardation syndrome X-linked, death-domain-associated protein, histone H3.3, and telomerase reverse transcriptase and discuss how these mutations lead to unexpected changes in the epigenetic landscape in gliomas. We describe the opportunities these discoveries might provide for the development of novel targeted therapy aimed at reversing early epigenetic aberrations in glioma precursor cells. Finally, we discuss the challenges for effective treatment of this fatal disease posed by intratumoral heterogeneity and clonal evolution.