Clonal ZEB1-driven mesenchymal transition promotes targetable oncologic anti-angiogenic therapy resistance.
Glioblastoma responses to bevacizumab are invariably transient with acquired resistance. We profiled paired patient specimens and bevacizumab-resistant xenograft models pre- and post-resistance towards the primary goal of identifying regulators whose targeting could prolong the therapeutic window, and the secondary goal of identifying biomarkers of therapeutic window closure. Bevacizumab-resistant patient specimens and xenografts exhibited decreased vessel density and increased hypoxia versus pre-resistance, suggesting that resistance occurs despite effective therapeutic devascularization. Microarray analysis revealed upregulated mesenchymal genes in resistant tumors correlating with bevacizumab treatment duration and causing three changes enabling resistant tumor growth in hypoxia. First, perivascular invasiveness along remaining blood vessels, which co-opts vessels in a VEGF-independent and neo-angiogenesis-independent manner, was upregulated in novel biomimetic 3D bioengineered platforms modeling the bevacizumab-resistant microenvironment. Second, tumor-initiating stem cells housed in the perivascular niche close to remaining blood vessels were enriched. Third, metabolic reprogramming assessed through real-time bioenergetic measurement and metabolomics upregulated glycolysis and suppressed oxidative phosphorylation. Single-cell sequencing of bevacizumab-resistant patient glioblastomas confirmed upregulated mesenchymal genes, particularly glycoprotein YKL-40 and transcription factor ZEB1, in later clones, implicating these changes as treatment-induced. Serum YKL-40 was elevated in bevacizumab-resistant vs. bevacizumab-naïve patients. CRISPR and pharmacologic targeting of ZEB1 with honokiol reversed the mesenchymal gene expression and associated stem cell, invasion, and metabolic changes defining resistance. Honokiol caused greater cell death in bevacizumab-resistant than bevacizumab-responsive tumor cells, with surviving cells losing mesenchymal morphology. Employing YKL-40 as a resistance biomarker and ZEB1 as a target to prevent resistance could fulfill the promise of anti-angiogenic therapy.
View details for DOI 10.1158/0008-5472.CAN-19-1305
View details for PubMedID 32041837
The phenotypes of proliferating glioblastoma cells reside on a single axis of variation.
Although tumor-propagating cells can be derived from glioblastomas (GBMs) of the proneural and mesenchymal subtypes, a glioma stem-like cell (GSC) of the classical subtype has not been identified. It is unclear if mesenchymal GSCs (mGSCs) and/or proneural GSCs (pGSCs) alone are sufficient to generate the heterogeneity observed in GBM. We performed single-cell/nuclei RNA-sequencing of 28 gliomas, and single-cell ATAC-sequencing for 8 cases. We find that GBM GSCs reside on a single axis of variation, ranging from proneural to mesenchymal. In silico lineage tracing using both transcriptomics and genetics supports mGSCs as the progenitors of pGSCs. Dual inhibition of pGSC-enriched and mGSC-enriched growth and survival pathways provides a more complete treatment than combinations targeting one GSC phenotype alone. This study sheds light on a long-standing debate regarding lineage relationships among GSCs and presents a paradigm by which personalized combination therapies can be derived from single-cell RNA signatures, to overcome intra-tumor heterogeneity.
View details for DOI 10.1158/2159-8290.CD-19-0329
View details for PubMedID 31554641
The neurosurgery applicant's "arms race": analysis of medical student publication in the Neurosurgery Residency Match.
Journal of neurosurgery
Neurosurgery is consistently one of the most competitive specialties for resident applicants. The emphasis on research in neurosurgery has led to an increasing number of publications by applicants seeking a successful residency match. The authors sought to produce a comprehensive analysis of research produced by neurosurgical applicants and to establish baseline data of neurosurgery applicant research productivity given the increased emphasis on research output for successful residency match.A retrospective review of publication volume for all neurosurgery interns in 2009, 2011, 2014, 2016, and 2018 was performed using PubMed and Google Scholar. Missing data rates were 11% (2009), 9% (2011), and < 5% (all others). The National Resident Matching Program report "Charting Outcomes in the Match" (ChOM) was interrogated for total research products (i.e., abstracts, presentations, and publications). The publication rates of interns at top 40 programs, students from top 20 medical schools, MD/PhD applicants, and applicants based on location of residency program and medical school were compared statistically against all others.Total publications per neurosurgery intern (mean ± SD) based on PubMed and Google Scholar were 5.5 ± 0.6 in 2018 (1.7 ± 0.3, 2009; 2.1 ± 0.3, 2011; 2.6 ± 0.4, 2014; 3.8 ± 0.4, 2016), compared to 18.3 research products based on ChOM. In 2018, the mean numbers of publications were as follows: neurosurgery-specific publications per intern, 4.3 ± 0.6; first/last author publications, 2.1 ± 0.3; neurosurgical first/last author publications, 1.6 ± 0.2; basic science publications, 1.5 ± 0.2; and clinical research publications, 4.0 ± 0.5. Mean publication numbers among interns at top 40 programs were significantly higher than those of all other programs in every category (p < 0.001). Except for mean number of basic science publications (p = 0.1), the mean number of publications was higher for interns who attended a top 20 medical school than for those who did not (p < 0.05). Applicants with PhD degrees produced statistically more research in all categories (p < 0.05) except neurosurgery-specific (p = 0.07) and clinical research (p = 0.3). While there was no statistical difference in publication volume based on the geographical location of the residency program, students from medical schools in the Western US produced more research than all other regions (p < 0.01). Finally, research productivity did not correlate with likelihood of medical students staying at their home institution for residency.The authors found that the temporal trend toward increased total research products over time in neurosurgery applicants was driven mostly by increased nonindexed research (abstracts, presentations, chapters) rather than by increased peer-reviewed publications. While we also identified applicant-specific factors (MD/PhDs and applicants from the Western US) and an outcome (matching at research-focused institutions) associated with increased applicant publications, further work will be needed to determine the emphasis that programs and applicants will need to place on these publications.
View details for DOI 10.3171/2019.8.JNS191256
View details for PubMedID 31675693
Insurance type impacts the economic burden and survival of patients with newly diagnosed glioblastoma.
Journal of neurosurgery
Glioblastoma (GBM) carries a high economic burden for patients and caregivers, much of which is associated with initial surgery. The authors investigated the impact of insurance status on the inpatient hospital costs of surgery for patients with GBM.The authors conducted a retrospective review of patients with GBM (2010-2015) undergoing their first resection at the University of California, San Francisco, and corresponding inpatient hospital costs.Of 227 patients with GBM (median age 62 years, 37.9% females), 31 (13.7%) had Medicaid, 94 (41.4%) had Medicare, and 102 (44.9%) had private insurance. Medicaid patients had 30% higher overall hospital costs for surgery compared to non-Medicaid patients ($50,285 vs $38,779, p = 0.01). Medicaid patients had higher intensive care unit (ICU; p < 0.01), operating room (p < 0.03), imaging (p < 0.001), room and board (p < 0001), and pharmacy (p < 0.02) costs versus non-Medicaid patients. Medicaid patients had significantly longer overall and ICU lengths of stay (6.9 and 2.6 days) versus Medicare (4.0 and 1.5 days) and privately insured patients (3.9 and 1.8 days, p < 0.01). Medicaid patients had similar comorbidity rates to Medicare patients (67.8% vs 68.1%), and both groups had higher comorbidity rates than privately insured patients (37.3%, p < 0.0001). Only 67.7% of Medicaid patients had primary care providers (PCPs) versus 91.5% of Medicare and 86.3% of privately insured patients (p = 0.009) at the time of presentation. Tumor diameter at diagnosis was largest for Medicaid (4.7 cm) versus Medicare (4.1 cm) and privately insured patients (4.2 cm, p = 0.03). Preoperative (70 vs 90, p = 0.02) and postoperative (80 vs 90, p = 0.03) Karnofsky Performance Scale (KPS) scores were lowest for Medicaid versus non-Medicaid patients, while in subgroup analysis, postoperative KPS score was lowest for Medicaid patients (80, vs 90 for Medicare and 90 for private insurance; p = 0.03). Medicaid patients had significantly shorter median overall survival (10.7 months vs 12.8 months for Medicare and 15.8 months for private insurance; p = 0.02). Quality-adjusted life year (QALY) scores were 0.66 and 1.05 for Medicaid and non-Medicaid patients, respectively (p = 0.036). The incremental cost per QALY was $29,963 lower for the non-Medicaid cohort.Patients with GBMs and Medicaid have higher surgical costs, longer lengths of stay, poorer survival, and lower QALY scores. This study indicates that these patients lack PCPs, have more comorbidities, and present later in the disease course with larger tumors; these factors may drive the poorer postoperative function and greater consumption of hospital resources that were identified. Given limited resources and rising healthcare costs, factors such as access to PCPs, equitable adjuvant therapy, and early screening/diagnosis of disease need to be improved in order to improve prognosis and reduce hospital costs for patients with GBM.
View details for DOI 10.3171/2019.3.JNS182629
View details for PubMedID 31226687
Stress Granule Assembly Disrupts Nucleocytoplasmic Transport
2018; 173 (4): 958-+
Defects in nucleocytoplasmic transport have been identified as a key pathogenic event in amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) mediated by a GGGGCC hexanucleotide repeat expansion in C9ORF72, the most common genetic cause of ALS/FTD. Furthermore, nucleocytoplasmic transport disruption has also been implicated in other neurodegenerative diseases with protein aggregation, suggesting a shared mechanism by which protein stress disrupts nucleocytoplasmic transport. Here, we show that cellular stress disrupts nucleocytoplasmic transport by localizing critical nucleocytoplasmic transport factors into stress granules, RNA/protein complexes that play a crucial role in ALS pathogenesis. Importantly, inhibiting stress granule assembly, such as by knocking down Ataxin-2, suppresses nucleocytoplasmic transport defects as well as neurodegeneration in C9ORF72-mediated ALS/FTD. Our findings identify a link between stress granule assembly and nucleocytoplasmic transport, two fundamental cellular processes implicated in the pathogenesis of C9ORF72-mediated ALS/FTD and other neurodegenerative diseases.
View details for PubMedID 29628143
Mutant Huntingtin Disrupts the Nuclear Pore Complex
2017; 94 (1): 93-+
Huntington's disease (HD) is caused by an expanded CAG repeat in the Huntingtin (HTT) gene. The mechanism(s) by which mutant HTT (mHTT) causes disease is unclear. Nucleocytoplasmic transport, the trafficking of macromolecules between the nucleus and cytoplasm, is tightly regulated by nuclear pore complexes (NPCs) made up of nucleoporins (NUPs). Previous studies offered clues that mHTT may disrupt nucleocytoplasmic transport and a mutation of an NUP can cause HD-like pathology. Therefore, we evaluated the NPC and nucleocytoplasmic transport in multiple models of HD, including mouse and fly models, neurons transfected with mHTT, HD iPSC-derived neurons, and human HD brain regions. These studies revealed severe mislocalization and aggregation of NUPs and defective nucleocytoplasmic transport. HD repeat-associated non-ATG (RAN) translation proteins also disrupted nucleocytoplasmic transport. Additionally, overexpression of NUPs and treatment with drugs that prevent aberrant NUP biology also mitigated this transport defect and neurotoxicity, providing future novel therapy targets.
View details for DOI 10.1016/j.neuron.2017.03.023
View details for Web of Science ID 000398262000012
View details for PubMedID 28384479
View details for PubMedCentralID PMC5595097