ATR-mediated phosphorylation of FANCI regulates dormant origin firing in response to replication stress.

Excess dormant origins bound by the minichromosome maintenance (MCM) replicative helicase complex play a critical role in preventing replication stress, chromosome instability, and tumorigenesis. In response to DNA damage, replicating cells must coordinate DNA repair and dormant origin firing to ensure complete and timely replication of the genome; how cells regulate this process remains elusive. Herein, we identify a member of the Fanconi anemia (FA) DNA repair pathway, FANCI, as a key effector of dormant origin firing in response to replication stress. Cells lacking FANCI have reduced number of origins, increased inter-origin distances, and slowed proliferation rates. Intriguingly, ATR-mediated FANCI phosphorylation inhibits dormant origin firing while promoting replication fork restart/DNA repair. Using super-resolution microscopy, we show that FANCI co-localizes with MCM-bound chromatin in response to replication stress. These data reveal a unique role for FANCI as a modulator of dormant origin firing and link timely genome replication to DNA repair.

Identification and characterization of second-generation EZH2 inhibitors with extended residence times and improved biological activity.

The histone methyltransferase EZH2 has been the target of numerous small-molecule inhibitor discovery efforts over the last 10+ years. Emerging clinical data have provided early evidence for single agent activity with acceptable safety profiles for first-generation inhibitors. We have developed kinetic methodologies for studying EZH2-inhibitor-binding kinetics that have allowed us to identify a unique structural modification that results in significant increases in the drug-target residence times of all EZH2 inhibitor scaffolds we have studied. The unexpected residence time enhancement bestowed by this modification has enabled us to create a series of second-generation EZH2 inhibitors with sub-pM binding affinities. We provide both biophysical evidence validating this sub-pM potency and biological evidence demonstrating the utility and relevance of such high-affinity interactions with EZH2.

Is there a code embedded in proteins that is based on post-translational modifications?

Covalent post-translational modifications (PTMs) provide vast indexing potential and expanded protein use. The 'histone code' hypothesis has inspired rapid advances throughout chromatin biology, and has recently been tapped for its relevance to non-histone proteins. Comprehensive analyses suggest that rather than constituting a general code, the covalent modifications of proteins (including histones) provide surfaces that are recognized by effectors that can give rise to intricate interactions and downstream events. These are reminiscent of other regulatory cascades in transcription and cell signalling.

Astrocyte-Mediated Neuronal Synchronization Properties Revealed by False Gliotransmitter Release.

Astrocytes spontaneously release glutamate (Glut) as a gliotransmitter (GT), resulting in the generation of extrasynaptic NMDAR-mediated slow inward currents (SICs) in neighboring neurons, which can increase local neuronal excitability. However, there is a deficit in our knowledge of the factors that control spontaneous astrocyte GT release and the extent of its influence. We found that, in rat brain slices, increasing the supply of the physiological transmitter Glut increased the frequency and signaling charge of SICs over an extended period. This phenomenon was replicated by exogenous preexposure to the amino acid D-aspartate (D-Asp). Using D-Asp as a "false" GT, we determined the extent of local neuron excitation by GT release in ventrobasal thalamus, CA1 hippocampus, and somatosensory cortex. By analyzing synchronized neuronal NMDAR-mediated excitation, we found that the properties of the excitation were conserved in different brain areas. In the three areas, astrocyte-derived GT release synchronized groups of neurons at distances of >;200 µm. Individual neurons participated in more than one synchronized population, indicating that individual neurons can be excited by more than one astrocyte and that individual astrocytes may determine a neuron's synchronized network. The results confirm that astrocytes can act as excitatory nodes that can influence neurons over a significant range in a number of brain regions. Our findings further suggest that chronic elevation of ambient Glut levels can lead to increased GT Glut release, which may be relevant in some pathological states.SIGNIFICANCE STATEMENT Astrocytes spontaneously release glutamate (Glut) and other gliotransmitters (GTs) that can modify neuronal activity. Exposing brain slices to Glut and D-aspartate (D-Asp) before recording resulted in an increase in frequency of GT-mediated astrocyte-neuron signaling. Using D-Asp, it was possible to investigate the effects of specific GT release at neuronal NMDARs. Calcium imaging showed synchronized activity in groups of neurons in cortex, hippocampus, and thalamus. The size of these populations was similar in all areas and some neurons were involved in more than one synchronous group. The findings show that GT release is supply dependent and that the properties of the signaling and activated networks are largely conserved between different brain areas.

Regulatory T Cell Modulation by CBP/EP300 Bromodomain Inhibition.

Covalent modification of histones is a fundamental mechanism of regulated gene expression in eukaryotes, and interpretation of histone modifications is an essential feature of epigenetic control. Bromodomains are specialized binding modules that interact with acetylated histones, linking chromatin recognition to gene transcription. Because of their ability to function in a domain-specific fashion, selective disruption of bromodomain:acetylated histone interactions with chemical probes serves as a powerful means for understanding biological processes regulated by these chromatin adaptors. Here we describe the discovery and characterization of potent and selective small molecule inhibitors for the bromodomains of CREBBP/EP300 that engage their target in cellular assays. We use these tools to demonstrate a critical role for CREBBP/EP300 bromodomains in regulatory T cell biology. Because regulatory T cell recruitment to tumors is a major mechanism of immune evasion by cancer cells, our data highlight the importance of CREBBP/EP300 bromodomain inhibition as a novel, small molecule-based approach for cancer immunotherapy.

Development of methyl isoxazoleazepines as inhibitors of BET.

In this report we detail the evolution of our previously reported thiophene isoxazole BET inhibitor chemotype exemplified by CPI-3 to a novel bromodomain selective chemotype (the methyl isoxazoleazepine chemotype) exemplified by carboxamide 23. The methyl isoxazoleazepine chemotype provides potent inhibition of the bromodomains of the BET family, excellent in vivo PK across species, low unbound clearance, and target engagement in a MYC PK-PD model.

BRD4 is an atypical kinase that phosphorylates serine2 of the RNA polymerase II carboxy-terminal domain.

The bromodomain protein, BRD4, has been identified recently as a therapeutic target in acute myeloid leukemia, multiple myeloma, Burkitt's lymphoma, NUT midline carcinoma, colon cancer, and inflammatory disease; its loss is a prognostic signature for metastatic breast cancer. BRD4 also contributes to regulation of both cell cycle and transcription of oncogenes, HIV, and human papilloma virus (HPV). Despite its role in a broad range of biological processes, the precise molecular mechanism of BRD4 function remains unknown. We report that BRD4 is an atypical kinase that binds to the carboxyl-terminal domain (CTD) of RNA polymerase II and directly phosphorylates its serine 2 (Ser2) sites both in vitro and in vivo under conditions where other CTD kinases are inactive. Phosphorylation of the CTD Ser2 is inhibited in vivo by a BRD4 inhibitor that blocks its binding to chromatin. Our finding that BRD4 is an RNA polymerase II CTD Ser2 kinase implicates it as a regulator of eukaryotic transcription.

Astrocyte and Neuronal Plasticity in the Somatosensory System.

Changing the whisker complement on a rodent's snout can lead to two forms of experience-dependent plasticity (EDP) in the neurons of the barrel cortex, where whiskers are somatotopically represented. One form, termed coding plasticity, concerns changes in synaptic transmission and connectivity between neurons. This is thought to underlie learning and memory processes and so adaptation to a changing environment. The second, called homeostatic plasticity, serves to maintain a restricted dynamic range of neuronal activity thus preventing its saturation or total downregulation. Current explanatory models of cortical EDP are almost exclusively neurocentric. However, in recent years, increasing evidence has emerged on the role of astrocytes in brain function, including plasticity. Indeed, astrocytes appear as necessary partners of neurons at the core of the mechanisms of coding and homeostatic plasticity recorded in neurons. In addition to neuronal plasticity, several different forms of astrocytic plasticity have recently been discovered. They extend from changes in receptor expression and dynamic changes in morphology to alteration in gliotransmitter release. It is however unclear how astrocytic plasticity contributes to the neuronal EDP. Here, we review the known and possible roles for astrocytes in the barrel cortex, including its plasticity.

Added value of diffusion-weighted acquisitions in MRI of the abdomen and pelvis.

OBJECTIVE: The purpose of this article is to review abdominopelvic applications of diffusion-weighted imaging (DWI), discuss advantages and limitations of DWI, and illustrate these with examples. CONCLUSION: High-quality abdominopelvic DWI can be performed routinely on current MRI systems and may offer added value in image interpretation. Particularly in unenhanced MRI examinations, DWI may provide an alternative source of image contrast and improved conspicuity to identify and potentially characterize pathology. DWI is a powerful technique that warrants implementation in routine abdominal and pelvic imaging protocols.

Targeting MYC dependence in cancer by inhibiting BET bromodomains.

The MYC transcription factor is a master regulator of diverse cellular functions and has been long considered a compelling therapeutic target because of its role in a range of human malignancies. However, pharmacologic inhibition of MYC function has proven challenging because of both the diverse mechanisms driving its aberrant expression and the challenge of disrupting protein-DNA interactions. Here, we demonstrate the rapid and potent abrogation of MYC gene transcription by representative small molecule inhibitors of the BET family of chromatin adaptors. MYC transcriptional suppression was observed in the context of the natural, chromosomally translocated, and amplified gene locus. Inhibition of BET bromodomain-promoter interactions and subsequent reduction of MYC transcript and protein levels resulted in G(1) arrest and extensive apoptosis in a variety of leukemia and lymphoma cell lines. Exogenous expression of MYC from an artificial promoter that is resistant to BET regulation significantly protected cells from cell cycle arrest and growth suppression by BET inhibitors. MYC suppression was accompanied by deregulation of the MYC transcriptome, including potent reactivation of the p21 tumor suppressor. Treatment with a BET inhibitor resulted in significant antitumor activity in xenograft models of Burkitt's lymphoma and acute myeloid leukemia. These findings demonstrate that pharmacologic inhibition of MYC is achievable through targeting BET bromodomains. Such inhibitors may have clinical utility given the widespread pathogenetic role of MYC in cancer.

Patient Questions Surrounding Posterior Nasal Nerve Ablation for Chronic Rhinitis.

Objective: In-office ablation of the posterior nasal nerve (PNN) has emerged as an effective treatment option for chronic rhinitis patients. This study explored questions patients commonly search online regarding this therapy and the quality of content available. Study Design: A retrospective analysis of online search criteria and sources was performed with subsequent analysis of results. Setting: Search and data acquisition was in September of 2023. Methods: Most common search terms related to cryotherapy and radiofrequency neurolysis of the PNN were identified with associated People Also Ask (PAA) questions. Questions were categorized and organized into subtopics and sources evaluated using readability and quality metrics. Results: A total of 255 unique PAA questions and 175 unique websites were identified. The most common subtopics were related to facts about chronic rhinitis (26.7%) and rhinitis treatment options (25.1%). Nearly a quarter (24.3%) of websites were from commercial sources. Quality metrics indicate difficult-to-read and low-quality materials. Conclusion: Existing online resources need improvement to provide patients material that is easier to read. Physicians counseling patients should be aware of these areas for adequate shared decision making.

Wakefulness affects synaptic and network activity by increasing extracellular astrocyte-derived adenosine.

Loss of sleep causes an increase in sleep drive and deficits in hippocampal-dependent memory. Both of these responses are thought to require activation of adenosine A1 receptors (adorA1Rs) and release of transmitter molecules including ATP, which is rapidly converted to adenosine in the extracellular space, from astrocytes in a process termed gliotransmission. Although it is increasingly clear that astrocyte-derived adenosine plays an important role in driving the homeostatic sleep response and the effects of sleep loss on memory (Halassa et al., 2009; Florian et al., 2011), previous studies have not determined whether the concentration of this signaling molecule increases in response to wakefulness. Here, we show that the level of adorA1R activation increases in response to wakefulness in mice (Mus musculus). We found that this increase affected synaptic transmission in the hippocampus and modulated network activity in the cortex. Direct biosensor-based measurement of adenosine showed that the net extracellular concentration of this transmitter increased in response to normal wakefulness and sleep deprivation. Genetic inhibition of gliotransmission prevented this increase and attenuated the wakefulness-dependent changes in synaptic and network regulation by adorA1R. Consequently, we conclude that wakefulness increases the level of extracellular adenosine in the hippocampus and that this increase requires the release of transmitters from astroctyes.

Sipuleucel-T immunotherapy for castration-resistant prostate cancer.

BACKGROUND: Sipuleucel-T, an autologous active cellular immunotherapy, has shown evidence of efficacy in reducing the risk of death among men with metastatic castration-resistant prostate cancer. METHODS: In this double-blind, placebo-controlled, multicenter phase 3 trial, we randomly assigned 512 patients in a 2:1 ratio to receive either sipuleucel-T (341 patients) or placebo (171 patients) administered intravenously every 2 weeks, for a total of three infusions. The primary end point was overall survival, analyzed by means of a stratified Cox regression model adjusted for baseline levels of serum prostate-specific antigen (PSA) and lactate dehydrogenase. RESULTS: In the sipuleucel-T group, there was a relative reduction of 22% in the risk of death as compared with the placebo group (hazard ratio, 0.78; 95% confidence interval [CI], 0.61 to 0.98; P=0.03). This reduction represented a 4.1-month improvement in median survival (25.8 months in the sipuleucel-T group vs. 21.7 months in the placebo group). The 36-month survival probability was 31.7% in the sipuleucel-T group versus 23.0% in the placebo group. The treatment effect was also observed with the use of an unadjusted Cox model and a log-rank test (hazard ratio, 0.77; 95% CI, 0.61 to 0.97; P=0.02) and after adjustment for use of docetaxel after the study therapy (hazard ratio, 0.78; 95% CI, 0.62 to 0.98; P=0.03). The time to objective disease progression was similar in the two study groups. Immune responses to the immunizing antigen were observed in patients who received sipuleucel-T. Adverse events that were more frequently reported in the sipuleucel-T group than in the placebo group included chills, fever, and headache. CONCLUSIONS: The use of sipuleucel-T prolonged overall survival among men with metastatic castration-resistant prostate cancer. No effect on the time to disease progression was observed. (Funded by Dendreon; ClinicalTrials.gov number, NCT00065442.)

An analysis of leukapheresis and central venous catheter use in the randomized, placebo controlled, phase 3 IMPACT trial of Sipuleucel-T for metastatic castrate resistant prostate cancer.

PURPOSE: Sipuleucel-T is an autologous cellular immunotherapy. We review the safety of the leukapheresis procedure required for sipuleucel-T preparation and complications related to venous catheter use in the randomized, placebo controlled phase 3 IMPACT (IMmunotherapy for ProstAte Cancer Trial) study (NCT 00065442). MATERIALS AND METHODS: A total of 512 patients with asymptomatic or minimally symptomatic metastatic castrate resistant prostate cancer were enrolled in the study. All patients were scheduled to undergo 3 standard 1.5 to 2.0 blood volume leukapheresis procedures at 2-week intervals. Leukapheresis related adverse events and those related to venous catheter use were reviewed. Immune cell counts were examined throughout the treatment course. RESULTS: Of 512 enrolled patients 506 underwent 1 or more leukapheresis procedures and were included in this analysis. Adverse events were comparable between the sipuleucel-T and control arms. Leukapheresis related adverse events were primarily associated with transient hypocalcemia (39.3%). Most leukapheresis related adverse events (97%) were of mild/moderate intensity. Median white blood cell count and absolute monocyte and lymphocyte counts were stable and within normal ranges throughout the treatment course. Of all patients 23.3% had a central venous catheter placed primarily for leukapheresis. Patients with vs without a central venous catheter had a higher risk of infection potentially related to catheter use (11.9% vs 1.3%, p <0.0001) and a trend toward a higher incidence of venous vascular events potentially related to catheter use, excluding the central nervous system (5.9% vs 2.1%, p = 0.06). CONCLUSIONS: Adverse events related to leukapheresis are manageable and quickly reversible. The majority of patients can undergo leukapheresis without a central venous catheter. Central venous catheters are associated with an increased risk of infections and venous vascular events. Peripheral intravenous access should be used when feasible.

Simultaneous measurement of tissue oxygen level-dependent (TOLD) and blood oxygenation level-dependent (BOLD) effects in abdominal tissue oxygenation level studies.

PURPOSE: To assess oxygenation in abdominal organs with magnetic resonance imaging (MRI), a novel approach is presented to simultaneously measure both T1 - and T2*-maps serially during a single dynamic MRI scan in response to an oxygen challenge. MATERIALS AND METHODS: The proposed acquisition scheme consists of a multishot multiecho gradient echo planar imaging sequence (ms-GEPI) interleaved with a multishot inversion recovery echo planar imaging (ms-IR-EPI) sequence. Respiratory motion compensation was accomplished with standard belt triggering and by acquiring all image data at the same phase of expiration. This respiratory-triggered, free-breathing, interleaved tissue oxygenation level-dependent (TOLD) and blood oxygenation level-dependent (BOLD) acquisition technique was validated on phantoms and seven healthy volunteers in response to an oxygen challenge. RESULTS: Measurements of relaxation times both in vitro and in vivo were in good agreement with those obtained using conventional pulse sequences and reported in the literature. The interleaved sequence was able to measure oxygen-induced relaxation time changes in human abdominal organs. CONCLUSION: The free-breathing respiratory-triggered interleaved T1 and T2* sequence successfully provided relaxation time maps of abdominal organs in a dynamic scan without the need for image registration. The simultaneous monitoring of tissue and blood oxygenation improves time efficiency and should enhance studies comparing dynamic T1 and T2* data within the abdomen.

Utility of clinical parameters, cystourethroscopy, and magnetic resonance imaging in the preoperative diagnosis of urethral diverticula.

INTRODUCTION AND HYPOTHESIS: Our purpose was to assess the accuracy of history and physical, cystourethroscopy, and magnetic resonance imaging (MRI) in preoperative diagnosis of urethral diverticula. METHODS: This was a retrospective review of all patients who underwent surgical excision of periurethral masses between 1998 and 2009. Presenting symptoms and examination and cystourethroscopic findings were noted. A single pathologist reviewed all cases and provided the reference standard for the diagnosis of a diverticulum. A single radiologist reviewed all preoperative MRI studies. Sensitivities, specificities, and positive and negative predictive values (PPV, NPV) were determined. RESULTS: Diverticula were diagnosed in 36/60 (60 %) patients. Transurethral fluid expression on palpation and recurrent urinary tract infection (UTI) had high PPV. Sensitivity, specificity, PPV, and NPV, respectively, for cystourethroscopy were 33 %, 100 %, 100 %, and 42 %; for MRI, these were 100 %, 83 %, 92 %, and 100 %. CONCLUSION: These data reinforce the utility of transurethral fluid expression for preoperative evaluation of urethral diverticula. Additionally, MRI is an excellent adjunctive diagnostic tool and may assist in establishing the diagnosis when there is high clinical suspicion of a urethral diverticulum but nonconfirmatory findings on cystourethroscopy.

Bop encodes a muscle-restricted protein containing MYND and SET domains and is essential for cardiac differentiation and morphogenesis.

Many transcription factors regulate specific temporal-spatial events during cardiac differentiation; however, the mechanisms that regulate such events are largely unknown. Using a modified subtractive hybridization method to identify specific genes that influence early cardiac development, we found that Bop is expressed specifically in cardiac and skeletal muscle precursors before differentiation of these lineages. Bop encodes a protein containing MYND and SET domains, which have been shown to regulate transcription by mediating distinct chromatin modifications. We show that m-Bop is a histone deacetylase-dependent transcriptional repressor. Targeted deletion of Bop in mice disrupted maturation of ventricular cardiomyocytes and interfered with formation of the right ventricle. Normal expression of Hand2, a transcription factor essential for right ventricular development, in cardiomyocyte precursors is dependent upon m-Bop. These results indicate that m-Bop is essential for cardiomyocyte differentiation and cardiac morphogenesis.

Lysine Methyltransferase SMYD1 Regulates Myogenesis via skNAC Methylation.

The SMYD family is a unique class of lysine methyltransferases (KMTases) whose catalytic SET domain is split by a MYND domain. Among these, Smyd1 was identified as a heart- and skeletal muscle-specific KMTase and is essential for cardiogenesis and skeletal muscle development. SMYD1 has been characterized as a histone methyltransferase (HMTase). Here we demonstrated that SMYD1 methylates is the Skeletal muscle-specific splice variant of the Nascent polypeptide-Associated Complex (skNAC) transcription factor. SMYD1-mediated methylation of skNAC targets K1975 within the carboxy-terminus region of skNAC. Catalysis requires physical interaction of SMYD1 and skNAC via the conserved MYND domain of SMYD1 and the PXLXP motif of skNAC. Our data indicated that skNAC methylation is required for the direct transcriptional activation of myoglobin (Mb), a heart- and skeletal muscle-specific hemoprotein that facilitates oxygen transport. Our study revealed that the skNAC, as a methylation target of SMYD1, illuminates the molecular mechanism by which SMYD1 cooperates with skNAC to regulate transcriptional activation of genes crucial for muscle functions and implicates the MYND domain of the SMYD-family KMTases as an adaptor to target substrates for methylation.

Compressive sensing could accelerate 1H MR metabolic imaging in the clinic.

PURPOSE: To retrospectively evaluate the fidelity of magnetic resonance (MR) spectroscopic imaging data preservation at a range of accelerations by using compressed sensing. MATERIALS AND METHODS: The protocols were approved by the institutional review board of the university, and written informed consent to acquire and analyze MR spectroscopic imaging data was obtained from the subjects prior to the acquisitions. This study was HIPAA compliant. Retrospective application of compressed sensing was performed on 10 clinical MR spectroscopic imaging data sets, yielding 600 voxels from six normal brain data sets, 163 voxels from two brain tumor data sets, and 36 voxels from two prostate cancer data sets for analysis. The reconstructions were performed at acceleration factors of two, three, four, five, and 10 and were evaluated by using the root mean square error (RMSE) metric, metabolite maps (choline, creatine, N-acetylaspartate [NAA], and/or citrate), and statistical analysis involving a voxelwise paired t test and one-way analysis of variance for metabolite maps and ratios for comparison of the accelerated reconstruction with the original case. RESULTS: The reconstructions showed high fidelity for accelerations up to 10 as determined by the low RMSE (< 0.05). Similar means of the metabolite intensities and hot-spot localization on metabolite maps were observed up to a factor of five, with lack of statistically significant differences compared with the original data. The metabolite ratios of choline to NAA and choline plus creatine to citrate did not show significant differences from the original data for up to an acceleration factor of five in all cases and up to that of 10 for some cases. CONCLUSION: A reduction of acquisition time by up to 80%, with negligible loss of information as evaluated with clinically relevant metrics, has been successfully demonstrated for hydrogen 1 MR spectroscopic imaging.