Novel microtubule-targeted agent 6-chloro-4-(methoxyphenyl) coumarin induces G2-M arrest and apoptosis in HeLa cells

Switching of the Polarity-Sensitive Aggregation Pattern of a Thiosemicarbazone-Based Anticancer Luminophore and Its Involvement in Cellular Apoptosis of the Human Lung Cancer Cell Line

Elucidation of the photophysical and biochemical properties of small molecules can facilitate their applications as prospective therapeutic imaging (theragnostic) agents. Herein, we demonstrate the luminescence behavior of a strategically designed potential therapeutic thiosemicarbazone derivative, (E)-1-(4-(diethylamino)-2-hydroxybenzylidene)-4,4-dimethylthiosemicarbazide (DAHTS), accompanied by the illustration of its solvation and solvation dynamics using spectroscopic techniques and exploring its promising antitumor activities by adopting the necessary biochemical assays. Solvent-dependent photophysical properties, namely UV-vis absorption, fluorescence emission, and excitation profiles, concentration-dependent studies, and time-resolved fluorescence decays, serve as footprints to explain the existence of DAHTS monomers, its excited-state intramolecular proton transfer (ESIPT) product, and dimeric and aggregated forms. The emission intensity progressively intensifies with increasing polarity and proticity of the solvents up to MeOH, but in water, a sudden dip is seen. Solvent polarity and H-bonding modulate the fluorescence behavior of the primary emission peak and significantly influence the formation of the dimer and DAHTS aggregates. The designed luminophore (DAHTS) exhibits significant antiproliferative activity against the human lung cancer (A549) cell lines with inhibitory concentrations (IC₅₀) of 16.88 and 11.92 μM for 24 and 48 h, respectively. DAHTS effectively reduces the cell viability and induces cytotoxicity with extensive morphological changes in A549 cells in the form of spikes when compared to the normal HEK cell lines. More importantly, it increases the p53 expression at the mRNA level that consolidates its potential therapeutic activity. The effect of DAHTS on apoptotic pathways against the A549 cell line has been investigated to determine its probable mechanism of cell death. Thus, the all-inclusive understanding of the photophysical properties and the necessary biochemical assays put forward important steps toward tailoring the thiosemicarbazone core structure for favorable cancer theragnostic applications in academic and pharmaceutical research.

Synthesis and Antiproliferative Effect of Halogenated Coumarin Derivatives

A series of 6- and 6,8-halocoumarin derivatives have been investigated as potential antiproliferative compounds against a panel of tumor and normal cell lines. Cytotoxic effects were determined by the MTT method. To investigate the potential molecular mechanism involved in the cytotoxic effect, apoptosis assay, cell cycle analysis, reactive oxygen species (ROS), and reduced glutathione analysis were performed. Among the screened compounds, coumarins 6,8-dibromo-2-oxo-2H-chromene-3-carbonitrile 2h and 6,8-diiodo-2-oxo-2H-chromene-3-carbonitrile 2k exhibited the most antiproliferative effect in thyroid cancer-derived cells TPC-1. The apoptosis assay showed that both 2h and 2k induced apoptosis in TPC-1 thyroid cancer cells. According to these experiments, both coumarins induced a slight increase in TPC-1 cells in the G2/M phase and a decrease in the S phase. A significant increase in ROS levels was observed in TPC-1 treated with diiodocoumarin 2k, while the dibromocoumarin 2h induced a decrease in ROS in a dose and time-dependent manner.

Modern metal-catalyzed and organocatalytic methods for synthesis of coumarin derivatives: a review

Coumarin is an important pharmaceutical structural motif, abundantly found in numerous commonly used drugs. Compounds containing this core show a broad spectrum of medicinal properties and biological activities. The increasing importance and wide usages of coumarin derivatives have drawn attention to its synthetic methods, among which metal-catalyzed and organocatalytic methods have proved the most effective. Several metal-catalyzed and/or organocatalytic synthetic strategies for coumarin have been investigated and reported in recent decades. This review focuses on more recent reports on catalysis methods for synthesizing coumarin and coumarin-like structures (including light-mediated methods and nano-catalysts), exploring the mechanistic aspects, simplicity, efficiency, repeatability, and other advantages and disadvantages of these methods.

Angelol-A exerts anti-metastatic and anti-angiogenic effects on human cervical carcinoma cells by modulating the phosphorylated-ERK/miR-29a-3p that targets the MMP2/VEGFA axis

AIMS

Angelol-A (Ang-A), a kind of coumarins, is isolated from the roots of Angelica pubescens f. biserrata. However, AA exerts antitumor effects and molecular mechanism on cervical cancer cells is unknown.

MAIN METHODS

Cell viability was determined using the MTT assay, and the cell cycle phase was assessed by PI staining with flow cytometry. Ang-A-treated cells with/without Antago-miR-29a-3p (miR-29a-3p inhibitor) or U0126 (MEK inhibitor) were assessed for the expression of miR-29a-3p, in vitro migration/invasion, and angiogenesis using qRT-PCR, a chemotaxis assay, and tube formation assay, respectively. The expression of mitogen-activated protein kinases/MMP2/MMP9/VEGFA was determined by western blot analysis with applicable antibodies.

KEY FINDINGS

Ang-A significantly inhibited MMP2 and VEGFA expression, cell migration, and invasive motility in human cervical cancer cells. Conditioned medium inhibited tube formation in HUVECs. Ang-A principally inhibited invasive motility and angiogenesis by upregulating the expression of miR-29a-3p that targets the VEGFA-3' UTR. The role of miR-29a-3p was confirmed using Antago-miR-29a-3p, which reversed the Ang-A-inhibited expression of MMP2 and VEGFA, invasive motility, and angiogenesis in human cervical cancer cells. The ERK pathway was implicated in mediating the metastatic and angiogenic action of Ang-A. Combined treatment with Ang-A treated and U0126 exerted a synergistic inhibitory effect on the expression of MMP2 and VEGFA and the metastatic and angiogenic properties of human cervical cancer cells.

SIGNIFICANCE

These findings are the first to indicate that in human cervical cancer cells, Ang-A exerts anti-metastatic and anti-angiogenic effects via targeting the miR-29a-3p/MMP2/VEGFA axis, mediated through the ERK pathway.

Synthesis of substituted 1,2-dihydroisoquinolines via Ni(ii) and Cu(i)/Ag(i) catalyzed double nucleophilic addition of arylamines to ortho-alkynyl donor-acceptor cyclopropanes (o-ADACs)

A concise approach for the synthesis of substituted 1,2-dihydroisoquinolines via double nucleophilic addition of primary arylamines to ortho-alkynyl donor-acceptor cyclopropanes (o-ADACs) in the presence of a catalytic Ni(ClO₄)₂·6H₂O and CuI/AgOTf system has been developed. Further applying this protocol, some of the derived malonates were converted into the corresponding monoesters under Krapcho decarboxylation reaction conditions. Thereafter, these esters were transformed into the respective acids and alcohols. In addition, multifunctionalized 4-(2,2,2-trifluoroacetyl) 1,2-dihydroisoquinolines were also obtained with excess TFAA.

Silver-catalyzed tandem cycloisomerization/hydroarylation reactions and mechanistic investigations for an efficient access to 1,2-dihydroisoquinolines

A combination of AcOH and Ag catalyst induced an efficient tandem reaction to form 1,2-dihydroisoquinoline derivatives. Highly functionalized multiheterocyclic scaffolds are accessible straightforwardly using readily available starting materials.

Allelochemical Activity of Eugenol-Derived Coumarins on Lactuca sativa L

Coumarins are widely distributed substances in plant species that promote phytotoxic effects, allowing them to be exploited as herbicides less harmful to the environment, since many invasive species have demonstrated resistance to commercially available products. The derived coumarins used in this study had not been tested in plant models and their effect on plants was unknown. The objective of this study was to evaluate the phytotoxic action of these coumarins in bioassays with Lactuca sativa L., in order to select the most responsive substance whose toxicity was best elucidated by chromosomal complement and enzymatic antioxidant metabolism studies. From the phytotoxicity assays, coumarin 8-methoxy-2-oxo-6-(prop-2-en-1-yl)-2H-chromene-3-carboxylic acid (A1), reported here for the first time, was selected as the most responsive and caused a reduction in the following parameters: number of normal seedlings, fresh biomass, root length and shoot length. Subsequent studies demonstrated that this coumarin is cytogenotoxic due to damage caused to the cell cycle and the occurrence of chromosomal abnormalities. However, it did not interfere with antioxidant enzyme activity and did not cause lipid peroxidation. The changes caused by coumarin A1 described herein can contribute to better understanding the allelochemical actions of coumarins and the potential use of these substances in the production of natural herbicides.

3-(3-Methoxyphenyl)-6-(3-amino-4-methoxyphenyl)-7H-[1,2,4] triazolo [3,4-b][1,3,4] thiadiazine, a novel tubulin inhibitor, evokes G2/M cell cycle arrest and apoptosis in SGC-7901 and HeLa cells

Gastric cancer and cervical cancer are two major malignant tumors that threaten human health. The novel chemotherapeutic drugs are needed urgently to treat gastric cancer and cervical cancer with high anticancer activity and metabolic stability. Previously we have reported the synthesis, characterization and identification of a novel combretastatin A-4 analog, 3-(3-methoxyphenyl)-6-(3-amino-4- methoxyphenyl) -7H-[1,2,4]triazolo[3,4-b][1,3,4] thiadiazine (XSD-7). In this study, we sought to investigate its anticancer mechanisms in a human gastric cancer cell line (SGC-7901 cells) and human cervical carcinoma cell line (HeLa cells). The 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide assay showed that XSD-7 induced cytotoxicity in SGC-7901 and HeLa cells with inhibitory concentration 50 values of 0.11 ± 0.03 and 0.12 ± 0.05 µM, respectively. Immunofluorescence studies proved that XSD-7 inhibited microtubule polymerization during cell division in SGC-7901 and HeLa cells. Then, these cells were arrested at G2/M cell cycle and subsequently progressed into apoptosis. In further study, mitochondrial membrane potential analysis and Western blot analysis demonstrated that XSD-7 treatment-induced SGC-7901 cell apoptosis via both the mitochondria-mediated pathway and the death receptor-mediated pathway. In contrast, XSD-7 induced apoptosis in HeLa cells mainly via the mitochondria-mediated pathway. Hence, our data indicate that XSD-7 exerted antiproliferative activity by disrupting microtubule dynamics, leading to cell cycle arrest, and eventually inducing cell apoptosis. XSD-7 with novel structure has the potential to be developed for therapeutic treatment of gastric cancer and cervical cancer.

Enhanced uptake, high selective and microtubule disrupting activity of carbohydrate fused pyrano-pyranones derived from natural coumarins attributes to its anti-malarial potential

Background

Malaria is one of the deadliest infectious diseases caused by protozoan parasite of Plasmodium spp. Increasing resistance to anti-malarials has become global threat in control of the disease and demands for novel anti-malarial interventions. Naturally-occurring coumarins, which belong to a class of benzo-α-pyrones, found in higher plants and some essential oils, exhibit therapeutic potential against various diseases. However, their limited uptake and non-specificity has restricted their wide spread use as potential drug candidates.

Methods

Two series of carbohydrate fused pyrano[3,2-c]pyranone carbohybrids which were synthesized by combination of 2-C-formyl galactal and 2-C-formyl glucal, with various freshly prepared 4-hydroxycoumarins were screened against Plasmodium falciparum. The anti-malarial activity of these carbohybrids was determined by growth inhibition assay on P. falciparum 3D7 strain using SYBR green based fluorescence assay. Haemolytic activity of carbohybrid 12, which showed maximal anti-malarial activity, was determined by haemocompatibility assay. The uptake of the carbohybrid 12 by parasitized erythrocytes was determined using confocal microscopy. Growth progression assays were performed to determine the stage specific effect of carbohybrid 12 treatment on Pf3D7. In silico studies were conducted to explore the mechanism of action of carbohybrid 12 on parasite microtubule dynamics. These findings were further validated by immunofluorescence assay and drug combination assay.

Results

2-C-formyl galactal fused pyrano[3,2-c]pyranone carbohybrid 12 exhibited maximum growth inhibitory potential against Plasmodium with IC₅₀ value of 5.861 µM and no toxicity on HepG2 cells as well as no haemolysis of erythrocytes. An enhanced uptake of this carbohybrid compound was observed by parasitized erythrocytes as compared to uninfected erythrocytes. Further study revealed that carbohybrid 12 arrests the growth of parasite at trophozoite and schizonts stage during course of progression through asexual blood stages. Mechanistically, it was shown that the carbohybrid 12 binds to α,β-heterodimer of tubulin and affects microtubule dynamics.

Conclusion

These findings show carbohydrate group fusion to 4-hydroxycoumarin precursor resulted in pyrano-pyranones derivatives with better solubility, enhanced uptake and improved selectivity. This data confirms that, carbohydrate fused pyrano[3,2-c]pyranones carbohybrids are effective candidates for anti-malarial interventions against P. falciparum.

Novel coumarin-6-sulfonamides as apoptotic anti-proliferative agents: synthesis, in vitro biological evaluation, and QSAR studies

Herein, we report the synthesis of different novel sets of coumarin-6-sulfonamide derivatives bearing different functionalities (4a, b, 8a-d, 11a-d, 13a, b, and 15a-c), and in vitro evaluation of their growth inhibitory activity towards the proliferation of three cancer cell lines; HepG2 (hepatocellular carcinoma), MCF-7 (breast cancer), and Caco-2 (colon cancer). HepG2 cells were the most sensitive cells to the influence of the target coumarins. Compounds 13a and 15a emerged as the most active members against HepG2 cells (IC50 = 3.48 ± 0.28 and 5.03 ± 0.39 µM, respectively). Compounds 13a and 15a were able to induce apoptosis in HepG2 cells, as assured by the upregulation of the Bax and downregulation of the Bcl-2, besides boosting caspase-3 levels. Besides, compound 13a induced a significant increase in the percentage of cells at Pre-G1 by 6.4-folds, with concurrent significant arrest in the G2-M phase by 5.4-folds compared to control. Also, 13a displayed significant increase in the percentage of annexin V-FITC positive apoptotic cells from 1.75-13.76%. Moreover, QSAR models were established to explore the structural requirements controlling the anti-proliferative activities.

The Effect of Millisecond Pulsed Electric Fields (msPEF) on Intracellular Drug Transport with Negatively Charged Large Nanocarriers Made of Solid Lipid Nanoparticles (SLN): In Vitro Study

Drug delivery technology is still a dynamically developing field of medicine. The main direction in nanotechnology research (nanocarriers, nanovehicles, etc.) is efficient drug delivery to target cells with simultaneous drug reduction concentration. However, nanotechnology trends in reducing the carrier sizes to several nanometers limit the volume of the loaded substance and may pose a danger of uncontrolled access into the cells. On the other hand, nanoparticles larger than 200 nm in diameter have difficulties to undergo rapid diffusional transport through cell membranes. The main advantage of large nanoparticles is higher drug encapsulation efficiency and the ability to deliver a wider array of drugs. Our present study contributes a new approach with large Tween 80 solid lipid nanoparticles SLN (i.e., hydrodynamic GM-SLN-glycerol monostearate, GM, as the lipid and ATO5-SLNs-glyceryl palmitostearate, ATO5, as the lipid) with diameters DH of 379.4 nm and 547 nm, respectively. They are used as drug carriers alone and in combination with electroporation (EP) induced by millisecond pulsed electric fields. We evaluate if EP can support the transport of large nanocarriers into cells. The study was performed with two cell lines: human colon adenocarcinoma LoVo and hamster ovarian fibroblastoid CHO-K1 with coumarin 6 (C6) as a fluorescent marker for encapsulation. The biological safety of the potential treatment procedure was evaluated with cell viability after their exposure to nanoparticles and EP. The EP efficacy was evaluated by FACS method. The impact on intracellular structure organization of cytoskeleton was visualized by CLSM method with alpha-actin and beta-tubulin. The obtained results indicate low cytotoxicity of both carrier types, free and loaded with C6. The evaluation of cytoskeleton proteins indicated no intracellular structure damage. The intracellular uptake and accumulation show that SLNs do not support transport of C6 coumarin. Only application of electroporation improved the transport of encapsulated and free C6 into both treated cell lines.

Triazole tethered C5-curcuminoid-coumarin based molecular hybrids as novel antitubulin agents: Design, synthesis, biological investigation and docking studies

Keeping in view the confines allied with presently accessible antitumor agents and success of C5-curcuminoid based bifunctional hybrids as novel antitubulin agnets, molecular hybrids of C5-curcuminoid and coumarin tethered by triazole ring have been synthesized and investigated for in-vitro cytotoxicity against THP-1, COLO-205, HCT-116 and PC-3 human tumor cell lines. The results revealed that the compounds A-2 to A-9, B-2, B-3, B-7 showed significant cytotoxic potential against THP-1, COLO-205 and HCT-116 cell lines, while the PC-3 cell line among these was found to be almost resistant. Structure activity relationship revealed that the nature of Ring X and the length of carbon-bridge (n) connecting triazole ring with coumarin moiety considerably influence the activity. Methoxy substituted phenyl ring as Ring X and two carbon-bridges were found to be the ideal structural features. The most potent compounds (A-2, A-3 and A-7) were further tested for tubulin polymerization inhibition. Compound A-2 was found to significantly inhibit the tubulin polymerization (IC50 = 0.82 μM in THP-1 tumor cells). The significant cytotoxicity and tubulin polymerization inhibition by A-2 was further rationalized by docking studies where it was docked at the curcumin binding site of tubulin.

Design, synthesis and anticancer activities of novel otobain derivatives

Twenty novel racemic otobain derivatives have been designed and synthesized, among which compound 27g exhibited the most potent anticancer activity.

Physalin B not only inhibits the ubiquitin-proteasome pathway but also induces incomplete autophagic response in human colon cancer cells in vitro

AIM

To investigate the effects of physalin B insolated from Physalis divericata on human colon cancer cells in vitro and its anticancer mechanisms.

METHODS

Human HCT116 colon cancer cell line was tested. Cell viability and apoptosis were detected, and relevant proteins were measured using Western blot analyses. Autophagosomes were observed in stable GFP-LC3 HCT116 cells. Localization of autophagosomes and lysosomes was evaluated in GFP-LC3/RFP-LAMP1-co-transfected cells. Microtubules and F-actin microfilaments were observed with confocal microscope. Mitochondrial ROS (mito-ROS) was detected with flow cytometry in the cells stained with MitoSox dye.

RESULTS

Physalin B inhibited the viability of HCT116 cells with an IC50 value of 1.35 μmol/L. Treatment of the cells with physalin B (2.5-10 μmol/L) induced apoptosis and the cleavage of PARP and caspase-3. Meanwhile, physalin B treatment induced autophagosome formation, and accumulation of LC3-II and p62, but decreased Beclin 1 protein level. Marked changes of microtubules and F-actin microfilaments were observed in physalin B-treated cells, which led to the blockage of co-localization of autophagosomes and lysosomes. Physalin B treatment dose-dependently increased the phosphorylation of p38, ERK and JNK in the cells, whereas the p38 inhibitor SB202190, ERK inhibitor U0126 or JNK inhibitor SP600125 could partially reduce physalin B-induced PARP cleavage and p62 accumulation. Moreover, physalin B treatment dose-dependently increased mito-ROS production in the cells, whereas the ROS scavenger NAC could reverse physalin B-induced effects, including incomplete autophagic response, accumulation of ubiquitinated proteins, changes of microtubules and F-actin, activation of p38, ERK and JNK, as well as cell death and apoptosis.

CONCLUSION

Physalin B induces mito-ROS, which not only inhibits the ubiquitin-proteasome pathway but also induces incomplete autophagic response in HCT116 cells in vitro.

Identification of DW532 as a novel anti-tumor agent targeting both kinases and tubulin

AIM

7,8-Dihydroxy-4-(3-hydroxy-4-methoxyphenyl)-2H-chromen-2-one (DW532) is one of simplified analogues of hematoxylin that has shown broad-spectrum inhibition on tyrosine kinases and in vitro anti-cancer activities. The aim of this study was to identify DW532 as a agent targeting both kinases and tubulin, and to investigate its anti-cancer and anti-angiogenesis activities.

METHODS

In vitro tyrosine kinases activity was examined with ELISA, and tyrosine kinases activity in cells was evaluated with Western blot analysis. Tubulin turbidity assay, surface plasmon resonance and immunofluorescence technique were used to characterize the tubulin inhibitory activity. Cell proliferation was examined with SRB assay, and cell apoptosis and cell cycle distribution were analyzed with Annexin-V/PI staining and flow cytometry. Tube formation, aortic ring and chick chorioallantoic membrane assays were used to evaluate the anti-angiogenesis efficacy.

RESULTS

DW532 inhibited EGFR and VEGFR2 in vitro kinase activity (the IC50 values were 4.9 and 5.5 μmol/L, respectively), and suppressed their downstream signaling. DW532 dose-dependently inhibited tubulin polymerization via direct binding to tubulin, thus disrupting the mitotic spindle assembly and leading to abnormal cell division. In a panel of human cancer cells, DW532 (1 and 10 μmol/L) induced G2/M phase arrest and cell apoptosis, which subsequently resulted in cytotoxicity. Knockdown of BubR1 or Mps1, the two core proteins of the spindle assembly checkpoint dramatically decreased DW532-induced cell cycle arrest in MDA-MB-468 cells. Moreover, treatment with DW532 potently and dose-dependently suppressed angiogenesis in vitro and in vivo.

CONCLUSION

DW532 is a dual inhibitor against tubulin and tyrosine kinases, and deserves further development as a novel anti-cancer agent.

Involvement of transcription factor XBP1s in the resistance of HDAC6 inhibitor Tubastatin A to superoxidation via acetylation-mediated proteasomal degradation

HDAC6 is a major cytoplasmic deacetylase. XBP1s is a basic-region leucine zipper (bZIP) transcriptional factor. Despite their mutual involvement in the anti-oxidative process, there are no reports about their inter-protein interactions so far. Here we identified a direct link between HDAC6 inhibition and XBP1s transcription activity in anti-oxidative damage. We showed that the specific HDAC6 inhibitor Tubastatin A could up-regulate XBP1s transcriptional activity, thereby increasing anti-oxidative genes expression. Moreover, knock down of XBP1s could significantly abolish the cell growth protection afforded by Tubastatin A. We hypothesize that Tubastatin A acts to increase XBP1s protein levels that are dependent on its HDAC6 deacetylase inhibition via a mechanism involving acetylation-mediated proteasomal degradation, providing novel mechanistic insight into the anti-oxidative effects of HDAC6 inhibition.

Establishing a High-content Analysis Method for Tubulin Polymerization to Evaluate Both the Stabilizing and Destabilizing Activities of Compounds

Microtubules are important components of the cellular cytoskeleton that play roles in various cellular processes such as vesicular transport and spindle formation during mitosis. They are formed by an ordered organization of α-tubulin and β-tubulin hetero-polymers. Altering microtubule polymerization has been known to be the mechanism of action for a number of therapeutically important drugs including taxanes and epothilones. Traditional cell-based assays for tubulin-interacting compounds rely on their indirect effects on cell cycle and/or cell proliferation. Direct monitoring of compound effects on microtubules is required to dissect detailed mechanisms of action in a cellular setting. Here we report a high-content assay platform to monitor tubulin polymerization status by directly measuring the acute effects of drug candidates on the cellular tubulin network with the capability to dissect the mechanisms of action. This high-content analysis distinguishes in a quantitative manner between compounds that act as tubulin stabilizers versus those that are tubulin destabilizers. In addition, using a multiplex approach, we expanded this analysis to simultaneously monitor physiological cellular responses and associated cellular phenotypes.