Proteomic Discovery of RNA-Protein Molecular Clamps Using a Thermal Shift Assay with ATP and RNA (TSAR)

Uncompetitive inhibition is an effective strategy for suppressing dysregulated enzymes and their substrates, but discovery of suitable ligands depends on often-unavailable structural knowledge and serendipity. Hence, despite surging interest in mass spectrometry-based target identification, proteomic studies of substrate-dependent target engagement remain sparse. Herein, we describe the Thermal Shift Assay with ATP and RNA (TSAR) as a template for proteome-wide discovery of substrate-dependent ligand binding. Using proteomic thermal shift assays, we show that simple biochemical additives can facilitate detection of target engagement in native cell lysates. We apply our approach to rocaglates, a family of molecules that specifically clamp RNA to eukaryotic translation initiation factor 4A (eIF4A), DEAD-box helicase 3X (DDX3X), and potentially other members of the DEAD-box (DDX) family of RNA helicases. To identify unexpected interactions, we optimized a target class-specific thermal denaturation window and evaluated ATP analog and RNA probe dependencies for key rocaglate-DDX interactions. We report novel DDX targets of the rocaglate clamping spectrum, confirm that DDX3X is a common target of several widely studied analogs, and provide structural insights into divergent DDX3X affinities between synthetic rocaglates. We independently validate novel targets of high-profile rocaglates, including the clinical candidate Zotatifin (eFT226), using limited proteolysis-mass spectrometry and fluorescence polarization experiments. Taken together, our study provides a model for screening uncompetitive inhibitors using a systematic chemical-proteomics approach to uncover actionable DDX targets, clearing a path towards characterization of novel molecular clamps and associated RNA helicase targets.

A chemical screen identifies structurally diverse metal chelators with activity against the fungal pathogen Candida albicans

Candida albicans, one of the most prevalent human fungal pathogens, causes diverse diseases extending from superficial infections to deadly systemic mycoses. Currently, only three major classes of antifungal drugs are available to treat systemic infections: azoles, polyenes, and echinocandins. Alarmingly, the efficacy of these antifungals against C. albicans is hindered both by basal tolerance toward the drugs and the development of resistance mechanisms such as alterations of the drug's target, modulation of stress responses, and overexpression of efflux pumps. Thus, the need to identify novel antifungal strategies is dire. To address this challenge, we screened 3,049 structurally-diverse compounds from the Boston University Center for Molecular Discovery (BU-CMD) chemical library against a C. albicans clinical isolate and identified 17 molecules that inhibited C. albicans growth by >80% relative to controls. Among the most potent compounds were CMLD013360, CMLD012661, and CMLD012693, molecules representing two distinct chemical scaffolds, including 3-hydroxyquinolinones and a xanthone natural product. Based on structural insights, CMLD013360, CMLD012661, and CMLD012693 were hypothesized to exert antifungal activity through metal chelation. Follow-up investigations revealed all three compounds exerted antifungal activity against non-albicans Candida, including Candida auris and Candida glabrata, with the xanthone natural product CMLD013360 also displaying activity against the pathogenic mould Aspergillus fumigatus. Media supplementation with metallonutrients, namely ferric or ferrous iron, rescued C. albicans growth, confirming these compounds act as metal chelators. Thus, this work identifies and characterizes two chemical scaffolds that chelate iron to inhibit the growth of the clinically relevant fungal pathogen C. albicansIMPORTANCEThe worldwide incidence of invasive fungal infections is increasing at an alarming rate. Systemic candidiasis caused by the opportunistic pathogen Candida albicans is the most common cause of life-threatening fungal infection. However, due to the limited number of antifungal drug classes available and the rise of antifungal resistance, an urgent need exists for the identification of novel treatments. By screening a compound collection from the Boston University Center for Molecular Discovery (BU-CMD), we identified three compounds representing two distinct chemical scaffolds that displayed activity against C. albicans. Follow-up analyses confirmed these molecules were also active against other pathogenic fungal species including Candida auris and Aspergillus fumigatus. Finally, we determined that these compounds inhibit the growth of C. albicans in culture through iron chelation. Overall, this observation describes two novel chemical scaffolds with antifungal activity against diverse fungal pathogens.

Synthesis of Neocannabinoids Using Controlled Friedel-Crafts Reactions

A one-step transformation to produce 8,9-dihydrocannabidiol (H2CBD) and related "neocannabinoids" via controlled Friedel-Crafts reactions is reported. Experimental and computational studies probing the mechanism of neocannabinoid synthesis from cyclic allylic alcohol and substituted resorcinol reaction partners provide understanding of the kinetic and thermodynamic factors driving regioselectivity for the reaction. Herein, we present the reaction scope for neocannabinoid synthesis including the production of both normal and abnormal isomers under both kinetic and thermodynamic control. Discovery and optimization of this one-step protocol between various allylic alcohols and resorcinol derivatives are discussed and supported with density functional theory calculations.

Exploring the targeting spectrum of rocaglates among eIF4A homologs

Inhibition of eukaryotic translation initiation through unscheduled RNA clamping of the DEAD-box (DDX) RNA helicases eIF4A1 and eIF4A2 has been documented for pateamine A (PatA) and rocaglates-two structurally different classes of compounds that share overlapping binding sites on eIF4A. Clamping of eIF4A to RNA causes steric blocks that interfere with ribosome binding and scanning, rationalizing the potency of these molecules since not all eIF4A molecules need to be engaged to elicit a biological effect. In addition to targeting translation, PatA and analogs have also been shown to target the eIF4A homolog, eIF4A3-a helicase necessary for exon junction complex (EJC) formation. EJCs are deposited on mRNAs upstream of exon-exon junctions and, when present downstream from premature termination codons (PTCs), participate in nonsense-mediated decay (NMD), a quality control mechanism aimed at preventing the production of dominant-negative or gain-of-function polypeptides from faulty mRNA transcripts. We find that rocaglates can also interact with eIF4A3 to induce RNA clamping. Rocaglates also inhibit EJC-dependent NMD in mammalian cells, but this does not appear to be due to induced eIF4A3-RNA clamping, but rather a secondary consequence of translation inhibition incurred by clamping eIF4A1 and eIF4A2 to mRNA.

Glacier retreat reorganizes river habitats leaving refugia for Alpine invertebrate biodiversity poorly protected

Alpine river biodiversity around the world is under threat from glacier retreat driven by rapid warming, yet our ability to predict the future distributions of specialist cold-water species is currently limited. Here we link future glacier projections, hydrological routing methods and species distribution models to quantify the changing influence of glaciers on population distributions of 15 alpine river invertebrate species across the entire European Alps, from 2020 to 2100. Glacial influence on rivers is projected to decrease steadily, with river networks expanding into higher elevations at a rate of 1% per decade. Species are projected to undergo upstream distribution shifts where glaciers persist but become functionally extinct where glaciers disappear completely. Several alpine catchments are predicted to offer climate refugia for cold-water specialists. However, present-day protected area networks provide relatively poor coverage of these future refugia, suggesting that alpine conservation strategies must change to accommodate the future effects of global warming.

Patients' Perceived Level of Clinician Knowledge of Transgender Health Care, Self-rated Health, and Psychological Distress Among Transgender Adults

Importance

Transgender, gender nonbinary, and genderqueer people are at increased risk for negative health outcomes, and medical school education is currently lacking on inclusion of these topics. However, there is little evidence of an association of clinician knowledge with the health of transgender people.

Objective

To evaluate the associations of patients' perceptions of clinician knowledge with self-rated health and severe psychological distress among transgender people.

Design, Setting, and Participants

In this cross-sectional study, a secondary data analysis of the 2015 US Transgender Survey (a survey of transgender, gender nonbinary, and genderqueer adults conducted across 50 states) Washington, DC, US territories, and US military bases in 2015 was performed. Data were analyzed from February to November 2022.

Exposures

Patients' perception of their clinician's knowledge about transgender health care.

Main Outcomes and Measures

Self-rated health, dichotomized as poor or fair vs excellent, very good, or good, and severe psychological distress (scoring a validated threshold of ≥13 on the Kessler Psychological Distress Scale).

Results

The sample included a total of 27 715 respondents (9238 transgender women [33.3%; 55.1% weighted; 95% CI, 53.4%-56.7%], 22 658 non-Hispanic White individuals [81.8%; 65.6% weighted; 95% CI, 63.7%-67.5%], and 4085 individuals aged 45-64 years [14.7%; 33.8% weighted; 95% CI, 32.0%-35.5%]). Of 23 318 individuals who answered questions regarding their perceptions of their clinicians' level of knowledge, 5732 (24.6%) reported their clinician knows almost everything about transgender care, 4083 (17.5%) reported their clinician knows most things, 3446 (14.8%) reported their clinician knows some things, 2680 (11.5%) reported their clinician knows almost nothing, and 7337 (31.5%) reported they were unsure. Nearly 1 in 4 transgender adults (5612 of 23 557 individuals [23.8%]) reported having to teach their clinician about transgender people. In total, 3955 respondents (19.4%; 20.8% weighted; 95% CI, 19.2%-22.6%) reported fair or poor self-rated health and 7392 (36.9%; 28.4% weighted, 95% CI, 26.9%-30.1%) met the criteria for severe psychological distress. After adjusting for covariates, compared with individuals who reported their clinician knows almost everything about transgender care, exposure to clinicians with lower perceived levels of knowledge about transgender care was associated with significantly higher odds of fair or poor self-rated health (adjusted odds ratio [aOR] for knowing almost nothing, 2.63; 95% CI, 1.76-3.94; aOR for unsure, 1.81; 95% CI, 1.28-2.56) and severe psychological distress (aOR for knowing almost nothing, 2.33; 95% CI, 1.61-3.37; aOR for unsure, 1.37; 95% CI, 1.05-1.79). Respondents who had to teach a clinician about transgender people had higher odds of reporting fair or poor self-rated health (aOR, 1.67; 95% CI, 1.31-2.13) and severe psychological distress (aOR, 1.49; 95% CI, 1.21-1.83) compared with those who did not.

Conclusion and Relevance

The findings of this cross-sectional study suggest that there is an association between perceived clinician knowledge about transgender people and self-rated health and psychological distress among transgender people. These results highlight the importance of integration and enhancement of transgender health in medical education curriculum as a necessary intervention to improve the health of transgender people.

Discovery of pyrazolopyrrolidinones as potent, broad-spectrum inhibitors of Leishmania infection

Introduction

Leishmaniasis is a parasitic disease that affects more than 1 million people worldwide annually, predominantly in resource-limited settings. The challenge in compound development is to exhibit potent activity against the intracellular stage of the parasite (the stage present in the mammalian host) without harming the infected host cells. We have identified a compound series (pyrazolopyrrolidinones) active against the intracellular parasites of Leishmania donovani and L. major; the causative agents of visceral and cutaneous leishmaniasis in the Old World, respectively.

Methods

In this study, we performed medicinal chemistry on a newly discovered antileishmanial chemotype, with over 100 analogs tested. Studies included assessments of antileishmanial potency, toxicity towards host cells, and in vitro ADME screening of key drug properties.

Results and discussion

Members of the series showed high potency against the deadliest form, visceral leishmaniasis (approximate EC₅₀ ≥ 0.01 μM without harming the host macrophage up to 10.0 μM). In comparison, the most efficient monotherapy treatment for visceral leishmaniasis is amphotericin B, which presents similar activity in the same assay (EC₅₀ = 0.2 μM) while being cytotoxic to the host cell at 5.0 μM. Continued development of this compound series with the Discovery Partnership with Academia (DPAc) program at the GlaxoSmithKline Diseases of the Developing World (GSK DDW) laboratories found that the compounds passed all of GSK's criteria to be defined as a potential lead drug series for leishmaniasis.

Conclusion

Here, we describe preliminary structure-activity relationships for antileishmanial pyrazolopyrrolidinones, and our progress towards the identification of candidates for future in vivo assays in models of visceral and cutaneous leishmaniasis.

BRCA mutational status shapes the stromal microenvironment of pancreatic cancer linking clusterin expression in cancer associated fibroblasts with HSF1 signaling

Tumors initiate by mutations in cancer cells, and progress through interactions of the cancer cells with non-malignant cells of the tumor microenvironment. Major players in the tumor microenvironment are cancer-associated fibroblasts (CAFs), which support tumor malignancy, and comprise up to 90% of the tumor mass in pancreatic cancer. CAFs are transcriptionally rewired by cancer cells. Whether this rewiring is differentially affected by different mutations in cancer cells is largely unknown. Here we address this question by dissecting the stromal landscape of BRCA-mutated and BRCA Wild-type pancreatic ductal adenocarcinoma. We comprehensively analyze pancreatic cancer samples from 42 patients, revealing different CAF subtype compositions in germline BRCA-mutated vs. BRCA Wild-type tumors. In particular, we detect an increase in a subset of immune-regulatory clusterin-positive CAFs in BRCA-mutated tumors. Using cancer organoids and mouse models we show that this process is mediated through activation of heat-shock factor 1, the transcriptional regulator of clusterin. Our findings unravel a dimension of stromal heterogeneity influenced by germline mutations in cancer cells, with direct implications for clinical research.

Inhibition of the Translation Initiation Factor eIF4A Enhances Tumor Cell Radiosensitivity

A fundamental component of cellular radioresponse is the translational control of gene expression. Because a critical regulator of translational control is the eukaryotic translation initiation factor 4F (eIF4F) cap binding complex, we investigated whether eIF4A, the RNA helicase component of eIF4F, can serve as a target for radiosensitization. Knockdown of eIF4A using siRNA reduced translational efficiency, as determined from polysome profiles, and enhanced tumor cell radiosensitivity as determined by clonogenic survival. The increased radiosensitivity was accompanied by a delayed dispersion of radiation-induced γH2AX foci, suggestive of an inhibition of DNA double-strand break repair. Studies were then extended to (-)-SDS-1-021, a pharmacologic inhibitor of eIF4A. Treatment of cells with the rocaglate (-)-SDS-1-021 resulted in a decrease in translational efficiency as well as protein synthesis. (-)-SDS-1-021 treatment also enhanced the radiosensitivity of tumor cell lines. This (-)-SDS-1-021-induced radiosensitization was accompanied by a delay in radiation-induced γH2AX foci dispersal, consistent with a causative role for the inhibition of double-strand break repair. In contrast, although (-)-SDS-1-021 inhibited translation and protein synthesis in a normal fibroblast cell line, it had no effect on radiosensitivity of normal cells. Subcutaneous xenografts were then used to evaluate the in vivo response to (-)-SDS-1-021 and radiation. Treatment of mice bearing subcutaneous xenografts with (-)-SDS-1-021 decreased tumor translational efficiency as determined by polysome profiles. Although (-)-SDS-1-021 treatment alone had no effect on tumor growth, it significantly enhanced the radiation-induced growth delay. These results suggest that eIF4A is a tumor-selective target for radiosensitization.

Identification of structurally re-engineered rocaglates as inhibitors against hepatitis E virus replication

Hepatitis E virus (HEV) infections are a leading cause of acute viral hepatitis in humans and pose a considerable threat to public health. Current standard of care treatment is limited to the off-label use of nucleoside-analog ribavirin (RBV) and PEGylated interferon-α, both of which are associated with significant side effects and provide limited efficacy. In the past few years, a promising natural product compound class of eukaryotic initiation factor 4A (eIF4A) inhibitors (translation initiation inhibitors), called rocaglates, were identified as antiviral agents against RNA virus infections. In the present study, we evaluated a total of 205 synthetic rocaglate derivatives from the BU-CMD compound library for their antiviral properties against HEV. At least eleven compounds showed inhibitory activities against the HEV genotype 3 (HEV-3) subgenomic replicon below 30 nM (EC₅₀ value) as determined by Gaussia luciferase assay. Three amidino-rocaglates (ADRs) (CMLD012073, CMLD012118, and CMLD012612) possessed antiviral activity against HEV with EC₅₀ values between 1 and 9 nM. In addition, these three selected compounds inhibited subgenomic replicons of different genotypes (HEV-1 [Sar55], wild boar HEV-3 [83-2] and human HEV-3 [p6]) in a dose-dependent manner and at low nanomolar concentrations. Furthermore, tested ADRs tend to be better tolerated in primary hepatocytes than hepatoma cancer cell lines and combination treatment of CMLD012118 with RBV and interferon-α (IFN-α) showed that CMLD012118 acts additive to RBV and IFN-α treatment. In conclusion, our results indicate that ADRs, especially CMLD012073, CMLD012118, and CMLD012612 may prove to be potential therapeutic candidates for the treatment of HEV infections and may contribute to the discovery of pan-genotypic inhibitors in the future.

Neighborhood cohesion and psychological distress across race and sexual orientation

Introduction

Method

Result

Conclusion

•

Lesbian, gay, and bisexual (LGB) people are more likely to meet the criteria for psychological distress than non-LGB people.

•

Neighborhood cohesion (NC) has differing impact on psychological distress by race and sexual orientation.

•

NC provides greater protection against moderate distress for non-LGB groups and severe psychological distress for LGB groups.

Divergent, C-C Bond Forming Macrocyclizations Using Modular Sulfonylhydrazone and Derived Substrates

A divergent approach to C-C bond forming macrocycle construction is described. Modular sulfonylhydrazone and derived pyridotriazole substrates with three key building blocks have been constructed and cyclized to afford diverse macrocyclic frameworks. Broad substrate scope and functional group tolerance have been demonstrated. In addition, site-selective postfunctionalization allowed for further diversification of macrocyclic cores.

Socioeconomic Disadvantage and Distance to Pediatric Critical Care

OBJECTIVES

To describe the geography of pediatric critical care services and the relationship between poverty and distance to these services across the United States.

DESIGN

Retrospective, cross-sectional study.

SETTING

Contiguous United States.

PATIENTS

Children less than 18 years as represented in the 2016 American Community Survey.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Pediatric critical care services were geographically concentrated within urban areas, with half of all PICUs located within 9.5 miles of another (interquartile range, 3.4-51.5 miles). Median distances from neighborhoods to the nearest unit increased linearly with Area Deprivation Index (p < 0.001), such that the median distance from the least privileged neighborhoods was nearly three times that of the most privileged neighborhoods (first decile = 7.8 miles [interquartile range, 3.4-15.8 miles] vs tenth decile = 22.6 miles [interquartile range, 4.2-52.5 miles]; p < 0.001). A relationship between neighborhood poverty and distance to a PICU was present across all U.S. regions and within urban/suburban and rural areas.

CONCLUSIONS

In the United States, the distance to pediatric critical care services increases with poverty. This carries implications for access to care and health outcome disparities.

Condensation tendency and planar isotropic actin gradient induce radial alignment in confined monolayers

A monolayer of highly motile cells can establish long-range orientational order, which can be explained by hydrodynamic theory of active gels and fluids. However, it is less clear how cell shape changes and rearrangement are governed when the monolayer is in mechanical equilibrium states when cell motility diminishes. In this work, we report that rat embryonic fibroblasts (REF), when confined in circular mesoscale patterns on rigid substrates, can transition from the spindle shapes to more compact morphologies. Cells align radially only at the pattern boundary when they are in the mechanical equilibrium. This radial alignment disappears when cell contractility or cell-cell adhesion is reduced. Unlike monolayers of spindle-like cells such as NIH-3T3 fibroblasts with minimal intercellular interactions or epithelial cells like Madin-Darby canine kidney (MDCK) with strong cortical actin network, confined REF monolayers present an actin gradient with isotropic meshwork, suggesting the existence of a stiffness gradient. In addition, the REF cells tend to condense on soft substrates, a collective cell behavior we refer to as the 'condensation tendency'. This condensation tendency, together with geometrical confinement, induces tensile prestretch (i.e. an isotropic stretch that causes tissue to contract when released) to the confined monolayer. By developing a Voronoi-cell model, we demonstrate that the combined global tissue prestretch and cell stiffness differential between the inner and boundary cells can sufficiently define the cell radial alignment at the pattern boundary.

Channeling macrophage polarization by rocaglates increases macrophage resistance to Mycobacterium tuberculosis

Macrophages contribute to host immunity and tissue homeostasis via alternative activation programs. M1-like macrophages control intracellular bacterial pathogens and tumor progression. In contrast, M2-like macrophages shape reparative microenvironments that can be conducive for pathogen survival or tumor growth. An imbalance of these macrophages phenotypes may perpetuate sites of chronic unresolved inflammation, such as infectious granulomas and solid tumors. We have found that plant-derived and synthetic rocaglates sensitize macrophages to low concentrations of the M1-inducing cytokine IFN-gamma and inhibit their responsiveness to IL-4, a prototypical activator of the M2-like phenotype. Treatment of primary macrophages with rocaglates enhanced phagosome-lysosome fusion and control of intracellular mycobacteria. Thus, rocaglates represent a novel class of immunomodulators that can direct macrophage polarization toward the M1-like phenotype in complex microenvironments associated with hypofunction of type 1 and/or hyperactivation of type 2 immunity, e.g., chronic bacterial infections, allergies, and, possibly, certain tumors.

Abstract LB204: HSF1 promotes inflammation induced tumor development through ECM remodeling

HSF1 promotes inflammation induced tumor development through ECM remodelingAbstractIn the colon, long-term exposure to chronic inflammation drives colitis associated colon cancer (CAC) in patients with inflammatory bowel disease (IBD). Chronic inflammation underlies tumor initiation, promotion, invasion, and metastasis. While the causal and clinical link between chronic inflammation and CAC is well established, we lack a molecular understanding of what is the way in which chronic inflammation leads to develop colon cancer. Within the tumor, cancer cells are surrounded by a variety of non-malignant cells, such as macrophages, endothelial cells, neutrophils, cancer-associated fibroblasts (CAFs), and together with the extracellular matrix (ECM) they compose the tumor microenvironment (TME), also termed the stroma. Even the most aggressive cancers depend and interact with their environment mostly through secreted factors. Unlike cancer cells, stromal cells are genomically stable, and do not harbor oncogenic mutations that could drive their co-evolution and functional reprogramming. Rather, stromal reprogramming is thought to be achieved by transcriptional rewiring. Previous work by us and others has shown that the master regulator heat shock factor 1 (HSF1) plays a crucial role in this process, by mediating a transcriptional program in fibroblasts that enables their reprogramming into cancer-associated fibroblasts (CAFs) to promote malignancy. We hypothesizde that HSF1 plays a crucial role in inflammation-driven cancer by initiation of a transcriptional program that leads to changes in the extracellular matrix (ECM). We found that, in cell culture, cancer-induced ECM assembly by fibroblasts requires HSF1. Using an inflammation-driven cancer model in mice, we measured the changes in proteomic and ECM organization over time. We found that HSF1 drives a transcriptional program that leads to ECM remodeling in early stages and results in development of colon cancer. Loss of HSF1 prevents inflammation-induced ECM remodeling. Further to that, in CAC patients, we found high activation of stromal HSF1 and similarity to our HSF1 proteomic ECM signature in human colorectal cancer driven by HSF1. Thus, HSF1-dependent ECM remodeling mediates the transition from chronic inflammation to colon cancer.

Citation Format: Oshrat Levi Galibov, Hagar Lavon, Rina Wassermann-Dozorets, Meirav Pevsner-Fischer, Shimrit Mayer, Esther Wershof, Yaniv Stein, Lauren E. Brown, Wenhan Zhang, Gil Friedman, Reinat Nevo, Ofra Golani, Lior H. Katz, Rona Yaeger, Ido Laish, John A. Porco, Erik Sahai, Dror S Shouval, David Kelsen, Ruth Scherz-Shouval. HSF1 promotes inflammation induced tumor development through ECM remodeling [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr LB204.

Sources of 2,3,7,8-Tetrachlorodibenzo-p-dioxin and Other Dioxins in Lower Passaic River, New Jersey, Sediments

Elevated levels of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and other contaminants have been reported in lower Passaic River, New Jersey, USA, sediments since the 1980s. Nearly 8000 surficial and buried sediment samples have been collected along the 17 miles (27.4 km) of river and analyzed for various contaminants, including the seventeen 2,3,7,8-substituted PCDD/F congeners. Principal component analysis and hierarchical cluster analysis reveal spatial heterogeneity in the distribution of dioxin congeners, with respect to both sediment depth and river mile. Polytopic vector analysis resolved 11 unique 2,3,7,8-substituted dioxin congener profiles in the river sediment. The profiles were consistent with multiple dioxin source types, including manufacture of certain dyes and pigments, chlorinated industrial chemicals, hexachlorophene, polychlorinated biphenyls, waste disposal and incineration, the production and use of 2,4,5-trichorophenol (2,4,5-TCP), and other industrial processes. The distribution of dioxin profiles in surface and buried river sediments is indicative of multiple inputs of 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) and other dioxins at different locations along the lower Passaic River. These findings are inconsistent with historical claims that a former herbicide manufacturing plant in the lower reach of the river is the only significant 2,3,7,8-TCDD source and consistent with evidence of several different inputs associated with the production, use, and/or disposal of 2,4,5-TCP at several locations along the lower Passaic River. Environ Toxicol Chem 2021;40:1499-1519. © 2020 SETAC.

Rocaglates Induce Gain-of-Function Alterations to eIF4A and eIF4F

Rocaglates are a diverse family of biologically active molecules that have gained tremendous interest in recent years due to their promising activities in pre-clinical cancer studies. As a result, this family of compounds has been significantly expanded through the development of efficient synthetic schemes. However, it is unknown whether all of the members of the rocaglate family act through similar mechanisms of action. Here, we present a comprehensive study comparing the biological activities of >200 rocaglates to better understand how the presence of different chemical entities influences their biological activities. Through this, we find that most rocaglates preferentially repress the translation of mRNAs containing purine-rich 5′ leaders, but certain rocaglates lack this bias in translation repression. We also uncover an aspect of rocaglate mechanism of action in which the pool of translationally active eIF4F is diminished due to the sequestration of the complex onto RNA.

Rocaglates are a diverse family of small molecules that inhibit eIF4A. Chu et al. undertake a comparative analysis of the bioactivity of >200 rocaglates and uncover nuances in their mechanisms of action. Rocaglates interfere with eIF4F release from the cap and exert a bystander effect to inhibit translation.

Defining and navigating macrocycle chemical space

Macrocyclic compounds (MCs) are of growing interest for inhibition of challenging drug targets. We consider afresh what structural and physicochemical features could be relevant to the bioactivity of this compound class. Using these features, we performed Principal Component Analysis to map oral and non-oral macrocycle drugs and clinical candidates, and also commercially available synthetic MCs, in structure–property space. We find that oral MC drugs occupy defined regions that are distinct from those of the non-oral MC drugs. None of the oral MC regions are effectively sampled by the synthetic MCs. We identify 13 properties that can be used to design synthetic MCs that sample regions overlapping with oral MC drugs. The results advance our understanding of what molecular features are associated with bioactive and orally bioavailable MCs, and illustrate an approach by which synthetic chemists can better evaluate MC designs. We also identify underexplored regions of macrocycle chemical space.

Macrocyclic compounds (MCs) are of high interest for inhibition of challenging drug targets, but existing oral MC drugs occupy regions of chemical space that are not well sampled by many available synthetic MC chemotypes.

Fungal-Selective Resorcylate Aminopyrazole Hsp90 Inhibitors: Optimization of Whole-Cell Anticryptococcal Activity and Insights into the Structural Origins of Cryptococcal Selectivity

The essential eukaryotic chaperone Hsp90 regulates the form and function of diverse client proteins, many of which govern thermotolerance, virulence, and drug resistance in fungal species. However, use of Hsp90 inhibitors as antifungal therapeutics has been precluded by human host toxicities and suppression of immune responses. We recently described resorcylate aminopyrazoles (RAPs) as the first class of Hsp90 inhibitors capable of discriminating between fungal (Cryptococcus neoformans, Candida albicans) and human isoforms of Hsp90 in biochemical assays. Here, we report an iterative structure-property optimization toward RAPs capable of inhibiting C. neoformans growth in culture. In addition, we report the first X-ray crystal structures of C. neoformans Hsp90 nucleotide binding domain (NBD), as the apoprotein and in complexes with the non-species-selective Hsp90 inhibitor NVP-AUY922 and three RAPs revealing unique ligand-induced conformational rearrangements, which reaffirm the hypothesis that intrinsic differences in protein flexibility can confer selective inhibition of fungal versus human Hsp90 isoforms.

Heat Shock Factor 1-dependent extracellular matrix remodeling mediates the transition from chronic intestinal inflammation to colon cancer

In the colon, long-term exposure to chronic inflammation drives colitis-associated colon cancer (CAC) in patients with inflammatory bowel disease. While the causal and clinical links are well established, molecular understanding of how chronic inflammation leads to the development of colon cancer is lacking. Here we deconstruct the evolving microenvironment of CAC by measuring proteomic changes and extracellular matrix (ECM) organization over time in a mouse model of CAC. We detect early changes in ECM structure and composition, and report a crucial role for the transcriptional regulator heat shock factor 1 (HSF1) in orchestrating these events. Loss of HSF1 abrogates ECM assembly by colon fibroblasts in cell-culture, prevents inflammation-induced ECM remodeling in mice and inhibits progression to CAC. Establishing relevance to human disease, we find high activation of stromal HSF1 in CAC patients, and detect the HSF1-dependent proteomic ECM signature in human colorectal cancer. Thus, HSF1-dependent ECM remodeling plays a crucial role in mediating inflammation-driven colon cancer.

Abstract 6507: Inhibition of the translation initiation factor eIF4A1 enhances tumor cell radiosensitivity

The cellular radioresponse is regulated by constitutively expressed proteins and by new gene expression. We have previously shown that radiation induces changes in gene expression primarily via translational control. Regulation of gene translation largely occurs at the initiation stage, and many factors that regulate initiation impact the eukaryotic translation initiation factor 4F (eIF4F) complex. eIF4F is comprised of the cap-binding protein eIF4E, the RNA helicase eIF4A, and the scaffold protein eIF4G. Because eIF4A is considered to regulate the translation of mRNAs involved in cell survival and proliferation, we investigated it as a target for tumor cell radiosensitization. Knockdown of eIF4A1 in the U251 glioblastoma and the HeLa cervical carcinoma cell lines resulted in a decrease in translational efficiency as determined by polysome profiling and an increase in cellular radiosensitivity as determined by clonogenic survival analysis. There was also an increase in γH2AX foci remaining at 24h after irradiation, consistent with an inhibition of DNA double strand break repair. These results suggest that eIF4A serves as a determinant of cellular radiosensitivity. As an additional approach to inhibiting eIF4A, we utilized the rocaglate hydroxamate (-)-SDS-1-021, which prevents eIF4A inclusion into eIF4F. Treatment of U251, HeLa and PSN1 pancreatic carcinoma cells with 10 nM (-)-SDS-1-021 resulted in decreased translational efficiency, which was accompanied by a decrease in protein synthesis. Treatment of the tumor cell lines with (-)-SDS-1-021 immediately before radiation resulted in an increase in radiosensitivity as well as an increase in γH2AX foci remaining at 24h, similar to eIF4A1 knockdown. Importantly, whereas treatment of the normal human fibroblast cell line MRC9 with (-)-SDS-1-021 also inhibited translation and protein synthesis, there was no effect on radiosensitivity. To gain a better understanding of the mechanism of radiosensitization by (-)-SDS-1-021, RNAseq was performed using polysome-bound mRNAs isolated from U251 and MRC9 cells. Cells were treated with 10 nM (-)-SDS-1-021, immediately irradiated (2Gy), and then harvested six hours post-irradiation. In U251 cells treated with 2Gy alone, 192 genes were translationally upregulated. The upregulation of 160 of these genes was inhibited by (-)-SDS-1-021 in the combination treatment group. Similarly, in MRC9 cells, 322 genes were translationally upregulated in response to radiation, and the upregulation of 173 of these was inhibited in the combination treatment group. By Ingenuity Pathway Analysis, the radiation-induced, (-)-SDS-1-021-sensitive genes in U251 were significantly enriched for proteins involved in DNA replication, recombination, and repair, which is in contrast to the MRC9 (-)-SDS-1-021 genes. Altogether, these findings suggest that eIF4A1 is a viable target for tumor radiosensitization.

Citation Format: Stacey L. Lehman, Theresa Wechsler, Kayla R. Schwartz, Amy Wahba, Lauren E. Brown, John A. Porco, Jerry Pelletier, Kevin Camphausen, Philip J. Tofilon. Inhibition of the translation initiation factor eIF4A1 enhances tumor cell radiosensitivity [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 6507.

Small Molecule Amyloid-β Protein Precursor Processing Modulators Lower Amyloid-β Peptide Levels via cKit Signaling

Alzheimer's disease (AD) is characterized by the accumulation of neurotoxic amyloid-β (Aβ) peptides consisting of 39-43 amino acids, proteolytically derived fragments of the amyloid-β protein precursor (AβPP), and the accumulation of the hyperphosphorylated microtubule-associated protein tau. Inhibiting Aβ production may reduce neurodegeneration and cognitive dysfunction associated with AD. We have previously used an AβPP-firefly luciferase enzyme complementation assay to conduct a high throughput screen of a compound library for inhibitors of AβPP dimerization, and identified a compound that reduces Aβ levels. In the present study, we have identified an analog, compound Y10, which also reduced Aβ. Initial kinase profiling assays identified the receptor tyrosine kinase cKit as a putative Y10 target. To elucidate the precise mechanism involved, AβPP phosphorylation was examined by IP-western blotting. We found that Y10 inhibits cKit phosphorylation and increases AβPP phosphorylation mainly on tyrosine residue Y743, according to AβPP751 numbering. A known cKit inhibitor and siRNA specific to cKit were also found to increase AβPP phosphorylation and lower Aβ levels. We also investigated a cKit downstream signaling molecule, the Shp2 phosphatase, and found that known Shp2 inhibitors and siRNA specific to Shp2 also increase AβPP phosphorylation, suggesting that the cKit signaling pathway is also involved in AβPP phosphorylation and Aβ production. We further found that inhibitors of both cKit and Shp2 enhance AβPP surface localization. Thus, regulation of AβPP phosphorylation by small molecules should be considered as a novel therapeutic intervention for AD.

Design and Synthesis of Fungal-Selective Resorcylate Aminopyrazole Hsp90 Inhibitors

The molecular chaperone Hsp90, essential in all eukaryotes, plays a multifaceted role in promoting survival, virulence, and drug resistance across diverse pathogenic fungal species. The chaperone is also critically important, however, to the pathogen's human host, preventing the use of known clinical Hsp90 inhibitors in antifungal applications due to concomitant host toxicity issues. With the goal of developing Hsp90 inhibitors with acceptable therapeutic indices for the treatment of invasive fungal infections, we initiated a program to design and synthesize potent inhibitors with selective activity against fungal Hsp90 isoforms over their human counterparts. Building on our previously reported derivatization of resorcylate natural products to produce fungal-selective compounds, we have developed a series of synthetic aminopyrazole-substituted resorcylate amides with broad, potent, and fungal-selective Hsp90 inhibitory activity. Herein we describe the synthesis of this series, as well as biochemical structure-activity relationships driving selectivity for the Hsp90 isoforms expressed by Cryptococcus neoformans and Candida albicans, two pathogenic fungi of major clinical importance.

eIF4A supports an oncogenic translation program in pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDA) is a lethal malignancy with limited treatment options. Although metabolic reprogramming is a hallmark of many cancers, including PDA, previous attempts to target metabolic changes therapeutically have been stymied by drug toxicity and tumour cell plasticity. Here, we show that PDA cells engage an eIF4F-dependent translation program that supports redox and central carbon metabolism. Inhibition of the eIF4F subunit, eIF4A, using the synthetic rocaglate CR-1-31-B (CR-31) reduced the viability of PDA organoids relative to their normal counterparts. In vivo, CR-31 suppresses tumour growth and extends survival of genetically-engineered murine models of PDA. Surprisingly, inhibition of eIF4A also induces glutamine reductive carboxylation. As a consequence, combined targeting of eIF4A and glutaminase activity more effectively inhibits PDA cell growth both in vitro and in vivo. Overall, our work demonstrates the importance of eIF4A in translational control of pancreatic tumour metabolism and as a therapeutic target against PDA.

Amidino-Rocaglates: A Potent Class of eIF4A Inhibitors

Rocaglates share a common cyclopenta[b]benzofuran core that inhibits eukaryotic translation initiation by modifying the behavior of the RNA helicase, eIF4A. Working as interfacial inhibitors, rocaglates stabilize the association between eIF4A and RNA, which can lead to the formation of steric barriers that block initiating ribosomes. There is significant interest in the development and expansion of rocaglate derivatives, as several members of this family have been shown to possess potent anti-neoplastic activity in vitro and in vivo. To further our understanding of rocaglate diversity and drug design, herein we explore the RNA clamping activity of >200 unique rocaglate derivatives. Through this, we report on the identification and characterization of a potent class of synthetic rocaglates called amidino-rocaglates. These compounds are among the most potent rocaglates documented to date and, taken together, this work offers important information that will guide the future design of rocaglates with improved biological properties.

Intercepted Retro-Nazarov Reaction: Syntheses of Amidino-Rocaglate Derivatives and Their Biological Evaluation as eIF4A Inhibitors

Rocaglates are a family of natural products isolated from the genus Aglaia which possess a highly substituted cyclopenta[b]benzofuran skeleton and inhibit cap-dependent protein synthesis. Rocaglates are attractive compounds due to their potential for inhibiting tumor cell maintenance in vivo by specifically targeting eukaryotic initiation factor 4A (eIF4A) and interfering with recruitment of ribosomes to mRNA. In this paper, we describe an intercepted retro-Nazarov reaction utilizing intramolecular tosyl migration to generate a reactive oxyallyl cation on the rocaglate skeleton. Trapping of the oxyallyl cation with a diverse range of nucleophiles has been used to generate over 50 novel amidino-rocaglate (ADR) and amino-rocaglate derivatives. Subsequently, these derivatives were evaluated for their ability to inhibit cap-dependent protein synthesis where they were found to outperform previous lead compounds including the rocaglate hydroxamate CR-1-31-B.

Initial results from the New Horizons exploration of 2014 MU69, a small Kuiper Belt object

The Kuiper Belt is a distant region of the outer Solar System. On 1 January 2019, the New Horizons spacecraft flew close to (486958) 2014 MU₆₉, a cold classical Kuiper Belt object approximately 30 kilometers in diameter. Such objects have never been substantially heated by the Sun and are therefore well preserved since their formation. We describe initial results from these encounter observations. MU₆₉ is a bilobed contact binary with a flattened shape, discrete geological units, and noticeable albedo heterogeneity. However, there is little surface color or compositional heterogeneity. No evidence for satellites, rings or other dust structures, a gas coma, or solar wind interactions was detected. MU₆₉'s origin appears consistent with pebble cloud collapse followed by a low-velocity merger of its two lobes.

Discovery of Macrocyclic Inhibitors of Apurinic/Apyrimidinic Endonuclease 1

Apurinic/apyrimidinic endonuclease 1 (APE1) is an essential base excision repair enzyme that is upregulated in a number of cancers, contributes to resistance of tumors treated with DNA-alkylating or -oxidizing agents, and has recently been identified as an important therapeutic target. In this work, we identified hot spots for binding of small organic molecules experimentally in high resolution crystal structures of APE1 and computationally through the use of FTMAP analysis ( http://ftmap.bu.edu/ ). Guided by these hot spots, a library of drug-like macrocycles was docked and then screened for inhibition of APE1 endonuclease activity. In an iterative process, hot-spot-guided docking, characterization of inhibition of APE1 endonuclease, and cytotoxicity of cancer cells were used to design next generation macrocycles. To assess target selectivity in cells, selected macrocycles were analyzed for modulation of DNA damage. Taken together, our studies suggest that macrocycles represent a promising class of compounds for inhibition of APE1 in cancer cells.

Oxo-aglaiastatin-Mediated Inhibition of Translation Initiation

Translation is a highly regulated process that is perturbed in human cancers, often through activation of the PI3K/mTOR pathway which impacts directly on the ribosome recruitment phase of translation initiation. While significant research has focused on “drugging” components of the PI3K/mTOR network, efforts have also been directed towards inhibiting eukaryotic initiation factor (eIF) 4F-dependent translation. Small molecule inhibitors of this complex have been identified, characterized, and used to validate the rationale of targeting this step to curtail tumor cell growth and modulate chemotherapy response. One such class of compounds are the rocaglates, secondary metabolites from the plant genus Aglaia, which target the RNA helicase subunit of eIF4F, eIF4A. Here we explore the ability of synthetic derivatives of aglaiastatins and an aglaroxin derivative to target the translation process in vitro and in vivo and find the synthetic derivative oxo-aglaiastatin to possess such activity. Oxo-aglaiastatin inhibited translation in vitro and in vivo and synergized with doxorubicin, ABT-199 (a Bcl-2 antagonist), and dexamethasone when tested on hematological cancer cells. The biological activity of oxo-aglaiastatin was shown to be a consequence of inhibiting eIF4A1 activity.

Structural basis for species-selective targeting of Hsp90 in a pathogenic fungus

New strategies are needed to counter the escalating threat posed by drug-resistant fungi. The molecular chaperone Hsp90 affords a promising target because it supports survival, virulence and drug-resistance across diverse pathogens. Inhibitors of human Hsp90 under development as anticancer therapeutics, however, exert host toxicities that preclude their use as antifungals. Seeking a route to species-selectivity, we investigate the nucleotide-binding domain (NBD) of Hsp90 from the most common human fungal pathogen, Candida albicans. Here we report structures for this NBD alone, in complex with ADP or in complex with known Hsp90 inhibitors. Encouraged by the conformational flexibility revealed by these structures, we synthesize an inhibitor with >25-fold binding-selectivity for fungal Hsp90 NBD. Comparing co-crystals occupied by this probe vs. anticancer Hsp90 inhibitors revealed major, previously unreported conformational rearrangements. These insights and our probe's species-selectivity in culture support the feasibility of targeting Hsp90 as a promising antifungal strategy.

Chemical Synthesis Enables Structural Reengineering of Aglaroxin C Leading to Inhibition Bias for Hepatitis C Viral Infection

As a unique rocaglate (flavagline) natural product, aglaroxin C displays intriguing biological activity by inhibiting hepatitis C viral entry. To further elucidate structure-activity relationships and diversify the pyrimidinone scaffold, we report a concise synthesis of aglaroxin C utilizing a highly regioselective pyrimidinone condensation. We have prepared more than 40 aglaroxin C analogues utilizing various amidine condensation partners. Through biological evaluation of analogues, we have discovered two lead compounds, CMLD012043 and CMLD012044, which show preferential bias for the inhibition of hepatitis C viral entry vs translation inhibition. Overall, the study demonstrates the power of chemical synthesis to produce natural product variants with both target inhibition bias and improved therapeutic indexes.

Diastereodivergent Synthesis of Chiral Tetrahydropyrrolodiazepinediones via a One-Pot Intramolecular aza-Michael/Lactamization Sequence

A modular and diastereodivergent synthesis of tetrahydro-1 H-pyrrolo[1,2 d]diazepine-(2,5)-diones is presented. The tetrahydropyrrolodiazepinedione scaffold is obtained via a base-mediated three-step isomerization/tandem cyclization of amino acid-coupled homoallylic amino esters. Diastereoselectivity of the process is mediated by the interplay of a kinetic cyclization event and a propensity for thermodynamic epimerization at two labile chiral centers, giving rise to two distinct major diastereomers dependent on starting material stereochemistry and reaction conditions selected. Herein, we present a synthetic and computational study for this tandem process on a variety of amino ester substrates.

Sensitization of renal carcinoma cells to TRAIL-induced apoptosis by rocaglamide and analogs

Rocaglamide has been reported to sensitize several cell types to TRAIL-induced apoptosis. In recent years, advances in synthetic techniques have led to generation of novel rocaglamide analogs. However, these have not been extensively analyzed as TRAIL sensitizers, particularly in TRAIL-resistant renal cell carcinoma cells. Evaluation of rocaglamide and analogs identified 29 compounds that are able to sensitize TRAIL-resistant ACHN cells to TRAIL-induced, caspase-dependent apoptosis with sub-µM potency which correlated with their potency as protein synthesis inhibitors and with loss of cFLIP protein in the same cells. Rocaglamide alone induced cell cycle arrest, but not apoptosis. Rocaglates averaged 4–5-fold higher potency as TRAIL sensitizers than as protein synthesis inhibitors suggesting a potential window for maximizing TRAIL sensitization while minimizing effects of general protein synthesis inhibition. A wide range of other rocaglate effects (e.g. on JNK or RAF-MEK-ERK signaling, death receptor levels, ROS, ER stress, eIF4E phosphorylation) were assessed, but did not contribute to TRAIL sensitization. Other than a rapid loss of MCL-1, rocaglates had minimal effects on mitochondrial apoptotic pathway proteins. The identification of structurally diverse/mechanistically similar TRAIL sensitizing rocaglates provides insights into both rocaglate structure and function and potential further development for use in RCC-directed combination therapy.

Abstract 3903: Rocaglamide A and synthetic analogues sensitize resistant renal carcinoma cells to TRAIL-induced apoptosis and inhibit cell proliferation

Induction of cancer cell-specific apoptosis via activation of TRAIL (tumor necrosis factor-related apoptosis-inducing ligand) signaling has been an attractive goal for cancer therapeutics. However, many tumor cells develop resistance to TRAIL. Therefore, the search for enhancers of TRAIL-induced apoptosis has accelerated over the past several years. A high-throughput screening assay was developed that identified several natural product enhancers of TRAIL-induced apoptosis in TRAIL-resistant renal carcinoma cells. Among these natural products was the protein synthesis inhibitor, rocaglamide A, a cyclopenta[b]benzofuran secondary metabolite from the genus Aglaia, with potent antiproliferative and anti-inflammatory properties. Natural and synthetic rocaglates have been reported to have potent anticancer activities in vitro on various human cancer cell lines and in vivo in mouse models. The mechanism of action involved in the anticancer effects of rocaglamide A is generally thought to be inhibition of translation initiation. However, several other cancer-related cellular effects including cell cycle arrest have been reported in various cancer cell types. In this study, rocaglamide A and its synthetic analogs were assessed for their ability to enhance TRAIL-induced apoptosis, inhibit protein synthesis, and regulate cellular processes associated with TRAIL sensitization in TRAIL-resistant ACHN renal carcinoma cells. Rocaglate treatment enhanced TRAIL signaling resulting in caspase-dependent apoptotic cell death upon addition of TRAIL. Rocaglates also inhibited protein synthesis, which correlates with rapid loss of the antiapoptotic FLICE-inhibitory protein (cFLIP) and MCL-1, which are often overexpressed in TRAIL-resistant cancer cells. On average, the rocaglates were ~4-5-fold more potent than TRAIL sensitizers compared to their protein synthesis inhibitory potency. This difference suggests a possible therapeutic window for induction of TRAIL sensitization while minimizing general effects of protein synthesis inhibition. Rocaglamide treatment alone inhibited cell proliferation leading to cell cycle arrest at G2/M phase but not subsequent apoptosis. These studies suggest that the TRAIL-sensitizing activity of rocaglates and their growth-inhibitory effects as single agents are largely dependent on protein synthesis inhibition. The development of a large number of structurally diverse but mechanistically similar enhancers of TRAIL signaling with a wide range of potencies allows for further understanding of structure-activity relationships regarding both protein synthesis inhibition and TRAIL sensitization for this important family of compounds.

Funded (in part) by NCI Contract No. HHSN261200800001E.

Citation Format: Ancy D. Nalli, Lauren E. Brown, Cheryl L. Thomas, Thomas J. Sayers, John A. Porco, Curtis J. Henrich. Rocaglamide A and synthetic analogues sensitize resistant renal carcinoma cells to TRAIL-induced apoptosis and inhibit cell proliferation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3903.

Abstract 684: Inhibition of translation by aglaiastatins: Mechanism of action

Background: Secondary metabolites from plants of the Aglaia genus consist of several classes of compounds, including the cyclopenta[b]benzopyrans, benzo[b]oxepines and cyclopenta[b]benzofurans (rocaglates). The best characterized of these is silvestrol; a rocaglate, which has been shown to target eukaryotic initiation factor 4A (eIF4A), the RNA helicase subunit of the eukaryotic initiation factor 4F (eIF4F) complex. The formation of this complex is regulated by the PI3K/mTOR and Ras-MAPK pathways. Hence, being at the nexus of important oncogenic pathways, eIF4F represents an attractive target for cancer therapy. Silvestrol and its analogs have demonstrated potent activity in human tumor cell lines and xenograft models. Some of the most responsive mRNAs are those encoding oncogenic proteins such as Myc and Mcl-1. This places this group of compounds as promising therapeutic agents against Myc-driven cancers.

Purpose of the study: The purpose of this study is to characterize a sub-group of Aglaia secondary metabolites known as aglaiastatins, which are characterized by the presence of a pyrimidone subunit fused to the cyclopenta[b]benzofuran structure, resulting in a pentacyclic skeleton.

Method: Using in vitro and in vivo assays, we assessed the potency of representative aglaiastatins towards inhibition of protein synthesis and cytotoxicity of tumor cells.

Results: We showed that aglaiastatins induce a specific inhibition of cap-dependent translation by interfering with eIF4A's RNA binding activity, similar to rocaglates. This strong correlation in the mechanism of action was further demonstrated in an eIF4AF163L rocaglate-resistant cell line. Aglaiastatins also demonstrated single agent potency in vitro against a diverse panel of human lymphoma cell lines as well as primary patient samples. In vivo, the compound of interest was found to have a chemosensitization capability, by reversing chemoresistance to doxorubicin in a pre-clinical murine lymphoma model.

Conclusion: Our results indicate that the aglaiastatins also target eIF4A, similarly to rocaglates. Their activity against rocaglate-resistant cells indicates a high similarity in drug target binding pattern. Moreover, the targeting of cap-dependent translation through the RNA helicase allows for the potent activity of the drug against several lymphoma lines, regardless of their mutational landscape, thus providing a potential therapeutic opportunity against difficult-to-treat hematological malignancies.

Citation Format: Rayelle Itoua Maïga, Regina Cencic, Jennifer Chu, Lauren E. Brown, Daniel Dirck Waller, Mònica Gómez Palou, Michael Sebag, John A. Porco, Jerry Pelletier. Inhibition of translation by aglaiastatins: Mechanism of action [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 684.

Inhibiting the oncogenic translation program is an effective therapeutic strategy in multiple myeloma

Multiple myeloma (MM) is a frequently incurable hematological cancer in which overactivity of MYC plays a central role, notably through up-regulation of ribosome biogenesis and translation. To better understand the oncogenic program driven by MYC and investigate its potential as a therapeutic target, we screened a chemically diverse small-molecule library for anti-MM activity. The most potent hits identified were rocaglate scaffold inhibitors of translation initiation. Expression profiling of MM cells revealed reversion of the oncogenic MYC-driven transcriptional program by CMLD010509, the most promising rocaglate. Proteome-wide reversion correlated with selective depletion of short-lived proteins that are key to MM growth and survival, most notably MYC, MDM2, CCND1, MAF, and MCL-1. The efficacy of CMLD010509 in mouse models of MM confirmed the therapeutic relevance of these findings in vivo and supports the feasibility of targeting the oncogenic MYC-driven translation program in MM with rocaglates.

Live Attenuated Influenza Vaccines engineered to express the nucleoprotein of a recent isolate stimulate human influenza CD8+ T cells more relevant to current infections

Live attenuated influenza vaccines (LAIV) induce CD8⁺ T lymphocyte responses that play an important role in killing virus-infected cells. Despite the relative conservation of internal influenza A proteins, the epitopes recognized by T cells can undergo drift under immune pressure. The internal proteins of Russian LAIVs are derived from the master donor virus A/Leningrad/134/17/57 (Len/17) isolated 60 years ago and as such, some CD8⁺ T cell epitopes may vary between the vaccine and circulating wild-type strains. To partially overcome this issue, the nucleoprotein (NP) gene of wild-type virus can be incorporated into LAIV reassortant virus, along with the HA and NA genes. The present study compares the human CD8+ T cell memory responses to H3N2 LAIVs with the Len/17 or the wild-type NP using an in vitro model.

Total Syntheses of the Isomeric Aglain Natural Products Foveoglin A and Perviridisin B: Selective Excited-State Intramolecular Proton-Transfer Photocycloaddition

Selective excited-state intramolecular proton-transfer (ESIPT) photocycloaddition of 3-hydroxyflavones with trans, trans-1,4-diphenyl-1,3-butadiene is described. Using this methodology, total syntheses of the natural products (±)-foveoglin A and (±)-perviridisin B were accomplished. Enantioselective ESIPT photocycloaddition using TADDOLs as chiral hydrogen-bonding additives provided access to (+)-foveoglin A. Mechanistic studies have revealed the possibility for a photoinduced electron-transfer (PET) pathway.

Dihydropyrimidine-Thiones and Clioquinol Synergize To Target β-Amyloid Cellular Pathologies through a Metal-Dependent Mechanism

The lack of therapies for neurodegenerative diseases arises from our incomplete understanding of their underlying cellular toxicities and the limited number of predictive model systems. It is critical that we develop approaches to identify novel targets and lead compounds. Here, a phenotypic screen of yeast proteinopathy models identified dihydropyrimidine-thiones (DHPM-thiones) that selectively rescued the toxicity caused by β-amyloid (Aβ), the peptide implicated in Alzheimer's disease. Rescue of Aβ toxicity by DHPM-thiones occurred through a metal-dependent mechanism of action. The bioactivity was distinct, however, from that of the 8-hydroxyquinoline clioquinol (CQ). These structurally dissimilar compounds strongly synergized at concentrations otherwise not competent to reduce toxicity. Cotreatment ameliorated Aβ toxicity by reducing Aβ levels and restoring functional vesicle trafficking. Notably, these low doses significantly reduced deleterious off-target effects caused by CQ on mitochondria at higher concentrations. Both single and combinatorial treatments also reduced death of neurons expressing Aβ in a nematode, indicating that DHPM-thiones target a conserved protective mechanism. Furthermore, this conserved activity suggests that expression of the Aβ peptide causes similar cellular pathologies from yeast to neurons. Our identification of a new cytoprotective scaffold that requires metal-binding underscores the critical role of metal phenomenology in mediating Aβ toxicity. Additionally, our findings demonstrate the valuable potential of synergistic compounds to enhance on-target activities, while mitigating deleterious off-target effects. The identification and prosecution of synergistic compounds could prove useful for developing AD therapeutics where combination therapies may be required to antagonize diverse pathologies.

Toxicity reference values for methylmercury effects on avian reproduction: Critical review and analysis

Effects of mercury (Hg) on birds have been studied extensively and with increasing frequency in recent years. The authors conducted a comprehensive review of methylmercury (MeHg) effects on bird reproduction, evaluating laboratory and field studies in which observed effects could be attributed primarily to Hg. The review focuses on exposures via diet and maternal transfer in which observed effects (or lack thereof) were reported relative to Hg concentrations in diet, eggs, or adult blood. Applicable data were identified for 23 species. From this data set, the authors identified ranges of toxicity reference values suitable for risk-assessment applications. Typical ranges of Hg effect thresholds are approximately 0.2 mg/kg to >1.4 mg/kg in diet, 0.05 mg/kg/d to 0.5 mg/kg/d on a dose basis, 0.6 mg/kg to 2.7 mg/kg in eggs, and 2.1 mg/kg to >6.7 mg/kg in parental blood (all concentrations on a wet wt basis). For Hg in avian blood, the review represents the first broad compilation of relevant toxicity data. For dietary exposures, the current data support TRVs that are greater than older, commonly used TRVs. The older diet-based TRVs incorporate conservative assumptions and uncertainty factors that are no longer justified, although they generally were appropriate when originally derived, because of past data limitations. The egg-based TRVs identified from the review are more similar to other previously derived TRVs but have been updated to incorporate new information from recent studies. While important research needs remain, a key recommendation is that species not yet tested for MeHg toxicity should be evaluated using toxicity data from tested species with similar body weights. Environ Toxicol Chem 2017;36:294-319. © 2016 SETAC.

Torque-angle-velocity Relationships and Muscle Performance of Professional and Youth Soccer Players

Soccer matches consist of a variety of different activities, including repeated sprints. Time to attain velocity (TTAV), load range (LR) and the torque-angle-velocity relationship (TAV_3D) represent an important measurement of muscle performance, however there are few related studies. The aim of this study was to compare these outcomes between soccer players of different age category. 17 professional (PRO) and 17 under-17 (U17) soccer players were assessed for concentric knee flexion/extension at 60, 120 and 300°/s. For the extensor muscles, differences were found in favor of the U17 group for TTAV and LR outcomes at 120°/s, however, the PRO group maintained higher torques in both movement directions in comparison to the U17 in TAV_3D evaluation. These results suggest that muscle performance of the PRO group is more efficient than the U17 group.

Asymmetric Dearomatization/Cyclization Enables Access to Polycyclic Chemotypes

Enantioenriched, polycyclic compounds were obtained from a simple acylphloroglucinol scaffold. Highly enantioselective dearomatization was accomplished using a Trost ligand-palladium(0) complex. A computational DFT model was developed to rationalize observed enantioselectivities and revealed a key reactant-ligand hydrogen bonding interaction. Dearomatized products were used in visible light-mediated photocycloadditions and oxidative free radical cyclizations to obtain novel polycyclic chemotypes including tricyclo[4.3.1.0^1,4]decan-10-ones, bicyclo[3.2.1]octan-8-ones and highly-substituted cycloheptanones.

Pluto's interaction with its space environment: Solar wind, energetic particles, and dust

The New Horizons spacecraft carried three instruments that measured the space environment near Pluto as it flew by on 14 July 2015. The Solar Wind Around Pluto (SWAP) instrument revealed an interaction region confined sunward of Pluto to within about 6 Pluto radii. The region's surprisingly small size is consistent with a reduced atmospheric escape rate, as well as a particularly high solar wind flux. Observations from the Pluto Energetic Particle Spectrometer Science Investigation (PEPSSI) instrument suggest that ions are accelerated and/or deflected around Pluto. In the wake of the interaction region, PEPSSI observed suprathermal particle fluxes equal to about 1/10 of the flux in the interplanetary medium and increasing with distance downstream. The Venetia Burney Student Dust Counter, which measures grains with radii larger than 1.4 micrometers, detected one candidate impact in ±5 days around New Horizons' closest approach, indicating an upper limit of <4.6 kilometers(-3) for the dust density in the Pluto system.

Critical perspectives on mercury toxicity reference values for protection of fish

Environmental management decisions at mercury-contaminated sediment sites are predicated on the understanding of risks to various receptors, including fish. Toxicity reference values (TRVs) for interpreting risks to fish have been developed to assess mercury concentrations in fish or fish prey. These TRVs were systematically evaluated based on several lines of evidence. First, their conceptual basis and specific derivation were evaluated, including a close review of underlying toxicity studies. Second, case studies were reviewed to investigate whether TRVs are predictive of effects on fish populations in the field. Third, TRVs were compared with available information regarding preindustrial and present-day background concentrations of mercury in fish. The findings show that existing TRVs are highly uncertain, because they were developed using limited data from studies not designed for TRV derivation. Although field studies also entail uncertainty, several case studies indicate no evidence of adverse effects despite mercury exposures that exceed the available TRVs. Some TRVs also fall within the range of background mercury concentrations in predatory or prey fish. Lack of information on the selenium status of mercury-exposed fish is a critical confounding factor, and the form of methylmercury used in toxicity testing may also contribute to differences between TRV-based predictions and field observations of mercury effects on fish. On balance, the available information indicates that several of the TRVs reviewed are lower than necessary to protect fish populations. The 20% effect concentration from a previously published dose-response analysis appears closer to an effect threshold, based on available laboratory data. Additional research is needed to provide a stronger basis to establish dose-response relationships for mercury effects on fish.

Impact of anti-inflammatories, beta-blockers and antibiotics on leaf litter breakdown in freshwaters

Pharmaceuticals are now recognised as important pollutants in freshwater systems, but a shortcoming of effects studies is that they have focused on structural endpoints and impacts on ecosystem functioning are poorly understood. The decomposition of organic matter is an important functional process in aquatic systems, and it is known that this can be impacted by the presence of pollutants. Previous studies on leaf litter breakdown have only considered the effects of antibiotics and not other groups of drugs though. The current study investigated the effects of anti-inflammatories, a beta-blocker and an antibiotic on microbially mediated breakdown of leaf litter in the laboratory; colonisation of leaf packs by benthic macroinvertebrates when placed in a stream; and shredding of leaf litter by these organisms. Furthermore, the effects of single compounds relative to their mixture were assessed. It was found that exposure of leaf litter to the study compounds did not influence its breakdown by microbes in the laboratory or macroinvertebrates in a stream. Exposure of leaf litter to pharmaceuticals also had no effect on its colonisation by macroinvertebrates in this study. Many unknowns remain, however, and further studies of the effects of pharmaceuticals on structural and functional endpoints are needed to aid aquatic conservation.

The effect of sediment mixing on mercury dynamics in two intertidal mudflats at Great Bay Estuary, New Hampshire, USA

Estuarine sediments store particulate contaminants including mercury (Hg). We studied Hg sediment dynamics in two intertidal mudflats at Great Bay estuary, NH, over multiple years. Sediments at both mudflats were physically mixed down to ~10 cm, as determined by ⁷Be measurements, albeit via different mechanisms. Portsmouth mudflat (PT) sediments were subject to bioturbation by infaunal organisms and Squamscott mudflat (SQ) sediments were subject to erosion and redeposition. The presence of higher concentrations of fresh Fe(III) hydroxide at PT suggested bioirrigation by the polychaetes (Nereis virens). At depths where infaunal bioirrigation was observed, pore-water inorganic Hg (Hg_i) and methylmercury (MeHg) were lower potentially due to their interaction with Fe(III) hydroxide. Methylmercury concentrations increased immediately below this zone in some samples, suggesting that the observed increase in material flux in bioirrigated sediments may initiate from lower depths. Pore water in sediment at PT also had higher fractions of more protein-like and labile DOC than those at SQ that can lead to increased MeHg production in PT, especially at depths where Hg_i is not removed from solution by Fe(III) hydroxide. Where sediment erosion and redeposition were observed at SQ, Hg species distribution was extended deeper into the sediment column. Moreover, methyl coenzyme M reductase (MCR) and mercury reductase (mer-A) genes were higher at SQ than PT suggesting differences in conditions for Hg cycling. Results showed that the near-surface region of high MeHg concentrations commonly observed in unmixed sediments does not exist in physically mixed sediments that are common in many estuarine environments.

A Novel Class of Small Molecule Compounds that Inhibit Hepatitis C Virus Infection by Targeting the Prohibitin-CRaf Pathway

Identification of novel drug targets and affordable therapeutic agents remains a high priority in the fight against chronic hepatitis C virus (HCV) infection. Here, we report that the cellular proteins prohibitin 1 (PHB1) and 2 (PHB2) are pan-genotypic HCV entry factors functioning at a post-binding step. While predominantly found in mitochondria, PHBs localize to the plasma membrane of hepatocytes through their transmembrane domains and interact with both EGFR and CRaf. Targeting PHB by rocaglamide (Roc-A), a natural product that binds PHB1 and 2, reduced cell surface PHB1 and 2, disrupted PHB-CRaf interaction, and inhibited HCV entry at low nanomolar concentrations. A structure-activity analysis of 32 synthetic Roc-A analogs indicated that the chiral, racemic version of aglaroxin C, a natural product biosynthetically related to Roc-A, displayed improved potency and therapeutic index against HCV infection. This study reveals a new class of HCV entry inhibitors that target the PHB1/2-CRaf pathway.

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Cellular proteins prohibitins 1 and 2 are essential HCV entry factors that function at a post-binding step.

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The natural compound Roc-A potently blocks HCV infection by disrupting prohibitins-CRaf interaction

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The Roc-A derivative, aglaroxin C, displays improved potency and therapeutic index towards HCV infection

Current FDA-approved HCV drugs all target viral proteins. We now demonstrate that a group of small molecules, the rocaglates, potently block HCV entry at low nanomolar concentrations. Roc-A inhibits HCV entry by disrupting the important interaction between two pan-genomic HCV entry factors, PHB1 and 2, and the signaling molecule CRaf. Overall, Roc-A and related rocaglates represent a new class of compounds that hold significant therapeutic promise in treating HCV infection.