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Our ongoing efforts to explore the chemical space associated with marine cyanobacteria from coral reefs of Guam has yielded two new members of the anaenamide family of natural products, anaenamides C (3) and D (4). These compounds were isolated from a novel Hormoscilla sp. (VPG16-58). Our phylogenetic profiling (16S rDNA) of this cyanobacterium indicated that VPG16-58 is taxonomically distinct from the previously reported producer of the anaephenes, VPG16-59 (Hormoscilla sp.), and other previously documented species of the genus Hormoscilla. The planar structures of 3 and 4 were determined via spectroscopic methods, and absolute configurations of the α-hydroxy acids were assigned by enantioselective HPLC analysis. To address the requirement for sufficient material for testing, we first adapted our published linear synthetic approach for 1 and 2 to generate anaenoic acid (7) that served as a point for diversification, providing the primary amides 3 and 4 from synthetic intermediates 5 and 6, respectively. The compounds were then tested for effects on HCT116 colon cancer cell viability and in an ARE-luciferase reporter gene assay for Nrf2 modulation using HEK293 human embryonic kidney cells. Our findings indicate that, in contrast to cytotoxic methyl esters 1 and 2, the primary amides 3 and 4 activate the Nrf2 pathway at noncytotoxic concentrations. Overall, our data suggest that the anaenamide scaffold is tunable to produce differential biological outcomes.

Pathogenic bacteria demonstrate incredible abilities to evade conventional antibiotics through the development of resistance and formation of dormant, surface-attached biofilms. Therefore, agents that target and eradicate planktonic and biofilm bacteria are of significant interest. We explored a new series of halogenated phenazines (HP) through the use of N-aryl-2-nitrosoaniline synthetic intermediates that enabled functionalization of the 3-position of this scaffold. Several HPs demonstrated potent antibacterial and biofilm-killing activities (e.g., HP 29, against methicillin-resistant Staphylococcus aureus: MIC = 0.075 μM; MBEC = 2.35 μM), and transcriptional analysis revealed that HPs 3, 28, and 29 induce rapid iron starvation in MRSA biofilms. Several HPs demonstrated excellent activities against Mycobacterium tuberculosis (HP 34, MIC = 0.80 μM against CDC1551). This work established new SAR insights, and HP 29 demonstrated efficacy in dorsal wound infection models in mice. Encouraged by these findings, we believe that HPs could lead to significant advances in the treatment of challenging infections.

Irregular nuclear shapes are a hallmark of human cancers. Recent studies suggest that alterations to chromatin regulators may cause irregular nuclear morphologies. Here we screened an epigenetic small molecule library consisting of 145 compounds against chromatin regulators for their ability to revert abnormal nuclear shapes that were induced by gene knockdown in noncancerous MCF10A human mammary breast epithelial cells. We leveraged a previously validated quantitative Fourier approach to quantify the elliptical Fourier coefficient (EFC ratio) as a measure of nuclear irregularities, which allowed us to perform rigorous statistical analyses of screening data. Top hit compounds fell into three major mode of action categories, targeting three separate epigenetic modulation routes: 1) histone deacetylase inhibitors, 2) bromodomain and extraterminal domain protein inhibitors, and 3) methyl-transferase inhibitors. Some of the top hit compounds were also efficacious in reverting nuclear irregularities in MDA-MB-231 triple negative breast cancer cells and in PANC-1 pancreatic cancer cells in a cell-type-dependent manner. Regularization of nuclear shapes was compound-specific, cell-type specific, and dependent on the specific molecular perturbation that induced nuclear irregularities. Our approach of targeting nuclear abnormalities may be potentially useful in screening new types of cancer therapies targeted toward chromatin structure.

Piperine, a natural product derived from peppercorns, has a variety of biological activities that make it an attractive lead compound for medicinal chemistry. However, piperine has some problematic physicochemical properties including poor aqueous solubility and a susceptibility to UV-induced degradation. In this work, we designed an analog of piperine in which the central conjugated hydrocarbon chain is replaced with a vicinal difluoroalkane moiety. We show that this fluorinated analog of piperine has superior physicochemical properties, and it also has higher potency and selectivity towards one particular drug target, acetylcholinesterase. This work highlights the potential usefulness of the threo-difluoroalkane motif as a surrogate for E-alkenes in medicinal chemistry.

Some fungal epithiodiketopiperazine alkaloids display α,β-polysulfide bridges alongside diverse structural variations. However, the logic of their chemical diversity has rarely been explored. Here, we report the identification of three new (2, 3, 8) and five known (1, 4–7) epithiodiketopiperazines of this subtype from a marine-derived Penicillium sp. The structure elucidation was supported by multiple spectroscopic analyses. Importantly, we observed multiple nonenzymatic interconversions of these analogues in aqueous solutions and organic solvents. Furthermore, the same biosynthetic origin of these compounds was supported by one mined gene cluster. The dominant analogue (1) demonstrated selective cytotoxicity to androgen-sensitive prostate cancer cells and HIF-depleted colorectal cells and mild antiaging activities, linking the bioactivity to oxidative stress. These results provide crucial insight into the formation of fungal epithiodiketopiperazines through chemical interconversions.

Largazole is a potent class I selective histone deacetylase inhibitor prodrug with anticancer activity against solid tumors in preclinical models. Largazole possesses in vitro activity against glioblastoma multiforme (GBM) cells and sufficiently crosses the blood-brain barrier based on measurement of the active species, largazole thiol, to achieve therapeutically relevant concentrations in the mouse brain. The effective dose resulted in pronounced functional responses on the transcript level based on RNA sequencing and quantitative polymerase chain reaction after reverse transcription (RT-qPCR), revealing desirable expression changes of genes related to neuroprotection, including Bdnf and Pax6 upregulation, extending the applicability of largazole to the treatment of brain cancer and neurodegenerative disorders. The largazole-induced modulation of Pax6 unifies both activities, since Pax6 expression suppresses GBM proliferation and invasion and inversely correlates with GBM tumor grade, while it is also implicated in neurogenesis, neuronal plasticity, and cognitive ability. Our results suggest that largazole could be repurposed for diseases of the brain.

Chemical investigation of a benthic marine cyanobacterium yielded the anticancer agent dolastatin 15, originally isolated from a mollusk. Dolastatin 15 is a microtubule-destabilizing agent with analogues undergoing clinical evaluation. Profiling against a panel of isogenic HCT116 colorectal cancer cells showed remarkable differential cytotoxicity against the parental cells over isogenic cells lacking HIF or other key players in the pathway, including oncogenic KRAS and VEGF. Dolastatin 15 displayed an antivascularization effect in human endothelial cells and in zebrafish vhl mutants with activated Hif, thus signifying its clinical potential as a treatment for solid tumors with an angiogenic component. Global transcriptome analysis with RNA sequencing suggested that dolastatin 15 could affect other major cancer pathways that might not directly involve tubulin or HIF. The identification of the true producer of a clinically relevant agent is important for sustainable supply, as is understanding the biosynthesis, and future genetic manipulation of the biosynthetic gene cluster for analogue production.

[Image: see text] Due to the potency and selectivity of lyngbyastatin 7 in inhibiting neutrophil elastase, a serine protease involved in numerous diseases, this cyclodepsipeptide was considered as a promising lead and subjected to further developmental studies. Lyngbyastatin 7 displayed a favorable serum and microsomal stability profile. The large-scale synthesis of key building blocks was performed on gram scale with improved yields and simplified purification procedures. To tailor the complex structure, define the minimal pharmacophore, and modulate the physicochemical properties of the lead scaffold, the first pilot library of analogues was designed and synthesized for structure–activity relationship studies. We uncovered the essential role of the side chain, indicating that the minimal structural requirements for elastase inhibition extended beyond the 3-amino-6-hydroxy-2-piperidone (Ahp) and 2-aminobutenoic acid (Abu) moieties conventionally known to convey antiprotease activity and elastase selectivity, respectively. Our studies will facilitate the design and development of this class of elastase inhibitors.

Marine cyanobacteria (blue-green algae) have been shown to possess an enormous capacity to produce structurally diverse natural products that exhibit a broad spectrum of potent biological activities, including cytotoxic, antifungal, antiparasitic, antiviral, and antibacterial activities. Using mass-spectrometry-guided fractionation together with molecular networking, cyanobacterial field collections from American Samoa and Palmyra Atoll yielded three new cyclic peptides, tutuilamides A-C. Their structures were established by spectroscopic techniques including 1D and 2D NMR, HR-MS, and chemical derivatization. Structure elucidation was facilitated by employing advanced NMR techniques including nonuniform sampling in combination with the 1,1-ADEQUATE experiment. These cyclic peptides are characterized by the presence of several unusual residues including 3-amino-6-hydroxy-2-piperidone and 2-amino-2-butenoic acid, together with a novel vinyl chloride-containing residue. Tutuilamides A-C show potent elastase inhibitory activity together with moderate potency in H-460 lung cancer cell cytotoxicity assays. The binding mode to elastase was analyzed by X-ray crystallography revealing a reversible binding mode similar to the natural product lyngbyastatin 7. The presence of an additional hydrogen bond with the amino acid backbone of the flexible side chain of tutuilamide A, compared to lyngbyastatin 7, facilitates its stabilization in the elastase binding pocket and possibly explains its enhanced inhibitory potency.

A new series of pyrimidine-5-carbonitrile derivatives has been designed as ATP mimicking tyrosine kinase inhibitors of the epidermal growth factor receptor (EGFR). These compounds were synthesized and evaluated for their in vitro cytotoxic activities against a panel of four human tumor cell lines, namely colorectal carcinoma (HCT-116), hepatocellular carcinoma (HepG-2), breast cancer (MCF-7), and non-small cell lung cancer cells (A549). Five of the synthesized compounds, 11a, 11b, 12b, 15b and 16a, were found to exhibit moderate antiproliferative activity against the tested cell lines and were more active than the EGFR inhibitor erlotinib. In particular, compound 11b showed 4.5- to 8.4-fold erlotinib activity against HCT-116, HepG-2, MCF-7, and A549 cells with IC50 values of 3.37, 3.04, 4.14, and 2.4 μM respectively. Moreover, the most cytotoxic compounds that showed promising IC50 values against the four cancer cell lines were subjected to further investigation for their kinase inhibitory activities against EGFRWT and EGFRT790M using homogeneous time resolved fluorescence (HTRF) assay. Compound 11b was also found to be the most active compound against both EGFRWT and mutant EGFRT790M, exhibiting IC50 values of 0.09 and 4.03 μM, respectively. The cell cycle and apoptosis analyses revealed that compound 11b can arrest the cell cycle at the G2/M phase and induce significant apoptotic effects in HCT-116, HepG-2, and MCF-7 cells. Additionally, compound 11b upregulated the level of caspase-3 by 6.5 fold in HepG-2 when compared with the control. Finally, molecular docking studies were carried out to examine the binding mode of the synthesized compounds against the proposed targets; EGFRWT and EGFRT790M. Additional in silico ADMET studies were performed to explore drug-likeness properties.

Covering: up to April 2020 Proteases are involved in the regulation of many physiological processes. Their overexpression and dysregulated activity are linked to diseases such as hypertension, diabetes, viral infections, blood clotting disorders, respiratory diseases, and cancer. Therefore, they represent an important class of therapeutic targets. Several protease inhibitors have reached the market and >60% of them are directly related to natural products, even when excluding synthetic natural product mimics. Historically, natural products have been a valuable and validated source of therapeutic agents, as over half of the marketed drugs across targets and diseases are inspired by natural product structures. In the past two decades the number of new protease inhibitors discovered from nature has sharply increased. Additionally, the availability of 3D structural information for proteases has permitted structure-based design and accelerated the synthesis of optimized lead structures with improved potency and selectivity profiles, resulting in some of the most-potent-in-class inhibitors. These discoveries were oftentimes maximized by in-depth biological assessments of lead inhibitors, linking them to a relevant disease state. This review will discuss some of the current and emerging drug targets and their involvement in various disease processes, highlighting selected success stories behind several FDA-approved protease inhibitors that have natural products scaffolds as well as recent selected pharmacologically well-characterized inhibitors derived from marine or terrestrial sources.

Ocular angiogenic diseases, characterized by abnormal blood vessel formation in the eye, are the leading cause of blindness. Although Anti-VEGF therapy is the first-line treatment in the market, a substantial number of patients are refractory to it or may develop resistance over time. As uncontrolled proliferation of vascular endothelial cells is one of the characteristic features of pathological neovascularization, we aimed to investigate the role of the class I histone deacetylase (HDAC) inhibitor Largazole, a cyclodepsipeptide from a marine cyanobacterium, in ocular angiogenesis. Our study showed that Largazole strongly inhibits retinal vascular endothelial cell viability, proliferation, and the ability to form tube-like structures. Largazole strongly inhibits the vessel outgrowth from choroidal explants in choroid sprouting assay while it does not affect the quiescent choroidal vasculature. Largazole also inhibits vessel outgrowth from metatarsal bones in metatarsal sprouting assay without affecting pericytes coverage. We further demonstrated a cooperative effect between Largazole and an approved anti-VEGF drug, Alflibercept. Mechanistically, Largazole strongly inhibits the expression of VEGFR2 and leads to an increased expression of cell cycle inhibitor, p21. Taken together, our study provides compelling evidence on the anti-angiogenic role of Largazole that exerts its function through mediating different signaling pathways. National Medical Research Council (NMRC) Published version This research was funded by the Duke-NUS Start-Up Grant to X.W., the Singapore National Medical Research Council DYNAMO NMRC/OFLCG/001/2017 and TAPP NMRC/OFLCG/004/2018 to X.W., and the Debbie and Sylvia DeSantis professorship to H.L.

TheNatural Product Reportsthemed collection on targeting and extending the eukaryotic druggable genome with natural products is introduced by the Guest Editors, Hendrik Luesch and John B. MacMillan.

CXCR7 plays an emerging role in several physiological processes. A linear peptide, amantamide (1), was isolated from marine cyanobacteria, and the structure was determined by NMR and mass spectrometry. The total synthesis was achieved by solid-phase method. After screening two biological target libraries, 1 was identified as a selective CXCR7 agonist. The selective activation of CXCR7 by 1 could provide the basis for developing CXCR7-targeted therapeutics and deciphering the role of CXCR7 in different diseases.

Three related new alkylphenols, termed anaephenes A-C (1-3), containing different side chains, were isolated from an undescribed filamentous cyanobacterium (VPG 16-59) collected in Guam. Our 16S rDNA sequencing efforts indicated that VPG 16-59 is a member of the marine genus Hormoscilla (Oscillatoriales). The structures of anaephenes A-C (1-3) were elucidated by spectroscopic methods, and compounds assayed for growth inhibitory activity against prokaryotic and eukaryotic cell lines. Anaephene B (2), possessing a terminal alkyne, displayed moderate activity against Bacillus cereus and Staphylococcus aureus with MIC values of 6.1 μg/mL. While 1 and 3 showed no pronounced activity in these assays, their structural features highlight the unusual biosynthetic capacity of this cyanobacterium and warrant further study.

Pathogenic bacteria demonstrate incredible abilities to evade conventional antibiotics through the development of resistance and formation of dormant, surface-attached biofilms. Therefore, agents that target and eradicate planktonic and biofilm bacteria are of significant interest. We explored a new series of halogenated phenazines (HP) through the use of N-aryl-2-nitrosoaniline synthetic intermediates that enabled functionalization of the 3-position of this scaffold. Several HPs demonstrated potent antibacterial and biofilm-killing activities (e.g., HP 29, against methicillin-resistant Staphylococcus aureus: MIC = 0.075 μM; MBEC = 2.35 μM), and transcriptional analysis revealed that HPs 3, 28, and 29 induce rapid iron starvation in MRSA biofilms. Several HPs demonstrated excellent activities against Mycobacterium tuberculosis (HP 34, MIC = 0.80 μM against CDC1551). This work established new SAR insights, and HP 29 demonstrated efficacy in dorsal wound infection models in mice. Encouraged by these findings, we believe that HPs could lead to significant advances in the treatment of challenging infections.

Amantelide A, a polyhydroxylated macrolide isolated from a marine cyanobacterium, displays broad-spectrum activity against mammalian cells, bacterial pathogens, and marine fungi. We conducted comprehensive mechanistic studies to identify the molecular targets and pathways affected by amantelide A. Our investigations relied on chemical structure similarities with compounds of known mechanisms, yeast knockout mutants, yeast chemogenomic profiling, and direct biochemical and biophysical methods. We established that amantelide A exerts its antifungal action by binding to ergosterol-containing membranes followed by pore formation and cell death, a mechanism partially shared with polyene antifungals. Binding assays demonstrated that amantelide A also binds to membranes containing epicholesterol or mammalian cholesterol, thus suggesting that the cytotoxicity to mammalian cells might be due to its affinity to cholesterol-containing membranes. However, membrane interactions were not completely dependent on sterols. Yeast chemogenomic profiling suggested additional direct or indirect effects on actin. Accordingly, we performed actin polymerization assays, which suggested that amantelide A also promotes actin polymerization in cell-free systems. However, the C-33 acetoxy derivative amantelide B showed a similar effect on actin dynamics in vitro but no significant activity against yeast. Overall, these studies suggest that the membrane effects are the most functionally relevant for amantelide A mechanism of action.

New cyanobacteria-derived bifunctional analogues of doscadenamide A, a LasR-dependent quorum sensing (QS) activator in Pseudomonas aeruginosa, characterized by dual acylation of the pyrrolinone core structure and the pendant side chain primary amine to form an imide/amide hybrid are reported. The identities of doscadenamides B-J were confirmed through total synthesis and a strategic focused library with different acylation and unsaturation patterns was created. Key molecular interactions for binding with LasR and a functional response through mutation studies coupled with molecular docking were identified. The structure-activity relationships (SARs) were probed in various Gram-negative bacteria, including P. aeruginosa and Vibrio harveyi, indicating that the pyrrolinone-N acyl chain is critical for full agonist activity, while the other acyl chain is dispensable or can result in antagonist activity, depending on the bacterial system. Since homoserine lactone (HSL) quorum sensing activators have been shown to act in synergy with TRAIL to induce apoptosis in cancer cells, selected doscadenamides were tested in orthogonal eukaryotic screening systems. The most potent QS agonists, doscadenamides S10-S12, along with doscadenamides F and S4 with partial or complete saturation of the acyl side chains, exhibited the most pronounced synergistic effects with TRAIL in triple negative MDA-MB-231 breast cancer cells. The overall correlation of the SAR with respect to prokaryotic and eukaryotic targets may hint at coevolutionary processes and intriguing host-bacteria relationships. The doscadenamide scaffold represents a non-HSL template for combination therapy with TRAIL pathway stimulators.

Described herein is a function-oriented synthesis route and biological evaluation of pseudoguaianolide analogues. The 10-step synthetic route developed retains the topological complexity of the natural product, installs functional handles for late-stage diversification, and forges the key bioactive Michael acceptors early in the synthesis. The analogues were found to be low-micromolar Nrf2 activators and micromolar NF-κB inhibitors and dependent on the local environment of the Michael acceptor moieties.

35 p.-5 fig.-1 tab., Tubulin-targeted chemotherapy has proven to be a successful and wide spectrum strategy against solid and liquid malignancies. Therefore, new ways to modulate this essential protein could lead to new antitumoral pharmacological approaches. Currently known tubulin agents bind to six distinct sites at α/β-tubulin either promoting microtubule stabilization or depolymerization. We have discovered a seventh binding site at the tubulin intradimer interface where a novel microtubule-destabilizing cyclodepsipeptide, termed gatorbulin-1 (GB1), binds. GB1 has a unique chemotype produced by a marine cyanobacterium. We have elucidated this dual, chemical and mechanistic, novelty through multidimensional characterization, starting with bioactivity-guided natural product isolation and multinuclei NMR-based structure determination, revealing the modified pentapeptide with a functionally critical hydroxamate group; and validation by total synthesis. We have investigated the pharmacology using isogenic cancer cell screening, cellular profiling, and complementary phenotypic assays, and unveiled the underlying molecular mechanism by in vitro biochemical studies and high-resolution structural determination of the α/β-tubulin−GB1 complex., This research was supported by the NIH, National Cancer Institute Grants R01CA172310 (to H.L.) and R50CA211487 (to R.R.) and National Institute of General Medical Sciences Grant P41GM086210 (to H.L. and V.J.P.), Commercialization Fund Award from University of Florida (UF) Innovate (UF Office of Technology Licensing), and Debbie and Sylvia DeSantis Chair professorship (H.L.). The biochemical and the crystal structure work was supported by grants Ministerio de Ciencia e Innovación PID2019-10454RB-I00/AEI/10.13039/501100011033, Fondo de Investigaciones Sanitarias and COV20/01007E Proyecto Intramural Especial 201920E111 from Consejo Superior de Investigaciones Científicas (to J.F.D.) and European Union H2020-MSCA-ITN-2019 860070 TUBINTRAIN grant (to J.F.D. and A.E.P.).

Cyanobacteria produce a plethora of compounds with unique chemical structures and diverse biological activities. Importantly, the increasing availability of cyanobacterial genome sequences and the rapid development of bioinformatics tools have unraveled the tremendous potential of cyanobacteria in producing new natural products. However, the discovery of these compounds based on cyanobacterial genomes has progressed slowly as the majority of their corresponding biosynthetic gene clusters (BGCs) are silent. In addition, cyanobacterial strains are often slow-growing, difficult for genetic engineering, or cannot be cultivated yet, limiting the use of host genetic engineering approaches for discovery. On the other hand, genetically tractable hosts such as Escherichia coli, Actinobacteria, and yeast have been developed for the heterologous expression of cyanobacterial BGCs. More recently, there have been increased interests in developing model cyanobacterial strains as heterologous production platforms. Herein, we present recent advances in the heterologous production of cyanobacterial compounds in both cyanobacterial and noncyanobacterial hosts. Emerging strategies for BGC assembly, host engineering, and optimization of BGC expression are included for fostering the broader applications of synthetic biology tools in the discovery of new cyanobacterial natural products.

A new series of pyrimidine-5-carbonitrile derivatives has been designed as ATP mimicking tyrosine kinase inhibitors of the epidermal growth factor receptor (EGFR). These compounds were synthesized and evaluated for their in vitro cytotoxic activities against a panel of four human tumor cell lines, namely colorectal carcinoma (HCT-116), hepatocellular carcinoma (HepG-2), breast cancer (MCF-7), and non-small cell lung cancer cells (A549). Five of the synthesized compounds, 11a, 11b, 12b, 15b and 16a, were found to exhibit moderate antiproliferative activity against the tested cell lines and were more active than the EGFR inhibitor erlotinib. In particular, compound 11b showed 4.5- to 8.4-fold erlotinib activity against HCT-116, HepG-2, MCF-7, and A549 cells with IC50 values of 3.37, 3.04, 4.14, and 2.4 μM respectively. Moreover, the most cytotoxic compounds that showed promising IC50 values against the four cancer cell lines were subjected to further investigation for their kinase inhibitory activities against EGFRWT and EGFRT790M using homogeneous time resolved fluorescence (HTRF) assay. Compound 11b was also found to be the most active compound against both EGFRWT and mutant EGFRT790M, exhibiting IC50 values of 0.09 and 4.03 μM, respectively. The cell cycle and apoptosis analyses revealed that compound 11b can arrest the cell cycle at the G2/M phase and induce significant apoptotic effects in HCT-116, HepG-2, and MCF-7 cells. Additionally, compound 11b upregulated the level of caspase-3 by 6.5 fold in HepG-2 when compared with the control. Finally, molecular docking studies were carried out to examine the binding mode of the synthesized compounds against the proposed targets; EGFRWT and EGFRT790M. Additional in silico ADMET studies were performed to explore drug-likeness properties.

We describe the total synthesis of tutuilamide A, a potent porcine pancreatic elastase (PPE) inhibitor and a representative member of the 3-amino-6-hydroxy-2-piperidone (Ahp) cyclodepsipeptide family, isolated from marine cyanobacteria. The Ahp unit serves as a pharmacophore and the adjacent 2-amino-2-butenoic acid (Abu) is a main driver of the selectivity among serine proteases. We adapted our previous convergent strategy to generate the macrocycle, common with lyngbyastatin 7 and related elastase inhibitors, and then appended the tutuilamide A-specific side chain bearing a vinyl chloride. Tutuilamide A and lyngbyastatin 7 were evaluated side by side for the inhibition of the disease-relevant human neutrophil elastase (HNE). Tutuilamide A and lyngbyastatin 7 were approximately equipotent against HNE, while tutuilamide A was previously shown to be more active against PPE compared with lyngbyastatin 7, further demonstrating that the side chain provides opportunities to not only modulate potency but also selectivity among proteases of the same function from different organisms. Profiling of tutuilamide A against mainly human serine proteases revealed high selectivity for HNE (IC50 0.73 nM) and pleiotropic activity against kallikrein 7 (KLK7, IC50 5.0 nM), without affecting other kallikreins, similarly to lyngbyastatin 7 (IC50 0.85 nM for HNE and 3.1 nM for KLK7). A comprehensive molecular docking study for elastases and KLK7 afforded deeper insight into the intricate differences between inhibitor interactions with HNE and PPE, accounting for the differential activities for both compounds. The synthesis and molecular studies serve as a proof-of-concept that the macrocyclic scaffold can be diversified to fine-tune the activity of serine protease inhibitors.

New modified depsipeptides and geometric isomers, termed anaenamides A (1a) and B (1b), along with the presumptive biosynthetic intermediate, anaenoic acid (2), were discovered from a marine cyanobacterium from Guam. Structures were confirmed by total synthesis. The alkyl-salicylic acid fragment and the C-terminal α-chlorinated α,β-unsaturated ester are novelties in cyanobacterial natural products. Cancer cell viability assays indicated that the C-terminal unit serves as the pharmacophore and that the double bond geometry impacts the cytotoxicity.

Irregular nuclear shapes characterized by blebs, lobules, micronuclei, or invaginations are hallmarks of many cancers and human pathologies. Despite the correlation between abnormal nuclear shape and human pathologies, the mechanism by which the cancer nucleus becomes misshapen is not fully understood. Motivated by recent evidence that modifying chromatin condensation can change nuclear morphology, we conducted a high-throughput RNAi screen to identify epigenetic regulators that are required to maintain normal nuclear shape in human breast epithelial MCF-10A cells. We silenced 608 genes in parallel using an epigenetics siRNA library and used an unbiased Fourier analysis approach to quantify nuclear contour irregularity from fluorescent images captured on a high-content microscope. Using this quantitative approach, which we validated with confocal microscopy, we significantly expand the list of epigenetic regulators that impact nuclear morphology.