Overexpression of Eg5 predicts unfavorable prognosis in non-muscle invasive bladder urothelial carcinoma

Identifying and characterising promising small molecule inhibitors of kinesin spindle protein using ligand-based virtual screening, molecular docking, molecular dynamics and MM‑GBSA calculations

The kinesin spindle protein (Eg5) is a mitotic protein that plays an essential role in the formation of the bipolar spindles during the mitotic phase. Eg5 protein controls the segregation of the chromosomes in mitosis which renders it a vital target for cancer treatment. In this study our approach to identifying novel scaffold for Eg5 inhibitors is based on targeting the novel allosteric pocket (α4/α6/L11). Extensive computational techniques were applied using ligand-based virtual screening and molecular docking by two approaches, MOE and AutoDock, to screen a library of commercial compounds. We identified compound 8-(3-(1H-imidazol-1-ylpropylamino)-3-methyl-7-((naphthalen-3-yl)methyl)-1H-purine-2, 6 (3H,7H)-dione (compound 5) as a novel scaffold for Eg5 inhibitors. This compound inhibited cancer cell Eg5 ATPase at 2.37 ± 0.15 µM. The molecular dynamics simulations revealed that the identified compound formed stable interactions in the allosteric pocket (α4/α6/L11) of the receptor, indicating its potential as a novel Eg5 inhibitor.

A Multiomics Profiling Based on Online Database Revealed Prognostic Biomarkers of BLCA

Background

Bladder cancer (BLCA) is one of the most common urological malignancies globally, posing a severe threat to public health. In combination with protein-protein interaction (PPI) network analysis of proteomics, Gene Set Variation Analysis (GSVA) and “CancerSubtypes” package of R software for transcriptomics can help identify biomarkers related to BLCA prognosis. This will have significant implications for prevention and treatment.

Method

BLCA data were downloaded from The Cancer Genome Atlas (TCGA) database and GEO database (GSE13507). GSVA analysis converted the gene expression matrix to the gene set expression matrix. “CancerSubtypes” classified patients into three subtypes and established a prognostic model based on differentially expressed gene sets (DEGSs) among the three subtypes. For genes from prognosis-related DEGSs, functional and pathway enrichment analyses and PPI network analysis were carried out. The Human Protein Atlas (HPA) database was used for validation. Finally, the proportion of tumor-infiltrating immune cells (TIICs) was determined using the CIBERSORT algorithm.

Results

In total, 414 tumor samples and 19 adjacent-tumor samples were obtained from TCGA, with 145 samples belonging to subtype A, 126 samples belonging to subtype B, and 136 samples belonging to subtype C. Then, we identified 83 DEGSs and constituted a prognostic signature with two of them: “GSE1460_CD4_THYMOCYTE_VS_THYMIC_STROMAL_CELL_DN” and “MODULE_253.” Finally, five subnets of two PPI networks were established, and nine core proteins were obtained: CDH2, COL1A1, EIF2S2, PSMA3, NAA10, DNM1L, TUBA4A, KIF11, and KIF23. The HPA database confirmed the expression of the nine core proteins in BLCA tissues. Furthermore, EIF2S2, PSMA3, DNM1L, and TUBA4A could be novel BLCA prognostic biomarkers.

Conclusions

In this study, we discovered two gene sets linked to BLCA prognosis. PPI analysis confirmed the network's core proteins, and several newly discovered biomarkers of BLCA prognosis were identified.

KIF11 as a potential cancer prognostic marker promotes tumorigenesis in children with Wilms tumor

Emerging evidence suggests that KIF11 could play a pivotal role in cancer cell proliferation; however, its biological functions and molecular mechanisms in Wilms tumor (WT) cells are largely unknown. The aim of this study was to evaluate the clinical significance and therapeutic potential of KIF11 proteins in WT. KIF11 expression in WT tissues and adjacent nontumor tissues was determined using qRT-PCR, Western blotting, immunohistochemistry (IHC) and bioinformatics. The function of KIF11 protein was determined by its correlation with tumor cell growth, angiogenesis, and apoptosis using IHC and lentiviral vector-mediated KIF11 depletion. KIF11 expression was upregulated in WT tissues and was associated with WT clinical outcomes. Tumor KIF11 expression was significantly associated with the Ki67 proliferation index. CCK-8, flow-cytometric analysis, and Western blotting revealed that KIF11 knockdown significantly inhibited WT cell growth. Functional studies have indicated that increased KIF11 expression is significantly correlated with vascular endothelial growth factor (VEGF) expression and intratumoral microvessel density. We further confirmed that downregulated expression of KIF11 promoted cell apoptosis and significantly increased Bcl-2 and Bax expression. Our findings demonstrate that KIF11 plays a role in promoting the development of human WT and can serve as a potential molecular marker for the treatment of WT.

Impact of the ferrocenyl group on cytotoxicity and KSP inhibitory activity of ferrocenyl monastrol conjugates

The incorporation of the ferrocenyl moiety into a bioactive molecule may significantly alter the activity of the resulting conjugate. By applying this strategy, we designed ferrocenyl analogs of monastrol - the first low molecular weight kinesin spindle protein (KSP) inhibitor. The obtained compounds showed low micromolar antiproliferative activity towards a panel of sensitive and ABC-overexpressing cancer cells. Most cytotoxic compounds exhibited also higher KSP modulatory activity and ability for ROS generation compared to monastrol. The increased bioactivity of the studied compounds can be attributed to the presence of the ferrocenyl group.

Exploratory comparisons between different anti-mitotics in clinically-used drug combination in triple negative breast cancer

Triple-negative breast cancer (TNBC) constitutes a very aggressive type of breast cancer with few options of cytotoxic chemotherapy available for them. A chemotherapy regimen comprising of doxorubicin hydrochloride and cyclophosphamide, followed by paclitaxel, known as AC-T, is approved for usage as an adjuvant treatment for this type of breast cancer. In this study we aimed to elucidate the role of KIF11 in TNBC progression throughout its inhibition by two synthetic small molecules containing the DHPM core (dihydropyrimidin-2(1H)-ones or -thiones), with the hypothesis that these inhibitors could be an interesting option of antimitotic drug used alone or as adjuvant therapy in association with AC. For this purpose, we evaluated the efficacy of DHPMs used as monotherapy or in combination with doxorubicin and cyclophosphamide, in Balbc-nude mice bearing breast cancer induced by MDA-MB-231, having AC-T as positive control. Our data provide extensive evidence to demonstrate that KIF11 inhibitors showed pronounced antitumor activity, acting in key points of tumorigenesis and cancer progression in in vivo xenograft model of triple negative breast cancer, like down-regulation of KIF11 and ALDH1-A1. Moreover, they didn’t show the classic peripheral neuropathy characterized by impaired mobility, as it is common with paclitaxel use. These results suggest that the use of a MAP inhibitor in breast cancer regimen treatment could be a promising strategy to keep antitumoral activity reducing the side effects.

Second-Generation Antimitotics in Cancer Clinical Trials

Mitosis represents a promising target to block cancer cell proliferation. Classical antimitotics, mainly microtubule-targeting agents (MTAs), such as taxanes and vinca alkaloids, are amongst the most successful anticancer drugs. By disrupting microtubules, they activate the spindle assembly checkpoint (SAC), which induces a prolonged delay in mitosis, expected to induce cell death. However, resistance, toxicity, and slippage limit the MTA's effectiveness. With the desire to overcome some of the MTA's limitations, mitotic and SAC components have attracted great interest as promising microtubule-independent targets, leading to the so-called second-generation antimitotics (SGAs). The identification of inhibitors against most of these targets, and the promising outcomes achieved in preclinical assays, has sparked the interest of academia and industry. Many of these inhibitors have entered clinical trials; however, they exhibited limited efficacy as monotherapy, and failed to go beyond phase II trials. Combination therapies are emerging as promising strategies to give a second chance to these SGAs. Here, an updated view of the SGAs that reached clinical trials is here provided, together with future research directions, focusing on inhibitors that target the SAC components.

KIF11 Promotes Proliferation of Hepatocellular Carcinoma among Patients with Liver Cancers

BACKGROUND

Hepatocellular carcinoma (HCC) lacks effective treatments and has a poor prognosis. Therefore it is needed to develop more effective drug targets. Kinesin family member 11 (KIF11) has been reported to affect the progression of several cancers, and its high expression associates with the prognosis of patients. However, the relevant mechanisms of KIF11 in HCC progression have not been studied.

METHOD

Through the cancer genome atlas (TCGA) database and immunohistochemical (IHC) staining of patients' specimens, we determined that KIF11 was highly expressed in HCC tissues and associated with prognosis. We established a KIF11 stably depleted hepatoma cell line, through cell-cloning experiments and cell counting kit-8 (CCK-8) assays to detect the effects on proliferation in vitro. The role of KIF11 in promoting cell proliferation was verified in mice.

RESULT

The expression of KIF11 was negatively correlated with the overall survival (OS) and disease-free survival (DFS) and positively correlated with tumor size of HCC patients. KIF11 depletion inhibits cell proliferation and tumor growth in vitro and in vivo. Conclusion. KIF11 can be used as a positive correlation marker for HCC prognosis and served as a potential therapeutic target.

Eg5 targeting agents: From new anti-mitotic based inhibitor discovery to cancer therapy and resistance

Eg5, the product of Kif11 gene, also known as kinesin spindle protein, is a motor protein involved in the proper establishment of a bipolar mitotic spindle. Eg5 is one of the 45 different kinesins coded in the human genome of the kinesin motor protein superfamily. Over the last three decades Eg5 has attracted great interest as a promising new mitotic target. The identification of monastrol as specific inhibitor of the ATPase activity of the motor domain of Eg5 inhibiting the Eg5 microtubule motility in vitro and in cellulo sparked an intense interest in academia and industry to pursue the identification of novel small molecules that target Eg5 in order to be used in cancer chemotherapy based on the anti-mitotic strategy. Several Eg5 inhibitors entered clinical trials. Currently the field is faced with the problem that most of the inhibitors tested exhibited only limited efficacy. However, one Eg5 inhibitor, Arry-520 (clinical name filanesib), has demonstrated clinical efficacy in patients with multiple myeloma and is scheduled to enter phase III clinical trials. At the same time, new trends in Eg5 inhibitor research are emerging, including an increased interest in novel inhibitor binding sites and a focus on drug synergy with established antitumor agents to improve chemotherapeutic efficacy. This review presents an updated view of the structure and function of Eg5-inhibitor complexes, traces the possible development of resistance to Eg5 inhibitors and their potential therapeutic applications, and surveys the current challenges and future directions of this active field in drug discovery.

IL3RA-Targeting Antibody-Drug Conjugate BAY-943 with a Kinesin Spindle Protein Inhibitor Payload Shows Efficacy in Preclinical Models of Hematologic Malignancies

IL3RA (CD123) is the alpha subunit of the interleukin 3 (IL-3) receptor, which regulates the proliferation, survival, and differentiation of hematopoietic cells. IL3RA is frequently expressed in acute myeloid leukemia (AML) and classical Hodgkin lymphoma (HL), presenting an opportunity to treat AML and HL with an IL3RA-directed antibody-drug conjugate (ADC). Here, we describe BAY-943 (IL3RA-ADC), a novel IL3RA-targeting ADC consisting of a humanized anti-IL3RA antibody conjugated to a potent proprietary kinesin spindle protein inhibitor (KSPi). In vitro, IL3RA-ADC showed potent and selective antiproliferative efficacy in a panel of IL3RA-expressing AML and HL cell lines. In vivo, IL3RA-ADC improved survival and reduced tumor burden in IL3RA-positive human AML cell line-derived (MOLM-13 and MV-4-11) as well as in patient-derived xenograft (PDX) models (AM7577 and AML11655) in mice. Furthermore, IL3RA-ADC induced complete tumor remission in 12 out of 13 mice in an IL3RA-positive HL cell line-derived xenograft model (HDLM-2). IL3RA-ADC was well-tolerated and showed no signs of thrombocytopenia, neutropenia, or liver toxicity in rats, or in cynomolgus monkeys when dosed up to 20 mg/kg. Overall, the preclinical results support the further development of BAY-943 as an innovative approach for the treatment of IL3RA-positive hematologic malignancies.

Transcriptome analysis reveals key signature genes involved in the oncogenesis of lung cancer

Previous studies have suggested potential signature genes for lung cancer, however, due to factors such as sequencing platform, control, data selection and filtration conditions, the results of lung cancer-related gene expression analysis are quite different. Here, we performed a meta-analysis on existing lung cancer gene expression results to identify Meta-signature genes without noise. In this study, functional enrichment, protein-protein interaction network, the DAVID, String, TfactS, and transcription factor binding were performed based on the gene expression profiles of lung adenocarcinoma and non-small cell lung cancer deposited in the GEO database. As a result, a total of 574 differentially expressed genes (DEGs) affecting the pathogenesis of lung cancer were identified (207 up-regulated expression and 367 down-regulated expression in lung cancer tissues). A total of 5,093 interactions existed among the 507 (88.3%) proteins, and 10 Meta-signatures were identified: AURKA, CCNB1, KIF11, CCNA2, TOP2A, CENPF, KIF2C, TPX2, HMMR, and MAD2L1. The potential biological functions of Meta-signature DEGs were revealed. In summary, this study identified key genes involved in the process of lung cancer. Our results would help the developing of novel biomarkers for lung cancer.

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.

Kinesin family member 11 is a potential therapeutic target and is suppressed by microRNA-30a in breast cancer

Kinesin family member 11 (KIF11) is a plus end‐directed kinesin indispensable for the formation of the bipolar spindle in metaphase, where it objects to the action of minus end‐directed molecular motors. Here, we hypothesize that KIF11 might be a therapeutic target of breast cancer and regulated by miR‐30a. Cell Counting Kit 8 assays were used to investigate cell proliferation. Invasion assays were used to survey the motility of cells. Kaplan‐Meier and Cox proportional analyses were employed for this outcome study. The prognostic significance and performance of KIF11 were validated on 17 worldwide independent microarray datasets and two The Cancer Genome Atlas‐Breast Invasive Carcinoma sets. microRNA was predicted targeting KIF11 through sequence alignment in microRNA.org and confirmed by coexpression analysis in human breast cancer samples. Dual‐luciferase reporter assays were employed to validate the interaction between miR‐30a and KIF11 further. Higher KIF11 mRNA levels and lower miR‐30a were significantly associated with poor survival of breast cancer patients. Inhibition of KIF11 by small‐hairpin RNA significantly reduced the proliferation and invasion capabilities of the breast cancer cells. Meanwhile, downregulation of KIF11 could enhance the cytotoxicity of adriamycin in breast cancer cell lines MCF‐7 and MDA‐MB‐231. A population study also validated that chemotherapy and radiotherapy significantly improved survival in early‐stage breast cancer patients with low KIF11 expression levels. Further bioinformatics analysis demonstrated that miR‐30a could interact with KIF11 and validated by dual‐luciferase reporter assays. Therefore, KIF11 is a potential therapeutic target of breast cancer. miR‐30a could specifically interact with KIF11 and suppress its expression in breast cancer.

Transport of microtubules according to the number and spacing of kinesin motors on gold nano-pillars

Motor proteins function in in vivo ensembles to achieve cargo transport, flagellum motion, and mitotic cell division. Although the cooperativity of multiple motors is indispensable for physiological function, reconstituting the arrangement of motors in vitro is challenging, so detailed analysis of the functions of motor ensembles has not yet been achieved. Here, we developed an assay platform to study the motility of microtubules driven by a defined number of kinesin motors spaced in a definite manner. Gold (Au) nano-pillar arrays were fabricated on a silicon/silicon dioxide (Si/SiO₂) substrate with spacings of 100 nm to 500 nm. The thiol-polyethylene glycol (PEG)-biotin self-assembled monolayer (SAM) and silane-PEG-CH₃ SAM were then selectively formed on the pillars and SiO₂ surface, respectively. This allowed for both immobilization of kinesin molecules on Au nano-pillars in a precise manner and repulsion of kinesins from the SiO₂ surface. Using arrayed kinesin motors, we report that motor number and spacing do not influence the motility of microtubules driven by kinesin-1 motors. This assay platform is applicable to all kinds of biotinylated motors, allows the study of the effects of motor number and spacing, and is expected to reveal novel behaviors of motor proteins.

Cancer drug therapy and stochastic modeling of "nano-motors"

Background

Controlled inhibition of kinesin motor proteins is highly desired in the field of oncology. Among other interventions, there exists “targeted chemotherapeutic regime/options” of selective Eg5 competitive and allosteric inhibitors, inducing cancer cell apoptosis and tumor regression with improved safety profiles.

Research question

Though promising, such studies are still under clinical trials, for the discovery of efficient and least harmful Eg5 inhibitors. The aim of this research was to bridge the computational modeling approach with drug design and therapy of cancer cells.

Methods

A computational model, interfaced with the clinical data of “Eg5 dynamics” and “inhibitors” via special functions, is presented in this article. Comparisons are made for the drug efficacy, and the threshold values are predicted through numerical simulations.

Results

Results are obtained to depict the dynamics induced by ispinesib, when used as an inhibitor of kinesin Eg5, on cancer cell lines.

Non-canonical functions of the mitotic kinesin Eg5

Kinesins are widely expressed, microtubule-dependent motors that play vital roles in microtubule-associated cellular activities, such as cell division and intracellular transport. Eg5, also known as kinesin-5 or kinesin spindle protein, is a member of the kinesin family that contributes to the formation and maintenance of the bipolar mitotic spindle during cell division. Small-molecule compounds that inhibit Eg5 activity have been shown to impair spindle assembly, block mitotic progression, and possess anti-cancer activity. Recent studies focusing on the localization and functions of Eg5 in plants have demonstrated that in addition to spindle organization, this motor protein has non-canonical functions, such as chromosome segregation and cytokinesis, that have not been observed in animals. In this review, we discuss the structure, function, and localization of Eg5 in various organisms, highlighting the specific role of this protein in plants. We also propose directions for the future studies of novel Eg5 functions based on the lessons learned from plants.

Circular RNA‑MTO1 suppresses breast cancer cell viability and reverses monastrol resistance through regulating the TRAF4/Eg5 axis

Circular RNAs (circRNAs), a class of endogenous RNAs, have emerged as an enigmatic class of genes. However, little is known about their value in the progression and chemoresistance of cancers. The present study sought to determine the expression profiles and potential modulatory role of circRNAs on breast cancer cell viability and monastrol resistance. Monastrol-resistant cell lines were established by exposing breast cancer cells to increasing concentrations of monastrol. A human circRNA microarray was used to search for dysregulated circRNAs in monastrol-resistant cells, then circRNA‑MTO1 (hsa‑circRNA-007874) was validated as a circRNA that exhibited elevated expression levels in monastrol-resistant cells. Mechanistic investigations suggested that upregulation of circRNA‑MTO1 suppressed cell viability, promoted monastrol-induced cell cytotoxicity and reversed monastrol resistance. Subsequently, Eg5 was identified as the functional target of circRNA‑MTO1, and MTO1 inhibited Eg5 protein level but not mRNA level. By treating with protein synthesis inhibitor cycloheximide (CHX), it was revealed that MTO1 did not affect the protein stability of Eg5. RNA-pull down experiments followed by mass spectrometry revealed that MTO1 interacted with tumor necrosis factor receptor associated factor 4 (TRAF4), and sequester TRAF4 from activating Eg5 translation, thereby inhibiting the Eg5 protein level. Taken together, the data reveal a regulatory mechanism by circRNA‑MTO1 to control cell viability and monastrol resistance in breast cancer cells.

A New Way to Treat Brain Tumors: Targeting Proteins Coded by Microcephaly Genes?: Brain tumors and microcephaly arise from opposing derangements regulating progenitor growth. Drivers of microcephaly could be attractive brain tumor targets

New targets for brain tumor therapies may be identified by mutations that cause hereditary microcephaly. Brain growth depends on the repeated proliferation of stem and progenitor cells. Microcephaly syndromes result from mutations that specifically impair the ability of brain progenitor or stem cells to proliferate, by inducing either premature differentiation or apoptosis. Brain tumors that derive from brain progenitor or stem cells may share many of the specific requirements of their cells of origin. These tumors may therefore be susceptible to disruptions of the protein products of genes that are mutated in microcephaly. The potential for the products of microcephaly genes to be therapeutic targets in brain tumors are highlighted hereby reviewing research on EG5, KIF14, ASPM, CDK6, and ATR. Treatments that disrupt these proteins may open new avenues for brain tumor therapy that have increased efficacy and decreased toxicity.

Kinesin family member 11 contributes to the progression and prognosis of human breast cancer

The present study aimed to clarify the association between kinesin family member 11 (KIF11) and human breast cancer, and the effect of KIF11 on breast cancer cell progression. Western blot analysis, reverse transcription-quantitative polymerase chain reaction (RT-qPCR) analysis, retroviral infection, immunohistochemistry staining, MTT assay, anchorage-independent growth ability assay and tumorigenicity assay were all used in the present study. Western blot and RT-qPCR analysis revealed that the expression of KIF11 was markedly increased in malignant cells compared with that in non-tumorous cells at the mRNA and protein level. Immunohistochemical analysis revealed that KIF11 expression was upregulated in 256/268 (95.8%) paraffin-embedded archival breast cancer biopsies. Statistical analysis demonstrated a significant association between the upregulation of KIF11 expression and the progression of breast cancer. Multivariate analysis revealed that KIF11 upregulation represents an independent prognostic indicator for the survival of patients with breast cancer. Tumorigenicity experiments were further used to evaluate the effect of KIF11 in non-obese diabetic/severe combined immunodeficient mice. Silencing endogenous KIF11 by short hairpin RNAs inhibited the proliferation of breast cancer cells in vitro and in vivo. The present results suggest that KIF11 may serve an important function in the proliferation of breast cancer and may represent a novel and useful prognostic marker for breast cancer.

KIF11 is required for proliferation and self-renewal of docetaxel resistant triple negative breast cancer cells

Development of chemoresistance remains a major hurdle for triple negative breast cancer treatment. Previous studies suggest that CD44+/CD24- cells, subpopulation of cancer stem cells with self-renewing and tumor-initiating capacities, are partly responsible for chemoresistance and therapeutic failure of triple negative breast cancer. Therefore, novel agents that target cancer stem cells (CSCs) may improve the clinical outcome. KIF11 (kinesin family member 11), overexpressed in many cancer cells, is a molecular motor protein that plays essential role in mitosis. In this study, we assess its role in docetaxel resistant triple negative breast cancer (TNBC). We found that the expression of KIF11 was significantly increased in CD44+/CD24- subpopulation of docetaxel resistant TNBC cells. Knockdown of KIF11 resulted in a significant decrease in the percentage of CSCs and mammosphere formation. KIF11 knockdown also inhibits cell growth and induces cell cycle G2/M arrest followed by cell mitosis and apoptosis. Further docetaxel resistant TNBC xenograft models demonstrated that KIF11 inhibitor exerts growth inhibitory effect in vivo. Of note, we also found that KIF11 was highly expressed in TNBC and its expression was correlated with shorter disease free survival time. All these data indicate that KIF11 is critical for proliferation and self-renewal in TNBC tumor cells in vitro and in vivo, suggesting that KIF11 may be a promising therapeutic target for treating chemoresistant TNBC.

High Eg5 expression predicts poor prognosis in breast cancer

Eg5 is a motor protein belonging to the kinesin-5 family and has been suggested to exert important function in tumors. In this study, we determined the mRNA and protein expression levels of Eg5 in cancerous and non-cancerous breast tissue by quantitative real-time polymerase chain reaction (qRT-PCR) and tissue microarray immunohistochemistry analysis (TMA-IHC) respectively. The results of 20 fresh-frozen BC samples demonstrated that Eg5 mRNA levels were significantly higher in BC tissues compared with corresponding non-cancerous tissue (p = 0.0009). TMA-IHC analysis in 127 BC tissues revealed that Eg5 expression obviously correlated with clinicopathologial parameters, including tumor grade (p = 0.004), ER status (p = 0.030), Ki67 status (p = 0.005), molecular classification (p = 0.026), N stage (p = 0.015), and TNM stage (p = 0.001). Kaplan-Meier survival curve indicated that high Eg5 expression (p = 0.012), Ki67 status (p = 0.014) and TNM stage (p = 0.026) were independent factors to predict poor prognosis for patients with breast cancer. Our data suggest that Eg5 is not only overexpressed in BC, it may be also served as a potential prognostic marker.

Eg5 Overexpression Is Predictive of Poor Prognosis in Hepatocellular Carcinoma Patients

Eg5 (kinesin spindle protein) plays an essential role in mitosis. Inhibition of Eg5 function results in cell cycle arrest at mitosis, which leads to cell death. To date, Eg5 expression and its prognostic significance have not been studied in hepatocellular carcinoma (HCC). In this study, 26 freshly frozen HCC tissue samples and matched peritumoral tissue samples were evaluated with a one-step qPCR test and immunohistochemical (IHC) analysis was conducted on 156 HCC samples to investigate the relationships among Eg5 expression, clinicopathological factors, and prognosis. Eg5 mRNA and protein expression levels were significantly higher in HCC tissues relative to matched noncancerous tissues (p < 0.05). High Eg5 protein expression was significantly related to liver cirrhosis (p = 0.038) and TNM stage (p = 0.008). Kaplan-Meier survival and Cox regression analyses revealed that Eg5 overexpression (p = 0.001), liver cirrhosis (p = 0.009), and TNM stage (p = 0.025) were independent prognostic factors for overall survival. These findings indicate that Eg5 expression can be used as a biomarker of poor prognosis and as a novel therapeutic target for HCC.

Analysis of Biphenyl-Type Inhibitors Targeting the Eg5 α4/α6 Allosteric Pocket

Eg5 is a mitotic kinesin protein that plays an important role in the formation and maintenance of the bipolar spindle during the mitotic phase. Due to its potentially reduced side effects in cancer therapy, Eg5 is considered to be an attractive target for developing anticancer inhibitors. Herein, we report a computational modeling study involving biphenyl-type inhibitors known to interact with the α4/α6 allosteric pocket of Eg5. Compared to the well-known α2/L5/α3 allosteric inhibitors, biphenyl-type inhibitors show a unique activity profile. In the Eg5-PVZB1194 (a biphenyl-type inhibitor) crystal structure, loop L11, which is located in the entrance of the α4/α6 allosteric-binding pocket, is missing due to crystal-packing effects. To better understand the role of this flexible loop upon biphenyl-type inhibitor-binding, MD simulations were performed to observe the L11 conformations from different states. It was demonstrated that L11 was more stabilized and showed less fluctuation when PVZB1194 was bound to Eg5. Residue Asn287 from L11 forms hydrogen bonding to the sulfone group of PVZB1194, whereby L11 moves inward to the α4/α6 allosteric pocket and moves away from the pocket in absence of the inhibitor. Pharmacophore, three-dimensional (3D)-QSAR, and ADME studies of biphenyl-type inhibitors of Eg5 were also performed. A best pharmacophore model, DDRRH.6, was generated, having correlation coefficients in the 3D-QSAR study of R² = 0.81 and Q² = 0.64. Furthermore, docking studies were carried out to observe the interaction between the remaining biphenyl-type inhibitors with Eg5. In addition, on the basis of fragment docking, a structure-based pharmacophore was generated, which shares good overlap of the DHRR features of the pharmacophore model DDHRR.6. The structure-based pharmacophore also contains extra hydrogen-bond acceptors and hydrophobic groups, features which provide possibilities in developing new or improved series of compounds.

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.

Kinesin family members KIF11 and KIF23 as potential therapeutic targets in malignant pleural mesothelioma

Malignant pleural mesothelioma (MPM) is a rare and aggressive form of cancer commonly associated with asbestos exposure that stems from the thoracic mesothelium with high mortality rate. Currently, treatment options for MPM are limited, and new molecular targets for treatments are urgently needed. Using quantitative reverse transcription-polymerase chain reaction (RT-PCR) and an RNA interference-based screening, we screened two kinesin family members as potential therapeutic targets for MPM. Following in vitro investigation of the target silencing effects on MPM cells, a total of 53 MPMs were analyzed immunohistochemically with tissue microarray. KIF11 and KIF23 transcripts were found to be overexpressed in the majority of clinical MPM samples as well as human MPM cell lines as determined by quantitative RT-PCR. Gene knockdown in MPM cell lines identified growth inhibition following knockdown of KIF11 and KIF23. High expression of KIF11 (KIF11-H) and KIF23 (KIF23-H) were found in 43.4 and 50.9% of all the MPM cases, respectively. Patients who received curative resection with tumors displaying KIF23-H showed shorter overall survival (P=0.0194). These results provide that inhibition of KIF11 and KIF23 may hold promise for treatment of MPMs, raising the possibility that kinesin-based drug targets may be developed in the future.

Fbxo30 Regulates Mammopoiesis by Targeting the Bipolar Mitotic Kinesin Eg5

Fbxo30 is an orphan member of the F-box protein family with no known substrate or function. Here we report that, while Fbxo30(-/-) mice exhibit normal development, growth, lifespan, and fertility, the females fail to nurture their offspring as a result of defective mammopoiesis. Mass spectrometry analysis of Fbxo30-associated proteins revealed that Fbxo30 specifically interacts with the bipolar spindle kinesin EG5 (encoded by Kif11). As a result, Fbxo30 targets Eg5 for ubiquitinylation and controls its oscillation during the cell cycle. Correlated with EG5 dysregulation, Fbxo30(-/-) mammary epithelial cells exhibit multiple defects in centrosome homeostasis, mitotic spindle formation, and proliferation. Effects on proliferation, centrosome homeostasis, and mammopoiesis in the Fbxo30(-/-) mice were rescued through normalization of Eg5 activity using shRNA and/or an EG5 inhibitor. Our data reveal the Fbxo30-Eg5 interaction as a critical checkpoint in mammopoiesis and a critical role for ubiquitinylation-regulated Eg5 oscillation in the cell cycle.

Recent findings and future directions for interpolar mitotic kinesin inhibitors in cancer therapy

The kinesin class of microtubule-associated motor proteins present attractive anti-cancer targets owing to their roles in key functions in dividing cells. Two interpolar mitotic kinesins Eg5 and HSET have opposing motor functions in mitotic spindle assembly with respect to microtubule movement, but both offer opportunities to develop cancer selective therapeutic agents. Here, we summarize the progress to date in developing inhibitors of Eg5 and HSET, with an emphasis on structural biology insights into the binding modes of allosteric inhibitors, compound selectivity and mechanisms of action of different chemical scaffolds. We discuss translation of preclinical studies to clinical experience with Eg5 inhibitors, recent findings on potential resistance mechanisms, and explore the implications for future anticancer drug development against these targets.

Synergism between inhibitors of Aurora A and KIF11 overcomes KIF15-dependent drug resistance

The mitotic kinesin KIF11 (also called Eg5) plays critical roles in spindle functions. Although a number of small-molecule inhibitors of KIF11 are currently in clinical development, drug-resistance could be developed through compensation by another kinesin called KIF15. Using a newly developed infrared-based cell system, we discovered that the effectiveness of one of the latest generations of KIF11 inhibitor (SB743921) could be enhanced with several inhibitors of Aurora A kinase. Evidence including live-cell imaging and isobologram analysis indicated that targeting KIF11 and Aurora A together promoted monoastral spindle formation and mitotic catastrophe synergistically, supporting a model of parallel pathways of centrosome regulation by Aurora A and KIF11. We also developed a KIF15-dependent SB743921-resistance cell model. Significantly, the drug-resistance could also be overcome with Aurora A inhibitors. These results provide a molecular basis for increasing the effectiveness of Aurora A and KIF11 inhibitors and tackling problems of drug resistance.

Eg5 inhibitor, a novel potent targeted therapy, induces cell apoptosis in renal cell carcinoma

Eg5 is critical for mitosis and overexpressed in various malignant tumors, which has now been identified as a promising target in cancer therapy. However, the anti-cancer activity of Eg5 inhibitor in renal cell carcinoma (RCC) remains an open issue. In this paper, we evaluated, for the first time, the therapeutic benefit of blocking Eg5 by S-(methoxytrityl)-L-cysteine (S(MeO)TLC) in RCC both in vitro and vivo. The expression of Eg5 was examined in clinical tissue samples and various kidney cell lines, including 293T, 786-0, and OS-RC-2. The anti-proliferative activity of Eg5 inhibitors, (S)-trityl-L-cysteine (STLC) and S(MeO)TLC, was evaluated by a cell viability assay. An apoptosis assay with Hoechst nuclear staining and flow cytometry was applied to investigate the efficacy of the S(MeO)TLC, which is more potent than STLC. Immunofluorescence was used to research the possible mechanism. Furthermore, in vivo studies were performed by using subcutaneous xenograft models, which were used to confirm its role as a potential anti-neoplastic drug. The Eg5 expression was detected in kidney cell lines and RCC tissues, which was low in normal kidney samples. STLC and S(MeO)TLC exhibited their optimal anti-proliferative activity in 72 h, and cells treated with S(MeO)TLC presented characteristic monoastral spindle phenotype in 24 h and apoptotic cells in 48 h. In vivo, S(MeO)TLC effectively suppressed tumor growth in subcutaneous xenograft models. Inhibition of Eg5 represses the proliferation of RCC in vitro and in vivo. All these findings collectively demonstrate that S(MeO)TLC, a potent Eg5 inhibitor, is a promising anti-cancer agent for the treatment of RCC.

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.

The expression of Eg5 predicts a poor outcome for patients with renal cell carcinoma

Eg5 is a member of the kinesin family of proteins, which associates with bipolar spindle formation in dividing tumor cells during mitosis. The aim of our study is to investigate the prognostic role of Eg5 expression in patients with renal cell carcinoma (RCC). RCC tissue specimens from 164 consecutively treated patients who underwent surgery between 2005 and 2011 were evaluated. The Eg5 expression was determined by immunohistochemistry, and correlated with clinicopathological parameters. The prognostic significance of Eg5 expression was explored using the univariate and multivariate survival analysis of 164 patients who were followed; one hundred and sixty-four tissue specimens "of patients" who were regularly followed with the mean 35.8 months (from 5 to 80 months). The expression of Eg5 was significantly associated with tumor nuclear grade (P = 0.019) and stage (P = 0.007), as well as tumor size (P = 0.033). In univariate analysis, Eg5 overexpression showed unfavorable influence on recurrence-free survival with statistical significance (P = 0.003). Clinical stage, nuclear grade and tumor size also showed strong statistical relation with adverse recurrence-free survival (P < 0.001). Multivariate analysis revealed that tumor stage, nuclear grade and Eg5 reactivity (P < 0.001, P = 0.002, P = 0.032) were identified as independent prognostic factors for recurrence-free survival in patients with RCC. In our opinion, the result of this study proved the relationship between Eg5 expression and worse clinical outcome in RCC. This finding suggested that Eg5 served as a prognostic factor, which could be useful to predict cancer evolution and provide appropriate treatments for RCC patients.

Inhibition of Eg5 acts synergistically with checkpoint abrogation in promoting mitotic catastrophe

The G(2) DNA damage checkpoint is activated by genotoxic agents and is particularly important for cancer therapies. Overriding the checkpoint can trigger precocious entry into mitosis, causing cells to undergo mitotic catastrophe. But some checkpoint-abrogated cells can remain viable and progress into G(1) phase, which may contribute to further genome instability. Our previous studies reveal that the effectiveness of the spindle assembly checkpoint and the duration of mitosis are pivotal determinants of mitotic catastrophe after checkpoint abrogation. In this study, we tested the hypothesis whether mitotic catastrophe could be enhanced by combining genotoxic stress, checkpoint abrogation, and the inhibition of the mitotic kinesin protein Eg5. We found that mitotic catastrophe induced by ionizing radiation and a CHK1 inhibitor (UCN-01) was exacerbated after Eg5 was inhibited with either siRNAs or monastrol. The combination of DNA damage, UCN-01, and monastrol sensitized cancer cells that were normally resistant to checkpoint abrogation. Importantly, a relatively low concentration of monastrol, alone not sufficient in causing mitotic arrest, was already effective in promoting mitotic catastrophe. These experiments suggest that it is possible to use sublethal concentrations of Eg5 inhibitors in combination with G(2) DNA damage checkpoint abrogation as an effective therapeutic approach.