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Brain metastases from lung adenocarcinoma (BM-LUAD) frequently cause patient mortality. To identify genomic alterations that promote brain metastases, we performed whole-exome sequencing of 73 BM-LUAD cases. Using case-control analyses, we discovered candidate drivers of brain metastasis by identifying genes with more frequent copy-number aberrations in BM-LUAD compared to 503 primary LUADs. We identified three regions with significantly higher amplification frequencies in BM-LUAD, including MYC (12 versus 6%), YAP1 (7 versus 0.8%) and MMP13 (10 versus 0.6%), and significantly more frequent deletions in CDKN2A/B (27 versus 13%). We confirmed that the amplification frequencies of MYC, YAP1 and MMP13 were elevated in an independent cohort of 105 patients with BM-LUAD. Functional assessment in patient-derived xenograft mouse models validated the notion that MYC, YAP1 or MMP13 overexpression increased the incidence of brain metastasis. These results demonstrate that somatic alterations contribute to brain metastases and that genomic sequencing of a sufficient number of metastatic tumors can reveal previously unknown metastatic drivers.

Objective Posterior fossa meningiomas are surgically challenging tumors that are associated with high morbidity and mortality. We sought to investigate the anatomical distribution of clinically actionable mutations in posterior fossa meningioma to facilitate identifying patients amenable for systemic targeted therapy trials. Methods Targeted sequencing of clinically targetable AKT1, SMO, and PIK3CA mutations was performed in 61 posterior fossa meningioma using Illumina NextSeq 500 to a target depth of >500 × . Samples were further interrogated for 53 cancer-relevant RNA fusions by the Archer FusionPlex panel to detect gene rearrangements. Results AKT1 (E17K) mutations were detected in five cases (8.2%), four in the foramen magnum and one in the cerebellopontine angle. In contrast, none of the posterior fossa tumors harbored an SMO (L412F) or a PIK3CA (E545K) mutation. Notably, the majority of foramen magnum meningiomas (4/7, 57%) harbored an AKT1 mutation. In addition, common clinically targetable gene fusions were not detected in any of the cases. Conclusion A large subset of foramen magnum meningiomas harbor AKT1 E17K mutations and are therefore potentially amenable to targeted medical therapy. Genotyping of foramen magnum meningiomas may enable more therapeutic alternatives and guide their treatment decision process.

2016 Background: The blood-brain barrier (BBB) is a major impediment to pharmacological treatment of gliomas, a diffuse tumor infiltrating the peri-tumoral normal brain. Low-intensity pulsed ultrasound directed at the brain with concomitant administration of intravenous microbubbles (LIPU/MB), temporarily opens the BBB. This technique was previously shown with a first generation of the device in combination with carboplatin chemotherapy (Idbaih et al. 2019). Here we investigate the pharmacokinetics and safety of this approach in the context of repeated delivery of albumin-bound paclitaxel (ABX) to the peri-tumoral brain. To perform LIPU/MB-based BBB opening prior to ABX infusions, we used a novel 6 x 6 cm device with 9 ultrasound emitters (SC9) that is implanted in a skull window after tumor resection. Methods: A Phase 1 dose-escalation trial using Bayesian adaptive design was initiated at our institution (NCT04528680). Patients with recurrent operable glioblastoma, a WHO PS ≤ 2 and normal bone marrow and organ function were eligible. After tumor resection and implantation of SC9, repeated cycles of BBB opening by LIPU/MB immediately followed by ABX, was performed every 3 weeks. Intraoperative LIPU/MB and low dose ABX was given prior to tumor resection for investigation of pharmacokinetics. Results: Seventeen patients have been enrolled and six dose levels of ABX were used (40-260 mg/m2). Severe, reversible taxane-associated encephalopathy was observed in one patient at the max. planned dose level (260 mg/m2). The patient continued treatment at a lower dose in subsequent cycles. One patient developed grade 2 cumulative peripheral neuropathy. Other mild to moderate and reversible toxicities for ABX including myelosuppression, fatigue, alopecia were observed as expected. Intraoperative sonication and pharmacokinetic studies showed that ABX tissue concentrations in non-enhancing peri-tumoral brain were increased several-fold after LIPU/MB. On electron microscopy, sonicated tissue showed ultra-structural alterations in brain capillary endothelial cells. Molecular studies showed transcriptional dysregulation of membrane transporters, pathways related to trans-cytosis, cell permeability as well as cell-cell and cell-matrix adhesion. Updated results will be presented. Conclusions: The LIPU/MB using skull-implantable ultrasound enhances the penetration of large chemotherapeutic drugs such as ABX in large regions of the brain, a procedure that can be performed repeatedly and safely. LIPU-based BBB opening leads to ultrastructural and transcriptional alterations in brain endothelial cells. A Phase 2 clinical trial is planned to investigate efficacy of this approach. Funding: NIH/NCI 1R01CA245969-01A1, Carthera (SC9 devices), Celgene/BMS, Malnati Brain Tumor Institute, Moceri Family Foundation. Clinical trial information: NCT04528680.

Although lung adenocarcinomas frequently metastasize to the brain, treatment options for lung adenocarcinoma brain metastases are limited. We discovered novel candidate drivers of progression by using case-control analyses to compare whole-exome sequencing data from a cohort of 73 lung adenocarcinoma brain metastases to a control cohort of 503 primary lung adenocarcinomas. We identified 3 genomic regions with significantly more frequent amplifications in brain metastases compared to the control cohort: MYC (12% vs 6%), YAP1 (7% vs 0.8%) and MMP13 (10% vs 0.6%). We also identified CDKN2A/B as a region deleted at a significantly greater frequency in brain metastases compared to primary lung adenocarcinomas (27% vs 13%, respectively). We confirmed frequent amplifications of MYC and YAP1/MMP13 in an independent validation cohort of 105 lung adenocarcinoma brain metastasis samples using fluorescence in situ hybridization. We further validated that MYC, YAP1 and MMP13 can drive brain metastases in a patient-derived xenograft mouse model. We found a higher incidence of metastases to the brain in mice receiving intracardiac injections of tumor cells expressing the candidate drivers compared to tumor cells expressing LacZ as a control. These results indicate that somatic alterations can drive lung adenocarcinomas to metastasize to the brain. The candidate brain metastasis drivers that we identified may serve as therapeutic targets in patients with lung adenocarcinomas who develop this devastating complication.

Anti-angiogenic therapies for cancer such as VEGF neutralizing antibody bevacizumab have limited durability. While mechanisms of resistance remain undefined, it is likely that acquired resistance to anti-angiogenic therapy will involve alterations of the tumor microenvironment. We confirmed increased tumor-associated macrophages in bevacizumab-resistant glioblastoma patient specimens and two novel glioblastoma xenograft models of bevacizumab resistance. Microarray analysis suggested downregulated macrophage migration inhibitory factor (MIF) to be the most pertinent mediator of increased macrophages. Bevacizumab-resistant patient glioblastomas and both novel xenograft models of resistance had less MIF than bevacizumab-naive tumors, and harbored more M2/protumoral macrophages that specifically localized to the tumor edge. Xenografts expressing MIF-shRNA grew more rapidly with greater angiogenesis and had macrophages localizing to the tumor edge which were more prevalent and proliferative, and displayed M2 polarization, whereas bevacizumab-resistant xenografts transduced to upregulate MIF exhibited the opposite changes. Bone marrow-derived macrophage were polarized to an M2 phenotype in the presence of condition-media derived from bevacizumab-resistant xenograft-derived cells, while recombinant MIF drove M1 polarization. Media from macrophages exposed to bevacizumab-resistant tumor cell conditioned media increased glioma cell proliferation compared with media from macrophages exposed to bevacizumab-responsive tumor cell media, suggesting that macrophage polarization in bevacizumab-resistant xenografts is the source of their aggressive biology and results from a secreted factor. Two mechanisms of bevacizumab-induced MIF reduction were identified: (1) bevacizumab bound MIF and blocked MIF-induced M1 polarization of macrophages; and (2) VEGF increased glioma MIF production in a VEGFR2-dependent manner, suggesting that bevacizumab-induced VEGF depletion would downregulate MIF. Site-directed biopsies revealed enriched MIF and VEGF at the enhancing edge in bevacizumab-naive patients. This MIF enrichment was lost in bevacizumab-resistant glioblastomas, driving a tumor edge M1-to-M2 transition. Thus, bevacizumab resistance is driven by reduced MIF at the tumor edge causing proliferative expansion of M2 macrophages, which in turn promotes tumor growth.

Although lung adenocarcinomas frequently metastasize to the brain, treatment options for lung adenocarcinoma brain metastases (BM-LUAD) are limited. We discovered novel candidate drivers of progression by using case-control analyses to compare whole-exome sequencing data from a cohort of 73 BM-LUAD to a control cohort of 503 primary lung adenocarcinomas. We identified MYC, YAP1 and MMP13 as genomic regions with significantly more frequent amplifications in BM-LUAD compared to control cohort. We validated that MYC, YAP1 and MMP13 can drive brain metastases in a patient-derived xenograft mouse model, where incidence of brain metastases was higher in mice injected with tumor cells expressing the candidate drivers compared to tumor cells expressing LacZ. These results indicate that somatic alterations can drive lung adenocarcinomas to metastasize to the brain. These candidate drivers may serve as therapeutic targets in patients with brain metastatic lung adenocarcinomas. Citation Format: Naema Nayyar, David J. Shih, Ivanna Bihun, Ibiayi Dagogo-Jack, Corey M. Gill, Elisa Aquilanti, Mia Bertalan, Alexander Kaplan, Megan R. D'Andrea, Ugonma Chukwueke, Christopher Alvarez-Breckenridge, Matthew Lastrapes, Ben Kuter, Matthew R. Strickland, Juan Carlos Martinez-Gutierrez, Deepika Nagabhushan, Magali De Sauvage, Michael D. White, Brandyn A. Castro, Kaitlin Hoang, Sun Ha Paek, Sun Hye Park, Maria Martinez-Lage, Anna S. Berghoff, Parker Merrill, Elizabeth R. Gerstner, Tracy T. Batchelor, Matthew P. Frosch, Ryan P. Frazier, Darrell R. Borger, A John Iafrate, Sandro Santagata, Matthias Preusser, Daniel P. Cahill, Scott L. Carter, Priscilla K. Brastianos. Identifying genomic drivers of lung adenocarcinoma brain metastases [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4729.

Objective Posterior fossa meningiomas are surgically challenging tumors that are associated with high morbidity and mortality. We sought to investigate the anatomical distribution of clinically actionable mutations in posterior fossa meningioma to facilitate identifying patients amenable for systemic targeted therapy trials. Methods Targeted sequencing of clinically targetable AKT1 , SMO , and PIK3CA mutations was performed in 61 posterior fossa meningioma using Illumina NextSeq 500 to a target depth of >500 × . Samples were further interrogated for 53 cancer-relevant RNA fusions by the Archer FusionPlex panel to detect gene rearrangements. Results AKT 1 ( E17K ) mutations were detected in five cases (8.2%), four in the foramen magnum and one in the cerebellopontine angle. In contrast, none of the posterior fossa tumors harbored an SMO ( L412F ) or a PIK3CA ( E545K ) mutation. Notably, the majority of foramen magnum meningiomas (4/7, 57%) harbored an AKT1 mutation. In addition, common clinically targetable gene fusions were not detected in any of the cases. Conclusion A large subset of foramen magnum meningiomas harbor AKT1 E17K mutations and are therefore potentially amenable to targeted medical therapy. Genotyping of foramen magnum meningiomas may enable more therapeutic alternatives and guide their treatment decision process.

Background: Stroke can result in varying degrees of respiratory failure. Some patients require tracheostomy in order to facilitate weaning from mechanical ventilation, long-term airway protection, or a combination of the two. Little is known about the rate and predictors of this outcome in patients with severe stroke. We aim to determine the rate of tracheostomy after severe ischemic stroke. Methods: Using the Nationwide Inpatient Sample database from 2007 to 2009, patients hospitalized with ischemic stroke were identified based on validated International Classification of Diseases, 9th revision, Clinical Modification codes. Next, patients with stroke were stratified based on whether they were treated with or without decompressive craniectomy, and the rate of tracheostomy for each group was determined. A logistic regression analysis was used to identify predictors of tracheostomy after decompressive craniectomy. Survey weights were used to obtain nationally representative estimates. Results: In 1,550,000 patients discharged with ischemic stroke nationwide, the rate of tracheostomy was 1.3% (95% confidence interval [CI], 1.2-1.4%), with a 1.3% (95% CI, 1.1-1.4%) rate in patients without decompressive craniectomy and a 33% (95% CI, 26-39%) rate in the surgical treatment group. Logistic regression analysis identified pneumonia as being significantly associated with tracheostomy after decompressive craniectomy (odds ratio, 3.95; 95% CI, 1.956.91). Conclusions: Tracheostomy is common after decompressive craniectomy and is strongly associated with the development of pneumonia. Given its impact on patient function and potentially modifiable associated factors, tracheostomy may warrant further study as an important patient-centered outcome among pa

Clinical trials revealed limited response duration of glioblastomas to VEGF-neutralizing antibody bevacizumab. Thriving in the devascularized microenvironment occurring after antiangiogenic therapy requires tumor cell adaptation to decreased glucose, with 50% less glucose identified in bevacizumab-treated xenografts. Compared with bevacizumab-responsive xenograft cells, resistant cells exhibited increased glucose uptake, glycolysis, 13C NMR pyruvate to lactate conversion, and survival in low glucose. Glucose transporter 3 (GLUT3) was upregulated in bevacizumab-resistant versus sensitive xenografts and patient specimens in a HIF-1α-dependent manner. Resistant versus sensitive cell mitochondria in oxidative phosphorylation-selective conditions produced less ATP. Despite unchanged mitochondrial numbers, normoxic resistant cells had lower mitochondrial membrane potential than sensitive cells, confirming poorer mitochondrial health, but avoided the mitochondrial dysfunction of hypoxic sensitive cells. Thin-layer chromatography revealed increased triglycerides in bevacizumab-resistant versus sensitive xenografts, a change driven by mitochondrial stress. A glycogen synthase kinase-3β inhibitor suppressing GLUT3 transcription caused greater cell death in bevacizumab-resistant than -responsive cells. Overexpressing GLUT3 in tumor cells recapitulated bevacizumab-resistant cell features: survival and proliferation in low glucose, increased glycolysis, impaired oxidative phosphorylation, and rapid in vivo proliferation only slowed by bevacizumab to that of untreated bevacizumab-responsive tumors. Targeting GLUT3 or the increased glycolysis reliance in resistant tumors could unlock the potential of antiangiogenic treatments.

BackgroundGlioblastoma patients can develop hydrocephalus, either obstructive, typically at diagnosis as a result of mass effect, or communicating, usually later in the disease.ObjectiveTo characterize the indications and efficacy of ventriculoperitoneal (VP) shunting for patients with glioblastoma-associated hydrocephalus.MethodsRetrospective review was conducted of 841 glioblastoma patients diagnosed from 2004 to 2014, 64 (8%) of whom underwent VP shunting for symptomatic hydrocephalus, to analyze symptoms and outcomes after shunting. Overall survival and postshunt survival were analyzed with Kaplan-Meier methods, with predictors evaluated by use of Cox proportional hazards.ResultsOf the 64 patients who underwent shunting, 42 (66%) had communicating hydrocephalus (CH) and 22 (34%) had obstructive hydrocephalus (OH). CH patients underwent more preshunt craniotomies than those with noncommunicating hydrocephalus, with a mean of 2.3 and 0.7 surgeries, respectively ( P < .001). Ventricular entry during craniotomy occurred in 52% of CH patients vs 59% of those with OH ( P = .8). After shunting, 61% of all patients achieved symptomatic improvement, which was not associated with hydrocephalus variant ( P > .99). Hydrocephalus symptom improvement rates were as follows: headache, 77%; lethargy, 61%; and altered cognition or memory, 54%. Symptomatic improvement was more likely in patients who were younger at shunt placement (hazard ratio, 0.96; P = .045). Symptomatic improvement, shorter time between glioblastoma diagnosis and shunt placement, and CH rather than OH led to improved postshunt survival (hazard ratio = 0.24-0.99; P = .01-.04).ConclusionVP shunting improves symptoms in most glioblastoma patients with suspected CH or OH, specifically younger patients. Symptomatic improvement, shorter duration between glioblastoma diagnosis and shunt placement, and CH rather than OH improve postshunt survival.

Metastases to the brain are a common complication of various cancers and are associated with poor prognosis. Management of these patients requires a multidisciplinary approach including whole-brain radiation therapy, stereotactic radiosurgery, surgical resection, chemotherapy, and supportive treatment. Because of recent technological advancements in genomics, our understanding of the genetics of brain metastases is rapidly advancing. This has led to the discovery of many potential genetic therapeutic targets in metastatic brain lesions. One of the limitations to systemic therapies is their limited ability to cross the blood brain barrier, necessitating the urgency to develop clinical trials to evaluate efficacy. A description of these genetic mutations, targeted therapies, and associated clinical trials in brain metastases from lung cancers, breast cancers, and melanoma is outlined in this review.

BACKGROUND: Patients with incomplete surgical resection of medulloblastoma are controversially regarded as having a marker of high-risk disease, which leads to patients undergoing aggressive surgical resections, so-called second-look surgeries, and intensified chemoradiotherapy. All previous studies assessing the clinical importance of extent of resection have not accounted for molecular subgroup. We analysed the prognostic value of extent of resection in a subgroup-specific manner. METHODS: We retrospectively identified patients who had a histological diagnosis of medulloblastoma and complete data about extent of resection and survival from centres participating in the Medulloblastoma Advanced Genomics International Consortium. We collected from resections done between April, 1997, and February, 2013, at 35 international institutions. We established medulloblastoma subgroup affiliation by gene expression profiling on frozen or formalin-fixed paraffin-embedded tissues. We classified extent of resection on the basis of postoperative imaging as gross total resection (no residual tumour), near-total resection (30 Gy vs no craniospinal irradiation). The primary analysis outcome was the effect of extent of resection by molecular subgroup and the effects of other clinical variables on overall and progression-free survival. FINDINGS: We included 787 patients with medulloblastoma (86 with WNT tumours, 242 with SHH tumours, 163 with group 3 tumours, and 296 with group 4 tumours) in our multivariable Cox models of progression-free and overall survival. We found that the prognostic benefit of increased extent of resection for patients with medulloblastoma is attenuated after molecular subgroup affiliation is taken into account. We identified a progression-free survival benefit for gross total resection over sub-total resection (hazard ratio [HR] 1·45, 95% CI 1·07-1·96, p=0·16) but no overall survival benefit (HR 1·23, 0·87-1·72, p=0·24). We saw no progression-free survival or overall survival benefit for gross total resection compared with near-total resection (HR 1·05, 0·71-1·53, p=0·8158 for progression-free survival and HR 1·14, 0·75-1·72, p=0·55 for overall survival). No significant survival benefit existed for greater extent of resection for patients with WNT, SHH, or group 3 tumours (HR 1·03, 0·67-1·58, p=0·89 for sub-total resection vs gross total resection). For patients with group 4 tumours, gross total resection conferred a benefit to progression-free survival compared with sub-total resection (HR 1·97, 1·22-3·17, p=0·0056), especially for those with metastatic disease (HR 2·22, 1·00-4·93, p=0·050). However, gross total resection had no effect on overall survival compared with sub-total resection in patients with group 4 tumours (HR 1·67, 0·93-2·99, p=0·084). INTERPRETATION: The prognostic benefit of increased extent of resection for patients with medulloblastoma is attenuated after molecular subgroup affiliation is taken into account. Although maximum safe surgical resection should remain the standard of care, surgical removal of small residual portions of medulloblastoma is not recommended when the likelihood of neurological morbidity is high because there is no definitive benefit to gross total resection compared with near-total resection. FUNDING: Canadian Cancer Society Research Institute, Terry Fox Research Institute, Canadian Institutes of Health Research, National Institutes of Health, Pediatric Brain Tumor Foundation, and the Garron Family Chair in Childhood Cancer Research.

Invasive resistance limits anti-angiogenic therapy's efficacy. We previously reported upregulated c-Met and b1 integrin in bevacizumab-resistant glioblastomas. We hypothesized chemotactic c-Met/HGF and haptotactic b1 integrin physically interact, forming an alliance driving invasive growth. Immunoprecipitated lysates of intracranial xenografts of U87-BevR and U87-BevS, models of bevacizumab-resistance and responsiveness, revealed robust c-Met/b1 integrin interactions in bevacizumab-treated U87-BevRs, and minimal complex in bevacizumab-treated U87-BevS, IgG-treated U87-BevR, or U87-BevS. Proximity ligation assays (PLAs) mirrored results of our immunopreicipitation. In culture, complex formation increased dose-dependently by bevacizumab-induced VEGF depletion, exposure to c-Met ligand HGF, and hypoxia. Complex formation was inhibited by VEGF165, the predominant VEGF isoform, and endothelial cell conditioned medium. Far-western blotting demonstrated only extracellular c-Met domain to bind b1 integrin. The c-Met/b1 integrin interaction led to cross-activation, with increasing concentrations of b1 integrin ligand fibronectin which increased c-Met phosphorylation. This was inhibited with integrin-linked kinase (ILK) knockdown. Complex induction via iDimerize, where b1 integrin/c-Met were tagged with complementary proteins, forming a complex upon heterodimer addition, increased migration substantially (P < 0.05). Site-directed biopsy of bevacizumab-resistant glioblastoma patient revealed increased complex formation progressing from core to enhancing edge to invasive cells outside enhancement. PLAs revealed 20-fold more c-Met/b1 complexes after bevacizumab resistance in patient-specimens compared to bevacizumab-naive glioblastomas at recurrence (P < 0.05). Furthermore, the percentage of cMet/b1 integrin from 20 patients taken at diagnosis correlated inversely with survival (P < 0.05). Anti-angiogenic therapy dose on complex formation in vivo by treating xenografts with 3 mg/kg bevacizumab was as effective as 10 mg/kg; however, only the latter contained c-Met/b1 complexes. A patient receiving 5mg/kg of bevacizumab, had no increased complex under PLA. In summary, we have demonstrated a mechanism where b1 integrin forms a complex with c-Met in bevacizumab-resistant glioblastoma, leading to allosteric cross-activation, driving the invasive resistant phenotype.

Myeloid Derived Suppressor Cells (MDSCs) are present in most solid tumors, including glioblastoma (GBM), where they can block the activation of tumor-reactive T-cells and support tumor growth. Our lab and others have demonstrated the important roles of cyclooxygenase (COX)-2 as well as its enzymatic product, prostaglandin E2 (PGE2), in MDSC development, accumulation, and function. PGE2 mediates cellular responses through its receptors, EP1-EP4, of which EP4 is known to play an important role in anti-tumor immune responses. We therefore evaluated the impact of ONO-AE3-208, an EP4 antagonist, on MDSC function, tumor growth, and T-cell activation in gliomas. Our in vitro studies demonstrated that while PGE2 and ONO-AE3-208 treatment did not alter the growth of SB28 mouse glioma cells, ONO-AE3-208 reversed the MDSC phenotype of bone marrow cells induced by PGE2 or SB28 glioma cell line-derived conditioned media. Similarly, ONO-AE3-208 restored interferon-γ production by CD8 T-cells following PGE2 treatment. In vivo, ONO-AE3-208 treatment significantly prolonged survival of mice bearing established intracranial C57BL/6-syngeneic SB28 gliomas in wild-type but not RAG1-/- immunodeficient mice. Immunostaining and flow cytometry revealed that ONO-AE3-208-treated gliomas were infiltrated by fewer MDSCs compared with control mice. RT-PCR analysis of glioma-infiltrating MDSCs demonstrated that ONO-AE3-208 treatment suppressed Arg1 and Cox2 expression levels in both Ly6G+ and Ly6C+ MDSC populations as well as Tgfb1 and Il4ra levels in Ly6G+ MDSCs. Consistently, glioma-infiltrating lymphocytes in ONO-AE3-208 treated tumor-bearing mice revealed enhanced Ifng expression compared with control mice, suggestive of enhanced T-cell activity. Finally, combination therapy using anti-PD1 monoclonal antibody with ONO-AE3-208 in the anti-PD1-sensitive GL261 glioma model resulted in further prolonged survival compared with anti-PD1 therapy alone. Our data demonstrate that ONO-AE3-208 may be useful in the treatment of glioma patients to suppress MDSCs and promote anti-tumor immunity.

Initial enthusiasm after promising Phase II trials for treating recurrent glioblastomas with the antiangiogenic drug bevacizumab—a neutralizing antibody targeting vascular endothelial growth factor—was tempered by recent Phase III trials showing no efficacy for treating newly diagnosed glioblastomas. As a result, there is uncertainty about the appropriate indications for the use of bevacizumab in glioblastoma treatment. There are also concerns about the effects of bevacizumab on wound healing that neurosurgeons must be aware of. In addition, biochemical evidence suggests a percentage of tumors treated with bevacizumab for an extended period of time will undergo transformation into a more biologically aggressive and invasive phenotype with a particularly poor prognosis. Despite these concerns, there remain numerous examples of radiological and clinical improvement after bevacizumab treatment, particularly in patients with recurrent glioblastoma with limited therapeutic options. In this paper, the authors review clinical results with bevacizumab for glioblastoma treatment to date, ongoing trials designed to address unanswered questions, current clinical indications based on existing data, neurosurgical implications of bevacizumab use in patients with glioblastoma, the current scientific understanding of the tumor response to short- and long-term bevacizumab treatment, and future studies that will need to be undertaken to enable this treatment to fulfill its therapeutic promise for glioblastoma.

While radiation therapy has been standard of care for newly diagnosed glioblastoma for several decades, it only delays but does not prevent recurrence of these aggressive tumors. Therefore, the identification and targeting of factors allowing glioblastoma cells to escape the deleterious effects of radiation is essential to allow this therapeutic modality to fulfill its potential. In an elegant study published in 2010, the Brown lab reported that irradiation induces recruitment of bone marrow-derived cells (BMDCs) into glioblastoma to form blood vessels de novo, a process defined as vasculogenesis, in contrast to angiogenesis which involves the remodeling of existing vessels in the tumor bed.1 In that study, pharmacologic inhibition of HIF-1 or of the interaction between the chemokine stromal derived factor-1 (SDF-1, CXCL12) and its receptor CXCR4 prevented the influx of BMDCs, primarily CD11b+ myelomonocytes, and the development of functional tumor vasculature after radiation, resulting in abrogation of tumor regrowth.1 Now, in a follow-up study entitled “Blockade of SDF-1 after irradiation inhibits tumor recurrences of autochthonous brain tumors in rats” published in this issue of Neuro-Oncology2, Liu and colleagues from that same group sought to improve upon limitations previously reported when they1 and others3 targeted the SDF-1/CXCR4 interaction using the small molecule CXCR4 inhibitor plerixafor (AMD3100). Specifically, the authors noted that endothelial cells in tumors like glioblastoma express high levels of CXCR7, the more recently discovered second receptor for SDF-1.4 Of note, besides its blockade of CXCR4, plerixafor is actually an allosteric agonist of CXCR7,5 which can signal through β-arrestin and may activate the endothelium leading to increased invasiveness of cancer cells.6 The authors therefore investigated combining radiation therapy with NOX-A12, 45 L-enantiomeric RNA nucleotides which form a structural scaffold that recognizes SDF-1 with high affinity and thus efficiently blocks the chemokine's interaction with CXCR4 and CXCR7 (Figure 1). They showed that NOX-A12 inhibits SDF-1 dependent chemotaxis of CXCR4 myelomonocytes and SDF-1 dependent CXCR7 internalization in endothelial cells. Open in a separate window Fig. 1. Dual receptors lead to dual functions of SDF-1 (CXCL12) in glioblastoma vasculogenesis after radiation therapy. Irradiated tumor cells secrete SDF-1, which binds CXCR4 expressed by marrow-derived myelomonocytes and CXCR7 expressed by marrow-derived endothelial precursors, which together participate in vasculogenesis.

Glioblastomas are the most common primary tumor of the brain. These tumors are differentiated from other tumors because of their highly vascularized nature, making them a prime target for anti-angiogenic therapies. Multiple phase II trials have investigated the efficacy of bevacizumab (Avastin), an antibody targeting vascular endothelial growth factor (VEGF), on recurrent glioblastomas. The beneficial results of bevacizumab in these studies have led to randomized Phase III trials looking at the impact of using bevacizumab at the time of diagnosis by adding it to the standard Stupp protocol of radiation therapy plus 6 months of temozolomide. Due to the fact that there continues to be a fraction of patients who do not respond or have disease progression while on bevacizumab therapy as well as patients who experience side effects of bevacizumab requiring stoppage of treatment, future studies will be needed to determine, potentially by gene expression studies, the best candidates for this targeted therapy.

Clinical trials revealed limited response duration of glioblastomas to the anti-angiogenic therapy bevacizumab, a VEGF-neutralizing antibody. Bevacizumab-resistant glioblastomas exhibit increased invasiveness and 50% more tumor-associated macrophages (TAMs), which can be of classical M1 or pro-tumoral M2 subtypes. As macrophage migration inhibitory factor (MIF) regulates tumor invasion and macrophage recruitment, we investigated MIF's role in bevacizumab resistance in glioblastoma. Patient bevacizumab-resistant glioblastomas exhibited 2-fold less MIF protein than bevacizumab-naive glioblastomas (n = 10; p < 0.05). Bevacizumab-resistant xenografts exhibited 6-fold less MIF protein and increased invasiveness than isogeneic bevacizumab-responsive xenografts (p < 0.05). Immunoprecipitation revealed that bevacizumab bound MIF, likely reflecting its 30% homology to the VEGF protein structure. Furthermore, VEGF stimulation of U87 cells in vitro increased MIF transcription and secretion 5-fold (p < 0.05), suggesting VEGF depletion as another mechanism of MIF downregulation. Site-directed biopsies of bevacizumab-naive glioblastomas revealed enriched MIF expression at the enhancing tumor margin, which was lost in bevacizumab-resistant glioblastomas (p < 0.05). A similar regional pattern of expression was seen with VEGF, supporting its role in stimulating tumor cell MIF secretion. Continued bevacizumab treatment of bevacizumab-resistant xenografts increased M2-like CD11b+ TAMs, 3-fold, with preferential localization at the tumor margin (p < 0.05). The same pattern of recruitment and polarization was seen in U87/MIF-shRNA relative to U87/control-shRNA intracranial xenografts (p < 0.05). When co-cultured with cells from bevacizumab-resistant xenografts or U87/MIF-shRNA cells, bone marrow matured to an M2-like phenotype (p < 0.05), while an M1-like phenotype was generated with addition of recombinant MIF in a dose-dependent manner (p < 0.05). In conclusion, MIF expression is enriched at the glioblastoma margin, a pattern that may create a perimeter of inflammatory M1-like TAMs. This pattern is lost with bevacizumab resistance, likely due to bevacizumab-induced MIF depletion and diminished VEGF-induced MIF upregulation. MIF depletion leads to M2-like TAM polarization and recruitment to the tumor margin, thus softening the tumor border and promoting invasive bevacizumab resistance.

Clinical trials revealed limited response duration of glioblastomas to VEGF-neutralizing antibody bevacizumab. Thriving in the harsh microenvironment created by anti-angiogenic therapy requires that tumors metabolically adapt to decreased nutrients. We investigated the hypothesis that metabolic reprogramming occurs during the evolution of anti-angiogenic therapy resistance. Bevacizumab treatment lowered glucose levels 3-fold in U87 xenografts (P 0.05). HSP60 was the only assessed mitochondrial enzyme with less expression in U87-BevR versus U87-BevS xenografts (P 0.05). We found bevacizumab resistance to be associated with greater GLUT3-mediated uptake of the reduced glucose levels, impaired mitochondrial health, and greater lipid production. Treatments targeting these potential points of weakness in resistant tumors should be developed and considered for use alongside anti-angiogenic therapy in glioblastoma.

Frontal sinus fractures are heterogeneous, and management of these fractures is often modified based on injury pattern and institutional experience. The optimal initial treatment of frontal sinus fractures is controversial. Treatment strategies are aimed at correcting cosmetic deformity, as well as at preventing delayed complications, including CSF fistulas, mucocele formation, and infection. Existing treatment options include observation, reconstruction, obliteration, cranialization, or a combination thereof. Modalities for treatment encompass both open surgical approaches and endoscopic techniques. In the absence of Class I data, the authors review the existing literature related to treatment strategies of frontal sinus fractures, particularly as they relate to CSF fistulas, to provide recommendations based on the best available evidence.