Tubulin Polymerization Activity Research Articles

Development of a natural product optimization strategy for inhibitors against MraY, a promising antibacterial target

MraY (phospho-N-acetylmuramoyl-pentapeptide-transferase) inhibitory natural products are attractive molecules as candidates for a new class of antibacterial agents to combat antimicrobial-resistant bacteria. Structural optimization of these natural products is required to improve their drug-like properties for therapeutic use. However, chemical modifications of these natural products are painstaking tasks due to complex synthetic processes, which is a bottleneck in advancing natural products to the clinic. Here, we develop a strategy for a comprehensive in situ evaluation of the build-up library, which enables us to streamline the preparation of the analogue library and directly assess its biological activities. We apply this approach to a series of MraY inhibitory natural products. Through construction and evaluation of the 686-compound library, we identify promising analogues that exhibit potent and broad-spectrum antibacterial activity against highly drug-resistant strains in vitro as well as in vivo in an acute thigh infection model. Structures of the MraY-analogue complexes reveal distinct interaction patterns, suggesting that these analogues represent MraY inhibitors with unique binding modes. We further demonstrate the generality of our strategy by applying it to tubulin-binding natural products to modulate their tubulin polymerization activities.

The Development of HDAC and Tubulin Dual-Targeting Inhibitors for Cancer Therapy.

Histone deacetylases (HDACs) are a class of enzymes that are responsible for the removal of acetyl groups from the ε-N-acetyl lysine of histones, allowing histones to wrap DNA more tightly. HDACs play an essential role in many biological processes, such as gene regulation, transcription, cell proliferation, angiogenesis, migration, differentiation and metastasis, which make it an excellent target for anticancer drug discovery. The search for histone deacetylase inhibitors (HDACis) has been intensified, with numerous HDACis being discovered, and five of them have reached the market. However, currently available HDAC always suffers from several shortcomings, such as limited efficacy, drug resistance, and toxicity. Accordingly, dual-targeting HDACis have attracted much attention from academia to industry, and great advances have been achieved in this area. In this review, we summarize the progress on inhibitors with the capacity to concurrently inhibit tubulin polymerization and HDAC activity and their application in cancer treatment.

Fatty Acid Conjugated Chalcones as Tubulin Polymerization Inhibitors: Design, Synthesis, QSAR, and Apoptotic and Antiproliferative Activity.

Cancer is often associated with an aberrant increase in tubulin and microtubule activity required for cell migration, invasion, and metastasis. A new series of fatty acid conjugated chalcones have been designed as tubulin polymerization inhibitors and anticancer candidates. These conjugates were designed to harness the beneficial physicochemical properties, ease of synthesis, and tubulin inhibitory activity of two classes of natural components. New lipidated chalcones were synthesized from 4-aminoacetophenone via N-acylation followed by condensation with different aromatic aldehydes. All new compounds showed strong inhibition of tubulin polymerization and antiproliferative activity against breast and lung cancer cell lines (MCF-7 and A549) at low or sub-micromolar concentrations. A significant apoptotic effect was shown using a flow cytometry assay that corresponded to cytotoxicity against cancer cell lines, as indicated by a 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide assay. Decanoic acid conjugates were more potent than longer lipid analogues, with the most active being more potent than the reference tubulin inhibitor, combretastatin-A4 and the anticancer drug, doxorubicin. None of the newly synthesized compounds caused any detectable cytotoxicity against the normal cell line (Wi-38) or hemolysis of red blood cells below 100 μM. It is unlikely that the new conjugates described would affect normal cells or interrupt with cell membranes due to their lipidic nature. A quantitative structure-activity relationship analysis was performed to determine the influence of 315 descriptors of the physicochemical properties of the new conjugates on their tubulin inhibitory activity. The obtained model revealed a strong correlation between the tubulin inhibitory activity of the investigated compounds and their dipole moment and degree of reactivity.

CuI-mediated synthesis of 1-aryl-5,6,7-trimethoxybenzimidazoles as potent antitubulin agents.

In situ CuI-mediated cyclization methodology helped yield benzimidazoles with different substitution manner, such as 1,2-diarylbenzimidazoles (4 and 5) and 1-arylbenzimidazoles (6-15). The result of structure-activity relationship (SAR) study confirmed the significance of the 5,6,7-trimethoxybenzimidazole moiety, and the representative derivatives (8-10) exhibited marked antiproliferative activity against A549, HCT-116, and PC-3 cells; in addition, they are able to inhibit the polymerization of tubulin. Among them, compound 10 inhibited the growth of A549, HCT-116, and PC-3 cells with a mean IC50 value of 0.07 μM, and its IC50 value of tubulin polymerization is 0.26 μM.

Design, synthesis and biological evaluation of quinoline-2-carbonitrile-based hydroxamic acids as dual tubulin polymerization and histone deacetylases inhibitors

A series of quinoline and quinazoline analogs were designed and synthesized as new tubulin polymerization (TP) and histone deacetylases (HDAC) inhibitors. Compounds 12a and 12d showed the best cytotoxicity activities against a panel of human cancer cell lines with an averaged IC50 value of 0.6 and 0.7 nM, respectively. Furthermore, these lead compounds showed good activities against CA-4-resistant colon-carcinoma and multidrug-resistant leukemia cells. In addition, compounds 12a and 12d induced HT29 cell cycle arrest in the G2/M phase and produced caspase-induced apoptosis of HT29 cells through mitochondrial dysfunction. Also, 12a and 12d inhibited HDAC8, 6, and 11 activities. Furthermore, lead compound 12a exhibited higher metabolic stability than isoCA-4 and was highly potent in suppressing tumor growth in the fibrosarcoma MCA205 tumor model. Collectively, these studies suggest that 12a represents a new dual inhibitor of TP and HDAC activities, which makes it a suitable candidate for further investigations in clinical development.

2-Methoxydiol derivatives as new tubulin and HDAC dual-targeting inhibitors, displaying antitumor and antiangiogenic response

Multi-target drugs design has become an active research field because of their advantages in cancer treatment. In present study, HDAC inhibitors pharmacophore and 2-methoxyestradiol(2ME2) were combined into a new hybrid molecule for the first time. Forty-seven 2ME2 derivatives were synthesized and evaluated for antiproliferative activity. In particular, compound 4s exhibited a dual inhibition of tubulin polymerization and HDAC (IC50 = 0.06 µM toward HDAC2) activity, as well as the most potent cytotoxicity IC50 values of 0.37–4.84 µM against six cancer cell lines. Compound 4s remarkably disrupted microtubule networks, arrested cell cycle at G2/M phase, induced mitochondrial membrane potential collapse and eventually apoptosis in A549 cells. Notably, 4s was discovered to potently imped the tube-formation of HUVECs and prohibited the proliferation, migration, and invasion of HUVECs, as well as A549 cells. In addition, the anti-angiogenic and anti-metastasis activities were demonstrated via a zebrafish model test. All these beneficial anticancer activities together with its high selectivity toward noncancer cells, suggested 4s may deserves consideration for cancer therapy.

Inhibition of nitric oxide production enhances the activity of facial nerve tubulin polymerization and the ability of tau to promote microtubule assembly after neurorrhaphy

We previously reported that inhibition of nitric oxide (NO) production promotes rat reconnected facial nerve regeneration. However, the underlying mechanism is obscure. Microtubule assembly is known to be essential to axon regeneration; nevertheless, tubulins and microtubule-associated proteins (MAPs) have been demonstrated as targets for NO and peroxynitrite. Thus, we hypothesized that NO and/or peroxynitrite may affect facial nerve regeneration via influencing on microtubule assembly. First, tubulins and tau (a MAP) were extracted from facial nerves of normal rats, treated with NO donor or peroxynitrite, and processed for microtubule assembly assay. We found that peroxynitrite, DEA NONOate, and Angeli's salt reduced the tubulin polymerization activity to a greater extent than GSNO, SIN-1, and SNAP. Additionally, SIN-1, peroxynitrite, and Angeli's salt impaired the ability of tau to promote microtubule assembly. Next, nitrosative stress biomarkers 3-nitrotyrosine (3-NT) and S-nitrosylated cysteine (SNO-Cys) were immunolabeled in facial nerves. Both biomarkers were highly upregulated in proximal and distal stumps of reconnected facial nerves at 3 days and 1 week after neurorrhaphy. Notably, the expression of 3-NT was greatly reduced at 2 weeks, whereas that of SNO-Cys was maintained. Conversely, inhibition of NO production with L-NAME prevented the upregulation of SNO-Cys. Further, we used tubulins and tau extracted from facial nerves of sham-operated, nerve suture + vehicle treatment, and nerve suture + L-NAME treatment rats to perform microtubule assembly assay. We found that L-NAME treatment enhanced polymerization activity of tubulins and ability of tau to promote microtubule assembly. It is noteworthy that α-tubulin plays a more important role than β-tubulin since the activity of microtubule assembly using α-tubulin extracted from L-NAME-treated rats was greatly elevated, whereas that using β-tubulin extracted from L-NAME-treated rats was not. Overall, our findings support that inhibition of NO production reduces nitrosative stress, and may thus facilitate microtubule assembly and facial nerve regeneration.

Neomenthol prevents the proliferation of skin cancer cells by restraining tubulin polymerization and hyaluronidase activity

IntroductionNeomenthol, a cyclic monoterpenoid, is a stereoisomer of menthol present in the essential oil of Mentha spp. It is used in food as a flavoring agent, in cosmetics and medicines because of its cooling effects. However, neomenthol has not been much explored for its anticancer potential. Additionally, targeting hyaluronidase, Cathepsin-D, and ODC by phytochemicals is amongst the efficient approach for cancer prevention and/or treatment. ObjectivesTo investigate the molecular and cell target-based antiproliferative potential of neomenthol on human cancer (A431, PC-3, K562, A549, FaDu, MDA-MB-231, COLO-205, MCF-7, and WRL-68) and normal (HEK-293) cell lines. MethodsThe potency of neomenthol was evaluated on human cancer and normal cell line using SRB, NRU and MTT assays. The molecular target based study of neomenthol was carried out in cell-free and cell-based test systems. Further, the potency of neomenthol was confirmed by quantitative real-time PCR analysis and molecular docking studies. The in vivo anticancer potential of neomenthol was performed on mice EAC model and the toxicity examination was accomplished through in silico, ex vivo and in vivo approaches. ResultsNeomenthol exhibits a promising activity (IC50 17.3 ± 6.49 μM) against human epidermoid carcinoma (A431) cells by arresting the G2/M phase and increasing the number of sub-diploid cells. It significantly inhibits hyaluronidase activity (IC50 12.81 ± 0.01 μM) and affects the tubulin polymerization. The expression analysis and molecular docking studies support the in vitro molecular and cell target based results. Neomenthol prevents EAC tumor formation by 58.84% and inhibits hyaluronidase activity up to 10% at 75 mg/kg bw, i.p. dose. The oral dose of 1000 mg/kg bw was found safe in acute oral toxicity studies. ConclusionNeomenthol delayed the growth of skin carcinoma cells by inhibiting the tubulin polymerization and hyaluronidase activity, which are responsible for tumor growth, metastasis, and angiogenesis.

2-APCAs, the Novel Microtubule Targeting Agents Active Against Distinct Cancer Cell Lines.

Microtubules are known as the most attractive molecular targets for anti-cancer drugs. However, the number of serious limitations of the microtubule targeting agents (MTAs) including poor bioavailability, adverse effects (e.g., systemic and neural toxicity), and acquired resistance after initiation of MTA-based therapy remain the driving forces to develop the novel therapeutic agents effectively targeting microtubules and exhibiting potent anti-tumor activities. Here, we report the discovery of 2-amino-pyrrole-carboxamides (2-APCAs), a novel class of MTA, which effectively inhibited the growth of the broad spectrum of cancer cell lines in vitro, including various types of breast, prostate, and non-small lung cancer (NSLC), soft tissue sarcomas (STS) (e.g., leio-, rhabdomyo-, and fibrosarcomas), osteosarcomas and gastrointestinal stromal tumors (GISTs). Importantly, 2-APCAs were also effective in cancer cell lines exhibiting resistance to certain chemotherapeutic agents, including MTAs and topoisomerase II inhibitors. The anti-proliferative effect of 2-APCAs was due to their ability to interfere with the polymerization of tubulin and thereby leading to the accumulation of tumor cells in the M-phase. As an outcome of the mitotic arrest, cancer cells underwent apoptotic cell death which was evidenced by increased expression of cleaved forms of the poly-ADP-ribose polymerase (PARP) and caspase-3 and the increased numbers of Annexin V-positive cells, as well. Among the compounds exhibiting the potent anti-cancer activities against the various cancer cell lines indicated above, 2-APCA-III was found the most active. Importantly, its cytotoxic activities correlated with its highest potency to interfere with the dynamics of tubulin polymerization and inducement of cell cycle arrest in the G2/M phase. Interestingly, the cytotoxic and tubulin polymerization activities of 2-APCAs correlated with the stability of the «tubulin—2-АРСА» complexes, illustrating the “tubulin-2-APCA-III” complex as the most stable. Molecular docking showed that the binding site for 2-АРСА-III is located in α tubulin by forming a hydrogen bond with Leu23. Of note, single-cell electrophoresis (Comet assay) data illustrated the low genotoxic activities of 2-APCAs when compared to certain anti-cancer chemotherapeutic agents. Taken together, our study describes the novel MTAs with potent anti-proliferative and pro-apoptotic activities, thereby illustrating them as a scaffold for the development of successful chemotherapeutic anti-cancer agent targeting microtubules.

10-(4-Phenylpiperazine-1-carbonyl)acridin-9(10H)-ones and related compounds: Synthesis, antiproliferative activity and inhibition of tubulin polymerization

As part of our continuing search for potent inhibitors of tubulin polymerization, two novel series of 42 10-(4-phenylpiperazine-1-carbonyl)acridin-9(10H)-ones and N-benzoylated acridones were synthesized on the basis of a retrosynthetic approach. All newly synthesized compounds were tested for antiproliferative activity and interaction with tubulin. Several analogs potently inhibited tumor cell growth. Among the compounds tested, 10-(4-(3-methoxyphenyl)piperazine-1-carbonyl)acridin-9(10H)-one (17c) exhibited excellent growth inhibitory effects on 93 tumor cell lines, with an average GI50 value of 5.4 nM. We were able to show that the strong cytotoxic effects are caused by disruption of tubulin polymerization, as supported by the EBI (N,N'-Ethylenebis(iodoacetamide)) assay and the fact that the most potent inhibitors of cancer cell growth turned out to be the most efficacious tubulin polymerization inhibitors. Potencies were nearly comparable or superior to those of the antimitotic reference compounds. Closely related to this, the most active analogs inhibited cell cycling at the G2/M phase at concentrations down to 30 nM and induced apoptosis in K562 leukemia cells. We believe that our work not only proves the excellent suitability of the acridone scaffold for the design of potent tubulin polymerization inhibitors but also enables synthetic access to further potentially interesting N-acylated acridones.

Synthesis and Biological Evaluation of 2-Substituted Benzyl-/Phenylethylamino-4-amino-5-aroylthiazoles as Apoptosis-Inducing Anticancer Agents.

Induction of apoptosis is a common chemotherapeutic mechanism to kill cancer cells The thiazole system has been reported over the past decades as a building block for the preparation of anticancer agents. A novel series of 2-arylalkylamino-4-amino-5-(3′,4′,5′-trimethoxybenzoyl)-thiazole derivatives designed as dual inhibitors of tubulin and cyclin-dependent kinases (CDKs) were synthesized and evaluated for their antiproliferative activity in vitro against two cancer cell lines and, for selected highly active compounds, for interactions with tubulin and cyclin-dependent kinases and for cell cycle and apoptosis effects. Structure-activity relationships were elucidated for various substituents at the 2-position of the thiazole skeleton. Among the synthesized compounds, the most active analogues were found to be the p-chlorobenzylamino derivative 8e as well as the p-chloro and p-methoxyphenethylamino analogues 8f and 8k, respectively, which inhibited the growth of U-937 and SK-MEL-1 cancer cell lines with IC50 values ranging from 5.7 to 12.2 μM. On U-937 cells, the tested compounds 8f and 8k induced apoptosis in a time and concentration dependent manner. These two latter molecules did not affect tubulin polymerization (IC50 > 20 μM) nor CDK activity at a single concentration of 10 μM, suggesting alternative targets than tubulin and CDK for the compounds.

Water mediated synthesis of 6-amino-5-cyano-2-oxo-N-(pyridin-2-yl)-4-(p-tolyl)-2H-[1,2'-bipyridine]-3-carboxamide and 6-amino-5-cyano-4-(4-fluorophenyl)-2-oxo-N-(pyridin-2-yl)-2H-[1,2'-bipyridine]-3-carboxamide - An experimental and computational studies with non-linear optical (NLO) and molecular docking analyses.

6-Amino-5-cyano-2-oxo-N-(pyridin-2-yl)-4-(p-tolyl)-2H-[1,2'-bipyridine]-3-carboxamide and 6-amino-5-cyano-4-(4-fluorophenyl)-2-oxo-N-(pyridin-2-yl)-2H-[1,2'-bipyridine]-3-carboxamide were synthesized through three-component reaction between N1,N3-di(pyridin-2-yl)-malonamide, aldehyde and malononitrile in water using triethylamine as a base at room temperature. Synthesized compounds were characterized by using different techniques (FT-IR, NMR and X-ray diffraction). Additionally, the mentioned compounds were investigated by computational chemistry methods. Obtained results were supported with calculated results. Additionally, NLO properties and molecular docking analyses of related compounds were examined in detail. The binding modes of the compounds 4a and 4b were explored with the colchicine binding site of tubulin, from molecular docking studies, remarkable interactions have been observed for 4a and 4b near to the colchicines binding site of tubulin that may contribute to the inhibition of tubulin polymerization and anticancer activity.

Potent combretastatin A-4 analogs containing 1,2,4-triazole: Synthesis, antiproliferative, anti-tubulin activity, and docking study

A series of cis restricted 1,2,4-triazole analogs of combretastatin A-4 (CA-4) were designed and synthesized. The antiproliferative activity of these compounds was measured on hepatocellular carcinoma HepG2, leukemia HL-60, and breast cancer MCF-7 cell lines. The obtained results showed a substantial ability of the synthesized anilides to inhibit tumor growth. On HepG2 cells, 5o and 5r showed potent IC50 values of 0.10 and 0.04 μM, respectively. While on HL-60 cells, the IC50 values were 0.004 and 0.01 μM for 5b and 5i, respectively. The inhibitory activity of tubulin polymerization was evaluated on HepG2 cells. The anilide 5r showed a remarkable tubulin inhibition compared to CA-4. Moreover, flow cytometry studies showed that HepG2 cells treated with the most potent compounds 5b and 5r were arrested in the G2/M phase of the cell cycle. This effect was accompanied by cellular apoptosis and activation of caspase-3. Molecular modeling showed several hydrogen bonding and van der Waals interactions with several important amino acids inside the colchicine binding site of tubulin.

Oxazole-Bridged Combretastatin A-4 Derivatives with Tethered Hydroxamic Acids: Structure⁻Activity Relations of New Inhibitors of HDAC and/or Tubulin Function.

New inhibitors of tubulin polymerization and/or histone deacetylase (HDAC) activity were synthesized by attaching alkyl tethered hydroxamic acid appendages of varying length to oxazole-bridged combretastatin A-4 analogous caps. While their antiproliferative and microtubule disrupting effect was most pronounced for derivatives with short spacers, HDAC inhibition was strongest for those with longer spacers. These findings were further supported by computational methods such as structure-based docking experiments exploring the target interactions of the derivatives with varying linkers. For instance, compounds featuring short four-atom spacers between cap and hydroxamic acid inhibited the growth of various cancer cell lines and human endothelial hybrid cells with IC50 values in the low nanomolar range. In line with their ability to inhibit the microtubule assembly, four- and five-atom spacered hydroxamic acids caused an accumulation of 518A2 melanoma cells in G2/M phase, whereas a compound featuring a six-atom spacer and performing best in HDAC inhibition, induced a G1 arrest in these cells. All these beneficial anticancer activities together with their selectivity for cancer cells over non-malignant cells, point out the great potential of these novel pleiotropic HDAC and tubulin inhibitors as drug candidates for cancer therapy.

Полимеризация тубулина и его колхицинсвязывающая активность в различных структурах головного мозга в норме и при шизофрении

Introduction: abnormalities of neuronal cytoskeleton in mental disorders require to study microtubules and their proteins. Tubulin (the main protein of microtubules) has specific properties: reversibly polymerize into microtubules and bind mitotic poison colchicine in equimolar quantities. Objective: to evaluate the process of tubulin polymerization by light scattering change and to determine the level of colchicine binding (colchicine binding activity of tubulin) in various brain structures in healthy and schizophrenia brains. Material and methods: autopsy brain samples from patients with schizophrenia (n = 6) and from the control group (n = 9) were studied. Samples of the prefrontal (area 10), temporal (area 21), cingulate cortex (area 23/24) and thalamus were isolated (Brodmann's areas). Measurements of light scattering during tubulin polymerization and colchicine-binding activity of tubulin were determined as described earlier. Results: tubulin polymerization was not disturbed in schizophrenia as compared to controls, except for the cingulate cortex that showed slight but significant decrease in light scattering. At the same time, the binding of colchicine in schizophrenia was reduced in all examined areas of the cortex. This decrease was not associated with age, sex, and postmortem interval since the groups were matched by these factors. The tubulin colchicine-binding activity in thalamus remained at the same level both in control and schizophrenia, but it was lower than in the areas of the cortex. Conclusion: Decreased activity and hence decreased amount of tubulin in the cerebral cortical areas without changes of the tubulin polymerization in microtubules have been shown in schizophrenia. The results confirm the literature data on the changes in the cytoskeleton in cortical areas in schizophrenia.

Discovery of Novel 4-Arylisochromenes as Anticancer Agents Inhibiting Tubulin Polymerization.

XJP-L (8), a derivative of the natural product (±)-7,8-dihydroxy-3-methylisochroman-4-one isolated from the peel of Musa sapien tum L., was found to exhibit weak inhibitory activity of tubulin polymerization (IC50 = 10.6 μM) in our previous studies. Thus, a series of 4-arylisochromene derivatives were prepared by incorporating the trimethoxyphenyl moiety into 8, among which compound (±)-19b was identified as the most potent compound with IC50 values ranging from 10 to 25 nM against a panel of cancer cell lines. Further mechanism studies demonstrated that (±)-19b disrupted the intracellular microtubule network, caused G2/M phase arrest, induced cell apoptosis, and depolarized mitochondria of K562 cells. Moreover, (±)-19b exhibited potent in vitro antivascular and in vivo antitumor activities. Notably, the R-configured enantiomer of (±)-19b, which was prepared by chiral separation, was slightly more potent than (±)-19b and was much more potent than the S-configured enantiomer in both antiproliferative and antitubulin assays. Our findings suggest that (±)-19b deserves further research as a potential antitubulin agent for the treatment of cancers.

Design and Synthesis of Tubulin and Histone Deacetylase Inhibitor Based on iso-Combretastatin A-4.

Designing multitarget drugs have raised considerable interest due to their advantages in the treatment of complex diseases such as cancer. Their design constitutes a challenge in antitumor drug discovery. The present study reports a dual inhibition of tubulin polymerization and HDAC activity. On the basis of 1,1-diarylethylenes ( isoCA-4) and belinostat, a series of hybrid molecules was successfully designed and synthesized. In particular compounds, 5f and 5h were proven to be potent inhibitors of both tubulin polymerization and HDAC8 leading to excellent antiproliferative activity.

3-Aryl/Heteroaryl-5-amino-1-(3′,4′,5′-trimethoxybenzoyl)-1,2,4-triazoles as antimicrotubule agents. Design, synthesis, antiproliferative activity and inhibition of tubulin polymerization

Many natural and synthetic substances are known to interfere with the dynamic assembly of tubulin, preventing the formation of microtubules. In our search for potent and selective antitumor agents, a novel series of 1-(3′,4′,5′-trimethoxybenzoyl)-5-amino-1,2,4-triazoles were synthesized. The compounds had different heterocycles, including thiophene, furan or the three isomeric pyridines, and they possessed a phenyl ring bearing electron-releasing or electron-withdrawing substituents at the 3-position of the 5-amino-1,2,4-triazole system. Most of the twenty-two tested compounds showed moderate to potent antiproliferative activities against a panel of solid tumor and leukemic cell lines, with four (5j, 5k, 5o and 5p) showing strong antiproliferative activity (IC50 < 1 μM) against selected cancer cells. Among them, several molecules preferentially inhibited the proliferation of leukemic cell lines, showing IC50 values 2-100-fold lower for Jurkat and RS4;11 cells than those for the three lines derived from solid tumors (HeLa, HT-29 and MCF-7 cells). Compound 5k strongly inhibited tubulin assembly, with an IC50 value of 0.66 μM, half that obtained in simultaneous experiments with CA-4 (IC50 = 1.3 μM).

Synthesis and biological evaluation of (1-aryl-1H-pyrazol-4-yl) (3,4,5-trimethoxyphenyl)methanone derivatives as tubulin inhibitors

A series of (1-aryl-1H-pyrazol-4-yl) (3,4,5-trimethoxyphenyl)methanones (8a-p, 9a-p) and ketoxime (10c) derivatives were designed and synthesized as antitubulin agents. All of the target compounds were evaluated for the in vitro anti-proliferative activities against three tumor cell lines (A549, HT-1080, SGC-7901). The most promising compounds in this class were (1-(p-tolyl)-1H-pyrazol-4-yl) (3,4,5-trimethoxyphenyl)methanone (9c) and its ketoxime derivative (10c), which significantly inhibited tumor cells growth with IC50 value of 0.054–0.16 μM. Meanwhile, compound 9c exhibited effectively inhibitory activity of tubulin polymerization. Consistent with its antitubulin activity, compound 9c could destructively damage microtubule network and arrest SGC-7901 cell cycle at G2/M phase significantly. The structure-activity relationship (SAR) and conformational analysis indicate that methyl group at C4-position of C-ring is critical for the activities and the amino group at the C5-position of B-ring plays a negative role in maintaining bioactivity. Furthermore, a molecular docking study was performed to elucidate its binding mode at the colchicine site in the tubulin heterodimer.

Molecular modeling study, synthesis and biological evaluation of combretastatin A-4 analogues as anticancer agents and tubulin inhibitors.

As the major structural component of microtubules, tubulin is an interesting target for the development of anticancer agents. In this study, 64 tubulin polymerization inhibitors of five-membered heterocycle-based combretastatin A-4 analogues were studied by a combination of molecular modeling techniques including 3D-QSAR, molecular docking, and molecular dynamics (MD) simulation. The CoMFA (comparative molecular field analysis) and CoMSIA (comparative molecular similarity indices analysis) models were established with desirable statistical parameters and excellent predictive ability. 20 ns MD simulations were successfully performed to confirm the detailed binding mode and validate the rationality of docking results. Combining the binding free energy calculations and 3D-QSAR results, some new heterocycle-based combretastatin A-4 analogues were designed. Three of them were synthesized and biologically evaluated. Compound 13a displayed potent antiproliferative activity (IC50 value of 1.31 μM against HepG2 cells, IC50 value of 1.37 μM against A549 cells) and inhibition of tubulin polymerization activity (IC50 value of 0.86 μM). Compound 13b also presented good activity against HepG2 cells (IC50 value of 4.75 μM). The experimental results demonstrated that the built models were effective for the development of novel anticancer agents and tubulin inhibitors.