Synthesis of benzoxazole-based vorinostat analogs and their antiproliferative activity.

Hydroxamic acid derivatives constitute an interesting novel class of antitumor agents. Three of them, including vorinostat, are approved drugs for the treatment of malignancies, while several others are currently under clinical trials. In this work, we present new vorinostat analogs containing the benzoxazole ring as the cap group and various linkers. The benzoxazole-based analogs were synthesized starting either from 2-aminobenzoxazole, through conventional coupling, or from benzoxazole, through a metal-free oxidative amination. All the synthesized compounds were evaluated for their antiproliferative activity on three diverse human cancer cell lines (A549, Caco-2 and SF268), in comparison to vorinostat. Compound 12 (GK601), carrying a benzoxazole ring replacement for the phenyl ring of vorinostat, was the most potent inhibitor of the growth of three cell lines (IC50 1.2-2.1 µΜ), similar in potency to vorinostat. Compound 12 also inhibited human HDAC1, HDAC2 and HDAC6 like vorinostat. This new analog also showed antiproliferative activity against two colon cancer cell lines genetically resembling pseudomyxoma peritonei (PMP), namely HCT116 GNAS R201C/+ and LS174T (IC50 0.6 and 1.4 µΜ, respectively) with potency comparable to vorinostat (IC50 1.1 and 2.1 µΜ, respectively).

A Potent Antagonist of Protease-Activated Receptor 2 That Inhibits Multiple Signaling Functions in Human Cancer Cells.

Protease-activated receptor 2 (PAR2) is a cell surface protein linked to G-protein dependent and independent intracellular signaling pathways that produce a wide range of physiological responses, including those related to metabolism, inflammation, pain, and cancer. Certain proteases, peptides, and nonpeptides are known to potently activate PAR2. However, no effective potent PAR2 antagonists have been reported yet despite their anticipated therapeutic potential. This study investigates antagonism of key PAR2-dependent signaling properties and functions by the imidazopyridazine compound I-191 (4-(8-(tert-butyl)-6-(4-fluorophenyl)imidazo[1,2-b]pyridazine-2-carbonyl)-3,3-dimethylpiperazin-2-one) in cancer cells. At nanomolar concentrations, I-191 inhibited PAR2 binding of and activation by structurally distinct PAR2 agonists (trypsin, peptide, nonpeptide) in a concentration-dependent manner in cells of the human colon adenocarcinoma grade II cell line (HT29). I-191 potently attenuated multiple PAR2-mediated intracellular signaling pathways leading to Ca2+ release, extracellular signal-regulated kinase 1/2 (ERK1/2) phosphorylation, Ras homologue gene family, member A (RhoA) activation, and inhibition of forskolin-induced cAMP accumulation. The mechanism of action of I-191 was investigated using binding and calcium mobilization studies in HT29 cells where I-191 was shown to be noncompetitive and a negative allosteric modulator of the agonist 2f-LIGRL-NH2 The compound alone did not activate these PAR2-mediated pathways, even at high micromolar concentrations, indicating no bias in these signaling properties. I-191 also potently inhibited PAR2-mediated downstream functional responses, including expression and secretion of inflammatory cytokines and cell apoptosis and migration, in human colon adenocarcinoma grade II cell line (HT29) and human breast adenocarcinoma cells (MDA-MB-231). These findings indicate that I-191 is a potent PAR2 antagonist that inhibits multiple PAR2-induced signaling pathways and functional responses. I-191 may be a valuable tool for characterizing PAR2 functions in cancer and in other cellular, physiological, and disease settings.

Europium-Labeled Synthetic C3a Protein as a Novel Fluorescent Probe for Human Complement C3a Receptor.

Measuring ligand affinity for a G protein-coupled receptor is often a crucial step in drug discovery. It has been traditionally determined by binding putative new ligands in competition with native ligand labeled with a radioisotope of finite lifetime. Competing instead with a lanthanide-based fluorescent ligand is more attractive due to greater longevity, stability, and safety. Here, we have chemically synthesized the 77 residue human C3a protein and conjugated its N-terminus to europium diethylenetriaminepentaacetate to produce a novel fluorescent protein (Eu-DTPA-hC3a). Time-resolved fluorescence analysis has demonstrated that Eu-DTPA-hC3a binds selectively to its cognate G protein-coupled receptor C3aR with full agonist activity and similar potency and selectivity as native C3a in inducing calcium mobilization and phosphorylation of extracellular signal-regulated kinases in HEK293 cells that stably expressed C3aR. Time-resolved fluorescence analysis for saturation and competitive binding gave a dissociation constant (Kd) of 8.7 ± 1.4 nM for Eu-DTPA-hC3a and binding affinities for hC3a (pKi of 8.6 ± 0.2 and Ki of 2.5 nM) and C3aR ligands TR16 (pKi of 6.8 ± 0.1 and Ki of 138 nM), BR103 (pKi of 6.7 ± 0.1 and Ki of 185 nM), BR111 (pKi of 6.3 ± 0.2 and Ki of 544 nM) and SB290157 (pKi of 6.3 ± 0.1 and Ki of 517 nM) via displacement of Eu-DTPA-hC3a from hC3aR. The macromolecular conjugate Eu-DTPA-hC3a is a novel nonradioactive probe suitable for studying ligand-C3aR interactions with potential value in accelerating drug development for human C3aR in physiology and disease.

Repurposing Registered Drugs as Antagonists for Protease-Activated Receptor 2.

Virtual screening of a drug database identified Carvedilol, Loratadine, Nefazodone and Astemizole as PAR2 antagonists, after ligand docking and molecular dynamics simulations using a PAR2 homology model and a putative binding mode of a known PAR2 ligand. The drugs demonstrated competitive binding and antagonism of calcium mobilization and ERK1/2 phosphorylation in CHO-hPAR2 transfected cells, while inhibiting IL-6 secretion in PAR2 expressing MDA-MB-231 breast cancer cells. This research highlights opportunities for GPCR hit-finding from FDA-approved drugs.

Ras-Related Protein Rab5a Regulates Complement C5a Receptor Trafficking, Chemotaxis, and Chemokine Secretion in Human Macrophages.

Complement activation and Rab GTPase trafficking are commonly observed in inflammatory responses. Recruitment of innate immune cells to sites of infection or injury and secretion of inflammatory chemokines are promoted by complement component 5a (C5a) that activates the cell surface protein C5a receptor1 (C5aR1). Persistent activation can lead to a myriad of inflammatory and autoimmune diseases. Here, we demonstrate that the mechanism of C5a induced chemotaxis of human monocyte-derived macrophages (HMDMs) and their secretion of inflammatory chemokines are controlled by Rab5a. We find that C5a activation of the G protein coupled receptor C5aR1 expressed on the surface of HMDMs, recruits ß-arrestin2 via Rab5a trafficking, then activates downstream phosphatidylinositol 3-kinase (PI3K)/Akt signaling that culminates in chemotaxis and secretion of pro-inflammatory chemokines from HMDMs. High-resolution lattice light-sheet microscopy on live cells showed that C5a activates C5aR1-GFP internalization and colocalization with Rab5a-tdTomato but not with dominant negative mutant Rab5a-S34N-tdTomato in HEK293 cells. We found that Rab5a is significantly upregulated in differentiated HMDMs and internalization of C5aR1 is dependent on Rab5a. Interestingly, while knockdown of Rab5a inhibited C5aR1-mediated Akt phosphorylation, it did not affect C5aR1-mediated ERK1/2 phosphorylation or intracellular calcium mobilization in HMDMs. Functional analysis using transwell migration and µ-slide chemotaxis assays indicated that Rab5a regulates C5a-induced chemotaxis of HMDMs. Further, C5aR1 was found to mediate interaction of Rab5a with ß-arrestin2 but not with G proteins in HMDMs. Furthermore, C5a-induced secretion of pro-inflammatory chemokines (CCL2, CCL3) from HMDMs was attenuated by Rab5a or ß-arrestin2 knockdown or by pharmacological inhibition with a C5aR1 antagonist or a PI3K inhibitor. These findings reveal a C5a-C5aR1-ß-arrestin2-Rab5a-PI3K signaling pathway that regulates chemotaxis and pro-inflammatory chemokine secretion in HMDMs and suggests new ways of selectively modulating C5a-induced inflammatory outputs.

N-(2-Aminophenyl)-benzamide Inhibitors of Class I HDAC Enzymes with Antiproliferative and Antifibrotic Activity.

Inhibitors of histone deacetylases (HDACs) have received special attention as novel anticancer agents. Among various types of synthetic inhibitors, benzamides constitute an important class, and one is an approved drug (chidamide). Here, we present a novel class of HDAC inhibitors containing the N-(2-aminophenyl)-benzamide functionality as the zinc-binding group linked to various cap groups, including the amino acids pyroglutamic acid and proline. We have identified benzamides that inhibit HADC1 and HDAC2 at nanomolar concentrations, with antiproliferative activity at micromolar concentrations against A549 and SF268 cancer cell lines. Docking studies shed light on the mode of binding of benzamide inhibitors to HDAC1, whereas cellular analysis revealed downregulated expression of EGFR mRNA and protein. Two benzamides were investigated in a mouse model of bleomycin-induced pulmonary fibrosis, and both showed efficacy on a preventative dosing schedule. N-(2-Aminophenyl)-benzamide inhibitors of class I HDACs might lead to new approaches for treating fibrotic disorders.

Landscaping macrocyclic peptides: stapling hDM2-binding peptides for helicity, protein affinity, proteolytic stability and cell uptake.

Cyclic peptides that modulate protein-protein interactions can be valuable therapeutic candidates if they can be delivered intact to their target proteins in cells. Here we systematically compare the effects of different helix-inducing cyclization constraints on the capacity of a macrocyclic peptide component to confer α-helicity, protein-binding affinity, resistance to degradative proteases and cell uptake to a 12-residue peptide fragment of tumor suppressor protein p53. We varied the helix-inducing constraint (hydrocarbon, lactam, aliphatic or aromatic thioether, etc.) and the position of the cyclization linker (i to i + 4 or i to i + 7 bridges) in order to sculpt the macrocyclic size, stabilize its structure, and promote cell uptake. We find that rigidifying the macrocycle leads to higher alpha helicity, target affinity and proteolytic stability to different extents, whereas cell uptake of compounds shown here is mostly driven by hydrophobicity and aromaticity of the macrocycle.

Differential effect of ECM molecules on re-expression of cartilaginous markers in near quiescent human chondrocytes.

The limited source of healthy primary chondrocytes restricts the clinical application of tissue engineering for cartilage repair. Therefore, method to maintain or restore the chondrocyte phenotype during in vitro expansion is essential. The objective of this study is to establish the beneficial effect of ECM molecules on restoring the re-expression of cartilaginous markers in primary human chondrocytes after extensive monolayer expansion. During the course of chondrocyte serial expansion, COL2A1, SOX9, and AGN mRNA expression levels, and GAG accumulation level were reduced significantly in serially passaged cells. Exogenous type II collagen dose-dependently elevated GAG level and induced the re-expression of cartilaginous marker mRNAs in P7 chondrocytes. Chondroitin sulfate did not show significant effect on P7 chondrocytes, while hyaluronic acid inhibited the expression of SOX9 and AGN mRNAs. Upon treatment with type II collagen, FAK, ERK1/2, and JNK were activated via phosphorylation in P7 chondrocytes within 15 min. Furthermore, GFOGER integrin blocking peptide, MEK inhibitor and JNK inhibitor, not p38 inhibitor, significantly reduced the type II collagen-induced GAG deposition level. Finally, in the presence of TGF-ß1 and IGF-I, P7 chondrocytes cultured in 3D type II collagen matrix exhibited better cartilaginous features than those cells cultured in the type I collagen matrix. In conclusion, type II collagen alone can effectively restore cartilaginous features of expanded P7 human chondrocytes. It is probably mediated via the activation of FAK-ERK1/2 and FAK-JNK signaling pathways. The potential application of type II collagen in expanding a scarcity of healthy chondrocytes in vitro for further tissue engineering is implicated.

PAR2 induces ovarian cancer cell motility by merging three signalling pathways to transactivate EGFR.

BACKGROUND AND PURPOSE: Specific cellular functions mediated by GPCRs are often associated with signalling through a particular G protein or ß-arrestin. Here, we examine signalling through a GPCR, protease-activated receptor 2 (PAR2), in a high-grade serous ovarian cancer cell line (OV90). EXPERIMENTAL APPROACH: Human ovarian cancer tissues (n = 1,200) and nine human ovarian cancer cell lines were assessed for PAR2 expression. PAR2 signalling mechanisms leading to cell migration and invasion were dissected using cellular assays, western blots, CRISPR-Cas9 gene knockouts, pharmacological inhibitors of PAR2 and downstream signalling proteins in OV90 cancer cells. KEY RESULTS: PAR2 was significantly overexpressed in clinical ovarian cancer tissues and in OV90 ovarian cancer cells. PAR2 agonists, an endogenous protease (trypsin) and a synthetic peptide (2f-LIGRL-NH2 ), induced migration and invasion of OV90 ovarian cancer cells through activating a combination of Gαq/11 , Gα12/13 and ß-arrestin1/2, but not Gαs or Gαi . This novel cooperative rather than parallel signalling resulted in downstream serial activation of Src kinases, then transactivation of epidermal growth factor receptor (EGFR), followed by downstream MEK-ERK1/2-FOS/MYC/STAT3-COX2 signalling. Either a PAR2 antagonist (I-191), CRISPR-Cas9 gene knockouts (PAR2 or Gα proteins or ß-arrestin1/2), or inhibitors of each downstream protein attenuated human ovarian cancer cell motility. CONCLUSION AND IMPLICATIONS: This study highlights a novel shared signalling cascade, requiring each of Gαq/11 , Gα12/13 and ß-arrestin1/2 for PAR2-induced ovarian cancer cell migration and invasion. This mechanism controlling a cellular function is unusual in not being linked to a specific individual G protein or ß-arrestin-mediated signalling pathway.

HDAC7 Inhibition by Phenacetyl and Phenylbenzoyl Hydroxamates.

The zinc-containing histone deacetylase enzyme HDAC7 is emerging as an important regulator of immunometabolism and cancer. Here, we exploit a cavity in HDAC7, filled by Tyr303 in HDAC1, to derive new inhibitors. Phenacetyl hydroxamates and 2-phenylbenzoyl hydroxamates bind to Zn2+ and are 50-2700-fold more selective inhibitors of HDAC7 than HDAC1. Phenylbenzoyl hydroxamates are 30-70-fold more potent HDAC7 inhibitors than phenacetyl hydroxamates, which is attributed to the benzoyl aromatic group interacting with Phe679 and Phe738. Phthalimide capping groups, including a saccharin analogue, decrease rotational freedom and provide hydrogen bond acceptor carbonyl/sulfonamide oxygens that increase inhibitor potency, liver microsome stability, solubility, and cell activity. Despite being the most potent HDAC7 inhibitors to date, they are not selective among class IIa enzymes. These strategies may help to produce tools for interrogating HDAC7 biology related to its catalytic site.

Achiral Derivatives of Hydroxamate AR-42 Potently Inhibit Class I HDAC Enzymes and Cancer Cell Proliferation.

AR-42 is an orally active inhibitor of histone deacetylases (HDACs) in clinical trials for multiple myeloma, leukemia, and lymphoma. It has few hydrogen bond donors and acceptors but is a chiral 2-arylbutyrate and potentially prone to racemization. We report achiral AR-42 analogues incorporating a cycloalkyl group linked via a quaternary carbon atom, with up to 40-fold increased potency against human class I HDACs (e.g., JT86, IC50 0.7 nM, HDAC1), 25-fold increased cytotoxicity against five human cancer cell lines, and up to 70-fold less toxicity in normal human cells. JT86 was ninefold more potent than racAR-42 in promoting accumulation of acetylated histone H4 in MM96L melanoma cells. Molecular modeling and structure-activity relationships support binding to HDAC1 with tetrahydropyran acting as a hydrophobic shield from water at the enzyme surface. Such potent inhibitors of class I HDACs may show benefits in diseases (cancers, parasitic infections, inflammatory conditions) where AR-42 is active.

Potent Thiophene Antagonists of Human Complement C3a Receptor with Anti-Inflammatory Activity.

Structure-activity relationships for a series of small-molecule thiophenes resulted in potent and selective antagonism of human Complement C3a receptor. The compounds are about 100-fold more potent than the most reported antagonist SB290157. A new compound JR14a was among the most potent of the new antagonists in vitro, assessed by (a) inhibition of intracellular calcium release (IC50 10 nM) induced in human monocyte-derived macrophages by 100 nM C3a, (b) inhibition of ß-hexosaminidase secretion (IC50 8 nM) from human LAD2 mast cells degranulated by 100 nM C3a, and (c) selectivity for human C3aR over C5aR. JR14a was metabolically stable in rat plasma and in rat liver microsomes and efficacious in rats when given orally to suppress rat paw inflammation, macrophage and mast cell activation, and histopathology induced by intraplantar paw administration of a C3aR agonist. Potent C3aR antagonists are now available for interrogating C3a receptor activation and suppressing C3aR-mediated inflammation in mammalian physiology and disease.

Bicyclic Helical Peptides as Dual Inhibitors Selective for Bcl2A1 and Mcl-1 Proteins.

A 26-residue peptide BimBH3 binds indiscriminately to multiple oncogenic Bcl2 proteins that regulate apoptosis of cancer cells. Specific inhibition of the BimBH3-Bcl2A1 protein-protein interaction was obtained in vitro and in cancer cells by shortening the peptide to 14 residues, inserting two cyclization constraints to stabilize a water-stable α-helix, and incorporating an N-terminal acrylamide electrophile for selective covalent bonding to Bcl2A1. Mass spectrometry of trypsin-digested bands on electrophoresis gels established covalent bonding of an electrophilic helix to just one of the three cysteines in Bcl2A1, the one (Cys55) at the BimBH3-Bcl2A1 protein-protein interaction interface. Optimizing the helix-inducing constraints and the sequence subsequently enabled electrophile removal without loss of inhibitor potency. The bicyclic helical peptides were potent, cell permeable, plasma-stable, dual inhibitors of Bcl2A1 and Mcl-1 with high selectivity over other Bcl2 proteins. One bicyclic peptide was shown to inhibit the interaction between a pro-apoptotic protein (Bim) and either endogenous Bcl2A1 or Mcl-1, to induce apoptosis of SKMel28 human melanoma cells, and to sensitize them for enhanced cell death by the anticancer drug etoposide. These approaches look promising for chemically silencing intracellular proteins.

Biased Signaling by Agonists of Protease Activated Receptor 2.

Protease activated receptor 2 (PAR2) is associated with metabolism, obesity, inflammatory, respiratory and gastrointestinal disorders, pain, cancer, and other diseases. The extracellular N-terminus of PAR2 is a common target for multiple proteases, which cleave it at different sites to generate different N-termini that activate different PAR2-mediated intracellular signaling pathways. There are no synthetic PAR2 ligands that reproduce the same signaling profiles and potencies as proteases. Structure-activity relationships here for 26 compounds spanned a signaling bias over 3 log units, culminating in three small ligands as biased agonist tools for interrogating PAR2 functions. DF253 (2f-LAAAAI-NH2) triggered PAR2-mediated calcium release (EC50 2 µM) but not ERK1/2 phosphorylation (EC50 > 100 µM) in CHO cells transfected with hPAR2. AY77 (Isox-Cha-Chg-NH2) was a more potent calcium-biased agonist (EC50 40 nM, Ca2+; EC50 2 µM, ERK1/2), while its analogue AY254 (Isox-Cha-Chg-A-R-NH2) was an ERK-biased agonist (EC50 2 nM, ERK1/2; EC50 80 nM, Ca2+). Signaling bias led to different functional responses in human colorectal carcinoma cells (HT29). AY254, but not AY77 or DF253, attenuated cytokine-induced caspase 3/8 activation, promoted scratch-wound healing, and induced IL-8 secretion, all via PAR2-ERK1/2 signaling. Different ligand components were responsible for different PAR2 signaling and functions, clues that can potentially lead to drugs that modulate different pathway-selective cellular and physiological responses.

Exploiting a novel conformational switch to control innate immunity mediated by complement protein C3a.

Complement C3a is an important protein in innate and adaptive immunity, but its specific roles in vivo remain uncertain because C3a degrades rapidly to form the C3a-desArg protein, which does not bind to the C3a receptor and is indistinguishable from C3a using antibodies. Here we develop the most potent, stable and highly selective small molecule modulators of C3a receptor, using a heterocyclic hinge to switch between agonist and antagonist ligand conformations. This enables characterization of C3 areceptor-selective pro- vs. anti-inflammatory actions in human mast cells and macrophages, and in rats. A C3a receptor-selective agonist induces acute rat paw inflammation by first degranulating mast cells before activating macrophages and neutrophils. An orally administered C3a receptor-selective antagonist inhibits mast cell degranulation, thereby blocking recruitment and activation of macrophages and neutrophils, expression of inflammatory mediators and inflammation in a rat paw edema model. These novel tools reveal the mechanism of C3a-induced inflammation and provide new insights to complement-based medicines.Complement C3a is an important protein in innate and adaptive immunity, but its roles in vivo are unclear. Here the authors develop novel chemical agonists and antagonists for the C3a receptor, and show that they modulate mast cell degranulation and inflammation in a rat paw edema model.

[Mathematical model in prediction and evaluation of the effects on control measures for schistosomiasis].

OBJECTIVE: To carry out a theoretical research on the rule that a mathematical model may play on predicting and evaluating the control effect of schistosomiasis japonica. METHODS: Earbour's two-host model was used to predict and evaluate the effect of different control measures by computer simulation. Pilot samples in two villages of Shanghai suburb in 1950s were applied for the analysis. RESULTS: When the prevalence was high, synchronous chemotherapy for human and cattle populations quickly reduced the indices of the infection. Mollusciciding provided positive impact on the effect of chemotherapy. Added with the environmental measures for snail control, the basic reproductive rate (BRR) and equilibrium prevalence in human and bovines were sustainably reduced and even reached an interruption of transmission. The effect of chemotherapy could be consolidated by the anti-fecundity vaccine for bovines. Satisfied control effect could also be obtained by chemotherapy in human and bovines combined with behaviour intervention for human and vaccination for bovines without snail control. In areas with lower levels of transmission velocity, BRR and prevalence, the effect of various interventions was better than that obtained in areas with higher levels of the above three infection indices, and the disease control could be easier. Conclusion The Barbour's mathematical model can be used to roughly predict and evaluate the effects of schistosomiasis control measures.