Glioblastoma (GBM), the most common primary malignant brain tumor in adults, is associated with significant morbidity and mortality despite maximal safe resection followed by chemo- and radiotherapy. GBMs contain self-renewing, tumorigenic glioma stem cells that contribute to tumor initiation, heterogeneity, therapeutic resistance, and recurrence. Intratumoral heterogeneity (ITH) of GBMs is also a major contributing factor to poor clinical outcomes associated with these high-grade glial tumors. Herein, the authors summarize recent discoveries and advances in the molecular and phenotypic characterization of GBMs with particular focus on ITH. In so doing, they attempt to highlight recent advances in molecular signatures/properties and metabolic alterations in an effort to clarify translational implications that may ultimately improve clinical outcomes.

OBJECTIVEDespite an aggressive multimodal therapeutic regimen, glioblastoma (GBM) continues to portend a grave prognosis, which is driven in part by tumor heterogeneity at both the molecular and cellular levels. Accordingly, herein the authors sought to identify metabolic differences between GBM tumor core cells and edge cells and, in so doing, elucidate novel actionable therapeutic targets centered on tumor metabolism.METHODSComprehensive metabolic analyses were performed on 20 high-grade glioma (HGG) tissues and 30 glioma-initiating cell (GIC) sphere culture models. The results of the metabolic analyses were combined with the Ivy GBM data set. Differences in tumor metabolism between GBM tumor tissue derived from within the contrast-enhancing region (i.e., tumor core) and that from the peritumoral brain lesions (i.e., tumor edge) were sought and explored. Such changes were ultimately confirmed at the protein level via immunohistochemistry.RESULTSMetabolic heterogeneity in both HGG tumor tissues and GBM sphere culture models was identified, and analyses suggested that tyrosine metabolism may serve as a possible therapeutic target in GBM, particularly in the tumor core. Furthermore, activation of the enzyme tyrosine aminotransferase (TAT) within the tyrosine metabolic pathway influenced the noted therapeutic resistance of the GBM core.CONCLUSIONSSelective inhibition of the tyrosine metabolism pathway may prove highly beneficial as an adjuvant to multimodal GBM therapies.

Neural tube defects (NTDs) are one of the greatest causes of childhood mortality and disability-adjusted life years worldwide. Global prevalence at birth is approximately 18.6 per 10,000 live births, with more than 300,000 infants with NTDs born every year. Substantial strides have been made in understanding the genetics, pathophysiology, and surgical treatment of NTDs, yet the natural history remains one of high morbidity and profound impairment of quality of life. Direct and indirect costs of care are enormous, which ensures profound inequities and disparities in the burden of disease in countries of low and moderate resources. All indices of disease burden are higher for NTDs in developing countries. The great tragedy is that the majority of NTDs can be prevented with folate fortification of commercially produced food. Unequivocal evidence of the effectiveness of folate to reduce the incidence of NTDs has existed for more than 25 years. Yet, the most comprehensive surveys of effectiveness of implementation strategies show that more than 100 countries fail to fortify, and consequently only 13% of folate-preventable spina bifida is actually prevented. Neurosurgeons harbor a disproportionate, central, and fundamental role in the management of NTDs and enjoy high standing in society. No organized group in medicine can speak as authoritatively or convincingly. As a result, neurosurgeons and organized neurosurgery harbor disproportionate potential to advocate for more comprehensive folate fortification, and thereby prevent the most common and severe birth defect to impact the human nervous system. Assertive, proactive, informed advocacy for folate fortification should be a central and integral part of the neurosurgical approach to NTDs. Only by making the prevention of dysraphism a priority can we best address the inequities often observed worldwide.

OBJECTIVEDespite significant recent efforts applied toward the development of efficacious therapies for glioblastoma (GBM) through exploration of GBM’s genome and transcriptome, curative therapeutic strategies remain highly elusive. As such, novel and effective therapeutics are urgently required. In this study, the authors sought to explore the kinomic landscape of GBM from a previously underutilized approach (i.e., spatial heterogeneity), followed by validation of Bruton’s tyrosine kinase (BTK) targeting according to this stepwise kinomic-based novel approach.METHODSTwelve GBM tumor samples were obtained and characterized histopathologically from 2 patients with GBM. PamStation peptide-array analysis of these tissues was performed to measure the kinomic activity of each sample. The Ivy GBM database was then utilized to determine the intratumoral spatial localization of BTK activity by investigating the expression of BTK-related transcription factors (TFs) within tumors. Genetic inhibition of BTK family members through lentiviral short hairpin RNA (shRNA) knockdown was performed to determine their function in the core-like and edge-like GBM neurosphere models. Finally, the small-molecule inhibitor of BTK, ONO/GS-4059, which is currently under clinical investigation in nonbrain cancers, was applied for pharmacological inhibition of regionally specified newly established GBM edge and core neurosphere models.RESULTSKinomic investigation identified two major subclusters of GBM tissues from both patients exhibiting distinct profiles of kinase activity. Comparatively, in these spatially defined subgroups, BTK was the centric kinase differentially expressed. According to the Ivy GBM database, BTK-related TFs were highly expressed in the tumor core, but not in edge counterparts. Short hairpin RNA–mediated gene silencing of BTK in previously established edge- and core-like GBM neurospheres demonstrated increased apoptotic activity with predominance of the sub-G1 phase of core-like neurospheres compared to edge-like neurospheres. Lastly, pharmacological inhibition of BTK by ONO/GS-4059 resulted in growth inhibition of regionally derived GBM core cells and, to a lesser extent, their edge counterparts.CONCLUSIONSThis study identifies significant heterogeneity in kinase activity both within and across distinct GBM tumors. The study findings indicate that BTK activity is elevated in the classically therapy-resistant GBM tumor core. Given these findings, targeting GBM’s resistant core through BTK may potentially provide therapeutic benefit for patients with GBM.

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