The anti-cancer effects of quinolone antibiotics?

Green Approach Toward Triazole Forming Reactions for Developing Anticancer Drugs

Compounds containing triazole have many significant applications in the dye and ink industry, corrosion inhibitors, polymers, and pharmaceutical industries. These compounds possess many antimicrobial, antioxidant, anticancer, antiviral, anti-HIV, antitubercular, and anticancer activities. Several synthetic methods have been reported for reducing time, minimizing synthetic steps, and utilizing less hazardous and toxic solvents and reagents to improve the yield of triazoles and their analogues synthesis. Among the improvement in methods, green approaches towards triazole forming biologically active compounds, especially anticancer compounds, would be very important for pharmaceutical industries as well as global research community. In this article, we have reviewed the last five years of green chemistry approaches on click reaction between alkyl azide and alkynes to install 1,2,3-triazole moiety in natural products and synthetic drug-like molecules, such as in colchicine, flavanone cardanol, bisphosphonates, thiabendazoles, piperazine, prostanoid, flavonoid, quinoxalines, C-azanucleoside, dibenzylamine, and aryl-azotriazole. The cytotoxicity of triazole hybrid analogues was evaluated against a panel of cancer cell lines, including multidrug-resistant cell lines.

Investigating the potential anticancer activities of antibiotics as topoisomerase II inhibitors and DNA intercalators: in vitro, molecular docking, molecular dynamics, and SAR studies

Topoisomerase II (TOP-2) is a promising molecular target for cancer therapy. Numerous antibiotics could interact with biologically relevant macromolecules and provoke antitumor potential. Herein, molecular docking studies were used to investigate the binding interactions of 138 antibiotics against the human topoisomerase II-DNA complex. Followed by the MD simulations for 200 ns and MM-GBSA calculations. On the other hand, the antitumor activities of the most promising candidates were investigated against three cancer cell lines using doxorubicin (DOX) as a reference drug. Notably, spiramycin (SP) and clarithromycin (CL) showed promising anticancer potentials on the MCF-7 cell line. Moreover, azithromycin (AZ) and CL exhibited good anticancer potentials against the HCT-116 cell line. Finally, the TOP-2 enzyme inhibition assay was carried out to confirm the proposed rationale. Briefly, potent TOP-2 inhibitory potentials were recorded for erythromycin (ER) and roxithromycin (RO). Additionally, a SAR study opened eyes to promising anticancer pharmacophores encountered by these antibiotics.HighlightsMolecular docking studies of 139 antibiotics against the topoisomerase II-DNA complex.SP, RO, AZ, CL, and ER were the most promising and commercially available candidates.Molecular dynamics simulations for 200 ns for the most promising five complexes.MM-GBSA calculations for the frontier five complexes.SP and CL showed promising anticancer potentials on the MCF-7 cell line, besides, AZ and CL exhibited good anticancer potentials against the HCT-116 cell line.Potent TOP-2 inhibitory potentials were recorded for ER and RO.

Upregulation of wild-type p53 by small molecule-induced elevation of NQO1 in non-small cell lung cancer cells

The tumor suppressor p53 is usually inactivated by somatic mutations in malignant neoplasms, and its reactivation represents an attractive therapeutic strategy for cancers. Here, we reported that a new quinolone compound RYL-687 significantly inhibited non-small cell lung cancer (NSCLC) cells which express wild type (wt) p53, in contract to its much weaker cytotoxicity on cells with mutant p53. RYL-687 upregulated p53 in cells with wt but not mutant p53, and ectopic expression of wt p53 significantly enhanced the anti-NSCLC activity of this compound. RYL-687 induced production of reactive oxygen species (ROS) and upregulation of Nrf2, leading to an elevation of the NAD(P)H:quinoneoxidoreductase-1 (NQO1) that can protect p53 by inhibiting its degradation by 20S proteasome. RYL-687 bound NQO1, facilitating the physical interaction between NQO1 and p53. NQO1 was required for RYL-687-induced p53 accumulation, because silencing of NQO1 by specific siRNA or an NQO1 inhibitor uridine, drastically suppressed RYL-687-induced p53 upregulation. Moreover, a RYL-687-related prodrug significantly inhibited tumor growth in NOD-SCID mice inoculated with NSCLC cells and in a wt p53-NSCLC patient-derived xenograft mouse model. These data indicate that targeting NQO1 is a rational strategy to reactivate p53, and RYL-687 as a p53 stabilizer bears therapeutic potentials in NSCLCs with wt p53.

New promising levofloxacin derivatives: Design, synthesis, cytotoxic activity screening, Topo2β polymerase inhibition assay, cell cycle apoptosis profile analysis

Newly designed levofloxacin analogues were synthesized to act as topoisomerase II beta inhibitors (Topo2β). Their cytotoxic activity was screened against breast, liver, and leukemia cancer cell lines. The best activity against liver cancer cell line (Hep3B) was exhibited by the target compounds 3c, 3e, 4a, and 6d (IC₅₀ = 2.33, 1.38, 0.60 and 0.43, respectively). (L-SR) leukemia cancer cell line was pronouncedly affected by compounds 3b, 3g and 4a (IC₅₀ = 1.62, 1.41 and 1.61, sequentially). 3c possessed the best activity against breast cancer cell line (MCF-7) with IC₅₀ = 0.66. Compounds 3c, 3e, 3g, 4a and 4c exhibited Topo2β inhibition activities exceeding etoposide and levofloxacin as reference drugs and variant cell lines. In DNA-Flow cytometry cell cycle analysis, compound 3c arrested the cell cycle at G2/M phase like etoposide and levofloxacin, while compounds 3e and 4a exhibit its arrest at S phase. In addition, 3c, 3e and 4a showed a significant elevation in active caspase-3 levels (10.01, 8.98 and 10.71 folds, respectively). The effect of the new compounds on normal cells was also investigated including breast (MCF10a), liver (THLE2), and lymphocytic (PCS-800-011) normal cell lines.

Selective toxicity of antibacterial agents-still a valid concept or do we miss chances and ignore risks?

BACKGROUND

Selective toxicity antibacteribiotics is considered to be due to interactions with targets either being unique to bacteria or being characterized by a dichotomy between pro- and eukaryotic pathways with high affinities of agents to bacterial- rather than eukaryotic targets. However, the theory of selective toxicity oversimplifies the complex modes of action of antibiotics in pro- and eukaryotes.

METHODS AND OBJECTIVE

This review summarizes data describing multiple modes of action of antibiotics in eukaryotes.

RESULTS

Aminoglycosides, macrolides, oxazolidinones, chloramphenicol, clindamycin, tetracyclines, glycylcyclines, fluoroquinolones, rifampicin, bedaquillin, ß-lactams inhibited mitochondrial translation either due to binding to mitosomes, inhibition of mitochondrial RNA-polymerase-, topoisomerase 2ß-, ATP-synthesis, transporter activities. Oxazolidinones, tetracyclines, vancomycin, ß-lactams, bacitracin, isoniazid, nitroxoline inhibited matrix-metalloproteinases (MMP) due to chelation with zinc and calcium, whereas fluoroquinols fluoroquinolones and chloramphenicol chelated with these cations, too, but increased MMP activities. MMP-inhibition supported clinical efficacies of ß-lactams and daptomycin in skin-infections, and of macrolides, tetracyclines in respiratory-diseases. Chelation may have contributed to neuroprotection by ß-lactams and fluoroquinolones. Aminoglycosides, macrolides, chloramphenicol, oxazolidins oxazolidinones, tetracyclines caused read-through of premature stop codons. Several additional targets for antibiotics in human cells have been identified like interaction of fluoroquinolones with DNA damage repair in eukaryotes, or inhibition of mucin overproduction by oxazolidinones.

CONCLUSION

The effects of antibiotics on eukaryotes are due to identical mechanisms as their antibacterial activities because of structural and functional homologies of pro- and eukaryotic targets, so that the effects of antibiotics on mammals are integral parts of their overall mechanisms of action.

Assembly of Benzothiazine and Triazole in a Single Molecular Entity: Synthesis of -Oxicam Derived Novel Molecules as Potential Antibacterial/ Anti-cancer Agents

BACKGROUND

Benzothiazine derivatives, because of their various biological activities have attracted particular attention in Med Chem and drug discovery efforts. The synthetic modifications of 1,2-benzothiazine 1,1-dioxides have been undertaken in order to explore and identify novel compounds or new analogues possessing promising biological activities. In our effort we have designed -oxicam derived bezothiazine-1,2,3-triazole derivatives as potential antibacterial agents.

METHODS

These compounds were synthesized via a multi-step sequence involving the Cu catalyzed azide- alkyne cycloaddition (CuAAC) as a key step. The CuAAC proceeded at room temperature in DMF to afford 26 novel molecules in good (70-90%) yields.

RESULTS

All these compounds were tested for their antibacterial properties against four strains of bacterial microorganisms and subsequently cytotoxic properties against lung and colon cancer cell lines. The compound 4e showed activities against majority of the bacterial species used (nearly comparable to amoxicillin, ciprofloxacin and ofloxacin against P. vulgaris) whereas 4d and 4f showed cytotoxicities selective towards cancer cells.

CONCLUSION

The present bezothiazine-1,2,3-triazole framework represents a new template for the identification of novel and potent antibacterial/anticancer agents.

Chemical tuning for potential antitumor fluoroquinolones

Phototoxic effects of 6,8 dihalogenated quinolones confers to this type of molecules a potential property as photochemotherapeutic agents. Two photodehalogenation processes seem to be involved in the remarkable photoinduced cellular damage. In this context, a new 6,8 dihalogenated quinolone 1 (1-methyl-6,8-difluoro-4-oxo-7-aminodimethyl-1,4-dihydroquinoline-3-carboxylic acid) was synthetized looking for improving the phototoxic properties of fluoroquinolones (FQ) and to determine the role of the photodegradation pathways in the FQ phototoxicity. With this purpose, fluorescence emissions, laser flash photolysis experiments and photodegradation studies were performed with compound 1 using 1-ethyl-6,8-difluoro-4-oxo-7-aminodimethyl-1,4-dihidroquinoline-3-carboxylic acid (2) and lomefloxacin (LFX) as reference compounds. The shortening of alkyl chain of the N(1) of the quinolone ring revealed a lifetime increase of the reactive aryl cation generated from photolysis of the three FQ and a significant reduction of the FQ photodegradation quantum yield. The fact that these differences were smaller when the same study was done using a hydrogen donor solvent (ethanol-aqueous buffer, 50/50 v/v) evidenced the highest ability of the reactive intermediate arising from 1 to produce intermolecular alkylations. These results were correlated with in vitro 3T3 NRU phototoxicity test. Thus, when Photo-Irritation-Factor (PIF) was determined for 1, 2 and LFX using cytotoxicity profiles of BALB/c 3T3 fibroblasts treated with each compound in the presence and absence of UVA light, a PIF more higher than 30 was obtained for 1 while the values for 2 and LFX were only higher than 8 and 10, respectively. Thereby, the present study illustrates an approach to modulate the photosensitizing properties of FQ with the purpose to improve the chemotherapeutic properties of antitumor quinolones. Moreover, the results obtained in this study also evidence that the key pathway responsible for the phototoxic properties associated with dihalogenated quinolones is the aryl cation generation.

A new quinolone alkaloid from the fruits of Tetradium ruticarpum

A rare new quinolone alkaloid containing three degrees of unsaturation in the side chain, named as 1-methyl-2-[(6Z,9Z,12Z)-6,9,12-pentadecatriene]-4(1H)-quinolone (1), together with three known quinolone alkaloids 1-methyl-2-[(6Z,9Z)-6,9-pentadecadienyl]-4(1H)-quinolone (2), 1-methyl-2-[(4Z,7Z)-4,7-tridecadienyl]-4(1H)-quinolone (3), 1-methyl-2-[(Z)-8-tridecenyl]-4(1H)-quinolone (4), were isolated from the fruits of Tetradium ruticarpum (A.Juss.) T.G.Hartley. Their structures were elucidated by physicochemical properties and spectroscopic data. All compounds were evaluated for their cytotoxic activities against three human tumor cell lines, including Lovo, MDA-MB-231, HeLa cells, by MTT method in 96-well microplates, and compounds 1 exhibited potent activity against MDA-MB-231 cells with IC50 values of 7.95 μM.

Using human experience to identify drug repurposing opportunities: theory and practice

Retrospective evidence drawn from real-world experience of a medicine's use outside its labelled indication is one of a number of techniques used in drug repurposing (DRP). Relying as it does on large numbers of real incidences of human experience, rather than individual case reports with limited statistical support, preclinical experiments with poor translatability or in silico associations, which are early-stage hypotheses, it represents the best validated form of DRP. Cancer is the most frequent of such DRP examples (e.g. aspirin in pancreatic cancer, hazard ratio = 0.25). This approach can be combined with pathway analysis to provide first-in-class treatments for complex diseases. Alternatively, it can be combined with prospective preclinical studies to uncover a validated mechanism for a new indication, after which a repurposed molecule is chemically optimized.

Search of Allosteric Inhibitors and Associated Proteins of an AKT-like Kinase from Trypanosoma cruzi

Proteins associated to the PI3K/AKT/mTOR signaling pathway are widely used targets for cancer treatment, and in recent years they have also been evaluated as putative targets in trypanosomatids parasites, such as Trypanosoma cruzi. Here, we performed a virtual screening approach to find candidates that can bind regions on or near the Pleckstrin homology domain of an AKT-like protein in T. cruzi. The compounds were also evaluated in vitro. The in silico and experimental results allowed us to identify a set of compounds that can potentially alter the intracellular signaling pathway through the AKT-like kinase of the parasite; among them, a derivative of the pyrazolopyridine nucleus with an IC₅₀ of 14.25 ± 1.00 μM against amastigotes of T. cruzi. In addition, we built a protein–protein interaction network of T. cruzi to understand the role of the AKT-like protein in the parasite, and look for additional proteins that can be postulated as possible novel molecular targets for the rational design of compounds against T. cruzi.

Immunobiological efficacy and immunotoxicity of novel synthetically prepared fluoroquinolone ethyl 6-fluoro-8-nitro-4-oxo-1,4-dihydroquinoline-3-carboxylate

The present study examined the cytotoxicity, anti-cancer reactivity, and immunomodulatory properties of new synthetically prepared fluoroquinolone derivative 6-fluoro-8-nitro-4-oxo-1,4-dihydroquinoline-3-carboxylate (6FN) in vitro. The cytotoxicity/toxicity studies (concentrations in the range 1-100μM) are focused on the cervical cancer cells HeLa, murine melanoma cancer cells B16, non-cancer fibroblast NIH-3T3 cells and reconstructed human epidermis tissues EpiDerm™. The significant growth inhibition of cancer cells HeLa and B16 was detected. The cytotoxicity was mediated via apoptosis-associated with activation of caspase-9 and -3. After 72h of treatment, the two highest 6FN concentrations (100 and 50μM) induced toxic effect on epidermis tissue EpiDerm™, even the structural changes in tissue were observed with concentration of 100μM. The effective induction of RAW 264.7 macrophages cell-release of pro- and anti-inflammatory T_H1, T_H2 and T_H17 cytokines, with anti-cancer and/or anti-infection activities, respectively, has been revealed even following low-dose exposition.

Amino acid or peptide conjugates of acridine/acridone and quinoline/quinolone-containing drugs. A critical examination of their clinical effectiveness within a twenty-year timeframe in antitumor chemotherapy and treatment of infectious diseases

Acridines/acridones, quinolines/quinolones (chromophores) and their derivatives constitute extremely important family of compounds in current medicine. Great significance of the compounds is connected with antimicrobial and antitumor activities. Combining these features together in one drug seems to be long-term benefit, especially in oncology therapy. The attractiveness of the chromophore drugs is still enhanced by elimination their toxicity and improvement not only selectivity, specificity but also bioavailability. The best results are reached by conjugation to natural peptides. This paper highlights significant advance in the study of amino acid or peptide chromophore conjugates that provide highly encouraging data for novel drug development. The structures and clinical significance of amino acid or peptide chromophore conjugates are widely discussed.

LZ-106, a novel analog of enoxacin, inducing apoptosis via activation of ROS-dependent DNA damage response in NSCLCs

Lung cancer, especially non-small-cell lung cancer (NSCLC), plays the leading role in cancer which is closely related to a myriad of fatal results. Unfortunately, current molecular mechanisms and clinical treatment of NSCLC still remain to be explored despite the fact that intensive investigations have been carried out in the last two decades. Recently, growing attention to finding exploitable sources of anticancer agents is refocused on quinolone compounds, an antibiotic with a long period of clinic application, for their remarkable cell-killing activity against not only bacteria, but eukaryotes as well. In this study, we found LZ-106, an analog of enoxacin, exhibiting potent inhibitory effects on NSCLC in both cultured cells and xenograft mouse model. We identified apoptosis-inducing action of LZ-106 in NSCLC cells through the mitochondrial and endoplasmic reticulum (ER)-stress apoptotic pathways via Annexin-V/PI double-staining assay, membrane potential detection, calcium level detection and the expression analysis of the key apoptotic proteins. Through comet assay, reactive oxygen species (ROS) detection, the expression analysis of DNA damage response (DDR) marker γ-H2AX and other DDR-related proteins, we also demonstrated that LZ-106 notably induced ROS overproduction and DDR. Interestingly, additional evidence in our findings revealed that DDR and apoptosis could be alleviated in the presence of ROS scavenger N-acetyl-cysteine (NAC), indicating ROS-dependent DDR involvement in LZ-106-induced apoptosis. Thus our data not only offered a new therapeutic candidate for NSCLC, but also put new insights into the pharmacological research of quinolones.

Tumour cell population growth inhibition and cell death induction of functionalized 6-aminoquinolone derivatives

OBJECTIVES

A number of previous studies has provided evidence that the well-known anti-bacterial quinolones may have potential as anti-cancer drugs. The aim of this study was to evaluate potential anti-tumour activity and selectivity of a set of 6-aminoquinolones showing some chemical similarity to naphthyridone derivative CX-5461, recently described as innovative anti-cancer agent.

MATERIALS AND METHODS

In-house quinolones 1-8 and ad hoc synthesized derivatives 9-13 were tested on Michigan Cancer Foundation-7 (MCF-7) breast cancer cells and mesenchymal progenitor (MePR2B) cell lines, analysing their effects on the cell cycle and cell death using FACS methodology. Activation of p53 was evaluated by western blotting.

RESULTS

Benzyl esters 4, 5 and their amide counterparts 12, 13 drastically modulated MCF-7 cell cycles inducing DNA fragmentation and cell death, thus proving to be potential anti-tumour compounds. When assayed in non-tumour MePR2B cells, compounds 4 and 5 were cytotoxic while 12 and 13 had a certain degree of selectivity, with compound 12 emerging as the most promising. Western blot analysis revealed that severe p53-K382ac activation was promoted by benzylester 5. In contrast, amide 12 exerted only a moderate effect which was, however, comparable to that of suberoylanilide hydoxamic acid (SAHA).

CONCLUSIONS

Taken together, these results further reinforce evidence that quinolones have potential as anti-cancer agents. Future work will be focused on understanding compound 12 mechanisms of action, and to obtain more potent and selective compounds.

Synthesis and potential antitumor activity of 7-(4-substituted piperazin-1-yl)-4-oxoquinolines based on ciprofloxacin and norfloxacin scaffolds: in silico studies

The potential antitumor activities of a series of 7-(4-substituted piperazin-1-yl)fluoroquinolone derivatives (1-14a,b) using ciprofloxacin and norfloxacin as scaffolds are described. These compounds exhibit potent and broad spectrum antitumor activities using 60 human cell lines in addition to the inherent antibacterial activity. Compounds 1a, 2a, 3b, 6b and 7a were found to be the most potent, while 2b, 5b, and 6a were found to have an average activity. The results of this study demonstrated that compounds 1a, 2a, 3b, 6b and 7a (mean GI50; 2.63-3.09 µM) are nearly 7-fold more potent compared with the positive control 5-fluorouracil (mean GI50; 22.60 µM). More interestingly, compounds 1a, 2a, 3b, 6b and 7a have an almost antitumor activity similar to gefitinib (mean GI50; 3.24 µM) and are nearly 2-fold more potent compared to erlotinib (mean GI50; 7.29 µM). In silico study and ADME-Tox prediction methodology were used to study the antitumor activity of the most active compounds and to identify the structural features required for antitumor activity.

Novel benzoxepine-1,2,3-triazole hybrids: synthesis and pharmacological evaluation as potential antibacterial and anticancer agents

A remarkably rapid CuAAC strategy afforded benzoxepine-1,2,3-triazole hybrids as potential antibacterial/cytotoxic agents.

Seeking the mechanism responsible for fluoroquinolone photomutagenicity: a pulse radiolysis, steady-state, and laser flash photolysis study

The mechanism responsible for the remarkable photomutagenicity of fluoroquinolone (FQ) antibiotics remains unknown. For this reason, it was considered worthwhile to study in detail the interactions between DNA and a dihalogenated FQ such as lomefloxacin (LFX; one of the most photomutagenic FQs) and its N-acetyl derivative ALFX. Studies of photosensitized DNA damage by (A)LFX, such as formation of DNA single-strand breaks (SSBs), together with pulse radiolysis, laser flash photolysis, and absorption and fluorescence measurements, have shown the important effects of the cationic character of the piperazinyl ring on the affinity of this type of drug for DNA. Hence, the formation of SSBs was detected for LFX, whereas ALFX and ciprofloxacin (a monofluorated FQ) needed a considerably larger dose of light to produce some damage. In this context, it was determined that the association constant (Ka) for the binding of LFX to DNA is ca. 2×10(3)M(-1), whereas in the case of ALFX it is only ca. 0.5×10(3)M(-1). This important difference is attributed to an association between the cationic peripheral ring of LFX and the phosphate moieties of DNA and justifies the DNA SSB results. The analysis of the transient species detected and the photomixtures has allowed us to establish the intermolecular processes involved in the photolysis of FQ in the presence of DNA and 2'-deoxyguanosine (dGuo). Interestingly, although a covalent binding of the dihalogenated FQ to dGuo occurs, the photodegradation of FQ…DNA complexes did not reveal any significant covalent attachment. Another remarkable outcome of this study was that (A)LFX radical anions, intermediates required for the onset of DNA damage, were detected by pulse radiolysis but not by laser flash photolysis.

Gemifloxacin inhibits migration and invasion and induces mesenchymal-epithelial transition in human breast adenocarcinoma cells

Gemifloxacin (GMF) is a fluoroquinolone antibiotic that inhibits bacterial DNA gyrase and topoisomerase IV. The aim of this study was to investigate the anti-metastatic activities of GMF and its possible mechanisms of action, with a special focus on the induction of mesenchymal-epithelial transition (MET). The human breast adenocarcinoma cell lines MDA-MB-231 and MDA-MB-453 were used to assess the anti-metastatic activity of GMF on cell migration and invasion and in scratch wound-healing assays. The effects of GMF on the MET and its regulatory nuclear factor κB (NF-κB)/Snail pathway were assessed. The in vivo anti-metastatic effect of GMF was also evaluated in an animal model. This study demonstrated that GMF inhibited the migration and invasion of MDA-MB-231 and MDA-MB-453 cells and induced the MET. GMF suppressed the activation of NF-κB, as well as the cell migration and invasion induced by tumor necrosis factor α (TNF-α). GMF was shown to inhibit the phosphorylation of the inhibitor of κB (IκB) and the translocation of NF-κB/Snail in both cancer cell lines. This study showed that the Raf kinase inhibitor protein (RKIP), an inhibitor of IκB kinase, is upregulated after GMF treatment. Inhibition of RKIP by small hairpin RNA transfection significantly decreased the inhibitory effect of GMF on the NF-κB/Snail pathway and also inhibited cell migration and invasion. Overexpression of Snail suppressed GMF-mediated metastasis inhibition and E-cadherin upregulation. An animal model revealed that GMF effectively inhibits lipopolysaccharide-mediated metastasis in mice. This study has demonstrated that GMF might be a novel anticancer agent for the prevention and treatment of metastasis in breast cancer.

KEY MESSAGES

GMF inhibits the migration and invasion of human breast adenocarcinoma cells. GMF induces MET by reducing NF-κB and Snail activation and by increasing RKIP levels. GMF has potential clinical implication as an anti-metastatic agent for breast cancer.

Targeting the transposase domain of the DNA repair component Metnase to enhance chemotherapy

Previous studies have shown that the DNA repair component Metnase (SETMAR) mediates resistance to DNA damaging cancer chemotherapy. Metnase has a nuclease domain that shares homology with the Transposase family. We therefore virtually screened the tertiary Metnase structure against the 550,000 compound ChemDiv library to identify small molecules that might dock in the active site of the transposase nuclease domain of Metnase. We identified eight compounds as possible Metnase inhibitors. Interestingly, among these candidate inhibitors were quinolone antibiotics and HIV integrase inhibitors, which share common structural features. Previous reports have described possible activity of quinolones as antineoplastic agents. Therefore, we chose the quinolone ciprofloxacin for further study, based on its wide clinical availability and low toxicity. We found that ciprofloxacin inhibits the ability of Metnase to cleave DNA and inhibits Metnase-dependent DNA repair. Ciprofloxacin on its own did not induce DNA damage, but it did reduce repair of chemotherapy-induced DNA damage. Ciprofloxacin increased the sensitivity of cancer cell lines and a xenograft tumor model to clinically relevant chemotherapy. These studies provide a mechanism for the previously postulated antineoplastic activity of quinolones, and suggest that ciprofloxacin might be a simple yet effective adjunct to cancer chemotherapy.

Immunomodulatory effects of antimicrobial agents. Part I: antibacterial and antiviral agents

Despite impressive therapeutic progresses in the battle against infections, microorganisms are still a threat to mankind. With hundreds of antibacterial molecules, major concerns remain about the emergence of resistant and multidrug-resistant pathogens. On the other hand, the antiviral drug armamentarium is comprised of only a few dozens of compounds which are highly pathogen specific, and resistance is also a concern. According to Arturo Casadevall (Albert Einstein College of Medicine, NY, USA), we have now entered the third era of anti-infective strategy, which intends to favor the interplay between active molecules and the immune system. The first part of this review focuses on the potential immunomodulating properties of anti-infective agents, beginning with antibacterial and antiviral agents.

Synthesis and biological evaluation of tetracyclic thienopyridones as antibacterial and antitumor agents

A facile synthesis of model 4-oxopyrido[3',2':4,5]thieno[3,2-b]indole-3-carboxylic acids 9a-e was achieved via Stille arylation of 2-chloro-3-nitro-4-oxothieno[2,3-b]pyridine-5-carboxylate and a subsequent microwave-assisted phosphite-mediated Cadogan reaction. The new compounds were tested for their in vitro antimicrobial and antiproliferative activity. Compounds 9a-c and 9e exhibited very high potency against Gram positive Bacillus subtilis and Bacillus megaterium at concentrations 0.000015-0.007 μg/mL. They also displayed excellent activity towards other Gram positive bacilli and staphylococci and Gram negative Haemophilus influenzae, being in most cases superior or equal to commercial fluoroquinolones. Both 9a and 9c were inhibitors of the DNA gyrase activity. As concerns antitumor properties, compounds 9b-e showed growth inhibition of MCF-7 breast tumor and A549 non-small cell lung cancer cells with IC(50) 1.6-2.8 μM and 2.6-6.9 μM, respectively, coupled with absence of cytotoxicity towards normal cells. These compounds are promising as dual acting chemotherapeutics.

Effects of substituents on the NMR features of basic bicyclic ring systems of fluoroquinolone antibiotics and the relationships between NMR chemical shifts, molecular descriptors and drug-likeness parameters

In the present study, the NMR spectroscopic features of trovafloxacin (TVA) mesylate, pefloxacin (PFX) mesylate dihydrate and ciprofloxacin (CIP) hydrochloride monohydrate were studied in DMSO-d6 solution with the aim of investigating the effects of substituents and the type of salt on the NMR parameters of basic bicyclic fluoroquinolone and fluoronaphthyridone ring systems. For this purpose, the 1H- and 13C- one- and two-dimensional homo- and heteronuclear NMR methods were used. The analysis of 1H- and 13C-NMR spectra confirmed the structures of investigated fluoroquinolone salts. Relationships between 1H- and 13C-NMR chemical shifts of fluoronaphthyridone and fluoroquinolone ring systems, calculated molecular descriptors (MDs) and drug-likeness scores (DLSs), computed for monoprotonic cations of investigated fluoroquinolone salts (TVAH+, PFXH+ and CIPH+), were also explored. The topological polar surface area (TPSA), the parameter of lipophilicity (miLogP), the relative molecular mass (Mr) and the volume (V) of computed molecular descriptors (MDs), as well as the G protein-coupled receptor ligand-likeness (GPCR ligand-ls), the ion channel ligand-likeness (ICL-ls), the kinase inhibitor-likeness (KI-ls) and the nuclear receptor ligand-likeness (NRL-ls) were used in this study. The 1H-NMR chemical shifts of protons in COOH, H5 and NHn+, as well as 13C-NMR chemical shifts of C4, C5 and C11 shown to be good parameters in exploration of property-property and property-drug-likeness relationships for investigated fluoroquinolone salts. Thus, collinear relationships of 1H-NMR chemical shifts of protons in COOH, H5 and NHn+ with TPSA and miLogP, as well as with GPCR ligand-ls, KI-ls and NRL-ls were revealed (δ, ppm H in COOH vs. TPSA, R = -0.9421; δ, ppm H in COOH vs. NRL-ls, R = -0.9216; δ, ppm H5 vs. miLogP, R = 0.9962; δ, ppm H5 vs. KI-ls, R = 0.9969; δ, ppm NHn+vs. TPSA, R = -0.9875 and δ, ppm NHn+vs. NRL-ls, R = -0.9948). The collinearities between, 13C-NMR chemical shifts of C4, C5 and C11 with KI-ls and NRL-ls, as well as with TPSA, miLogP, Mr and V were also revealed (δ, ppm C4 vs. TPSA, R = 0.9964; δ, ppm C4 vs. miLogP, R = 0.9487; δ, ppm C4 vs.Mr, R = 0.9629; δ, ppm C4 vs. KI-ls, R = 0.9461; δ, ppm C4 vs. NRL-ls, R = 0.9996; δ, ppm C5 vs. miLogP, R = 0.9994; δ, ppm C5 vs. KI-ls, R = 0.9990; δ, ppm C5 vs. NRL-ls, R = 0.9510; δ, ppm C11 vs. TPSA, R = -0,9958; δ, ppm C11 vs. NRL-ls, R = -0.9994 and δ, ppm C11 vs. KI-ls, R = -0.9481).

Chloroquine activates the p53 pathway and induces apoptosis in human glioma cells

Glioblastoma is the most common malignant brain tumor in adults. The currently available treatments offer only a palliative survival advantage and the need for effective treatments remains an urgent priority. Activation of the p53 growth suppression/apoptotic pathway is one of the promising strategies in targeting glioma cells. We show that the quinoline derivative chloroquine activates the p53 pathway and suppresses growth of glioma cells in vitro and in vivo in an orthotopic (U87MG) human glioblastoma mouse model. Induction of apoptosis is one of the mechanisms underlying the effects of chloroquine on suppressing glioma cell growth and viability. siRNA-mediated downregulation of p53 in wild-type but not mutant p53 glioblastoma cells substantially impaired chloroquine-induced apoptosis. In addition to its p53-activating effects, chloroquine may also inhibit glioma cell growth via p53-independent mechanisms. Our results clarify the mechanistic basis underlying the antineoplastic effect of chloroquine and reveal its therapeutic potential as an adjunct to glioma chemotherapy.