TR-644 a novel potent tubulin binding agent induces impairment of endothelial cells function and inhibits angiogenesis

Structure-Based Pharmacophore Design and Virtual Screening for Novel Tubulin Inhibitors with Potential Anticancer Activity

Tubulin inhibitors have been considered as potential drugs for cancer therapy. However, their drug resistance and serious side-effects are the main reasons for clinical treatment failure. Therefore, there is still an urgent need to develop effective therapeutic drugs. Herein, a structure-based pharmacophore model was developed based on the co-crystallized structures of the tubulin with a high resolution. The model including one hydrogen-bond acceptor feature, two aromatic features, and one hydrophobic feature was further validated using the Gunner-Henry score method. Virtual screening was performed by an integrated protocol that combines drug-likeness analysis, pharmacophore mapping, and molecular docking approaches. Finally, five hits were selected for biological evaluation. The results indicated that all these hits at the concentration of 40 μM showed an inhibition of more than 50% against five human tumor cells (MCF-7, U87MG, HCT-116, MDA-MB-231, and HepG2). Particularly, hit 1 effectively inhibited the proliferation of these tumor cells, with inhibition rates of more than 80%. The results of tubulin polymerization and colchicine-site competition assays suggested that hit 1 significantly inhibited tubulin polymerization by binding to the colchicine site. Thus, hit 1 could be used as a potential chemotherapeutic agent for cancer treatment. This work also demonstrated the potential of our screening protocol to identify biologically active compounds.

Design, Synthesis, and Biological Evaluation of 6-Substituted Thieno[3,2- d]pyrimidine Analogues as Dual Epidermal Growth Factor Receptor Kinase and Microtubule Inhibitors

The clinical evidence for the success of tyrosine kinase inhibitors in combination with microtubule-targeting agents prompted us to design and develop single agents that possess both epidermal growth factor receptor (EGFR) kinase and tubulin polymerization inhibitory properties. A series of 6-aryl/heteroaryl-4-(3',4',5'-trimethoxyanilino)thieno[3,2- d]pyrimidine derivatives were discovered as novel dual tubulin polymerization and EGFR kinase inhibitors. The 4-(3',4',5'-trimethoxyanilino)-6-( p-tolyl)thieno[3,2- d]pyrimidine derivative 6g was the most potent compound of the series as an antiproliferative agent, with half-maximal inhibitory concentration (IC₅₀) values in the single- or double-digit nanomolar range. Compound 6g bound to tubulin in the colchicine site and inhibited tubulin assembly with an IC₅₀ value of 0.71 μM, and 6g inhibited EGFR activity with an IC₅₀ value of 30 nM. Our data suggested that the excellent in vitro and in vivo profile of 6g may be derived from its dual inhibition of tubulin polymerization and EGFR kinase.

Antitubulin sulfonamides: The successful combination of an established drug class and a multifaceted target

Tubulin, the microtubules and their dynamic behavior are amongst the most successful antitumor, antifungal, antiparasitic, and herbicidal drug targets. Sulfonamides are exemplary drugs with applications in the clinic, in veterinary and in the agrochemical industry. This review summarizes the actual state and recent progress of both fields looking from the double point of view of the target and its drugs, with special focus onto the structural aspects. The article starts with a brief description of tubulin structure and its dynamic assembly and disassembly into microtubules and other polymers. Posttranslational modifications and the many cellular means of regulating and modulating tubulin's biology are briefly presented in the tubulin code. Next, the structurally characterized drug binding sites, their occupying drugs and the effects they induce are described, emphasizing on the structural requirements for high potency, selectivity, and low toxicity. The second part starts with a summary of the favorable and highly tunable combination of physical-chemical and biological properties that render sulfonamides a prototypical example of privileged scaffolds with representatives in many therapeutic areas. A complete description of tubulin-binding sulfonamides is provided, covering the different species and drug sites. Some of the antimitotic sulfonamides have met with very successful applications and others less so, thus illustrating the advances, limitations, and future perspectives of the field. All of them combine in a mechanism of action and a clinical outcome that conform efficient drugs.

Dual-targeting antitumor hybrids derived from Pt(IV) species and millepachine analogues

Many strategies have been developed to circumvent the shortcomings of Pt(II)-based chemotherapy, but the inherent problems still have not been effectively resolved. Here we report a new series of dual-targeting Pt(IV) prodrugs, conjugates of millepachine analogues with the related Pt(IV) complexes derived from cisplatin or oxaliplatin, respectively, which can inhibit tubulin polymerization and induce DNA damage. Among them, compound 19 possessed excellent antitumor activities against the tested human cancer cell lines, and arrested the cell cycle at the G2/M phases and ultimately induced cell apoptosis. Interestingly, its low cytotoxicity toward two human normal cells and sensitivity toward two cisplatin-resistant cells revealed the possibility for cancer therapy. More importantly, 19 displayed excellent antitumor efficacy in the SK-OV-3 xenograft model better than cisplatin and the corresponding millepachine analogue. Our research provided an efficient strategy for multi-targeting antitumor drug development.

Desacetylvinblastine Monohydrazide Disrupts Tumor Vessels by Promoting VE-cadherin Internalization

Vinca alkaloids, the well-known tubulin-binding agents, are widely used for the clinical treatment of malignant tumors. However, little attention has been paid to their vascular disrupting effects, and the underlying mechanisms remain largely unknown. This study aims to investigate the vascular disrupting effect and the underlying mechanisms of vinca alkaloids.

Methods: The capillary disruption assay and aortic ring assay were performed to evaluate the in vitro vascular disrupting effect of desacetylvinblastine monohydrazide (DAVLBH), a derivate of vinblastine, and the in vivo vascular disrupting effect was assessed on HepG2 xenograft model using magnetic resonance imaging, hematoxylin and eosin staining and immunohistochemistry. Tubulin polymerization, endothelial cell monolayer permeability, western blotting and immunofluorescence assays were performed to explore the underlying mechanisms of DAVLBH-mediated tumor vascular disruption.

Results: DAVLBH has potent vascular disrupting activity both in vitro and in vivo. DAVLBH disrupts tumor vessels in a different manner than classical tubulin-targeting VDAs; it inhibits microtubule polymerization, promotes the internalization of vascular endothelial cadherin (VE-cadherin) and inhibits the recycling of internalized VE-cadherin to the cell membrane, thus increasing endothelial cell permeability and ultimately resulting in vascular disruption. DAVLBH-mediated promotion of VE-cadherin internalization and inhibition of internalized VE-cadherin recycling back to the cell membrane are partly dependent on inhibition of microtubule polymerization, and Src activation is involved in DAVLBH-induced VE-cadherin internalization.

Conclusions: This study sheds light on the tumor vascular disrupting effect and underlying mechanisms of vinca alkaloids and provides new insight into the molecular mechanism of tubulin-targeting VDAs.

Synthesis and Biological Evaluation of 2-Methyl-4,5-Disubstituted Oxazoles as a Novel Class of Highly Potent Antitubulin Agents

Antimitotic agents that interfere with microtubule formation are one of the major classes of cytotoxic drugs for cancer treatment. Multiple 2-methyl-4-(3′,4′,5′-trimethoxyphenyl)-5-substituted oxazoles and their related 4-substituted-5-(3′,4′,5′-trimethoxyphenyl) regioisomeric derivatives designed as cis-constrained combretastatin A-4 (CA-4) analogues were synthesized and evaluated for their antiproliferative activity in vitro against a panel of cancer cell lines and, for selected highly active compounds, interaction with tubulin, cell cycle effects and in vivo potency. Both these series of compounds were characterized by the presence of a common 3′,4′,5′-trimethoxyphenyl ring at either the C-4 or C-5 position of the 2-methyloxazole ring. Compounds 4g and 4i, bearing a m-fluoro-p-methoxyphenyl or p-ethoxyphenyl moiety at the 5-position of 2-methyloxazole nucleus, respectively, exhibited the greatest antiproliferative activity, with IC₅₀ values of 0.35-4.6 nM (4g) and 0.5–20.2 nM (4i), which are similar to those obtained with CA-4. These compounds bound to the colchicine site of tubulin and inhibited tubulin polymerization at submicromolar concentrations. Furthermore, 4i strongly induced apoptosis that follows the mitochondrial pathway. In vivo, 4i in a mouse syngeneic model demonstrated high antitumor activity which significantly reduced the tumor mass at doses ten times lower than that required for CA-4P, suggesting that 4i warrants further evaluation as a potential anticancer drug.

ZLM-7 exhibits anti-angiogenic effects via impaired endothelial cell function and blockade of VEGF/VEGFR-2 signaling

Inhibition of angiogenesis is a promising therapeutic strategy against cancer. In this study, we reported that ZLM-7, a combretastain A-4 (CA-4) derivative, exhibited anti-angiogenic activity in vitro and in vivo. In vitro, ZLM-7 induced microtubule cytoskeletal disassembly. It decreased VEGF-induced proliferation, migration, invasion and tube formation in endothelial cells, which are critical steps in angiogenesis. In vivo, ZLM-7 significantly inhibited neovascularization in a chicken chorioallantoic membrane (CAM) model and reduced the microvessel density in tumor tissues of MCF-7 xenograft mouse model. ZLM-7 also displayed comparable antiangiogenic and anti-tumor activities associated with the lead compound CA-4, but exhibited lower toxicity compared with CA-4. The anti-angiogenic effect of ZLM-7 was exerted via blockade of VEGF/VEGFR-2 signaling. ZLM-7 treatment suppressed the expression and secretion of VEGF in endothelial cells and MCF-7 cells under hypoxia. Further, ZLM-7 suppressed the VEGF-induced phosphorylation of VEGFR-2 and its downstream signaling mediators including activated AKT, MEK and ERK in endothelial cells. Overall, these results demonstrate that ZLM-7 exhibits anti-angiogenic activities by impairing endothelial cell function and blocking VEGF/VEGFR-2 signaling, suggesting that ZLM-7 might be a potential angiogenesis inhibitor.

Current Advances of Tubulin Inhibitors in Nanoparticle Drug Delivery and Vascular Disruption/Angiogenesis

Extensive research over the last decade has resulted in a number of highly potent tubulin polymerization inhibitors acting either as microtubule stabilizing agents (MSAs) or microtubule destabilizing agents (MDAs). These inhibitors have potent cytotoxicity against a broad spectrum of human tumor cell lines. In addition to cytotoxicity, a number of these tubulin inhibitors have exhibited abilities to inhibit formation of new blood vessels as well as disrupt existing blood vessels. Tubulin inhibitors as a vascular disrupting agents (VDAs), mainly from the MDA family, induce rapid tumor vessel occlusion and massive tumor necrosis. Thus, tubulin inhibitors have become increasingly popular in the field of tumor vasculature. However, their pharmaceutical application is halted by a number of limitations including poor solubility and toxicity. Thus, recently, there has been considerable interests in the nanoparticle drug delivery of tubulin inhibitors to circumvent those limitations. This article reviews recent advances in nanoparticle based drug delivery for tubulin inhibitors as well as their tumor vasculature disruption properties.

The Novel Antitubulin Agent TR-764 Strongly Reduces Tumor Vasculature and Inhibits HIF-1α Activation

Tubulin binding agents (TBAs) are commonly used in cancer therapy as antimitotics. It has been described that TBAs, like combretastatin A-4 (CA-4), present also antivascular activity and among its derivatives we identified TR-764 as a new inhibitor of tubulin polymerization, based on the 2-(alkoxycarbonyl)-3-(3',4',5'-trimethoxyanilino)benzo[b]thiophene molecular skeleton. The antiangiogenic activity of TR-764 (1-10 nM) was tested in vitro on human umbilical endothelial cells (HUVECs), and in vivo, on the chick embryo chorioallantoic membrane (CAM) and two murine tumor models. TR-764 binding to tubulin triggers cytoskeleton rearrangement without affecting cell cycle and viability. It leads to capillary tube disruption, increased cell permeability, and cell motility reduction. Moreover it disrupts adherens junctions and focal adhesions, through mechanisms involving VE-cadherin/β-catenin and FAK/Src. Importantly, TR-764 is active in hypoxic conditions significantly reducing HIF-1α. In vivo TR-764 (1-100 pmol/egg) remarkably blocks the bFGF proangiogenic activity on CAM and shows a stronger reduction of tumor mass and microvascular density both in murine syngeneic and xenograft tumor models, compared to the lead compound CA-4P. Altogether, our results indicate that TR-764 is a novel TBA with strong potential as both antivascular and antitumor molecule that could improve the common anticancer therapies, by overcoming hypoxia-induced resistance mechanisms.

Design, synthesis, crystallization and biological evaluation of new symmetrical biscationic compounds as selective inhibitors of human Choline Kinase α1 (ChoKα1)

A novel family of compounds derivative of 1,1′-(((ethane-1,2-diylbis(oxy))bis(4,1-phenylene))bis(methylene))-bispyridinium or –bisquinolinium bromide (10a-l) containing a pair of oxygen atoms in the spacer of the linker between the biscationic moieties, were synthesized and evaluated as inhibitors of choline kinase against a panel of cancer-cell lines. The most promising compounds in this series were 1,1′-(((ethane-1,2-diylbis(oxy))bis(4,1-phenylene))bis(methylene))bis(4-(dimethylamino)pyridinium) bromide (10a) and 1,1′-(((ethane-1,2-diylbis(oxy))bis(4,1-phenylene))bis(methylene))-bis(7-chloro-4-(pyrrolidin-1-yl)quinolinium) bromide (10l), which inhibit human choline kinase (ChoKα1) with IC₅₀ of 1.0 and 0.92 μM, respectively, in a range similar to that of the previously reported biscationic compounds MN58b and RSM932A. Our compounds show greater antiproliferative activities than do the reference compounds, with unprecedented values of GI₅₀ in the nanomolar range for several of the cancer-cell lines assayed, and more importantly they present low toxicity in non-tumoral cell lines, suggesting a cancer-cell-selective antiproliferative activity. Docking studies predict that the compounds interact with the choline-binding site in agreement with the binding mode of most previously reported biscationic compounds. Moreover, the crystal structure of ChoKα1 with compound 10a reveals that this compound binds to the choline-binding site and mimics HC-3 binding mode as never before.

A tool for the quantification of radial neo-vessels in chick chorioallantoic membrane angiogenic assays

Angiogenesis, the process of new blood vessels formation, plays a key role in different physiological and pathological conditions and it is considered a promising target for the development of new anti-inflammatory and anti-tumor therapies. Several assays have been developed to mimic the angiogenic process in vitro and in vivo. Here we propose a technique for the quantification of the pro-angiogenic or anti-angiogenic responses induced by different molecules when implanted in vivo on the chick embryo chorioallantoic membrane (CAM). At day 11 of development CAM is completely vascularized and neo-vessels induced by exogenous molecules converge radially to the implant. Our algorithm is an effective and rapid tool to characterize molecules endowed with proor anti-angiogenic effects by means of the quantification of the vessels present in the CAM macroscopic images. Based on conventional and dedicated image morphology tools, the proposed technique is able to discriminate radial from non-radial vessels, excluding the last ones from the count.

New more polar symmetrical bipyridinic compounds: new strategy for the inhibition of choline kinase α1

AIM

Research of the antitumor properties of biscationic compounds has received significant attention over the last few years.

RESULTS

A novel family of 1,1'-([2,2'-bipyridine]-5,5'-diylbis(methylene))bis-substituted bromide (9a-k), containing two nitrogen atoms in the linker, considered as hypothetical hydrogen bond acceptors, were synthesized and evaluated as ChoK inhibitors and their antiproliferative activity against six cancer cell lines.

CONCLUSION

The most promising compounds in this series are 1,1'-([2,2'-bipyridine]-5,5'-diylbis(methylene))bis(4-(methyl(phenyl)amino)-quinolinium bromide derivatives 9g-i (analogs to RSM932A), that significantly inhibit cancer cell growth at even submicromolar concentrations, especially against leukemia cells. Compounds 9g-i also inhibit the ChoKα1 with good or moderate values, as predicted by initial docking studies. In addition, the most active compound 9h remarkably induces apoptosis in two cell lines following the mitochondrial pathway.

Novel Etoposide Analogue Modulates Expression of Angiogenesis Associated microRNAs and Regulates Cell Proliferation by Targeting STAT3 in Breast Cancer

Tumor microenvironment play role in angiogenesis and carcinogenesis. Etoposide, a known topoisomerase II inhibitor induces DNA damage resulting in cell cycle arrest. We developed a novel Etoposide analogue, Quinazolino-4β-amidopodophyllotoxin (C-10) that show better efficacy in regulating cell proliferation and angiogenesis. We evaluated its role on expression of microRNAs-15, 16, 17 and 221 and its targets Bcl-2, STAT3 and VEGF that dictate cell proliferation and angiogenesis. Docking studies clearly demonstrated the binding of Etoposide and C-10 to STAT3. We conclude that combination of Etoposide or C-10 with miR-15, 16, 17 and 221 as a new approach to induce apoptosis and control angiogenesis in breast cancer.

Novel 3-Substituted 7-Phenylpyrrolo[3,2-f]quinolin-9(6H)-ones as Single Entities with Multitarget Antiproliferative Activity

A series of chemically modified 7-phenylpyrrolo[3,2-f]quinolinones was synthesized and evaluated as anticancer agents. Among them, the most cytotoxic (subnanomolar GI50 values) amidic derivative 5f was shown to act as an inhibitor of tubulin polymerization (IC50, 0.99 μM) by binding to the colchicine site with high affinity. Moreover, 5f induced cell cycle arrest in the G2/M phase of the cell cycle in a concentration dependent manner, followed by caspase-dependent apoptotic cell death. Compound 5f also showed lower toxicity in nontumoral cells, suggesting selectivity toward cancer cells. Additional experiments revealed that 5f inhibited the enzymatic activity of multiple kinases, including AURKA, FLT3, GSK3A, MAP3K, MEK, RSK2, RSK4, PLK4, ULK1, and JAK1. Computational studies showed that 5f can be properly accommodated in the colchicine binding site of tubulin as well as in the ATP binding clefts of all examined kinases. Our data indicate that the excellent antiproliferative profile of 5f may be derived from its interactions with multiple cellular targets.

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.

Recent advances in vascular disrupting agents in cancer therapy

Vascular disrupting agents (VDAs) are an important class of compounds that exhibit selective activity against pre-existing tumor vasculature, causing rapid shutdown of the tumor blood flow and consequent necrosis of the tumor mass. The VDAs can be divided into flavonoid compounds, which are related to flavone acetic acid, and tubulin-binding agents. Tubulin-binding agents represent the largest group of VDAs and are characterized by different chemical structures, although most of them are derivatives of the lead compound combretastatin (CA-4). They demonstrated clinical activity, although recent findings have established that they have insufficient activity as single agents. Several resistance mechanisms occur, such as the resistance of the tumor rim cells, while promising results have been described in combination with other chemotherapeutics.

AECHL-1, a novel triterpenoid, targets tumor neo-vasculature and impairs the endothelial cell cytoskeleton

Tumor angiogenesis is characterized by abnormal vessel morphology leading to erratic and insufficient delivery of chemotherapeutics and oxygen, making the tumor core not only highly hypoxic but also unresponsive toward treatment. Such hypoxic conditions promote tumor aggressiveness, leading to the establishment of metastatic disease. Most anti-angiogenic treatments aim toward the destruction of tumor vasculature, which proves countereffective by further increasing its aggressive nature. Hence, developing drugs which target or regulate these processes might lead to a better delivery of chemotherapeutics resulting in tumor shrinkage. Plant-derived natural compounds having a bioactive ingredient, especially triterpenoids, have been known to possess anticancer properties. AECHL-1, a recently isolated novel triterpenoid with proven anticancer potential, is seemingly noncytotoxic toward HEK 293 and HUVECs. Also, cytotoxicity was absent during in vivo studies involving intraperitoneal injections with 5 µg/kg body weight AECHL-1 on SCID mice. When used at subtoxic doses, it was found to be effective in suppression of neo-vessel formation as demonstrated in the chick chorioallantoic membrane, rat aortic rings, Matrigel plugs and xenograft tumors implanted in SCID mice. Tumor vasculature from AECHL-1-treated mice showed greater mural cell coverage and relatively normalized architecture. Investigations into the molecular mechanisms responsible for these observations revealed an effect on the actin cytoskeleton of stimulated HUVECs as well as the VEGFR2-mediated MAPK pathway. AECHL-1 could effectively distinguish between stimulated and nonstimulated endothelial cells. AECHL-1 could also downregulate HIF-1α expression and VEGF secretion under hypoxic conditions, thus reducing the fears of unnecessarily aggravating tumor metastasis as a result of anti-angiogenic therapy. Results obtained from the aforementioned studies make it clear that though AECHL-1 shows promise in discouraging and pruning neo-vasculature, it may not affect existing vasculature as the doses used for the assays are significantly lower than the ones causing endothelial cell death and has potential to be considered as a candidate for therapeutic drug development.

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.

Synthesis and biological evaluation of N-(4-phenylthiazol-2-yl)cinnamamide derivatives as novel potential anti-tumor agents

In this study, a series of novel N-(4-phenylthiazol-2-yl)-cinnamamide derivatives (7a–8n) were synthesized and evaluated for their anti-proliferative activities in vitro.

Synthesis, antimitotic and antivascular activity of 1-(3',4',5'-trimethoxybenzoyl)-3-arylamino-5-amino-1,2,4-triazoles

A new class of compounds that incorporated the structural motif of the 1-(3',4',5'-trimethoxtbenzoyl)-3-arylamino-5-amino-1,2,4-triazole molecular skeleton was synthesized and evaluated for their antiproliferative activity in vitro, interactions with tubulin, and cell cycle effects. The most active agent, 3c, was evaluated for antitumor activity in vivo. Structure-activity relationships were elucidated with various substituents on the phenyl ring of the anilino moiety at the C-3 position of the 1,2,4-triazole ring. The best results for inhibition of cancer cell growth were obtained with the p-Me, m,p-diMe, and p-Et phenyl derivatives 3c, 3e, and 3f, respectively, and overall, these compounds were more or less as active as CA-4. Their vascular disrupting activity was evaluated in HUVEC cells, with compound 3c showing activity comparable with that of CA-4. Compound 3c almost eliminated the growth of syngeneic hepatocellular carcinoma in Balb/c mice, suggesting that 3c could be a new antimitotic agent with clinical potential.

Antiangiogenic activity of hypoxylonol C

Hypoxylonol C (1), isolated from the inedible mushroom Hypoxylon truncatum, exhibited inhibitory activities against the migration and tube formation of HUVECs. A cDNA microarray analysis was performed to investigate the target of hypoxylonol C (1) in HUVECs, and it was found that the genes related to cell cycle and adhesion were down-regulated. The down-regulation of mRNA levels of cell cycle and adhesion genes was confirmed by real-time RT-PCR. Cell cycle arrest and suppression of adhesion molecule expression might be plausible mechanisms of actions for the antiangiogenic activity of hypoxylonol C (1).

Concise synthesis and biological evaluation of 2-Aroyl-5-amino benzo[b]thiophene derivatives as a novel class of potent antimitotic agents

The biological importance of microtubules make them an interesting target for the synthesis of antitumor agents. The 2-(3',4',5'-trimethoxybenzoyl)-5-aminobenzo[b]thiophene moiety was identified as a novel scaffold for the preparation of potent inhibitors of microtubule polymerization acting through the colchicine site of tubulin. The position of the methoxy group on the benzo[b]thiophene was important for maximal antiproliferative activity. Structure-activity relationship analysis established that the best activities were obtained with amino and methoxy groups placed at the C-5 and C-7 positions, respectively. Compounds 3c-e showed more potent inhibition of tubulin polymerization than combretastatin A-4 and strong binding to the colchicine site. These compounds also demonstrated substantial antiproliferative activity, with IC50 values ranging from 2.6 to 18 nM in a variety of cancer cell lines. Importantly, compound 3c (50 mg/kg), significantly inhibited the growth of the human osteosarcoma MNNG/HOS xenograft in nude mice.