Bevacizumab for glioblastoma: current indications, surgical implications, and future directions.

Initial enthusiasm after promising Phase II trials for treating recurrent glioblastomas with the antiangiogenic drug bevacizumab­a neutralizing antibody targeting vascular endothelial growth factor­was 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.

Antigen-presenting B cells promote TCF-1+ PD1- stem-like CD8+ T-cell proliferation in glioblastoma.

Understanding the spatial relationship and functional interaction of immune cells in glioblastoma (GBM) is critical for developing new therapeutics that overcome the highly immunosuppressive tumor microenvironment. Our study showed that B and T cells form clusters within the GBM microenvironment within a 15-µm radius, suggesting that B and T cells could form immune synapses within the GBM. However, GBM-infiltrating B cells suppress the activation of CD8+ T cells. To overcome this immunosuppression, we leveraged B-cell functions by activating them with CD40 agonism, IFNγ, and BAFF to generate a potent antigen-presenting B cells named BVax. BVax had improved antigen cross-presentation potential compared to naïve B cells and were primed to use the IL15-IL15Ra mechanism to enhance T cell activation. Compared to naïve B cells, BVax could improve CD8 T cell activation and proliferation. Compared to dendritic cells (DCs), which are the current gold standard professional antigen-presenting cell, BVax promoted highly proliferative T cells in-vitro that had a stem-like memory T cell phenotype characterized by CD62L+CD44- expression, high TCF-1 expression, and low PD-1 and granzyme B expression. Adoptive transfer of BVax-activated CD8+ T cells into tumor-bearing brains led to T cell reactivation with higher TCF-1 expression and elevated granzyme B production compared to DC-activated CD8+ T cells. Adoptive transfer of BVax into an irradiated immunocompetent tumor-bearing host promoted more CD8+ T cell proliferation than adoptive transfer of DCs. Moreover, highly proliferative CD8+ T cells in the BVax group had less PD-1 expression than those highly proliferative CD8+ T cells in the DC group. The findings of this study suggest that BVax and DC could generate distinctive CD8+ T cells, which potentially serve multiple purposes in cellular vaccine development.

TIGIT and PD-1 Immune Checkpoint Pathways Are Associated With Patient Outcome and Anti-Tumor Immunity in Glioblastoma.

Glioblastoma (GBM) remains an aggressive brain tumor with a high rate of mortality. Immune checkpoint (IC) molecules are expressed on tumor infiltrating lymphocytes (TILs) and promote T cell exhaustion upon binding to IC ligands expressed by the tumor cells. Interfering with IC pathways with immunotherapy has promoted reactivation of anti-tumor immunity and led to success in several malignancies. However, IC inhibitors have achieved limited success in GBM patients, suggesting that other checkpoint molecules may be involved with suppressing TIL responses. Numerous IC pathways have been described, with current testing of inhibitors underway in multiple clinical trials. Identification of the most promising checkpoint pathways may be useful to guide the future trials for GBM. Here, we analyzed the The Cancer Genome Atlas (TCGA) transcriptomic database and identified PD1 and TIGIT as top putative targets for GBM immunotherapy. Additionally, dual blockade of PD1 and TIGIT improved survival and augmented CD8+ TIL accumulation and functions in a murine GBM model compared with either single agent alone. Furthermore, we demonstrated that this combination immunotherapy affected granulocytic/polymorphonuclear (PMN) myeloid derived suppressor cells (MDSCs) but not monocytic (Mo) MDSCs in in our murine gliomas. Importantly, we showed that suppressive myeloid cells express PD1, PD-L1, and TIGIT-ligands in human GBM tissue, and demonstrated that antigen specific T cell proliferation that is inhibited by immunosuppressive myeloid cells can be restored by TIGIT/PD1 blockade. Our data provide new insights into mechanisms of GBM αPD1/αTIGIT immunotherapy.

Genomic characterization of human brain metastases identifies drivers of metastatic lung adenocarcinoma.

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.

Genomic Analysis of Posterior Fossa Meningioma Demonstrates Frequent AKT1 E17K Mutations in Foramen Magnum Meningiomas.

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.

Ventriculoperitoneal Shunting for Glioblastoma: Risk Factors, Indications, and Efficacy.

BACKGROUND: Glioblastoma patients can develop hydrocephalus, either obstructive, typically at diagnosis as a result of mass effect, or communicating, usually later in the disease. OBJECTIVE: To characterize the indications and efficacy of ventriculoperitoneal (VP) shunting for patients with glioblastoma-associated hydrocephalus. METHODS: Retrospective 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. RESULTS: Of 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). CONCLUSION: VP 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.

GLUT3 upregulation promotes metabolic reprogramming associated with antiangiogenic therapy resistance.

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-3ß 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.

Novel approaches in genetic characterization and targeted therapy for brain metastases.

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.