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Background: Telomeric repeat-containing RNA (TERRA) is a large non-coding RNA in mammalian cells, which forms an integral component of telomeric heterochromatin. TERRA can bind to an allosteric site of telomeric repeat factor 2 (TRF2), a key component of Shelterin that protect chromosome termini. Both TERRA and TRF2 have been recognized as promising new therapeutic targets for cancer treatment., Methods: Our methods include FRET assay, SPR, CD, microscale thermophoresis (MST), enzyme-linked immunosorbent assay (ELISA), chromatin immunoprecipitation (ChIP), colony formation assays, Western blot, immunofluorescence, cell cycle arrest and apoptosis detection, and xCELLigence real-time cell analysis (RTCA)., Results: In our routine screening of small molecule libraries, we found that a Quindoline derivative, CK1-14 could bind to and stabilize TERRA G-quadruplex structure, which could bind more tightly with an allosteric site of a telomeric binding protein TRF2, resulting in dissociation of TRF2 from telomeric DNA. Further in cellular studies indicated that the above effect of CK1-14 on TERRA G-quadruplex could activate DNA-damage response and cause cell cycle arrest, resulting in inhibition of U2OS cell proliferation and causing cell apoptosis., Conclusions: Our mechanistic studies indicated that interaction of CK1-14 with TERRA induces telomeric DNA-damage response in U2OS cancer cells through inhibition of TRF2. CK1-14 could be further developed as a promising lead compound targeting telomere for cancer treatment., General Significance: Our present study provides the first evidence that allosteric modulation of TRF2 by TERRA G-quadruplex with a binding ligand could become a promising new strategy for cancer treatment especially for ALT tumor cells., (Copyright © 2017 Elsevier B.V. All rights reserved.)

The c-MYC oncogene is overactivated during Burkitt's lymphoma pathogenesis. Targeting c-MYC to inhibit its transcriptional activity has emerged as an effective anticancer strategy. We synthesized four series of disubstituted quindoline derivatives by introducing the second cationic amino side chain and 5-N-methyl group based on a previous study of SYUIQ-5 (1) as c-MYC promoter G-quadruplex ligands. The in vitro evaluations showed that all new compounds exhibited higher stabilities and binding affinities, and most of them had better selectivity (over duplex DNA) for the c-MYC G-quadruplex compared to 1. Moreover, the new ligands prevented NM23-H2, a transcription factor, from effectively binding to the c-MYC G-quadruplex. Further studies showed that the selected ligand, 7a4, down-regulated c-MYC transcription by targeting promoter G-quadruplex and disrupting the NM23-H2/c-MYC interaction in RAJI cells. 7a4 could inhibit Burkitt's lymphoma cell proliferation through cell cycle arrest and apoptosis and suppress tumor growth in a human Burkitt's lymphoma xenograft.

Transcriptional control of c-myc oncogene is an important strategy for antitumor drug design. G-quadruplexes in the promoter region have been proven to be the transcriptional down-regulator of this gene. The transcriptional factor NM23-H2 can reactivate c-myc transcription by unwinding the G-quadruplex structure. Thus, down-regulation of c-myc transcription via disrupting G-quadruplex-NM23-H2 interaction might be a potential approach for cancer therapy. Here, a series of new isaindigotone derivatives were designed and synthesized based on our previous study. The abilities of these derivatives on interacting with G-quadruplexes or NM23-H2, and disrupting G-quadruplex-NM23-H2 interaction were evaluated. Among these derivatives, 19d and 22d showed remarkable abilities on disrupting G-quadruplex-NM23-H2 interaction. They exhibited significant effects on c-myc-relating processes in SiHa cells, including inhibiting the transcription and translation, inhibiting cellular proliferation, inducing apoptosis, and regulating cell cycle. Our findings provided the basis for the anticancer strategy based on c-myc transcriptional regulation via small molecules disrupting G-quadruplex-protein interaction.

Background: Angiogenesis is thought to be important in tumorigenesis and tumor progress. Vascular endothelial growth factor (VEGF) is a pluripotent cytokine and angiogenic growth factor that plays crucial roles in embryonic development and tumor progression. In many types of cancer, VEGF is overexpressed and is generally associated with tumor progression and survival rate. The polypurine/polypyrimidine sequence located upstream of the promoter region in the human VEGF gene can form specific parallel G-quadruplex structures, raising the possibility for transcriptional control of VEGF through G-quadruplex ligands., Methods: PCR stop assay, circular dichroism (CD) spectra, RNA extraction and RT-PCR, enzyme-linked immunosorbent assay (ELISA), luciferase Assays, cell scrape test, xCELLigence real-time cell analysis (RTCA), and chick embryo chorioallantoic membrane (CAM) assay., Results and Conclusions: We found that quindoline derivatives can interact with the G-rich DNA sequences of the VEGF promoter to stabilize this G-quadruplex and suppress the transcription and expression of the VEGF protein. We also demonstrated that these derivatives exhibit potential anti-angiogenic activity in chick embryos and antitumor activity, including the inhibition of cell proliferation and migration., General Significance: Our new findings have significances not only for understanding the mechanism of the G-quadruplex ligands mediating the VEGF transcription inhibition, but also for exploring a new anti-tumor strategy to blocking the transcription of VEGF to inhibit the angiogenesis in cancer cells., (Copyright © 2014 Elsevier B.V. All rights reserved.)

A tailor-made colorimetric and red-emitting fluorescent dual probe for G-quadruplex nucleic acids was developed by incorporating a coumarin-hemicyanine fluorophore into an isaindigotone framework. The significant and distinct changes in both the color and fluorescence of this probe enable the label-free and visual detection of G-quadruplex structures.

A series of isaindigotone derivatives and analogues were designed, synthesized and evaluated as dual inhibitors of cholinesterases (ChEs) and self-induced β-amyloid (Aβ) aggregation. The synthetic compounds had IC(50) values at micro or nano molar range for cholinesterase inhibition, and some compounds exhibited strong inhibitory activity for AChE and high selectivity for AChE over BuChE, which were much better than the isaindigotone derivatives previously reported by our group. Most of these compounds showed higher self-induced Aβ aggregation inhibitory activity than a reference compound curcumin. The structure-activity relationship studies revealed that the derivatives with higher inhibition activity on AChE also showed higher selectivity for AChE over BuChE. Compound 6c exhibiting excellent inhibition for both AChE and self-induced Aβ aggregation was further studied using CD, EM, molecular docking and kinetics., (Copyright © 2012. Published by Elsevier Ltd.)

G-quadruplex structures are a new class of attractive targets for DNA-interactive anticancer agents. The primary building block of this structure is the G-quartet, which is composed of four coplanar guanines and serves as the major binding site for small molecules. NMR studies and molecular dynamics simulations have suggested that the planarity of G-quartet surface has been highly dynamic in solution. To better investigate how the planarity of unfused aromatic ligand impacts on its quadruplex binding properties, a variety of planarity controllable isaindigotone derivatives were designed and synthesized. The interaction of G-quadruplex DNA with these designed ligands was systematically explored using a series of biophysical studies. The FRET-melting, SPR, and CD spectroscopy results showed that reducing the planarity of their unfused aromatic core resulted in their decreased binding affinity and stabilization ability for G-quadruplex. NMR studies also suggested that these compounds could stack on the G-quartet surface. Such results are in parallel with subsequent molecular modeling studies. A detailed binding energy analysis indicated that van der Waals energy (ΔE(vdw)) and entropy (TΔS) are responsible for their decreased quadruplex binding and stabilization effect. All these results provided insight information about how quadruplex recognition could be controlled by adjusting the planarity of ligands, which shed light on further development of unfused aromatic molecules as optimal G-quadruplex binding ligands.

Quindoline derivatives as telomeric quadruplex ligands have shown good biological activity for telomerase inhibition. In the present study, we used spectroscopic and calorimetric methods to investigate the interactions between a quindoline derivative (5-methyl-11-(2-morpholinoethylamino)-10-H-indolo-[3,2-b]quinolin-5-ium iodide, compound 1) and human telomeric G-quadruplex. The thermodynamic studies using isothermal titration calorimetry (ITC) indicated that their binding process was temperature-dependent and enthalpy-entropy co-driven. The significant negative heat capacity was obtained experimentally from the temperature dependence of enthalpy changes, which was consistent with that from theoretical calculation, and all suggesting significant hydrophobic contribution to the molecular recognition process. Based on the results from UV-vis, ITC, steady-state and time-resolved fluorescence, their binding mode was determined as two ligand molecules stacking on the quartets on both ends of the quadruplex. These results shed light on rational design and development of quindoline derivatives as G-quadruplex binding ligands., (Copyright © 2011 Elsevier Inc. All rights reserved.)

Human bcl-2 gene is an apoptosis-related oncogene containing a GC-rich sequence which is located upstream from P1 promoter and has the potential to form G-quadruplex structures. However, the regulatory role of the quadruplex and the effect of its ligands on bcl-2 have not been clarified. Here, we demonstrated that the G-quadruplex structure was disrupted when partial mutation of G --> A was made, resulting in a 2-fold increase in basal transcriptional activity of bcl-2 promoter. Quindoline derivatives, the highly active G-quadruplex ligands developed by our group, could significantly suppress bcl-2 transcriptional activation but had less effect on mutated bcl-2 transcription. These results provided direct evidence that G-quadruplex structure formed in bcl-2 promoter region could function as a transcriptional repressor element, and G-quadruplex specific ligands could regulate the transcription of bcl-2 through stabilization of quadruplex structure. The results further indicated that quindoline derivatives could induce apoptosis of HL-60 tumor cells.

A series of novel rutaecarpine derivatives and related alkaloid derivatives 3-aminoalkanamido-substituted rutaecarpine 4a-f and 7,8-dehydrorutaecarpine 5a-c, and 6-aminoalkanamido-substituted 3-[2-(3-Indolyl)ethyl]-4(3a)-quinazolinones 8a-c, were synthesized and subjected to pharmacological evaluation as acetylcholinesterase (AChE) inhibitors. The synthetic compounds exhibited strong inhibitory activity for AChE and high selectivity for AChE over BuChE. The structure-activity relationships were discussed and their binding conformation and simultaneous interactions mode were further clarified by kinetic characterization and the molecular docking studies., (Copyright (c) 2009 Elsevier Masson SAS. All rights reserved.)

Four isaindigotone derivatives (5a,b and 6a,b) designed as telomeric G-quadruplex ligands have been synthesized and characterized. The unfused aromatic rings in these compounds allow a flexible and adaptive conformation in G-quadruplex recognition. The interaction of human telomeric G-quadruplex DNA with these designed ligands was explored by means of FRET melting, fluorescence titration, CD spectroscopy, continuous variation, and molecular modeling studies. Our results showed that the adaptive scaffold might not only allow the ligands to well occupy the G-quartet but also perfectly bind to the grooves of the G-quadruplex. The synergetic effect of the multiple binding modes might be responsible for the improved binding ability and high selectivity of these ligands toward G-quadruplex over duplex DNA. Long-term exposure of HL60 and CA46 cancer cells to compound 5a showed a remarkable decrease in population growth, cellular senescence phenotype, and shortening of the telomere length, which is consistent with the behavior of an effective telomeric G-quadruplex ligand and telomerase inhibitor.

A series of 5-N-methyl quindoline (cryptolepine) derivatives (2a- x) as telomeric quadruplex ligands was synthesized and evaluated. The designed ligands possess a positive charge at the 5- N position of the aromatic quindoline scaffold. The quadruplex binding of these compounds was evaluated by circular dichroism (CD) spectroscopy, fluorescence resonance energy transfer (FRET) melting assay, polymerase chain reaction (PCR) stop assay, nuclear magnetic resonance (NMR), and molecular modeling studies. Introduction of a positive charge not only significantly improved the binding ability but also induced the selectivity toward antiparallel quadruplex, whereas the nonmethylated derivatives tended to stabilize hybrid-type quadruplexes. NMR and molecular modeling studies revealed that the ligands stacked on the external G-quartets and the positively charged 5- N atom could contribute to the stabilizing ability. Long-term exposure of human cancer cells to 2r showed a remarkable cessation in population growth and cellular senescence phenotype and accompanied by a shortening of the telomere length.

A series of isaindigotone derivatives 5a-d and 6a-d were designed, synthesized and evaluated as acetylcholinesterase and butyrylcholinesterase inhibitors. Results showed that the novel class of isaindigotone derivatives could inhibit both cholinesterases and the selectivity of AChE over BuChE inhibition was related to the aromatic, the species and length of the alkyl amino side chain of compounds. The structure-activity relationships were discussed and their multiple binding modes were further clarified in the molecular docking studies.

A series of 9-aminoalkanamido-1-azabenzanthrones derviatives (3a-i Ar-NHCO(CH(2))(n)NR(1)R(2)) and their quaternary methiodide salts (4a-g Ar-NHCO(CH(2))(n)N(+)(CH(3))R(1)R(2)I(-)) were designed and synthesized as acetylcholinesterase (AChE) or butyrylcholinesterase (BuChE) inhibitors. The synthetic compounds exhibited high AChE inhibitory activity with IC(50) values in the nanomolar range and high selectivity for AChE over BuChE (45- to 1980-fold). The structure-activity relationships (SARs) were discussed.

Stabilization of G-quadruplex structures in the promoter region of certain oncogenes is an emerging field in anticancer drug design. Human c-myc gene is one of these oncogenes, and G-quadruplexes have been proven to be the transcriptional controller of this gene. In the present study, the interaction of quindoline derivatives with G-quadruplexes in c-myc was investigated. The experimental results indicated that these derivatives have the ability to induce/stabilize the G-quadruplexes in c-myc, which lead to down-regulation of the c-myc in the Hep G2 cell line. It was found that derivatives with terminal amino groups in their side chains would selectively bind to the isomers with the double nucleotide loops in the absence of K+. Molecular modeling studies revealed the binding mode between the derivatives and the G-quadruplexes is end-stacking at the 3'-position, and the positively charged side chain on the quindoline derivatives may contribute to the selectivity to certain loop isomers of topological quadruplexes as well as the improved stabilization action.

A new series of quindoline derivatives (4a-j) were designed and synthesized to develop novel and potent telomerase inhibitors. The interaction of the G-quadruplex of human telomere DNA with these newly designed molecules was examined via circular dichroism spectroscopy and electrophoretic mobility shift assay (EMSA). The selectivity between the quindoline derivative (4a) and G-quadruplex or duplex DNA was investigated by competition dialysis. These new compounds as inhibitors of telomerase were also investigated through the utilization of modified telomerase repeat amplification protocol (TRAP) assay. The results revealed that the introduction of electron-donating groups such as substituted amino groups at the C-11 position of quindoline significantly improved the inhibitory effect on telomerase activity ((Tel)IC50 > 138 microM for quindoline, 0.44-12.3 microM for quindoline derivatives 4a-j). The quindoline derivatives not only stabilized the G-quadruplex structure but also induced the G-rich telomeric repeated DNA sequence to fold into quadruplex.

Background and Purpose: Promoting energy metabolism is known to provide therapeutic effects for obesity and associated metabolic disorders. The present study evaluated the therapeutic effects of the newly identified bouchardatine (Bou) on obesity-associated metabolic disorders and the molecular mechanisms of these effects.Experimental Approach: The molecular mode of action of Bou for its effects on lipid metabolism was first examined in 3T3-L1 adipocytes and HepG2 cells. This was followed by an evaluation of its metabolic effects in mice fed a high-fat diet for 16 weeks with Bou being administered in the last 5 weeks. Further mechanistic investigations were conducted in pertinent organs of the mice and relevant cell models.Key Results: In 3T3-L1 adipocytes, Bou reduced lipid content and increased sirtuin 1 (SIRT1) activity to facilitate liver kinase B1 (LKB1) activation of AMPK. Chronic administration of Bou (50 mg∙kg-1 every other day) in mice significantly attenuated high-fat diet-induced increases in body weight gain, dyslipidaemia and fatty liver without affecting food intake and no adverse effects were detected. These metabolic effects were associated with activation of the SIRT1-LKB1-AMPK signalling pathway in adipose tissue and liver. Of particular note, UCP1 expression and mitochondrial biogenesis were increased in both white and brown adipose tissues of Bou-treated mice. Incubation with Bou induced similar changes in primary brown adipocytes isolated from mice.Conclusions and Implications: Bou may have therapeutic potential for obesity-related metabolic diseases by increasing the capacity of energy expenditure in adipose tissues and liver through a mechanism involving the SIRT1-LKB1-AMPK axis. [ABSTRACT FROM AUTHOR]

Abstract: A series of 3-substituted (5c–5f, 6c–6f) and 4-substituted (10a–10g) oxoisoaporphine derivatives were synthesized. It was found that all these synthetic compounds had IC50 values at micro or nano molar range for cholinesterase inhibition, and most of them could inhibit amyloid β (Aβ) self-induced aggregation with inhibition ratio from 31.8% to 57.6%. The structure–activity relationship studies revealed that the derivatives with higher selectivity on AChE also showed better inhibition on Aβ self-induced aggregation. The results from cell toxicity study indicated that most quaternary methiodide salts had higher IC50 values than the corresponding non-quaternary compounds. This study provided potentially important information for further development of oxoisoaporphine derivatives as lead compounds for the treatment of Alzheimer’s disease. [Copyright &y& Elsevier]

Abstract: Aporphine alkaloids, isolated from Chinese medicinal herb, are important natural products. We recently reported that synthetic derivatives of oxoisoaporphine alkaloids exhibited high acetylcholinesterase inhibitory activity and high selectivity for AChE over BuChE (Bioorg. Med. Chem. Lett. 2007, 17, 3765–3768). In this paper, further research results were presented. A series of novel derivatives of oxoaporphine alkaloids (5a–j, 4-carboxylic amide-7-oxo-7H-dibenzo[de,g]quinoline, Ar-CONH(CH2)nNR) and their quaternary methiodide salts (6a–h, Ar-CONH(CH2)nN+(CH3)RI−) were designed and synthesized as acetylcholinesterase (AChE) and/or butyrylcholinesterase (BuChE) inhibitors. The AChE inhibition potency of synthetic oxoaporphine derivatives was decreased about 2–3 orders of magnitude as compared with that of oxoisoaporphine derivatives. Non-competitive binding mode was found for both kinds of derivatives. Molecular docking simulations on the oxoisoaporphine derivatives 7 series and oxoaporphine derivatives 6 series with AChE from Torpedo californica have demonstrated that the ligands bound to the dual-site of the enzyme. [Copyright &y& Elsevier]

Abstract: A series of novel oxoisoaporphine alkaloid derivatives, 9-aminoalkanamido-1-azabenzanthrone (general formula Ar–NHCO(CH2) n NR2, Ar=1-azabenzanthrone, n =1, 2 or 3), had been synthesized. Compared with 1-azabenzanthrone, the derivatives had significantly higher DNA binding affinity with calf thymus DNA, and higher potent cytotoxicity against different tumor cell lines. The cytotoxicity and the structure–activity relationship of the prepared compounds were studied. The derivatives with two methylene groups (n =2), and piperidine or ethanolamine functional group in the side chain exhibited highest DNA binding affinity and cytotoxicity. [Copyright &y& Elsevier]

Abstract: The interaction of berberine and its 9-substituted derivatives with human telomeric DNA d[G3(T2AG3)3](telo21) has been investigated via CD spectroscopy, fluorescence spectroscopy, PCR-stop assay, competitive dialysis, and telomerase repeat amplification protocol (TRAP) assay. The results indicated that these semisynthesized compounds could induce and stabilize the formation of anti-parallel G-quadruplex of telomeric DNA in the presence or absence of metal cations. Compared with berberine, the 9-substituted derivatives exhibit stronger binding affinity with G-quadruplex and higher inhibitory activity for telomerase. Introduction of a side chain with proper length of methylene and terminal amino group to the 9-position of berberine would significantly strengthen the binding affinity with G-quadruplex, resulting in increasing inhibitory effects on the amplification of telo21 DNA and on the telomerase activity. [Copyright &y& Elsevier]