bluuebunny/crossref_metadata_2025 huggingface dataset:
CMR—basic principles
Authors: Bogaert Jan , Symons Rolf , Wright Jeremy
Published: June 2021

Cardiac magnetic resonance imaging (CMR) has rapidly evolved to become the modality of choice in the evaluation of a wide spectrum of cardiovascular disorders. This is mostly related to its multiparametric approach where the different features such as morphology (including deep tissue characterization), function, perfusion can be non-invasively studied using a series of (different) pulse sequences. Therefore, CMR may provide a ‘one stop shop’ approach to cardiac patients offering a complete cardiac evaluation by a single modality without the use of ionizing radiation. However, to maximize its clinical use, not all pulse sequences should be used in every patient. Moreover, minimizing time spent in the magnetic resonance imaging (MRI) machine is desirable in critically ill, unstable patients. Therefore, experienced cardiac imagers from radiology and cardiology should be present to provide on-site real-time assessment of the images and to determine which pulse sequences are necessary each patient. In this fashion, a complete CMR exam should be obtainable in less than 30 minutes for the vast majority of patients. The aim of this chapter is to describe the physics and practical aspects of CMR and then explore the available pulse sequences, so that the clinical utility of CMR can be maximized.
Assessment of myocardial function by speckle-tracking echocardiography
Authors: Edvardsen Thor , Klaeboe Lars Gunnar , Szymczyk Ewa , Kasprzak Jarosław D.
Published: June 2021

Myocardial deformation or strain is the universal property of contracting cardiac muscle. Deformation is defined in physics as relative change of length (and is therefore unitless and usually given as percentage) and in cardiac imaging it is thus algebraically negative for shortening or positive for thickening. There are several definitions of strain—Lagrangian strain refers to a fixed baseline distance and Eulerian (or natural) strain—to a dynamically changing reference length, representing a time integral of strain rate (which can be obtained by tissue Doppler). Measurements of strains are usually obtained by greyscale image quantification modality—speckle-tracking echocardiography (STE) which analyses myocardial motion by tracking and matching naturally occurring markers of myocardial texture, described as speckles. Echocardiographic speckles represent interference pattern of subtle myocardial scatters and can be followed from frame to frame by dedicated software to define the displacement of the myocardium within the interval between consecutive frames (inverse of frame rate).
New technical developments in nuclear cardiology and hybrid imaging
Authors: Saraste Antti , Dorbala Sharmila , Knuuti Juhani
Published: June 2021

Cardiac hybrid imaging offers the ability to combine strengths of different imaging modalities in providing information on cardiac physiology along with cardiac and coronary anatomy. Hybrid images contain two data sets combined into a fused image in which both data sets contribute important information. Hybrid coronary computed tomography angiography and nuclear or magnetic resonance myocardial perfusion imaging has been shown to accurately detect coronary artery disease. Emerging clinical applications of cardiac hybrid imaging include evaluation of myocardial viability, cardiac or vascular inflammation, infection, and cardiac infiltration. Cardiac dedicated single photon emission computed tomography scanners, novel software methods for low count image reconstruction, and quantification of myocardial blood flow by positron emission tomography (PET) have potential to lower radiation dose associated with cardiac imaging while maintaining high diagnostic accuracy for the detection of coronary artery disease.
Mitral valve stenosis
Authors: Peters Ferande , Brochet Eric
Published: June 2021

Mitral stenosis is an important valvular lesion that when encountered both in the developing world and the developed world requires accurate assessment. The mitral valve area is the key parameter that should be used to assess severity. Morphological assessment of the entire valve apparatus is required to identify rheumatic versus non-rheumatic aetiology as well the subgroup of patients who may benefit from percutaneous mitral commisurotomy. Three-dimensional transthoracic and transoesophageal echocardiography provide additive qualitative and quantitative data to the aforementioned key imaging requirements. Tomographic imaging (CT/MRI) are mainly utilized when echocardiography is not feasible. Imaging techniques are vital to aid diagnosis and explore therapeutic options in degenerative mitral stenosis but require further refinement with regard to accuracy of diagnosis and selection of optimal quantitative techniques.
Mitral valve regurgitation
Authors: Muñoz Daniel Rodríguez , Yiangou Kyriakos , Zamorano José Luis
Published: June 2021

The prevalence of mitral regurgitation (MR) is increasing in Western countries, which results in making it the second most frequent valvular heart disease requiring surgery. MR can be classified as primary (organic) or secondary (functional). Causes of primary MR consist of leaflet lesions, either degenerative changes (Barlow’s disease, fibroelastic degeneration, and annular calcification), rheumatic disease, or infective endocarditis. Causes of secondary MR consist of those that produce geometrical distortion of the subvalvular apparatus due to dilatation and remodelling of the left ventricle such as ischaemic heart disease and cardiomyopathies. The implementation of mitral valve repair as well as the rise of new transcatheter techniques, provided that are performed in experienced, high volume centres with the contribution of a valvular heart team, have impressively changed the prognosis of patients with severe MR. This has set new frontiers in the management of MR and has upgraded the role of imaging, creating new responsibilities, since its presence in every step of the procedure either preoperatively (quantification of MR, determination of the underlying mechanisms, investigation of reparability, determination of prognosis) or intra- and postoperatively, has been declared as fundamental.
Endocarditis
Authors: Muñoz Daniel Rodríguez , del Castillo Álvaro Marco
Published: June 2021

Cardiac imaging is the cornerstone in the diagnosis of endocarditis. It plays a key role in the confirmation of the diagnosis, location, and extension of the disease, as well as on the evaluation of associated lesions that directly impact treatment options. Echocardiography, both transthoracic and transoesophageal, are the main tools in the diagnostic process. However, alternative imaging techniques have emerged to compensate some of their pitfalls. In this chapter, we review the potential findings as well as the advantages and limitations of each technique. A correct understanding of the information they can provide is essential both for the clinical cardiologist and the specialist in cardiac imaging.
Transcatheter aortic valve implantation
Authors: Ng Arnold C.T. , Delgado Victoria , Bax Jeroen J.
Published: June 2021

Transcatheter aortic valve implantation (TAVI) is an established therapy for patients with symptomatic severe aortic stenosis and contraindications for surgical aortic valve replacement or with intermediate and high operative risk in whom the heart team considers that TAVI is the best therapeutic option. Accurate patient selection strongly relates on multimodality imaging consisting mostly of the combination of transthoracic echocardiography and computed tomography. To guide the procedure, fluoroscopy is the mainstay imaging modality. In the follow-up of the patients, transthoracic echocardiography and computed tomography are again the main imaging modalities to use. Cardiovascular magnetic resonance and nuclear imaging have a minimal role in this area.
Transcatheter mitral valve interventions
Authors: Wunderlich Nina C. , Siegel Robert J. , Rajani Ronak , Flint Nir
Published: June 2021

The past decade has been a revolution in the use of percutaneous procedures for mitral valve (MV) therapy, and currently there are several devices in different stages of development. The enhanced imaging with 3D transoesophageal echocardiography (TEE), as well as computed tomography (CT) and fusion imaging, has led to better understanding of MV anatomy, which in turn helped promote the development of new devices, as well as being crucial for procedural guidance and effective valve repair or replacement. In addition to the new devices, fusion imaging promises to result in even better outcomes in the future by enhancing device deployment. While initially device development for the MV focused on degenerative mitral regurgitation (MR), more recent studies have demonstrated that reducing the severity of secondary MR with transcatheter techniques may provide symptomatic benefit with regards to cardiac heart failure and improved survival. Percutaneous therapies for the MV, as they are less invasive, have many advantages that may supplant surgical techniques, provided that they reduce morbidity and mortality and have comparable efficacy. In this chapter we review transcatheter MV interventions for mitral stenosis (MS) and MR.
Transcatheter tricuspid valve repair/replacement
Authors: Hahn Rebecca T.
Published: June 2021

Given the high prevalence of significant functional tricuspid regurgitation (TR) in a number of disease states, as well as the impact of TR on mortality, interest has grown in refining the diagnosis and treatment, with hopes of improving outcomes. Surgical intervention has been associated with high mortality and limited improvement in mortality resulting in a need for less invasive alternatives. The current chapter reviews the new percutaneous options for treatment of TR by looking at the pertinent surgical literature, reviewing the relevant anatomic, discussing the strengths and pitfalls of imaging this complex disease process and finally reviewing important device design that may influence device choice.
Nuclear cardiology and detection of coronary artery disease
Authors: Underwood Richard , Stirrup James , Neglia Danilo
Published: June 2021

Experience with radionuclide assessments of myocardial perfusion can be measured over decades. Myocardial perfusion scintigraphy (MPS), performed by either single-photon emission computed tomography (SPECT) or positron emission tomography (PET), has been validated for the diagnosis and prognosis of coronary artery disease (CAD) and is embedded in national and international guidelines. With multiple alternative cardiac imaging modalities available, it is important to understand the principles, indications, and pitfalls of each option. No single technique provides a complete assessment of the heart; many provide complementary rather than equivalent information. In this chapter, the value of cardiac radionuclide imaging in stable CAD and acute coronary syndromes (ACS) is discussed, with a particular emphasis on the role of SPECT MPS, the most commonly used technique in nuclear cardiology.
PET-CT and detection of coronary artery disease
Authors: Di Carli Marcelo F.
Published: June 2021

Myocardial perfusion PET/CT imaging has emerged as a powerful and comprehensive non-invasive approach for the management of patients with suspected or known coronary artery disease (CAD). The multiparametric PET/CT approach provides quantitative information about the extent and severity of focal and diffuse CAD, coronary microvascular dysfunction (CMD), atherosclerotic burden, and left ventricular function. Contemporary evidence demonstrates that this comprehensive approach is one of the most accurate non-invasive tools for diagnosis, risk prediction, and guiding management in patients with CAD. This chapter summarizes the versatility of the integrated PET/CT scan to provide detailed quantitative information tailored to the patient and clinical question. I then review patient-centred clinical applications using case vignettes to illustrate indications of PET/CT and how to present the findings into clinically actionable information for the practising cardiologist. In each case, I review the available data highlighting the diagnostic and prognostic value of the integrated PET/CT protocol.
Non-invasive imaging of the vulnerable atherosclerotic plaque
Authors: Bing Rong , Newby David E. , Narula Jagat , Dweck Marc R.
Published: June 2021

Cardiovascular disease remains the leading cause of death globally despite advances in medical therapy and risk stratification; ischaemic heart disease was responsible for an estimated 9.5 million deaths in 2016. To address this ongoing global burden of morbidity and mortality, there is a need for more sophisticated methods of diagnosis and prognostication, above and beyond clinical risk scores alone. The majority of myocardial infarction occurs due to ruptured atherosclerotic plaque, leading to acute thrombosis and coronary occlusion. For decades, the concept of the vulnerable plaque—plaques prone to rupture or thrombotic complications—has been central to our understanding of the pathophysiology of acute coronary syndromes. More recently, there has been a shift towards identifying the vulnerable patient through assessment of total atherosclerotic disease burden, in recognition of the fact that most plaque rupture events do not lead to clinical events. Moreover, demonstrating a strong causal link between vulnerable plaques and clinical events has previously proven difficult due to limitations in available invasive and non-invasive imaging modalities. However, we now have an array of imaging techniques that hold great potential for the advancement of vulnerable plaque imaging. These modalities are the subject of state-of-the-art clinical research, aiming to develop the role of atherosclerotic plaque imaging in modern clinical practice and ultimately to improve patient outcomes.
Imaging of microvascular disease
Authors: Camici Paolo G. , Rimoldi Ornella
Published: June 2021

Beside obstructive disease of the epicardial coronary arteries dysfunction of the coronary microvasculature has emerged in the past 20 years as an additional mechanism of myocardial ischaemia. The coronary microvasculature cannot be directly visualized in vivo, therefore, both invasive and non-invasive techniques, have been developed to assess parameters that depend directly on coronary microvascular function. Studies at the microcirculatory level entail the use of vasodilators to obtain near-maximal vasodilation. The ratio of the maximal increase of blood flow above its resting value the coronary flow reserve (CFR) allows to gain an insight into the integrated circulatory function. The diagnostic accuracy of imaging techniques can be exploited to detect impairments of myocardial perfusion in asymptomatic subjects with cardiovascular risk factors. The assessment of the coronary microvascular function has provided novel details on the pathophysiological role of coronary microvascular dysfunction in the development of myocardial ischaemia bearing also important prognostic implications.
Evaluation of left ventricular diastolic function
Authors: Popescu Bogdan A. , Beladan Carmen C. , Galderisi Maurizio
Published: June 2021

This chapter looks at how left ventricular diastolic dysfunction (LVDD) is a key player in the pathophysiology of heart failure and it has prognostic implications even in the preclinical stage. Echocardiography is the first-line imaging modality used for the clinical evaluation of left ventricular (LV) diastolic function. A large number of echocardiographic parameters have been tested and validated against invasive measurements of diastolic function, each of them having potential limitations. The updated 2016 American Society of Echocardiography (ASE)/European Association of Cardiovascular Imaging (EACVI) recommendations proposed a comprehensive integrated approach aiming to make the assessment of LV diastolic function easier and accurate for daily clinical practice.
Imaging cardiac innervation
Authors: Flotats Albert , Carrió Ignasi
Published: June 2021

Cardiac autonomic nervous system contributes to maintain haemodynamic and electrophysiological stability to changing demands. Cardiac innervation imaging can be performed by means of planar scintigraphy/SPECT or PET using different radiotracers developed for the assessment of pre- and postsynaptic receptors of the cardiac autonomic nervous system, with sufficient sensitivity to assess a process that takes place at picomolar concentrations. Clinically, cardiac innervation imaging is mainly performed targeting postganglionic presynaptic sympathetic neurons by means of myocardial 123I-metaiodobenzylguanidine (123I-mIBG) planar scintigraphy and SPECT, which has shown to be of value in the assessment of patients with different cardiac disorders, especially in those with heart failure (HF), having an independent prognostic value. This clinically oriented chapter updates the subject with inclusion of new data reinforcing the use of sympathetic cardiac innervation imaging for improving patient management.
Cardiac resynchronization therapy: Optimization and follow-up
Authors: Sitges Marta , Donal Erwan
Published: June 2021

Cardiac imaging techniques have an important role in the follow-up of patients undergoing cardiac resynchronization therapy (CRT) as they provide objective evidence of changes in cardiac dimensions and function. The role of echocardiography is well established in the assessment of left ventricular reverse remodelling and the evaluation of secondary (functional) mitral regurgitation. Additionally, echocardiography might be used for optimizing the programming of atrioventricular (AV) and interventricular (VV) delays of current CRT devices. Acute benefit from this optimization has been demonstrated, but longer follow-up studies have failed to show a clear benefit of optimized CRT on top of simultaneous biventricular pacing on the outcome of patients with CRT. This chapter reviews the role of imaging in assessing follow-up and outcome of patients undergoing CRT as well as the rationale, the methods used, and the clinical impact of optimization of the programming of CRT devices.
Other genetic and acquired cardiomyopathies
Authors: Haugaa Kristina , Elliott Perry
Published: June 2021

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is an inherited, progressive cardiomyopathy associated with high risk of ventricular tachycardia associated with right-sided structural disorders. More recent reports have shown that although the right ventricle (RV) is most often affected, the left ventricle (LV) is also commonly involved. This has led to the more recent term arrhythmogenic cardiomyopathy (AC). Men are more frequently affected than women and it is usually diagnosed between the second and fourth decade of life. The most common presentation is ventricular arrhythmia, specifically ventricular tachycardia originating from the RV with a characteristic left bundle-branch block (LBBB) morphology. ARVC is also an important cause of sudden death in individuals <30 years of age and has been found in up to 20% of sudden deaths in young individuals. Furthermore, ARVC is more common in athletes and disease expression is associated with high intensity exercise.
Myocarditis
Authors: Yilmaz Ali , Mahrholdt Heiko , Sechtem Udo
Published: June 2021

The symptoms and signs of myocarditis are non-specific. Thus, myocarditis is a differential diagnosis in many patients with heart complaints. As myocarditis may accompany common viral infections of the upper respiratory and gastrointestinal tracts, and mild ECG changes are not uncommon in such patients, the diagnosis needs to be considered in large patient cohorts. Establishing the correct diagnosis is of importance as the disease may lead to sudden cardiac death or dilated cardiomyopathy. As clinical tools such as history taking, physical examination, blood tests, the ECG, and the chest X-ray are not sufficient to ascertain the diagnosis of myocarditis, additional information from cardiac imaging techniques, or endomyocardial biopsy are necessary to confirm or exclude the disease. In daily clinical routine, however, the use of biopsy is limited to severely ill patients with reduced left ventricular function due to its invasiveness and potential complications. Thus, this chapter reviews how non-invasive cardiac imaging techniques can be used in clinical practice to diagnose myocarditis.
Aortic disease: Aneurysm and dissection—role of MSCT
Authors: Hinojar Rocío , Erbel Raimund
Published: June 2021

Multislice computed tomography (MSCT) is currently the preferred modality for diagnosis and complete characterization of aortic pathology because of its widespread availability, rapidity, excellent spatial resolution, and excellent accuracy for all aortic segments and different aortic diseases. Aortic disease often remains undiagnosed until a life-threatening complication occurs or the disease is an unexpected finding on imaging studies performed for other purposes. MSCT allows the measurement of the aortic wall and dimension and the evaluation of morphologic features and surrounding structures, even in very sick or unstable patients. It provides not only accurate and highly reproducible aortic measurements but also the evaluation of the wall and contents of an aneurysm, including thrombus, and surrounding structures.
The role of CMR and MSCT
Authors: Di Salvo Giovanni , Pluchinotta Francesca R.
Published: June 2021

Congenital heart disease (CHD) affects 6–8 per 1,000 of newborn infants. As a result of advances in cardiac surgery and clinical management, survival of patients with CHD has significantly improved over the last decades. Nowadays, it is estimated that 85% of children will survive to adulthood. Imaging is a crucial component to the multidisciplinary management of these patients. Techniques are required both to characterize anatomical structures and their functional status in order to improve management, evaluate the consequences of interventions, and help guide prognosis. Therefore, assessment for CHD requires a multimodality approach where a variety of imaging techniques should be used in a complementary fashion looking for sensitivity, accuracy, reproducibility, and cost-effectiveness, while minimizing harm to the patients.
Fast magnetoacoustic wave trains: from tadpoles to boomerangs
Authors: Kolotkov Dmitrii Y , Nakariakov Valery M , Moss Guy , Shellard Paul
Published: June 2021

Rapidly propagating fast magnetoacoustic wave trains guided by field-aligned plasma non-uniformities are confidently observed in the Sun’s corona. Observations at large heights suggest that fast wave trains can travel long distances from the excitation locations. We study characteristic time signatures of fully developed, dispersive fast magnetoacoustic wave trains in field-aligned zero-β plasma slabs in the linear regime. Fast wave trains are excited by a spatially localized impulsive driver and propagate along the waveguide as prescribed by the waveguide-caused dispersion. In slabs with steeper transverse density profiles, developed wave trains are shown to consist of three distinct phases: a long-period quasi-periodic phase with the oscillation period shortening with time, a multiperiodic (peloton) phase in which distinctly different periods co-exist, and a short-lived periodic Airy phase. The appearance of these phases is attributed to a non-monotonic dependence of the fast wave group speed on the parallel wavenumber due to the waveguide dispersion, and is shown to be different for axisymmetric (sausage) and non-axisymmetric (kink) modes. In wavelet analysis, this corresponds to the transition from the previously known tadpole shape to a new boomerang shape of the wave train spectrum, with two well-pronounced arms at shorter and longer periods. We describe a specific previously published radio observation of a coronal fast wave train, highly suggestive of a change of the wavelet spectrum from a tadpole to a boomerang, broadly consistent with our modelling. The applicability of these boomerang-shaped fast wave trains for probing the transverse structuring of the waveguiding coronal plasma is discussed.
Formation and fate of the born-again planetary nebula HuBi 1
Authors: Toalá J A , Lora V , Montoro-Molina B , Guerrero M A , Esquivel A
Published: June 2021

We present the first 3D radiation-hydrodynamic simulations on the formation and evolution of born-again planetary nebulae (PNe), with particular emphasis to the case of HuBi 1, the inside-out PN. We use the extensively tested guacho code to simulate the formation of HuBi 1 adopting mass-loss and stellar wind terminal velocity estimates obtained from observations presented by our group. We found that, if the inner shell of HuBi 1 was formed by an explosive very late thermal pulse (VLTP) ejecting material with velocities of ∼300 km s−1, the age of this structure is consistent with that of ≃200 yr derived from multi-epoch narrow-band imaging. Our simulations predict that, as a consequence of the dramatic reduction of the stellar wind velocity and photon ionizing flux during the VLTP, the velocity and pressure structure of the outer H-rich nebula are affected creating turbulent ionized structures surrounding the inner shell. These are indeed detected in Gran Telescopio Canarias MEGARA optical observations. Furthermore, we demonstrate that the current relatively low ionizing photon flux from the central star of HuBi 1 is not able to completely ionize the inner shell, which favours previous suggestions that its excitation is dominated by shocks. Our simulations suggest that the kinetic energy of the H-poor ejecta of HuBi 1 is at least 30 times that of the clumps and filaments in the evolved born-again PNe A 30 and A 78, making it a truly unique VLTP event.
The DEAD-box RNA helicase RhlE2 is a global regulator ofPseudomonas aeruginosalifestyle and pathogenesis
Authors: Hausmann Stéphane , Gonzalez Diego , Geiser Johan , Valentini Martina
Published: June 2021

RNA helicases perform essential housekeeping and regulatory functions in all domains of life by binding and unwinding RNA molecules. The bacterial RhlE-like DEAD-box RNA helicases are among the least well studied of these enzymes. They are widespread especially among Proteobacteria, whose genomes often encode multiple homologs. The significance of the expansion and diversification of RhlE-like proteins for bacterial fitness has not yet been established. Here, we study the two RhlE homologs present in the opportunistic pathogen Pseudomonas aeruginosa. We show that, in the course of evolution, RhlE1 and RhlE2 have diverged in their biological functions, molecular partners and RNA-dependent enzymatic activities. Whereas RhlE1 is mainly needed for growth in the cold, RhlE2 also acts as global post-transcriptional regulator, affecting the level of hundreds of cellular transcripts indispensable for both environmental adaptation and virulence. The global impact of RhlE2 is mediated by its unique C-terminal extension, which supports the RNA unwinding activity of the N-terminal domain as well as an RNA-dependent interaction with the RNase E endonuclease and the cellular RNA degradation machinery. Overall, our work reveals how the functional and molecular divergence between two homologous RNA helicases can contribute to bacterial fitness and pathogenesis.
ATRT-01. IDENTIFICATION OF MICRORNA-BASED PROGNOSTIC BIOMARKERS AND CANDIDATE THERAPEUTIC AGENTS FOR ATYPICAL TERATOID/RHABDOID TUMOR
Authors: Zhang Yang
Published: June 2021

Background

MicroRNA (miRNA) has been found to be involved in development of many malignant pediatric brain tumors, including atypical teratoid/rhabdoid tumor (AT/RT) that is highly aggressive and carries a dismal prognosis. The current study investigated the potential value of miRNAs and pivotal genes associated with AT/RT using bioinformatics analysis, aiming to identify new prognostic biomarkers and candidate drugs for AT/RT patients.

Methods

Differentially expressed miRNAs (DEMs) and genes (DEGs) between AT/RT and normal control samples were obtained from GEO database. The target genes of DEMs were predicted via TargetScanHuman7.2 and miRDB, and then intersected with DEGs. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses of overlapping genes were conducted, followed by construction of protein-protein interaction network. Hub genes were determined by Cytoscape software, and their prognostic values were evaluated using Kaplan-Meier analysis. Connectivity Map database was used to identify latent therapeutic agents.

Results

A total of 11 DEMs (hsa-miR-1224-5p, hsa-miR-128-3p, hsa-miR-17-5p, hsa-miR-18b-5p, hsa-miR-29c-5p, hsa-miR-329-3p, hsa-miR-379-5p, hsa-miR-433-3p, hsa-miR-488-5p, hsa-miR-656-3p and hsa-miR-885-5p) were screened. By intersecting 3275 predicted target genes and 925 DEGs, we finally identified 226 overlapping genes that were enriched in pathways in cancer and MAPK signaling pathway. Four hub genes (GRIA2, NRXN1, SLC6A1 and SYT1) were significantly associated with the overall survival of AT/RT patients. Candidate drugs included histone deacetylase inhibitor (givinostat), DNA synthesis inhibitor (floxuridine), cyclin-dependent kinase inhibitor (purvalanol) and janus kinase inhibitor (lestaurtinib).

Conclusion

In summary, this study systematically analyzed AT/RT-related miRNAs and pivotal genes to provide novel prognostic biomarkers and potential therapeutic agents.
ATRT-02. THE DUAL MTORC1/2 INHIBITOR, TAK-228 COMBINES SYNERGISTICALLY WITH THE BH3 MIMETIC, OBATOCLAX TO IMPROVE SURVIVAL IN MICE BEARING ORTHOTOPIC XENOGRAFTS OF AT/RT
Authors: Findlay Tyler , Parkhurst Ashlyn , Wang Sabrina , Eberhart Charles , Raabe Eric , Rubens Jeffrey
Published: June 2021

mTOR activation drives tumorigenicity by regulating transcription factor expression and downstream growth and survival pathways. We have previously shown that mTORC1 and mTORC2 are highly activated in AT/RT and the dual mTORC1/2 inhibitor, TAK-228 (Sapanisertib) improves survival in mice bearing orthotopic xenografts of AT/RT. To design a rational combination therapy that enhances TAK-228’s efficacy and durability, we performed RNASeq 4 hours after TAK-228 treatment of AT/RT cell models. Pathway analysis revealed disruption of the NRF2-mediated stress response. NRF2 is a cap’n’collar leucine zipper transcription factor that regulates expression of genes involved in redox homeostasis, energy metabolism, cell proliferation, and survival. Analysis of publicly available RNASeq data on 32 human tumors identified elevated expression of NRF2 in AT/RT (median expression 40.78, normal brain 18.81). Short-hairpin knockdown of NRF2 decreased the expression of NRF2 as well as the anti-apoptotic proteins MCL-1, BCL-xL, and BCL-2 (western blot), and intracellular concentrations of reduced glutathione (p<0.005, t-test). TAK-228 similarly decreased expression of NRF2, MCL-1, and glutathione (p<0.005, t-test) demonstrating that TAK-228 compromises AT/RT defenses against oxidative stress and cell death. The brain-penetrant BH3 mimetic, Obatoclax increases oxidative stress and induces apoptosis in AT/RT (MUSE oxidative stress, cPARP western blot, t-test p<0.05). These complementary mechanisms of action synergize to slow AT/RT cell growth (MUSE Cell viability assay, ANOVA p<0.05) and induce high rates of cell death (MUSE ANNEXIN V assay, ANOVA p<0.05, Western blot for cPARP, Compusyn Synergy analysis CI<1.0). Once-weekly treatments of TAK-228 combined with Obatoclax in orthotopic mouse models of AT/RT is well tolerated, slows tumor growth (bioluminescence imaging, ANOVA p<0.05) and significantly extends median survival from 35 to 55 days (Log-rank p<0.05). These findings support a new clinical trial aimed at improving AT/RT survival.
BIOL-05. MAPK PATHWAY INHIBITION SENSITIZES TO IMMUNOTHERAPY IN BRAF-MUTANT GLIOMAS
Authors: Park Jong-Whi , Barrette Anne-Marie , Wang Wei , Grossauer Stefan , Grant Gerald , Lau Ken , Pitteri Sharon , Monje Michelle , Petritsch Claudia
Published: June 2021

Background

BRAF alterations frequently occur in pediatric low-grade gliomas. Previously, we showed that dabrafenib and trametinib (D+T) that target MAPK pathway can mediate the antitumor effect in a preclinical model of BRAF-mutant glioma (PMC5342782). Here, we further investigate the effect of MAPK pathway inhibitors on cancer cells and tumor-infiltrating immune cells to maximize the therapeutic efficacy in malignant gliomas.

Methods

Drug concentrations in tumor, brain and plasma were assessed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). RNA sequencing and Gene Set Enrichment Analysis were performed using patient-derived BRAF-mutant glioma lines upon D+T treatment. Molecular profiles of drug-resistant clones were assessed for understanding of glioma heterogeneity and exploring new therapeutic targets. Results. BRAF-mutant stem-like glioma cells were particularly resistant to BRAF or MAPK inhibitor, along with aggressive phenotype in mice. LC-MS/MS showed effective D+T drug delivery in tumor regions. The transcriptome analysis demonstrated that D+T upregulate HLA molecules and downregulate immunosuppressive factors in patient-derived BRAF-mutant glioma lines. Consistent with these molecular changes, D+T led to changes in the proportions of tumor-infiltrating immune cells, including CD8+ cytotoxic T lymphocytes and FOXP3+ regulatory T cells. Furthermore, the therapeutic effect of D+T was further enhanced in combination with immune checkpoint inhibition.

Conclusions

The present study highlights the immunomodulatory activity of MAPK pathway inhibitors in BRAF-mutant gliomas.
EMBR-06. EFFECTIVE INHIBITION OF MYC-AMPLIFIFIED GROUP 3 MEDULLOBLASTOMA BY FACT-TARGETED CURAXIN DRUG CBL0137
Authors: Wang Jiajia , Ma Jie
Published: June 2021

Medulloblastoma (MB) is the most common malignant pediatric brain tumor that can be categorized into four major molecular subgroups. Group 3 MB with MYC amplifification (MYCamp-G3-MB) has been shown to be highly aggressive and exhibited worst prognosis, indicating the need for novel effective therapy most urgently. A few epigenetic targeted therapeutic strategies have recently been proven to effectively treat preclinical models of MYCamp-G3-MB, including BET inhibition, HDAC inhibition and SETD8 inhibition, unveiling a promising direction for further investigation. In this study, we carried out systemic bioinformatic analyses of public-available MB datasets as well as functional genomic screening datasets of primary MYCamp-G3-MB lines to search for other potential therapeutic targets within epigenetic modulators. We identifified SSRP1, a subunit of histone-chaperone FACT complex, to be the top drug target candidate as it is highly cancer-dependent in whole-genome CRISPR-Cas9 screening across multiple MYCamp-G3-MB lines; signifificantly upregulated in MYCamp-G3-MB compared to normal cerebellum and most of the rest MB subtypes; its higher expression is correlated with worse prognosis; and it has a blood-brain-barrier penetrable targeted drug that has entered early phase human clinical trials already. Then we utilized RNA-interference approach to verify the cancer-dependency of SSRP1 in multiple MYCamp-G3-MB lines and further confifirmed the therapeutic effificacy of FACT-targeted curaxin drug CBL0137 on treating preclinical models of MYCamp-G3-MB in vitro and in vivo, including an orthotopic intracranial xenograft model. Mechanistically, transcriptome analyses showed CBL0137 preferentially suppressed cell-cycle and DNA-repair related biological processes. Moreover, it selectively disrupted transcription of MYC and NEUROD1, two critical oncogenic transcription factors of MYCamp-G3-MB, via depleting FACT complex from their promoter regions. In summary, our study demonstrates FACT-targeted CBL0137 works effectively on treating MYCamp-G3-MB, presenting another promising epigenetic-targeted therapeutic strategy against the most devastating form of MB.
EMBR-15. PRC2 COMPLEX ENFORCES NEURONAL LINEAGE AND SUPPRESSES TUMOR GROWTH IN SHH MEDULLOBLASTOMA
Authors: Cleveland Abigail , Malawsky Daniel , Churiwal Mehal , Gershon Timothy
Published: June 2021

Hyperactivation of Sonic Hedgehog (SHH) signaling pathway drives tumor progression in the largest medulloblastoma subgroup. During cerebellar development, promoters of SHH target genes show inhibitory trimethylation of histone H3 at lysine 27 (H3K27me3), mediated by the Polycomb Repressive Complex 2 (PRC2). Here, we explored the regulation of cerebellar growth and medulloblastoma tumorigenesis by PRC2 complex components EED and EZH2. For developmental studies, we conditionally deleted Eed or Ezh2 in the Atoh1 lineage that gives rise to the cerebellar granule neuron progenitors (CGNP) that are cells of origin for SHH medulloblastomas. For tumor studies, we bred the conditional Eed- or Ezh2-deleted mouse lines with mice genetically engineered to develop SHH medulloblastoma. Our developmental studies showed that Eed was absolutely required for cerebellar growth. Eed-deleted CGNPs underwent aberrant, myocyte-like differentiation and spontaneous apoptosis, resulting in cerebellar hypoplasia. In contrast, Ezh2 deletion produced no developmental phenotype, despite blocking all H3K27me3 in CGNPs. Our tumor studies showed that Eed-deleted medulloblastomas similarly showed aberrant, myocyte differentiation, but unlike CGNPs, did not undergo widespread apoptosis. Eed-deleted medulloblastomas progressed more rapidly than control tumors, indicating that the inappropriate, muscle-like differentiation did not slow tumor growth. Ezh2-deleted medulloblastomas similarly progressed more rapidly than controls. Our data show that the PRC2 complex acts to enforce neuronal lineage commitment in both development and tumorigenesis and to restrain tumor growth in SHH medulloblastoma. Myocyte differentiation in Eed-deleted tumors suggests that PRC2 loss of function may contribute to the medullomyoblastomas that have been observed in patients. The differences in developmental phenotype show that EZH2 and EED functions are non-identical and can be dissociated, while similar increase in tumor progression show tumor suppressive functions for both EED and EZH2.
EMBR-16. SMOOTHENED-ACTIVATING LIPIDS DRIVE RESISTANCE TO CDK4/6 INHIBITION IN HEDGEHOG-ASSOCIATED MEDULLOBLASTOMA
Authors: Daggubati Vikas , Hochstelter Jordan , Bommireddy Anirudh , Choudhury Abrar , Krup Alexis Leigh , Choski Pervinder , Tong Pakteema , Li Amy , Xu Libin , Reiter Jeremy , Raleigh David
Published: June 2021

Background

Medulloblastoma is an aggressive pediatric brain tumor that is associated with misactivation of the Hedgehog (HH) pathway. Our lab has shown that CDK6, a critical activator of the cell cycle, is a direct transcriptional target of oncogenic HH signaling, and that inhibiting CDK6 blocks the growth of HH-associated medulloblastoma in mice. A clinical trial exploring the efficacy of CDK6 inhibition in medulloblastoma patients is underway, but prior attempts to target the HH pathway in medulloblastoma have been encumbered by resistance to molecular monotherapy. Thus, we sought to identify mechanisms of resistance to CDK6 inhibition in HH-associated medulloblastoma.

Methods

We performed orthogonal CRISPR and CRISPR interference screens in HH-associated medulloblastoma cells treated with pharmacologic inhibitors of CDK6 in vitro, and RNA-sequencing of HH-associated medulloblastomas with genetic deletion of CDK6 in vivo. Mechanistic and functional validation of resistance pathways was performed using CRISPR interference, immunoblotting, immunofluorescence, genetics, and pharmacology. Lipid quantification was carried out by ultra-high performance liquid chromatography-tandem mass spectrometry.

Results

Our results reveal that decreased ribosomal protein expression underlies resistance to CDK6 inhibition in HH-associated medulloblastoma, leading to endoplasmic reticular (ER) stress and activation of the unfolded protein response (UPR). We show that ER stress and the UPR increase the activity of enzymes producing Smoothened-activating sterol lipids that sustain oncogenic HH signaling in medulloblastoma despite CDK6 inhibition. These discoveries suggest that combination molecular therapy against CDK6 and HSD11ß2, an enzyme producing Smoothened-activating lipids, may be an effective treatment for HH-associated medulloblastoma. In support of this hypothesis, we demonstrate that concurrent genetic deletion or pharmacological inhibition of CDK6 and HSD11ß2 additively blocks the growth of multiple models of HH-associated medulloblastoma in mice.

Conclusions

Smoothened-activating lipid biosynthesis underlies resistance to CDK6 inhibition in HH-associated medulloblastoma, revealing a novel combination therapy to treat the most common malignant brain tumor in children.
EMBR-20. ELONGATION CONTROL OF MRNA TRANSLATION DRIVES GROUP 3 MEDULLOBLASTOMA
Authors: Delaidelli Alberto , Negri Gian Luca , Wang Que Xi , Huang Albert , Sidhu Simran , Zhang Joyce , Huang Yue Zhou , Yao Betty , Langman Sofya , Vislovukh Andrii , Hovestadt Volker , Taylor Michael , Leprivier Gabriel , Sorensen Poul
Published: June 2021

Medulloblastoma (MB) is the most common pediatric intracranial tumor and leading cause of childhood related cancer deaths. Group 3 affiliation and genetic amplifications of the MYC oncogene are predictors of adverse outcome in MB, underscoring a dire need for novel and more effective therapeutic approaches. The let-7 family of small non-coding RNAs (miRNAs) is known to inhibit tumor progression and regulate metabolism by targeting and degrading several cellular mRNAs, including MYC. Indeed, let-7 miRNAs are frequently repressed in several cancer types, including in MYC-driven MB. We previously reported that the mRNA translation elongation regulator eukaryotic Elongation Factor-2 Kinase (eEF2K) is a pivotal mediator of cancer cell adaptation to nutrient deprivation. In the current work, we identified a potential binding site for let-7 miRNAs on the eEF2K 3’ untranslated region (UTR). In addition, eEF2K mRNA and let-7 miRNA expressions negatively correlate in MB, suggesting a potential regulation of the former by the latter. Let-7 miRNAs transfection decreases eEF2K mRNA and protein levels (by ~40–50%). Down-regulation of luciferase activity by let-7 miRNAs is impaired upon mutation of the let-7 binding site on the eEF2K 3’UTR. Inhibition of eEF2K significantly reduces survival of MYC-amplified MB cell lines under nutrient deprivation, altering their mRNA translation rates. Knockout of eEF2K increases survival of MYC-amplified MB xenografts when mice are kept under calorie restricted diets. We conclude that let-7 miRNAs degrade the eEF2K mRNA by binding to its 3’UTR, indicating that let-7 repression in MYC-driven MB is partially responsible for increased eEF2K levels. Moreover, the let-7-eEF2K axis constitutes a critical mechanism for MYC-driven MB adaptation to acute metabolic stress, representing a promising therapeutic target. Future therapeutic studies will aim to combine eEF2K inhibition with caloric restriction mimetic drugs, as eEF2K activity appears critical under metabolic stress conditions.
HGG-13. BRAIN DISTRIBUTION AND CLEARANCE OF ALISERTIB IS LIMITED BY PGP AND BCRP EFFLUX PUMPS AND DEPENDENT UPON DELIVERY METHOD
Authors: Power Erica , Oh Juhee , Zhang Liang , Elmquist William , Daniels David
Published: June 2021

Diffuse midline gliomas (DMGs) harboring the H3K27M mutation are highly aggressive, uniformly fatal brain tumors that primarily occur in children. The blood-brain barrier (BBB), including drug efflux pumps, prevent numerous drugs from reaching CNS tumors at cytotoxic concentrations. Alisertib is an aurora kinase inhibitor that was previously identified in a drug screen as a compound of interest. However, its ability to penetrate the BBB is not well established. The goals of this study were two-fold: 1) determine the CNS distribution and clearance rates of alisertib following systemic delivery and if the BBB efflux pumps, Pgp and BCRP, alter distribution and clearance. 2) Compare alisertib distribution and clearance following convection-enhanced delivery to systemic results. WT and Pgp/BCRP knockout mice and Sprague-dawley rats underwent tail vein injection (mice and rats) or convection-enhanced delivery to the brainstem (rats only) of alisertib and sacrificed at 0, 2, 4, 8, 12, 16 and 24hours. The plasma and brain were collected and analyzed for alisertib concentration by HPLC-MS/MS. We found that in both mice and rats, alisertib concentration in the plasma and brain decreased biexponentially. Overall, Alisertib was found to be 3.14% brain penetrant. In Pgp/BCRP knockout mice, alisertib concentration in the plasma and brain decreased biexponentially, but was detected at higher concentration at all time points in the brain compared to WT mice. This resulted in a higher brain penetrance (17.26%). Differences based on anatomical brain region were significant in those rats which received convection-enhanced delivery. Alisertib was found in higher concentration in the pons and cerebellum compared to systemic delivery, but lower concentrations in the cortex and plasma. These results suggest that drug clearance may be a general mechanism limiting efficacy of drugs of interest and should be carefully considered during preclinical evaluation.
HGG-26. SINGLE-CELL RNA-SEQ OF PEDIATRIC HIGH-GRADE GLIOMAS IDENTIFIES COMMON ONCOGENIC PROCESSES AMONG DISTINCT TUMOR HISTOLOGIES
Authors: DeSisto John , Donson Andrew , Fu Rui , Sanford Bridget , Riemondy Kent , Green Adam
Published: June 2021

Background

Pediatric high-grade glioma (PHGG) is a deadly childhood brain tumor that responds poorly to treatment. PHGG comprises two major subtypes: cortical tumors with wild-type H3K27 and diffuse midline gliomas (DMG) that occur in the midline and have characteristic H3K27M mutations. Cortical PHGG is heterogeneous with multiple molecular subtypes. In order to identify underlying commonalities in cortical PHGG that might lead to better treatment modalities, we performed molecular profiling, including single-cell RNA-Seq (scRNA-Seq), on PHGG samples from Children’s Hospital Colorado.

Methods

Nineteen cortical PHGG tumor samples, one DMG and one normal margin sample obtained at biopsy were disaggregated to isolate viable cells. Fifteen were glioblastomas (GBM), including five with epithelioid and/or giant cell features and five radiation-induced glioblastomas (RIG). There were also four non-GBM PHGG. We performed scRNA-Seq using 10X Genomics v.3 library preparation to enable capture of infiltrating immune cells. We also performed bulk RNA-Seq and DNA methylation profiling.

Results

After eliminating patient-specific and cell-cycle effects, RIG, epithelioid GBM, and other GBM each formed identifiable subgroups in bulk RNA-Seq and scRNA-Seq datasets. In the scRNA-Seq data, clusters with cells from multiple tumor samples included a PDGFRA-positive population expressing oligodendrocyte progenitor markers, astrocytic, mesenchymal and stemlike populations, macrophage/monocyte immune cells, and a smaller T-cell population. Analyses of DNA methylation data showed PDGFRA and CDK4 amplification and CDKN2A deletion are common alterations among PHGG. Inferred copy number variation analysis of the single-cell data confirmed that individual tumors include populations that both include and lack the molecular alterations identified in the methylation data. RNA velocity studies to define tumor cells of origin and further analyses of the immune cell populations are underway.

Conclusions

Single-cell analysis of PHGG confirms a large degree of tumor heterogeneity but also shows that PHGG have stemlike, mesenchymal and immune cell populations with common characteristics.