Elucidation of Structure-activity Relationship of 2-Quinolone Derivatives and Exploration of Their Antitumor Potential Through Bax-induced Apoptotic Pathway

Quinolone Derivatives as Anticancer Agents: Importance in Medicinal Chemistry

Quinolone is a heterocyclic compound containing carbonyl at the C-2 or C-4 positions with nitrogen at the C-1 position. The scaffold was first identified for its antibacterial properties, and the derivatives were known to possess many pharmacological activities, including anticancer. In this review, the quinolin-2(H)-one and quinolin-4(H)-one derivatives were identified to inhibit several various proteins and enzymes involved in cancer cell growth, such as topoisomerase, microtubules, protein kinases, phosphoinositide 3-kinases (PI3K) and histone deacetylase (HDAC). Hybrids of quinolone with curcumin or chalcone, 2-phenylpyrroloquinolin-4-one and 4-quinolone derivatives have demonstrated strong potency against cancer cell lines. Additionally, quinolones have been explored as inhibitors of protein kinases, including EGFR and VEGFR. Therefore, this review aims to consolidate the medicinal chemistry of quinolone derivatives in the pipeline and discuss their similarities in terms of their pharmacokinetic profiles and potential target sites to provide an understanding of the structural requirements of anticancer quinolones.

Enantioselective Direct Vinylogous Allylic Alkylation of 4-Methylquinolones under Iridium Catalysis

The first enantioselective vinylogous allylic alkylation of 4-methylquinolones has been developed. This iridium-catalyzed reaction introduces an allyl group at the γ-position of 4-methyl-2-quinolones with exclusive branched selectivity and an excellent level of enantioselectivity. This in turn allows for the enantioselective synthesis of γ-allylquinolines and related nitrogenous heterocycles. This is the first application of 4-methylquinolones in an enantioselective transformation.

A comprehensive review of topoisomerase inhibitors as anticancer agents in the past decade

The topoisomerase enzymes play an important role in DNA metabolism, and searching for enzyme inhibitors is an important target in the search for new anticancer drugs. Discovery of new anticancer chemotherapeutical capable of inhibiting topoisomerase enzymes is highlighted in anticancer research. Therefore, biologists, organic chemists and medicinal chemists all around the world have been identifying, designing, synthesizing and evaluating a variety of novel bioactive molecules targeting topoisomerase. This review summarizes types of topoisomerase inhibitors in the past decade, and divides them into nine classes by structural characteristics, including N-heterocycles compounds, quinone derivatives, flavonoids derivatives, coumarin derivatives, lignan derivatives, polyphenol derivatives, diterpenes derivatives, fatty acids derivatives, and metal complexes. Then we discussed the application prospect and development of these anticancer compounds, as well as concluded parts of their structural-activity relationships. We believe this review would be invaluable in helping to further search potential topoisomerase inhibition as antitumor agent in clinical usage.

Microwave-Assisted Synthesis, Characterisation, and DNA-Binding Properties of RuII Complexes Coordinated by Norfloxacin as Potential Tumour Inhibitors

Three novel norfloxacin-based ruthenium(ii) complexes, [Ru(bpy)2(NFLX)]Cl·2H2O (1), [Ru(phen)2(NFLX)]Cl·2H2O (2), and [Ru(dmbpy)2(NFLX)]Cl·2H2O (3) (bpy=2,2′-bipyridine, phen=1,10-phenanthroline, dmbpy=4,4′-dimethyl-2,2′-bipyridine, and NFLX=norfloxacin), were synthesised and characterised with electrospray ionisation mass spectrometry and 1H and 13C NMR spectroscopy. The antitumour properties were evaluated by MTT assay, and the data revealed that 2 can inhibit the growth of human lung adenocarcinoma A549 efficiently. Furthermore, the DNA-binding behaviours of these complexes were investigated by a multiple spectroscopy assay and viscosity study. The results indicated that these complexes interact with calf thymus DNA through electrostatic interactions with a strong binding affinity in the order 2>3>1. Therefore, these results suggested that 2 might be a suitable anticancer agent due to its excellent DNA-binding abilities.

MiR-133a regarded as a potential biomarker for benzene toxicity through targeting Caspase-9 to inhibit apoptosis induced by benzene metabolite (1,4-Benzoquinone)

Benzene is an environmental and industrial chemical which is widely utilized in various applications. Our previous study showed that miR-133a expression was down-regulated in chronic benzene poisoning workers, but the mechanism of miR-133a in benzene-induced hematotoxicity remains unclear. In this population-based study, benzene-exposed group recruited workers whose concentration of air benzene was 3.50±1.60mg/m(3), and control workers who were exposed to 0.06±0.01mg/m(3) air benzene. By comparison, Caspase-9 and Caspase-3 was up-regulated while miR-133a expression decreased in benzene-exposed workers. Pearson correlation analysis showed that miR-133a was reversely correlated with pro-apoptotic gene Caspase-9 in population-based study. Moreover, multiple linear regressions indicated that miR-133a was positively associated with blood cells count. To explore the underlying mechanism of miR-133a in benzene-induced hematotoxicity, AO/EB staining and TEM ultrastructural analysis were conducted to verify the activation of apoptosis in Human Leukemic U937 Cells induced by benzene metabolites (1,4-Benzoquinone, 1,4-BQ), while the mechanism of miR-133a in 1,4-BQ-induced apoptosis was performed using lentivirus vectors transfection. The results demonstrated that 1,4-BQ evidently induced mitochondria-mediated apoptosis and increased pro-apoptotic genes (Caspase-9 and Caspase-3) expression in a dose-dependent manner. The mechanistic study showed 1,4-BQ decreased miR-133a expression and miR-133a over-expression attenuated 1, 4-BQ-caused upregulation of Caspase-9, Caspase-3 and apoptosis. In conclusion, our research suggested that benzene induced hematotoxicity by decreasing miR-133a and caspase-dependent apoptosis which might contribute to the underlying mechanism of miR-133a in benzene-induced hematotoxicity.

Evaluation of Ceiba pentandra (L.) Gaertner bark extracts for in vitro cytotoxicity on cancer cells and in vivo antitumor activity in solid and liquid tumor models

The stem bark of Ceiba pentandra (L.) Gaertner is claimed to be useful in the treatment of tumors in the southern part of India. This plant possesses a number of sesquiterpenoids and isoflavones which are known for their anticancer properties. The present study was designed to scientifically evaluate the cytotoxic potential of bark extracts in in vitro on Ehrlich ascites carcinoma (EAC), MCF-7 and B16F10 cells and in vivo in EAC (Liquid tumor) model and Dalton's lymphoma ascites (DLA or solid tumor) model. The bark was powdered and extracted successively with solvents viz., petroleum ether (PE), benzene, chloroform, acetone (AC), and ethyl alcohol in the sequential order of polarity. Cytotoxicity of dried extracts was screened on EAC cells by trypan blue assay. Three potent extracts namely petroleum ether, acetone, and ethanol were screened for their cytotoxicity on MCF-7 and B16F10 cells by MTT assay and nucleomorphological alteration by propidium iodide staining. Safe doses of these extracts were evaluated by acute toxicity study in mice. Extracts were found to be safe up to 300 mg/kg in acute toxicity study. Dosage of 1/10th and 1/20th of safe dose i.e., 15 and 30 mg/kg were selected for in vivo study. In the EAC model, both doses of the extracts showed a significant (P < 0.05) improvement in mean survival time and a maximum decline in tumor induced increase in body weight (an indirect measure of tumor weight) by the PE and AC treatment at 15 mg/kg compared to control. In the DLA-model, all extracts at both tested dose levels showed >50 % reduction in tumor weight and a significant reduction (P < 0.05) in tumor volume on the 30th day compared to control. It can be concluded that these extracts possess cytotoxic and antitumor activity.

Amphipathic silica nanoparticles induce cytotoxicity through oxidative stress mediated and p53 dependent apoptosis pathway in human liver cell line HL-7702 and rat liver cell line BRL-3A

The aim of this study was to evaluate the potential cytotoxicity and the underlying mechanism of amphipathic silica nanoparticles (SiO2 NPs) exposure to human normal liver HL-7702 cells and rat normal liver BRL-3A cells. Prior to the cellular studies, transmission electron microscopy (TEM), dynamic light scattering (DLS), and X ray diffraction (XRD) were used to characterize SiO2 NPs, which proved the amorphous nature of SiO2 NPs with TEM diameter of 19.8±2.7nm. Further studies proved that exposure to SiO2 NPs dose-dependently induced cytotoxicity as revealed by cell counting kit (CCK-8) and lactate dehydrogenase (LDH) assays, with more severe cytotoxicity in HL-7702 cells than BRL-3A cells. Reactive oxygen species (ROS) and glutathione (GSH) assays showed elevated oxidative stress in both cells. Morphological studies by microscopic observation, Hochest 33258 and AO/EB staining indicated significant apoptotic changes after the cells being exposed to SiO2 NPs. Further studies by western blot indicated that SiO2 NPs exposure to both cells up-regulated p53, Bax and cleaved caspase-3 expression and down-regulated Bcl-2 and caspase-3 levels. Activated caspase-3 activity detected by colorimetric assay kit and caspase-3/7 activity detected by fluorescent real-time detection kit were significantly increased by SiO2 NPs exposure. In addition, antioxidant vitamin C significantly attenuated SiO2 NPs-induced caspase-3 activation, which indicated that SiO2 NPs-induced oxidative stress was involved in the process of HL-7702 and BRL-3A cell apoptosis. Taken together, these results suggested that SiO2 NPs-induced cytotoxicity in HL-7702 and BRL-3A cells was through oxidative stress mediated and p53, caspase-3 and Bax/Bcl-2 dependent pathway and HL-7702 cells were more sensitive to SiO2 NPs-induced cytotoxicity than BRL-3A cells.

Selected novel 5'-amino-2'-hydroxy-1, 3-diaryl-2-propen-1-ones arrest cell cycle of HCT-116 in G0/G1 phase

A series of 5'-amino-2'-hydroxy-1,3-diaryl-2-propen-1-ones (AC1-AC15) were synthesized by Claisen-Schmidt condensation of 5'-acetamido-2'-hydroxy acetophenone with various substituted aromatic aldehydes. The synthesized compounds were characterized by FTIR, ¹H NMR and mass spectrometry and evaluated for their selective cytotoxicity using MTT assay on two cancer cell lines namely breast cancer cell line (MCF-7), colon cancer cell line (HCT-116) and one normal kidney epithelial cell line (Vero). Among the tested compounds, AC-10 showed maximum cytotoxic effect on MCF-7 cell line with IC₅₀ value 74.7 ± 3.5 µM. On HCT-116 cells, AC-13 exhibited maximum cytotoxicity with IC₅₀ value 42.1 ± 4.0 µM followed by AC-14 and AC-10 with IC₅₀ values 62 ± 2.3 µM and 95.4 ± 1.7 µM respectively. All tested compounds were found to be safe on Vero cell line with IC₅₀ value more than 200 µM. Based on their highest efficacy on HCT-116, AC-10, AC-13 and AC-14 were selected for mechanistic study on this cell line by evaluating changes nucleomorphological characteristics using acridine orange-ethidium bromide (AOEB) dual stain and by analyzing cell cycle with flow cytometry using propidium iodide stain. In AOEB staining, all three tested compounds showed significant (p < 0.05) increase in percentage apoptotic nuclei compared to control cells, with highest increase in apoptotic nuclei by AC-13 treatment (31 %). Flow cytometric studies showed cell cycle arrest by AC-10 and AC-14 treatment in G₀/G₁ phase and by AC-13 in G₀/G₁ and G₂/M phase. The study reflected the potential of AC-10, AC-13 and AC-14 to be the lead molecules for further optimization.

Metal-free ring expansion of indoles with nitroalkenes: a simple, modular approach to 3-substituted 2-quinolones

3-Substituted 2-quinolones are obtained via a novel metal-free transannulation reaction of 2-nitroolefins with 2-substituted indoles in polyphosphoric acid.

Synthesis of a novel series of 2,3,4-trisubstituted oxazolidines designed by isosteric replacement or rigidification of the structure and cytotoxic evaluation

Rigidification of the structure of 2,3,4-trisubstituted oxazolidines enhances the activity against LNCaP cells without affecting normal cell proliferation.

D-pinitol promotes apoptosis in MCF-7 cells via induction of p53 and Bax and inhibition of Bcl-2 and NF-κB

Development of drugs from natural products has been undergoing a gradual evoluation. Many plant derived compounds have excellent therapeutic potential against various human ailments. They are important sources especially for anticancer agents. A number of promising new agents are in clinical development based on their selective molecular targets in the field of oncology. D-pinitol is a naturally occurring compound derived from soy which has significant pharmacological activitites. Therefore we selected D-pinitol in order to evaluate apoptotic potential in the MCF-7 cell line. Human breast cancer cells were treated with different concentrations of D-pinitol and cytotoxicity was measured by MTT and LDH assays. The mechanism of apoptosis was studied with reference to expression of p53, Bcl-2, Bax and NF-kB proteins. The results revealed that D-pinitol significantly inhibited the proliferation of MCF-7 cells in a concentration-dependent manner, while upregulating the expression of p53, Bax and down regulating Bcl-2 and NF-kB. Thus the results obtained in this study clearly vindicated that D-pinitol induces apotosis in MCF-7 cells through regulation of proteins of pro- and anti-apoptotic cascades.

Metal-free transannulation reaction of indoles with nitrostyrenes: a simple practical synthesis of 3-substituted 2-quinolones

3-Substituted 2-quinolones are obtained via a novel, metal-free transannulation reaction of 2-substituted indoles with 2-nitroalkenes in polyphosphoric acid. The reaction can be used in conjunction with the Fisher indole synthesis offering a practical three-component heteroannulation methodology to produce 2-quinolones from arylhydrazines, 2-nitroalkenes and acetophenone.

Trimethoxy-benzaldehyde levofloxacin hydrazone inducing the growth arrest and apoptosis of human hepatocarcinoma cells

Background

In order to search for new structural modification strategies on fluoroquinolones, we have designed and synthesized a series of fluoroquinolone derivatives by linking various hydrazine compounds to the C-3 carboxyl group of levofloxacin and assessed their anticancer activities. Several novel levofloxacin derivatives displayed potent cytotoxicity against the tested cancer cell lines in vitro. In the present study, we investigated the effect of 1-Cyclopropyl-6-fluoro-4-oxo-7- piperazin-1, 4-dihydro- quinoline- 3-carboxylic acid benzo [1,3] dioxol-5- ylmethylene- hydrazide (QNT11) on the apoptosis of human hepatocarcinoma cells in vitro.

Methods

The inhibition effects of QNT11 on cell proliferation were examined by MTT assay. Cell apoptosis was determined by TUNEL and DNA agarose gel electrophoresis method. The topoisomerase ΙΙ activity was measured by agarose gel electrophoresis using Plasmid pBR322 DNA as the substrate. Cell cycle progression was analyzed using flow cytometry in conjunction with ethanol fixation and propidium iodide staining. Mitochondrial membrane potential (△ψm) was measured by high content screening image system. The caspase-9, caspase-8, caspase-3, Bcl-2, Bax, CDK1, Cyclin B1and cytochrome c protein expressions were detected by Western blot analysis.

Results

QNT11 showed selective cytotoxicity against Hep3B, SMMC-7721, MCF-7 and HCT-8 cell lines with IC₅₀ values of 2.21 μM, 2.38 μM, 3.17 μM and 2.79 μM, respectively. In contrast, QNT11 had weak cytotoxicity against mouse bone marrow mesenchymal stem cells (BMSCs) with IC₅₀ value of 7.46 μM. Treatment of Hep3B cells with different concentrations of QNT11 increased the percentage of the apoptosis cells significantly, and agarose gel electrophoresis revealed the ladder DNA bands typical of apoptotic cells, with a decrease in the mitochondrial membrane potential. Compared to the control group, QNT11 could influence the DNA topoisomerase IIactivity and inhibit the religation of DNA strands, thus keeping the DNA in fragments. There was a significant increase of cytochrome c in the cytosol after 24 h of treatment with QNT11 and a decrease in the mitochondrial compartment. Observed changes in cell cycle distribution by QNT11 treated might be caused by insufficient preparation for G₂/M transition. In addition, QNT11 increased the protein expression of Bax, caspase-9, caspase-8, caspase-3, as well as the cleaved activated forms of caspase-9, caspase-8 and caspase-3 significantly, whereas the expression of Bcl-2 decreased.

Conclusions

Our results showed that QNT11 as a fluoroquinolone derivative exerted potent and selectively anticancer activity through the mechanism of eukaryotic topoisomerase II poisoning. The growth inhibition was in large part mediated via apoptosis-associated mitochondrial dysfunction and regulation of Bcl-2 signaling pathways.