DNA damage and genome instability by G-quadruplex ligands are mediated by R loops in human cancer cells.

G quadruplexes (G4s) and R loops are noncanonical DNA structures that can regulate basic nuclear processes and trigger DNA damage, genome instability, and cell killing. By different technical approaches, we here establish that specific G4 ligands stabilize G4s and simultaneously increase R-loop levels within minutes in human cancer cells. Genome-wide mapping of R loops showed that the studied G4 ligands likely cause the spreading of R loops to adjacent regions containing G4 structures, preferentially at 3'-end regions of expressed genes, which are partially ligand-specific. Overexpression of an exogenous human RNaseH1 rescued DNA damage induced by G4 ligands in BRCA2-proficient and BRCA2-silenced cancer cells. Moreover, even if the studied G4 ligands increased noncanonical DNA structures at similar levels in nuclear chromatin, their cellular effects were different in relation to cell-killing activity and stimulation of micronuclei, a hallmark of genome instability. Our findings therefore establish that G4 ligands can induce DNA damage by an R loop-dependent mechanism that can eventually lead to different cellular consequences depending on the chemical nature of the ligands.

Isatin Bis-Indole and Bis-Imidazothiazole Hybrids: Synthesis and Antimicrobial Activity.

Isatin and its derivatives are important heterocycles found in nature and present in numerous bioactive compounds which possess various biological activities. Moreover, it is an essential building block in organic synthesis. The discovery of novel compounds active against human pathogenic bacteria and fungi is an urgent need, and the isatin may represent the suitable scaffold in the design of biologically relevant antimicrobials. A small library of 18 isatin hybrids was synthetized and evaluated for their antimicrobial potential on three reference strains: S. aureus, E. coli, both important human pathogens infamous for causing community- and hospital-acquired severe systemic infections; and C. albicans, responsible for devastating invasive infections, mainly in immunocompromised individuals. The study highlighted two lead compounds, 6k and 6m, endowed with inhibitory activity against S. aureus at very low concentrations (39.12 and 24.83 µg/mL, respectively).

Synthesis and Biological Evaluation of New Bis-Indolinone Derivatives Endowed with Cytotoxic Activity.

A series of new Knoevenagel adducts, bearing two indolinone systems, has been synthesized and evaluated on 60 human cancer cell lines according to protocols available at the National Cancer Institute (Bethesda, MD, USA). Some derivatives proved to be potent antiproliferative agents, showing GI50 values in the submicromolar range. Compound 5b emerged as the most active and was further studied in Jurkat cells in order to determine the effects on cell-cycle phases and the kind of cell death induced. Finally, oxidative stress and DNA damage induced by compound 5b were also analyzed.

Synthesis and biological evaluation of thiazole derivatives on basic defects underlying cystic fibrosis.

Cystic fibrosis is a genetic disease caused by loss-of-function mutations in the cystic fibrosis transmembrane conductance regulator gene, encoding for CFTR protein. The most frequent mutation is the deletion of phenylalanine at position 508 (F508del), which leads to distinct defects in channel gating and cellular processing. In last years, several thiazole containing small molecules, endowed with dual F508del-CFTR modulator activity, proved to be able to target these defects. In search of new chemical entities able to restore CFTR function, we designed and synthesized a small series of sixteen thiazole derivatives. The designed compounds were studied as correctors and potentiators of F508del-CFTR. Although none of the molecules showed significant corrector activity, compounds 10 and 11 exhibited potentiator effects, thus allowing to determine some basic structural features which enable to obtain F508del-CFTR potentiator activity. In silico ADME studies showed that these derivatives obey Lipinski's rule of five and are expected to be orally bioavailable. Therefore, these molecules may represent a good starting point for the design of analogues endowed with improved CFTR potentiator activity and a good pharmacokinetic profile.

Indole Derivative Interacts with Estrogen Receptor Beta and Inhibits Human Ovarian Cancer Cell Growth.

Ovarian cancer remains the leading cause of mortality among gynecological tumors. Estrogen receptor beta (ERß) expression has been suggested to act as a tumor suppressor in epithelial ovarian cancer by reducing both tumor growth and metastasis. ERß expression abnormalities represent a critical step in the development and progression of ovarian cancer: for these reasons, its re-expression by genetic engineering, as well as the use of targeted ERß therapies, still constitute an important therapeutic approach. 3-{[2-chloro-1-(4-chlorobenzyl)-5-methoxy-6-methyl-1H-indol-3-yl]methylene}-5-hydroxy-6-methyl-1,3-dihydro-2H-indol-2-one, referred to here as compound 3, has been shown to have cytostatic as well cytotoxic effects on various hormone-dependent cancer cell lines. However, the mechanism of its anti-carcinogenic activity is not well understood. Here, we offer a possible explanation of such an effect in the human ovarian cancer cell line IGROV1. Chromatin binding protein assay and liquid chromatography mass spectrometry were exploited to localize and quantify compound 3 in cells. Molecular docking was used to prove compound 3 binding to ERß. Mass spectrometry-based approaches were used to analyze histone post-translational modifications. Finally, gene expression analyses revealed a set of genes regulated by the ERß/3 complex, namely CCND1, MYC, CDKN2A, and ESR2, providing possible molecular mechanisms that underline the observed antiproliferative effects.

Synthesis of 3-(Imidazo[2,1-b]thiazol-6-yl)-2H-chromen-2-one Derivatives and Study of Their Antiviral Activity against Parvovirus B19.

Parvovirus B19 (B19V) is a human pathogenic virus associated with a wide range of clinical conditions. Currently, there are no recognized antiviral drugs for B19V treatment; therefore, efforts in the search for compounds inhibiting B19V replication are now being pursued. Coumarins (chromen-2-ones) are considered a privileged structure for designing novel orally bioavailable and non-peptidic antiviral agents. To further contribute to the development of new drugs against B19V, our research was focused on the synthesis, characterization and evaluation of antiviral activity of some new 3-(imidazo[2,1-b]thiazol-6-yl)-2H-chromen-2-one derivatives. The effects of the synthesized compounds on cell viability and viral replication were investigated by employing two relevant cellular systems, the myeloblastoid cell line UT7/EpoS1 and primary erythroid progenitor cells (EPCs). Some of the tested compounds showed inhibitory activity both on cell viability and on viral replication, depending on the cellular system. These results suggest that the mechanism involved in biological activity is sensitive to small structural changes and that it is possible to direct the activity of the 3-(imidazo[2,1-b]thiazol-6-yl)-2H-chromen-2-one core.

Synthesis and antiproliferative activity of imidazo[2,1-b][1,3,4]thiadiazole derivatives.

A series of 2,5,6-substituted imidazo[2,1-b][1,3,4]thiadiazole derivatives have been prepared and were tested for antiproliferative activity on cancer cells at the National Cancer Institute. Results showed that molecules with a benzyl group at position 2, exhibited an increase in activity for the introduction of a formyl group at the 5 position. The compound 2-benzyl-5-formyl-6-(4-bromophenyl)imidazo[2,1-b][1,3,4]thiadiazole 22 has been chosen for understanding the mechanism of action by various molecular and cellular biology studies. Results obtained from cell cycle evaluation analysis, analysis of mitochondrial membrane potential and Annexin V-FITC by flow cytometric analysis, ROS production and expression of apoptotic and DNA-repair proteins suggested that compound 22 induced cytotoxicity by activating extrinsic pathway of apoptosis, however, without affecting cell cycle progression.

Identification of a new bisindolinone arresting IGROV1 cells proliferation.

In an initial screening, a series of novel Knoevenagel adducts were submitted to the National Cancer Institute for evaluation of antitumor activity in human cell lines. In particular, compound 5f showed remarkable selectivity against IGROV1, an ovarian cancer cell line, without affecting healthy human fibroblast cells. Analyses of cytotoxicity, cell proliferation, cell migration, epigenetic changes, gene expression, and DNA damage were performed to obtain detailed information about its antitumor properties. Our results show that 5f causes proliferation arrest, decrease in motility, histone hyperacetylation, downregulation of cyclin D1 and α5 subunit of integrin ß1 gene transcription. In addition, 5f treatment reduces transcript and protein levels of cyclin D1, which increases sensitivity to ionizing radiation and results in DNA damage comparable to cyclin D1 gene silencing.

Balancing Affinity, Selectivity, and Cytotoxicity of Hydrazone-Based G-Quadruplex Ligands for Activation of Interferon ß Genes in Cancer Cells.

G-quadruplex (G4) ligands are investigated to discover new anticancer drugs with increased cell-killing potency. These ligands can induce genome instability and activate innate immune genes at non-cytotoxic doses, opening the discovery of cytostatic immune-stimulating ligands. However, the interplay of G4 affinity/selectivity with cytotoxicity and immune gene activation is not well-understood. We investigated a series of closely related hydrazone derivatives to define the molecular bases of immune-stimulation activity. Although they are closely related to each other, such derivatives differ in G4 affinity, cytotoxicity, genome instability, and immune gene activation. Our findings show that G4 affinity of ligands is a critical feature for immune gene activation, whereas a high cytotoxic potency interferes with it. The balance of G4 stabilization versus cytotoxicity can determine the level of immune gene activation in cancer cells. Thus, we propose a new rationale based on low cell-killing potency and high immune stimulation to discover effective anticancer G4 ligands.

Synthesis, in vitro cytotoxicity, molecular docking and ADME study of some indolin-2-one linked 1,2,3-triazole derivatives.

In pursuit of an anticancer lead, a library of 1,2,3-triazole derivatives (7a-x) was prepared, characterized and screened for in vitro cytotoxicity in different cell lines. Most of the compounds proved to be cytotoxic with IC50 values in the low micromolar range. Further studies showed that the most active compound 7c induces caspase-dependent apoptosis in Jurkat cells by activating both the intrinsic and the extrinsic apoptotic pathways and perturbs cell-cycle progression. Moreover, 7c did not show any genotoxic activity. Molecular docking simulations were performed against epidermal growth factor receptor (EGFR). Docking experiments showed that, compounds 7c, 7o and 7 v bind within active sites of epidermal growth factor receptor EGFR (Pdb ID: 6P8Q) by strong hydrogen bonds with residue MET793, Pi-Sulfur with residue MET790 and Pi-Alkyl type interactions with residues LEU788, ALA743. The SwissADME webserver investigation suggested that most of the synthesized compounds follow the rules of drug-likeness.

Antitumor activity and COMPARE analysis of bis-indole derivatives.

This paper reports the synthesis of new derivatives (formed by two indole systems separated by a central moiety) analogous of potent antitumor agents previously described. The activity of the bis-indoles bearing a pyridine core confirms the good result described in the previous paper and compound 4c was chosen for the first in vivo experiment (Hollow Fiber Assay). COMPARE analysis and structure-activity relationships were also considered. Contrary to data reported by other Authors, no correlations were found between antitumor activity and NQO1 induction.

Monohydrazone Based G-Quadruplex Selective Ligands Induce DNA Damage and Genome Instability in Human Cancer Cells.

Targeting G-quadruplex structures is currently viewed as a promising anticancer strategy. Searching for potent and selective G-quadruplex binders, here we describe a small series of new monohydrazone derivatives designed as analogues of a lead which was proved to stabilize G-quadruplex structures and increase R loop levels in human cancer cells. To investigate the G-quadruplex binding properties of the new molecules, in vitro biophysical studies were performed employing both telomeric and oncogene promoter G-quadruplex-forming sequences. The obtained results allowed the identification of a highly selective G-quadruplex ligand that, when studied in human cancer cells, proved to be able to stabilize both G-quadruplexes and R loops and showed a potent cell killing activity associated with the formation of micronuclei, a clear sign of genome instability.

Synthesis, in vitro and in vivo biological evaluation of substituted 3-(5-imidazo[2,1-b]thiazolylmethylene)-2-indolinones as new potent anticancer agents.

A small library of 3-(5-imidazo[2,1-b]thiazolylmethylene)-2-indolinones has been synthesized and screened according to protocols available at the National Cancer Institute (NCI). Some derivatives were potent antiproliferative agents, showing GI50 values in the nanomolar range. Remarkably, when most active compounds against leukemia cells were tested in human peripheral blood lymphocytes from healthy donors, were 100-200 times less cytotoxic. Some compounds, selected by the Biological Evaluation Committee of NCI, were examined to determine tubulin assembly inhibition. Furthermore, flow cytometric studies performed on HeLa, HT-29, and A549 cells, showed that compounds 14 and 25 caused a block in the G2/M phase. Interestingly, these derivatives induced apoptosis through the mitochondrial death pathway, causing in parallel significant activation of both caspase-3 and -9, PARP cleavage and down-regulation of the anti-apoptotic proteins Bcl-2 and Mcl-1. Finally, compound 25 was also tested in vivo in the murine BL6-B16 melanoma and E0771 breast cancer cells, causing in both cases a significant reduction in tumor volume.

New antitumor imidazo[2,1-b]thiazole guanylhydrazones and analogues.

The synthesis of new antitumor 6-substituted imidazothiazole guanylhydrazones is described. Moreover, a series of compounds with a different basic chain at the 5 position were prepared. Finally, the replacement of the thiazole ring in the imidazothiazole system was also considered. All the new compounds prepared were submitted to the NCI cell line screen for evaluation of their antitumor activity. A few selected compounds were submitted to additional biological studies concerning effects on the cell cycle, apoptosis, and mitochondria.

Diphenidol-related diamines as novel muscarinic M4 receptor antagonists.

A series of hydrochloride derivatives 2a-9a and quaternary ammonium derivatives 3b-9b of diphenidol have been synthesized and characterized in receptor binding and cellular functional assays versus human muscarinic M(1)-M(5) receptors expressed in CHO cells. Compound 8b, a methiodide derivative with a bipiperidinyl moiety and a second diphenidol framework, showed a potent and selective M(4) activity as competitive antagonist. Moreover 8b, acting as an allosteric modulator, was able to retard the dissociation rate of [(3)H]-N-methylscopolamine from CHO-M(4) cell membranes exposed to atropine. Taken together, these data suggest that 8b might open new avenues to the discovery of novel multivalent antagonists for the muscarinic receptors.

Chemiluminescent high-throughput microassay applied to imidazo[2,1-b]thiazole derivatives as potential acetylcholinesterase and butyrylcholinesterase inhibitors.

The synthesis of a new series of imidazo[2,1-b]thiazole derivatives is described. They were tested as potential acetylcholinesterase and butyrylcholinesterase inhibitors by means of a chemiluminescent microassay. Although most of the new compounds did not show significant cholinesterase inhibition potency, three of them displayed selective antiacetylcholinesterase activity in the micromolar range.

Investigation on the Effects of Antimicrobial imidazo[2,1-b]thiazole Derivatives on the Genitourinary Microflora.

BACKGROUND: Fused five-membered heterocyclic rings containing bridgehead nitrogen atom are particularly versatile in the field of medicinal chemistry because of their different biological activities. Among them, the imidazo[2,1-b]thiazole is an attractive fused heterocyclic core that has been extensively studied. OBJECTIVE: The aim of the current study was to study the therapeutic applications of imidazo[2,1- b]thiazole derivatives as antimicrobial agents for the treatment of genitourinary infections. METHOD: A traditional synthetic methodology was involved to obtain a small series of imidazothiazole derivatives. RESULTS: Herein, we report the antimicrobial activity of the imidazo[2,1-b]thiazole or imidazo[2,1- b]thiazolidine derivatives against selected fungi, Gram-positive and Gram-negative bacteria. Moreover, experiments were carried out to investigate the interference towards the endogenous microbiota. CONCLUSION: The most interesting of the series are the thiocyano derivatives (19, 23) showing a good profile for the treatment of genitourinary infections: a spectrum of activity covering both bacteria and fungi together with a reduced impact versus critical lines of Lactobacillus exerting defense against pathogens.

Substituted E-3-(2-chloro-3-indolylmethylene)1,3-dihydroindol-2-ones with antitumor activity. Effect on the cell cycle and apoptosis.

The synthesis and antitumor activity of new E-3-(2-chloro-3-indolylmethylene)1,3-dihydroindol-2-ones is described. They were studied at the National Cancer Institute, taking into consideration the 50% growth inhibitory power (pGI50), the cytostatic effect (pTGI = total growth inhibition), and the cytotoxic effect (pLC50). All the compounds were potent growth inhibitors, with mean pGI50 ranging from 5.26 to 7.72. They were also analyzed with NCI COMPARE algorithm. Further studies were dedicated to the effects on the cell cycle and apoptosis.

1,4-Anthraquinone: A new useful pre-column reagent for the determination of N-acetylcysteine and captopril in pharmaceuticals by high performance liquid chromatography.

1,4-Anthraquinone (ANQ) is proposed as a novel pre-column reagent for high performance liquid chromatography (HPLC) determination of N-acetylcysteine (NAC) and captopril (CAP) in pharmaceutical formulations. The derivatization reactions were carried out at room temperature: NAC at pH 8 for 1min, while CAP at pH 7.5 for 20min. Both reactions reached completeness at a reagent to thiol molar ratio of about 2.5. The synthesised derivatives were characterized by 1H NMR and IR. The chromatographic separations were performed on a C18 Phenomenex Synergi Fusion 4µm (250mm×4.6mm I.D.) stainless steel column with detection at λ=300nm. The mobile phase consisted of methanol/triethylammonium (TEA) phosphate buffer (pH 3; 0.05mol/L) 75:25 (v/v) at a flow-rate of 0.4mL/min for NAC and 88:12 (v/v), at a flow-rate of 0.6mL/min for CAP. The validation parameters (linearity, sensitivity, accuracy, precision, specificity and stability) were highly satisfactory. Linear response was observed (determination coefficient ≥0.9996). Detection limits were about 8 and 18ng/mL for NAC and CAP, respectively. Intra-day precision (relative standard deviation, R.S.D.) was ≤1.58%, for thiol to internal standard (IS) peak area ratio and ≤0.33%, for thiol and IS retention times (tR), without significant differences between intra- and inter-day data. Thiol recovery studies were satisfactory (99.50%) with R.S.D. ≤0.56%. The results highlight the high sensitivity of the method and the remarkable reactivity and selectivity of the reagent towards the thiol function. The developed method is suitable for the quality control of both thiols in commercial products. The method can be applied in any analytical laboratory not requiring a sophisticated instrumentation.

Antitumor activity of substituted E-3-(3,4,5-trimethoxybenzylidene)-1,3-dihydroindol-2-ones1.

The design and synthesis of anticancer E-3-(3,4,5-trimethoxybenzylidene)-1,3-dihydroindol-2-ones is reported. Strong COMPARE correlations among the cell line responses suggest that these compounds may be acting similarly through a combination of different mechanisms of action. The 5-methoxy derivative (2h) was the most active compound with a mean pGI50 of 6.34, and it is now under review by Biological Evaluation Committee of the National Cancer Institute for possible further studies.