Microtubule destabilising activity of selected 7-methoxy-2-phenylbenzo[b]furan derivative against primary and metastatic melanoma cells

Herein, we report the results of anticancer screening of two 2-phenylbenzo[b]furan derivatives functionalised at the 3-position with 4-hydroxy-3,5-dimethoxybenzoyl (BF2) or 3,4,5-trimethoxybenzoyl (BF3) against 60 different cancer cell lines. The results confirmed the anticancer potential of the tested compounds against different cancer cell types, especially colon cancer, brain cancer and melanoma. BF3 was defined as the most potent (also as a tubulin polymerisation inhibitor). Its anticancer activity against melanoma cell lines that originated from different stages, i.e., primary skin-derived A375 and metastatic WM9/MDA-MB-435S, was evaluated (as the clinical success of melanoma therapy strictly depends on the disease stage). Moreover, to determine the BF3 mode of action and its effect on cell proliferation, intracellular microtubule networks, cell cycle phase distribution and apoptosis were evaluated. Our study revealed that BF3 inhibited cell proliferation in a dose-dependent manner, with IC50 yielding 0.09 ± 0.01 μM, 0.11 ± 0.01 μM and 0.18 ± 0.05 μM for A375, MDA-MB435S and WM9, respectively. The strong antiproliferative activity of compound BF3 correlated well with its inhibitory effect on tubulin polymerisation. Molecular docking proved that BF3 belongs to the colchicine binding site inhibitors (CBSIs), and experimental studies revealed that it disturbs cell cycle progression leading to G2/M arrest and apoptosis.

Synthesis and Biological Studies of Benzo[b]furan Derivatives: A Review from 2011 to 2022

The importance of the benzo[b]furan motif becomes evident in the remarkable results of numerous biological investigations, establishing its potential as a robust therapeutic option. This review presents an overview of the synthesis of and exhaustive biological studies conducted on benzo[b]furan derivatives from 2011 to 2022, accentuating their exceptional promise as anticancer, antibacterial, and antifungal agents. Initially, the discussion focuses on chemical synthesis, molecular docking simulations, and both in vitro and in vivo studies. Additionally, we provide an analysis of the intricate interplay between structure and activity, thereby facilitating comparisons and profoundly emphasizing the applications of the benzo[b]furan motif within the realms of drug discovery and medicinal chemistry.

Synthesis and biological evaluation of benzofuran piperazine derivatives as potential anticancer agents

This work describes about the synthesis and evaluation of substituted benzofuran piperazines as potential anticancer agents. The synthesized candidates have been evaluated for their cell proliferation inhibition properties in six murine and human cancer cell lines. In vitro evaluation of apoptosis and cell cycle analysis with the lead candidate 1.19 reveals that necrosis might be an important pathway for the candidate compounds to cause cell death. Further, in vivo evaluation of the lead compound shows that this candidate is well tolerated in healthy mice. Additionally, an in vivo anticancer efficacy study in mice using a MDA-MB-231 xenograft model with the lead compound provides good anti-cancer efficacy.

Virtual and experimental high throughput screening of substituted hydrazones on β-Tubulin polymerization

Microtubule targeting agents that disrupt the dynamic functioning of the mitotic spindle are some of the best chemotherapeutic agents. Interruption of microtubule dynamics through polymerization or depolymerization causes cell arrest leading to apoptosis. We report a novel class of aroylhydrazones with anticancer properties. Tubulin inhibition studies were performed using both computational and biological methods. Docking and pharmacophore mapping showed efficient binding between the ligands and the protein. Tubulin inhibition assay showed the aroylhydrazones to be inhibitors of tubulin polymerization. DFT studies explains the geometrical and electronic properties of the compounds. Furthermore, anticancer studies using lung and liver cancer cell lines gave low IC₅₀ values with the methyl substituted hydrazone MH-2 being the most potent. (IC₅₀ of 0.0896 and 0.1040 µM respectively). The methyl group is responsible for the effective binding to the protein. Thus, a new class of tubulin binding agents have been identified as potential agents in cancer therapy.

Developments of isoCombretastatin A-4 derivatives as highly cytotoxic agents

Combretastatin A-4 (CA-4) is a natural anti-cancer agent isolated in 1989 from the African willow tree, Combretum caffrum. Due to its chemical simplicity, this (Z)-stilbene has been the subject of many structural modifications mainly to improve its chemical and metabolic stability. Beside a large number of synthetic analogues, isoCombretastatin A-4 (isoCA-4), has proved to be a solution of choice since this non-natural isomer of CA-4 is stable, easier to synthesize and has equivalent antitumor properties as CA-4. In this review, we will present the structure-activity relationships (SARs) around isoCA-4 since its discovery in 2007. In a first part, we will describe some alternatives to replace the phenol B-ring of isoCA-4, then we will focus on the variations made on the 1,1-ethylene double bond and then, we will evocate very recent exiting results concerning the possible replacements of the 3,4,5-trimethoxyphenyl A-ring of isoCA-4 by suitable heterocycles.

Discovery and optimization of 3,4,5-trimethoxyphenyl substituted triazolylthioacetamides as potent tubulin polymerization inhibitors

Based on our previous research, three series of new triazolylthioacetamides possessing 3,4,5-trimethoxyphenyl moiety were synthesized, and evaluated for antiproliferative activities and inhibition of tubulin polymerization. The most promising compounds 8b and 8j demonstrated more significant antiproliferative activities against MCF-7, HeLa, and HT-29 cell lines than our lead compound 6. Moreover, analogues 8f, 8j, and 8o manifested more potent antiproliferative activities against HeLa cell line with IC₅₀ values of 0.04, 0.05 and 0.16 μM, respectively, representing 100-, 82-, and 25-fold improvements of the activity compared to compound 6. Furthermore, the representative compound, 8j, was found to induce significant cell cycle arrest at the G₂/M phase in HeLa cell lines via a concentration-dependent manner. Meanwhile, compound 8b exhibited the most potent tubulin polymerization inhibitory activity with an IC₅₀ value of 5.9 μM, which was almost as active as that of CA-4 (IC₅₀ = 4.2 μM). Additionally, molecular docking analysis suggested that 8b formed stable interactions in the colchicine-binding site of tubulin.

Synthesis of imidazo-thiadiazole linked indolinone conjugates and evaluated their microtubule network disrupting and apoptosis inducing ability

A series of imidazo[2,1-b][1,3,4]thiadiazole linked indolinone conjugates were synthesized and investigated for antiproliferative activity in different human cancer cell lines by changing various substitutions at indolinone and phenyl ring systems. Among them conjugates 7, 14 and 15 were exhibited potent antiproliferative activity with GI₅₀ values from 0.13 to 3.8 μΜ and evaluated for cell cycle analysis, tubulin polymerization assay and apoptosis. Treatment with 7, 14 and 15 were resulted in accumulation of cells in G2/M phase, inhibition of tubulin assembly, disruption of microtubule network. Inhibition of tubulin polymerization was further supported by Western blot analysis. In addition, the conjugates (7, 14 and 15) also showed apoptosis in HeLa cell line, detailed biological studies such as Hoechst 33,258 staining, DNA fragmentation and caspase-3 assays suggested that these compounds induce cell death by apoptosis. Docking studies revealed that these compounds (7, 14 and 15) bind with αAsn101, αThr179, αSer178, βCys241, βLys254 and βLys352 in the colchicine-binding site of the tubulin.

Development of combretastatins as potent tubulin polymerization inhibitors

The combretastatins are isolated from South African tree combretum caffrum kuntze. The lead compound combretastatin A-4 has displayed remarkable cytotoxic effect in a wide variety of preclinical tumor models and inhibits tubulin polymerization by interacting at colchicine binding site of microtubule. However, the structural simplicity of C A-4 is favorable for synthesis of various derivatives projected to induce rapid and selective vascular shutdown in tumors. Majority of the molecules have shown excellent antiproliferative activity and are able to inhibit tubulin polymerization as well as possible mechanisms of action have been investigated. In this review article, the synthesis and structure-activity relationships of C A-4 and immense number of its synthetic derivatives with various modifications on the A, B-rings, bridge carbons and their anti mitotic activities are discussed.

Benzofuran-2-acetic ester derivatives induce apoptosis in breast cancer cells by upregulating p21Cip/WAF1 gene expression in p53-independent manner

Breast cancer is the most common malignancy and the leading cause of cancer-related death in women worldwide. High toxicity of used chemotherapeutics and resistance of cancer cells to treatments are a driving force for searching the new drug candidates for breast cancer therapy. In this study, we tested the antiproliferative effects of a series of benzofuran-2-acetic methyl ester derivatives, synthesized by a palladium-catalyzed carbonylative heterocyclization approach, on breast cancer cells. We observed that benzofuran compounds bearing a phenyl or tert-butyl substituent α to the methoxycarbonyl group significantly inhibited anchorage-dependent and -independent cell growth, and induced G0/G1 cell cycle arrest in human estrogen receptor alpha positive (MCF-7 and T47D) and in triple negative MDA-MB-231 breast cancer cells, without affecting growth of MCF-10A normal breast epithelial cells. Mechanistically, benzofuran derivatives enhanced the cyclin-dependent kinase inhibitor p21^Cip/WAF1 expression at both mRNA and protein levels and this occurs transcriptionally in an Sp1-dependent manner. Moreover, benzofuran derivatives induced apoptosis, increased poly (ADP-ribose) polymerase cleavage and Bax/Bcl-2 ratio along with a marked DNA fragmentation along with a marked DNA fragmentation and a strong increase in TUNEL-positive breast cancer cells. Overall, we provide evidence that the newly tested benzofuran derivatives showed antiproliferative and pro-apoptotic activities against breast cancer cells regardless estrogen receptor status, suggesting their possible clinical development as anticancer agents.

Combretastatins: more than just vascular targeting agents?

Several prodrugs of the naturally occurring combretastatins have undergone extensive clinical evaluation as vascular targeting agents (VTAs). Their increased selectivity toward endothelial cells together with their innate ability to rapidly induce vascular shutdown and inhibit tumor growth at doses up to 10-fold less than the maximum tolerated dose led to the clinical evaluation of combretastatins as VTAs. Tubulin is well established as the molecular target of the combretastatins and the vast majority of its synthetic derivatives. Furthermore, tubulin is a highly validated molecular target of many direct anticancer agents routinely used as front-line chemotherapeutics. The unique vascular targeting properties of the combretastatins have somewhat overshadowed their development as direct anticancer agents and the delineation of the various cell death pathways and anticancer properties associated with such chemotherapeutics. Moreover, the ongoing clinical trial of OXi4503 (combretastatin-A1 diphosphate) together with preliminary preclinical evaluation for the treatment of refractory acute myelogenous leukemia has successfully highlighted both the indirect and direct anticancer properties of combretastatins. In this review, we discuss the development of the combretastatins from nature to the clinic. The various mechanisms underlying combretastatin-induced cell cycle arrest, mitotic catastrophe, cell death, and survival are also reviewed in an attempt to further enhance the clinical prospects of this unique class of VTAs.

Synthesis and biological evaluation of imidazo[1,5-a]pyridine-benzimidazole hybrids as inhibitors of both tubulin polymerization and PI3K/Akt pathway

A series of imidazo[1,5-a]pyridine-benzimidazole hybrids (5a–aa) were prepared and evaluated for their cytotoxic activity against a panel of sixty human tumor cell lines. Among them compounds 5d and 5l showed significant cytotoxic activity with GI50 values ranging from 1.06 to 14.9 μM and 0.43 to 7.73 μM, respectively. Flow cytometric analysis revealed that these compounds arrest the cell cycle at G2/M phase and induced cell death by apoptosis. The tubulin polymerization assay (IC50 of 5d is 3.25 μM and 5l is 1.71 μM) and immunofluorescence analysis showed that these compounds effectively inhibited the microtubule assembly in human breast cancer cells (MCF-7). Further, the apoptotic effects of compounds were confirmed by Hoechst staining, mitochondrial membrane potential, cytochrome c release, ROS generation, caspase 9 activation and DNA fragmentation analysis. After treatment with these compounds for 48 h, p-PTEN and p-AKT levels were markedly decreased. Moreover, these compounds did not significantly inhibit the normal human embryonic kidney cells, HEK-293. The molecular docking simulations predicted the binding interactions of 5d and 5l with colchicine binding site of the tubulin, which is in compliance with the antiproliferative activity data.

Poly(ADP-ribosyl)ation enhances H-RAS protein stability and causes abnormal cell cycle progression in human TK6 lymphoblastoid cells treated with hydroquinone

Hydroquinone (HQ), one of the most important benzene-derived metabolites, can induce aberrant cell cycle progression; however, the mechanism of this induction remains unclear. Poly(ADP-ribosyl)ation (PARylation), which is catalysed primarily by poly(ADP-ribose) polymerase-1 (PARP-1), participates in various biological processes, including cell cycle control. The results of the present study show an accumulation in G1 phase versus S phase of TK6 human lymphoblast cells treated with HQ for 48h compared with PBS-treated cells; after 72h of HQ treatment, the cells transitioned from G1 arrest to S phase arrest. We examined the expression of six genes related to the cell cycle or leukaemia to further explore the reason for this phenomenon. Among these genes, H-RAS was found to be associated with this phenomenon because its mRNA and protein expression decreased at 48h and increased at 72h. Experiments for PARP activity induction and inhibition revealed that the observed PARylation was positively associated with H-RAS expression. Moreover, in cells treated with HQ in conjunction with PARP-1 knockdown, expression of the H-RAS protein decreased and the number of cells in G1 phase increased. The degree of poly(ADP-ribosyl) modification of the H-RAS protein increased in cells treated with HQ for 72h, further supporting that changes in PARylation contributed to the rapid alteration of H-RAS protein expression, followed by abnormal progression of the cell cycle. Co-immunoprecipitation (co-IP) assays were employed to determine whether protein complexes were formed by PARP-1 and H-RAS proteins, and the direct interaction between these proteins indicated that PARylation regulated H-RAS expression. As detected by confocal microscopy, the H-RAS protein was found in the nucleus and cytoplasm. To our knowledge, this study is the first to reveal that H-RAS protein can be modified by PARylation.

Design, synthesis, in vitro, and in vivo anticancer and antiangiogenic activity of novel 3-arylaminobenzofuran derivatives targeting the colchicine site on tubulin

A new series of compounds characterized by the presence of a 2-methoxy/ethoxycarbonyl group, combined with either no substituent or a methoxy group at each of the four possible positions of the benzene portion of the 3-(3',4',5'-trimethoxyanilino)benzo[b]furan skeleton, were evaluated for antiproliferative activity against cancer cells in culture and, for selected, highly active compounds, inhibition of tubulin polymerization, cell cycle effects, and in vivo potency. The greatest antiproliferative activity occurred with a methoxy group introduced at the C-6 position, the least with this substituent at C-4. Thus far, the most promising compound in this series was 2-methoxycarbonyl-3-(3',4',5'-trimethoxyanilino)-6-methoxybenzo[b]furan (3g), which inhibited cancer cell growth at nanomolar concentrations (IC50 values of 0.3-27 nM), bound to the colchicine site of tubulin, induced apoptosis, and showed, both in vitro and in vivo, potent vascular disrupting properties derived from the effect of this compound on vascular endothelial cells. Compound 3g had in vivo antitumor activity in a murine model comparable to the activity obtained with combretastatin A-4 phosphate.

Biological and medicinal significance of benzofuran

This article emphasizes on the importance of benzofuran as a biologically relevant heterocycle. It covers most of the physiologically as well as medicinally important compounds containing benzofuran rings. This article also covers clinically approved drugs containing benzofuran scaffold.

Design and synthesis of imidazo[2,1-b]thiazole-chalcone conjugates: microtubule-destabilizing agents

A series of chalcone conjugates featuring the imidazo[2,1-b]thiazole scaffold was designed, synthesized, and evaluated for their cytotoxic activity against five human cancer cell lines (MCF-7, A549, HeLa, DU-145 and HT-29). These new hybrid molecules have shown promising cytotoxic activity with IC50 values ranging from 0.64 to 30.9 μM. Among them, (E)-3-(6-(4-fluorophenyl)-2,3-bis(4-methoxyphenyl)imidazo[2,1-b]thiazol-5-yl)-1-(pyridin-2-yl)prop-2-en-1-one (11 x) showed potent antiproliferative activity with IC50 values ranging from 0.64 to 1.44 μM in all tested cell lines. To investigate the mechanism of action, the detailed biological aspects of this promising conjugate (11 x) were carried out on the A549 lung cancer cell line. The tubulin polymerization assay and immunofluoresence analysis results suggest that this conjugate effectively inhibits microtubule assembly in A549 cells. Flow cytometric analysis revealed that this conjugate induces cell-cycle arrest in the G2/M phase and leads to apoptotic cell death. This was further confirmed by Hoechst staining, activation of caspase-3, DNA fragmentation analysis, and Annexin V-FITC assay. Moreover, molecular docking studies indicated that this conjugate (11 x) interacts and binds efficiently with the tubulin protein.

Design and synthesis of aminostilbene-arylpropenones as tubulin polymerization inhibitors

A series of aminostilbene-arylpropenones were designed and synthesized by Michael addition and were investigated for their cytotoxic activity against various human cancer cell lines. Some of the investigated compounds exhibited significant antiproliferative activity against a panel of 60 human cancer cell lines of the US National Cancer Institute, with 50 % growth inhibition (GI50) values in the range from < 0.01 to 19.9 μM. One of the compounds showed a broad spectrum of antiproliferative efficacy on most of the cell lines, with a GI50 value of < 0.01 μM. All of the synthesized compounds displayed cytotoxicity against A549 (non-small-cell lung cancer), HeLa (cervical carcinoma), MCF-7 (breast cancer), and HCT116 (colon carcinoma) with 50 % inhibitory concentration (IC50) values ranging from 0.011 to 8.56 μM. A cell cycle assay revealed that these compounds arrested the G2/M phase of the cell cycle. Two compounds exhibited strong inhibitory effects on tubulin assembly with IC50 values of 0.71 and 0.79 μM. Moreover, dot-blot analysis of cyclin B1 demonstrated that some of the congeners strongly induced cyclin B1 protein levels. Molecular docking studies indicated that these compounds occupy the colchicine binding site of tubulin.

Synthesis and biological evaluation of 1,2,3-triazole linked aminocombretastatin conjugates as mitochondrial mediated apoptosis inducers

A series of 1,2,3-triazole linked aminocombretastatin conjugates were synthesized and evaluated for cytotoxicity, inhibition of tubulin polymerization and apoptosis inducing ability. Most of the conjugates exhibited significant anticancer activity against some representative human cancer cell lines and two of the conjugates 6d and 7c displayed potent cytotoxicity with IC50 values of 53 nM and 44 nM against A549 human lung cancer respectively, and were comparable to combretastatin A-4 (CA-4). SAR studies revealed that 1-benzyl substituted triazole moiety with an amide linkage at 3-position of B-ring of the combretastatin subunit are more active compared to 2-position. G2/M cell cycle arrest was induced by these conjugates 6d and 7c and the tubulin polymerization assay (IC50 of 1.16 μM and 0.95 μM for 6d and 7c, respectively) as well as immunofluorescence analysis showed that these conjugates effectively inhibit microtubule assembly at both molecular and cellular levels in A549 cells. Colchicine competitive binding assay suggested that these conjugates bind at the colchicine binding site of tubulin as also observed from the docking studies. Further, mitochondrial membrane potential, ROS generation, caspase-3 activation assay, Hoechst staining and DNA fragmentation analysis revealed that these conjugates induce cell death by apoptosis.