Single-nucleus expression characterization of non-enhancing region of recurrent high-grade glioma.

Background: Non-enhancing (NE) infiltrating tumor cells beyond the contrast-enhancing (CE) bulk of tumor are potential propagators of recurrence after gross total resection of high-grade glioma. Methods: We leveraged single-nucleus RNA sequencing on 15 specimens from recurrent high-grade gliomas (n = 5) to compare prospectively identified biopsy specimens acquired from CE and NE regions. Additionally, 24 CE and 22 NE biopsies had immunohistochemical staining to validate RNA findings. Results: Tumor cells in NE regions are enriched in neural progenitor cell-like cellular states, while CE regions are enriched in mesenchymal-like states. NE glioma cells have similar proportions of proliferative and putative glioma stem cells relative to CE regions, without significant differences in % Ki-67 staining. Tumor cells in NE regions exhibit upregulation of genes previously associated with lower grade gliomas. Our findings in recurrent GBM paralleled some of the findings in a re-analysis of a dataset from primary GBM. Cell-, gene-, and pathway-level analyses of the tumor microenvironment in the NE region reveal relative downregulation of tumor-mediated neovascularization and cell-mediated immune response, but increased glioma-to-nonpathological cell interactions. Conclusions: This comprehensive analysis illustrates differing tumor and nontumor landscapes of CE and NE regions in high-grade gliomas, highlighting the NE region as an area harboring likely initiators of recurrence in a pro-tumor microenvironment and identifying possible targets for future design of NE-specific adjuvant therapy. These findings also support the aggressive approach to resection of tumor-bearing NE regions.

Low- and High-Grade Glioma-Associated Vascular Cells Differentially Regulate Tumor Growth.

A key feature distinguishing high-grade glioma (HG) from low-grade glioma (LG) is the extensive neovascularization and endothelial hyperproliferation. Prior work has shown that tumor-associated vasculature from HG is molecularly and functionally distinct from normal brain vasculature and expresses higher levels of protumorigenic factors that promote glioma growth and progression. However, it remains unclear whether vessels from LG also express protumorigenic factors, and to what extent they functionally contribute to glioma growth. Here, we profile the transcriptomes of glioma-associated vascular cells (GVC) from IDH-mutant (mIDH) LG and IDH-wild-type (wIDH) HG and show that they exhibit significant molecular and functional differences. LG-GVC show enrichment of extracellular matrix-related gene sets and sensitivity to antiangiogenic drugs, whereas HG-GVC display an increase in immune response-related gene sets and antiangiogenic resistance. Strikingly, conditioned media from LG-GVC inhibits the growth of wIDH glioblastoma cells, whereas HG-GVC promotes growth. In vivo cotransplantation of LG-GVC with tumor cells reduces growth, whereas HG-GVC enhances tumor growth in orthotopic xenografts. We identify ASPORIN (ASPN), a small leucine-rich repeat proteoglycan, highly enriched in LG-GVC as a growth suppressor of wIDH glioblastoma cells in vitro and in vivo. Together, these findings indicate that GVC from LG and HG are molecularly and functionally distinct and differentially regulate tumor growth. Implications: This study demonstrated that vascular cells from IDH-mutant LG and IDH-wild-type HG exhibit distinct molecular signatures and have differential effects on tumor growth via regulation of ASPN-TGFß1-GPM6A signaling.

pH-Weighted amine chemical exchange saturation transfer echo planar imaging visualizes infiltrating glioblastoma cells.

BACKGROUND: Given the invasive nature of glioblastoma, tumor cells exist beyond the contrast-enhancing (CE) region targeted during treatment. However, areas of non-enhancing (NE) tumors are difficult to visualize and delineate from edematous tissue. Amine chemical exchange saturation transfer echo planar imaging (CEST-EPI) is a pH-sensitive molecular magnetic resonance imaging technique that was evaluated in its ability to identify infiltrating NE tumors and prognosticate survival. METHODS: In this prospective study, CEST-EPI was obtained in 30 patients and areas with elevated CEST contrast ("CEST+" based on the asymmetry in magnetization transfer ratio: MTRasym at 3 ppm) within NE regions were quantitated. Median MTRasym at 3 ppm and volume of CEST + NE regions were correlated with progression-free survival (PFS). In 20 samples from 14 patients, image-guided biopsies of these areas were obtained to correlate MTRasym at 3 ppm to tumor and non-tumor cell burden using immunohistochemistry. RESULTS: In 15 newly diagnosed and 15 recurrent glioblastoma, higher median MTRasym at 3ppm within CEST + NE regions (P = .007; P = .0326) and higher volumes of CEST + NE tumor (P = .020; P < .001) were associated with decreased PFS. CE recurrence occurred in areas of preoperative CEST + NE regions in 95.4% of patients. MTRasym at 3 ppm was correlated with presence of tumor, cell density, %Ki-67 positivity, and %CD31 positivity (P = .001; P < .001; P < .001; P = .001). CONCLUSIONS: pH-weighted amine CEST-EPI allows for visualization of NE tumor, likely through surrounding acidification of the tumor microenvironment. The magnitude and volume of CEST + NE tumor correlates with tumor cell density, degree of proliferating or "active" tumor, and PFS.

Prevalencia de endometritis crónica en mujeres infértiles establecida mediante histeroscopia y biopsia endometrial con CD138 / Prevalence of chronic endometritis in infertile women by hysteroscopy and endometrial biopsy with CD138

Resumen OBJETIVO: Determinar, mediante histeroscopia de evaluación y biopsia de endometrio, con análisis histológico endometrial e identificación de células plasmáticas con inmunohisdtoquímica con CD138 positiva, la prevalencia de endometritis crónica en pacientes infértiles. MATERIALES Y MÉTODOS: Estudio observacional, retrospectivo, efectuado de marzo de 2016 a noviembre del 2021 en el Centro de Reproducción Asistida de Saltillo (CREAS), Coahuila, México, en pacientes que consultaron por infertilidad. El diagnóstico de endometritis crónica se estableció mediante histeroscopia y biopsia de endometrio con inmunohistoquímica CD138. Se analizaron la prevalencia y precisión diagnóstica de la histeroscopia y la biopsia de endometrio. Además, la relación entre las características histeroscópicas específicas y la endometritis crónica confirmada por biopsia con CD138 positiva. RESULTADOS: La prevalencia de endometritis crónica por biopsia de endometrio CD138 positiva en las 170 pacientes estudiadas fue de 36% (n = 62) y por histeroscopia del 48.8% (n = 83), esta última con una sensibilidad del 48.3%, especificidad del 50.9%, valor predictivo positivo y negativo del 36.1 y 63.2%, respectivamente. En relación con las características histeroscópicas, la hiperemia endometrial tuvo una relación estadísticamente significativa con la prevalencia de endometritis crónica (p-value = 0.008; RM = 0.357; IC95%: 0.14-0.81) y con ≥ 2 características sugerentes de endometritis crónica (p-value = 0.015; RM = 3.63; IC95%: 1.15-12.69). CONCLUSIONES: En el procedimiento diagnóstico de la paciente infértil es importante descartar la endometritis crónica. Para ello es decisivo recurrir a herramientas diagnósticas, como la histeroscopia y confirmar el diagnóstico con una biopsia de endometrio con inmunohistoquímica CD138 positiva para que de esta manera pueda dirigirse el tratamiento.

Abstract OBJECTIVE: To determine the prevalence of chronic endometritis in infertile patients by evaluating hysteroscopy and endometrial biopsy with endometrial histologic analysis and identification of plasma cells by CD138-positive immunohistochemistry. MATERIALS AND METHODS: Observational, retrospective study performed from March 2016 to November 2021 at the Center for Assisted Reproduction of Saltillo (CREAS), Coahuila, Mexico, in patients who consulted for infertility. Chronic endometritis was diagnosed by hysteroscopy and endometrial biopsy with CD138 immunohistochemistry. The prevalence and diagnostic accuracy of hysteroscopy and endometrial biopsy were analysed. The association between specific hysteroscopic features and chronic endometritis confirmed by CD138-positive endometrial biopsy was also investigated. RESULTS: The prevalence of chronic endometritis by CD138-positive endometrial biopsy in the 170 patients studied was 36% (n = 62) and by hysteroscopy 48.8% (n = 83), the latter with a sensitivity of 48.3%, specificity of 50.9%, positive and negative predictive values of 36.1 and 63.2%, respectively. In relation to hysteroscopic features, endometrial hyperemia had a statistically significant relationship with the prevalence of chronic endometritis (p-value = 0.008; RM = 0.357; 95%CI: 0.14-0.81) and with ≥ 2 features suggestive of chronic endometritis (p-value = 0.015; RM = 3.63; 95%CI: 1.15-12.69). CONCLUSIONS: In the diagnostic process of infertile patients, it is important to exclude chronic endometritis. It is crucial to use diagnostic tools such as hysteroscopy and to confirm the diagnosis by endometrial biopsy with positive CD138 immunohistochemistry in order to guide treatment.

Low- and high-grade glioma endothelial cells differentially regulate tumor growth.

Background: A key feature distinguishing high-grade glioma (HGG) from low-grade glioma (LGG) is the extensive neovascularization and endothelial hyperproliferation. Prior work has shown that tumor endothelial cells (TEC) from HGG are molecularly and functionally distinct from normal brain EC and secrete higher levels of pro-tumorigenic factors that promote glioma growth and progression. However, it remains unclear whether TEC from LGG also express pro-tumorigenic factors, and to what extent they functionally contribute to glioma growth. Methods: Transcriptomic profiling was conducted on tumor endothelial cells (TEC) from grade II/III (LGG, IDH-mutant) and grade IV HGG (IDH-wildtype). Functional differences between LGG- and HGG-TEC were evaluated using growth assays, resistance to anti-angiogenic drugs and radiation therapy. Conditioned media and specific factors from LGG- and HGG-TEC were tested on patient-derived gliomasphere lines using growth assays in vitro and in co-transplantation studies in vivo in orthotopic xenograft models. Results: LGG-TEC showed enrichment of extracellular matrix and cell cycle-related gene sets and sensitivity to anti-angiogenic therapy whereas HGG-TEC displayed an increase in immune response-related gene sets and anti-angiogenic resistance. LGG- and HGG-TEC displayed opposing effects on growth and proliferation of IDH-wildtype and mutant tumor cells. Asporin (ASPN), a small leucine rich proteoglycan enriched in LGG-TEC was identified as a growth suppressor of IDH-wildtype GBM by modulating TGFΒ1-GPM6A signaling. Conclusions: Our findings indicate that TEC from LGG and HGG are molecularly and functionally heterogeneous and differentially regulate the growth of IDH-wildtype and mutant tumors.

Interfer(on)ing with Zika virus.

In this issue of Neuron, Bulstrode et al.1 demonstrate that glioblastoma slice cultures, unlike neural progenitors, are refractory to Zika virus infection. The anti-infective mechanism is myeloid-lineage cell-secreted interferon beta. These studies have implications for therapeutics in both glioblastoma and Zika virus infections.

Pathway-based approach reveals differential sensitivity to E2F1 inhibition in glioblastoma.

Analysis of tumor gene expression is an important approach for the classification and identification of therapeutic vulnerabilities. However, targeting glioblastoma (GBM) based on molecular subtyping has not yet translated into successful therapies. Here, we present an integrative approach based on molecular pathways to expose new potentially actionable targets. We used gene set enrichment analysis (GSEA) to conduct an unsupervised clustering analysis to condense the gene expression data from bulk patient samples and patient-derived gliomasphere lines into new gene signatures. We identified key targets that are predicted to be differentially activated between tumors and were functionally validated in a library of gliomasphere cultures. Resultant cluster-specific gene signatures associated not only with hallmarks of cell cycle and stemness gene expression, but also with cell-type specific markers and different cellular states of GBM. Several upstream regulators, such as PIK3R1 and EBF1 were differentially enriched in cells bearing stem cell like signatures and bear further investigation. We identified the transcription factor E2F1 as a key regulator of tumor cell proliferation and self-renewal in only a subset of gliomasphere cultures predicted to be E2F1 signaling dependent. Our in vivo work also validated the functional significance of E2F1 in tumor formation capacity in the predicted samples. E2F1 inhibition also differentially sensitized E2F1-dependent gliomasphere cultures to radiation treatment. Our findings indicate that this novel approach exploring cancer pathways highlights key therapeutic vulnerabilities for targeting GBM.

P300 promotes tumor recurrence by regulating radiation-induced conversion of glioma stem cells to vascular-like cells.

Glioma stem cells (GSC) exhibit plasticity in response to environmental and therapeutic stress leading to tumor recurrence, but the underlying mechanisms remain largely unknown. Here, we employ single-cell and whole transcriptomic analyses to uncover that radiation induces a dynamic shift in functional states of glioma cells allowing for acquisition of vascular endothelial-like and pericyte-like cell phenotypes. These vascular-like cells provide trophic support to promote proliferation of tumor cells, and their selective depletion results in reduced tumor growth post-treatment in vivo. Mechanistically, the acquisition of vascular-like phenotype is driven by increased chromatin accessibility and H3K27 acetylation in specific vascular genes allowing for their increased expression post-treatment. Blocking P300 histone acetyltransferase activity reverses the epigenetic changes induced by radiation and inhibits the adaptive conversion of GSC into vascular-like cells and tumor growth. Our findings highlight a role for P300 in radiation-induced stress response, suggesting a therapeutic approach to prevent glioma recurrence.

Conservation and divergence of vulnerability and responses to stressors between human and mouse astrocytes.

Astrocytes play important roles in neurological disorders such as stroke, injury, and neurodegeneration. Most knowledge on astrocyte biology is based on studies of mouse models and the similarities and differences between human and mouse astrocytes are insufficiently characterized, presenting a barrier in translational research. Based on analyses of acutely purified astrocytes, serum-free cultures of primary astrocytes, and xenografted chimeric mice, we find extensive conservation in astrocytic gene expression between human and mouse samples. However, the genes involved in defense response and metabolism show species-specific differences. Human astrocytes exhibit greater susceptibility to oxidative stress than mouse astrocytes, due to differences in mitochondrial physiology and detoxification pathways. In addition, we find that mouse but not human astrocytes activate a molecular program for neural repair under hypoxia, whereas human but not mouse astrocytes activate the antigen presentation pathway under inflammatory conditions. Here, we show species-dependent properties of astrocytes, which can be informative for improving translation from mouse models to humans.

High-Dimensional Analysis of Circulating and Tissue-Derived Myeloid-Derived Suppressor Cells from Patients with Glioblastoma.

We will first describe analysis of MDSC subsets from patient tumors with multicolor flow cytometry. The key components of this methodology are to obtain viable single cell suspensions and eliminate red blood cell contamination.

Discovery of a dual inhibitor of NQO1 and GSTP1 for treating glioblastoma.

BACKGROUND: Glioblastoma (GBM) is a universally lethal tumor with frequently overexpressed or mutated epidermal growth factor receptor (EGFR). NADPH quinone oxidoreductase 1 (NQO1) and glutathione-S-transferase Pi 1 (GSTP1) are commonly upregulated in GBM. NQO1 and GSTP1 decrease the formation of reactive oxygen species (ROS), which mediates the oxidative stress and promotes GBM cell proliferation. METHODS: High-throughput screen was used for agents selectively active against GBM cells with EGFRvIII mutations. Co-crystal structures were revealed molecular details of target recognition. Pharmacological and gene knockdown/overexpression approaches were used to investigate the oxidative stress in vitro and in vivo. RESULTS: We identified a small molecular inhibitor, "MNPC," that binds to both NQO1 and GSTP1 with high affinity and selectivity. MNPC inhibits NQO1 and GSTP1 enzymes and induces apoptosis in GBM, specifically inhibiting the growth of cell lines and primary GBM bearing the EGFRvIII mutation. Co-crystal structures between MNPC and NQO1, and molecular docking of MNPC with GSTP1 reveal that it binds the active sites and acts as a potent dual inhibitor. Inactivation of both NQO1 and GSTP1 with siRNA or MNPC results in imbalanced redox homeostasis, leading to apoptosis and mitigated cancer proliferation in vitro and in vivo. CONCLUSIONS: Thus, MNPC, a dual inhibitor for both NQO1 and GSTP1, provides a novel lead compound for treating GBM via the exploitation of specific vulnerabilities created by mutant EGFR.

The Covid-19 pandemic seen from the frontline.

COVID-19 disease caused by infection with the SARS-CoV-2 virus produces respiratory symptoms, predominantly of the upper airways, which can progress to pneumonia after 7 days with persistent fever, cough and dyspnea, and even develop a syndrome of acute respiratory distress (ARDS), multi-organ failure and death. Since COVID-19 disease was declared by the WHO there has been a redistribution of the healthcare system for these types of patients, especially in the front line, which is, in primary care, emergencies and in intensive care units (ICU). In primary care, the fundamental role is the diagnosis of the suspected patients, follow-up mainly by telemedicine (specially telephone calls) to detect warning signs in case of worsening and subsequent referral to the emergency department; as well as explaining home isolation measures. In the emergency department, it is included the management of suspicious cases and, if it any risk factor is found, complementary tests are carried out for precise diagnosis and admission assessment; In case of oxygen saturation <95% and poor general condition, valuation is requested for admission to the ICU. Depending on the severity of the patient, he/she would be or not a candidate for invasive mechanical ventilation, which must be performed by trained personnel to prevent the spread of the infection minimizing the risk of contagion. ARDS's treatment strategies include pulmonary protection ventilation, prone position, recruitment maneuvers and, less frequently, oxygenation by extracorporeal membrane. Among the specific treatments for COVID-19 stand out mainly drugs to reduce viral load, although sometimes specific drugs will be needed to treat hyperinflammation, hypercoagulability and concomitant infections. One of the goals to be achieved is for patients to recover and be able to successfully return to work; for this purpose, an adequate physical and psychological rehabilitation program is essential, as about 50% have symptoms of anxiety and depression.

The Covid-19 pandemic seen from the frontline

ABSTRACT COVID-19 disease caused by infection with the SARS-CoV-2 virus produces respiratory symptoms, predominantly of the upper airways, which can progress to pneumonia after 7 days with persistent fever, cough and dyspnea, and even develop a syndrome of acute respiratory distress (ARDS), multi-organ failure and death. Since COVID-19 disease was declared by the WHO there has been a redistribution of the healthcare system for these types of patients, especially in the front line, which is, in primary care, emergencies and in intensive care units (ICU). In primary care, the fundamental role is the diagnosis of the suspected patients, follow-up mainly by telemedicine (specially telephone calls) to detect warning signs in case of worsening and subsequent referral to the emergency department; as well as explaining home isolation measures. In the emergency department, it is included the management of suspicious cases and, if it any risk factor is found, complementary tests are carried out for precise diagnosis and admission assessment; In case of oxygen saturation <95% and poor general condition, valuation is requested for admission to the ICU. Depending on the severity of the patient, he/she would be or not a candidate for invasive mechanical ventilation, which must be performed by trained personnel to prevent the spread of the infection minimizing the risk of contagion. ARDS's treatment strategies include pulmonary protection ventilation, prone position, recruitment maneuvers and, less frequently, oxygenation by extracorporeal membrane. Among the specific treatments for COVID-19 stand out mainly drugs to reduce viral load, although sometimes specific drugs will be needed to treat hyperinflammation, hypercoagulability and concomitant infections. One of the goals to be achieved is for patients to recover and be able to successfully return to work; for this purpose, an adequate physical and psychological rehabilitation program is essential, as about 50% have symptoms of anxiety and depression.

Metronomic capecitabine as an immune modulator in glioblastoma patients reduces myeloid-derived suppressor cells.

BACKGROUNDMyeloid-derived suppressor cells (MDSCs) are elevated in the circulation of patients with glioblastoma (GBM), present in tumor tissue, and associated with poor prognosis. While low-dose chemotherapy reduces MDSCs in preclinical models, the use of this strategy to reduce MDSCs in GBM patients has yet to be evaluated.METHODSA phase 0/I dose-escalation clinical trial was conducted in patients with recurrent GBM treated 5-7 days before surgery with low-dose chemotherapy via capecitabine, followed by concomitant low-dose capecitabine and bevacizumab. Clinical outcomes, including progression-free and overall survival, were measured, along with safety and toxicity profiles. Over the treatment time course, circulating MDSC levels were measured by multiparameter flow cytometry, and tumor tissue immune profiles were assessed via time-of-flight mass cytometry.RESULTSEleven patients total were enrolled across escalating dose cohorts of 150, 300, and 450 mg bid. No serious adverse events related to the drug combination were observed. Compared with pretreatment baseline, circulating MDSCs were found to be higher after surgery in the 150-mg treatment arm and lower in the 300-mg and 450-mg treatment arms. Increased cytotoxic immune infiltration was observed after low-dose capecitabine compared with untreated GBM patients in the 300-mg and 450-mg treatment arms.CONCLUSIONSLow-dose, metronomic capecitabine in combination with bevacizumab was well tolerated in GBM patients and was associated with a reduction in circulating MDSC levels and an increase in cytotoxic immune infiltration into the tumor microenvironment.TRIAL REGISTRATIONClinicalTrials.gov NCT02669173.FUNDINGThis research was funded by the Cleveland Clinic, Case Comprehensive Cancer Center, the Musella Foundation, B*CURED, the NIH, the National Cancer Institute, the Sontag Foundation, Blast GBM, the James B. Pendleton Charitable Trust, and the Dr. Miriam and Sheldon G. Adelson Medical Research Foundation. Capecitabine was provided in kind by Mylan Pharmaceuticals.

Global immune fingerprinting in glioblastoma patient peripheral blood reveals immune-suppression signatures associated with prognosis.

Glioblastoma (GBM) remains uniformly lethal, and despite a large accumulation of immune cells in the microenvironment, there is limited antitumor immune response. To overcome these challenges, a comprehensive understanding of GBM systemic immune response during disease progression is required. Here, we integrated multiparameter flow cytometry and mass cytometry TOF (CyTOF) analysis of patient blood to determine changes in the immune system among tumor types and over disease progression. Utilizing flow cytometry analysis in a cohort of 259 patients ranging from benign to malignant primary and metastatic brain tumors, we found that GBM patients had a significant elevation in myeloid-derived suppressor cells (MDSCs) in peripheral blood but not immunosuppressive Tregs. In GBM patient tissue, we found that increased MDSC levels in recurrent GBM portended poor prognosis. CyTOF analysis of peripheral blood from newly diagnosed GBM patients revealed that reduced MDSCs over time were accompanied by a concomitant increase in DCs. GBM patients with extended survival also had reduced MDSCs, similar to the levels of low-grade glioma (LGG) patients. Our findings provide a rationale for developing strategies to target MDSCs, which are elevated in GBM patients and predict poor prognosis.

Building Bonds: Cancer Stem Cells Depend on Their Progeny to Drive Tumor Progression.

Little is currently known about how cancer stem-like cells (CSCs) interact with their more restricted progeny. In this issue of Cell Stem Cell, Wang et al. (2018) demonstrate a novel bidirectional signaling axis between CSCs and their progeny that is mediated by brain-derived neurotrophic factor and VGF accelerating glioma progression.

Cx26 drives self-renewal in triple-negative breast cancer via interaction with NANOG and focal adhesion kinase.

Tumors adapt their phenotypes during growth and in response to therapies through dynamic changes in cellular processes. Connexin proteins enable such dynamic changes during development, and their dysregulation leads to disease states. The gap junction communication channels formed by connexins have been reported to exhibit tumor-suppressive functions, including in triple-negative breast cancer (TNBC). However, we find that connexin 26 (Cx26) is elevated in self-renewing cancer stem cells (CSCs) and is necessary and sufficient for their maintenance. Cx26 promotes CSC self-renewal by forming a signaling complex with the pluripotency transcription factor NANOG and focal adhesion kinase (FAK), resulting in NANOG stabilization and FAK activation. This FAK/NANOG-containing complex is not formed in mammary epithelial or luminal breast cancer cells. These findings challenge the paradigm that connexins are tumor suppressors in TNBC and reveal a unique function for Cx26 in regulating the core self-renewal signaling that controls CSC maintenance.

A molecular cascade modulates MAP1B and confers resistance to mTOR inhibition in human glioblastoma.

Background: Clinical trials of therapies directed against nodes of the signaling axis of phosphatidylinositol-3 kinase/Akt/mammalian target of rapamycin (mTOR) in glioblastoma (GBM) have had disappointing results. Resistance to mTOR inhibitors limits their efficacy. Methods: To determine mechanisms of resistance to chronic mTOR inhibition, we performed tandem screens on patient-derived GBM cultures. Results: An unbiased phosphoproteomic screen quantified phosphorylation changes associated with chronic exposure to the mTOR inhibitor rapamycin, and our analysis implicated a role for glycogen synthase kinase (GSK)3B attenuation in mediating resistance that was confirmed by functional studies. A targeted short hairpin RNA screen and further functional studies both in vitro and in vivo demonstrated that microtubule-associated protein (MAP)1B, previously associated predominantly with neurons, is a downstream effector of GSK3B-mediated resistance. Furthermore, we provide evidence that chronic rapamycin induces microtubule stability in a MAP1B-dependent manner in GBM cells. Additional experiments explicate a signaling pathway wherein combinatorial extracellular signal-regulated kinase (ERK)/mTOR targeting abrogates inhibitory phosphorylation of GSK3B, leads to phosphorylation of MAP1B, and confers sensitization. Conclusions: These data portray a compensatory molecular signaling network that imparts resistance to chronic mTOR inhibition in primary, human GBM cell cultures and points toward new therapeutic strategies.

A 4-miRNA signature to predict survival in glioblastomas.

Glioblastomas are among the most lethal cancers; however, recent advances in survival have increased the need for better prognostic markers. microRNAs (miRNAs) hold great prognostic potential being deregulated in glioblastomas and highly stable in stored tissue specimens. Moreover, miRNAs control multiple genes representing an additional level of gene regulation possibly more prognostically powerful than a single gene. The aim of the study was to identify a novel miRNA signature with the ability to separate patients into prognostic subgroups. Samples from 40 glioblastoma patients were included retrospectively; patients were comparable on all clinical aspects except overall survival enabling patients to be categorized as short-term or long-term survivors based on median survival. A miRNome screening was employed, and a prognostic profile was developed using leave-one-out cross-validation. We found that expression patterns of miRNAs; particularly the four miRNAs: hsa-miR-107_st, hsa-miR-548x_st, hsa-miR-3125_st and hsa-miR-331-3p_st could determine short- and long-term survival with a predicted accuracy of 78%. Heatmap dendrograms dichotomized glioblastomas into prognostic subgroups with a significant association to survival in univariate (HR 8.50; 95% CI 3.06-23.62; p<0.001) and multivariate analysis (HR 9.84; 95% CI 2.93-33.06; p<0.001). Similar tendency was seen in The Cancer Genome Atlas (TCGA) using a 2-miRNA signature of miR-107 and miR-331 (miR sum score), which were the only miRNAs available in TCGA. In TCGA, patients with O6-methylguanine-DNA-methyltransferase (MGMT) unmethylated tumors and low miR sum score had the shortest survival. Adjusting for age and MGMT status, low miR sum score was associated with a poorer prognosis (HR 0.66; 95% CI 0.45-0.97; p = 0.033). A Kyoto Encyclopedia of Genes and Genomes analysis predicted the identified miRNAs to regulate genes involved in cell cycle regulation and survival. In conclusion, the biology of miRNAs is complex, but the identified 4-miRNA expression pattern could comprise promising biomarkers in glioblastoma stratifying patients into short- and long-term survivors.