Discovery of novel quinoline-based analogues of combretastatin A-4 as tubulin polymerisation inhibitors with apoptosis inducing activity and potent anticancer effect

A new series of quinoline derivatives of combretastatin A-4 have been designed, synthesised and demonstrated as tubulin polymerisation inhibitors. These novel compounds showed significant antiproliferative activities, among them, 12c exhibited the most potent inhibitory activity against different cancer cell lines (MCF-7, HL-60, HCT-116 and HeLa) with IC₅₀ ranging from 0.010 to 0.042 µM, and with selectivity profile against MCF-10A non-cancer cells. Further mechanistic studies suggest that 12c can inhibit tubulin polymerisation and cell migration, leading to G₂/M phase arrest. Besides, 12c induces apoptosis via a mitochondrial-dependant apoptosis pathway and caused reactive oxygen stress generation in MCF-7 cells. These results provide guidance for further rational development of potent tubulin polymerisation inhibitors for the treatment of cancer.

Highlights

• A novel series of quinoline derivatives of combretastatin A-4 have been designed and synthesised.
• Compound 12c showed significant antiproliferative activities against different cancer cell lines.
• Compound 12c effectively inhibited tubulin polymerisation and competed with [³H] colchicine in binding to tubulin.
• Compound 12c arrested the cell cycle at G₂/M phase, effectively inducing apoptosis and inhibition of cell migration.

     

Development of a novel,multifunctional, membrane-interactive pyridinium salt with potent anticancer activity

The synthesis and biological evaluation of a novel pyridinium salt is reported. Initial membrane interaction with isolated phospholipid monolayers was obtained with the pyridinium salt, and two neutral analogues for comparison, and the anticancer effects of the best compound established using a cytotoxicity screening assay against glioma cells using both an established cell line and three short-term cell cultures—one of which has been largely resistant to all chemotherapeutic drugs tested to date. The results indicate that the pyridinium salt exhibits potent anticancer activity (EC₅₀s = 9.8–312.5 μM) on all cell types, including the resistant one, for a continuous treatment of 72 h. Microscopic examination of the treated cells using a trypan blue exclusion assay showed membrane lysis had occurred. Therefore, this letter highlights the potential for a new class of pyridinium salt to be developed as a much needed alternative treatment for glioma chemotherapy.     

Ethaselen: a potent mammalian thioredoxin reductase 1 inhibitor and novel organoselenium anticancer agent

Mammalian thioredoxin reductase 1 (TrxR1) is considered to be an important anticancer drug target and to be involved in both carcinogenesis and cancer progression. Here, we report that ethaselen, a novel organoselenium compound with anticancer activity, specifically binds to the unique selenocysteine-cysteine redox pair in the C-terminal active site of mammalian TrxR1. Ethaselen was found to be a potent inhibitor rather than an efficient substrate of mammalian TrxR1. It effectively inhibits wild-type mammalian TrxR1 at submicromolar concentrations with an initial mixed-type inhibition pattern. By using recombinant human TrxR1 variants and human glutathione reductase, we prove that ethaselen specifically targets the C-terminal but not the N-terminal active site of mammalian TrxR1. In A549 human lung cancer cells, ethaselen significantly suppresses cell viability in parallel with direct inhibition of TrxR1 activity. It does not, however, alter either the disulfide-reduction capability of thioredoxin or the activity of glutathione reductase. As a downstream effect of TrxR1 inactivation, ethaselen causes a dose-dependent thioredoxin oxidation and enhances the levels of cellular reactive oxygen species in A549 cells. Thus, we propose ethaselen as the first selenium-containing inhibitor of mammalian TrxR1 and provide evidence that selenium compounds can act as anticancer agents based on mammalian TrxR1 inhibition.     

Bombesin analogs containing alpha-amino-isobutyric acid with potent anticancer activity.

Six octapeptide bombesin (BN) analogs were synthesized by substituting alpha-aminoisobutyric acid (Aib), in place of Ala9 or Gly11, or both, in the [D-Phe6, desMet14]-BN (6-14) sequence: D-Phe6-Gln7-Trp8-Ala9-Val10-Gly11-His12-Leu13-NH2 (P0). Additionally, Leu13 was replaced with isoleucine in two analogs and one of the analogs was butanoylated at the N-terminus. The antiproliferative activity of the analogs was tested in vitro on human pancreatic (MiaPaCa-2) and colon cancer (SW620, HT29 and PTC) cell lines using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The analogs demonstrated anticancer activity in the above cell lines at concentrations ranging from 0.01 nM to 1 microM. One of the analogs, P6, was evaluated for in vivo tumor regression in a xenograft model of human primary colon cancer in athymic nude mice and was found to cause significant reduction in tumor volume. NMR and molecular dynamics (MD) simulation studies for this analog revealed the presence of a mixed 3(10)/alpha-helical structure. This study demonstrates that the designed BN analogs retain their anticancer activity after the incorporation of the constrained amino acid, Aib, and are potential molecules for future use in cancer therapy and drug targeting.     

A novel tetrazole analogue of resveratrol is a potent anticancer agent

A series of novel tetrazole analogues of resveratrol were synthesized and evaluated for their anti-leukemic activity against an extensive panel of human cancer cell lines and against the MV4-11 AML cell line. These molecules were designed as drug-like derivatives of the resveratrol analogue DMU-212 and its cyano derivatives. Four compounds 8g, 8h, 10a and 10b exhibited LD₅₀ values of 4.60?µM, 0.02?µM, 1.46?µM, and 1.08?µM, respectively, against MV4-11 leukemia cells. The most potent compounds, 8h and 10b, were also found to be active against an extensive panel of human hematological and solid tumor cell lines; compound 8h was the most potent compound with GI₅₀ values <10?nM against more than 90% of the human cancer cell lines in the 60-cell panel. Analogues 8g, 8h, 10a and 10b were also tested for their ability to inhibit the polymerization of tubulin, and compound 8h was found to be the most potent analogue. Molecular modeling studies demonstrated that 8h binds to the colchicine binding site on tubulin. Thus, compound 8h is considered to be a lead druglike molecule from this tetrazole series of compounds.     

Substance P analogs containing alpha,alpha-dialkylated amino acids with potent anticancer activity.

Six analogs (peptides 1-6) of the potent substance P (SP) derivative known as 'Antagonist D' were synthesized by substituting constrained amino acids Aib or Acp (cycloleucine, 1-amino cyclopentane carboxylic acid) at different positions in the Antagonist D sequence: D-Arg(1)-Pro(2)-Lys(3)-Pro(4)-D-Phe(5)-Gln(6)-D-Trp(7)-Phe(8)-D-Trp(9)-Leu(10)-Leu(11)-NH(2). In the preliminary in vitro antiproliferative screening of the analogs on different human cancer cell lines by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, peptide 1 was found to be the most active. Further, peptide 1 was butanoylated (analog 5) or octanoylated (analog 6) at the N-terminus. SP analogs 1, 5, and 6 were evaluated in vivo in a xenograft model of human primary colon tumor (PTC) cell line in athymic nude mice and were found to cause tumor regression. This study investigates if the use of the constrained amino acids Aib and Acp in the designed SP analogs can retain the in vitro and in vivo anticancer activities, which could be useful in cancer therapy and drug targeting. Further, the strategy of incorporation of Aib or Acp in biologically active peptides can be exploited in determining the receptor-bound conformation and in transforming these bioactive peptides into pharmacologically useful drugs.     

Synthesis and activity of a cyclo-heptapeptide containing Lys-Gly-Asp-sequence as a novel anti-platelet agent

Linear hepta-peptide Cys-Lys-Gly-Asp-Trp-Asp-Cys was synthesized first and then disulfide bond was formed between the Cys1 and Cys7 to develop cyclo-heptapeptide containing Lys-Gly-Asp-sequence. Structural simulation showed that Lys-Gly-Asp-motif (KDG) displayed functional conformation. The cyclo-heptapeptide exhibited potent anti-platelet aggregation activity based on specific recognition and interaction with the GPIIb-IIIa receptor on platelet cell membrane. The specific and potent anti-platelet activity makes the KGD-containing cyclo-heptapeptide a possible therapeutic agent.     

1-(3,4,5-Trimethoxyphenyl)ethane-1,2-diyl esters,a novel compound class with potent chemoreversal activity

1-(3,4,5-Trimethoxyphenyl)ethane-1,2-diyl esters, which share a fragment from (±)-3′-O-4′-O-bis(3,4-dimethoxycinnamoyl)-cis-khellactone (DMDCK) and 3′R,4′R-disubstituted-2′,2′-dimethyldihydropyrano[2,3-f]chromone (DSP), exhibited remarkable chemoreversal activity on multidrug resistant human nasopharyngeal carcinoma (KB) when combined with three anticancer drugs, paclitaxel, vincristine and doxorubicin. Among 15 novel synthesized analogs, bis-trimethoxybenzoyl derivative 15 was the most active (340-fold more active than verapamil when used with vincristine) followed by two di-cinnamoyl derivatives, 10 and 11, and then di-cyclohexanecarbonyl derivative 9. All aliphatic chain derivatives, 3–5, showed no activity. Structure-activity relationship study indicated that a di-ester structure was critical to enhance the activity resulting from the maintenance of the spatial arrangement proposed by the pharmacophore based on the verapamil-binding site. Further mechanism of action study showed 15 inhibited mainly P-glycoprotein efflux pump function, while 13 exhibited an additional multidrug resistance-associated protein efflux pump function.     

Immunomodulation-mediated anticancer activity of a novel compound from Brugmansia suaveolens leaves

Immunomodulation activity-guided fractionation of ethanol extract of Brugmansia suaveolens leaves was carried out to isolate a novel compound SUPH036-022A (1) by co-culturing the test fraction/compound activated PBMC with MCF7 and A549 cancer cell lines. Assessment of immune markers in PBMC, and analysis of apoptosis markers and cell cycle was carried out for cancer cells. The structure of the isolated compound was elucidated by spectral analysis. Compound 1 enhanced the secretion of immune markers, IL-2 and IFN-γ, from PBMC. Further, compound 1 treated PBMC increased cell death in MCF7 and A549 cell lines and induced ROS production and mitochondrial membrane perturbation, leading to apoptosis. Flow cytometry analysis revealed; compound 1 stimulated PBMC to cause a five-fold increase in cell cycle perturbations in the sub-G1 stage of cancer cells as compared to the negative control. The compound, in the absence of PBMC, only had a weak cytotoxic activity against these cell lines. Thus, compound 1 is a novel lead for immunomodulation-mediated anticancer activity.     

Design,synthesis and evaluation of novel sophoridinic imine derivatives containing conjugated planar structure as potent anticancer agents

Based on our previous study and the binding mode of camptothecin with Topo I, a series of novel sophoridine imine derivatives containing conjugated planar structure were designed, synthesized and tested for their in vitro anticancer activity. The results showed that most of the derivatives displayed potent activity. In particular, compounds 10b exhibited excellent anti-proliferative activities with IC₅₀ 5.7?µM and 8.5?µM against HepG-2 and HeLa cell lines, respectively. Molecular docking studies revealed that the introduction of conjugated planar structure could form π-π stacking interaction with DNA, leading to the improvement of biological activity. Its mode of action was to inhibit the activity of DNA Topo I, followed by the G0/G1 phase arrest. This work provides a theoretical basis for structural optimizations and exploring anticancer pathways of this kind of compound and 10b could emerge as promising lead compounds for the development of novel Topo I inhibitors.     

Chlorimipramine: a novel anticancer agent with a mitochondrial target

Mitochondria have been suggested to be a potential intracellular target for cancer chemotherapy. In this report, we demonstrate the ability of the tricyclic antidepressant chlorimipramine to kill human glioma cells in vitro by a molecular mechanism resulting in an increase in caspase 3 activity following inhibition of glioma oxygen consumption. Studies with isolated rat mitochondria showed that chlorimipramine specifically inhibited mitochondrial complex III activity, which causes decreased mitochondrial membrane potential as well as mitochondrial swelling and vacuolation. The use of chlorimipramine in human as an effective, non-toxic cancer therapeutic having a strong selectivity between cancer cells and normal cells on the basis of their mitochondrial function is discussed.     

Discovery of a novel bicyclic compound,DS54360155, as an orally potent analgesic without mu-opioid receptor agonist activity

We synthesized derivatives of a natural alkaloid, conolidine, and evaluated these derivatives in the acetic acid-induced writhing test and formalin test in ddY mice after oral administration. As a result, we identified (5S)-6-methyl-1,3,4,5,6,8-hexahydro-7H-2,5-methano[1,5]diazonino[7,8-b]indol-7-one sulfate salt, 15a (DS54360155), with a unique and original bicyclic skeleton, as an analgesic more potent than conolidine. Moreover, 15a did not exhibit mu-opioid receptor agonist activity.     

Synthesis of a novel series of artemisinin dimers with potent anticancer activity involving Sonogashira cross-coupling reaction

A series of C-10 acetal artemisinin dimers were synthesized using Sonogashira cross-coupling reaction. All these novel semisynthetic artemisinin dimers exhibited excellent growth inhibitory activity against Lung A-549 human cancer cell line.     

Optimization of substituted cinnamic acyl sulfonamide derivatives as tubulin polymerization inhibitors with anticancer activity

A new series of novel cinnamic acyl sulfonamide derivatives were designed and synthesized and evaluated their anti-tubulin polymerization activities and anticancer activities. One of these compounds, compound 5a with a benzdioxan group, was observed to be an excellent tubulin inhibitor (IC₅₀?=?0.88?µM) and display the best antiproliferative activity against MCF-7 with an IC₅₀ value of 0.17?μg/mL. Docking simulation was performed to insert compound 5a into the crystal structure of tubulin at colchicine binding site to determine the probable binding model. 3D-QSAR model was also built to provide more pharmacophore understanding that could be used to design new agents with more potent anti-tubulin polymerization activity.     

Plocabulin,a novel tubulin inhibitor,has potent antitumor activity in patient-derived xenograft models of gastrointestinal stromal tumors

The majority of patients with gastrointestinal stromal tumors (GIST) eventually become resistant with time due to secondary mutations in the driver receptor tyrosine kinase. Novel treatments that do not target these receptors may therefore be preferable. For the first time, we evaluated a tubulin inhibitor, plocabulin, in patient-derived xenograft (PDX) models of GIST, a disease generally considered to be resistant to cytotoxic agents. Three PDX models of GIST with different KIT genotype were generated by implanting tumor fragments from patients directly into nude mice. We then used these well characterized models with distinct sensitivity to imatinib to evaluate the efficacy of the novel tubulin inhibitor. The efficacy of the drug was assessed by volumetric analysis of the tumors, histopathology, immunohistochemistry and Western blotting. Plocabulin treatment led to extensive necrosis in all three models and significant tumor shrinkage in two models. This histological response can be explained by the drug's vascular-disruptive properties, which resulted in a shutdown of tumor vasculature, reflected by a decreased total vascular area in the tumor tissue. Our results demonstrated the in vivo efficacy of the novel tubulin inhibitor plocabulin in PDX models of GIST and challenge the established view that GIST are resistant to cytotoxic agents in general and to tubulin inhibitors in particular. Our findings provide a convincing rationale for early clinical exploration of plocabulin in GIST and warrant further exploration of this class of drugs in the management of this common sarcoma subtype.     

Synthesis and anticancer activity of novel bisindolylhydroxymaleimide derivatives with potent GSK-3 kinase inhibition

Synthesis and biological evaluation of a series of novel indole derivatives as anticancer agents is described. A bisindolylmaleimide template has been derived as a versatile pharmacophore with which to pursue chemical diversification. Starting from maleimide, the introduction of an oxygen to the headgroup (hydroxymaleimide) was initially investigated and the bioactivity assessed by screening of kinase inhibitory activity, identifying substituent derived selectivity. Extension of the hydroxymaleimide template to incorporate substitution of the indole nitrogens was next completed and assessed again by kinase inhibition identifying unique selectivity patterns with respect to GSK-3 and CDK kinases. Subsequently, the anticancer activity of bisindolylmaleimides were assessed using the NCI-60 cell screen, disclosing the discovery of growth inhibitory profiles towards a number of cell lines, such as SNB-75 CNS cancer, A498 and UO-31 renal, MDA MB435 melanoma and a panel of leukemia cell lines. The potential for selective kinase inhibition by modulation of this template is evident and will inform future selective clinical candidates.     

Optimization of gefitinib analogues with potent anticancer activity

The interactions of gefitinib (Iressa) in EGFR are hydrogen bonding and van der Waals forces through quinazoline and aniline rings. However the morpholino group of gefitinib is poorly ordered due to its weak electron density. A series of novel piperazino analogues of gefitinib where morpholino group substituted with various piperazino groups were designed and synthesized. Most of them indicated significant anti-cancer activities against human cancer cell lines. In particular, compounds 52–54 showed excellent potency against cancer cells. Convergent synthetic approach has been developed for the synthesis of gefitinib intermediate which can lead to gefitinib as well as numerous analogues.     

Design and synthesis of novel oridonin analogues as potent anticancer agents

To identify anticancer agents with higher potency and lower toxicity, a series of oridonin derivatives with substituted benzene moieties at the C17 position were designed, synthesised, and evaluated for their antiproliferative properties. Most of the derivatives exhibited antiproliferative effects against AGS, MGC803, Bel7402, HCT116, A549, and HeLa cells. Compound 2p (IC_50?=?1.05?µM) exhibited the most potent antiproliferative activity against HCT116 cells; it was more potent than oridonin (IC₅₀?=?6.84?µM) and 5-fluorouracil (5-FU) (IC_50?=?24.80?µM). The IC₅₀ value of 2p in L02 cells was 6.5-fold higher than that in HCT116 cells. Overall, it exhibited better selective antiproliferative activity and specificity than oridonin and 5-FU. Furthermore, compound 2p arrested HCT116 cells at the G2 phase of the cell cycle and increased the percentage of apoptotic cells to a greater extent than oridonin.