Making the Auroras glow: regulation of Aurora A and B kinase function by interacting proteins

The role of Aurora kinase A in hepatocellular carcinoma: Unveiling the intriguing functions of a key but still underexplored factor in liver cancer

Aurora Kinase A (AURKA) plays a central role as a serine/threonine kinase in regulating cell cycle progression and mitotic functions. Over the years, extensive research has revealed the multifaceted roles of AURKA in cancer development and progression. AURKA's dysregulation is frequently observed in various human cancers, including hepatocellular carcinoma (HCC). Its overexpression in HCC has been associated with aggressive phenotypes and poor clinical outcomes. This review comprehensively explores the molecular mechanisms underlying AURKA expression in HCC and its functional implications in cell migration, invasion, epithelial-to-mesenchymal transition, metastasis, stemness, and drug resistance. This work focuses on the clinical significance of AURKA as a diagnostic and prognostic biomarker for HCC. High levels of AURKA expression have been correlated with shorter overall and disease-free survival in various cohorts, highlighting its potential utility as a sensitive prognostic indicator. Recent insights into AURKA's role in modulating the tumour microenvironment, particularly immune cell recruitment, may provide valuable information for personalized treatment strategies. AURKA's critical involvement in modulating cellular pathways and its overexpression in cancer makes it an attractive target for anticancer therapies. This review discusses the evidence about novel and selective AURKA inhibitors for more effective treatments for HCC.

Discovery of N-benzylbenzamide-based allosteric inhibitors of Aurora kinase A

Aurora kinases (AurkA/B/C) regulate the assembly of bipolar mitotic spindles and the fidelity of chromosome segregation during mitosis, and are attractive therapeutic targets for cancers. Numerous ATP-competitive AurkA inhibitors have been developed as potential anti-cancer agents. Recently, a few allosteric inhibitors have been reported that bind to the allosteric Y-pocket within AurkA kinase domain and disrupt the interaction between AurkA and its activator TPX2. Herein we report a novel allosteric AurkA inhibitor (6h) of N-benzylbenzamide backbone. Compound 6h suppressed the both catalytic activity and non-catalytic functions of AurkA. The inhibitory activity of 6h against AurkA (IC50 = 6.50 μM) was comparable to that of the most potent allosteric AurkA inhibitor AurkinA. Docking analysis against the Y-pocket revealed important pharmacophores and interactions that were coherent with structure-activity relationship. In addition, 6h suppressed DNA replication in G1-S phase, which is a feature of allosteric inhibition of AurA. Our current study may provide a useful insight in designing potent allosteric AurkA inhibitors.

Revisiting Aurora Kinase B: A promising therapeutic target for cancer therapy

Cancer continues to be a major health concern globally, although the advent of targeted therapy has revolutionized treatment options. Aurora Kinase B is a serine-threonine kinase that has been explored as an oncology therapeutic target for more than two decades. Aurora Kinase B inhibitors show promising biological results in in-vitro and in-vivo experiments. However, there are no inhibitors approved yet for clinical use, primarily because of the side effects associated with Aurora B inhibitors. Several studies demonstrate that Aurora B inhibitors show excellent synergy with various chemotherapeutic agents, radiation therapy, and targeted therapies. This makes it an excellent choice as an adjuvant therapy to first-line therapies, which greatly improves the therapeutic window and side effect profile. Recent studies indicate the role of Aurora B in some deadly cancers with limited therapeutic options, like triple-negative breast cancer and glioblastoma. Herein, we review the latest developments in Aurora Kinase B targeted research, with emphasis on its potential as an adjuvant therapy and its role in some of the most difficult-to-treat cancers.

NAK-associated protein 1/NAP1 activates TBK1 to ensure accurate mitosis and cytokinesis

Subcellular location and activation of Tank Binding Kinase 1 (TBK1) govern precise progression through mitosis. Either loss of activated TBK1 or its sequestration from the centrosomes causes errors in mitosis and growth defects. Yet, what regulates its recruitment and activation on the centrosomes is unknown. We identified that NAK-associated protein 1 (NAP1) is essential for mitosis, binding to and activating TBK1, which both localize to centrosomes. Loss of NAP1 causes several mitotic and cytokinetic defects due to inactivation of TBK1. Our quantitative phosphoproteomics identified numerous TBK1 substrates that are not only confined to the centrosomes but are also associated with microtubules. Substrate motifs analysis indicates that TBK1 acts upstream of other essential cell cycle kinases like Aurora and PAK kinases. We also identified NAP1 as a TBK1 substrate phosphorylating NAP1 at S318 to promote its degradation by the ubiquitin proteasomal system. These data uncover an important distinct function for the NAP1-TBK1 complex during cell division.

Functional specialization of Aurora kinase homologs during oogenic meiosis in the tunicate Oikopleura dioica

A single Aurora kinase found in non-vertebrate deuterostomes is assumed to represent the ancestor of vertebrate Auroras A/B/C. However, the tunicate Oikopleura dioica, a member of the sister group to vertebrates, possesses two Aurora kinases (Aurora1 and Aurora2) that are expressed in proliferative cells and reproductive organs. Previously, we have shown that Aurora kinases relocate from organizing centers to meiotic nuclei and were enriched on centromeric regions as meiosis proceeds to metaphase I. Here, we assessed their respective functions in oogenic meiosis using dsRNA interferences. We found that Aurora1 (Aur1) was involved in meiotic spindle organization and chromosome congression, probably through the regulation of microtubule dynamics, whereas Aurora2 (Aur2) was crucial for chromosome condensation and meiotic spindle assembly. In vitro kinase assays showed that Aur1 and Aur2 had comparable levels of kinase activities. Using yeast two-hybrid library screening, we identified a few novel interaction proteins for Aur1, including c-Jun-amino-terminal kinase-interacting protein 4, cohesin loader Scc2, and mitochondrial carrier homolog 2, suggesting that Aur1 may have an altered interaction network and participate in the regulation of microtubule motors and cohesin complexes in O. dioica.

Bioluminescent immunoassay for serine/threonine protein kinase activity using an aequorin-labeled monoclonal antibody and a synthetic peptide as a substrate

A bioluminescent immunoassay system was developed to determine serine/threonine protein kinase activity using an aequorin-labeled monoclonal antibody and a synthetic peptide as the substrate. A monoclonal antibody against the synthetic phosphorylated serine peptide (K9P peptide) of histone H3 (19 amino acid residues), referred to as the H3S10P antibody, was chemically conjugated to maleimide-activated aequorin to prepare aequorin-labeled H3S10P (AQ-S-H3S10P). For the serine/threonine kinase assay, a non-phosphorylated serine peptide (K9C peptide) coated on a microplate was incubated with serine/threonine protein kinase in the presence of ATP and Mg2+. The resulting phosphorylated K9C peptides (K9P peptide) were identified using AQ-S-H3S10P. Thus, after the removal of unbound AQ-S-H3S10P though washing, the serine/threonine kinase activity was determined by the luminescence activity of aequorin from AQ-S-H3S10P bound to the K9P peptide. This assay system, in combination with the K9C peptide and AQ-S-H3S10P, could be used to screen inhibitors of various serine/threonine protein kinases in general.

Regulation and function of R-loops at repetitive elements

R-loops are atypical, three-stranded nucleic acid structures that contain a stretch of RNA:DNA hybrids and an unpaired, single stranded DNA loop. R-loops are physiological relevant and can act as regulators of gene expression, chromatin structure, DNA damage repair and DNA replication. However, unscheduled and persistent R-loops are mutagenic and can mediate replication-transcription conflicts, leading to DNA damage and genome instability if left unchecked. Detailed transcriptome analysis unveiled that 85% of the human genome, including repetitive regions, hold transcriptional activity. This anticipates that R-loops management plays a central role for the regulation and integrity of genomes. This function is expected to have a particular relevance for repetitive sequences that make up to 75% of the human genome. Here, we review the impact of R-loops on the function and stability of repetitive regions such as centromeres, telomeres, rDNA arrays, transposable elements and triplet repeat expansions and discuss their relevance for associated pathological conditions.

Plasmodium ARK2 and EB1 drive unconventional spindle dynamics, during chromosome segregation in sexual transmission stages

The Aurora family of kinases orchestrates chromosome segregation and cytokinesis during cell division, with precise spatiotemporal regulation of its catalytic activities by distinct protein scaffolds. Plasmodium spp., the causative agents of malaria, are unicellular eukaryotes with three unique and highly divergent aurora-related kinases (ARK1-3) that are essential for asexual cellular proliferation but lack most canonical scaffolds/activators. Here we investigate the role of ARK2 during sexual proliferation of the rodent malaria Plasmodium berghei, using a combination of super-resolution microscopy, mass spectrometry, and live-cell fluorescence imaging. We find that ARK2 is primarily located at spindle microtubules in the vicinity of kinetochores during both mitosis and meiosis. Interactomic and co-localisation studies reveal several putative ARK2-associated interactors including the microtubule-interacting protein EB1, together with MISFIT and Myosin-K, but no conserved eukaryotic scaffold proteins. Gene function studies indicate that ARK2 and EB1 are complementary in driving endomitotic division and thereby parasite transmission through the mosquito. This discovery underlines the flexibility of molecular networks to rewire and drive unconventional mechanisms of chromosome segregation in the malaria parasite.

A mitotic NADPH upsurge promotes chromosome segregation and tumour progression in aneuploid cancer cells

Redox metabolites have been observed to fluctuate through the cell cycle in cancer cells, but the functional impacts of such metabolic oscillations remain unknown. Here, we uncover a mitosis-specific nicotinamide adenine dinucleotide phosphate (NADPH) upsurge that is essential for tumour progression. Specifically, NADPH is produced by glucose 6-phosphate dehydrogenase (G6PD) upon mitotic entry, which neutralizes elevated reactive oxygen species (ROS) and prevents ROS-mediated inactivation of mitotic kinases and chromosome missegregation. Mitotic activation of G6PD depends on the phosphorylation of its co-chaperone protein BAG3 at threonine 285, which results in dissociation of inhibitory BAG3. Blocking BAG3T285 phosphorylation induces tumour suppression. A mitotic NADPH upsurge is present in aneuploid cancer cells with high levels of ROS, while nearly unobservable in near-diploid cancer cells. High BAG3T285 phosphorylation is associated with worse prognosis in a cohort of patients with microsatellite-stable colorectal cancer. Our study reveals that aneuploid cancer cells with high levels of ROS depend on a G6PD-mediated NADPH upsurge in mitosis to protect them from ROS-induced chromosome missegregation.

Identification of PP2A-B55 targets uncovers regulation of emerin during nuclear envelope reassembly in Drosophila

Mitotic exit requires the dephosphorylation of many proteins whose phosphorylation was needed for mitosis. Protein phosphatase 2A with its B55 regulatory subunit (PP2A-B55) promotes this transition. However, the events and substrates that it regulates are incompletely understood. We used proteomic approaches in Drosophila to identify proteins that interact with and are dephosphorylated by PP2A-B55. Among several candidates, we identified emerin (otefin in Drosophila). Emerin resides in the inner nuclear membrane and interacts with the DNA-binding protein barrier-to-autointegration factor (BAF) via a LEM domain. We found that the phosphorylation of emerin at Ser50 and Ser54 near its LEM domain negatively regulates its association with BAF, lamin and additional emerin in mitosis. We show that dephosphorylation of emerin at these sites by PP2A-B55 determines the timing of nuclear envelope reformation. Genetic experiments indicate that this regulation is required during embryonic development. Phosphoregulation of the emerin-BAF complex formation by PP2A-B55 appears as a key event of mitotic exit that is likely conserved across species.

V-Src delocalizes Aurora B by suppressing Aurora B kinase activity during monopolar cytokinesis

c-Src tyrosine kinase plays roles in a wide range of signaling events and its increased activity is frequently observed in a variety of epithelial and non-epithelial cancers. v-Src, an oncogene first identified in the Rous sarcoma virus, is an oncogenic version of c-Src and has constitutively active tyrosine kinase activity. We previously showed that v-Src induces Aurora B delocalization, resulting in cytokinesis failure and binucleated cell formation. In the present study, we explored the mechanism underlying v-Src-induced Aurora B delocalization. Treatment with the Eg5 inhibitor (+)-S-trityl-L-cysteine (STLC) arrested cells in a prometaphase-like state with a monopolar spindle; upon further inhibition of cyclin-dependent kinase (CDK1) by RO-3306, cells underwent monopolar cytokinesis with bleb-like protrusions. Aurora B was localized to the protruding furrow region or the polarized plasma membrane 30 min after RO-3306 addition, whereas inducible v-Src expression caused Aurora B delocalization in cells undergoing monopolar cytokinesis. Delocalization was similarly observed in monopolar cytokinesis induced by inhibiting Mps1, instead of CDK1, in the STLC-arrested mitotic cells. Importantly, western blotting analysis and in vitro kinase assay revealed that v-Src decreased the levels of Aurora B autophosphorylation and its kinase activity. Furthermore, like v-Src, treatment with the Aurora B inhibitor ZM447439 also caused Aurora B delocalization at concentrations that partially inhibited Aurora B autophosphorylation. Given that phosphorylation of Aurora B by v-Src was not observed, these results suggest that v-Src causes Aurora B delocalization by indirectly suppressing Aurora B kinase activity.

Aurora B Inhibitors as Cancer Therapeutics

The Aurora kinases (A, B, and C) are a family of three isoform serine/threonine kinases that regulate mitosis and meiosis. The Chromosomal Passenger Complex (CPC), which contains Aurora B as an enzymatic component, plays a critical role in cell division. Aurora B in the CPC ensures faithful chromosome segregation and promotes the correct biorientation of chromosomes on the mitotic spindle. Aurora B overexpression has been observed in several human cancers and has been associated with a poor prognosis for cancer patients. Targeting Aurora B with inhibitors is a promising therapeutic strategy for cancer treatment. In the past decade, Aurora B inhibitors have been extensively pursued in both academia and industry. This paper presents a comprehensive review of the preclinical and clinical candidates of Aurora B inhibitors as potential anticancer drugs. The recent advances in the field of Aurora B inhibitor development will be highlighted, and the binding interactions between Aurora B and inhibitors based on crystal structures will be presented and discussed to provide insights for the future design of more selective Aurora B inhibitors.

Aurora Kinase A Regulation by Cysteine Oxidative Modification

Aurora kinase A (AURKA), which is a member of serine/threonine kinase family, plays a critical role in regulating mitosis. AURKA has drawn much attention as its dysregulation is critically associated with various cancers, leading to the development of AURKA inhibitors, a new class of anticancer drugs. As the spatiotemporal activity of AURKA critically depends on diverse intra- and inter-molecular factors, including its interaction with various protein cofactors and post-translational modifications, each of these pathways should be exploited for the development of a novel class of AURKA inhibitors other than ATP-competitive inhibitors. Several lines of evidence have recently shown that redox-active molecules can modify the cysteine residues located on the kinase domain of AURKA, thereby regulating its activity. In this review, we present the current understanding of how oxidative modifications of cysteine residues of AURKA, induced by redox-active molecules, structurally and functionally regulate AURKA and discuss their implications in the discovery of novel AURKA inhibitors.

Plasmodium ARK2-EB1 axis drives the unconventional spindle dynamics, scaffold formation and chromosome segregation of sexual transmission stages

Mechanisms of cell division are remarkably diverse, suggesting the underlying molecular networks among eukaryotes differ extensively. The Aurora family of kinases orchestrates the process of chromosome segregation and cytokinesis during cell division through precise spatiotemporal regulation of their catalytic activities by distinct scaffolds. Plasmodium spp., the causative agents of malaria, are unicellular eukaryotes that have three divergent aurora-related kinases (ARKs) and lack most canonical scaffolds/activators. The parasite uses unconventional modes of chromosome segregation during endomitosis and meiosis in sexual transmission stages within mosquito host. This includes a rapid threefold genome replication from 1N to 8N with successive cycles of closed mitosis, spindle formation and chromosome segregation within eight minutes (termed male gametogony). Kinome studies had previously suggested likely essential functions for all three Plasmodium ARKs during asexual mitotic cycles; however, little is known about their location, function, or their scaffolding molecules during unconventional sexual proliferative stages. Using a combination of super-resolution microscopy, mass spectrometry, omics and live-cell fluorescence imaging, we set out to investigate the contribution of the atypical Aurora paralog ARK2 to proliferative sexual stages using rodent malaria model Plasmodium berghei. We find that ARK2 primarily localises to the spindle apparatus associated with kinetochores during both mitosis and meiosis. Interactomics and co-localisation studies reveal a unique ARK2 scaffold at the spindle including the microtubule plus end-binding protein EB1 and lacking some other conserved molecules. Gene function studies indicate complementary functions of ARK2 and EB1 in driving endomitotic divisions and thereby parasite transmission. Our discovery of a novel Aurora spindle scaffold underlines the emerging flexibility of molecular networks to rewire and drive unconventional mechanisms of chromosome segregation in the malaria parasite Plasmodium.

Survivin Small Molecules Inhibitors: Recent Advances and Challenges

Survivin, as a member of the inhibitor of apoptosis proteins (IAPs) family, acts as a suppressor of apoptosis and plays a central role in cell division. Survivin has been considered as an important cancer drug target because it is highly expressed in many types of human cancers, while it is effectively absent from terminally differentiated normal tissues. Moreover, survivin is involved in tumor cell resistance to chemotherapy and radiation. Preclinically, downregulation of survivin expression or function reduced tumor growth induced apoptosis and sensitized tumor cells to radiation and chemotherapy in different human tumor models. This review highlights the role of survivin in promoting cellular proliferation and inhibiting apoptosis and summarizes the recent advances in and challenges of developing small-molecule survivin inhibitors.

Plasmodium ARK2-EB1 axis drives the unconventional spindle dynamics, scaffold formation and chromosome segregation of sexual transmission stages

Mechanisms of cell division are remarkably diverse, suggesting the underlying molecular networks among eukaryotes differ extensively. The Aurora family of kinases orchestrates the process of chromosome segregation and cytokinesis during cell division through precise spatiotemporal regulation of their catalytic activities by distinct scaffolds. Plasmodium spp., the causative agents of malaria, are unicellular eukaryotes that have three divergent aurora-related kinases (ARKs) and lack most canonical scaffolds/activators. The parasite uses unconventional modes of chromosome segregation during endomitosis and meiosis in sexual transmission stages within mosquito host. This includes a rapid threefold genome replication from 1N to 8N with successive cycles of closed mitosis, spindle formation and chromosome segregation within eight minutes (termed male gametogony). Kinome studies had previously suggested likely essential functions for all three Plasmodium ARKs during asexual mitotic cycles; however, little is known about their location, function, or their scaffolding molecules during unconventional sexual proliferative stages. Using a combination of super-resolution microscopy, mass spectrometry, and live-cell fluorescence imaging, we set out to investigate the role of the atypical Aurora paralog ARK2 to proliferative sexual stages using rodent malaria model Plasmodium berghei . We find that ARK2 primarily localises to the spindle apparatus in the vicinity of kinetochores during both mitosis and meiosis. Interactomics and co-localisation studies reveal a unique ARK2 scaffold at the spindle including the microtubule plus end-binding protein EB1, lacking conserved Aurora scaffold proteins. Gene function studies indicate complementary functions of ARK2 and EB1 in driving endomitotic divisions and thereby parasite transmission. Our discovery of a novel Aurora kinase spindle scaffold underlines the emerging flexibility of molecular networks to rewire and drive unconventional mechanisms of chromosome segregation in the malaria parasite Plasmodium .

The deubiquitinating enzyme complex BRISC regulates Aurora B activation via lysine-63-linked ubiquitination in mitosis

Faithful chromosome segregation requires bi-oriented kinetochore-microtubule attachment on the metaphase spindle. Aurora B kinase, the catalytic core of the chromosome passage complex (CPC), plays a crucial role in this process. Aurora B activation has widely been investigated in the context of protein phosphorylation. Here, we report that Aurora B is ubiquitinated in mitosis through lysine-63 ubiquitin chains (K63-Ub), which is required for its activation. Mutation of Aurora B at its primary K63 ubiquitin site inhibits its activation, reduces its kinase activity, and disrupts the association of Aurora B with other components of CPC, leading to severe mitotic defects and cell apoptosis. Moreover, we identify that BRCC36 isopeptidase complex (BRISC) is the K63-specific deubiquitinating enzyme for Aurora B. BRISC deficiency augments the accumulation of Aurora B K63-Ubs, leading to Aurora B hyperactivation and erroneous chromosome-microtubule attachments. These findings define the role of K63-linked ubiquitination in regulating Aurora B activation and provide a potential site for Aurora B-targeting drug design.

The Anaphase-Promoting Complex/Cyclosome Is a Cellular Ageing Regulator

The anaphase-promoting complex/cyclosome (APC/C) is a complicated cellular component that plays significant roles in regulating the cell cycle process of eukaryotic organisms. The spatiotemporal regulation mechanisms of APC/C in distinct cell cycle transitions are no longer mysterious, and the components of this protein complex are gradually identified and characterized. Given the close relationship between the cell cycle and lifespan, it is urgent to understand the roles of APC/C in lifespan regulation, but this field still seems to have not been systematically summarized. Furthermore, although several reviews have reported the roles of APC/C in cancer, there are still gaps in the summary of its roles in other age-related diseases. In this review, we propose that the APC/C is a novel cellular ageing regulator based on its indispensable role in the regulation of lifespan and its involvement in age-associated diseases. This work provides an extensive review of aspects related to the underlying mechanisms of APC/C in lifespan regulation and how it participates in age-associated diseases. More comprehensive recognition and understanding of the relationship between APC/C and ageing and age-related diseases will increase the development of targeted strategies for human health.

The Aurora Kinase Inhibitor TAK901 Inhibits Glioblastoma Growth by Blocking SREBP1-Mediated Lipid Metabolism

Glioblastoma (GBM) is the most common and lethal malignant primary brain tumor. The standard treatment for GBM including surgical resection followed by radiation therapy and adjuvant chemotherapy with temozolomide remains unsatisfactory. In this study, we investigated the effects of the Aurora kinase inhibitor, TAK901, in GBM both in vitro and in vivo, and explored its key downstream targets. The effects of TAK901 were investigated using cell viability, cell apoptosis, live/dead, cell cycle, Transwell, 3D cell invasion, neuro-sphere, and self-renewal assays. Mechanistic studies were conducted using RNA-seq, lipid measurements, reverse transcription-quantitative polymerase chain reaction (RT-qPCR), and Western blotting. The in vivo efficacy of TAK901 was validated using orthotopic xenograft GBM mouse models. In both GBM cells and GSCs, TAK901 remarkably reduced cell viability, self-renewal, migration and invasion and induced apoptosis and cell cycle arrest. Treatment with TAK901 considerably inhibited GBM growth in vivo. RNA-seq and RT-qPCR analyses showed that TAK901 downregulated the expression and activation of SREBP1. Moreover, SREBP1 overexpression alleviated the TAK901-mediated suppression of cell viability and apoptosis in GBM cells. Our results provide evidence that TAK901 inhibits GBM growth by suppressing SREBP1-mediated lipid metabolism.

Unweaving the mitotic spindle: A focus on Aurora kinase inhibitors in lung cancer

Lung cancer is one of the most aggressive malignancies, classified into two major histological subtypes: non-small cell lung cancer (NSCLC), that accounts for about 85% of new diagnosis, and small cell lung cancer (SCLC), the other 15%. In the case of NSCLC, comprehensive genome sequencing has allowed the identification of an increasing number of actionable targets, which have become the cornerstone of treatment in the advanced setting. On the other hand, the concept of oncogene-addiction is lacking in SCLC, and the only innovation of the last 30 years has been the introduction of immune checkpoint inhibitors in extensive stage disease. Dysregulation of cell cycle is a fundamental step in carcinogenesis, and Aurora kinases (AURKs) are a family of serine/threonine kinases that play a crucial role in the correct advance through the steps of the cycle. Hyperexpression of Aurora kinases is a common protumorigenic pathway in many cancer types, including NSCLC and SCLC; in addition, different mechanisms of resistance to anticancer drugs rely on AURK expression. Hence, small molecule inhibitors of AURKs have been developed in recent years and tested in several malignancies, with different results. The aim of this review is to analyze the current evidences of AURK inhibition in lung cancer, starting from preclinical rationale to finish with clinical trials available up to now.

Dephosphorylation in nuclear reassembly after mitosis

In most animal cell types, the interphase nucleus is largely disassembled during mitotic entry. The nuclear envelope breaks down and chromosomes are compacted into separated masses. Chromatin organization is also mostly lost and kinetochores assemble on centromeres. Mitotic protein kinases play several roles in inducing these transformations by phosphorylating multiple effector proteins. In many of these events, the mechanistic consequences of phosphorylation have been characterized. In comparison, how the nucleus reassembles at the end of mitosis is less well understood in mechanistic terms. In recent years, much progress has been made in deciphering how dephosphorylation of several effector proteins promotes nuclear envelope reassembly, chromosome decondensation, kinetochore disassembly and interphase chromatin organization. The precise roles of protein phosphatases in this process, in particular of the PP1 and PP2A groups, are emerging. Moreover, how these enzymes are temporally and spatially regulated to ensure that nuclear reassembly progresses in a coordinated manner has been partly uncovered. This review provides a global view of nuclear reassembly with a focus on the roles of dephosphorylation events. It also identifies important open questions and proposes hypotheses.

Comprehensive review of α-carboline alkaloids: Natural products, updated synthesis, and biological activities

α-carboline (9H-pyrido[2,3-b]indole), contains a pyridine ring fused with an indole backbone, is a promising scaffold for medicinal chemistry. In recent decades, accumulating evidence shows that α-carboline natural products and their derivatives possess diverse bioactivities. However, hitherto, there is no comprehensive review to systematically summarize this important class of alkaloids. In this perspective, this paper represents the first review to provide a comprehensive description of α-carbolines including natural products, updated literature of synthesis, and their diverse biological activities. Their biological activities including antitumor, anti-microbial, anti-Alzheimer’s disease, anti-atherosclerosis, and antioxidant activities were hilighted. And the targets and the main structure activity relationships (SARs) will be presented. Finally, challenges and future directions of this class of compounds will be discussed. This review will be helpful in understanding and encouraging further exploration for this group of alkaloids.

Polar Chromosomes—Challenges of a Risky Path

The process of chromosome congression and alignment is at the core of mitotic fidelity. In this review, we discuss distinct spatial routes that the chromosomes take to align during prometaphase, which are characterized by distinct biomolecular requirements. Peripheral polar chromosomes are an intriguing case as their alignment depends on the activity of kinetochore motors, polar ejection forces, and a transition from lateral to end-on attachments to microtubules, all of which can result in the delayed alignment of these chromosomes. Due to their undesirable position close to and often behind the spindle pole, these chromosomes may be particularly prone to the formation of erroneous kinetochore-microtubule interactions, such as merotelic attachments. To prevent such errors, the cell employs intricate mechanisms to preposition the spindle poles with respect to chromosomes, ensure the formation of end-on attachments in restricted spindle regions, repair faulty attachments by error correction mechanisms, and delay segregation by the spindle assembly checkpoint. Despite this protective machinery, there are several ways in which polar chromosomes can fail in alignment, mis-segregate, and lead to aneuploidy. In agreement with this, polar chromosomes are present in certain tumors and may even be involved in the process of tumorigenesis.

Particulate matter (PM10) destabilizes mitotic spindle through downregulation of SETD2 in A549 lung cancer cells

Air pollution represents an environmental problem, impacting negatively in human health. Particulate matter of 10 μm or less in diameter (PM₁₀) is related to pulmonary diseases, including lung cancer. Mitotic spindle is made up by chromosome-microtubule (MT) interactions, where SETD2 plays an important role in MT stability. SETD2 binds and activates α-TUBULIN sub-unit and promotes MT polymerization. Alongside this mechanism, the spindle assembly checkpoint (SAC) senses the adequate mitotic progression through proteins such as BUBR1, AURORA B and SURVIVIN. Alterations in MT dynamics as well as in SAC cause aneuploidy and chromosomal instability, a common phenotype in cancer cells. In this study, we evaluated the effect of PM₁₀ in the expression and protein levels of SETD2, as well as the effect in the expression and protein levels of SAC and mitotic components involved in chromosomal segregation/mitosis, using the A549 lung cancer cell line. A549 cell cultures were exposed to PM₁₀ (10 μg/cm²) for 24 h to evaluate the expression and protein levels of SETD2 (SETD2), TUBA1A (α-TUBULIN), CCNB1 (CYCLIN B1), BUB1B (BUBR1), AURKB (AURORA B) and BIRC5 (SURVIVIN). We observed that PM₁₀ decreases the expression and protein levels of SETD2, α-TUBULIN and BUBR1 and increases the levels of AURORA B and SURVIVIN in A549 cells, compared with non-treated cells. PM₁₀ also caused a decrease in mitotic index and in the percentage of cells in G2/M when compared with control group. Co-localization of SETD2/α -TUB was lower in PM₁₀-treated cells in comparison with non-treated cells. Finally, micronuclei (MN) frequency was higher in PM₁₀-treated cells in contrast with non-treated cells, being whole chromosomes more common in PM₁₀-treated MN than in non-treated MN. Our results suggest that PM₁₀ causes missegregation and aneuploidy through downregulation of SETD2 and SAC components, inducing aneuploidy and predisposing to the generation of chromosomal instability in transformed cells.

Integrative network analysis of early-stage lung adenocarcinoma identifies aurora kinase inhibition as interceptor of invasion and progression

Here we focus on the molecular characterization of clinically significant histological subtypes of early-stage lung adenocarcinoma (esLUAD), which is the most common histological subtype of lung cancer. Within lung adenocarcinoma, histology is heterogeneous and associated with tumor invasion and diverse clinical outcomes. We present a gene signature distinguishing invasive and non-invasive tumors among esLUAD. Using the gene signatures, we estimate an Invasiveness Score that is strongly associated with survival of esLUAD patients in multiple independent cohorts and with the invasiveness phenotype in lung cancer cell lines. Regulatory network analysis identifies aurora kinase as one of master regulators of the gene signature and the perturbation of aurora kinases in vitro and in a murine model of invasive lung adenocarcinoma reduces tumor invasion. Our study reveals aurora kinases as a therapeutic target for treatment of early-stage invasive lung adenocarcinoma.

Pyrogallol-Phloroglucinol-6, 6-Bieckol Restored Primary Cilia Length, Which Was Decreased by High-Fat Diet in Visceral Adipose Tissue, and Decreased Adipogenesis

Length of primary cilia, which involves cell cycle reentry and disassembly of cilia, promotes cell mitosis. It is known that the cilia length in adipose tissue of the high-fat diet (HFD) animals was shortened and accompanied by increased adipogenesis. Male C57BL/6N mice were randomly divided into groups. The mice group was given the normal fat diet (NFD/saline), HFD mice group for 4 weeks, and then HFD was also treated for the next 4 weeks with saline (HFD/saline), Ecklonia cava extract (HFD/ECE), or pyrogallol-phloroglucinol-6, 6-bieckol, a segment of ECE (HFD/PPB). We evaluated the effect of ECE and PPB on modulating cilia length of visceral adipose tissue and decreasing adipogenesis by decreasing cell cycle reentry using an HFD-fed mouse model. ECE and PPB decreased physiological changes, which increased by HFD, but ECE and PPB decreased the upregulation of the IL-6/STAT3/AURKA signaling pathway, which is involved in cilia disassembly. In addition, ECE or PPB elongated the cilia and decreased cyclin A2 and Cdk2 expression, which promote cell cycle reentry, and decreased the adipogenesis genes. PPB and ECE restored cilia length and decreased adipogenesis through modulating the IL-6/STAT3/AURKA pathway and decreasing cell cycle reentry in the visceral adipose tissue of HFD/saline mice group.

Characterization of subcellular localization of eukaryotic clamp loader/unloader and its regulatory mechanism

Proliferating cell nuclear antigen (PCNA) plays a critical role as a processivity clamp for eukaryotic DNA polymerases and a binding platform for many DNA replication and repair proteins. The enzymatic activities of PCNA loading and unloading have been studied extensively in vitro. However, the subcellular locations of PCNA loaders, replication complex C (RFC) and CTF18-RFC-like-complex (RLC), and PCNA unloader ATAD5-RLC remain elusive, and the role of their subunits RFC2-5 is unknown. Here we used protein fractionation to determine the subcellular localization of RFC and RLCs and affinity purification to find molecular requirements for the newly defined location. All RFC/RLC proteins were detected in the nuclease-resistant pellet fraction. RFC1 and ATAD5 were not detected in the non-ionic detergent-soluble and nuclease-susceptible chromatin fractions, independent of cell cycle or exogenous DNA damage. We found that small RFC proteins contribute to maintaining protein levels of the RFC/RLCs. RFC1, ATAD5, and RFC4 co-immunoprecipitated with lamina-associated polypeptide 2 (LAP2) α which regulates intranuclear lamin A/C. LAP2α knockout consistently reduced detection of RFC/RLCs in the pellet fraction, while marginally affecting total protein levels. Our findings strongly suggest that PCNA-mediated DNA transaction occurs through regulatory machinery associated with nuclear structures, such as the nuclear matrix.

Targeting Aurora B kinase prevents and overcomes resistance to EGFR inhibitors in lung cancer by enhancing BIM- and PUMA-mediated apoptosis

The clinical success of EGFR inhibitors in EGFR-mutant lung cancer is limited by the eventual development of acquired resistance. We hypothesize that enhancing apoptosis through combination therapies can eradicate cancer cells and reduce the emergence of drug-tolerant persisters. Through high-throughput screening of a custom library of ∼1,000 compounds, we discover Aurora B kinase inhibitors as potent enhancers of osimertinib-induced apoptosis. Mechanistically, Aurora B inhibition stabilizes BIM through reduced Ser87 phosphorylation, and transactivates PUMA through FOXO1/3. Importantly, osimertinib resistance caused by epithelial-mesenchymal transition (EMT) activates the ATR-CHK1-Aurora B signaling cascade and thereby engenders hypersensitivity to respective kinase inhibitors by activating BIM-mediated mitotic catastrophe. Combined inhibition of EGFR and Aurora B not only efficiently eliminates cancer cells but also overcomes resistance beyond EMT.

AURKB, CHEK1 and NEK2 as the Potential Target Proteins of Scutellaria barbata on Hepatocellular Carcinoma: An Integrated Bioinformatics Analysis

Objective

We aim to explore the potential anti-HCC mechanism of Scutellaria barbata through integrated bioinformatics analysis.

Methods

We searched active ingredients and related targets of Scutellaria barbata via TCMSP database, PubChem and SwissTargetPrediction database. Then, we identified HCC disease targets from GEO dataset by WGCNA. Next, the intersected targets of disease targets and drug targets were input into STRING database to construct PPI networking in order to obtain potential therapeutic targets of Scutellaria barbata. Cytoscape software was used to carry out network topology analysis of potential targets. We used the R package for GO analysis and KEGG analysis. Finally, we used AutoDock vina and PyMOL software for molecular docking.

Results

Sixteen active components from Scutellaria barbata were lastly selected for further investigation. A total of 442 component targets were identified from 16 active ingredients of Scutellaria barbata after the removal of duplicate targets. GSE45436 was selected for construction of WGCNA and screening of differentially expressed genes. A total of 354 genes were up-regulated in HCC samples and 100 were down-regulated in HCC patients. Twenty-one common genes were obtained by intersection and 10 critical targets were filtered for further investigation. The enrichment analysis showed that cell cycle, DNA replication, p53 signaling pathway were mainly involved. The molecular docking results showed that 4 potential combinations were with the best binding energy and molecular interactions.

Conclusion

AURKB, CHEK1 and NEK2 could be the potential target proteins of Scutellaria barbata in treating HCC. Cell cycle, DNA replication, p53 signaling pathway consist of the fundamental regulation cores in this mechanism.

SUMO proteases SENP3 and SENP5 spatiotemporally regulate the kinase activity of Aurora A

Precise chromosome segregation is mediated by a well-assembled mitotic spindle, which requires balance of the kinase activity of Aurora A (AurA, also known as AURKA). However, how this kinase activity is regulated remains largely unclear. Here, using in vivo and in vitro assays, we report that conjugation of SUMO2 with AurA at K258 in early mitosis promotes the kinase activity of AurA and facilitates the binding with its activator Bora. Knockdown of the SUMO proteases SENP3 and SENP5 disrupts the deSUMOylation of AurA, leading to increased kinase activity and abnormalities in spindle assembly and chromosome segregation, which could be rescued by suppressing the kinase activity of AurA. Collectively, these results demonstrate that SENP3 and SENP5 deSUMOylate AurA to render spatiotemporal control on its kinase activity in mitosis. This article has an associated First Person interview with the first author of the paper.

AGO2 localizes to cytokinetic protrusions in a p38-dependent manner and is needed for accurate cell division

Argonaute 2 (AGO2) is an indispensable component of the RNA-induced silencing complex, operating at the translational or posttranscriptional level. It is compartmentalized into structures such as GW- and P-bodies, stress granules and adherens junctions as well as the midbody. Here we show using immunofluorescence, image and bioinformatic analysis and cytogenetics that AGO2 also resides in membrane protrusions such as open- and close-ended tubes. The latter are cytokinetic bridges where AGO2 colocalizes at the midbody arms with cytoskeletal components such as α-Τubulin and Aurora B, and various kinases. AGO2, phosphorylated on serine 387, is located together with Dicer at the midbody ring in a manner dependent on p38 MAPK activity. We further show that AGO2 is stress sensitive and important to ensure the proper chromosome segregation and cytokinetic fidelity. We suggest that AGO2 is part of a regulatory mechanism triggered by cytokinetic stress to generate the appropriate micro-environment for local transcript homeostasis.

Pantazopoulou et al. find that AGO2 resides in open-ended tunneling nanotubes and close-ended cytokinetic bridges. At the latter location, AGO2 colocalizes with cell division components and the authors show that AGO2 depletion impairs cell division fidelity.

Aurora B kinase: a potential drug target for cancer therapy

BACKGROUND

Ensuring genetic integrity is essential during the cell cycle to avoid aneuploidy, one of the underlying causes of malignancies. Aurora kinases are serine/threonine kinase that play a vital role in maintaining the genomic integrity of the cells. There are three forms of aurora kinases in the mammalian cells, which are highly conserved and act together with several other proteins to control chromosome alignment and its equal distribution to daughter cells in mitosis and meiosis.

METHODS

We provide here a detailed analysis of Aurora B kinase (ABK) in terms of its expression, structure, function, disease association and potential therapeutic implications.

RESULTS

ABK plays an instrumental in mitotic entry, chromosome condensation, spindle assembly, cytokinesis, and abscission. Small-molecule inhibitors of ABK are designed and synthesized to control cancer progression. A detailed understanding of ABK pathophysiology in different cancers is of great significance in designing and developing effective therapeutic strategies.

CONCLUSION

In this review, we have discussed the physiological significance of ABK followed by its role in cancer progression. We further highlighted available small-molecule inhibitors to control the tumor proliferation and their mechanistic insights.

Chromosomal Instability in Acute Myeloid Leukemia

Chromosomal instability (CIN), the increasing rate in which cells acquire new chromosomal alterations, is one of the hallmarks of cancer. Many studies highlighted CIN as an important mechanism in the origin, progression, and relapse of acute myeloid leukemia (AML). The ambivalent feature of CIN as a cancer-promoting or cancer-suppressing mechanism might explain the prognostic variability. The latter, however, is described in very few studies. This review highlights the important CIN mechanisms in AML, showing that CIN signatures can occur largely in all the three major AML types (de novo AML, secondary-AML, and therapy-related-AML). CIN features in AML could also be age-related and reflect the heterogeneity of the disease. Although most of these abnormalities show an adverse prognostic value, they also offer a strong new perspective on personalized therapy approaches, which goes beyond assessing CIN in vitro in patient tumor samples to predict prognosis. Current and emerging AML therapies are exploring CIN to improve AML treatment, which includes blocking CIN or increasing CIN beyond the limit threshold to induce cell death. We argue that the characterization of CIN features, not included yet in the routine diagnostic of AML patients, might provide a better stratification of patients and be extended to a more personalized therapeutic approach.

Mitotic syndicates Aurora Kinase B (AURKB) and mitotic arrest deficient 2 like 2 (MAD2L2) in cohorts of DNA damage response (DDR) and tumorigenesis

Aurora Kinase B (AURKB) and Mitotic Arrest Deficient 2 Like 2 (MAD2L2) are emerging anticancer therapeutic targets. AURKB and MAD2L2 are the least well studied members of their protein families, compared to AURKA and MAD2L1. Both AURKB and MAD2L2 play a critical role in mitosis, cell cycle checkpoint, DNA damage response (DDR) and normal physiological processes. However, the oncogenic roles of AURKB and MAD2L2 in tumorigenesis and genomic instability have also been reported. DDR acts as an arbitrator for cell fate by either repairing the damage or directing the cell to self-destruction. While there is strong evidence of interphase DDR, evidence of mitotic DDR is just emerging and remains largely unelucidated. To date, inhibitors of the DDR components show effective anti-cancer roles. Contrarily, long-term resistance towards drugs that target only one DDR target is becoming a challenge. Targeting interactions between protein-protein or protein-DNA holds prominent therapeutic potential. Both AURKB and MAD2L2 play critical roles in the success of mitosis and their emerging roles in mitotic DDR cannot be ignored. Small molecule inhibitors for AURKB are in clinical trials. A few lead compounds towards MAD2L2 inhibition have been discovered. Targeting mitotic DDR components and their interaction is emerging as a potent next generation anti-cancer therapeutic target. This can be done by developing small molecule inhibitors for AURKB and MAD2L2, thereby targeting DDR components as anti-cancer therapeutic targets and/or targeting mitotic DDR. This review focuses on AURKB and MAD2L2 prospective synergy to deregulate the p53 DDR pathway and promote favourable conditions for uncontrolled cell proliferation.

Spatiotemporal coordination of Greatwall-Endos-PP2A promotes mitotic progression

Mitotic entry involves inhibition of protein phosphatase 2A bound to its B55/Tws regulatory subunit (PP2A-B55/Tws), which dephosphorylates substrates of mitotic kinases. This inhibition is induced when Greatwall phosphorylates Endos, turning it into an inhibitor of PP2A-Tws. How this mechanism operates spatiotemporally in the cell is incompletely understood. We previously reported that the nuclear export of Greatwall in prophase promotes mitotic progression. Here, we examine the importance of the localized activities of PP2A-Tws and Endos for mitotic regulation. We find that Tws shuttles through the nucleus via a conserved nuclear localization signal (NLS), but expression of Tws in the cytoplasm and not in the nucleus rescues the development of tws mutants. Moreover, we show that Endos must be in the cytoplasm before nuclear envelope breakdown (NEBD) to be efficiently phosphorylated by Greatwall and to bind and inhibit PP2A-Tws. Disrupting the cytoplasmic function of Endos before NEBD results in subsequent mitotic defects. Evidence suggests that this spatiotemporal regulation is conserved in humans.

Aurora kinase A is essential for meiosis in mouse oocytes

The Aurora protein kinases are well-established regulators of spindle building and chromosome segregation in mitotic and meiotic cells. In mouse oocytes, there is significant Aurora kinase A (AURKA) compensatory abilities when the other Aurora kinase homologs are deleted. Whether the other homologs, AURKB or AURKC can compensate for loss of AURKA is not known. Using a conditional mouse oocyte knockout model, we demonstrate that this compensation is not reciprocal because female oocyte-specific knockout mice are sterile, and their oocytes fail to complete meiosis I. In determining AURKA-specific functions, we demonstrate that its first meiotic requirement is to activate Polo-like kinase 1 at acentriolar microtubule organizing centers (aMTOCs; meiotic spindle poles). This activation induces fragmentation of the aMTOCs, a step essential for building a bipolar spindle. We also show that AURKA is required for regulating localization of TACC3, another protein required for spindle building. We conclude that AURKA has multiple functions essential to completing MI that are distinct from AURKB and AURKC.

KIF14 controls ciliogenesis via regulation of Aurora A and is important for Hedgehog signaling

Primary cilia play critical roles in development and disease. Their assembly and disassembly are tightly coupled to cell cycle progression. Here, we present data identifying KIF14 as a regulator of cilia formation and Hedgehog (HH) signaling. We show that RNAi depletion of KIF14 specifically leads to defects in ciliogenesis and basal body (BB) biogenesis, as its absence hampers the efficiency of primary cilium formation and the dynamics of primary cilium elongation, and disrupts the localization of the distal appendage proteins SCLT1 and FBF1 and components of the IFT-B complex. We identify deregulated Aurora A activity as a mechanism contributing to the primary cilium and BB formation defects seen after KIF14 depletion. In addition, we show that primary cilia in KIF14-depleted cells are defective in response to HH pathway activation, independently of the effects of Aurora A. In sum, our data point to KIF14 as a critical node connecting cell cycle machinery, effective ciliogenesis, and HH signaling.

Gene regulatory networks exhibit several kinds of memory: quantification of memory in biological and random transcriptional networks

Gene regulatory networks (GRNs) process important information in developmental biology and biomedicine. A key knowledge gap concerns how their responses change over time. Hypothesizing long-term changes of dynamics induced by transient prior events, we created a computational framework for defining and identifying diverse types of memory in candidate GRNs. We show that GRNs from a wide range of model systems are predicted to possess several types of memory, including Pavlovian conditioning. Associative memory offers an alternative strategy for the biomedical use of powerful drugs with undesirable side effects, and a novel approach to understanding the variability and time-dependent changes of drug action. We find evidence of natural selection favoring GRN memory. Vertebrate GRNs overall exhibit more memory than invertebrate GRNs, and memory is most prevalent in differentiated metazoan cell networks compared with undifferentiated cells. Timed stimuli are a powerful alternative for biomedical control of complex in vivo dynamics without genomic editing or transgenes.

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Gene regulatory networks' dynamics are modified by transient stimuli

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GRNs have several different types of memory, including associative conditioning

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Evolution favored GRN memory, and differentiated cells have the most memory capacity

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Training GRNs offers a novel biomedical strategy not dependent on genetic rewiring

Inhibition of Aurora Kinase B activity disrupts development and differentiation of salivary glands

Little is known about the key molecules that regulate cell division during organogenesis. Here we determine the role of the cell cycle promoter aurora kinase B (AURKB) during development, using embryonic salivary glands (E-SGs) as a model. AURKB is a serine/threonine kinase that regulates key events in mitosis, which makes it an attractive target for tailored anticancer therapy. Many reports have elaborated on the role of AURKB in neoplasia and cancer; however, no previous study has shown its role during organ development. Our previous experiments have highlighted the essential requirement for AURKB during adult exocrine regeneration. To investigate if AURKB is similarly required for progression during embryonic development, we pharmacologically inhibited AURKB in developing submandibular glands (SMGs) at embryonic day (E)13.5 and E16.5, using the highly potent and selective drug Barasertib. Inhibition of AURKB interfered with the expansion of the embryonic buds. Interestingly, this effect on SMG development was also seen when the mature explants (E16.5) were incubated for 24 h with another cell cycle inhibitor Aphidicolin. Barasertib prompted apoptosis, DNA damage and senescence, the markers of which (cleaved caspase 3, γH2AX, SA-βgal and p21, respectively), were predominantly seen in the developing buds. In addition to a reduction in cell cycling and proliferation of the epithelial cells in response to AURKB inhibition, Barasertib treatment led to an excessive generation of reactive oxygen species (ROS) that resulted in downregulation of the acinar differentiation marker Mist1. Importantly, inhibition of ROS was able to rescue this loss of identity, with Mist1 expression maintained despite loss of AURKB. Together, these data identify AURKB as a key molecule in supporting embryonic development and differentiation, while inhibiting senescence-inducing signals during organogenesis.

Structure-Based Discovery and Bioactivity Evaluation of Novel Aurora-A Kinase Inhibitors as Anticancer Agents via Docking-Based Comparative Intermolecular Contacts Analysis (dbCICA)

Aurora-A kinase plays a central role in mitosis, where aberrant activation contributes to cancer by promoting cell cycle progression, genomic instability, epithelial-mesenchymal transition, and cancer stemness. Aurora-A kinase inhibitors have shown encouraging results in clinical trials but have not gained Food and Drug Administration (FDA) approval. An innovative computational workflow named Docking-based Comparative Intermolecular Contacts Analysis (dbCICA) was applied—aiming to identify novel Aurora-A kinase inhibitors—using seventy-nine reported Aurora-A kinase inhibitors to specify the best possible docking settings needed to fit into the active-site binding pocket of Aurora-A kinase crystal structure, in a process that only potent ligands contact critical binding-site spots, distinct from those occupied by less-active ligands. Optimal dbCICA models were transformed into two corresponding pharmacophores. The optimal one, in capturing active hits and discarding inactive ones, validated by receiver operating characteristic analysis, was used as a virtual in-silico search query for screening new molecules from the National Cancer Institute database. A fluorescence resonance energy transfer (FRET)-based assay was used to assess the activity of captured molecules and five promising Aurora-A kinase inhibitors were identified. The activity was next validated using a cell culture anti-proliferative assay (MTT) and revealed a most potent lead 85(NCI 14040) molecule after 72 h of incubation, scoring IC₅₀ values of 3.5–11.0 μM against PANC1 (pancreas), PC-3 (prostate), T-47D and MDA-MB-231 (breast)cancer cells, and showing favorable safety profiles (27.5 μM IC₅₀ on fibroblasts). Our results provide new clues for further development of Aurora-A kinase inhibitors as anticancer molecules.

The coordination of nuclear envelope assembly and chromosome segregation in metazoans

The nuclear envelope (NE) is composed of two lipid bilayer membranes that enclose the eukaryotic genome. In interphase, the NE is perforated by thousands of nuclear pore complexes (NPCs), which allow transport in and out of the nucleus. During mitosis in metazoans, the NE is broken down and then reassembled in a manner that enables proper chromosome segregation and the formation of a single nucleus in each daughter cell. Defects in coordinating NE reformation and chromosome segregation can cause aberrant nuclear architecture. This includes the formation of micronuclei, which can trigger a catastrophic mutational process commonly observed in cancers called chromothripsis. Here, we discuss the current understanding of the coordination of NE reformation with chromosome segregation during mitotic exit in metazoans. We review differing models in the field and highlight recent work suggesting that normal NE reformation and chromosome segregation are physically linked through the timing of mitotic spindle disassembly.

In silico pathway analysis based on chromosomal instability in breast cancer patients

BACKGROUND

Complex genomic changes that arise in tumors are a consequence of chromosomal instability. In tumor cells genomic aberrations disrupt core signaling pathways involving various genes, thus delineating of signaling pathways can help understand the pathogenesis of cancer. The bioinformatics tools can further help in identifying networks of interactions between the genes to get a greater biological context of all genes affected by chromosomal instability.

METHODS

Karyotypic analyses was done in 150 clinically confirmed breast cancer patients and 150 age and gender matched healthy controls after 72 h Peripheral lymphocyte culturing and GTG-banding. Reactome database from Cytoscape software version 3.7.1 was used to perform in-silico analysis (functional interaction and gene enrichment).

RESULTS

Frequency of chromosomal aberrations (structural and numerical) was found to be significantly higher in patients as compared to controls. The genes harbored by chromosomal regions showing increased aberration frequency in patients were further analyzed in-silico. Pathway analysis on a set of genes that were not linked together revealed that genes HDAC3, NCOA1, NLRC4, COL1A1, RARA, WWTR1, and BRCA1 were enriched in the RNA Polymerase II Transcription pathway which is involved in recruitment, initiation, elongation and dissociation during transcription.

CONCLUSION

The current study employs the information inferred from chromosomal instability analysis in a non-target tissue for determining the genes and the pathways associated with breast cancer. These results can be further extrapolated by performing either mutation analysis in the genes/pathways deduced or expression analysis which can pinpoint the relevant functional impact of chromosomal instability.

Aurora kinase inhibition sensitizes melanoma cells to T-cell-mediated cytotoxicity

Although immunotherapy has achieved impressive durable clinical responses, many cancers respond only temporarily or not at all to immunotherapy. To find novel, targetable mechanisms of resistance to immunotherapy, patient-derived melanoma cell lines were transduced with 576 open reading frames, or exposed to arrayed libraries of 850 bioactive compounds, prior to co-culture with autologous tumor-infiltrating lymphocytes (TILs). The synergy between the targets and TILs to induce apoptosis, and the mechanisms of inhibiting resistance to TILs were interrogated. Gene expression analyses were performed on tumor samples from patients undergoing immunotherapy for metastatic melanoma. Finally, the effect of inhibiting the top targets on the efficacy of immunotherapy was investigated in multiple preclinical models. Aurora kinase was identified as a mediator of melanoma cell resistance to T-cell-mediated cytotoxicity in both complementary screens. Aurora kinase inhibitors were validated to synergize with T-cell-mediated cytotoxicity in vitro. The Aurora kinase inhibition-mediated sensitivity to T-cell cytotoxicity was shown to be partially driven by p21-mediated induction of cellular senescence. The expression levels of Aurora kinase and related proteins were inversely correlated with immune infiltration, response to immunotherapy and survival in melanoma patients. Aurora kinase inhibition showed variable responses in combination with immunotherapy in vivo, suggesting its activity is modified by other factors in the tumor microenvironment. These data suggest that Aurora kinase inhibition enhances T-cell cytotoxicity in vitro and can potentiate antitumor immunity in vivo in some but not all settings. Further studies are required to determine the mechanism of primary resistance to this therapeutic intervention.

SET/TAF1 forms a distance-dependent feedback loop with Aurora B and Bub1 as a tension sensor at centromeres

During mitosis, spatiotemporal regulation of phosphorylation at the kinetochore is essential for accurate chromosome alignment and proper chromosome segregation. Aurora B kinase phosphorylates kinetochore substrates to correct improper kinetochore-microtubule (KT-MT) attachments, whereas tension across the centromeres inactivates Aurora B kinase, and PP2A phosphatase dephosphorylates the kinetochore proteins to stabilize the attachments. However, the molecular entity of the tension sensing mechanism remains elusive. In a previous report, we showed that centromeric SET/TAF1 on Sgo2 up-regulates Aurora B kinase activity via PP2A inhibition in prometaphase. Here we show that Aurora B and Bub1 at the centromere/kinetochore regulate both kinase activities one another in an inter-kinetochore distance-dependent manner, indicating a positive feedback loop. We further show that the centromeric pool of SET on Sgo2 depends on Bub1 kinase activity, and the centromeric localization of SET decreases in a distance-dependent manner, thereby inactivating Aurora B in metaphase. Consistently, ectopic targeting of SET to the kinetochores during metaphase hyperactivates Aurora B via PP2A inhibition, and thereby rescues the feedback loop. Thus, we propose that SET, Aurora B and Bub1 form a distance-dependent positive feedback loop, which spatiotemporally may act as a tension sensor at centromeres.

Reversine exerts cytotoxic effects through multiple cell death mechanisms in acute lymphoblastic leukemia

PURPOSE

Acute lymphoblastic leukemia (ALL) is an aggressive hematological cancer with limited therapeutic options for adult patients. Aurora kinases have drawn attention as potential targets in hematological neoplasms due to their high expression and biological functions. Aurora kinase A (AURKA) and AURKB are essential for a successful mitosis, acting in spindle mitotic organization and cytokinesis. Reversine is a synthetic purine analog that acts as a multi-kinase inhibitor with anti-neoplastic activity by targeting AURKA and AURKB.

METHODS

ALL patient gene expression data were retrieved from the Amazonia!

DATABASE

For functional assays, Jurkat (T-ALL) and Namalwa (B-ALL) cells were exposed to increasing concentrations of reversine and submitted to various cellular and molecular assays.

RESULTS

We found that AURKB expression was higher in ALL patient samples compared to normal lymphocytes (p < 0.0001). The ALL cell lines tested displayed aberrant AURKA and AURKB expression. In Jurkat and Namalwa cells, reversine reduced cell viability in a dose- and time-dependent manner (p < 0.05). Reversine also significantly reduced the viability of primary ALL cells. Reversine induced apoptosis and autophagy, and reduced cell proliferation in both cell lines (p < 0.05). Mitotic catastrophe markers, including cell cycle arrest at G₂/M, increased cell size and DNA damage, were observed upon reversine exposure. Short- and long-term treatment with reversine inhibited autonomous clonogenicity (p < 0.05). At the molecular level, reversine reduced AURKB activity, induced SQSTM1/p62 consumption, and increased LC3BII and γ-H2AX levels. In Namalwa cells, reversine modulated 25 out of 84 autophagy-related genes, including BCL2, BAD, ULK1, ATG10, IRGM and MAP1LC3B, which indicates that reversine acts by initiating and sustaining autophagy signals in ALL cells.

CONCLUSIONS

From our data we conclude that reversine reduces the viability of ALL cells by triggering multiple cell death mechanisms, including apoptosis, mitotic catastrophe, and autophagy. Our findings highlight reversine as a potential anticancer agent for ALL.

Kv10.1 Regulates Microtubule Dynamics during Mitosis

Kv10.1 (potassium voltage-gated channel subfamily H member 1, known as EAG1 or Ether-à-go-go 1), is a voltage-gated potassium channel, prevailingly expressed in the central nervous system. The aberrant expression of Kv10.1 is detected in over 70% of all human tumor tissues and correlates with poorer prognosis. In peripheral tissues, Kv10.1 is expressed almost exclusively during the G2/M phase of the cell cycle and regulates its progression-downregulation of Kv10.1 extends the duration of the G2/M phase both in cancer and healthy cells. Here, using biochemical and imaging techniques, such as live-cell measurements of microtubule growth and of cytosolic calcium, we elucidate the mechanisms of Kv10.1-mediated regulation at the G2/M phase. We show that Kv10.1 has a dual effect on mitotic microtubule dynamics. Through the functional interaction with ORAI1 (calcium release-activated calcium channel protein 1), it modulates cytosolic calcium oscillations, thereby changing microtubule behavior. The inhibition of either Kv10.1 or ORAI1 stabilizes the microtubules. In contrast, the knockdown of Kv10.1 increases the dynamicity of mitotic microtubules, resulting in a stronger spindle assembly checkpoint, greater mitotic spindle angle, and a decrease in lagging chromosomes. Understanding of Kv10.1-mediated modulation of the microtubule architecture will help to comprehend how cancer tissue benefits from the presence of Kv10.1, and thereby increase the efficacy and safety of Kv10.1-directed therapeutic strategies.

Microsatellite frameshift variants in SGO1 of gastric cancer are not always associated with MSI status

AIMS

Although frameshift variants in the microsatellite area of shugoshin 1 (SGO1) have been reported in the context of microsatellite instability-high (MSI-H)/deficient mismatch repair gastrointestinal cancer, most have been evaluated only in early stage I-III patients, and only two of its five microsatellite regions have been evaluated. Therefore, we investigated the frequency and MSI status of microsatellite frameshift variants in gastric cancer cases, including stage IV.

METHODS

In a total of 55 cases, 30 gastric cancer resection and 25 non-resection cases, DNA was extracted from both tumour and normal parts and PCR was performed. The variant was confirmed by TA cloning, and MSI was evaluated using GeneMapper software.

RESULTS

A frameshift variant of c.973delA was observed in 16 of the 45 evaluable cases. Its frequency was 35.6%. Of the 25 cases that could be assessed for MSI status, two cases of MSI-H were associated with the c.973delA SGO1 variant. However, c.973delA SGO1 variant was also observed in four cases of microsatellite stable.

CONCLUSION

Our study shows that SGO1 frameshift variants are not always associated with MSI status.

Aurora kinase B inhibitor barasertib (AZD1152) inhibits glucose metabolism in gastric cancer cells

Barasertib is a highly selective Aurora kinase B (AURKB) inhibitor and has been widely applied in a variety of cancer cells to investigate the regulatory function of AURKB. However, the effect of barasertib on glucose metabolism in gastric cancer (GC) remains illustrated. Here, barasertib was identified to effectively reduce glucose uptake and lactate production in GC cells in a dose-dependent and time-dependent manner. The expression levels of GLUT1, LDHA and HK2 were decreased by barasertib treatment of GC cells. Furthermore, we found that barasertib induced the expression of ribosomal protein S7 (RPS7), as a tumor suppressor, to regulate glucose metabolism. Silencing of RPS7 rescued the effects of barasertib on glucose metabolism in GC cells. Overexpression of RPS7 suppressed the promoter activity of C-Myc, which has been identified as an important regulator of glucose metabolism in cancer cells. The clinical data showed that the expression level of AURKB in GC patients' sera and tissues were positively correlated with those of C-Myc, GLUT1 and LDHA, but negatively with that of RPS7. Therefore, these findings provide new evidence that barasertib regulates GC cell glucose metabolism by inducing the RPS7/C-Myc signal pathway, and have important implications for the development of therapeutic approaches using AURKB as a target protein to prevent tumor recurrence.

Mutational analysis of Aurora kinase C gene in Egyptian patients with macrozoospermia

Macrozoospermia is a rare syndrome. The key marker of the disease is a high percentage of spermatozoa with abnormal phenotypes namely enlarged head and multiple tails. The presence of at least 70% of spermatozoa with a large head is usually associated with Aurora kinase C gene (AURKC) mutations. We sought to assess AURKC as a potential genetic actor of macrozoospermia in a sample of infertile Egyptian men. We recruited 30 patients and conducted a clinical examination, semen analysis, and DNA sequencing and RFLP for AURKC. We diagnosed 17 patients with characteristic macrozoospermia and classified them into eight severe and nine mild cases. We detected genetic variants of AURKC in five patients (29.4%): Three patients with severe macrozoospermia had c.144delC mutations in exon 3 (37.5% of the severe), and two mild cases had c.1157G>A polymorphism in the 3' UTR (22.2% of the mild). A successful intracytoplasmic sperm injection (ICSI) was achieved only with a severe macrozoospermia patient without apparent AURKC mutation. The present study is the first report to link macrozoospermia and AURKC mutations in Egypt. The study recommends macrozoospermia patients to perform AURKC gene analysis and attempt ICSI, even those with a high percentage of large head spermatozoa.

Sulfonamide-based 4-anilinoquinoline derivatives as novel dual Aurora kinase (AURKA/B) inhibitors: Synthesis, biological evaluation and in silico insights

Aurora kinases (AURKs) were identified as promising druggable targets for targeted cancer therapy. Aiming at the development of novel chemotype of dual AURKA/B inhibitors, herein we report the design and synthesis of three series of 4-anilinoquinoline derivatives bearing a sulfonamide moiety (5a-d, 9a-d and 11a-d). The % inhibition of AURKA/B was determined for all target quinolines, then compounds showed more than 50% inhibition on either of the enzymes, were evaluated further for their IC₅₀ on the corresponding enzyme. In particular, compound 9d displayed potent AURKA/B inhibitory activities with IC₅₀ of 0.93 and 0.09 µM, respectively. Also, 9d emerged as the most efficient anti-proliferative analogue in the US-NCI anticancer assay toward the NCI 60 cell lines panel, with broad spectrum activity against different cell lines from diverse cancer subpanels. Docking studies, confirmed that, the sulfonamide SO₂ oxygen was involved in a hydrogen bond with Lys162 and Lys122 in AURKA and AURKB, respectively, whereas, the sulfonamide NH could catch hydrogen bond interaction with the surrounding amino acid residues Lys141, Glu260, and Asn261 in AURKA and Lys101, Glu177, and Asp234 in AURKB. Furthermore, N1 nitrogen of the quinoline scaffold formed an essential hydrogen bond with the hinge region key amino acids Ala213 and Ala173 in AURKA and AURKB, respectively.