Inhibitors of Mitotic Kinesins: Next-Generation Antimitotics

Synthesis of Novel 3,4-Dihydropyrimidine Derivatives, Cytotoxic Activity Evaluation, Apoptosis, Molecular Docking Studies, and MD Simulations

In this study, twelve 3,4-dihydropyrimidines derivatives were synthesized through Biginelli multi-component reaction. The efficacy of these compounds against MCF-7, A549, and HeLa cells was evaluated using the MTT method. The results showed that designed derivatives were more effective against A549 cancer cells than MCF-7 and HeLa cells. Compound 5l (bearing 4-Cl-phenyl at C4 of 3, 4-dihydropyrimidin-2(1H)-one ring) was the most potent analogue (A549: 18.65±1.87 μM, HeLa: 26.59±2.71 μM, MCF-7: 31.82±2.64 μM). The presence of an electron-withdrawing group with optimum lipophilicity at the C4 position of the phenyl ring increased the cytotoxic effect. The flow cytometry findings indicated that compound 5l induced apoptosis in A549 cancer cells in a dose-dependent manner. Eg5 and AKT1 were selected as molecular modeling target by applying pharmacology network analyses. The molecular docking results indicated that both enantiomers of compound 5l had significant interactions with key residues in both Eg5 (Gly117 and Glu116) and AKT1 (Ala123 and Glu121) active sites. However, MD simulation revealed that the R enantiomer had a more stable complex and a higher binding affinity to the Eg5 enzyme active site than the S-enantiomer. The affinity of 5l (R enantiomer) to Eg5 was predicted more than AKT1.

In vitro antitumor activity, molecular dynamics simulation, DFT study, ADME prediction, and Eg5 binding of enastron analogues

The objective of this study is to evaluate a series of molecules based on cyclosulfamide as potential anticancer agents. Additionally, the study aims to analyze the obtained results through in silico studies; by conducting experiments and utilizing theoretical methods. In this context, we investigated the cytotoxic activity of enastron analogues on three human cell lines PRI (lymphoblastic cell line) derived from B-cell lymphoma. JURKAT (ATCC TIB-152) acute T cell leukaemia and K562 (ATCC CLL-243) is a chronic myelogenous leukaemia. Most of the tested compounds showed good inhibitory activity compared with the reference ligand (chlorambucil). The 5a derivative demonstrated the strongest effect against all cancer cells used. Furthermore, molecular docking simulations of the Eg5-enastron analogue complex revealed that studied molecules have the ability to inhibit the Eg5 enzyme, as evidenced by their calculated docking score. Following the promising results from the molecular docking study, the complex Eg5-4a underwent a 100 ns molecular dynamics simulation using Desmond. During the simulation, the receptor-ligand pairing demonstrated substantial stability after the initial 70 ns. In addition, we used DFT calculations to analyze the electronic and geometric characteristics of the studied compounds. The HOMO and LUMO band gap energies, and the molecular electrostatic potential surface were also deducted for the stable structure of each compound. Also, we studied the prediction of absorption, distribution, metabolism and excretion (ADME) of the compounds.

KIF20A promotes the development of fibrosarcoma via PI3K-Akt signaling pathway

Adult fibrosarcoma is an aggressive subtype of soft tissue sarcoma (STS), in which high expression of KIF20A indicates a poor prognosis. However, the precise role of KIF20A in fibrosarcoma progression remains unknown. In this study, we initially examined KIF20A expression and function in the human fibrosarcoma cell line HT-1080. The results showed that KIF20A was highly expressed in HT-1080, knockdown of KIF20A impaired cell proliferation, migration, invasion and induced G2/M arrest and cell apoptosis. Transcriptome study suggested that PI3K-Akt signal pathway was involved in these biological changes. We confirmed that PI3K-Akt and NF-κB signaling pathways were impaired after the down-regulation of KIF20A, which can be reversed by the Akt activator SC79 in HT-1080 in vitro. In a xenograft mouse model, knockdown of KIF20A inhibited tumor growth, Ki67 expression and liver metastasis. Taken together, our results suggested that KIF20A promoted fibrosarcoma progression via PI3K-Akt signaling pathway and might be a potential therapeutic target for fibrosarcoma.

Molecular mechanisms and differences in lynch syndrome developing into colorectal cancer and endometrial cancer based on gene expression, methylation, and mutation analysis

Purpose

The aim of this study was to screen biomarkers specific to Lynch syndrome (LS) with colorectal cancer (CRC) or endometrial cancer (EC) to explore the mechanisms by which LS develops into CRC and EC and their differences.

Methods

Differentially expressed or differentially methylated genes and differential mutations were identified in 10 LS, 50 CRC, and 50 EC patients from TCGA, and genes overlapping between LS and CRC or EC (named SGs-LCs and SGs-LEs, respectively) were identified. Afterward, we annotated the enriched GO terms and pathways and constructed a protein–protein interaction (PPI) network. Finally, samples from 10 clinical cases with MSI-H/MSS CRC and EC were collected to verify the mutations and their correlations with five LS pathogenic genes in the SGs-LCs and SGs-LEs.

Results

A total of 494 SGs-LCs and 104 SGs-LEs were identified and enriched in 106 and 14 GO terms, respectively. There were great differences in the gene count and enriched terms between SGs-LCs and SGs-LEs. In the PPI network, SST, GCG, SNAP25, and NPY had the highest degree of connection among the SGs-LCs, and KIF20A and NUF2 had the highest degree of connection among the SGs-LE. In the SGs-LCs and SGs-LEs, the genes whose expression levels affected the survival of LS, CRC or EC patients were quite different.

Conclusions

COL11A1 was found to be mutated in MSS CRC patients, similar to the mutations of MSH6. SST, GCG, SNAP25, and NPY may be biomarkers for the development of LS into CRC, and KIF20A and NUF2 may be markers of LS developing into EC.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10552-021-01543-w.

Kolaflavanone, a biflavonoid derived from medicinal plant Garcinia, is an inhibitor of mitotic kinesin Eg5

Mitotic kinesin Eg5 remains a validated target in antimitotic therapy because of its essential role in the formation and maintenance of bipolar mitotic spindles. Although numerous Eg5 inhibitors of synthetic origin are known, only a few inhibitors derived from natural products have been reported. In our study, we focused on identifying novel Eg5 inhibitors from medicinal plants, particularly Garcinia species. Herein, we report the inhibitory effect of kolaflavanone (KLF), a Garcinia biflavonoid, on the ATPase and microtubule-gliding activities of mitotic kinesin Eg5. Additionally, we showed the interaction mechanism between Eg5 and KLF via in vitro and in silico analyses. The results revealed that KLF inhibited both the basal and microtubule-activated ATPase activities of Eg5. The inhibitory mechanism is allosteric, without a direct competition with adenosine-5'-diphosphate for the nucleotide-binding site. KLF also suppressed the microtubule gliding of Eg5 in vitro. The Eg5-KLF model obtained from molecular docking showed that the biflavonoid exists within the α2/α3/L5 (α2: Lys111-Glu116 and Ile135-Asp149, α3: Asn206-Thr226; L5: Gly117-Gly134) pocket, with a binding pose comparable to known Eg5 inhibitors. Overall, our data suggest that KLF is a novel allosteric inhibitor of mitotic kinesin Eg5.

Inhibition of kinesin motor protein KIFC1 by AZ82 induces multipolar mitosis and apoptosis in prostate cancer cell

Kinesin 14 family member KIFC1 is a mitotic kinesin which contains a C-terminal motor domain and plays a vital role for clustering the amplified centrosomes. Overexpression of KIFC1 in prostate cancer (PCa) cells showed resistance to docetaxel (DTX). The present study revealed that small KIFC1 inhibitor AZ82 suppresed the transcription and translation of KIFC1 significantly in PCa cells. AZ82 inhibited the KIFC1 expression both in the cytoplasm and nucleus of PCa cells. Inhibition of KIFC1 by AZ82 caused multipolar mitosis in PCa cells via de-clustering the amplified centrosomes and decreased the rate of cancer cell growth and proliferation. Moreover, depletion of KIFC1 reduced cells entering the cell cycle and caused PCa cells death through apoptosis by increasing the expression of Bax and Cytochrome C. Thereby, KIFC1 silencing and inhibition decreased the PCa cells survival by inducing multipolar mitosis as well as apoptosis, suggesting inhibition of KIFC1 using AZ82 might be a strategy to treat PCa by controlling the cancer cell proliferation.

Design, synthesis, and molecular docking study of new monastrol analogues as kinesin spindle protein inhibitors

Lung, colorectal, and breast cancers are the top three types of cancer by incidence and are responsible for one-third of the cancer incidence and mortality. A series of 18 3,4-dihydropyrimidine analogues bearing a 1,2-methylenedioxybenzene component at position 4 with diverse side chains at positions 5 and 6 was designed and synthesized as inhibitors of the Eg5 kinesin enzyme. Target compounds were screened for their anticancer activity according to the NCI-USA protocol toward a panel of 60 cancer cell lines. Compounds 12a and 12b displayed the best antiproliferation activity against many cell lines. Interestingly, compound 12a displayed lethal effects against non-small-cell lung cancer NCI-H522 cells (-42.26%) and MDA-MB-468 breast cancer cells (-1.10%) at a single-dose assay concentration of 10^-5  M. Compounds 11c, 11d, 11g, 12a-d, 13, 15, and 18a were assayed against the kinesin enzyme, with IC₅₀ values ranging from 1.2 to 18.71 μM, which were more potent compared with monastrol (IC₅₀  = 20 μM). Cell cycle analysis of NCI-H522 cells treated with compound 12a showed cell cycle arrest at the G2/M phase. Furthermore, the expression levels of active caspase-3 and -9 were measured. A molecular docking study was performed for some demonstrative compounds as well as monastrol docked into the allosteric binding site of the kinesin spindle protein.

Identification of potential key genes for HER-2 positive breast cancer based on bioinformatics analysis

BACKGROUNDS

HER-2 positive breast cancer is a subtype of breast cancer with poor clinical outcome. The aim of this study was to identify differentially expressed genes (DEGs) for HER-2 positive breast cancer and elucidate the potential interactions among them.

MATERIAL AND METHODS

Three gene expression profiles (GSE29431, GSE45827, and GSE65194) were derived from the Gene Expression Omnibus (GEO) database. GEO2R tool was applied to obtain DEGs between HER-2 positive breast cancer and normal breast tissues. Gene ontology (GO) annotation analysis and Kyoto Encyclopedia of Genes and Genome (KEGG) pathway enrichment analysis was performed by the Database for Annotation, Visualization and Integrated Discovery (David) online tool. Protein-protein interaction (PPI) network, hub gene identification and module analysis was conducted by Cytoscape software. Online Kaplan-Meier plotter survival analysis tool was also used to investigate the prognostic values of hub genes in HER-2 positive breast cancer patients.

RESULTS

A total of 54 upregulated DEGs and 269 downregulated DEGs were identified. Among them, 10 hub genes including CCNB1, RAC1, TOP2A, KIF20A, RRM2, ASPM, NUSAP1, BIRC5, BUB1B, and CEP55 demonstrated by connectivity degree in the PPI network were screened out. In Kaplan-Meier plotter survival analysis, the overexpression of RAC1 and RRM2 were shown to be associated with an unfavorable prognosis in HER-2 positive breast cancer patients.

CONCLUSIONS

This present study identified a number of potential target genes and pathways which might impact the oncogenesis and progression of HER-2 positive breast cancer. These findings could provide new insights into the detection of novel diagnostic and therapeutic biomarkers for this disease.

Growth arrest and apoptosis induced by kinesin Eg5 inhibitor K858 and by its 1,3,4-thiadiazoline analogue in tumor cells

Tumors are complex and heterogeneous but, despite this, they share the ability to proliferate continuously, irrespective of the presence of growth signals, leading to a higher fraction of actively growing and dividing cells compared with normal tissues. For this reason, the cytotoxic antimitotic treatments remain an important clinical tool for tumors. Among these drugs, antitubulin compounds constitute one of the most effective anticancer chemotherapies; however, they cause dose-limiting side effects. Therefore, it is still necessary to develop compounds with new targets and new mechanisms of action to reduce side effects or chemoresistance. Mitosis-specific kinesin Eg5 can represent an attractive target for discovering such new anticancer agents because its role is fundamental in mitotic progression. Therefore, we analyzed the effects induced by an inhibitor of kinesin Eg5, K858, and by its 1,3,4-thiadiazoline analogue on human melanoma and prostate cancer cell lines. We found that both compounds have an antiproliferative effect, induce apoptosis, and can determine a downmodulation of survivin.

Positive expression of KIF20A indicates poor prognosis of glioma patients

Glioma patients have a poor overall survival; however, patients can show distinct clinical outcomes due to the high heterogeneity of the tumor, which may be indicated by certain clinicobiological parameters. Kinesin family member 20A (KIF20A), which participates in cytokinesis and intracellular transportation, has been recently reported to be upregulated in pancreatic cancer, breast cancer, and bladder cancer. In the current study, we investigated the expression of KIF20A in gliomas and its significance in predicting the prognosis after surgery. We found that KIF20A positive expression in glioma tissues correlated significantly with Ki67 protein expression and advanced World Health Organization grade. Univariate and multivariate analysis revealed that KIF20A can act as an independent prognostic factor for predicting the overall survival of glioma patients. Moreover, we demonstrated that KIF20A can positively regulate the expression of Ki67 in glioma cell lines. Correspondingly, overexpression of KIF20A can promote cell proliferation and invasion, whereas knockdown of KIF20A can inhibit cell viability and invasion capacity. In vitro study also showed that under the treatment of plumbagin, an anticancer drug, KIF20A expression decreased in a dose-dependent manner. In addition, the overexpression of KIF20A can also increase the drug resistance toward plumbagin, which provided the possibility that KIF20A may contribute to the chemotherapy resistance of gliomas.

Ubiquitin ligase RNF20/40 facilitates spindle assembly and promotes breast carcinogenesis through stabilizing motor protein Eg5

Whether transcriptional regulators are functionally involved in mitosis is a fundamental question in cell biology. Here we report that the RNF20/40 complex, a major ubiquitin ligase catalysing histone H2B monoubiquitination, interacts with the motor protein Eg5 during mitosis and participates in spindle assembly. We show that the RNF20/40 complex monoubiquitinates and stabilizes Eg5. Loss of RNF20/40 results in spindle assembly defects, cell cycle arrest and apoptosis. Consistently, depletion of either RNF20/40 or Eg5 suppresses breast cancer in vivo. Significantly, RNF20/40 and Eg5 are concurrently upregulated in human breast carcinomas and high Eg5 expression is associated with poorer overall survival of patients with luminal A, or B, breast cancer. Our study uncovers an important spindle assembly role of the RNF20/40 complex, and implicates the RNF20/40-Eg5 axis in breast carcinogenesis, supporting the pursuit of these proteins as potential targets for breast cancer therapeutic interventions.

Eg5 has a role in spindle assembly and has been associated with tumorigenesis but it is not clear how its activity is regulated. Here, the authors show that the E3 ligase RNF20/40 regulates mitotic spindle assembly by regulating the stability of Eg5 through mono-ubiquitination of K745.

Discovery of a novel inhibitor of kinesin-like protein KIFC1

Historically, drugs used in the treatment of cancers also tend to cause damage to healthy cells while affecting cancer cells. Therefore, the identification of novel agents that act specifically against cancer cells remains a high priority in the search for new therapies. In contrast with normal cells, most cancer cells contain multiple centrosomes which are associated with genome instability and tumorigenesis. Cancer cells can avoid multipolar mitosis, which can cause cell death, by clustering the extra centrosomes into two spindle poles, thereby enabling bipolar division. Kinesin-like protein KIFC1 plays a critical role in centrosome clustering in cancer cells, but is not essential for normal cells. Therefore, targeting KIFC1 may provide novel insight into selective killing of cancer cells. In the present study, we identified a small-molecule KIFC1 inhibitor, SR31527, which inhibited microtubule (MT)-stimulated KIFC1 ATPase activity with an IC50 value of 6.6 μM. By using bio layer interferometry technology, we further demonstrated that SR31527 bound directly to KIFC1 with high affinity (Kd=25.4 nM). Our results from computational modelling and saturation-transfer difference (STD)-NMR experiments suggest that SR31527 bound to a novel allosteric site of KIFC1 that appears suitable for developing selective inhibitors of KIFC1. Importantly, SR31527 prevented bipolar clustering of extra centrosomes in triple negative breast cancer (TNBC) cells and significantly reduced TNBC cell colony formation and viability, but was less toxic to normal fibroblasts. Therefore, SR31527 provides a valuable tool for studying the biological function of KIFC1 and serves as a potential lead for the development of novel therapeutic agents for breast cancer treatment.

Impaired angiogenesis and tumor development by inhibition of the mitotic kinesin Eg5

Kinesin motor proteins exert essential cellular functions in all eukaryotes. They control mitosis, migration and intracellular transport through interaction with microtubules. Small molecule inhibitors of the mitotic kinesin KiF11/Eg5 are a promising new class of anti-neoplastic agents currently evaluated in clinical cancer trials for solid tumors and hematological malignancies. Here we report induction of Eg5 and four other mitotic kinesins including KIF20A/Mklp2 upon stimulation of in vivo angiogenesis with vascular endothelial growth factor-A (VEGF-A). Expression analyses indicate up-regulation of several kinesin-encoding genes predominantly in lymphoblasts and endothelial cells. Chemical blockade of Eg5 inhibits endothelial cell proliferation and migration in vitro. Mitosis-independent vascular outgrowth in aortic ring cultures is strongly impaired after Eg5 or Mklp2 protein inhibition. In vivo, interfering with KIF11/Eg5 function causes developmental and vascular defects in zebrafish and chick embryos and potent inhibition of tumor angiogenesis in experimental tumor models. Besides blocking tumor cell proliferation, impairing endothelial function is a novel mechanism of action of kinesin inhibitors.

Tubulin inhibitors: pharmacophore modeling, virtual screening and molecular docking

AIM

To construct a quantitative pharmacophore model of tubulin inhibitors and to discovery new leads with potent antitumor activities.

METHODS

Ligand-based pharmacophore modeling was used to identify the chemical features responsible for inhibiting tubulin polymerization. A set of 26 training compounds was used to generate hypothetical pharmacophores using the HypoGen algorithm. The structures were further validated using the test set, Fischer randomization method, leave-one-out method and a decoy set, and the best model was chosen to screen the Specs database. Hit compounds were subjected to molecular docking study using a Molecular Operating Environment (MOE) software and to biological evaluation in vitro.

RESULTS

Hypo1 was demonstrated to be the best pharmacophore model that exhibited the highest correlation coefficient (0.9582), largest cost difference (70.905) and lowest RMSD value (0.6977). Hypo1 consisted of one hydrogen-bond acceptor, a hydrogen-bond donor, a hydrophobic feature, a ring aromatic feature and three excluded volumes. Hypo1 was validated with four different methods and had a goodness-of-hit score of 0.81. When Hypo1 was used in virtual screening of the Specs database, 952 drug-like compounds were revealed. After docking into the colchicine-binding site of tubulin, 5 drug-like compounds with the required interaction with the critical amino acid residues and the binding free energies < -4 kcal/mol were selected as representative leads. Compounds 1 and 3 exhibited inhibitory activity against MCF-7 human breast cancer cells in vitro.

CONCLUSION

Hypo1 is a quantitative pharmacophore model for tubulin inhibitors, which not only provides a better understanding of their interaction with tubulin, but also assists in discovering new potential leads with antitumor activities.

Kif11 dependent cell cycle progression in radial glial cells is required for proper neurogenesis in the zebrafish neural tube

Radial glia serve as the resident neural stem cells in the embryonic vertebrate nervous system, and their proliferation must be tightly regulated to generate the correct number of neuronal and glial cell progeny in the neural tube. During a forward genetic screen, we recently identified a zebrafish mutant in the kif11 loci that displayed a significant increase in radial glial cell bodies at the ventricular zone of the spinal cord. Kif11, also known as Eg5, is a kinesin-related, plus-end directed motor protein responsible for stabilizing and separating the bipolar mitotic spindle. We show here that Gfap+ radial glial cells express kif11 in the ventricular zone and floor plate. Loss of Kif11 by mutation or pharmacological inhibition with S-trityl-L-cysteine (STLC) results in monoastral spindle formation in radial glial cells, which is characteristic of mitotic arrest. We show that M-phase radial glia accumulate over time at the ventricular zone in kif11 mutants and STLC treated embryos. Mathematical modeling of the radial glial accumulation in kif11 mutants not only confirmed an ~226× delay in mitotic exit (likely a mitotic arrest), but also predicted two modes of increased cell death. These modeling predictions were supported by an increase in the apoptosis marker, anti-activated Caspase-3, which was also found to be inversely proportional to a decrease in cell proliferation. In addition, treatment with STLC at different stages of neural development uncovered two critical periods that most significantly require Kif11 function for stem cell progression through mitosis. We also show that loss of Kif11 function causes specific reductions in oligodendroglia and secondary interneurons and motorneurons, suggesting these later born populations require proper radial glia division. Despite these alterations to cell cycle dynamics, survival, and neurogenesis, we document unchanged cell densities within the neural tube in kif11 mutants, suggesting that a mechanism of compensatory regulation may exist to maintain overall proportions in the neural tube. We propose a model in which Kif11 normally functions during mitotic spindle formation to facilitate the progression of radial glia through mitosis, which leads to the maturation of progeny into specific secondary neuronal and glial lineages in the developing neural tube.

Kinesin spindle protein inhibitors in cancer: a patent review (2008 - present)

INTRODUCTION

Inhibition of kinesin spindle protein (KSP) has emerged as a novel and validated therapeutic strategy against cancers. A lot of new KSP inhibitors have been identified in recent years and some of them have entered clinical trials. This may provide more selections in future cancer therapy.

AREAS COVERED

In the present review, the authors will describe the most recent classes of KSP inhibitors by reviewing about 96 literatures in which 24 patent applications were included from 2008 to now.

EXPERT OPINION

Many new KSP inhibitors have been discovered that act either by binding in an allosteric site of KSP or by ATP competitive inhibition. There are several ATP non-competitive KSP inhibitors entering clinical investigation. Although they were both well tolerated and showed acceptable pharmacokinetic profiles, limited clinical response was always the problem. Mutation of the binding pocket was also a hindrance in the development of these allosteric inhibitors. The appearance of ATP competitive KSP inhibitors was considered to be able to overcome mutation-mediated resistance to the allosteric inhibitors, which could be a new approach for the development of novel KSP inhibitors.

Kinesin spindle protein (KSP) inhibitors in combination with chemotherapeutic agents for cancer therapy

A diverse group of proteins, the activities of which are precisely orchestrated during mitosis, have emerged as targets for cancer therapeutics; these include the Aurora kinases (AKs), Polo-like kinases (PLKs), and the kinesin spindle protein (KSP). KSP is essential for the proper separation of spindle poles during mitosis. Agents that target KSP selectively act on cells undergoing cell division, which means that KSP inhibitors are mitosis-specific drugs, and have demonstrated remarkable activities in vitro. However, a significant obstacle to the success of KSP inhibitors is that these compounds, with tremendous efficacy in vitro, have demonstrated little or even no antitumor activity in vivo. Accumulated data suggest that a combination of KSP inhibitors with various cytostatic drugs will result in a more powerful tumor-killing effect than monotherapy. Combination therapies might predominate and represent the next frontier in the discovery research of KSP inhibitors as potential anticancer drugs. Few published studies have reviewed combination therapy using KSP inhibitors. Herein we provide a comprehensive review of the literature on KSP inhibitor monotherapy and therapeutic combinations. The current state and problems are also discussed.

Advances in the discovery of kinesin spindle protein (Eg5) inhibitors as antitumor agents

Cancer is considered as one of the most serious health problems. Despite the presence of many effective chemotherapeutic agents, their severe side effects together with the appearance of mutant tumors limit the use of these drugs and increase the need for new anticancer agents. Eg5 represents an attractive target for medicinal chemists since Eg5 is overexpressed in many proliferative tissues while almost no Eg5 is detected in nonproliferative tissues. Many Eg5 inhibitors displayed potent anticancer activity against some of the mutant tumors with limited side effects. The present review provides an overview about the progress in the discovery of Eg5 inhibitors especially from 2009 to 2012 as well as the clinical trials conducted on some of these inhibitors.

De novo design, synthesis and biological evaluation of 1,4-dihydroquinolin-4-ones and 1,2,3,4-tetrahydroquinazolin-4-ones as potent kinesin spindle protein (KSP) inhibitors

Kinesin spindle protein (KSP) inhibitors are a promising class of anticancer agents that cause mitotic arrest in cells from a failure to form functional bipolar mitotic spindles. Here, we report the design, synthesis and biological evaluation of a novel series of 1,4-dihydroquinolin-4-ones and 1,2,3,4-tetrahydroquinazolin-4-ones using de novo design method. The synthesized compound was evaluated and proved to have potent inhibitory activities in the KSP ATPase. Compounds 15j and 15p show potent inhibitory activities in cell proliferation assays. Preferred compound 15j markedly induced G2/M phase cell cycle arrest with characteristic monoastral spindles and subsequent cell death in A549 cells. In vivo evaluation of 15j on the growth of transplantable S180 sarcoma in mice suggested its therapeutic potential for further development.

Structure-activity relationships of carboline and carbazole derivatives as a novel class of ATP-competitive kinesin spindle protein inhibitors

The kinesin spindle protein (KSP) is a mitotic kinesin involved in the establishment of a functional bipolar mitotic spindle during cell division. It is considered to be an attractive target for cancer chemotherapy with reduced side effects. Based on natural product scaffold-derived fused indole-based inhibitors and known biphenyl-type KSP inhibitors, various carboline and carbazole derivatives were synthesized and biologically evaluated. β-Carboline and lactam-fused carbazole derivatives exhibited remarkably potent KSP inhibitory activity and mitotic arrest in prometaphase with formation of an irregular monopolar spindle. The planar tri- and tetracyclic analogs inhibited KSP ATPase in an ATP-competitive manner just like biphenyl-type inhibitors.

Essential genes for astroglial development and axon pathfinding during zebrafish embryogenesis

The formation of the central nervous system depends on the coordinated development of neural and glial cell types that arise from a common precursor. Using an existing group of zebrafish mutants generated by viral insertion, we performed a "shelf-screen" to identify genes necessary for astroglial development and axon scaffold formation. We screened 274 of 315 viral insertion lines using antibodies that label axons (anti-Acetylated Tubulin) and astroglia (anti-Gfap) and identified 25 mutants with defects in gliogenesis, glial patterning, neurogenesis, and axon guidance. We also identified a novel class of mutants affecting radial glial cell numbers. Defects in astroglial patterning were always associated with axon defects, supporting an important role for axon-glial interactions during axon scaffold development. The genes disrupted in these viral lines have all been identified, providing a powerful new resource for the study of axon guidance, glio- and neurogenesis, and neuron-glial interactions during development of the vertebrate CNS.

Discovery of the First Potent and Selective Inhibitor of Centromere-Associated Protein E: GSK923295

Inhibition of mitotic kinesins represents a novel approach for the discovery of a new generation of anti-mitotic cancer chemotherapeutics. We report here the discovery of the first potent and selective inhibitor of centromere-associated protein E (CENP-E) 3-chloro-N-{(1S)-2-[(N,N-dimethylglycyl)amino]-1-[(4-{8-[(1S)-1-hydroxyethyl]imidazo[1,2-a]pyridin-2-yl}phenyl)methyl]ethyl}-4-[(1-methylethyl)oxy]benzamide (GSK923295; 1), starting from a high-throughput screening hit, 3-chloro-4-isopropoxybenzoic acid 2. Compound 1 has demonstrated broad antitumor activity in vivo and is currently in human clinical trials.

K858, a novel inhibitor of mitotic kinesin Eg5 and antitumor agent, induces cell death in cancer cells

The aim of this study was to investigate the mechanism of inhibition of Eg5 (kinesin spindle protein), a mitotic kinesin that plays an essential role in establishing mitotic spindle bipolarity, by the novel small molecule inhibitor K858. K858 was selected in a phenotype-based forward chemical genetics screen as an antimitotic agent, and subsequently characterized as an inhibitor of Eg5. K858 blocked centrosome separation, activated the spindle checkpoint, and induced mitotic arrest in cells accompanied by the formation of monopolar spindles. Long-term continuous treatment of cancer cells with K858 resulted in antiproliferative effects through the induction of mitotic cell death, and polyploidization followed by senescence. In contrast, treatment of nontransformed cells with K858 resulted in mitotic slippage without cell death, and cell cycle arrest in G(1) phase in a tetraploid state. In contrast to paclitaxel, K858 did not induce the formation of micronuclei in either cancer or nontransformed cells, suggesting that K858 has minimal effects on abnormalities in the number and structure of chromosomes. K858 exhibited potent antitumor activity in xenograft models of cancer, and induced the accumulation of mitotic cells with monopolar spindles in tumor tissues. Importantly, K858, unlike antimicrotubule agents, had no effect on microtubule polymerization in cell-free and cell-based assays, and was not neurotoxic in a motor coordination test in mice. Taken together, the Eg5 inhibitor K858 represents an important compound for further investigation as a novel anticancer therapeutic.

Targeting the kinesin spindle protein: basic principles and clinical implications

Kinesin spindle protein (KSP), a member of the kinesin superfamily of microtubule-based motors, plays a critical role in mitosis as it mediates centrosome separation and bipolar spindle assembly and maintenance. Inhibition of KSP function leads to cell cycle arrest at mitosis with the formation of monoastral microtubule arrays, and ultimately, to cell death. Several KSP inhibitors are currently being studied in clinical trials and provide new opportunities for the development of novel anticancer therapeutics alternative from the available microtubule targeting drugs.

Conformation-dependent ligand regulation of ATP hydrolysis by human KSP: activation of basal hydrolysis and inhibition of microtubule-stimulated hydrolysis by a single, small molecule modulator

Human kinesin spindle protein (KSP)/hsEg5, a member of the kinesin-5 family, is essential for mitotic spindle assembly in dividing human cells and is required for cell cycle progression through mitosis. Inhibition of the ATPase activity of KSP leads to cell cycle arrest during mitosis and subsequent cell death. Ispinesib (SB-715992), a potent and selective inhibitor of KSP, is currently in phase II clinical trials for the treatment of multiple tumor types. Mutations that attenuate Ispinesib binding to KSP in vitro have been identified, highlighting the need for inhibitors that target different binding sites and inhibit KSP activity by novel mechanisms. We report here a small-molecule modulator, KSPA-1, that activates KSP-catalyzed ATP hydrolysis in the absence of microtubules yet inhibits microtubule-stimulated ATP hydrolysis by KSP. KSPA-1 inhibits cell proliferation and induces monopolar-spindle formation in tumor cells. Results from kinetic analyses, microtubule (MT) binding competition assays, and hydrogen/deuterium-exchange studies show that KSPA-1 does not compete directly for microtubule binding. Rather, this compound acts by driving a conformational change in the KSP motor domain and disrupts productive ATP turnover stimulated by MT. These findings provide a novel mechanism for targeting KSP and perhaps other mitotic kinesins.

Synthesis and SAR of thiophene containing kinesin spindle protein (KSP) inhibitors

We have identified and synthesized a series of thiophene containing inhibitors of kinesin spindle protein. SAR studies led to the synthesis of 33, which was co-crystallized with KSP and determined to bind to an allosteric pocket previously described for other known KSP inhibitors.

Rapid preparation of the mitotic kinesin Eg5 inhibitor monastrol using controlled microwave-assisted synthesis

We present here a protocol for the synthesis of the dihydropyrimidine (DHPM) derivative monastrol, which is known to be a specific mitotic kinesin Eg5 inhibitor. By applying controlled microwave heating under sealed-vessel conditions, the synthesis via the one-pot three-component Biginelli condensation can be performed in a shorter reaction time (30 min) compared with conventional heating methods that normally require several hours of reflux heating. For the purification of the crude target compound, two different methods are presented. The first protocol includes a simple precipitation/filtration step to provide monastrol in 76% isolated yield and high purity so that no recrystallization step is necessary. This can be ascribed to the microwave heating technology in which less side-product formation is typically one of the advantages. In an alternative purification step, column chromatography is performed, which provides the product in a slightly higher yield (86%). Monastrol synthesis can be conducted in approximately 2 h by employing the precipitation/filtration purification method.

Synthesis and structure-activity relationships of carbazole sulfonamides as a novel class of antimitotic agents against solid tumors

Two series of carbazole sulfonamides related to Combretastatin A4 (1) were synthesized and evaluated for antiproliferative activity. Thirteen of the 26 new sulfonamides exhibited IC(50) values of <1 muM against CEM leukemia cells. Five compounds were evaluated against a panel of eight human tumor cell lines. 9-Ethyl-N-(3,4,5-trimethoxyphenyl)-carbazole-3-sulfonamide (11a) showed significant antitumor activity in two human xenograft models (MCF-7 and Bel-7402). Preliminary studies with 11a showed that the mode of action involves arrest of M-phase cell cycle and induction of apoptosis by increasing expression of p53 and promoting bcl-2 phosphorylation. Unexpectedly, 11a only weakly inhibits tubulin polymerization, which suggests that the mode of action of 11a differs from 1 and involves an unidentified target(s). Also, the SAR information gleaned from ring A-substituted analogues varies significantly from that of 1. Carbazole sulfonamides are a novel promising class of antimitotic agents with clinical development potential.