Antimitotic drugs in cancer chemotherapy: promises and pitfalls

Biological and metabolomics-guided isolation of tetrahydrofurofuran lignan from Croton spp. with antiproliferative activity against human melanoma cell line

The Croton genus (Euphorbiaceae) is recognized as a promising source for identifying bioactive compounds with antiproliferative activity. However, knowledge on the chemical composition and activity of Croton floribundus, Croton echinocarpus, and Croton zehntneri is limited. Thus, this study aimed to investigate the antiproliferative activity of these species on cells derived from tumoral breast, lung, and melanoma cells, and primary fibroblasts derived from human skin. Metabolomic strategies were applied via ultra-performance liquid chromatography coupled with high-resolution mass spectrometry and multivariate statistical analysis to target the main active compound. The C. floribundus leaf extract exhibited the highest activity, with an IC50 value lower than that of the reference drug - temozolomide - in the most responsive cell line - SK-MEL-147 - and in all the evaluated melanoma cell lines (SK-MEL-147, CHL-1 and WM-1366). Four tetrahydrofurofuran lignans were isolated for the first time from the most promising fraction of the C. floribundus extract. According to the metabolomic and multivariate statistical analyses, the isolated lignan epi-yangambin constituted the main antiproliferative compound against SK-MEL-147; furthermore, it exhibited selective antiproliferative activity for this cell line (IC50 = 13.09 μg/mL and selectivity index = 3.82; temozolomide, IC50 = 121.50 μg/mL) due to, at least in part, its ability to inhibit cell cycle progression at G2/M. This is especially relevant considering the high resistance of melanoma cells to available drugs. Thus, epi-yangambin can serve as a prototype for further antiproliferative investigations.

Chronic spindle assembly checkpoint activation causes myelosuppression and gastrointestinal atrophy

Interference with microtubule dynamics in mitosis activates the spindle assembly checkpoint (SAC) to prevent chromosome segregation errors. The SAC induces mitotic arrest by inhibiting the anaphase-promoting complex (APC) via the mitotic checkpoint complex (MCC). The MCC component MAD2 neutralizes the critical APC cofactor, CDC20, preventing exit from mitosis. Extended mitotic arrest can promote mitochondrial apoptosis and caspase activation. However, the impact of mitotic cell death on tissue homeostasis in vivo is ill-defined. By conditional MAD2 overexpression, we observe that chronic SAC activation triggers bone marrow aplasia and intestinal atrophy in mice. While myelosuppression can be compensated for, gastrointestinal atrophy is detrimental. Remarkably, deletion of pro-apoptotic Bim/Bcl2l11 prevents gastrointestinal syndrome, while neither loss of Noxa/Pmaip or co-deletion of Bid and Puma/Bbc3 has such a protective effect, identifying BIM as rate-limiting apoptosis effector in mitotic cell death of the gastrointestinal epithelium. In contrast, only overexpression of anti-apoptotic BCL2, but none of the BH3-only protein deficiencies mentioned above, can mitigate myelosuppression. Our findings highlight tissue and cell-type-specific survival dependencies in response to SAC perturbation in vivo.

Tumor invasiveness is regulated by the concerted function of APC, formins, and Arp2/3 complex

Tumor cell invasion is the initial step in metastasis, the leading cause of death from cancer. Invasion requires protrusive cellular structures that steer the migration of leader cells emanating from the tumor mass toward neighboring tissues. Actin is central to these processes and is therefore the prime target of drugs known as migrastatics. However, the broad effects of general actin inhibitors limit their therapeutic use. Here, we delineate the roles of specific actin nucleators in tuning actin-rich invasive protrusions and pinpoint potential pharmacological targets. We subject colorectal cancer spheroids embedded in collagen matrix-a preclinical model mirroring solid tumor invasiveness-to pharmacologic and/or genetic treatment of specific actin arrays to assess their roles in invasiveness. Our data reveal coordinated yet distinct involvement of actin networks nucleated by adenomatous polyposis coli, formins, and actin-related protein 2/3 complex in the biogenesis and maintenance of invasive protrusions. These findings may open avenues for better targeted therapies.

Design, synthesis and biological evaluation of new 2,6-difluorinated phenyl 4-(2-oxoimidazolidin-1-yl)benzenesulfonates as new antimicrotubule agents

We previously discovered a novel family of antimicrotubule agents designated as phenyl 4-(2-oxoimidazolidin-1-yl)benzenesulfonates (PIB-SOs). In this study, we evaluated the effect of the difluorination of the aromatic ring bearing the imidazolidin-2-one moiety (ring A) at positions 3, 5 and 2, 6 on their antiproliferative activity on four cancer cell lines, their ability to disrupt the microtubules and their toxicity toward chick embryos. We thus synthesized, characterized and biologically evaluated 24 new difluorinated PIB-SO derivatives designated as phenyl 3,5-difluoro-4-(2-oxoimidazolidin-1-yl)benzenesulfonates (3,5-PFB-SOs, 4-15) and phenyl 2,6-difluoro-4-(2-oxoimidazolidin-1-yl)benzenesulfonates (2,6-PFB-SOs, 16-27). The concentration of the drug required to inhibit cell growth by 50% (IC50) of 3,5-PFB-SOs is over 1000 nM while most of 2,6-PFB-SOs exhibit IC50 in the nanomolar range (23-900 nM). Furthermore, the most potent 2,6-PFB-SOs 19, 26 and 27 arrest the cell cycle progression in G2/M phase, induce cytoskeleton disruption and impair microtubule polymerization. Docking studies also show that the most potent 2,6-PFB-SOs 19, 21, 24, 26 and 27 have binding affinity toward the colchicine-binding site (C-BS). Moreover, their antiproliferative activity is not affected by antimicrotubule- and multidrug-resistant cell lines. Besides, they exhibit improved in vitro hepatic stability in the mouse, rat and human microsomes compared to their non-fluorinated counterparts. They also showed theoretical pharmacokinetic, physicochemical and drug-like properties suited for further in vivo assays. In addition, they exhibit low to no systemic toxicity toward chick embryos. Finally, our study evidences that PIB-SOs must be fluorinated in specific positions on ring A to maintain both their antiproliferative activity and their biological activity toward microtubules.

Design, Synthesis, and Evaluation of Biological Activity of Ferrocene-Ispinesib Hybrids: Impact of a Ferrocenyl Group on the Antiproliferative and Kinesin Spindle Protein Inhibitory Activity

With the aim to combine more than one biologically-active component in a single molecule, derivatives of ispinesib and its (S) analogue were prepared that featured ferrocenyl moieties or bulky organic substituents. Inspired by the strong kinesin spindle protein (KSP) inhibitory activity of ispinesib, the compounds were investigated for their antiproliferative activity. Among these compounds, several derivatives demonstrated significantly higher antiproliferative activity than ispinesib with nanomolar IC50 values against cell lines. Further evaluation indicated that the antiproliferative activity is not directly correlated with their KSP inhibitory activity while docking suggested that several of the derivatives may bind in a manner similar to ispinesib. In order to investigate the mode of action further, cell cycle analysis and reactive oxygen species formation were investigated. The improved antiproliferative activity of the most active compounds may be assigned to synergic effects of various factors such as KSP inhibitory activity due to the ispinesib core and ability to generate ROS and induce mitotic arrest.

Organometallic Ru, Os, Rh and Ir half-sandwich conjugates of ispinesib - impact of the organometallic group on the antimitotic activity

Antimitotic agents are among the most important drugs used in anticancer therapy. Kinesin spindle protein (KSP) was proposed as a promising target for new antimitotic drugs. Herein, we report the synthesis of Ru, Os, Rh, and Ir half-sandwich complexes with the KSP inhibitor ispinesib and its (S)-enantiomer. Conjugation of the organometallic moiety with ispinesib and its (S)-enantiomer resulted in a significantly increased cytotoxicity of up to 5.6-fold compared to the parent compounds, with IC50 values in the nanomolar range. The most active derivatives were the ispinesib Ru and Rh conjugates which were able to generate reactive oxygen species (ROS), which may at least partially explain their high cytotoxicity. At the same time, the Os and Ir derivatives acted as KSP inhibitors with no effects on ROS generation.

Synergy between inhibitors of two mitotic spindle assembly motors undermines an adaptive response

Mitosis is the cellular process that ensures accurate segregation of the cell's genetic material into two daughter cells. Mitosis is often deregulated in cancer; thus drugs that target mitosis-specific proteins represent attractive targets for anticancer therapy. Numerous inhibitors have been developed against kinesin-5 Eg5, a kinesin essential for bipolar spindle assembly. Unfortunately, Eg5 inhibitors (K5Is) have been largely ineffective in the clinic, possibly due to the activity of a second kinesin, KIF15, that can suppress the cytotoxic effect of K5Is by driving spindle assembly through an Eg5-independent pathway. We hypothesized that pairing of K5Is with small molecule inhibitors of KIF15 will be more cytotoxic than either inhibitor alone. Here we present the results of a high-throughput screen from which we identified two inhibitors that inhibit the motor activity of KIF15 both in vitro and in cells. These inhibitors selectively inhibit KIF15 over other molecular motors and differentially affect the ability of KIF15 to bind microtubules. Finally, we find that chemical inhibition of KIF15 reduces the ability of cells to acquire resistance to K5Is, highlighting the centrality of KIF15 to K5I resistance and the value of these inhibitors as tools with which to study KIF15 in a physiological context.

The microtubule cytoskeleton: An old validated target for novel therapeutic drugs

Compounds targeting microtubules are widely used in cancer therapy with a proven efficacy. However, because they also target non-cancerous cells, their administration leads to numerous adverse effects. With the advancement of knowledge on the structure of tubulin, the regulation of microtubule dynamics and their deregulation in pathological processes, new therapeutic strategies are emerging, both for the treatment of cancer and for other diseases, such as neuronal or even heart diseases and parasite infections. In addition, a better understanding of the mechanism of action of well-known drugs such as colchicine or certain kinase inhibitors contributes to the development of these new therapeutic approaches. Nowadays, chemists and biologists are working jointly to select drugs which target the microtubule cytoskeleton and have improved properties. On the basis of a few examples this review attempts to depict the panorama of these recent advances.

New antiproliferative agents derived from tricyclic 3,4-dihydrobenzo[4,5]imidazo[1,2-a][1,3,5]triazine scaffold: Synthesis and pharmacological effects

A series of novel 3,4-dihydrobenzo[4,5]imidazo[1,2-a][1,3,5]triazine (BIT) derivatives were designed and synthesized. In vitro antiproliferative activity was detected toward two human colorectal adenocarcinoma cell lines (CaCo-2 and HT-29) and one human dermal microvascular endothelial cell line (HMVEC-d). The most active compounds, namely 2-4 and 8, were further investigated to clarify the mechanism behind their biological activity. Through immunofluorescence assay, we identified the target of these molecules to be the microtubule cytoskeleton with subsequent formation of dense microtubule accumulation, particularly at the periphery of the cancer cells, as observed in paclitaxel-treated cells. Overall, these results highlight BIT derivatives as robust and feasible candidates deserving to be further developed in the search for novel potent antiproliferative microtubule-targeting agents.

A novel pyroptosis-related signature predicts prognosis and response to treatment in breast carcinoma

Background: Pyroptosis is a new form of programmed cell death (PCD), also known as cellular inflammatory necrosis. Its discovery has resulted in a novel approach to the progression and medication resistance of breast cancer (BC). However, there is still a significant gap in the investigation of pyroptosis-related genes in BC.

Methods: The mRNA expression profiles and clinical data of BC patients were obtained from the Gene Expression Omnibus (GEO) and The Cancer Genome Atlas (TCGA) databases. Then, using the TCGA cohort, we created a predictive multigene signature including pyroptosis-related genes and verified it using the two GEO cohorts. A pyroptosis-related gene signature was created by combining several bioinformatics and statistical methodologies to predict patient prognosis and responses to immunotherapy and chemotherapy. Furthermore, a nomogram based on the gene signature and clinicopathological markers was created to better classify the risk and quantify the risk assessment of individual patients.

Results: A pyroptosis-related gene signature consisting of 15 genes was established. The pyroptosis-related gene signature classified the patients into two groups: high-risk and low-risk. When combined with clinical variables, the risk score was discovered to be an independent predictor of overall survival (OS) in BC patients. Some immunological pathways and genes were linked to pyroptosis, according to Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) evaluations. Patients in the high-risk group had a worse prognosis and were not very sensitive to immunotherapy. However, several chemotherapeutic agents were predicted to have greater potential for patients in the high-risk group. Finally, a nomogram was developed that included a classifier based on the 15 pyroptosis-related genes, tumor stage, age, and histologic grade. This nomogram demonstrated good classification capacity and might help with clinical decision-making in BC.

Antineoplastics Encapsulated in Nanostructured Lipid Carriers

Ideally, antineoplastic treatment aims to selectively eradicate cancer cells without causing systemic toxicity. A great number of antineoplastic agents (AAs) are available nowadays, with well-defined therapeutic protocols. The poor bioavailability, non-selective action, high systemic toxicity, and lack of effectiveness of most AAs have stimulated the search for novel chemotherapy protocols, including technological approaches that provide drug delivery systems (DDS) for gold standard medicines. Nanostructured lipid carriers (NLC) are DDS that contain a core of solid and lipid liquids stabilised by surfactants. NLC have high upload capacity for lipophilic drugs, such as the majority of AAs. These nanoparticles can be prepared with a diversity of biocompatible (synthetic or natural) lipid blends, administered by different routes and functionalised for targeting purposes. This review focused on the research carried out from 2000 to now, regarding NLC formulations for AAs (antimetabolites, antimitotics, alkylating agents, and antibiotics) encapsulation, with special emphasis on studies carried out in vivo. NLC systems for codelivery of AAs were also considered, as well as those for non-classical drugs and therapies (natural products and photosensitisers). NLC have emerged as powerful DDS to improve the bioavailability, targeting and efficacy of antineoplastics, while decreasing their toxic effect in the treatment of different types of cancer.

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.

Future prospects for mitosis-targeted antitumor therapies

Dysregulation of cell cycle progression is a hallmark of cancer cells. In recent years, efforts have been devoted to the development of new therapies that target proteins involved in cell cycle regulation and mitosis. Novel targeted antimitotic drugs include inhibitors of aurora kinase family, polo-like kinase 1, Mps1, Eg5, CENP-5 and the APC/cyclosome complex. While certain new inhibitors reached the clinical trial stage, most were discontinued due to negative results. However, these therapies should not be readily dismissed. Based on recent advances concerning their mechanisms of action, new strategies could be devised to increase their efficacy and promote further clinical trials. Here we discuss three main lines of action to empower these therapeutic approaches: increasing cell death signals during mitotic arrest, targeting senescent cells and facilitating antitumor immune response through immunogenic cell death (ICD).

Effect of KIF22 on promoting proliferation and migration of gastric cancer cells via MAPK-ERK pathways

Background

Gastric cancer (GC) is one of the most globally prevalent cancers in the world. The pathogenesis of GC has not been fully elucidated, and there still lacks effective targeted therapeutics. The influence of altered kinesin superfamily protein 22 (KIF22) expression in GC progression is still unclearly. The aim of this study was to investigate the KIF22 effects on GC and related mechanisms.

Methods

Gastric carcinoma tissues and matching non-cancerous tissues were collected from patients with GC who have accepted a radical gastrectomy in Lanzhou University Second Hospital from May 2013 to December 2014. The expression of KIF22 was examined in GC of 67 patients and 20 para-carcinoma tissues by immunochemical staining. The relationship between the expression of KIF22 and clinicopathologic characteristics was next investigated in the remaining 52 patients except for 15 patients who did not complete follow-up for 5 years. Cell viability was performed via 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) test and colony formation assay in the MGC-803 and BGC-823 GC cells. Cell scratch and trans-well invasion assay was performed to assess migration ability in the MGC-803 and BGC-823 GC cells. Gene set enrichment analysis (GSEA) pathway enrichment analysis was performed to explore the potential functions. Cell cycle was detected by flow cytometry. In addition, the two GC cell lines were used to elucidate the underlying mechanism of KIF22 in GC in vitro via assessing the effects on mitogen-activated protein kinase and extracellular regulated protein kinases (MAPK/ERK) signal transduction pathway-related expressions by Western blotting assays. The differences were compared by t tests, one-way analysis of variance, and Chi-squared tests.

Results

The study showed that KIF22 was up-regulated in GC, and KIF22 high expression was significantly related to differentiation degree (χ² = 12.842, P = 0.002) and poorly overall survivals. GSEA pathway enrichment analysis showed that KIF22 was correlated with the cell cycle. Silence of KIF22 decreased the ability of the proliferation and migration in gastric cells, induced G1/S phase cell cycle arrest via regulating the MAPK-ERK pathways.

Conclusions

KIF22 protein level was negatively correlated with prognosis. KIF22 knockdown might inhibit proliferation and metastasis of GC cells via the MAPK-ERK signaling pathway.

The high-resolution X-ray structure of vinca-domain inhibitors of microtubules provides a rational approach for drug design

Tubulin vinca-domain ligands can inhibit microtubule polymerization, causing cell death in mitosis, and their potential against multiple cancer types has been demonstrated. However, due to drug resistance and toxicities, development of novel vinca-domain ligands is still needed. In this study, we determined the high-resolution crystal structures of vinorelbine, YXD, and Phomopsin A in complex with tubulin at 2.5 Å. Additionally, we recapitulated all previously published high-resolution crystal structures of the vinca binding site to reveal critical residues and the molecular mechanism of vinca-domain ligands interacting with tubulin. Furthermore, we designed putatively novel triazolopyrimidine derivatives by introducing secondary amine groups to establish salt-bridge and H-bond interactions with Asp179^β1 and Asn329^α2 . Our studies provided the structural basis for designing novel tubulin vinca-domain ligands.

Nanomechanics in Monitoring the Effectiveness of Drugs Targeting the Cancer Cell Cytoskeleton

Increasing attention is devoted to the use of nanomechanics as a marker of various pathologies. Atomic force microscopy (AFM) is one of the techniques that could be applied to quantify the nanomechanical properties of living cells with a high spatial resolution. Thus, AFM offers the possibility to trace changes in the reorganization of the cytoskeleton in living cells. Impairments in the structure, organization, and functioning of two main cytoskeletal components, namely, actin filaments and microtubules, cause severe effects, leading to cell death. That is why these cytoskeletal components are targets for antitumor therapy. This review intends to describe the gathered knowledge on the capability of AFM to trace the alterations in the nanomechanical properties of living cells induced by the action of antitumor drugs that could translate into their effectiveness.

Metal-Dependent Cytotoxic and Kinesin Spindle Protein Inhibitory Activity of Ru, Os, Rh, and Ir Half-Sandwich Complexes of Ispinesib-Derived Ligands

Ispinesib is a potent inhibitor of kinesin spindle protein (KSP), which has been identified as a promising target for antimitotic anticancer drugs. Herein, we report the synthesis of half-sandwich complexes of Ru, Os, Rh, and Ir bearing the ispinesib-derived N,N-bidentate ligands (R)- and (S)-2-(1-amino-2-methylpropyl)-3-benzyl-7-chloroquinazolin-4(3H)-one and studies on their chemical and biological properties. Using the enantiomerically pure (R)- and (S)-forms of the ligand, depending on the organometallic moiety, either the S_M,R or R_M,S diastereomers, respectively, were observed in the molecular structures of the Ru- and Os(cym) (cym = η⁶-p-cymene) compounds, whereas the R_M,R or S_M,S diastereomers were found for the Rh- and Ir(Cp*) (Cp* = η⁵-pentamethylcyclopentadienyl) derivatives. However, density functional theory (DFT) calculations suggest that the energy difference between the diastereomers is very small, and therefore a mixture of both will be present in solution. The organometallics exhibited varying antiproliferative activity in a series of human cancer cell lines, with the complexes featuring the (R)-enantiomer of the ligand being more potent than the (S)-configured counterparts. Notably, the Rh and Ir complexes demonstrated high KSP inhibitory activity, even at 1 nM concentration, which was independent of the chirality of the ligand, whereas the Ru and especially the Os derivatives were much less active.

Antineoplastic Agents: Environmental Prevalence and Adverse Outcomes in Aquatic Organisms

Cancer is the second leading cause of death worldwide, with 9.6 million cancer-related deaths in 2018. Cancer incidence has increased over time, and so has the prescription rate of chemotherapeutic drugs. These pharmaceuticals, known as antineoplastic agents, enter the aquatic environment via human excretion and wastewater. The objectives of the present critical review were to investigate the risk of antineoplastics to aquatic species and to summarize the current state of knowledge regarding their levels in the environment, because many antineoplastics are not adequately removed during wastewater treatment. We conducted 2 separate literature reviews to synthesize data on the global environmental prevalence and toxicity of antineoplastics. The antineoplastics most frequently detected in the environment included cyclophosphamide, ifosfamide, tamoxifen, methotrexate, and 5-fluorouracil; all were detectable in multiple water sources, including effluent and surface waters. These antineoplastics span 3 different mechanistic classes, with cyclophosphamide and ifosfamide classified as alkylating agents, tamoxifen as a hormonal agent, and methotrexate and 5-fluorouracil as antimetabolites. Studies that characterize the risk of antineoplastics released into aquatic environments are scarce. We summarize the biological impacts of the most environmentally prevalent antineoplastics on aquatic organisms and propose an adverse outcome pathway for cyclophosphamide and ifosfamide, 2 widely prescribed drugs with a similar immunotoxic mode of action. Acute and chronic ecotoxicity studies using aquatic models are needed for risk characterization of antineoplastics. Environ Toxicol Chem 2020;39:967-985. © 2020 SETAC.

Recent advances of therapeutic targets based on the molecular signature in breast cancer: genetic mutations and implications for current treatment paradigms

Breast cancer is the most common malignancy in women all over the world. Genetic background of women contributes to her risk of having breast cancer. Certain inherited DNA mutations can dramatically increase the risk of developing certain cancers and are responsible for many of the cancers that run in some families. Regarding the widespread multigene panels, whole exome sequencing is capable of providing the evaluation of genetic function mutations for development novel strategy in clinical trials. Targeting the mutant proteins involved in breast cancer can be an effective therapeutic approach for developing novel drugs. This systematic review discusses gene mutations linked to breast cancer, focusing on signaling pathways that are being targeted with investigational therapeutic strategies, where clinical trials could be potentially initiated in the future are being highlighted.

Delivering Combination Chemotherapies and Targeting Oncogenic Pathways via Polymeric Drug Delivery Systems

The side-effects associated with chemotherapy necessitates better delivery of chemotherapeutics to the tumor. Nanoparticles can load higher amounts of drug and improve delivery to tumors, increasing the efficacy of treatment. Polymeric nanoparticles, in particular, have been used extensively for chemotherapeutic delivery. This review describes the efforts made to deliver combination chemotherapies and inhibit oncogenic pathways using polymeric drug delivery systems. Combinations of chemotherapeutics with other drugs or small interfering RNA (siRNA) combinations have been summarized. Special attention is given to the delivery of drug combinations that involve either paclitaxel or doxorubicin, two popular chemotherapeutics in clinic. Attempts to inhibit specific pathways for oncotherapy have also been described. These include inhibition of oncogenic pathways (including those involving HER2, EGFR, MAPK, PI3K/Akt, STAT3, and HIF-1α), augmentation of apoptosis by inhibiting anti-apoptosis proteins (Bcl-2, Bcl-xL, and survivin), and targeting dysregulated pathways such as Wnt/β-catenin and Hedgehog.

Neurymenolide A, a Novel Mitotic Spindle Poison from the New Caledonian Rhodophyta Phacelocarpus neurymenioides

The marine α-pyrone macrolide neurymenolide A was previously isolated from the Fijian red macroalga, Neurymenia fraxinifolia, and characterized as an antibacterial agent against antibiotic-resistant strains that also exhibited moderate cytotoxicity in vitro against cancer cell lines. This compound was also shown to exhibit allelopathic effects on Scleractinian corals. However, to date no mechanism of action has been described in the literature. The present study showed, for the first time, the isolation of neurymenolide A from the New Caledonian Rhodophyta, Phacelocarpus neurymenioides. We confirmed the compound’s moderate cytotoxicity in vitro against several human cell lines, including solid and hematological malignancies. Furthermore, we combined fluorescence microscopy and flow cytometry to demonstrate that treatment of U-2 OS osteosarcoma human cells with neurymenolide A could block cell division in prometaphase by inhibiting the correct formation of the mitotic spindle, which induced a mitotic catastrophe that led to necrosis and apoptosis. Absolute configuration of the stereogenic center C-17 of neurymenolide A was deduced by comparison of the experimental and theoretical circular dichroism spectra. Since the total synthesis of this compound has already been described, our findings open new avenues in cancer treatment for this class of marine molecules, including a new source for the natural product.

Towards modern anticancer agents that interact with tubulin

Tubulin is the primary target of an ever growing number of natural, semisynthetic and synthetic products as potential anticancer agents. The mechanisms of interaction of these molecules with tubulin are varied. These drug classes have shown to inhibit effectively several cancer types with IC₅₀ from midmicromolar to low nanomolar concentrations. However, some limiting obstacles still remain, such as the development of multidrug resistance and cytotoxicity. We have reviewed recent advances in different classes of tubulin binding agents, including colchicine site agents, Vinca alkaloids, tryprostatins, moroidin, hemiasterlin, diazonamide, taxanes, epothilones and laulimalide.

Natural products as new antimitotic compounds for anticancer drug development

Cell cycle control genes are frequently mutated in cancer cells, which usually display higher rates of proliferation than normal cells. Dysregulated mitosis leads to genomic instability, which contributes to tumor progression and aggressiveness. Many drugs that disrupt mitosis have been studied because they induce cell cycle arrest and tumor cell death. These antitumor compounds are referred to as antimitotics. Vinca alkaloids and taxanes are natural products that target microtubules and inhibit mitosis, and their derivatives are among the most commonly used drugs in cancer therapy worldwide. However, severe adverse effects such as neuropathies are frequently observed during treatment with microtubule-targeting agents. Many efforts have been directed at developing improved antimitotics with increased specificity and decreased likelihood of inducing side effects. These new drugs generally target specific components of mitotic regulation that are mainly or exclusively expressed during cell division, such as kinases, motor proteins and multiprotein complexes. Such small molecules are now in preclinical studies and clinical trials, and many are products or derivatives from natural sources. In this review, we focused on the most promising targets for the development of antimitotics and discussed the advantages and disadvantages of these targets. We also highlighted the novel natural antimitotic agents under investigation by our research group, including combretastatins, withanolides and pterocarpans, which show the potential to circumvent the main issues in antimitotic therapy.

New chalcone derivative exhibits antiproliferative potential by inducing G2/M cell cycle arrest, mitochondrial-mediated apoptosis and modulation of MAPK signalling pathway

In the present study, we investigated antiproliferative activity of seven newly synthesized chalcone derivatives. Among tested compounds, (2 E)-3-(acridin-9-yl)-1-(2,6-dimethoxyphenyl)prop-2-en-1-one (1C) was the most potent with IC₅₀ = 4.1 μmol/L in human colorectal HCT116 cells and was selected for further studies. Inhibition of cell proliferation was associated with cell cycle arrest in G2/M phase and dysregulation of α, α1 and β5 tubulins. Moreover, 1C caused disruption of the mitochondrial membrane potential and increased number of cells with sub G0/G1 DNA content which is considered as marker of apoptosis. Apoptosis was confirmed by annexin V/PI and AO/PI staining. Furthermore, we found increased concentration of cytochrome c, Smac/Diablo and increased caspase-3 and caspase-9 activity, cleavage of PARP as well as activation of DNA repair mechanisms in 1C-treated HCT116 cancer cells. Moreover this chalcone derivative up-regulated proapoptotic Bax expression and down-regulated antiapoptotic Bcl-2 and Bcl-xL expression. Additionally, 1C treatment led to modulation of MAPKs and Akt signalling pathways. In conclusion, our data showed ability of 1C to suppress cancel cell growth and provide the rationale for further in vivo study.

Is inflammatory micronucleation the key to a successful anti-mitotic cancer drug?

Paclitaxel is a successful anti-cancer drug that kills cancer cells in two-dimensional culture through perturbation of mitosis, but whether it causes tumour regression by anti-mitotic actions is controversial. Drug candidates that specifically target mitosis, including inhibitors of kinesin-5, AurkA, AurkB and Plk1, disappointed in the clinic. Current explanations for this discrepancy include pharmacokinetic differences and hypothetical interphase actions of paclitaxel. Here, we discuss post-mitotic micronucleation as a special activity of taxanes that might explain their higher activity in solid tumours. We review data showing that cells which exit mitosis in paclitaxel are highly micronucleated and suffer post-mitotic DNA damage, and that these effects are much stronger for paclitaxel than kinesin-5 inhibitors. We propose that post-mitotic micronucleation promotes inflammatory signalling via cGAS–STING and other pathways. In tumours, this signalling may recruit cytotoxic leucocytes, damage blood vessels and prime T-cell responses, leading to whole-tumour regression. We discuss experiments that are needed to test the micronucleation hypothesis, and its implications for novel anti-mitotic targets and enhancement of taxane-based therapies.

Dynamics of human protein kinase Aurora A linked to drug selectivity

Protein kinases are major drug targets, but the development of highly-selective inhibitors has been challenging due to the similarity of their active sites. The observation of distinct structural states of the fully-conserved Asp-Phe-Gly (DFG) loop has put the concept of conformational selection for the DFG-state at the center of kinase drug discovery. Recently, it was shown that Gleevec selectivity for the Tyr-kinase Abl was instead rooted in conformational changes after drug binding. Here, we investigate whether protein dynamics after binding is a more general paradigm for drug selectivity by characterizing the binding of several approved drugs to the Ser/Thr-kinase Aurora A. Using a combination of biophysical techniques, we propose a universal drug-binding mechanism, that rationalizes selectivity, affinity and long on-target residence time for kinase inhibitors. These new concepts, where protein dynamics in the drug-bound state plays the crucial role, can be applied to inhibitor design of targets outside the kinome.

Protein kinases are a family of enzymes found in all living organisms. These enzymes help to control many biological processes, including cell division. When particular protein kinases do not work correctly, cells may start to divide uncontrollably, which can lead to cancer. One example is the kinase Aurora A, which is over-active in many common human cancers. As a result, researchers are currently trying to design drugs that reduce the activity of Aurora A in the hope that these could form new anticancer treatments.

In general, drugs are designed to be as specific in their action as possible to reduce the risk of harmful side effects to the patient. Designing a drug that affects a single protein kinase, however, is difficult because there are hundreds of different kinases in the body, all with similar structures. Because drugs often work by binding to specific structural features, a drug that targets one protein kinase can often alter the activity of a large number of others too.

Gleevec is a successful anti-leukemia drug that specifically works on one target kinase, producing minimal side effects. It was recently discovered that the drug works through a phenomenon called ‘induced fit’. This means that after the drug binds it causes a change in the enzyme’s overall shape that alters the activity of the enzyme. The shape change is complex, and so even small structural differences can change the effect of a particular drug.

Do other drugs that target other protein kinases also produce induced fit effects? To find out, Pitsawong, Buosi, Otten, Agafonov et al. studied how three anti-cancer drugs interact with Aurora A: two drugs specifically designed to switch off Aurora A, and Gleevec (which does not target Aurora A).

The two drugs that specifically target Aurora A were thought to work by targeting one structural feature of the enzyme. However, the biochemical and biophysical experiments performed by Pitsawong et al. revealed that these drugs instead work through an induced fit effect. By contrast, Gleevec did not trigger an induced fit on Aurora A and so bound less tightly to it.

In light of these results, Pitsawong et al. suggest that future efforts to design drugs that target protein kinases should focus on exploiting the induced fit process. This will require more research into the structure of particular kinases.

Universal response in the RKO colon cancer cell line to distinct antimitotic therapies

Both classic and newer antimitotics commonly induce a prolonged mitotic arrest in cell culture. During arrest, cells predominantly undergo one of two fates: cell death by apoptosis, or mitotic slippage and survival. To refine this binary description, a quantitative understanding of these cell responses is needed. Herein, we propose a quantitative description of the kinetics of colon carcinoma RKO cell fates in response to different antimitotics, using data from the single cell experiments of Gascoigne and Taylor (2008). The mathematical model is calibrated using the in vitro experiments of Gascoigne and Taylor (2008). We show that the time-dependent probability of cell death or slippage is universally identical for monastrol, nocodazole and two different doses of AZ138, but significantly different for taxol. Death and slippage responses across drugs can be characterized by Gamma distributions. We demonstrate numerically that these rates increase with prolonged mitotic arrest. Our model demonstrates that RKO cells exhibit a triphasic response - first, remain in mitosis, then undergo fast and slow transition, respectively- dependent on the length of mitotic arrest and irrespective of cell fate, drug type or dose.

UBASH3B-mediated silencing of the mitotic checkpoint: Therapeutic perspectives in cancer

Defects in mitosis can lead to aneuploidy, which is a common feature of human cancers. Spindle Assembly Checkpoint (SAC) controls fidelity of chromosome segregation in mitosis to prevent aneuploidy. The ubiquitin receptor protein Ubiquitin Associated and SH3 Domain Containing B (UBASH3B) was recently found to control SAC silencing and faithful chromosome segregation by relocalizing Aurora B kinase to the mitotic microtubules. Accordingly, loss and gain of function of UBASH3B have strong effects on mitotic progression. Downregulation of UBASH3B prevents SAC satisfaction leading to inhibition of chromosome segregation, mitotic arrest, and cell death. In contrast, increased cellular levels of UBASH3B trigger premature and uncontrolled chromosome segregation. Interestingly, elevated levels of UBASH3B were found in aggressive tumors. Therefore, we raised the question whether the oncogenic potential of UBASH3B is linked to its role in chromosome segregation. Here we show that in cancer cells expressing high levels of UBASH3B and SAC proteins, downregulation of UBASH3B, can further potentiate SAC response inducing mitotic arrest and cell death. Moreover, data mining approaches identified a correlation between mRNA levels of UBASH3B and SAC components in a set of primary patient tumors including kidney and liver carcinomas. Thus, inhibition of UBASH3B may offer an attractive therapeutic perspective for cancers.

Targeting TAO Kinases Using a New Inhibitor Compound Delays Mitosis and Induces Mitotic Cell Death in Centrosome Amplified Breast Cancer Cells

Thousand-and-one amino acid kinases (TAOK) 1 and 2 are activated catalytically during mitosis and can contribute to mitotic cell rounding and spindle positioning. Here, we characterize a compound that inhibits TAOK1 and TAOK2 activity with IC50 values of 11 to 15 nmol/L, is ATP-competitive, and targets these kinases selectively. TAOK inhibition or depletion in centrosome-amplified SKBR3 or BT549 breast cancer cell models increases the mitotic population, the percentages of mitotic cells displaying amplified centrosomes and multipolar spindles, induces cell death, and inhibits cell growth. In contrast, nontumorigenic and dividing bipolar MCF-10A breast cells appear less dependent on TAOK activity and can complete mitosis and proliferate in the presence of the TAOK inhibitor. We demonstrate that TAOK1 and TAOK2 localize to the cytoplasm and centrosomes respectively during mitosis. Live cell imaging shows that the TAOK inhibitor prolongs the duration of mitosis in SKBR3 cells, increases mitotic cell death, and reduces the percentages of cells exiting mitosis, whereas MCF-10A cells continue to divide and proliferate. Over 80% of breast cancer tissues display supernumerary centrosomes, and tumor cells frequently cluster extra centrosomes to avoid multipolar mitoses and associated cell death. Consequently, drugs that stimulate centrosome declustering and induce multipolarity are likely to target dividing centrosome-amplified cancer cells preferentially, while sparing normal bipolar cells. Our results demonstrate that TAOK inhibition can enhance centrosome declustering and mitotic catastrophe in cancer cells, and these proteins may therefore offer novel therapeutic targets suitable for drug inhibition and the potential treatment of breast cancers, where supernumerary centrosomes occur. Mol Cancer Ther; 16(11); 2410-21. ©2017 AACR.

Ginkgetin induces G2-phase arrest in HCT116 colon cancer cells through the modulation of b‑Myb and miRNA34a expression

Ginkgetin has been reported to display antitumor activity. However, the relevant pathway integrating cell cycle regulation and signaling pathways involved in growth inhibition in CRC cells remains to be identified. In this study, ginkgetin-treated HCT116 CRC cells exhibited significant dose-dependent growth inhibition with a GI50 value of 4.0 µM for 48-h treatment, together with apoptosis, via G2-phase cell cycle arrest. When HCT116 cells were treated with 10 µM ginkgetin for 48 h, the percentage of cells in G2/M phase increased by 2.2-fold (43.25%) versus the untreated control (19.69%). Ginkgetin regulated the expression of genes that are critically involved in G2 phase arrest cells, such as b‑Myb, CDC2 and cyclin B1. Furthermore, we found that the suppression of b‑Myb expression by ginkgetin was rescued ~5.1-fold by treatment with a miR-34a inhibitor (500 nM) and b‑Myb was downregulated by >80% by 100 nM miR‑34a mimic. These data suggest that the miRNA34a/b‑Myb/cyclin B1 cascade plays a critical role in ginkgetin-induced G2 cell cycle arrest, as well as in the inhibition of HCT116 cell proliferation. Moreover, the administration of ginkgetin (10 mg/kg) reduced tumor volumes by 36.5% and tumor weight by 37.6% in the mice xenografted with HCT116 cells relative to their vehicle-treated counterparts. Therefore, ginkgetin is the first compound shown to regulate b‑Myb by modulating miR-34a, and we suggest the use of ginkgetin as an inducer of G2 arrest for the treatment of CRC.

Cell death response to anti-mitotic drug treatment in cell culture, mouse tumor model and the clinic

Anti-mitotic cancer drugs include classic microtubule-targeting drugs, such as taxanes and vinca alkaloids, and the newer spindle-targeting drugs, such as inhibitors of the motor protein; Kinesin-5 (aka KSP, Eg5, KIF11); and Aurora-A, Aurora-B and Polo-like kinases. Microtubule-targeting drugs are among the first line of chemotherapies for a wide spectrum of cancers, but patient responses vary greatly. We still lack understanding of how these drugs achieve a favorable therapeutic index, and why individual patient responses vary. Spindle-targeting drugs have so far shown disappointing results in the clinic, but it is possible that certain patients could benefit if we understand their mechanism of action better. Pre-clinical data from both cell culture and mouse tumor models showed that the cell death response is the most variable point of the drug action. Hence, in this review we focus on current mechanistic understanding of the cell death response to anti-mitotics. We first draw on extensive results from cell culture studies, and then cross-examine them with the more limited data from animal tumor models and the clinic. We end by discussing how cell type variation in cell death response might be harnessed to improve anti-mitotic chemotherapy by better patient stratification, new drug combinations and identification of novel targets for drug development.

Mitotic cell death induction by targeting the mitotic spindle with tubulin-inhibitory indole derivative molecules

Tubulin-targeting molecules are widely used cancer therapeutic agents. They inhibit microtubule-based structures, including the mitotic spindle, ultimately preventing cell division. The final fates of microtubule-inhibited cells are however often heterogeneous and difficult to predict. While recent work has provided insight into the cell response to inhibitors of microtubule dynamics (taxanes), the cell response to tubulin polymerization inhibitors remains less well characterized. Arylthioindoles (ATIs) are recently developed tubulin inhibitors. We previously identified ATI members that effectively inhibit tubulin polymerization in vitro and cancer cell growth in bulk cell viability assays. Here we characterise in depth the response of cancer cell lines to five selected ATIs. We find that all ATIs arrest mitotic progression, yet subsequently yield distinct cell fate profiles in time-lapse recording assays, indicating that molecules endowed with similar tubulin polymerization inhibitory activity in vitro can in fact display differential efficacy in living cells. Individual ATIs induce cytological phenotypes of increasing severity in terms of damage to the mitotic apparatus. That differentially triggers MCL-1 down-regulation and caspase-3 activation, and underlies the terminal fate of treated cells. Collectively, these results contribute to define the cell response to tubulin inhibitors and pinpoint potentially valuable molecules that can increase the molecular diversity of tubulin-targeting agents.

Modeling Cancer Cell Growth Dynamics In vitro in Response to Antimitotic Drug Treatment

Investigating the role of intrinsic cell heterogeneity emerging from variations in cell-cycle parameters and apoptosis is a crucial step toward better informing drug administration. Antimitotic agents, widely used in chemotherapy, target exclusively proliferative cells and commonly induce a prolonged mitotic arrest followed by cell death via apoptosis. In this paper, we developed a physiologically motivated mathematical framework for describing cancer cell growth dynamics that incorporates the intrinsic heterogeneity in the time individual cells spend in the cell-cycle and apoptosis process. More precisely, our model comprises two age-structured partial differential equations for the proliferative and apoptotic cell compartments and one ordinary differential equation for the quiescent compartment. To reflect the intrinsic cell heterogeneity that governs the growth dynamics, proliferative and apoptotic cells are structured in "age," i.e., the amount of time remaining to be spent in each respective compartment. In our model, we considered an antimitotic drug whose effect on the cellular dynamics is to induce mitotic arrest, extending the average cell-cycle length. The prolonged mitotic arrest induced by the drug can trigger apoptosis if the time a cell will spend in the cell cycle is greater than the mitotic arrest threshold. We studied the drug's effect on the long-term cancer cell growth dynamics using different durations of prolonged mitotic arrest induced by the drug. Our numerical simulations suggest that at confluence and in the absence of the drug, quiescence is the long-term asymptotic behavior emerging from the cancer cell growth dynamics. This pattern is maintained in the presence of small increases in the average cell-cycle length. However, intermediate increases in cell-cycle length markedly decrease the total number of cells and can drive the cancer population to extinction. Intriguingly, a large "switch-on/switch-off" increase in the average cell-cycle length maintains an active cell population in the long term, with oscillating numbers of proliferative cells and a relatively constant quiescent cell number.

Anti-Melanoma Activities of Haspin Inhibitor CHR-6494 Deployed as a Single Agent or in a Synergistic Combination with MEK Inhibitor

Background: Melanoma is a heterogeneous malignancy that presents an immense challenge in therapeutic development. Recent approaches targeting the oncogenic MAP kinase pathways have shown tremendous improvement in the overall survival of patients with advanced melanoma. However, there is still an urgent need for identification of new strategies to overcome drug resistances and to improve therapeutic efficacy. Haspin (Haploid Germ Cell-Specific Nuclear Protein Kinase) belongs to a selected group of mitotic kinases and is required for normal mitosis progression. In contrast to inhibitors of other mitotic kinases, anti-tumor potential of haspin inhibitors has not been well explored. Herein, we aim to examine effects of CHR-6494, a small molecule inhibitor of haspin, in melanoma cells.

Methods: Anti-tumor activities of the haspin inhibitor CHR-6494 were tested in a number of melanoma cell lines either as a single agent or in combination with the MEK inhibitor Trametinib (GSK1120212). Experiments are based on: 1) Cell viability determined by the crystal violet staining assay; 2) apoptotic responses measured by the caspase 3/7 activity assay and western blot analysis for the level of cleaved PARP (Poly ADP-Ribose Polymerase); 3) cell cycle analysis conducted using flow cytometry; and 4) cell migratory ability assessed by the scratch assay and the transwell migration assay.

Results: We have found that CHR-6494 alone elicits a dose dependent inhibitory effect on the viability of several melanoma cell lines. This growth inhibition is accompanied by an increase in apoptotic responses. More importantly, CHR-6494 appears to synergize with the MEK inhibitor Trametinib in suppressing cell growth and enhancing apoptosis in both wild type and BRAFV600E mutant melanoma cell lines. Administering of these two small molecules as a combination is also capable of suppressing cell migration to a greater extent than the individual agent.

Conclusion: These results suggest that haspin can be considered as a viable anti-melanoma target, and that concomitant inhibition of haspin and MEK activities with small molecules could represent a novel therapeutic strategy with improved efficacy for treatment of melanoma.

Addressing a weakness of anticancer therapy with mitosis inhibitors: Mitotic slippage

Mitosis inhibitors, which include antimicrotubule drugs, are chemotherapy agents that induce the arrest and apoptosis of mitotic cells. Mitotic slippage, in which mitotically arrested cells exit mitosis, limits the effectiveness of mitosis inhibitors. We have discovered that the CRL2^ZYG11A/B ubiquitin ligase promotes mitotic slippage. The combination of antimicrotubule drugs and a CRL2^ZYG11A/B inhibitor prevents mitotic slippage to increase antimitotic efficacy.

ErbB Receptors and Cancer

The ErbB receptor family, also known as the EGF receptor family or type I receptor family, includes the epidermal growth factor (EGF) receptor (EGFR) or ErbB1/Her1, ErbB2/Her2, ErbB3/Her3, and ErbB4/Her4. Among all RTKs, EGFR was the first RTK identified and the first one linked to cancer. Thus, EGFR has also been the most intensively studied among all RTKs. ErbB receptors are activated after homodimerization or heterodimerization. The ErbB family is unique among the various groups of receptor tyrosine kinases (RTKs) in that ErbB3 has impaired kinase activity, while ErbB2 does not have a direct ligand. Therefore, heterodimerization is an important mechanism that allows the activation of all ErbB receptors in response to ligand stimulation. The activated ErbB receptors bind to many signaling proteins and stimulate the activation of many signaling pathways. The specificity and potency of intracellular signaling pathways are determined by positive and negative regulators, the specific composition of activating ligand(s), receptor dimer components, and the diverse range of proteins that associate with the tyrosine phosphorylated C-terminal domain of the ErbB receptors. ErbB receptors are overexpressed or mutated in many cancers, especially in breast cancer, ovarian cancer, and non-small cell lung cancer. The overexpression and overactivation of ErbB receptors are correlated with poor prognosis, drug resistance, cancer metastasis, and lower survival rate. ErbB receptors, especially EGFR and ErbB2 have been the primary choices as targets for developing cancer therapies.

Physical determinants of bipolar mitotic spindle assembly and stability in fission yeast

Mitotic spindles use an elegant bipolar architecture to segregate duplicated chromosomes with high fidelity. Bipolar spindles form from a monopolar initial condition; this is the most fundamental construction problem that the spindle must solve. Microtubules, motors, and cross-linkers are important for bipolarity, but the mechanisms necessary and sufficient for spindle assembly remain unknown. We describe a physical model that exhibits de novo bipolar spindle formation. We began with physical properties of fission-yeast spindle pole body size and microtubule number, kinesin-5 motors, kinesin-14 motors, and passive cross-linkers. Our model results agree quantitatively with our experiments in fission yeast, thereby establishing a minimal system with which to interrogate collective self-assembly. By varying the features of our model, we identify a set of functions essential for the generation and stability of spindle bipolarity. When kinesin-5 motors are present, their bidirectionality is essential, but spindles can form in the presence of passive cross-linkers alone. We also identify characteristic failed states of spindle assembly-the persistent monopole, X spindle, separated asters, and short spindle, which are avoided by the creation and maintenance of antiparallel microtubule overlaps. Our model can guide the identification of new, multifaceted strategies to induce mitotic catastrophes; these would constitute novel strategies for cancer chemotherapy.

p53-independent structure-activity relationships of 3-ring mesogenic compounds' activity as cytotoxic effects against human non-small cell lung cancer lines

BACKGROUND

We recently demonstrated the cytotoxicity of liquid crystal precursors (hereafter referred to as "mesogenic compounds") in the human non-small cell lung cancer (NSCLC) cell line A549 which carry wild-type p53. p53 mutations are observed in 50 % of NSCLC and contribute to their resistance to chemotherapy. To develop more effective and cancer-specific agents, in this study, we investigated the structure-activity relationships of mesogenic compounds with cytotoxic effects against multiple NSCLC cells.

METHODS

The pharmacological effects of mesogenic compounds were examined in human NSCLC cells (A549, LU99, EBC-1, and H1299) and normal WI-38 human fibroblast. Analyses of the cell cycle, cell-death induction, and capsases expression were performed.

RESULTS

The 3-ring compounds possessing terminal alkyl and hydroxyl groups (compounds C1-C5) showed cytotoxicity in NSCLC cells regardless of the p53 status. The compounds C1 and C3, which possess a pyrimidine at the center of the core, induced G2/M arrest, while the compounds without a pyrimidine (C2, C4, and C5) caused G1 arrest; all compounds produced caspase-mediated cell death. These events occurred in a p53-independent manner. Furthermore, it was suggested that compounds induced cell death through p53-independent DNA damage-signaling pathway. Compounds C2, C4, and C5 did not show strong cytotoxicity in WI-38 cells, whereas C1 and C3 did. However, the cytotoxicity of compound C1 against WI-38 cells was improved by modulating the terminal alkyl chain lengths of the compound.

CONCLUSIONS

We showed the p53-indepdent structure-activity relationships of mesogenic compounds related to the cytotoxic effects. These structure-activity relationships will be helpful in the development of more effective and cancer-specific agents.

Maintaining Genome Stability in Defiance of Mitotic DNA Damage

The implementation of decisions affecting cell viability and proliferation is based on prompt detection of the issue to be addressed, formulation and transmission of a correct set of instructions and fidelity in the execution of orders. While the first and the last are purely mechanical processes relying on the faithful functioning of single proteins or macromolecular complexes (sensors and effectors), information is the real cue, with signal amplitude, duration, and frequency ultimately determining the type of response. The cellular response to DNA damage is no exception to the rule. In this review article we focus on DNA damage responses in G2 and Mitosis. First, we set the stage describing mitosis and the machineries in charge of assembling the apparatus responsible for chromosome alignment and segregation as well as the inputs that control its function (checkpoints). Next, we examine the type of issues that a cell approaching mitosis might face, presenting the impact of post-translational modifications (PTMs) on the correct and timely functioning of pathways correcting errors or damage before chromosome segregation. We conclude this essay with a perspective on the current status of mitotic signaling pathway inhibitors and their potential use in cancer therapy.

N-(2-methyl-indol-1H-5-yl)-1-naphthalenesulfonamide: A novel reversible antimitotic agent inhibiting cancer cell motility

A series of compounds containing the sulfonamide scaffold were synthesized and screened for their in vitro anticancer activity against a representative panel of human cancer cell lines, leading to the identification of N-(2-methyl-1H-indol-5-yl)-1-naphthalenesulfonamide (8e) as a compound showing a remarkable activity across the panel, with IC50 values in the nanomolar-to-low micromolar range. Cell cycle distribution analysis revealed that 8e promoted a severe G2/M arrest, which was followed by cellular senescence as indicated by the detection of senescence-associated β-galactosidase (SA-β-gal) in 8e-treated cells. Prolonged 8e treatment also led to the onset of apoptosis, in correlation with the detection of increased Caspase 3/7 activities. Despite increasing γ-H2A.X levels, a well-established readout for DNA double-strand breaks, in vitro DNA binding studies with 8e did not support interaction with DNA. In agreement with this, 8e failed to activate the cellular DNA damage checkpoint. Importantly, tubulin staining showed that 8e promoted a severe disorganization of microtubules and mitotic spindle formation was not detected in 8e-treated cells. Accordingly, 8e inhibited tubulin polymerization in vitro in a dose-dependent manner and was also able to robustly inhibit cancer cell motility. Docking analysis revealed a compatible interaction with the colchicine-binding site of tubulin. Remarkably, these cellular effects were reversible since disruption of treatment resulted in the reorganization of microtubules, cell cycle re-entry and loss of senescent markers. Collectively, our data suggest that this compound may be a promising new anticancer agent capable of both reducing cancer cell growth and motility.

Effects of Anticancer Drugs on Chromosome Instability and New Clinical Implications for Tumor-Suppressing Therapies

Whole chromosomal instability (CIN), manifested as unequal chromosome distribution during cell division, is a distinguishing feature of most cancer types. CIN is generally considered to drive tumorigenesis, but a threshold level exists whereby further increases in CIN frequency in fact hinder tumor growth. While this attribute is appealing for therapeutic exploitation, drugs that increase CIN beyond this therapeutic threshold are currently limited. In our previous work, we developed a quantitative assay for measuring CIN based on the use of a nonessential human artificial chromosome (HAC) carrying a constitutively expressed EGFP transgene. Here, we used this assay to rank 62 different anticancer drugs with respect to their effects on chromosome transmission fidelity. Drugs with various mechanisms of action, such as antimicrotubule activity, histone deacetylase inhibition, mitotic checkpoint inhibition, and targeting of DNA replication and damage responses, were included in the analysis. Ranking of the drugs based on their ability to induce HAC loss revealed that paclitaxel, gemcitabine, dactylolide, LMP400, talazoparib, olaparib, peloruside A, GW843682, VX-680, and cisplatin were the top 10 drugs demonstrating HAC loss at a high frequency. Therefore, identification of currently used compounds that greatly increase chromosome mis-segregation rates should expedite the development of new therapeutic strategies to target and leverage the CIN phenotype in cancer cells.

Cross-Talk between AURKA and Plk1 in Mitotic Entry and Spindle Assembly

The Aurora kinase A (AURKA) is involved in different aspects of mitotic control, from mitotic entry to cytokinesis. Consistent with its pleiotropic roles, several AURKA interactors are able to modulate its activity, the best characterized being the microtubule-binding protein TPX2, the centrosomal protein Cep192, and Bora. Bora has been described as an essential cofactor of AURKA for phosphorylation-mediated activation of the mitotic kinase polo-like kinase 1 (Plk1) at the G2/M transition. A complex AURKA/Plk1 signaling axis is emerging, with multiple involved actors; recent data suggest that this control network is not restricted to mitotic entry only, but operates throughout mitosis. Here, we integrate available data from the literature to depict the complex interplay between AURKA and Plk1 in G2 and mitosis and how it contributes to their mitotic functions. We will particularly focus on how the activity of specifically localized AURKA/Plk1 pools is modulated in time and space by their reciprocal regulation to ensure the timely and coordinated unfolding of downstream mitotic events.

Sgo1 is a potential therapeutic target for hepatocellular carcinoma

Shugoshin-like protein 1 (Sgo1) is an essential protein in mitosis; it protects sister chromatid cohesion and thereby ensures the fidelity of chromosome separation. We found that the expression of Sgo1 mRNA was relatively low in normal tissues, but was upregulated in 82% of hepatocellular carcinoma (HCC), and correlated with elevated alpha-fetoprotein and early disease onset of HCC. The depletion of Sgo1 reduced cell viability of hepatoma cell lines including HuH7, HepG2, Hep3B, and HepaRG. Using time-lapse microscopy, we showed that hepatoma cells were delayed and ultimately die in mitosis in the absence of Sgo1. In contrast, cell viability and mitotic progression of immortalized cells were not significantly affected. Notably, mitotic cell death induced upon Sgo1 depletion was suppressed upon inhibitions of cyclin-dependent kinase-1 and Aurora kinase-B, or the depletion of mitotic arrest deficient-2. Thus, mitotic cell death induced upon Sgo1 depletion in hepatoma cells is mediated by persistent activation of the spindle assembly checkpoint. Together, these results highlight the essential role of Sgo1 in the maintenance of a proper mitotic progression in hepatoma cells and suggest that Sgo1 is a promising oncotarget for HCC.

Overexpression of KIF23 predicts clinical outcome in primary lung cancer patients

OBJECTIVE

High-level expression of kinesin family member 23 (KIF23), a member of microtubule-dependent molecular motors that transport organelles within cells and move chromosomes during cell division, has been observed in a variety of human malignancies. The aims of the present study were to observe the expression of KIF23 in lung cancer, examine the role of KIF23 in lung cancer cell growth and/or survival by small interfering RNA experiments, and explore its clinicopathologic significance and evaluate KIF23 expression as a prognostic marker.

MATERIALS AND METHODS

Quantitative reverse transcription-polymerase chain reaction analysis was performed to detect the expression of KIF23 mRNA using metastatic lymph nodes from patients with advanced lung cancer obtained by endobronchial ultrasonography-guided transbronchial needle aspiration (EBUS-TBNA) and primary lung tumors through surgical sample. The role of KIF23 in cancer cell growth was examined by small interfering RNA experiments. A total of 339 lung cancers were analyzed immunohistochemically on tissue microarrays to examine the expression of KIF23 protein and its clinicopathologic significance.

RESULTS

KIF23 transcript was found to be overexpressed in the great majority of metastatic lymph nodes from advanced lung cancers and primary lung tumors. Inhibiting KIF23 expression effectively suppressed lung cancer cell growth. High-level KIF23 expression was observed in 67.8% of the 339 cases. Lung adenocarcinoma patients with tumors displaying a high-level of KIF23 expression was also identified as an independent prognostic factor by multivariate analysis (P=0.0064).

CONCLUSION

KIF23 not only provides additional prognostic information for surgical treatment of lung cancer, but may also be a novel therapeutic target for these patients.

DNA methylation of DKK3 modulates docetaxel chemoresistance in human nonsmall cell lung cancer cell

Dickkopf-related protein 3 (DKK3) gene, as a tumor suppressor gene, has been discovered in various cancers, but its relationship with tumor chemoresistance is still unclear. In this study, this laboratory detected that DNA methylation contributes to the downregulation of DKK3 in docetaxel resistance of human lung cancer cells and its possible biochemical mechanism. DKK3 has been proved to be downregulated by hypermethylation in docetaxel-resistant lung cancer cells. Upregulation of DKK3 can reverse the chemoresistance of docetaxel-resistant cell lines in vitro by growth inhibition and enhancement of apoptosis. Conversely, downregulation of DKK3 could induce parental human lung cancer cells insensitivity to docetaxel by promoting proliferative capacity and inhibiting apoptosis of cancer cells. In addition, the authors observed that overexpression of DKK3 might decrease the expression of P-glycoprotein. All results suggested that epigenetic downregulation of DKK3 leads to docetaxel resistance in human nonsmall cell lung cancer (NSCLC) cells by increased expression of P-glycoprotein. DKK3 may reveal a novel molecular target for docetaxel resistance for NSCLC patients in the future.

Personalised and Precision Medicine in Cancer Clinical Trials: Panacea for Progress or Pandora's Box?

Cancer clinical trials have been one of the key foundations for significant advances in oncology. However, there is a clear recognition within the academic, care delivery and pharmaceutical/biotech communities that our current model of clinical trial discovery and development is no longer fit for purpose. Delivering transformative cancer care should increasingly be our mantra, rather than maintaining the status quo of, at best, the often miniscule incremental benefits that are observed with many current clinical trials. As we enter the era of precision medicine for personalised cancer care (precision and personalised medicine), it is important that we capture and utilise our greater understanding of the biology of disease to drive innovative approaches in clinical trial design and implementation that can lead to a step change in cancer care delivery. A number of advances have been practice changing (e.g. imatinib mesylate in chronic myeloid leukaemia, Herceptin in erb-B2-positive breast cancer), and increasingly we are seeing the promise of a number of newer approaches, particularly in diseases like lung cancer and melanoma. Targeting immune checkpoints has recently yielded some highly promising results. New algorithms that maximise the effectiveness of clinical trials, through for example a multi-stage, multi-arm type design are increasingly gaining traction. However, our enthusiasm for the undoubted advances that have been achieved are being tempered by a realisation that these new approaches may have significant cost implications. This article will address these competing issues, mainly from a European perspective, highlight the problems and challenges to healthcare systems and suggest potential solutions that will ensure that the cost/value rubicon is addressed in a way that allows stakeholders to work together to deliver optimal cost-effective cancer care, the benefits of which can be transferred directly to our patients.