Hypoxia-inducible factor 1 recruits FACT and RNF20/40 to mediate histone ubiquitination and transcriptional activation of target genes.

Hypoxia-inducible factor 1 (HIF-1) is a transcriptional activator that mediates cellular adaptation to decreased oxygen availability. HIF-1 recruits chromatin-modifying enzymes leading to changes in histone acetylation, citrullination, and methylation at target genes. Here, we demonstrate that hypoxia-inducible gene expression in estrogen receptor (ER)-positive MCF7 and ER-negative SUM159 human breast cancer cells requires the histone H2A/H2B chaperone facilitates chromatin transcription (FACT) and the H2B ubiquitin ligase RING finger protein 20/40 (RNF20/40). Knockdown of FACT or RNF20/40 expression leads to decreased transcription initiation and elongation at HIF-1 target genes. Mechanistically, FACT and RNF20/40 are recruited to hypoxia response elements (HREs) by HIF-1 and stabilize binding of HIF-1 (and each other) at HREs. Hypoxia induces the monoubiquitination of histone H2B at lysine 120 at HIF-1 target genes in an HIF-1-dependent manner. Together, these findings delineate a cooperative molecular mechanism by which FACT and RNF20/40 stabilize multiprotein complex formation at HREs and mediate histone ubiquitination to facilitate HIF-1 transcriptional activity.

Plexin-B3 expression stimulates MET signaling, breast cancer stem cell specification, and lung metastasis.

Intratumoral hypoxia is a microenvironmental feature that promotes breast cancer progression and is associated with cancer mortality. Plexin B3 (PLXNB3) is highly expressed in estrogen receptor-negative breast cancer, but the underlying mechanisms and consequences have not been thoroughly investigated. Here, we report that PLXNB3 expression is increased in response to hypoxia and that PLXNB3 is a direct target gene of hypoxia-inducible factor 1 (HIF-1) in human breast cancer cells. PLXNB3 expression is correlated with HIF-1α immunohistochemistry, breast cancer grade and stage, and patient mortality. Mechanistically, PLXNB3 is required for hypoxia-induced MET/SRC/focal adhesion kinase (FAK) and MET/SRC/STAT3/NANOG signaling as well as hypoxia-induced breast cancer cell migration, invasion, and cancer stem cell specification. PLXNB3 knockdown impairs tumor formation and lung metastasis in orthotopic breast cancer mouse models.

Recruitment of women in neurosurgery: a 7-year quantitative analysis.

OBJECTIVE: The authors aimed to characterize which US medical schools have the most female neurosurgery residents and to identify potential associations between medical school characteristics and successful recruitment of women pursuing a neurosurgery career. METHODS: The authors evaluated a total of 1572 residents in US neurosurgery programs accredited by the Accreditation Council for Graduate Medical Education as of February 2021, representing match cohorts from 2014 to 2020. The authors extracted US medical school characteristics and ranked schools based on the percentages of women graduates entering neurosurgery. They additionally studied yearly trends of the percentage of women constituting incoming neurosurgery resident cohorts as well as associations between female recruitment percentage and medical school characteristics using univariable and stepwise multivariable linear regression (including significant univariable factors). RESULTS: The cohort consisted of 1255 male and 317 (20%) female residents. Yearly trends indicated a significant drop in incoming female residents in 2016, followed by significant increases in 2017 and 2019. On multivariable analysis, the following factors were associated with a higher average percentage of female graduates entering neurosurgery: total affiliated neurosurgery clinical faculty (ß = 0.006, 95% CI 0.001-0.011, p = 0.01), allopathic versus osteopathic schools (ß = 0.231, 95% CI 0.053-0.409, p = 0.01), and top 10 U.S. News & World Report ranking (ß = 0.380, 95% CI 0.129-0.589, p < 0.01). When the number of female clinical faculty was added to the model, the variable was not statistically significant. Multivariable bibliometric analyses indicated a higher mean preresidency H-index for men, with an even greater gender difference identified in the 2021 H-index. CONCLUSIONS: This study characterizes which medical schools are most successful at recruiting female students who constituted the total neurosurgery resident workforce of the 2020-2021 academic year. The overall number of clinical neurosurgery faculty rather than faculty gender was independently associated with female recruitment. Gender differences in research productivity persisted with control for confounders and increased between preresidency and 2021 time points. Such understanding of factors that influence the recruitment of women can help improve female representation in neurosurgery residency training moving forward.

NARF is a hypoxia-induced coactivator for OCT4-mediated breast cancer stem cell specification.

Hypoxia is a key characteristic of the breast cancer microenvironment that promotes expression of the transcriptional activator hypoxia-inducible factor 1 (HIF-1) and is associated with poor patient outcome. HIF-1 increases the expression or activity of stem cell pluripotency factors, which control breast cancer stem cell (BCSC) specification and are required for cancer metastasis. Here, we identify nuclear prelamin A recognition factor (NARF) as a hypoxia-inducible, HIF-1 target gene in human breast cancer cells. NARF functions as an essential coactivator by recruiting the histone demethylase KDM6A to OCT4 bound to genes encoding the pluripotency factors NANOG, KLF4, and SOX2, leading to demethylation of histone H3 trimethylated at lysine-27 (H3K27me3), thereby increasing the expression of NANOG, KLF4, and SOX2, which, together with OCT4, mediate BCSC specification. Knockdown of NARF significantly decreased the BCSC population in vitro and markedly impaired tumor initiation capacity and lung metastasis in orthotopic mouse models.

Polymeric Nanoparticles in Brain Cancer Therapy: A Review of Current Approaches.

Translation of novel therapies for brain cancer into clinical practice is of the utmost importance as primary brain tumors are responsible for more than 200,000 deaths worldwide each year. While many research efforts have been aimed at improving survival rates over the years, prognosis for patients with glioblastoma and other primary brain tumors remains poor. Safely delivering chemotherapeutic drugs and other anti-cancer compounds across the blood-brain barrier and directly to tumor cells is perhaps the greatest challenge in treating brain cancer. Polymeric nanoparticles (NPs) are powerful, highly tunable carrier systems that may be able to overcome those obstacles. Several studies have shown appropriately-constructed polymeric NPs cross the blood-brain barrier, increase drug bioavailability, reduce systemic toxicity, and selectively target central nervous system cancer cells. While no studies relating to their use in treating brain cancer are in clinical trials, there is mounting preclinical evidence that polymeric NPs could be beneficial for brain tumor therapy. This review includes a variety of polymeric NPs and how their associated composition, surface modifications, and method of delivery impact their capacity to improve brain tumor therapy.

The Translational Potential of Microglia and Monocyte-Derived Macrophages in Ischemic Stroke.

The immune response to ischemic stroke is an area of study that is at the forefront of stroke research and presents promising new avenues for treatment development. Upon cerebral vessel occlusion, the innate immune system is activated by danger-associated molecular signals from stressed and dying neurons. Microglia, an immune cell population within the central nervous system which phagocytose cell debris and modulate the immune response via cytokine signaling, are the first cell population to become activated. Soon after, monocytes arrive from the peripheral immune system, differentiate into macrophages, and further aid in the immune response. Upon activation, both microglia and monocyte-derived macrophages are capable of polarizing into phenotypes which can either promote or attenuate the inflammatory response. Phenotypes which promote the inflammatory response are hypothesized to increase neuronal damage and impair recovery of neuronal function during the later phases of ischemic stroke. Therefore, modulating neuroimmune cells to adopt an anti-inflammatory response post ischemic stroke is an area of current research interest and potential treatment development. In this review, we outline the biology of microglia and monocyte-derived macrophages, further explain their roles in the acute, subacute, and chronic stages of ischemic stroke, and highlight current treatment development efforts which target these cells in the context of ischemic stroke.

Hypoxia-inducible factors: cancer progression and clinical translation.

Hypoxia-inducible factors (HIFs) are master regulators of oxygen homeostasis that match O2 supply and demand for each of the 50 trillion cells in the adult human body. Cancer cells co-opt this homeostatic system to drive cancer progression. HIFs activate the transcription of thousands of genes that mediate angiogenesis, cancer stem cell specification, cell motility, epithelial-mesenchymal transition, extracellular matrix remodeling, glucose and lipid metabolism, immune evasion, invasion, and metastasis. In this Review, the mechanisms and consequences of HIF activation in cancer cells are presented. The current status and future prospects of small-molecule HIF inhibitors for use as cancer therapeutics are discussed.

Home Program Matching in Neurosurgical Residency Programs: A 7-Year Study.

OBJECTIVE: The objective of the study was to determine home program matching percentage (staying in a program affiliated with one's medical school) for each neurosurgical residency program in the United States. Secondarily, it was to elucidate both program-level and resident characteristics associated with home program matching. METHODS: Demographic and bibliometric characteristics were collected for 1572 residents in U.S.-based and Accreditation Council for Graduate Medical Education-accredited neurosurgery programs over the 2014-2020 match period using publicly available websites. Program characteristics were collected, including number of clinical faculty, top 20 Doximity research ranking, top 10 Doximity reputation ranking, top 10 U.S. News department ranking, affiliation with a U.S. News top 10 medical school, and geographic region. Programs were ranked according to home program matching percentage, and associations were statistically evaluated. RESULTS: The average home program matching percentage per residency was 18.6%. NewYork-Presbyterian/Columbia retained the largest percentage of its own medical students with a home program matching percentage of 57.14%. From the resident frame of reference, only a higher preresidency H-index (3.7 ± 4.0 vs. 3.2 ± 3.7, P = 0.033) was significantly associated with home program matching. From a program perspective, program size (standardized ß = 0.234, P = 0.006), Doximity research (standardized ß = 0.206, P = 0.031), Doximity reputation (standardized ß = 0.196, P = 0.040), and U.S. News program rankings (standardized ß = 0.200, P = 0.036) were all significantly associated with home program matching. Overall home program matching percentage remained relatively constant over the 2014-2020 time period. CONCLUSIONS: The results of this study delineate home program matching patterns on a program-by-program level for U.S. neurosurgical residency programs.

HIF inhibitor 32-134D eradicates murine hepatocellular carcinoma in combination with anti-PD1 therapy.

Hepatocellular carcinoma (HCC) is a major cause of cancer mortality worldwide and available therapies, including immunotherapies, are ineffective for many patients. HCC is characterized by intratumoral hypoxia, and increased expression of hypoxia-inducible factor 1α (HIF-1α) in diagnostic biopsies is associated with patient mortality. Here we report the development of 32-134D, a low-molecular-weight compound that effectively inhibits gene expression mediated by HIF-1 and HIF-2 in HCC cells, and blocks human and mouse HCC tumor growth. In immunocompetent mice bearing Hepa1-6 HCC tumors, addition of 32-134D to anti-PD1 therapy increased the rate of tumor eradication from 25% to 67%. Treated mice showed no changes in appearance, behavior, body weight, hemoglobin, or hematocrit. Compound 32-134D altered the expression of a large battery of genes encoding proteins that mediate angiogenesis, glycolytic metabolism, and responses to innate and adaptive immunity. This altered gene expression led to significant changes in the tumor immune microenvironment, including a decreased percentage of tumor-associated macrophages and myeloid-derived suppressor cells, which mediate immune evasion, and an increased percentage of CD8+ T cells and natural killer cells, which mediate antitumor immunity. Taken together, these preclinical findings suggest that combining 32-134D with immune checkpoint blockade may represent a breakthrough therapy for HCC.

External Validation of a Neural Network Model in Aneurysmal Subarachnoid Hemorrhage: A Comparison With Conventional Logistic Regression Models.

BACKGROUND: Interest in machine learning (ML)-based predictive modeling has led to the development of models predicting outcomes after aneurysmal subarachnoid hemorrhage (aSAH), including the Nijmegen acute subarachnoid hemorrhage calculator (Nutshell). Generalizability of such models to external data remains unclear. OBJECTIVE: To externally validate the performance of the Nutshell tool while comparing it with the conventional Subarachnoid Hemorrhage International Trialists (SAHIT) models and to review the ML literature on outcome prediction after aSAH and aneurysm treatment. METHODS: A prospectively maintained database of patients with aSAH presenting consecutively to our institution in the 2013 to 2018 period was used. The web-based Nutshell and SAHIT calculators were used to derive the risks of poor long-term (12-18 months) outcomes and 30-day mortality. Discrimination was evaluated using the area under the curve (AUC), and calibration was investigated using calibration plots. The literature on relevant ML models was surveyed for a synopsis. RESULTS: In 269 patients with aSAH, the SAHIT models outperformed the Nutshell tool (AUC: 0.786 vs 0.689, P = .025) in predicting long-term functional outcomes. A logistic regression model of the Nutshell variables derived from our data achieved adequate discrimination (AUC = 0.759) of poor outcomes. The SAHIT models outperformed the Nutshell tool in predicting 30-day mortality (AUC: 0.810 vs 0.636, P < .001). Calibration properties were more favorable for the SAHIT models. Most published aneurysm-related ML-based outcome models lack external validation and usable testing platforms. CONCLUSION: The Nutshell tool demonstrated limited performance on external validation in comparison with the SAHIT models. External validation and the dissemination of testing platforms for ML models must be emphasized.

Which medical schools produce the most neurosurgery residents? An analysis of the 2014-2020 cohort.

OBJECTIVE: In this study, the authors sought to determine which US medical schools have produced the most neurosurgery residents and to evaluate potential associations between recruitment and medical school characteristics. METHODS: Demographic and bibliometric characteristics were collected for 1572 residents in US-based and Accreditation Council for Graduate Medical Education (ACGME)-accredited neurosurgery programs over the 2014 to 2020 match period using publicly available websites. US medical school characteristics were collected, including class size, presence of a home neurosurgery program, number of clinical neurosurgery faculty, research funding, presence of a neurosurgery interest group, and a top 10 ranking via U.S. News & World Report or Doximity. Correlations and associations were then evaluated using Pearson's correlation coefficient (PCC), independent-samples t-test, and univariable or stepwise multivariable linear regression, as appropriate. RESULTS: Vanderbilt University produced the most neurosurgery residents as a percentage of medical graduates at 3.799%. Case Western Reserve University produced the greatest absolute number of neurosurgery residents (n = 40). The following factors were shown to be associated with a higher mean percentage of graduates entering neurosurgery: number of clinical neurosurgery faculty (PCC 0.509, p < 0.001), presence of a neurosurgery interest group (1.022% ± 0.737% vs 0.351% ± 0.327%, p < 0.001) or home neurosurgery program (1.169% ± 0.766% vs 0.428% ± 0.327%, p < 0.001), allopathic compared with osteopathic school (0.976% ± 0.719% vs 0.232% ± 0.272%, p < 0.001), U.S. News top 10 ranking for neurology and neurosurgery (1.923% ± 0.924% vs 0.757% ± 0.607%, p < 0.001), Doximity top 10 residency program ranking (1.715% ± 0.803% vs 0.814% ± 0.688%, p < 0.001), and amount of NIH funding (PCC 0.528, p < 0.001). CONCLUSIONS: The results of this study have delineated which medical schools produced the most neurosurgery residents currently in training, and the most important independent factors predicting the percentage of graduates entering neurosurgery and the preresidency h-index.

Author Correction: Multicellular 3D Neurovascular Unit Model for Assessing Hypoxia and Neuroinflammation Induced Blood-Brain Barrier Dysfunction.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Multicellular 3D Neurovascular Unit Model for Assessing Hypoxia and Neuroinflammation Induced Blood-Brain Barrier Dysfunction.

The blood-brain barrier (BBB) is a dynamic component of the brain-vascular interface that maintains brain homeostasis and regulates solute permeability into brain tissue. The expression of tight junction proteins between adjacent endothelial cells and the presence of efflux proteins prevents entry of foreign substances into the brain parenchyma. BBB dysfunction, however, is evident in many neurological disorders including ischemic stroke, trauma, and chronic neurodegenerative diseases. Currently, major contributors to BBB dysfunction are not well understood. Here, we employed a multicellular 3D neurovascular unit organoid containing human brain microvascular endothelial cells, pericytes, astrocytes, microglia, oligodendrocytes and neurons to model the effects of hypoxia and neuroinflammation on BBB function. Organoids were cultured in hypoxic chamber with 0.1% O2 for 24 hours. Organoids cultured under this hypoxic condition showed increased permeability, pro-inflammatory cytokine production, and increased oxidative stress. The anti-inflammatory agents, secoisolariciresinol diglucoside and 2-arachidonoyl glycerol, demonstrated protection by reducing inflammatory cytokine levels in the organoids under hypoxic conditions. Through the assessment of a free radical scavenger and an anti-inflammatory endocannabinoid, we hereby report the utility of the model in drug development for drug candidates that may reduce the effects of ROS and inflammation under disease conditions. This 3D organoid model recapitulates characteristics of BBB dysfunction under hypoxic physiological conditions and when exposed to exogenous neuroinflammatory mediators and hence may have potential in disease modeling and therapeutic development.