Lymphocyte-Activation Gene 3 Facilitates Pathological Tau Neuron-to-Neuron Transmission

The spread of prion-like protein aggregates is a common driver of pathogenesis in various neurodegenerative diseases, including Alzheimer's disease (AD) and related Tauopathies. Tau pathologies exhibit a clear progressive spreading pattern that correlates with disease severity. Clinical observation combined with complementary experimental studies has shown that Tau preformed fibrils (PFF) are prion-like seeds that propagate pathology by entering cells and templating misfolding and aggregation of endogenous Tau. While several cell surface receptors of Tau are known, they are not specific to the fibrillar form of Tau. Moreover, the underlying cellular mechanisms of Tau PFF spreading remain poorly understood. Here, it is shown that the lymphocyte-activation gene 3 (Lag3) is a cell surface receptor that binds to PFF but not the monomer of Tau. Deletion of Lag3 or inhibition of Lag3 in primary cortical neurons significantly reduces the internalization of Tau PFF and subsequent Tau propagation and neuron-to-neuron transmission. Propagation of Tau pathology and behavioral deficits induced by injection of Tau PFF in the hippocampus and overlying cortex are attenuated in mice lacking Lag3 selectively in neurons. These results identify neuronal Lag3 as a receptor of pathologic Tau in the brain，and for AD and related Tauopathies, a therapeutic target.

Bidirectional Transcription at the PPP2R2B Gene Locus in Spinocerebellar Ataxia Type 12

BACKGROUND

Spinocerebellar ataxia type 12 (SCA12) is a neurodegenerative disease caused by expansion of a CAG repeat in the PPP2R2B gene.

OBJECTIVE

In this study, we tested the hypothesis that the PPP2R2B antisense (PPP2R2B-AS1) transcript containing a CUG repeat is expressed and contributes to SCA12 pathogenesis.

METHODS

Expression of PPP2R2B-AS1 transcript was detected in SCA12 human induced pluripotent stem cells (iPSCs), iPSC-derived NGN2 neurons, and SCA12 knock-in mouse brains using strand-specific reverse transcription polymerase chain reaction. The tendency of expanded PPP2R2B-AS1 (expPPP2R2B-AS1) RNA to form foci, a marker of toxic processes involving mutant RNAs, was examined in SCA12 cell models by fluorescence in situ hybridization. The apoptotic effect of expPPP2R2B-AS1 transcripts on SK-N-MC neuroblastoma cells was evaluated by caspase 3/7 activity. Western blot was used to examine the expression of repeat associated non-ATG-initiated translation of expPPP2R2B-AS1 transcript in SK-N-MC cells.

RESULTS

The repeat region in the PPP2R2B gene locus is bidirectionally transcribed in SCA12 iPSCs, iPSC-derived NGN2 neurons, and SCA12 mouse brains. Transfected expPPP2R2B-AS1 transcripts induce apoptosis in SK-N-MC cells, and the apoptotic effect may be mediated, at least in part, by the RNA secondary structure. The expPPP2R2B-AS1 transcripts form CUG RNA foci in SK-N-MC cells. expPPP2R2B-AS1 transcript is translated in the alanine open reading frame (ORF) via repeat-associated non-ATG translation, which is diminished by single-nucleotide interruptions within the CUG repeat and MBNL1 overexpression.

CONCLUSIONS

These findings suggest that PPP2R2B-AS1 contributes to SCA12 pathogenesis and may therefore provide a novel therapeutic target for the disease. © 2023 International Parkinson and Movement Disorder Society.

Cell Therapy for Parkinson's Disease

Parkinson's Disease (PD) is a neurodegenerative disease characterized by the progressive loss of dopaminergic neurons of the substantia nigra pars compacta with a reduction in dopamine concentration in the striatum. It is a substantial loss of dopaminergic neurons that is responsible for the classic triad of PD symptoms, i.e., resting tremor, muscular rigidity, and bradykinesia. Several current therapies for PD may only offer symptomatic relief and do not address the underlying neurodegeneration of PD. The recent developments in cellular reprogramming have enabled the development of previously unachievable cell therapies and patient-specific modeling of PD through Induced Pluripotent Stem Cells (iPSCs). iPSCs possess the inherent capacity for pluripotency, allowing for their directed differentiation into diverse cell lineages, such as dopaminergic neurons, thus offering a promising avenue for addressing the issue of neurodegeneration within the context of PD. This narrative review provides a comprehensive overview of the effects of dopamine on PD patients, illustrates the versatility of iPSCs and their regenerative abilities, and examines the benefits of using iPSC treatment for PD as opposed to current therapeutic measures. In means of providing a treatment approach that reinforces the long-term survival of the transplanted neurons, the review covers three supplementary avenues to reinforce the potential of iPSCs.

Tyrosine kinase signaling-independent MET-targeting with CAR-T cells

BACKGROUND

Recent progress in cancer immunotherapy encourages the expansion of chimeric antigen receptor (CAR) T cell therapy in solid tumors including hepatocellular carcinoma (HCC). Overexpression of MET receptor tyrosine kinase is common in HCC; however, MET inhibitors are effective only when MET is in an active form, making patient stratification difficult. Specific MET-targeting CAR-T cells hold the promise of targeting HCC with MET overexpression regardless of signaling pathway activity.

METHODS

MET-specific CARs with CD28ζ or 4-1BBζ as co-stimulation domains were constructed. MET-CAR-T cells derived from healthy subjects (HS) and HCC patients were evaluated for their killing activity and cytokine release against HCC cells with various MET activations in vitro, and for their tumor growth inhibition in orthotopic xenograft models in vivo.

RESULTS

MET-CAR.CD28ζ and MET-CAR.4-1BBζ T cells derived from both HS and HCC patients specifically killed MET-positive HCC cells. When stimulated with MET-positive HCC cells in vitro, MET-CAR.CD28ζ T cells demonstrated a higher level of cytokine release and expression of programmed cell death protein 1 (PD-1) than MET-CAR.4-1BBζ T cells. When analyzed in vivo, MET-CAR.CD28ζ T cells more effectively inhibited HCC orthotopic tumor growth in mice when compared to MET-CAR.4-1BBζ T cells.

CONCLUSION

We generated and characterized MET-specific CAR-T cells for targeting HCC with MET overexpression regardless of MET activation. Compared with MET-CAR.4-1BBζ, MET-CAR.CD28ζ T cells showed a higher anti-HCC potency but also a higher level of T cell exhaustion. While MET-CAR.CD28ζ is preferred for further development, overcoming the exhaustion of MET-CAR-T cells is necessary to improve their therapeutic efficacy in vivo.

Mutations in DARS2 result in global dysregulation of mRNA metabolism and splicing

Leukoencephalopathy with brainstem and spinal cord involvement and lactate elevation (LBSL) is a rare neurological disorder caused by the mutations in the DARS2 gene, which encodes the mitochondrial aspartyl-tRNA synthetase. The objective of this study was to understand the impact of DARS2 mutations on cell processes through evaluation of LBSL patient stem cell derived cerebral organoids and neurons. We generated human cerebral organoids (hCOs) from induced pluripotent stem cells (iPSCs) of seven LBSL patients and three healthy controls using an unguided protocol. Single cells from 70-day-old hCOs were subjected to SMART-seq2 sequencing and bioinformatic analysis to acquire high-resolution gene and transcript expression datasets. Global gene expression analysis demonstrated dysregulation of a number of genes involved in mRNA metabolism and splicing processes within LBSL hCOs. Importantly, there were distinct and divergent gene expression profiles based on the nature of the DARS2 mutation. At the transcript level, pervasive differential transcript usage and differential spliced exon events that are involved in protein translation and metabolism were identified in LBSL hCOs. Single-cell analysis of DARS2 (exon 3) showed that some LBSL cells exclusively express transcripts lacking exon 3, indicating that not all LBSL cells can benefit from the "leaky" nature common to splice site mutations. At the gene- and transcript-level, we uncovered that dysregulated RNA splicing, protein translation and metabolism may underlie at least some of the pathophysiological mechanisms in LBSL. To confirm hCO findings, iPSC-derived neurons (iNs) were generated by overexpressing Neurogenin 2 using lentiviral vector to study neuronal growth, splicing of DARS2 exon 3 and DARS2 protein expression. Live cell imaging revealed neuronal growth defects of LBSL iNs, which was consistent with the finding of downregulated expression of genes related to neuronal differentiation in LBSL hCOs. DARS2 protein was downregulated in iNs compared to iPSCs, caused by increased exclusion of exon 3. The scope and complexity of our data imply that DARS2 is potentially involved in transcription regulation beyond its canonical role of aminoacylation. Nevertheless, our work highlights transcript-level dysregulation as a critical, and relatively unexplored, mechanism linking genetic data with neurodegenerative disorders.

Pathological Tau transmission initiated by binding lymphocyte-activation gene 3

The spread of prion-like protein aggregates is believed to be a common driver of pathogenesis in many neurodegenerative diseases. Accumulated tangles of filamentous Tau protein are considered pathogenic lesions of Alzheimer's disease (AD) and related Tauopathies, including progressive supranuclear palsy, and corticobasal degeneration. Tau pathologies in these illnesses exhibits a clear progressive and hierarchical spreading pattern that correlates with disease severity1,2. Clinical observation combined with complementary experimental studies3,4 have shown that Tau preformed fibrils (PFF) are prion-like seeds that propagate pathology by entering cells and templating misfolding and aggregation of endogenous Tau. While several receptors of Tau are known, they are not specific to the fibrillar form of Tau. Moreover, the underlying cellular mechanisms of Tau PFF spreading remains poorly understood. Here, we show that the lymphocyte-activation gene 3 (Lag3) is a cell surface receptor that binds to PFF, but not monomer, of Tau. Deletion of Lag3 or inhibition of Lag3 in primary cortical neurons significantly reduces the internalization of Tau PFF and subsequent Tau propagation and neuron-to-neuron transmission. Propagation of Tau pathology and behavioral deficits induced by injection of Tau PFF in the hippocampus and overlying cortex are attenuated in mice lacking Lag3 selectively in neurons. Our results identify neuronal Lag3 as a receptor of pathologic Tau in the brain, and for AD and related Tauopathies a therapeutic target.

Bidirectional transcription at the PPP2R2B gene locus in spinocerebellar ataxia type 12

OBJECTIVE

Spinocerebellar ataxia type 12 (SCA12) is a neurodegenerative disease caused by expansion of a CAG repeat in the PPP2R2B gene . Here we tested the hypothesis that the PPP2R2B antisense ( PPP2R2B-AS1 ) transcript containing a CUG repeat is expressed and contributes to SCA12 pathogenesis.

METHODS

Expression of PPP2R2B-AS1 transcript was detected in SCA12 human induced pluripotent stem cells (iPSCs), iPSC-derived NGN2 neurons, and SCA12 knock-in mouse brains using strand-specific RT-PCR (SS-RT-PCR). The tendency of expanded PPP2R2B-AS1 ( expPPP2R2B-AS1 ) RNA to form foci, a marker of toxic processes involving mutant RNAs, was examined in SCA12 cell models by fluorescence in situ hybridization. The toxic effect of expPPP2R2B-AS1 transcripts on SK-N-MC neuroblastoma cells was evaluated by caspase 3/7 activity. Western blot was used to examine the expression of repeat associated non-ATG-initiated (RAN) translation of expPPP2R2B-AS1 transcript in SK-N-MC cells.

RESULTS

The repeat region in PPP2R2B gene locus is bidirectionally transcribed in SCA12 iPSCs, iPSC-derived NGN2 neurons, and SCA12 mouse brains. Transfected expPPP2R2B-AS1 transcripts are toxic to SK-N-MC cells, and the toxicity may be mediated, at least in part, by the RNA secondary structure. The expPPP2R2B-AS1 transcripts form CUG RNA foci in SK-N-MC cells. expPPP2R2B-AS1 transcript is translated in the Alanine ORF via repeat-associated non-ATG (RAN) translation, which is diminished by single nucleotide interruptions within the CUG repeat, and MBNL1 overexpression.

INTERPRETATION

These findings suggest that PPP2R2B-AS1 contributes to SCA12 pathogenesis, and may therefore provide a novel therapeutic target for the disease.

Mutations in DARS2 result in global dysregulation of mRNA metabolism and splicing

Leukoencephalopathy with brain stem and spinal cord involvement and lactate elevation (LBSL) is a rare neurological disorder caused by the mutations in the DARS2 gene, which encodes the mitochondrial aspartyl-tRNA synthetase. The objective of this study was to understand the impact of DARS2 mutations on cell processes through evaluation of LBSL patient stem cell derived cerebral organoids and neurons. We generated human cerebral organoids (hCOs) from induced pluripotent stem cells (iPSCs) of seven LBSL patients and three healthy controls using an unguided protocol. Single cells from 70-day-old hCOs underwent SMART-seq2 sequencing and multiple bioinformatic analysis tools were applied to high-resolution gene and transcript expression analyses. To confirm hCO findings, iPSC-derived neurons (iNs) were generated by overexpressing Neurogenin 2 using lentiviral vector to study neuronal growth, splicing of DARS2 exon 3 and DARS2 protein expression. Global gene expression analysis demonstrated dysregulation of a number of genes involved in mRNA metabolism and splicing processes within LBSL hCOs. Importantly, there were distinct and divergent gene expression profiles based on the nature of the DARS2 mutation. At the transcript level, pervasive differential transcript usage and differential spliced exon events that are involved in protein translation and metabolism were identified in LBSL hCOs. Single-cell analysis of DARS2 (exon 3) showed that some LBSL cells exclusively express transcripts lacking exon 3, indicating that not all LBSL cells can benefit from the "leaky" nature common to splice site mutations. Live cell imaging revealed neuronal growth defects of LBSL iNs, which was consistent with the finding of downregulated expression of genes related to neuronal differentiation in LBSL hCOs. DARS2 protein was downregulated in iNs compared to iPSCs, caused by increased exclusion of exon 3. At the gene- and transcript-level, we uncovered that dysregulated RNA splicing, protein translation and metabolism may underlie at least some of the pathophysiological mechanisms in LBSL. The scope and complexity of our data imply that DARS2 is potentially involved in transcription regulation beyond its canonical role of aminoacylation. Nevertheless, our work highlights transcript-level dysregulation as a critical, and relatively unexplored, mechanism linking genetic data with neurodegenerative disorders.

Search for Subsolar-Mass Binaries in the First Half of Advanced LIGO's and Advanced Virgo's Third Observing Run

We report on a search for compact binary coalescences where at least one binary component has a mass between 0.2  M_{⊙} and 1.0  M_{⊙} in Advanced LIGO and Advanced Virgo data collected between 1 April 2019 1500 UTC and 1 October 2019 1500 UTC. We extend our previous analyses in two main ways: we include data from the Virgo detector and we allow for more unequal mass systems, with mass ratio q≥0.1. We do not report any gravitational-wave candidates. The most significant trigger has a false alarm rate of 0.14  yr^{-1}. This implies an upper limit on the merger rate of subsolar binaries in the range [220-24200]  Gpc^{-3} yr^{-1}, depending on the chirp mass of the binary. We use this upper limit to derive astrophysical constraints on two phenomenological models that could produce subsolar-mass compact objects. One is an isotropic distribution of equal-mass primordial black holes. Using this model, we find that the fraction of dark matter in primordial black holes in the mass range 0.2  M_{⊙}<m_{PBH}<1.0  M_{⊙} is f_{PBH}≡Ω_{PBH}/Ω_{DM}≲6%. This improves existing constraints on primordial black hole abundance by a factor of ∼3. The other is a dissipative dark matter model, in which fermionic dark matter can collapse and form black holes. The upper limit on the fraction of dark matter black holes depends on the minimum mass of the black holes that can be formed: the most constraining result is obtained at M_{min}=1  M_{⊙}, where f_{DBH}≡Ω_{DBH}/Ω_{DM}≲0.003%. These are the first constraints placed on dissipative dark models by subsolar-mass analyses.

ATRX loss promotes immunosuppressive mechanisms in IDH1 mutant glioma

BACKGROUND

ATRX inactivation occurs with IDH1R132H and p53 mutations in over 80% of Grades II/III astrocytomas. It is believed that ATRX loss contributes to oncogenesis by dysregulating epigenetic and telomere mechanisms but effects on anti-glioma immunity have not been explored. This paper examines how ATRX loss contributes to the malignant and immunosuppressive phenotypes of IDH1R132H/p53mut glioma cells and xenografts.

METHODS

Isogenic astrocytoma cells (+/-IDH1R132H/+/-ATRXloss) were established in p53mut astrocytoma cell lines using lentivirus encoding doxycycline-inducible IDH1R132H, ATRX shRNA, or Lenti-CRISPR/Cas9 ATRX. Effects of IDH1R132H+/-ATRXloss on cell migration, growth, DNA repair, and tumorigenicity were evaluated by clonal growth, transwell and scratch assays, MTT, immunofluorence and immunoblotting assays, and xenograft growth. Effects on the expression and function of modulators of the immune microenvironment were quantified by qRT-PCR, immunoblot, T-cell function, macrophage polarization, and flow cytometry assays. Pharmacologic inhibitors were used to examine epigenetic drivers of the immunosuppressive transcriptome of IDH1R132H/p53mut/ATRXloss cells.

RESULTS

Adding ATRX loss to the IDH1R132H/p53mut background promoted astrocytoma cell aggressiveness, induced expression of BET proteins BRD3/4 and an immune-suppressive transcriptome consisting of up-regulated immune checkpoints (e.g., PD-L1, PD-L2) and altered cytokine/chemokine profiles (e.g., IL33, CXCL8, CSF2, IL6, CXCL9). ATRX loss enhanced the capacity of IDH1R132H/p53mut cells to induce T-cell apoptosis, tumorigenic/anti-inflammatory macrophage polarization and Treg infiltration. The transcriptional and biological immune-suppressive responses to ATRX loss were enhanced by temozolomide and radiation and abrogated by pharmacologic BET inhibition.

CONCLUSIONS

ATRX loss activates a BRD-dependent immune-suppressive transcriptome and immune escape mechanism in IDH1R132H/p53mut astrocytoma cells.

Edaravone activates the GDNF/RET neurotrophic signaling pathway and protects mRNA-induced motor neurons from iPS cells

BACKGROUND

Spinal cord motor neurons (MNs) from human iPS cells (iPSCs) have wide applications in disease modeling and therapeutic development for amyotrophic lateral sclerosis (ALS) and other MN-associated neurodegenerative diseases. We need highly efficient MN differentiation strategies for generating iPSC-derived disease models that closely recapitulate the genetic and phenotypic complexity of ALS. An important application of these models is to understand molecular mechanisms of action of FDA-approved ALS drugs that only show modest clinical efficacy. Novel mechanistic insights will help us design optimal therapeutic strategies together with predictive biomarkers to achieve better efficacy.

METHODS

We induce efficient MN differentiation from iPSCs in 4 days using synthetic mRNAs coding two transcription factors (Ngn2 and Olig2) with phosphosite modification. These MNs after extensive characterization were applied in electrophysiological and neurotoxicity assays as well as transcriptomic analysis, to study the neuroprotective effect and molecular mechanisms of edaravone, an FDA-approved drug for ALS, for improving its clinical efficacy.

RESULTS

We generate highly pure and functional mRNA-induced MNs (miMNs) from control and ALS iPSCs, as well as embryonic stem cells. Edaravone alleviates H2O2-induced neurotoxicity and electrophysiological dysfunction in miMNs, demonstrating its neuroprotective effect that was also found in the glutamate-induced miMN neurotoxicity model. Guided by the transcriptomic analysis, we show a previously unrecognized effect of edaravone to induce the GDNF receptor RET and the GDNF/RET neurotrophic signaling in vitro and in vivo, suggesting a clinically translatable strategy to activate this key neuroprotective signaling. Notably, edaravone can replace required neurotrophic factors (BDNF and GDNF) to support long-term miMN survival and maturation, further supporting the neurotrophic function of edaravone-activated signaling. Furthermore, we show that edaravone and GDNF combined treatment more effectively protects miMNs from H2O2-induced neurotoxicity than single treatment, suggesting a potential combination strategy for ALS treatment.

CONCLUSIONS

This study provides methodology to facilitate iPSC differentiation and disease modeling. Our discoveries will facilitate the development of optimal edaravone-based therapies for ALS and potentially other neurodegenerative diseases.

Targeting UDP-α-d-glucose 6-dehydrogenase alters the CNS tumor immune microenvironment and inhibits glioblastoma growth

Glioblastoma (GBM, WHO grade IV glioma) is the most common and lethal malignant brain tumor in adults with a dismal prognosis. The extracellular matrix (ECM) supports GBM progression by promoting tumor cell proliferation, migration, and immune escape. Uridine diphosphate (UDP)-glucose 6-dehydrogenase (UGDH) is the rate-limiting enzyme that catalyzes the biosynthesis of glycosaminoglycans that are the principal component of the CNS ECM. We investigated how targeting UGDH in GBM influences the GBM immune microenvironment, including tumor-associated microglia/macrophages (TAMs) and T cells. TAMs are the main immune effector cells in GBM and can directly target tumor cells if properly activated. In co-cultures of GBM cells and human primary macrophages, UGDH knockdown in GBM cells promoted macrophage phagocytosis and M1-like polarization. In orthotropic human GBM xenografts and syngeneic mouse glioma models, targeting UGDH decreased ECM deposition, increased TAM phagocytosis marker expression, reduced M2-like TAMs and inhibited tumor growth. UGDH knockdown in GBM cells also promoted cytotoxic T cell infiltration and activation in orthotopic syngeneic mouse glioma models. The potent and in-human-use small molecule GAG synthesis inhibitor 4-methylumbelliferone (4-MU) was found to inhibit GBM cell proliferation and migration in vitro, mimic the macrophage and T-cell responses to UGDH knockdown in vitro and in vivo and inhibit growth of orthotopic murine GBM. Our study shows that UGDH supports GBM growth through multiple mechanisms and supports the development of ECM-based therapeutic strategies to simultaneously target tumor cells and their microenvironment.

Monoallelic IDH1 R132H Mutation Mediates Glioma Cell Response to Anticancer Therapies via Induction of Senescence

Heterozygous isocitrate dehydrogenase (IDH) R132H mutation (IDH1^R132H/WT) is an early event during gliomagenesis. Clinically, patients with glioma carrying mutant IDH1 respond better to antitumor therapies. However, the mechanism by which IDH1 mutations contribute to gliomagenesis and therapeutic response remains elusive. Here we report that senescence is involved in the improved therapeutic responses of mutant IDH1 glioma cells. Knocking-in IDH1^R132H/WT in glioma cells significantly enhanced gliomas cell senescence in response to temozolomide and radiation via a DNA-damage mediated mechanism. We further asked if senescence plays a role in IDH1^R132H/WT-induced gliomagenesis. Together with ATRX knockout and p53/RB loss, IDH1^R132H/WT transformed nonneoplastic human astroglial cells to form tumors in mouse brains. In-depth characterization revealed that a subset of these precancerous cells underwent senescence-like phenotypic changes, including flat and enlarged-cell morphology, increased senescence marker expression, decreased cell proliferation, and cell-cycle arrest at the G₂-M phase. Mechanistic studies indicated that the combination of glioma driver genes (p53/RB/IDH1/ATRX) dramatically increased DNA damage and activated DNAdamage response (DDR) pathways ATR/ATR and Chk1/Chk2 in senescent cells. To determine how senescent cells drive tumor formation, we investigated non-cell-autonomous mechanisms such as senescence-associated secretory phenotype (SASP), a panel of proinflammatory and tissue-remodeling factors implicated in a tumor-permissive microenvironment. We found that astroglial cells carrying p53/RB/ATRX loss and IDH1^R132H/WT upregulated key factors in SASP via an epigenetic-mediated mechanism. Our work suggests that drugs that specifically eliminate senescent cells could help kill precancerous cells and senescent tumor cells following antitumor therapies. IMPLICATIONS: The mechanisms by which IDH1 mutations contribute to gliomagenesis and therapeutic responses remain incompletely characterized; this work reveals senescence as a novel mechanism of IDH-mutant-mediated biological impact and describes new therapeutic opportunities concerning IDH1-mutant gliomas.

EGFR Activates a TAZ-Driven Oncogenic Program in Glioblastoma

Hyperactivated EGFR signaling is a driver of various human cancers, including glioblastoma (GBM). Effective EGFR-targeted therapies rely on knowledge of key signaling hubs that transfer and amplify EGFR signaling. Here we focus on the transcription factor TAZ, a potential signaling hub in the EGFR signaling network. TAZ expression was positively associated with EGFR expression in clinical GBM specimens. In patient-derived GBM neurospheres, EGF induced TAZ through EGFR-ERK and EGFR-STAT3 signaling, and the constitutively active EGFRvIII mutation caused EGF-independent hyperactivation of TAZ. Genome-wide analysis showed that the EGFR-TAZ axis activates multiple oncogenic signaling mechanisms, including an EGFR-TAZ-RTK positive feedback loop, as well as upregulating HIF1α and other oncogenic genes. TAZ hyperactivation in GBM stem-like cells induced exogenous mitogen-independent growth and promoted GBM invasion, radioresistance, and tumorigenicity. Screening a panel of brain-penetrating EGFR inhibitors identified osimertinib as the most potent inhibitor of the EGFR-TAZ signaling axis. Systemic osimertinib treatment inhibited the EGFR-TAZ axis and in vivo growth of GBM stem-like cell xenografts. Overall these results show that the therapeutic efficacy of osimertinib relies on effective TAZ inhibition, thus identifying TAZ as a potential biomarker of osimertinib sensitivity. SIGNIFICANCE: This study establishes a genome-wide map of EGFR-TAZ signaling in glioblastoma and finds osimertinib effectively inhibits this signaling, justifying its future clinical evaluation to treat glioblastoma and other cancers with EGFR/TAZ hyperactivation. GRAPHICAL ABSTRACT: http://cancerres.aacrjournals.org/content/canres/81/13/3580/F1.large.jpg.

Constraints on Cosmic Strings Using Data from the Third Advanced LIGO-Virgo Observing Run

We search for gravitational-wave signals produced by cosmic strings in the Advanced LIGO and Virgo full O3 dataset. Search results are presented for gravitational waves produced by cosmic string loop features such as cusps, kinks, and, for the first time, kink-kink collisions. A template-based search for short-duration transient signals does not yield a detection. We also use the stochastic gravitational-wave background energy density upper limits derived from the O3 data to constrain the cosmic string tension Gμ as a function of the number of kinks, or the number of cusps, for two cosmic string loop distribution models. Additionally, we develop and test a third model that interpolates between these two models. Our results improve upon the previous LIGO-Virgo constraints on Gμ by 1 to 2 orders of magnitude depending on the model that is tested. In particular, for the one-loop distribution model, we set the most competitive constraints to date: Gμ≲4×10^{-15}. In the case of cosmic strings formed at the end of inflation in the context of grand unified theories, these results challenge simple inflationary models.

Constraints on Cosmic Strings Using Data from the Third Advanced LIGO-Virgo Observing Run

We search for gravitational-wave signals produced by cosmic strings in the Advanced LIGO and Virgo full O3 dataset. Search results are presented for gravitational waves produced by cosmic string loop features such as cusps, kinks, and, for the first time, kink-kink collisions. A template-based search for short-duration transient signals does not yield a detection. We also use the stochastic gravitational-wave background energy density upper limits derived from the O3 data to constrain the cosmic string tension Gμ as a function of the number of kinks, or the number of cusps, for two cosmic string loop distribution models. Additionally, we develop and test a third model that interpolates between these two models. Our results improve upon the previous LIGO-Virgo constraints on Gμ by 1 to 2 orders of magnitude depending on the model that is tested. In particular, for the one-loop distribution model, we set the most competitive constraints to date: Gμ≲4×10^{-15}. In the case of cosmic strings formed at the end of inflation in the context of grand unified theories, these results challenge simple inflationary models.

Mutant IDH1 promotes phagocytic function of microglia/macrophages in gliomas by downregulating ICAM1

Tumor-associated microglia/macrophages (TAMs) are the main innate immune effector cells in malignant gliomas and have both pro- and anti-tumor functions. The plasticity of TAMs is partially dictated by oncogenic mutations in tumor cells. Heterozygous IDH1 mutation is a cancer driver gene prevalent in grade II/III gliomas, and IDH1 mutant gliomas have relatively favorable clinical outcomes. It is largely unknown how IDH mutation alters TAM phenotypes to influence glioma growth. Here we established clinically relevant isogenic glioma models carrying monoallelic IDH1 R132H mutation (IDH1^R132H/WT) and found that IDH1^R132H/WT significantly downregulated immune response-related pathways in glioma cells, indicating an immunomodulation role of mutant IDH1. Co-culturing IDH1^R132H/WT glioma cells with human macrophages promoted anti-tumor phenotypes of macrophages and increased macrophage migration and phagocytic capacity. In orthotopic xenografts, IDH1^R132H/WT decreased tumor growth and prolonged animal survival, accompanied by increased TAM recruitment and upregulated phagocytosis markers, suggesting the induction of anti-tumor TAM functions. Using human cytokine arrays that query 36 proteins, we identified significant downregulation of ICAM-1/CD54 in IDH1^R132H/WT gliomas, which was further confirmed by ELISA and immunoblotting analyses. ICAM1 gain-of-function studies revealed that ICAM1 downregulation in IDH1^R132H/WT cells played a mechanistic role to mediate the immunomodulation function of IDH1^R132H/WT. ICAM-1 silencing in IDH1 wild-type glioma cells decreased tumor growth and increased the anti-tumor function of TAMs. Together, our studies support a new TAM-mediated phagocytic function within IDH1 mutant gliomas, and improved understanding of this process may uncover novel approaches to targeting IDH1 wild type gliomas.

Reprogramming Transcription Factors Oct4 and Sox2 Induce a BRD-Dependent Immunosuppressive Transcriptome in GBM-Propagating Cells

A subset of stem-like cells in glioblastoma (GBM; GSC) underlies tumor propagation, therapeutic resistance, and tumor recurrence. Immune evasion is critical for GSCs to carry out these functions. However, the molecular mechanisms employed by GSCs to escape antitumor immunity remain largely unknown. The reprogramming transcription factors Oct4 and Sox2 function as core multipotency factors and play an essential role in the formation and maintenance of GSCs, but the roles of these transcription factors in GSC immune escape have not been well explored. Here we examine how Oct4/Sox2 coexpression contributes to the immunosuppressive phenotype of GSCs. Combined transcription profiling and functional studies of Oct4/Sox2 coexpressing GSCs and differentiated GBM cells demonstrated that Oct4 and Sox2 cooperatively induce an immunosuppressive transcriptome consisting of multiple immunosuppressive checkpoints (i.e., PD-L1, CD70, A2aR, TDO) and dysregulation of cytokines and chemokines that are associated with an immunosuppressive tumor microenvironment. Mechanistically, induction and function of BRD/H3k27Ac-dependent immunosuppressive genes played a role in the immunosuppressive phenotype of GSCs. Pan-BET bromodomain inhibitors (e.g., JQ1) and shBRD4 constructs significantly inhibited the immunosuppressive transcriptome and immunosuppressive biological responses induced by Oct4/Sox2. Our findings identify targetable mechanisms by which tumor-propagating GSCs contribute to the immunosuppressive microenvironment in GBM. SIGNIFICANCE: This report identifies mechanisms by which the reprogramming transcription factors Oct4 and Sox2 function to drive the immunomodulatory transcriptome of GSCs and contribute to the immunosuppressive microenvironment in GBM.

Frondoside A Inhibits an MYC-Driven Medulloblastoma Model Derived from Human-Induced Pluripotent Stem Cells

Medulloblastoma (MB) is the most common malignant pediatric brain tumor. MYC-driven MBs, commonly found in the group 3 MB, are aggressive and metastatic with the worst prognosis. Modeling MYC-driven MB is the foundation of therapeutic development. Here, we applied a synthetic mRNA-driven strategy to generate neuronal precursors from human-induced pluripotent stem cells (iPSCs). These neuronal precursors were transformed by the MYC oncogene combined with p53 loss of function to establish an MYC-driven MB model recapitulating the histologic and transcriptomic hallmarks of group 3 MB. We further show that the marine compound Frondoside A (FA) effectively inhibits this MYC-driven MB model without affecting isogenic neuronal precursors with undetectable MYC expression. Consistent results from a panel of MB models support that MYC levels are positively correlated with FA's antitumor potency. Next, we show that FA suppresses MYC expression and its downstream gene targets in MB cells, suggesting a potential mechanism underlying FA's inhibitory effects on MYC-driven cancers. In orthotopic xenografts of MYC-driven MB, intratumoral FA administration potently induces cytotoxicity in tumor xenografts, significantly extends the survival of tumor-bearing animals, and enhances the recruitment of microglia/macrophages and cytotoxic T lymphocytes to tumors. Moreover, we show that MYC levels also predict FA potency in glioblastoma and non-small cell lung cancer cells. Taken together, this study provides an efficient human iPSC-based strategy for personalizable cancer modeling, widely applicable to mechanistic studies (e.g., genetic predisposition to cancer) and drug discovery. Our preclinical results justify the clinical translation of FA in treating MYC-driven MB and other human cancers.

Association of high-sensitivity C-reactive protein and long-term mortality may differ from lipoprotein(a) levels among patients undergoing coronary angiography

Background

The use of high-sensitivity C-reactive protein (hs-CRP) as an inflammation biomarker in predicting long-term mortality remains controversial. We aimed to investigate whether the association of hs-CRP with long-term mortality differs from another inflammation biomarker, lipoprotein(a), in patients undergoing coronary angiography (CAG).

Methods

A total of 2422 patients undergoing CAG were included in the final analysis from a prospective, observational study. We divided them into 4 groups according to hs-CRP level (high ≥4.8 mg/l, low &lt;4.8 mg/l) and lipoprotein(a) level (high ≥17 mg/dl, low &lt;17 mg/dl).

Results

The overall incidence of all-cause long-term mortality was 133/2422 (5.5%). In the high lipoprotein(a) group, after adjusting for LDL-cholesterol concentration (LDL-C), age, sex, smoking status, diabetes mellitus and estimated glomerular filtration rate (eGFR), a high hs-CRP level was an independent predictor of all-cause long-term mortality (hazard ratio: 2.01; 95% CI: 1.13–3.54; p=0.02). In the low lipoprotein(a) group, a similar result was not found (hazard ratio: 1.42; 95% CI: 0.92–2.01; p=0.24).

Conclusions

Our data suggested that the association of hs-CRP with all-cause long-term mortality may differ from lipoprotein(a) levels among patients undergoing CAG. In addition to hs-CRP, a high lipoprotein(a) level might be a simultaneous intervention target for improving long-term prognosis in the future.

Funding Acknowledgement

Type of funding source: None

Genetic driver mutations introduced in identical cell-of-origin in murine glioblastoma reveal distinct immune landscapes but similar response to checkpoint blockade

Glioblastoma (GBM) is the most aggressive primary brain tumor. In addition to being genetically heterogeneous, GBMs are also immunologically heterogeneous. However, whether the differences in immune microenvironment are driven by genetic driver mutation is unexplored. By leveraging the versatile RCAS/tv-a somatic gene transfer system, we establish a mouse model for Classical GBM by introducing EGFRvIII expression in Nestin-positive neural stem/progenitor cells in adult mice. Along with our previously published Nf1-silenced and PDGFB-overexpressing models, we investigate the immune microenvironments of the three models of human GBM subtypes by unbiased multiplex profiling. We demonstrate that both the quantity and composition of the microenvironmental myeloid cells are dictated by the genetic driver mutations, closely mimicking what was observed in human GBM subtypes. These myeloid cells express high levels of the immune checkpoint protein PD-L1; however, PD-L1 targeted therapies alone or in combination with irradiation are unable to increase the survival time of tumor-bearing mice regardless of the driver mutations, reflecting the outcomes of recent human trials. Together, these results highlight the critical utility of immunocompetent mouse models for preclinical studies of GBM, making these models indispensable tools for understanding the resistance mechanisms of immune checkpoint blockade in GBM and immune cell-targeting drug discovery.

Unexpected cell type-dependent effects of autophagy on polyglutamine aggregation revealed by natural genetic variation in C. elegans

Background

Monogenic protein aggregation diseases, in addition to cell selectivity, exhibit clinical variation in the age of onset and progression, driven in part by inter-individual genetic variation. While natural genetic variants may pinpoint plastic networks amenable to intervention, the mechanisms by which they impact individual susceptibility to proteotoxicity are still largely unknown.

Results

We have previously shown that natural variation modifies polyglutamine (polyQ) aggregation phenotypes in C. elegans muscle cells. Here, we find that a genomic locus from C. elegans wild isolate DR1350 causes two genetically separable aggregation phenotypes, without changing the basal activity of muscle proteostasis pathways known to affect polyQ aggregation. We find that the increased aggregation phenotype was due to regulatory variants in the gene encoding a conserved autophagy protein ATG-5. The atg-5 gene itself conferred dosage-dependent enhancement of aggregation, with the DR1350-derived allele behaving as hypermorph. Surprisingly, increased aggregation in animals carrying the modifier locus was accompanied by enhanced autophagy activation in response to activating treatment. Because autophagy is expected to clear, not increase, protein aggregates, we activated autophagy in three different polyQ models and found a striking tissue-dependent effect: activation of autophagy decreased polyQ aggregation in neurons and intestine, but increased it in the muscle cells.

Conclusions

Our data show that cryptic natural variants in genes encoding proteostasis components, although not causing detectable phenotypes in wild-type individuals, can have profound effects on aggregation-prone proteins. Clinical applications of autophagy activators for aggregation diseases may need to consider the unexpected divergent effects of autophagy in different cell types.

TSPO deficiency induces mitochondrial dysfunction, leading to hypoxia, angiogenesis, and a growth-promoting metabolic shift toward glycolysis in glioblastoma

BACKGROUND

The ligands of mitochondrial translocator protein (TSPO) have been widely used as diagnostic biomarkers for glioma. However, the true biological actions of TSPO in vivo and its role in glioma tumorigenesis remain elusive.

METHODS

TSPO knockout xenograft and spontaneous mouse glioma models were employed to assess the roles of TSPO in the pathogenesis of glioma. A Seahorse Extracellular Flux Analyzer was used to evaluate mitochondrial oxidative phosphorylation and glycolysis in TSPO knockout and wild-type glioma cells.

RESULTS

TSPO deficiency promoted glioma cell proliferation in vitro in mouse GL261 cells and patient-derived stem cell-like GBM1B cells. TSPO knockout increased glioma growth and angiogenesis in intracranial xenografts and a mouse spontaneous glioma model. Loss of TSPO resulted in a greater number of fragmented mitochondria, increased glucose uptake and lactic acid conversion, decreased oxidative phosphorylation, and increased glycolysis.

CONCLUSION

TSPO serves as a key regulator of glioma growth and malignancy by controlling the metabolic balance between mitochondrial oxidative phosphorylation and glycolysis.1. TSPO deficiency promotes glioma growth and angiogenesis.2. TSPO regulates the balance between mitochondrial oxidative phosphorylation and glycolysis.

Carbon Dots as a New Class of Diamagnetic Chemical Exchange Saturation Transfer (diaCEST) MRI Contrast Agents

While carbon dots (C-dots) have been extensively investigated pertaining to their fluorescent, phosphorescent, electrochemiluminescent, optoelectronic, and catalytic features, their inherent chemical exchange saturation transfer magnetic resonance imaging (CEST MRI) properties are unknown. By virtue of their hydrophilicity and abundant exchangeable protons of hydroxyl, amine, and amide anchored on the surface, we report here that C-dots can be adapted as effective diamagnetic CEST (diaCEST) MRI contrast agents. As a proof-of-concept demonstration, human glioma cells were labeled with liposomes with or without encapsulated C-dots and implanted in mouse brain. In vivo CEST MRI was able to clearly differentiate labeled cells from non-labeled cells. The present findings may encourage new applications of C-dots for in vivo imaging in deep tissues, which is currently not possible using conventional fluorescent (near-infrared) C-dots.

Abstract 2608: EGF signaling activates a TAZ-driven oncogenic program in glioblastoma

Glioblastoma multiforme (GBM) is the most aggressive and lethal primary brain tumor in humans. Hyperactivation of the signaling pathway driven by the epidermal growth factor (EGF) and its receptor (EGFR) are commonly occurring in GBM. The oncogenic transcriptional program driven by EGF signaling is still incompletely understood in GBM. Here, we found that EGF induces the upregulation and nuclear translocation of TAZ, an oncogenic transcriptional co-activator. TAZ and its paralog gene YAP are commonly known as downstream mediators of the Hippo signaling pathway. TAZ has been found as a driver of mesenchymal transition in GBM cells and promotes GBM radioresistance. Our results support that EGF induces TAZ transcription and the activation of TAZ gene targets, through the signaling axis including EGFR, STAT3 and ERK. EGFRvIII is the most frequently occurring EGFR mutation in GBM causing constitutively active EGFR. We found that EGFRvIII causes EGF-independent activation of TAZ and its downstream oncogenic targets. Next, we used next-generation sequencing to establish a genome-wide map of TAZ gene targets in GBM cells after EGF stimulation. The results suggest that EGF signaling activates a TAZ-driven oncogenic program including autocrine and paracrine factors that promote GBM growth, angiogenesis, stemness and immunoescape. Moreover, we found that TAZ targeting by shRNAs or the FDA-approved drug Verteporfin effectively inhibits the TAZ-driven oncogenic program activated by EGF stimulation or the EGFRvIII mutant. TAZ targeting also inhibits GBM cell growth and xenograft formation. In contrast, enforced TAZ induces the TAZ-driven oncogenic program and promotes GBM cell growth and xenograft formation. In conclusion, our results reveal a novel TAZ-driven oncogenic program that is activated by EGF signaling in GBM. Our discoveries strongly support TAZ as a therapeutic target for GBM and likely other human cancer with hyperactivation of EGF signaling. Our preclinical studies also provide a clinically translatable strategy for GBM therapy based on using the FDA-approved drug Verteporfin.

Citation Format: Minling Gao, Yi Fu, Laterra John, Mingyao Ying. EGF signaling activates a TAZ-driven oncogenic program in glioblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2608.

Extracellular Matrix Protein Tenascin C Increases Phagocytosis Mediated by CD47 Loss of Function in Glioblastoma

Glioblastomas (GBM) are highly infiltrated by myeloid-derived innate immune cells that contribute to the immunosuppressive nature of the brain tumor microenvironment (TME). CD47 has been shown to mediate immune evasion, as the CD47-SIRPα axis prevents phagocytosis of tumor cells by macrophages and other myeloid cells. In this study, we established CD47 homozygous deletion (CD47^-/-) in human and mouse GBM cells and investigated the impact of eliminating the "don't eat me" signal on tumor growth and tumor-TME interactions. CD47 knockout (KO) did not significantly alter tumor cell proliferation in vitro but significantly increased phagocytosis of tumor cells by macrophages in cocultures. Compared with CD47 wild-type xenografts, orthotopic xenografts derived from CD47^-/- tumor cells grew significantly slower with enhanced tumor cell phagocytosis and increased recruitment of M2-like tumor-associated microglia/macrophages (TAM). CD47 KO increased tumor-associated extracellular matrix protein tenascin C (TNC) in xenografts, which was further examined in vitro. CD47 loss of function upregulated TNC expression in tumor cells via a Notch pathway-mediated mechanism. Depletion of TNC in tumor cells enhanced the growth of CD47^-/- xenografts in vivo and decreased the number of TAM. TNC knockdown also inhibited phagocytosis of CD47^-/- tumor cells in cocultures. Furthermore, TNC stimulated release of proinflammatory factors including TNFα via a Toll-like receptor 4 and STAT3-dependent mechanism in human macrophage cells. These results reveal a vital role for TNC in immunomodulation in brain tumor biology and demonstrate the prominence of the TME extracellular matrix in affecting the antitumor function of brain innate immune cells. SIGNIFICANCE: These findings link TNC to CD47-driven phagocytosis and demonstrate that TNC affects the antitumor function of brain TAM, facilitating the development of novel innate immune system-based therapies for brain tumors.

Synthetic mRNAs Drive Highly Efficient iPS Cell Differentiation to Dopaminergic Neurons

Proneural transcription factors (TFs) drive highly efficient differentiation of pluripotent stem cells to lineage-specific neurons. However, current strategies mainly rely on genome-integrating viruses. Here, we used synthetic mRNAs coding two proneural TFs (Atoh1 and Ngn2) to differentiate induced pluripotent stem cells (iPSCs) into midbrain dopaminergic (mDA) neurons. mRNAs coding Atoh1 and Ngn2 with defined phosphosite modifications led to higher and more stable protein expression, and induced more efficient neuron conversion, as compared to mRNAs coding wild-type proteins. Using these two modified mRNAs with morphogens, we established a 5-day protocol that can rapidly generate mDA neurons with >90% purity from normal and Parkinson's disease iPSCs. After in vitro maturation, these mRNA-induced mDA (miDA) neurons recapitulate key biochemical and electrophysiological features of primary mDA neurons and can provide high-content neuron cultures for drug discovery. Proteomic analysis of Atoh1-binding proteins identified the nonmuscle myosin II (NM-II) complex as a new binding partner of nuclear Atoh1. The NM-II complex, commonly known as an ATP-dependent molecular motor, binds more strongly to phosphosite-modified Atoh1 than the wild type. Blebbistatin, an NM-II complex antagonist, and bradykinin, an NM-II complex agonist, inhibited and promoted, respectively, the transcriptional activity of Atoh1 and the efficiency of miDA neuron generation. These findings established the first mRNA-driven strategy for efficient iPSC differentiation to mDA neurons. We further identified the NM-II complex as a positive modulator of Atoh1-driven neuron differentiation. The methodology described here will facilitate the development of mRNA-driven differentiation strategies for generating iPSC-derived progenies widely applicable to disease modeling and cell replacement therapy. Stem Cells Translational Medicine 2019;8:112&12.

Krüppel-like factor 9 and histone deacetylase inhibitors synergistically induce cell death in glioblastoma stem-like cells

Background

The dismal prognosis of patients with glioblastoma (GBM) is attributed to a rare subset of cancer stem cells that display characteristics of tumor initiation, growth, and resistance to aggressive treatment involving chemotherapy and concomitant radiation. Recent research on the substantial role of epigenetic mechanisms in the pathogenesis of cancers has prompted the investigation of the enzymatic modifications of histone proteins for therapeutic drug targeting. In this work, we have examined the function of Krüppel-like factor 9 (KLF9), a transcription factor, in chemotherapy sensitization to histone deacetylase inhibitors (HDAC inhibitors).

Methods

Since GBM neurosphere cultures from patient-derived gliomas are enriched for GBM stem-like cells (GSCs) and form highly invasive and proliferative xenografts that recapitulate the features demonstrated in human patients diagnosed with GBM, we established inducible KLF9 expression systems in these GBM neurosphere cells and investigated cell death in the presence of epigenetic modulators such as histone deacetylase (HDAC) inhibitors.

Results

We demonstrated that KLF9 expression combined with HDAC inhibitor panobinostat (LBH589) dramatically induced glioma stem cell death via both apoptosis and necroptosis in a synergistic manner. The combination of KLF9 expression and LBH589 treatment affected cell cycle by substantially decreasing the percentage of cells at S-phase. This phenomenon is further corroborated by the upregulation of cell cycle inhibitors p21 and p27. Further, we determined that KLF9 and LBH589 regulated the expression of pro- and anti- apoptotic proteins, suggesting a mechanism that involves the caspase-dependent apoptotic pathway. In addition, we demonstrated that apoptosis and necrosis inhibitors conferred minimal protective effects against cell death, while inhibitors of the necroptosis pathway significantly blocked cell death.

Conclusions

Our findings suggest a detailed understanding of how KLF9 expression in cancer cells with epigenetic modulators like HDAC inhibitors may promote synergistic cell death through a mechanism involving both apoptosis and necroptosis that will benefit novel combinatory antitumor strategies to treat malignant brain tumors.

[Factors affecting stability after fixed orthodontic treatment]

Objective: To analyze factors affecting stability after fixed orthodontic treatment. Methods: Five hundred and forty-four patients who had finished fixed orthodontic treatment more than two years in First Department of Orthodontics, China Medical University from January, 2000 to December, 2017 were investigated and the rate of regular revisit was counted. The data of 288 patients were successfully collected by calling or sending text messages and the rate of standard use of retainers as prescribed (patients wore retainers for 24 months or longer) was counted. According to the variation of peer assessment rating (PAR) index at the start of retention and the time the data collected, the patients were divided into relapse group (variation of PAR index >5) and non-relapse group (variation of PAR index ≤5). Difference significance analysis and multiple-factor logistic regression analysis were used. Sixty patients wearing retainers well were collected and the curative effects of Hawley retainer and vacuum formed retainer (VFR) were compared, which included overbite, overjet, maxillary irregularity index, mandibular irregularity index, width betwenn canine and width between first molar. Results: The rate of regular revisit was 41.0% (223/544). Two hundred and one of 288 patients (69.8%) who were visited successfully had regular revisit, and 60.4%(174/288) of the patients wore retainers well; 30.2% (87/288) of the patients who were visited successfully didn't have regular revisit, and 10.4% (30/288) of the patients wore retainers well. Difference significance analysis showed that there was highly significant difference between relapse group and non-relapse group in the type of retainer and duration of retention (P<0.01). One hundred and forty of 224 patients (62.5%) in non-relapse group and 37.5% (24/64) of the patients in relapse group used VFR, and the duration of retention in non-relapse group was significantly longer than that in relapse group (P<0.01). Multiple-factor Logistic regression analysis showed that wearing Hawley retainers (OR=3.067, P<0.05) was the risk factor influencing relapse. The duration of retention (OR=0.832, P<0.01) was the protective factor influencing relapse. Independent-sample t test indicated that the variations of maxillary [(0.82±0.36) mm] and mandibular [(1.05±0.22) mm] irregularity index in Hawley retainer group were larger than maxillary [(0.64±0.29) mm] and mandibular [(0.72±0.35) mm)] irregularity index in VFR group, respectively. The differences between the two groups were significant (P<0.05). Conclusions: Duration of retention was implicated in stability after orthodontic treatment. VFR had better effect in the aspects of irregularity index than Hawley retainer.

Krüppel-like factor 4 (KLF4) induces mitochondrial fusion and increases spare respiratory capacity of human glioblastoma cells

Krüppel-like factor 4 (KLF4) is a zinc finger transcription factor critical for the regulation of many cellular functions in both normal and neoplastic cells. Here, using human glioblastoma cells, we investigated KLF4's effects on cancer cell metabolism. We found that forced KLF4 expression promotes mitochondrial fusion and induces dramatic changes in mitochondrial morphology. To determine the impact of these changes on the cellular functions following, we analyzed how KLF4 alters glioblastoma cell metabolism, including glucose uptake, glycolysis, pentose phosphate pathway, and oxidative phosphorylation. We did not identify significant differences in baseline cellular metabolism between control and KLF4-expressing cells. However, when mitochondrial function was impaired, KLF4 significantly increased spare respiratory capacity and levels of reactive oxygen species in the cells. To identify the biological effects of these changes, we analyzed proliferation and survival of control and KLF4-expressing cells under stress conditions, including serum and nutrition deprivation. We found that following serum starvation, KLF4 altered cell cycle progression by arresting the cells at the G2/M phase and that KLF4 protected cells from nutrition deprivation-induced death. Finally, we demonstrated that methylation-dependent KLF4-binding activity mediates mitochondrial fusion. Specifically, the downstream targets of KLF4-mCpG binding, guanine nucleotide exchange factors, serve as the effector of KLF4-induced mitochondrial fusion, cell cycle arrest, and cell protection. Our experimental system provides a robust model for studying the interactions between mitochondrial morphology and function, mitochondrial dynamics and metabolism, and mitochondrial fusion and cell death during tumor initiation and progression.

The Effects of Quinine on Neurophysiological Properties of Dopaminergic Neurons

Quinine is an antimalarial drug that is toxic to the auditory system by commonly inducing hearing loss and tinnitus, presumably due to its ototoxic effects on disruption of cochlear hair cells and blockade of ion channels of neurons in the auditory system. To a lesser extent, quinine also causes ataxia, tremor, and dystonic reactions. As dopaminergic neurons are implicated to play a role in all of these diseases, we tested the toxicity of quinine on induced dopaminergic (iDA) neurons derived from human pluripotent stem cells (iPSCs) and primary dopaminergic (DA) neurons of substantia nigra from mice brain slices. Patch clamp recordings and combined drug treatments were performed to examine key physiological properties of the DA neurons. We found that quinine (12.5-200 μM) depolarized the resting membrane potential and attenuated the amplitudes of rebound spikes induced by hyperpolarization. Action potentials were also broadened in spontaneously spiking neurons. In addition to quinine attenuating hyperpolarization-dependent conductance, the tail currents following withdrawal of hyperpolarizing currents were also attenuated. Taken together, we found that iPSC-derived DA neurons recapitulated all the tested physiological properties of human DA neurons, and quinine had distinct effects on the physiology of both iDA and primary DA neurons. This toxicity of quinine may be the underlying mechanism for the movement disorders of cinchonism or quinism and may play a role in tinnitus modulation.

Genome-wide prediction of DNase I hypersensitivity using gene expression

We evaluate the feasibility of using a biological sample's transcriptome to predict its genome-wide regulatory element activities measured by DNase I hypersensitivity (DH). We develop BIRD, Big Data Regression for predicting DH, to handle this high-dimensional problem. Applying BIRD to the Encyclopedia of DNA Elements (ENCODE) data, we found that to a large extent gene expression predicts DH, and information useful for prediction is contained in the whole transcriptome rather than limited to a regulatory element's neighboring genes. We show applications of BIRD-predicted DH in predicting transcription factor-binding sites (TFBSs), turning publicly available gene expression samples in Gene Expression Omnibus (GEO) into a regulome database, predicting differential regulatory element activities, and facilitating regulome data analyses by serving as pseudo-replicates. Besides improving our understanding of the regulome-transcriptome relationship, this study suggests that transcriptome-based prediction can provide a useful new approach for regulome mapping.

Abstract 5833: Targeting the transcription co-activator TAZ inhibits MYC-driven medulloblastoma

Medulloblastoma (MB), the most common malignant pediatric brain tumor, results in significant neurological, intellectual and physical disability or death. Four MB subtypes (WNT, SHH, Group 3 and 4) have recently been identified. Group 3 MB, the most aggressive subtype, is more frequently associated with gene amplification and/or protein overexpression of the MYC (c-Myc) oncogene, hereby referred to as MYC-driven MBs. It is still unclear how MB cells activate and maintain high MYC expression, as only a small portion of MYC-high MBs is caused by MYC genomic amplification. MYC-targeted MB therapies are also lacking. Targeting MYC upstream activators is a promising strategy for inhibiting MYC-driven MBs, when compared to direct MYC inhibition that is still challenging. Here, we focus on the transcription co-activator TAZ, a novel MYC upstream activator and a potential therapeutic target for inhibiting MYC-driven MBs. TAZ (transcriptional co-activator with PDZ-binding motif) is an oncogenic driver in multiple human cancers. TAZ and its paralog YAP form complexes with other transcription factors, such as TEAD, to activate downstream gene targets. TAZ and YAP are transcriptional effectors of various signaling pathways, such as the Hippo pathway. We found for the first time that TAZ is an essential MYC activator in MB cells. TAZ but not its paralog YAP is highly expressed in MYC-amplified MB cells and their xenografts. TAZ silencing downregulates MYC and inhibits MB cell proliferation. Enforced TAZ expression induces MYC expression in MB cells and promotes MB cell growth. We further showed that TAZ forms complex with transcription activator TEAD to bind to and transactivate MYC enhancers. For pharmacological TAZ targeting, we found that the FDA-approved drug Verteporfin (VP) inhibits TAZ-TEAD interaction, suppresses MYC expression and inhibits MB cell tumor propagation in vivo. We have also developed a nanoparticle formulation by using DSPE-mPEG2000 micelles to achieve VP delivery cross the blood-brain barrier in mice bearing brain tumor xenografts. In summary, our results provide novel insights into MYC upstream activators in MB, and also identify TAZ as a potential therapeutic target for inhibiting MYC-driven MBs. This knowledge may also be widely applicable to other TAZ/MYC-expressing human cancers, such as glioblastoma. Moreover, our studies support the effectiveness of VP treatment in pre-clinical MB models. These results and also the nanocarrier system for systemic VP delivery provide a solid foundation for VP clinical trials in patients with MB and likely other MYC-driven cancers.

Note: This abstract was not presented at the meeting.

Citation Format: Yingchao Xue, Mingyao Ying. Targeting the transcription co-activator TAZ inhibits MYC-driven medulloblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5833. doi:10.1158/1538-7445.AM2017-5833

Methylated cis-regulatory elements mediate KLF4-dependent gene transactivation and cell migration

Altered DNA methylation status is associated with human diseases and cancer; however, the underlying molecular mechanisms remain elusive. We previously identified many human transcription factors, including Krüppel-like factor 4 (KLF4), as sequence-specific DNA methylation readers that preferentially recognize methylated CpG (mCpG), here we report the biological function of mCpG-dependent gene regulation by KLF4 in glioblastoma cells. We show that KLF4 promotes cell adhesion, migration, and morphological changes, all of which are abolished by R458A mutation. Surprisingly, 116 genes are directly activated via mCpG-dependent KLF4 binding activity. In-depth mechanistic studies reveal that recruitment of KLF4 to the methylated cis-regulatory elements of these genes result in chromatin remodeling and transcription activation. Our study demonstrates a new paradigm of DNA methylation-mediated gene activation and chromatin remodeling, and provides a general framework to dissect the biological functions of DNA methylation readers and effectors.

Inhibition of neuronal ferroptosis protects hemorrhagic brain

Intracerebral hemorrhage (ICH) causes high mortality and morbidity, but our knowledge of post-ICH neuronal death and related mechanisms is limited. In this study, we first demonstrated that ferroptosis, a newly identified form of cell death, occurs in the collagenase-induced ICH model in mice. We found that administration of ferrostatin-1, a specific inhibitor of ferroptosis, prevented neuronal death and reduced iron deposition induced by hemoglobin in organotypic hippocampal slice cultures (OHSCs). Mice treated with ferrostatin-1 after ICH exhibited marked brain protection and improved neurologic function. Additionally, we found that ferrostatin-1 reduced lipid reactive oxygen species production and attenuated the increased expression level of PTGS2 and its gene product cyclooxygenase-2 ex vivo and in vivo. Moreover, ferrostatin-1 in combination with other inhibitors that target different forms of cell death prevented hemoglobin-induced cell death in OHSCs and human induced pluripotent stem cell-derived neurons better than any inhibitor alone. These results indicate that ferroptosis contributes to neuronal death after ICH, that administration of ferrostatin-1 protects hemorrhagic brain, and that cyclooxygenase-2 could be a biomarker of ferroptosis. The insights gained from this study will advance our knowledge of the post-ICH cell death cascade and be essential for future preclinical studies.

Regulation of Glioblastoma Tumor-Propagating Cells by the Integrin Partner Tetraspanin CD151

Glioblastoma (GBM) stem cells (GSCs) represent tumor-propagating cells with stem-like characteristics (stemness) that contribute disproportionately to GBM drug resistance and tumor recurrence. Understanding the mechanisms supporting GSC stemness is important for developing therapeutic strategies for targeting GSC-dependent oncogenic mechanisms. Using GBM-derived neurospheres, we identified the cell surface tetraspanin family member CD151 as a novel regulator of glioma cell stemness, GSC self-renewal capacity, migration, and tumor growth. CD151 was found to be overexpressed in GBM tumors and GBM neurospheres enriched in GSCs. Silencing CD151 inhibited neurosphere forming capacity, neurosphere cell proliferation, and migration and attenuated the expression of markers and transcriptional drivers of the GSC phenotype. Conversely, forced CD151 expression promoted neurosphere self-renewal, cell migration, and expression of stemness-associated transcription factors. CD151 was found to complex with integrins α3, α6, and β1 in neurosphere cells, and blocking CD151 interactions with integrins α3 and α6 inhibited AKT phosphorylation, a downstream effector of integrin signaling, and impaired sphere formation and neurosphere cell migration. Additionally, targeting CD151 in vivo inhibited the growth of GBM neurosphere-derived xenografts. These findings identify CD151 and its interactions with integrins α3 and α6 as potential therapeutic targets for inhibiting stemness-driving mechanisms and stem cell populations in GBM.

A Comparison of the Diagnostic Accuracy and Reliability of Subjective Grading and Computer-Aided Assessment of Intranodal Vascularity in Differentiating Metastatic and Reactive Cervical Lymphadenopathy

PURPOSE

Ultrasound is a well-established imaging modality in the assessment of malignant cervical lymphadenopathy. With the use of Doppler ultrasound, intranodal vascularity can be evaluated. However, the major limitation of ultrasound is operator dependency. Therefore, this study aimed to evaluate and compare the diagnostic accuracy and reliability of the subjective grading and computer-aided approach in assessing intranodal vascularity for the differentiation of benign and malignant lymph nodes.

MATERIALS AND METHODS

The present study retrospectively assessed 99 power Doppler ultrasound images of cervical lymph nodes and evaluated the degree of intranodal vascularity using qualitative subjective grading (QSG) and quantitative computer-aided (QCA) methods. The diagnostic accuracy of the two methods in distinguishing metastatic and reactive nodes and their inter- and intra-rater reliability in assessing intranodal vascularity were evaluated and compared.

RESULTS

The results showed that the QCA method was more accurate than the QSG method with a significantly higher sensitivity (67.8 % and 61.9 %, respectively, p < 0.05) and specificity (73.3 % and 57.3 %, respectively, p < 0.05). Using the intranodal vascularity index as determined by the QCA approach, the optimum cut-off to differentiate metastatic and reactive cervical lymph nodes was 32 %. The QCA method showed higher inter- and intra-rater reliability than the QSG method.

CONCLUSION

In the assessment of the degree of intranodal vascularity, the QCA method was more accurate and reliable than the QSG method in distinguishing metastatic and reactive lymph nodes.

Abstract 2892: A MYC-driven medulloblastoma model derived from human induced pluripotent stem cells

Brain tumors are the most common cause of childhood oncological death, and medulloblastoma (MB) is the most common malignant pediatric brain tumor. Current MB treatments yield five-year survival rates of 60-70%, but usually result in significant neurological, intellectual and physical disabilities. Recent gene expression studies have identified four MB subgroups, many of which have unique clinical and histopathological features. Patients with Group 3 MB are more likely to have aggressive and invasive tumors with large cell/anaplastic histology, and have the worst prognosis. Group 3 MB is characterized by amplification and overexpression oncogenic transcription factor MYC, herein referred to as MYC-driven MB. Modeling MYC-driven MB is critical for developing and testing potential therapies for this highly aggressive MB. Recently, murine MYC-driven MB models have been developed using mouse neural stem cells (NSCs) or neuronal precursor cells (NPCs). But human MB models derived from individual-specific cells are still lacking. Human induced pluripotent stem cells (iPSCs) can be differentiated into various types of cells and hold great promise for developing individual-specific disease models. It is valuable to develop MB models using human iPSCs from both MB patients and unaffected persons. In comparison with mouse-cell-derived MB models, human-iPSC-derived MB models will provide a unique and high-impact platform not only for personalized drug discovery but also for studying the role of individual's distinctive genetic background in carcinogen sensitivity and MB susceptibility. Transcription factor Atoh1 governs the development of cerebellar granule neurons and is essential for MB formation. Here, we induced Atoh1 in human iPSCs to differentiate these cells into NPCs. We further infected these Atoh1-induced NPCs with lentiviruses encoding a stabilized form of MYC (MYCT58A) and dominant-negative p53 (DNp53). These NPCs generated aggressive tumors after being transplanted into mouse cerebellum. NPCs infected by DNp53 alone did not form tumors after 90 days. These MYC-driven tumors were comprised of poorly differentiated, medium to large size cells which showed nuclear molding, prominent nucleoli and numerous mitotic (Ki67+) and apoptotic (Cleaved-Caspase-3+) cells. These tumors also expressed early neuronal lineage marker (β-tubulin III). All these features closely mimic human Group 3 MB. Moreover, we also established neurosphere cultures from these MYC-driven tumors to enrich cancer stem-like cells that have the capability for long-term self-renewal and tumor initiation upon serial transplantations. In summary, we established a novel human-iPSC-drived cancer model for modeling MYC-driven MB. Our results support the feasibility to recapitulate human cancers using progenies derived from human iPSCs. The iPSC-derived MB model we established will facilitate mechanistic studies and drug testing for human aggressive MB.

Citation Format: Jonathan Sagal, Charles G. Eberhart, Mingyao Ying. A MYC-driven medulloblastoma model derived from human induced pluripotent stem cells. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2892. doi:10.1158/1538-7445.AM2015-2892

A novel recurrent CHEK2 Y390C mutation identified in high-risk Chinese breast cancer patients impairs its activity and is associated with increased breast cancer risk

Certain predisposition factors such as BRCA1/2 and CHEK2 mutations cause familial breast cancers that occur early. In China, breast cancers are diagnosed at relatively younger age, and higher percentage of patients are diagnosed before 40 years, than that in Caucasians. However, the prevalence for BRCA1/2 mutations and reported CHEK2 germline mutations is much lower or absent in Chinese population, arguing for the need to study other novel risk alleles among Chinese breast cancer patients. In this study, we searched for CHEK2 mutations in young, high-risk breast cancer patients in China and detected a missense variant Y390C (1169A > G) in 12 of 150 patients (8.0%) and 2 in 250 healthy controls (0.8%, P = 0.0002). Four of the Y390C carriers have family history of breast and/or ovarian cancer. In patients without family history, Y390C carriers tend to develop breast cancer early, before 35 years of age. The codon change at Y390, a highly conserved residue located in CHEK2's kinase domain, appeared to significantly impair CHEK2 activity. Functional analysis suggested that the CHEK2 Y390C mutation is deleterious as judged by the mutant protein's inability to inactivate CDC25A or to activate p53 after DNA damage. Cells expressing the CHEK2 Y390C variant showed impaired p21 and Puma expression after DNA damage, and the deregulated cell cycle checkpoint and apoptotic response may help conserve mutations and therefore contribute to tumorigeneisis. Taken together, our results not only identified a novel CHEK2 allele that is associated with cancer families and confers increased breast cancer risk, but also showed that this allele significantly impairs CHEK2 function during DNA damage response. Our results provide further insight on how the function of such an important cancer gene may be impaired by existing mutations to facilitate tumorigenesis. It also offers a new subject for breast cancer monitoring, prevention and management.

Kruppel-like factor-9 (KLF9) inhibits glioblastoma stemness through global transcription repression and integrin α6 inhibition

It is increasingly important to understand the molecular basis for the plasticity of neoplastic cells and their capacity to transition between differentiated and stemlike phenotypes. Kruppel-like factor-9 (KLF9), a member of the large KLF transcription factor family, has emerged as a regulator of oncogenesis, cell differentiation, and neural development; however, the molecular basis for the diverse contextual functions of KLF9 remains unclear. This study focused on the functions of KLF9 in human glioblastoma stemlike cells. We established for the first time a genome-wide map of KLF9-regulated targets in human glioblastoma stemlike cells and show that KLF9 functions as a transcriptional repressor and thereby regulates multiple signaling pathways involved in oncogenesis and stem cell regulation. A detailed analysis of one such pathway, integrin signaling, showed that the capacity of KLF9 to inhibit glioblastoma cell stemness and tumorigenicity requires ITGA6 repression. These findings enhance our understanding of the transcriptional networks underlying cancer cell stemness and differentiation and identify KLF9-regulated molecular targets applicable to cancer therapeutics.

Abstract 3014: Hyaluronan-mediated motility receptor maintains stemness and tumorigenic potential of glioblastoma stem cells

Glioblastoma (GBM) stem cells (GSCs) are a subpopulation of tumor cells that display stem-like characteristics (stemness) and play unique roles in tumor propagation, therapeutic resistance and tumor recurrence. It is becoming increasingly important to identify novel therapeutic targets in GSC for anti-GBM therapies. Here, we demonstrate that hyaluronan-mediated motility receptor (HMMR) is hyper-expressed in GBM tumors and supports the self-renewal and tumorigenic potential of GSCs. HMMR silencing impairs GSC self-renewal and inhibits the expression of GSC markers and regulators. HMMR silencing suppresses GSC-derived tumor growth and extends the survival of mice bearing GSC xenografts. HMMR overexpression promotes GSC self-renewal and intracranial tumor propagation. In human GBM tumor specimens, HMMR expression is positively correlated with the expression of cell-stemness-associated markers and regulators. Our findings identify HMMR as a potential therapeutic target for inhibiting GSCs, suggesting therapeutic applications against GBM.

Citation Format: Jessica Tilghman, John Laterra, Mingyao Ying. Hyaluronan-mediated motility receptor maintains stemness and tumorigenic potential of glioblastoma stem cells. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3014. doi:10.1158/1538-7445.AM2014-3014