Integration of Computational Pipeline to Streamline Efficacious Drug Nomination and Biomarker Discovery in Glioblastoma.

Glioblastoma multiforme (GBM) is the deadliest, most heterogeneous, and most common brain cancer in adults. Not only is there an urgent need to identify efficacious therapeutics, but there is also a great need to pair these therapeutics with biomarkers that can help tailor treatment to the right patient populations. We built patient drug response models by integrating patient tumor transcriptome data with high-throughput cell line drug screening data as well as Bayesian networks to infer relationships between patient gene expression and drug response. Through these discovery pipelines, we identified agents of interest for GBM to be effective across five independent patient cohorts and in a mouse avatar model: among them are a number of MEK inhibitors (MEKis). We also predicted phosphoglycerate dehydrogenase enzyme (PHGDH) gene expression levels to be causally associated with MEKi efficacy, where knockdown of this gene increased tumor sensitivity to MEKi and overexpression led to MEKi resistance. Overall, our work demonstrated the power of integrating computational approaches. In doing so, we quickly nominated several drugs with varying known mechanisms of action that can efficaciously target GBM. By simultaneously identifying biomarkers with these drugs, we also provide tools to select the right patient populations for subsequent evaluation.

RNA splicing analysis deciphers developmental hierarchies and reveals therapeutic targets in adult glioma.

Widespread alterations in RNA alternative splicing (AS) have been identified in adult gliomas. However, their regulatory mechanism, biological significance, and therapeutic potential remain largely elusive. Here, using a computational approach with both bulk and single cell RNA-sequencing, we uncover a prognostic AS signature linked with neural developmental hierarchies. Using advanced iPSC glioma models driven by glioma driver mutations, we show that this AS signature could be enhanced by EGFRvIII and inhibited by in situ IDH1 mutation. Functional validation of two isoform switching events in CERS5 and MPZL1 shows regulations of sphingolipid metabolism and SHP2 signaling, respectively. Analysis of upstream RNA binding proteins reveals PTBP1 as a key regulator of the AS signature where targeting of PTBP1 suppresses tumor growth and promotes the expression of a neuron marker TUJ1 in glioma stem-like cells. Overall, our data highlights the role of AS in impacting glioma malignance and heterogeneity and its potential as a therapeutic vulnerability for treating adult gliomas.

Stem cell modeling of nervous system tumors.

Nervous system tumors, particularly brain tumors, represent the most common tumors in children and one of the most lethal tumors in adults. Despite decades of research, there are few effective therapies for these cancers. Although human nervous system tumor cells and genetically engineered mouse models have served as excellent platforms for drug discovery and preclinical testing, they have limitations with respect to accurately recapitulating important aspects of the pathobiology of spontaneously arising human tumors. For this reason, attention has turned to the deployment of human stem cell engineering involving human embryonic or induced pluripotent stem cells, in which genetic alterations associated with nervous system cancers can be introduced. These stem cells can be used to create self-assembling three-dimensional cerebral organoids that preserve key features of the developing human brain. Moreover, stem cell-engineered lines are amenable to xenotransplantation into mice as a platform to investigate the tumor cell of origin, discover cancer evolutionary trajectories and identify therapeutic vulnerabilities. In this article, we review the current state of human stem cell models of nervous system tumors, discuss their advantages and disadvantages, and provide consensus recommendations for future research.

Mechanically Tunable Hydrogels with Self-Healing and Shape Memory Capabilities from Thermo-Responsive Amino Acid-Derived Vinyl Polymers.

In this study, we report the fabrication and characterization of self-healing and shape-memorable hydrogels, the mechanical properties of which can be tuned via post-polymerization crosslinking. These hydrogels were constructed from a thermo-responsive poly(N-acryloyl glycinamide) (NAGAm) copolymer containing N-acryloyl serine methyl ester (NASMe) units (5 mol%) that were readily synthesized via conventional radical copolymerization. This transparent and free-standing hydrogel is produced via multiple hydrogen bonds between PNAGAm chains by simply dissolving the polymer in water at a high temperature (~90 °C) and then cooling it. This hydrogel exhibited moldability and self-healing properties. The post-polymerization crosslinking of the amino acid-derived vinyl copolymer network with glutaraldehyde, which acts as a crosslinker between the hydroxy groups of the NASMe units, tuned mechanical properties such as viscoelasticity and tensile strength. The optimal crosslinker concentration efficiently improved the viscoelasticity. Moreover, these hydrogels exhibited shape fixation (~60%)/memory (~100%) behavior owing to the reversible thermo-responsiveness (upper critical solution temperature-type) of the PNAGAm units. Our multifunctional hydrogel, with moldable, self-healing, mechanical tunability via post-polymerization crosslinking, and shape-memorable properties, has considerable potential for applications in engineering and biomedical materials.

Integrated analysis of single-cell chromatin state and transcriptome identified common vulnerability despite glioblastoma heterogeneity.

In 2021, the World Health Organization reclassified glioblastoma, the most common form of adult brain cancer, into isocitrate dehydrogenase (IDH)-wild-type glioblastomas and grade IV IDH mutant (G4 IDHm) astrocytomas. For both tumor types, intratumoral heterogeneity is a key contributor to therapeutic failure. To better define this heterogeneity, genome-wide chromatin accessibility and transcription profiles of clinical samples of glioblastomas and G4 IDHm astrocytomas were analyzed at single-cell resolution. These profiles afforded resolution of intratumoral genetic heterogeneity, including delineation of cell-to-cell variations in distinct cell states, focal gene amplifications, as well as extrachromosomal circular DNAs. Despite differences in IDH mutation status and significant intratumoral heterogeneity, the profiled tumor cells shared a common chromatin structure defined by open regions enriched for nuclear factor 1 transcription factors (NFIA and NFIB). Silencing of NFIA or NFIB suppressed in vitro and in vivo growths of patient-derived glioblastomas and G4 IDHm astrocytoma models. These findings suggest that despite distinct genotypes and cell states, glioblastoma/G4 astrocytoma cells share dependency on core transcriptional programs, yielding an attractive platform for addressing therapeutic challenges associated with intratumoral heterogeneity.

Cooperativity between H3.3K27M and PDGFRA poses multiple therapeutic vulnerabilities in human iPSC-derived diffuse midline glioma avatars.

Diffuse midline glioma (DMG) is a leading cause of brain tumor death in children. In addition to hallmark H3.3K27M mutations, significant subsets also harbor alterations of other genes, such as TP53 and PDGFRA. Despite the prevalence of H3.3K27M, the results of clinical trials in DMG have been mixed, possibly due to the lack of models recapitulating its genetic heterogeneity. To address this gap, we developed human iPSC-derived tumor models harboring TP53R248Q with or without heterozygous H3.3K27M and/or PDGFRAD842V overexpression. The combination of H3.3K27M and PDGFRAD842V resulted in more proliferative tumors when gene-edited neural progenitor (NP) cells were implanted into mouse brains compared to NP with either mutation alone. Transcriptomic comparison of tumors and their NP cells of origin identified conserved JAK/STAT pathway activation across genotypes as characteristic of malignant transformation. Conversely, integrated genome-wide epigenomic and transcriptomic analyses, as well as rational pharmacologic inhibition, revealed targetable vulnerabilities unique to the TP53R248Q; H3.3K27M; PDGFRAD842V tumors and related to their aggressive growth phenotype. These include AREG-mediated cell cycle control, altered metabolism, and vulnerability to combination ONC201/trametinib treatment. Taken together, these data suggest that cooperation between H3.3K27M and PDGFRA influences tumor biology, underscoring the need for better molecular stratification in DMG clinical trials.

Age-Dependent Hemorrhage Risk and Obliteration Benefit After Radiosurgery for Brain Arteriovenous Malformation.

PURPOSE: Because patients with untreated brain arteriovenous malformations (BAVMs) are at variable risks of cerebral hemorrhage and associated mortality and morbidity, it is essential to identify patient populations who benefit most from prophylactic interventions. This study aimed to examine age-dependent differences in the therapeutic effect of stereotactic radiosurgery (SRS) on BAVMs. METHODS AND MATERIALS: This retrospective observational study enrolled patients with BAVMs who underwent SRS at our institution between 1990 and 2017. The primary outcome was post-SRS hemorrhage, and the secondary outcomes included nidus obliteration, post-SRS early signal changes, and mortality. To investigate age-related differences in outcomes after SRS, we performed age-stratified analyses using the Kaplan-Meier analysis and weighted logistic regression with the inverse probability of censoring weighting (IPCW). To address significant differences in patient baseline characteristics, we also performed inverse probability of treatment weighting (IPTW) adjusted for possible confounders to investigate age-related differences in outcomes after SRS. RESULTS: A total of 735 patients with 738 BAVMs were stratified by age. Age-stratified analysis using a weighted logistic regression model with IPCW showed a direct correlation between patient age and post-SRS hemorrhage (odds ratio [OR], 95% confidence interval [CI], and P value: 2.20, 1.34-3.63, and .002 at 18 months; 1.86, 1.17-2.93, and .008 at 36 months; and 1.61, 1.05-2.48, and .030 at 54 months, respectively). The age-stratified analysis also showed an inverse relationship between age and obliteration over the first 42 months after SRS (OR, 95% CI, and P value: 0.05, 0.02-0.12, and <.001 at 6 months; 0.55, 0.44-0.70, and <.001 at 24 months; and 0.76, 0.63-0.91, and .002 at 42 months, respectively). These results were also confirmed with the IPTW analyses. CONCLUSIONS: Our analysis demonstrated that patients' age at SRS is significantly associated with hemorrhage and the nidus obliteration rate after treatment. In particular, younger patients are more likely to exhibit reduced cerebral hemorrhages and achieve earlier nidus obliteration compared with older patients.

Pioneering models of pediatric brain tumors.

Among children and adolescents in the United States (0 to 19 years old), brain and other central nervous system tumors are the second most common types of cancers, surpassed in incidence only by leukemias. Despite significant progress in the diagnosis and treatment modalities, brain cancer remains the leading cause of death in the pediatric population. There is an obvious unfulfilled need to streamline the therapeutic strategies and improve survival for these patients. For that purpose, preclinical models play a pivotal role. Numerous models are currently used in pediatric brain tumor research, including genetically engineered mouse models, patient-derived xenografts and cell lines, and newer models that utilize novel technologies such as genome engineering and organoids. Furthermore, extensive studies by the Children's Brain Tumor Network (CBTN) researchers and others have revealed multiomic landscapes of variable pediatric brain tumors. Combined with such integrative data, these novel technologies have enabled numerous applicable models. Genome engineering, including CRISPR/Cas9, expanded the flexibility of modeling. Models generated through genome engineering enabled studying particular genetic alterations in clean isogenic backgrounds, facilitating the dissection of functional mechanisms of those mutations in tumor biology. Organoids have been applied to study tumor-to-tumor-microenvironment interactions and to address developmental aspects of tumorigenesis, which is essential in some pediatric brain tumors. Other modalities, such as humanized mouse models, could potentially be applied to pediatric brain tumors. In addition to current valuable models, such novel models are anticipated to expedite functional tumor biology study and establish effective therapeutics for pediatric brain tumors.

Randomized phase III study of high-dose methotrexate and whole-brain radiotherapy with/without temozolomide for newly diagnosed primary CNS lymphoma: JCOG1114C.

BACKGROUND: The goal was to determine whether the addition of temozolomide (TMZ) to the standard treatment of high-dose methotrexate (HD-MTX) and whole-brain radiotherapy (WBRT) for primary central nervous system lymphoma (PCNSL) improves survival. METHODS: An open-label, randomized, phase III trial was conducted in Japan, enrolling immunocompetent patients aged 20-70 years with histologically confirmed, newly diagnosed PCNSL. After administration of HD-MTX, patients were randomly assigned to receive WBRT (30 Gy) ±â€…10 Gy boost (arm A) or WBRT ±â€…boost with concomitant and maintenance TMZ for 2 years (arm B). The primary endpoint was overall survival (OS). RESULTS: Between September 29, 2014 and October 15, 2018, 134 patients were enrolled, of whom 122 were randomly assigned and analyzed. At the planned interim analysis, 2-year OS was 86.8% (95% confidence interval [CI]: 72.5-94.0%) in arm A and 71.4% (56.0-82.2%) in arm B. The hazard ratio was 2.18 (95% CI: 0.95-4.98), with the predicted probability of showing the superiority of arm B at the final analysis estimated to be 1.3%. The study was terminated early due to futility. O6-methylguanine-DNA methyltransferase (MGMT) promoter methylation status was measured in 115 tumors, and it was neither prognostic nor predictive of TMZ response. CONCLUSIONS: This study failed to demonstrate the benefit of concomitant and maintenance TMZ in newly diagnosed PCNSL.

Structural studies of SALL family protein zinc finger cluster domains in complex with DNA reveal preferential binding to an AATA tetranucleotide motif.

The Spalt-like 4 transcription factor (SALL4) plays an essential role in controlling the pluripotent property of embryonic stem cells via binding to AT-rich regions of genomic DNA, but structural details on this binding interaction have not been fully characterized. Here, we present crystal structures of the zinc finger cluster 4 (ZFC4) domain of SALL4 (SALL4ZFC4) bound with different dsDNAs containing a conserved AT-rich motif. In the structures, two zinc fingers of SALL4ZFC4 recognize an AATA tetranucleotide. We also solved the DNA-bound structures of SALL3ZFC4 and SALL4ZFC1. These structures illuminate a common preference for the AATA tetranucleotide shared by ZFC4 of SALL1, SALL3, and SALL4. Furthermore, our cell biology experiments demonstrate that the DNA-binding activity is essential for SALL4 function as DNA-binding defective mutants of mouse Sall4 failed to repress aberrant gene expression in Sall4-/- mESCs. Thus, these analyses provide new insights into the mechanisms of action underlying SALL family proteins in controlling cell fate via preferential targeting to AT-rich sites within genomic DNA during cell differentiation.

Developing Bottom-Up Induced Pluripotent Stem Cell Derived Solid Tumor Models Using Precision Genome Editing Technologies.

Advances in genome and tissue engineering have spurred significant progress and opportunity for innovation in cancer modeling. Human induced pluripotent stem cells (iPSCs) are an established and powerful tool to study cellular processes in the context of disease-specific genetic backgrounds; however, their application to cancer has been limited by the resistance of many transformed cells to undergo successful reprogramming. Here, we review the status of human iPSC modeling of solid tumors in the context of genetic engineering, including how base and prime editing can be incorporated into "bottom-up" cancer modeling, a term we coined for iPSC-based cancer models using genetic engineering to induce transformation. This approach circumvents the need to reprogram cancer cells while allowing for dissection of the genetic mechanisms underlying transformation, progression, and metastasis with a high degree of precision and control. We also discuss the strengths and limitations of respective engineering approaches and outline experimental considerations for establishing future models.

Star-Shaped Peptide-Polymer Hybrids as Fast pH-Responsive Supramolecular Hydrogels.

Significant challenges have gone into the design of smart hydrogels, with numerous potential applications in the industrial, cosmetic, and biomedical fields. Herein, we report the synthesis of novel 4-arm self-assembling peptide-polyethylene glycol (PEG) hybrid star-shaped polymers and their comprehensive hydrogel properties. ß-sheet-forming oligopeptides with alternating hydrophobic Leu/ionizable Glu repeats and Cys residues were successfully conjugated to 4-arm PEG via a thiol-maleimide click reaction. The hybrid star-shaped polymers demonstrated good cytocompatibility and reversible ß-sheet (lightly acidic pH)-to-random coil (neutral and basic pH) transition in dilute aqueous solutions. At increasing polymer concentrations up to 0.5 wt %, the star-shaped polymers formed transparent hydrogels with shear-thinning and self-healing behaviors via ß-sheet self-assembly, as well as a conformation-dependent gel-sol transition. Interestingly, the star-shaped polymers responded rapidly to pH changes, causing gelation to occur rapidly within a few seconds from the change in pH. Hydrogel characteristics could be modulated by manipulating the length and net charge of the peptide blocks. Furthermore, these star-shaped polymers served as satisfactory network scaffolds that could respond to dynamic environmental changes in the pH-oscillation system, owing to their excellent gelation capability and pH sensitivity. As such, they are highly favorable for diverse applications, such as pH-responsive controlled release.

TERT promoter C228T mutation in neural progenitors confers growth advantage following telomere shortening in vivo.

BACKGROUND: Heterozygous TERT (telomerase reverse transcriptase) promoter mutations (TPMs) facilitate TERT expression and are the most frequent mutation in glioblastoma (GBM). A recent analysis revealed this mutation is one of the earliest events in gliomagenesis. However, no appropriate human models have been engineered to study the role of this mutation in the initiation of these tumors. METHOD: We established GBM models by introducing the heterozygous TPM in human induced pluripotent stem cells (hiPSCs) using a two-step targeting approach in the context of GBM genetic alterations, CDKN2A/B and PTEN deletion, and EGFRvIII overexpression. The impact of the mutation was evaluated through the in vivo passage and in vitro experiment and analysis. RESULTS: Orthotopic injection of neuronal precursor cells (NPCs) derived from hiPSCs with the TPM into immunodeficient mice did not enhance tumorigenesis compared to TERT promoter wild type NPCs at initial in vivo passage presumably due to relatively long telomeres. However, the mutation recruited GA-Binding Protein and engendered low-level TERT expression resulting in enhanced tumorigenesis and maintenance of short telomeres upon secondary passage as observed in human GBM. These results provide the first insights regarding increased tumorigenesis upon introducing a TPM compared to isogenic controls without TPMs. CONCLUSION: Our novel GBM models presented the growth advantage of heterozygous TPMs for the first time in the context of GBM driver mutations relative to isogenic controls, thereby allowing for the identification and validation of TERT promoter-specific vulnerabilities in a genetically accurate background.

High Dose Radiosurgery Targeting the Primary Tumor Sites Contributes to Survival in Patients With Skull Base Chordoma.

PURPOSE: Skull base chordoma (SBC) is a rare, aggressive bone tumor and a challenging therapeutic target. The efficacy of stereotactic radiosurgery (SRS) for SBC remains unclear. We aimed to elucidate therapeutic factors for favorable outcomes and establish a novel therapeutic approach for SBC. METHODS AND MATERIALS: This single-center retrospective study examined 47 SBCs treated with SRS. Treatment factors affecting local control rates (LCRs), remote control rates (RCRs), and overall survival (OS) were evaluated. Initially, we applied "localized-field SRS," wherein the irradiated volume accurately included recurrent/residual tumors on the radiographic images. Since 2015, we systematically applied "extended-field SRS," wherein the irradiated volume included the tumor location on the radiographic images and the preoperative tumor location with 2-mm margins. RESULTS: Tumor progression was observed in 23 SBCs (49%) after SRS. Higher marginal doses ≥20 Gy resulted in a higher LCR than lower-dose treatments (92% at 2 years and 73% at 5 years vs 43% at 2 years and 21% at 3 years, P = .001). Twenty-four patients underwent extended-field SRS, and 23 underwent localized-field SRS. While the LCRs were not significantly different, extended-field SRS improved RCRs (extended-field SRS: 100% vs localized-field SRS: 46% at 5 years; P = .001) without radiation-induced adverse events. Multivariate analysis demonstrated that extended-field SRS was associated with better RCRs (P = .001) and OS (P = .001). CONCLUSIONS: Extended-field SRS achieved LCRs comparable to previous studies and excellent OS without increasing the risk of radiation-induced adverse events.

Narcissistic Self-Sorting of Amphiphilic Collagen-Inspired Peptides in Supramolecular Vesicular Assembly.

Herein, we describe the hierarchical self-assembly accompanying self-sorting of collagen-inspired peptides (CPs). The two amphiphilic CPs used in this study contained an azobenzene (Az) moiety at the N-terminal, connected through a flexible spacer, but with different lengths of the (Gly-Pro-Hyp)n triplet (n = 5 and 7). When the CP aqueous solution (60 °C) was cooled to 4 °C, both CPs formed a triple helix structure and the pre-organized helices subsequently self-assembled into highly ordered vesicles with a diameter of 50-200 nm. Interestingly, narcissistic self-sorting was observed in both triple helix- and matured vesicle-formation processes, when the two CPs were mixed. Owing to the difference in the propensity for triple helix formation with temperature, the two CPs discriminate each other in response to a temperature change and form two kinds of triple helix foldamers, each containing a single component. The resulting differences in the amphiphilic balance and molecular length between the foldamers appear to allow individual self-sorting to form distinct vesicles. Furthermore, such vesicular assemblies were found to disassemble upon UV irradiation via trans-cis isomerization of the Az-groups. These findings offer important insights into the design of new complex but ordered, peptide self-assembly systems with potential applications in nanobiotechnology.

Targeting glioblastoma signaling and metabolism with a re-purposed brain-penetrant drug.

The highly lethal brain cancer glioblastoma (GBM) poses a daunting challenge because the blood-brain barrier renders potentially druggable amplified or mutated oncoproteins relatively inaccessible. Here, we identify sphingomyelin phosphodiesterase 1 (SMPD1), an enzyme that regulates the conversion of sphingomyelin to ceramide, as an actionable drug target in GBM. We show that the highly brain-penetrant antidepressant fluoxetine potently inhibits SMPD1 activity, killing GBMs, through inhibition of epidermal growth factor receptor (EGFR) signaling and via activation of lysosomal stress. Combining fluoxetine with temozolomide, a standard of care for GBM, causes massive increases in GBM cell death and complete tumor regression in mice. Incorporation of real-world evidence from electronic medical records from insurance databases reveals significantly increased survival in GBM patients treated with fluoxetine, which was not seen in patients treated with other selective serotonin reuptake inhibitor (SSRI) antidepressants. These results nominate the repurposing of fluoxetine as a potentially safe and promising therapy for patients with GBM and suggest prospective randomized clinical trials.

Supramolecular Nanofibers from Collagen-Mimetic Peptides Bearing Various Aromatic Groups at N-Termini via Hierarchical Self-Assembly.

Self-assembly of artificial peptides has been widely studied for constructing nanostructured materials, with numerous potential applications in the nanobiotechnology field. Herein, we report the synthesis and hierarchical self-assembly of collagen-mimetic peptides (CMPs) bearing various aromatic groups at the N-termini, including 2-naphthyl, 1-naphtyl, anthracenyl, and pyrenyl groups, into nanofibers. The CMPs (R-(GPO)n: n > 4) formed a triple helix structure in water at 4 °C, as confirmed via CD analyses, and their conformations were more stable with increasing hydrophobicity of the terminal aromatic group and peptide chain length. The resulting pre-organized triple helical CMPs showed diverse self-assembly into highly ordered nanofibers, reflecting their slight differences in hydrophobic/hydrophilic balance and configuration of aromatic templates. TEM analysis demonstrated that 2Np-CMPn (n = 6 and 7) and Py-CMP6 provided well-developed natural collagen-like nanofibers and An-CMPn (n = 5-7) self-assembled into rod-like micelle fibers. On the other hand, 2Np-CMP5 and 1Np-CMP6 were unable to form nanofibers under the same conditions. Furthermore, the Py-CMP6 nanofiber was found to encapsulate a guest hydrophobic molecule, Nile red, and exhibited unique emission behavior based on the specific nanostructure. In addition to the ability of CMPs to bind small molecules, their controlled self-assembly enables their versatile utilization in drug delivery and wavelength-conversion nanomaterials.

PI3Kγ inhibition suppresses microglia/TAM accumulation in glioblastoma microenvironment to promote exceptional temozolomide response.

Precision medicine in oncology leverages clinical observations of exceptional response. Toward an understanding of the molecular features that define this response, we applied an integrated, multiplatform analysis of RNA profiles derived from clinically annotated glioblastoma samples. This analysis suggested that specimens from exceptional responders are characterized by decreased accumulation of microglia/macrophages in the glioblastoma microenvironment. Glioblastoma-associated microglia/macrophages secreted interleukin 11 (IL11) to activate STAT3-MYC signaling in glioblastoma cells. This signaling induced stem cell states that confer enhanced tumorigenicity and resistance to the standard-of-care chemotherapy, temozolomide (TMZ). Targeting a myeloid cell restricted an isoform of phosphoinositide-3-kinase, phosphoinositide-3-kinase gamma isoform (PI3Kγ), by pharmacologic inhibition or genetic inactivation disrupted this signaling axis by reducing microglia/macrophage-associated IL11 secretion in the tumor microenvironment. Mirroring the clinical outcomes of exceptional responders, PI3Kγ inhibition synergistically enhanced the anti-neoplastic effects of TMZ in orthotopic murine glioblastoma models. Moreover, inhibition or genetic inactivation of PI3Kγ in murine glioblastoma models recapitulated expression profiles observed in clinical specimens isolated from exceptional responders. Our results suggest key contributions from tumor-associated microglia/macrophages in exceptional responses and highlight the translational potential for PI3Kγ inhibition as a glioblastoma therapy.

PTEN deficiency leads to proteasome addiction: a novel vulnerability in glioblastoma.

BACKGROUND: Glioblastoma (GBM) is the most common primary brain tumor in adults with a median survival of approximately 15 months; therefore, more effective treatment options for GBM are required. To identify new drugs targeting GBMs, we performed a high-throughput drug screen using patient-derived neurospheres cultured to preferentially retain their glioblastoma stem cell (GSC) phenotype. METHODS: High-throughput drug screening was performed on GSCs followed by a dose-response assay of the 5 identified original "hits." A PI3K/mTOR dependency to a proteasome inhibitor (carfilzomib), was confirmed by genetic and pharmacologic experiments. Proteasome Inhibition Response Signatures were derived from proteomic and bioinformatic analysis. Molecular mechanism of action was determined using three-dimensional (3D) GBM-organoids and preclinical orthotopic models. RESULTS: We found that GSCs were highly sensitive to proteasome inhibition due to an underlying dependency on an increased protein synthesis rate, and loss of autophagy, associated with PTEN loss and activation of the PI3K/mTOR pathway. In contrast, combinatory inhibition of autophagy and the proteasome resulted in enhanced cytotoxicity specifically in GSCs that did express PTEN. Finally, proteasome inhibition specifically increased cell death markers in 3D GBM-organoids, suppressed tumor growth, and increased survival of mice orthotopically engrafted with GSCs. As perturbations of the PI3K/mTOR pathway occur in nearly 50% of GBMs, these findings suggest that a significant fraction of these tumors could be vulnerable to proteasome inhibition. CONCLUSIONS: Proteasome inhibition is a potential synthetic lethal therapeutic strategy for GBM with proteasome addiction due to a high protein synthesis rate and autophagy deficiency.

Epidermal growth factor receptor as a molecular determinant of glioblastoma response to dopamine receptor D2 inhibitors.

BACKGROUND: There are ongoing clinical trials exploring the efficacy of dopamine receptor D2 (DRD2) inhibition against glioblastomas, the most common primary brain tumor. Here we examine potential molecular determinants of this efficacy. METHODS: The Cancer Genome Atlas glioblastoma database and other published mRNA profiles were used to analyze the DRD2 and epidermal growth factor receptor (EGFR) expression pattern. In vitro and in vivo responses to DRD2 inhibitors were determined using patient-derived xenograft (PDX) glioblastoma models. Immunohistochemical studies were performed on clinically annotated glioblastoma samples derived from patients treated with ONC201. RESULTS: Analysis of clinical glioblastoma specimens derived from independent patient cohorts revealed an inverse correlation between EGFR and DRD2 mRNA expression, with implication that signaling mediated by these proteins shares overlapping functions. In independent panels of PDX glioblastoma lines, high EGFR expression was associated with poor in vitro and in vivo response to DRD2 inhibitors, including haloperidol and ONC201. Moreover, ectopic expression of a constitutively active EGFR, variant (v)III, suppressed glioblastoma sensitivity to ONC201. DRD2 expression positively correlated with expression of rate-limiting enzymes for dopamine synthesis as well as dopamine secretion, suggesting contribution of autocrine DRD2 signaling. Analysis of specimens from patients treated with ONC201 (n = 15) showed an inverse correlation between the intensity of EGFR staining and clinical response. The median overall survival for patients with high and low EGFR staining was 162 and 373 days, respectively (0.037). CONCLUSIONS: High EGFR expression is a determinant of poor glioblastoma response to DRD2. This finding should inform future clinical trial designs.