Aurora B: A new promising therapeutic target in cancer

Preserving Genome Integrity: Unveiling the Roles of ESCRT Machinery

The endosomal sorting complex required for transport (ESCRT) machinery is composed of an articulated architecture of proteins that assemble at multiple cellular sites. The ESCRT machinery is involved in pathways that are pivotal for the physiology of the cell, including vesicle transport, cell division, and membrane repair. The subunits of the ESCRT I complex are mainly responsible for anchoring the machinery to the action site. The ESCRT II subunits function to bridge and recruit the ESCRT III subunits. The latter are responsible for finalizing operations that, independently of the action site, involve the repair and fusion of membrane edges. In this review, we report on the data related to the activity of the ESCRT machinery at two sites: the nuclear membrane and the midbody and the bridge linking cells in the final stages of cytokinesis. In these contexts, the machinery plays a significant role for the protection of genome integrity by contributing to the control of the abscission checkpoint and to nuclear envelope reorganization and correlated resilience. Consistently, several studies show how the dysfunction of the ESCRT machinery causes genome damage and is a codriver of pathologies, such as laminopathies and cancer.

A comprehensive review on role of Aurora kinase inhibitors (AKIs) in cancer therapeutics

Aurora kinases (AURKs) are a family of serine /threonine protein kinases that have a crucial role in cell cycle process mainly in the event of chromosomal segregation, centrosome maturation and cytokinesis. The family consists of three members including Aurora kinase A (AURK-A), Aurora kinase B (AURK-B) and Aurora kinase C (AURK-C). All AURKs contain a conserved kinase domain for their activity but differ in their cellular localization and functions. AURK-A and AURK-B are expressed mainly in somatic cells while the expression of AURK-C is limited to germ cells. AURK-A promotes G2 to M transition of cell cycle by controlling centrosome maturation and mitotic spindle assembly. AURK-B and AURK-C form the chromosome passenger complex (CPC) that ensures proper chromosomal alignments and segregation. Aberrant expression of AURK-A and AURK-B has been detected in several solid tumours and malignancies. Hence, they have become an attractive therapeutic target against cancer. The first part of this review focuses on AURKs structure, functions, subcellular localization, and their role in tumorigenesis. The review also highlights the functional and clinical impact of selective as well as pan kinase inhibitors. Currently, >60 compounds that target AURKs are in preclinical and clinical studies. The drawbacks of existing inhibitors like selectivity, drug resistance and toxicity have also been addressed. Since, majority of inhibitors are Aurora kinase inhibitor (AKI) type-1 that bind to the active (DFGin and Cin) conformation of the kinase, this information may be utilized to design highly selective kinase inhibitors that can be combined with other therapeutic agents for better clinical outcomes.

Centrosomes and associated proteins in pathogenesis and treatment of breast cancer

Breast cancer is the most prevalent malignancy among women worldwide. Despite significant advances in treatment, it remains one of the leading causes of female mortality. The inability to effectively treat advanced and/or treatment-resistant breast cancer demonstrates the need to develop novel treatment strategies and targeted therapies. Centrosomes and their associated proteins have been shown to play key roles in the pathogenesis of breast cancer and thus represent promising targets for drug and biomarker development. Centrosomes are fundamental cellular structures in the mammalian cell that are responsible for error-free execution of cell division. Centrosome amplification and aberrant expression of its associated proteins such as Polo-like kinases (PLKs), Aurora kinases (AURKs) and Cyclin-dependent kinases (CDKs) have been observed in various cancers, including breast cancer. These aberrations in breast cancer are thought to cause improper chromosomal segregation during mitosis, leading to chromosomal instability and uncontrolled cell division, allowing cancer cells to acquire new genetic changes that result in evasion of cell death and the promotion of tumor formation. Various chemical compounds developed against PLKs and AURKs have shown meaningful antitumorigenic effects in breast cancer cells in vitro and in vivo. The mechanism of action of these inhibitors is likely related to exacerbation of numerical genomic instability, such as aneuploidy or polyploidy. Furthermore, growing evidence demonstrates enhanced antitumorigenic effects when inhibitors specific to centrosome-associated proteins are used in combination with either radiation or chemotherapy drugs in breast cancer. This review focuses on the current knowledge regarding the roles of centrosome and centrosome-associated proteins in breast cancer pathogenesis and their utility as novel targets for breast cancer treatment.

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.

LINC01134: a pivotal oncogene with promising predictive maker and therapeutic target in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) represents a leading and fatal malignancy within the gastrointestinal tract. Recent advancements highlight the pivotal role of long non-coding RNAs (lncRNAs) in diverse biological pathways and pathologies, particularly in tumorigenesis. LINC01134, a particular lncRNA, has attracted considerable attention due to its oncogenic potential in hepatoma. Current research underscores LINC01134's potential in augmenting the onset and progression of HCC, with notable implications in drug resistance. This review comprehensively explores the molecular functions and regulatory mechanisms of LINC01134 in HCC, offering a fresh perspective for therapeutic interventions. By delving into LINC01134's multifaceted roles, we aim to foster novel strategies in HCC management.

Hepatitis C virus fitness can influence the extent of infection-mediated epigenetic modifications in the host cells

Introduction

Cellular epigenetic modifications occur in the course of viral infections. We previously documented that hepatitis C virus (HCV) infection of human hepatoma Huh-7.5 cells results in a core protein-mediated decrease of Aurora kinase B (AURKB) activity and phosphorylation of Serine 10 in histone H3 (H3Ser10ph) levels, with an affectation of inflammatory pathways. The possible role of HCV fitness in infection-derived cellular epigenetic modifications is not known.

Methods

Here we approach this question using HCV populations that display a 2.3-fold increase in general fitness (infectious progeny production), and up to 45-fold increase of the exponential phase of intracellular viral growth rate, relative to the parental HCV population.

Results

We show that infection resulted in a HCV fitness-dependent, average decrease of the levels of H3Ser10ph, AURKB, and histone H4 tri-methylated at Lysine 20 (H4K20m3) in the infected cell population. Remarkably, the decrease of H4K20m3, which is a hallmark of cellular transformation, was significant upon infection with high fitness HCV but not upon infection with basal fitness virus.

Discussion

Here we propose two mechanisms ─which are not mutually exclusive─ to explain the effect of high viral fitness: an early advance in the number of infected cells, or larger number of replicating RNA molecules per cell. The implications of introducing HCV fitness as an influence in virus-host interactions, and for the course of liver disease, are warranted. Emphasis is made in the possibility that HCV-mediated hepatocellular carcinoma may be favoured by prolonged HCV infection of a human liver, a situation in which viral fitness is likely to increase.

Pediatric Acute Lymphoblastic Leukemia Emerging Therapies-From Pathway to Target

Over the past 40 years, the 5-years-overall survival rate of pediatric cancer reached 75-80%, and for acute lymphoblastic leukemia (ALL), exceeded 90%. Leukemia continues to be a major cause of mortality and morbidity for specific patient populations, including infants, adolescents, and patients with high-risk genetic abnormalities. The future of leukemia treatment needs to count better on molecular therapies as well as immune and cellular therapy. Advances in the scientific interface have led naturally to advances in the treatment of childhood cancer. These discoveries have involved the recognition of the importance of chromosomal abnormalities, the amplification of the oncogenes, the aberration of tumor suppressor genes, as well as the dysregulation of cellular signaling and cell cycle control. Lately, novel therapies that have already proven efficient on relapsed/refractory ALL in adults are being evaluated in clinical trials for young patients. Tirosine kinase inhibitors are, by now, part of the standardized treatment of Ph+ALL pediatric patients, and Blinatumomab, with promising results in clinical trials, received both FDA and EMA approval for use in children. Moreover, other targeted therapies such as aurora-kinase inhibitors, MEK-inhibitors, and proteasome-inhibitors are involved in clinical trials that include pediatric patients. This is an overview of the novel leukemia therapies that have been developed starting from the molecular discoveries and those that have been applied in pediatric populations.

A Review of the Regulatory Mechanisms of N-Myc on Cell Cycle

Neuroblastoma has obvious heterogeneity. It is one of the few undifferentiated malignant tumors that can spontaneously degenerate into completely benign tumors. However, for its high-risk type, even with various intensive treatment options, the prognosis is still unsatisfactory. At the same time, a large number of research data show that the abnormal amplification and high-level expression of the MYCN gene are positively correlated with the malignant progression, poor prognosis, and mortality of neuroblastoma. In this context, this article explores the role of the N-Myc, MYCN gene expression product on its target genes related to the cell cycle and reveals its regulatory network in promoting tumor proliferation and malignant progression. We hope it can provide ideas and direction for the research and development of drugs targeting N-Myc and its downstream target genes.

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.

FCH domain only 1 (FCHo1), a potential new biomarker for lung cancer

Lung carcinoma is the main reason for cancer-associated deaths in the world. In a previous study, FCH domain only 1 (FCHo1) which is managed by protein kinase B (AKT), was shown to be activated in lung cancer. FCHo1 knockdown has previously been shown to cause cell death in lung cancer. However, the specific roles of FCHo1 in lung carcinoma remain elusive. Herein, we propose that FCHo1's intracellular mechanism targets the G1 to S phase transition, following the M phase. We demonstrated that F-BAR and mu homology domains exist separately in human lung tissues and that one truncated form is not detected in patients with lung cancer. Furthermore, quantitative global proteome analysis of FCHo1 indicated that the inhibition of G1/S phase transition and FCHo1 RNAi led to the death of cells in the G1/S phase. Noninvasive viral aerosol-mediated delivery of FCHo1 shRNA suppressed cancer progression in mice with non-small-cell lung cancer (NSCLC), suggesting that the delivery of FCHo1 shRNA could be a meaningful therapeutic strategy in lung cancer. Additional studies are needed to make clear the detailed mechanism of action of FCHo1.

Identification of a novel anticancer mechanism of Paeoniae Radix extracts based on systematic transcriptome analysis

Paeoniae Radix (PR) has a great therapeutic value in many clinical applications; however, the presence of various bioactive compounds and its complicated effects on human health makes its precise mechanisms of action unclear. This study investigated the effects of PR at the molecular pathway level by profiling genome-wide gene expression changes following dose-dependent treatment of human lung cancer cells (A549) with PR water extract (WPR), PR ethanol extracts (EPR), as well as their individual components. We found that PR exerts anticancer effects in A549 cells by regulating numerous pathways. Specifically, EPR and two compounds, namely, hederagenin (HG) and oleanolic acid (OA), significantly downregulate the Aurora B pathway. Furthermore, we generated an integrated PR extracts-compounds-target genes network in the Aurora B pathway to understand their interactions. Our findings reinforce that inhibiting Aurora kinase activity is a therapeutic target for treating cancers, providing the potential for novel mechanisms of action for PR and its components against lung cancer.

Therapeutic targeting of "undruggable" MYC

c-MYC controls global gene expression and regulates cell proliferation, cell differentiation, cell cycle, metabolism and apoptosis. According to some estimates, MYC is dysregulated in ≈70% of human cancers and strong evidence implicates aberrantly expressed MYC in both tumor initiation and maintenance. In vivo studies show that MYC inhibition elicits a prominent anti-proliferative effect and sustained tumor regression while any alteration on healthy tissue remains reversible. This opens an exploitable window for treatment that makes MYC one of the most appealing therapeutic targets for cancer drug development. This review describes the main functional and structural features of the protein structure of MYC and provides a general overview of the most relevant or recently identified interactors that modulate MYC oncogenic activity. This review also summarizes the different approaches aiming to abrogate MYC oncogenic function, with a particular focus on the prototype inhibitors designed for the direct and indirect targeting of MYC.

The Abscission Checkpoint: A Guardian of Chromosomal Stability

The abscission checkpoint contributes to the fidelity of chromosome segregation by delaying completion of cytokinesis (abscission) when there is chromatin lagging in the intercellular bridge between dividing cells. Although additional triggers of an abscission checkpoint-delay have been described, including nuclear pore defects, replication stress or high intercellular bridge tension, this review will focus only on chromatin bridges. In the presence of such abnormal chromosomal tethers in mammalian cells, the abscission checkpoint requires proper localization and optimal kinase activity of the Chromosomal Passenger Complex (CPC)-catalytic subunit Aurora B at the midbody and culminates in the inhibition of Endosomal Sorting Complex Required for Transport-III (ESCRT-III) components at the abscission site to delay the final cut. Furthermore, cells with an active checkpoint stabilize the narrow cytoplasmic canal that connects the two daughter cells until the chromatin bridges are resolved. Unsuccessful resolution of chromatin bridges in checkpoint-deficient cells or in cells with unstable intercellular canals can lead to chromatin bridge breakage or tetraploidization by regression of the cleavage furrow. In turn, these outcomes can lead to accumulation of DNA damage, chromothripsis, generation of hypermutation clusters and chromosomal instability, which are associated with cancer formation or progression. Recently, many important questions regarding the mechanisms of the abscission checkpoint have been investigated, such as how the presence of chromatin bridges is signaled to the CPC, how Aurora B localization and kinase activity is regulated in late midbodies, the signaling pathways by which Aurora B implements the abscission delay, and how the actin cytoskeleton is remodeled to stabilize intercellular canals with DNA bridges. Here, we review recent progress toward understanding the mechanisms of the abscission checkpoint and its role in guarding genome integrity at the chromosome level, and consider its potential implications for cancer therapy.

Synthesis, In Vitro and In Silico Anticancer Activity of New 4-Methylbenzamide Derivatives Containing 2,6-Substituted Purines as Potential Protein Kinases Inhibitors

A novel class of potential protein kinase inhibitors 7–16 was synthesized in high yields using various substituted purines. The most promising compounds, 7 and 10, exhibited inhibitory activity against seven cancer cell lines. The IC₅₀ values for compounds 7 and 10 were 2.27 and 2.53 μM for K562 cells, 1.42 and 1.52 μM for HL-60 cells, and 4.56 and 24.77 μM for OKP-GS cells, respectively. In addition, compounds 7 and 10 dose-dependently induced the apoptosis and cell cycle arrest at G2/M phase, preventing the cell division of OKP-GS cells. Compounds 7, 9, and 10 showed 36–45% inhibitory activity against PDGFRα and PDGFRβ at the concentration of 1 μM. Molecular modeling experiments showed that obtained compounds could bind to PDGFRα as either type 1 (compound 7, ATP-competitive) or type 2 (compound 10, allosteric) inhibitors, depending on the substituent in the amide part of the molecule.

Indolin-2-one derivatives as selective Aurora B kinase inhibitors targeting breast cancer

Aurora B is a pivotal cell cycle regulator where errors in its function results in polyploidy, genetic instability, and tumorigenesis. It is overexpressed in many cancers, consequently, targeting Aurora B with small molecule inhibitors constitutes a promising approach for anticancer therapy. Guided by structure-based design and molecular hybridization approach we developed a series of fifteen indolin-2-one derivatives based on a previously reported indolin-2-one-based multikinase inhibitor (1). Seven derivatives, 5g, 6a, 6c-e, 7, and 8a showed preferential antiproliferative activity in NCI-60 cell line screening and out of these, carbamate 6e and cyclopropylurea 8a derivatives showed optimum activity against Aurora B (IC₅₀ = 16.2 and 10.5 nM respectively) and MDA-MB-468 cells (IC₅₀ = 32.6 ± 9.9 and 29.1 ± 7.3 nM respectively). Furthermore, 6e and 8a impaired the clonogenic potential of MDA-MB-468 cells. Mechanistic investigations indicated that 6e and 8a induced G2/M cell cycle arrest, apoptosis, and necrosis of MDA-MB-468 cells and western blot analysis of 8a effect on MDA-MB-468 cells revealed 8a's ability to reduce Aurora B and its downstream target, Histone H3 phosphorylation. 6e and 8a displayed better safety profiles than multikinase inhibitors such as sunitinib, showing no cytotoxic effects on normal rat cardiomyoblasts and murine hepatocytes. Finally, 8a demonstrated a more selective profile than 1 when screened against ten related kinases. Based on these findings, 8a represents a promising candidate for further development to target breast cancer via Aurora B selective inhibition.

A Novel Ruthenium(II) Complex With Lapachol Induces G2/M Phase Arrest Through Aurora-B Kinase Down-Regulation and ROS-Mediated Apoptosis in Human Prostate Adenocarcinoma Cells

Lapachol is a well-studied natural product that has been receiving great interest due to its anticancer properties that target oxidative stress. In the present work, two novel lapachol-containing ruthenium(II) complexes [Ru(Lap)(dppm)(bipy)]PF6 (1) and [Ru(Lap)(dppm)(phen)]PF6 (2) [Lap = lapachol, dppm = 1,1'-bis(diphosphino)methane, bipy = 2,2'-bipyridine, phen = 1,10-phenantroline] were synthesized, fully characterized, and investigated for their cellular and molecular responses on cancer cell lines. We found that both complexes exhibited a potent cytotoxic effect in a panel of cancer cell lines in monolayer cultures, as well as in a 3D model of multicellular spheroids formed from DU-145 human prostate adenocarcinoma cells. Furthermore, the complex (2) suppressed the colony formation, induced G2/M-phase arrest, and downregulated Aurora-B. The mechanism studies suggest that complex (2) stimulate the overproduction of reactive oxygen species (ROS) and triggers caspase-dependent apoptosis as a result of changes in expression of several genes related to cell proliferation and caspase-3 and -9 activation. Interestingly, we found that N-acetyl-L-cysteine, a ROS scavenger, suppressed the generation of intracellular ROS induced by complex (2), and decreased its cytotoxicity, indicating that ROS-mediated DNA damage leads the DU-145 cells into apoptosis. Overall, we highlighted that coordination of lapachol to phosphinic ruthenium(II) compounds considerably improves the antiproliferative activities of resulting complexes granting attractive selectivity to human prostate adenocarcinoma cells. The DNA damage response to ROS seems to be involved in the induction of caspase-mediated cell death that plays an important role in the complexes' cytotoxicity. Upon further investigations, this novel class of lapachol-containing ruthenium(II) complexes might indicate promising chemotherapeutic agents for prostate cancer therapy.

Experiments in the EpiDerm 3D Skin In Vitro Model and Minipigs In Vivo Indicate Comparatively Lower In Vivo Skin Sensitivity of Topically Applied Aneugenic Compounds

Risk management of in vitro aneugens for topically applied compounds is not clearly defined because there is no validated methodology to accurately measure compound concentration in proliferating stratum basale keratinocytes of the skin. Here, we experimentally tested several known aneugens in the EpiDerm reconstructed human skin in vitro micronucleus assay and compared the results to flow cytometric mechanistic biomarkers (phospho-H3; MPM2, DNA content). We then evaluated similar biomarkers (Ki-67, nuclear area) using immunohistochemistry in skin sections of minipigs following topical exposure the potent aneugens, colchicine, and hesperadin. Data from the EpiDerm model showed positive micronucleus responses for all aneugens tested following topical or direct media dosing with similar sensitivity when adjusted for applied dose. Quantitative benchmark dose-response analysis exhibited increases in the mitotic index biomarkers phospho-H3 and MPM2 for tubulin binders and polyploidy for aurora kinase inhibitors are at least as sensitive as the micronucleus endpoint. By comparison, the aneugens tested did not induce histopathological changes, increases in Ki-67 immunolabeling or nuclear area in skin sections from the in vivo minipig study at doses in significant excess of those eliciting a response in vitro. Results indicate the EpiDerm in vitro micronucleus assay is suitable for the hazard identification of aneugens. The lack of response in the minipig studies indicates that the barrier function of the minipig skin, which is comparable to human skin, protects from the effects of aneugens in vivo. These results provide a basis for conducting additional studies in the future to further refine this understanding.

Heteroarene-fused anthraquinone derivatives as potential modulators for human aurora kinase B

The quest for effective anticancer therapeutics continues to be extensively pursued. Over the past century, several drugs have been developed, however, a majority of these drugs have a poor therapeutic index and increased toxicity profile. Hence, there still exists ample opportunity to discover safe and effective anticancer drugs. Aurora Kinase B (AurB), a member of the Aurora kinase family and a key regulator of mitotic cell division, is found to be frequently overexpressed in a variety of human cancers and has thus emerged as an attractive target for the design of anticancer therapeutics. In the present study, a structure-based scaffold hopping approach was utilized to modify the heterocyclic moiety of (S)-3-(3-aminopyrrolidine-1-carbonyl)-4,11-dihydroxy-2-methylanthra [2,3-b]furan-5,10-dione (anthrafuran 1) to generate a series of heteroarene-fused anthraquinone derivatives, which were then subjected to virtual screening for the identification of potential AurB inhibitors. The obtained hits were subsequently synthesized and evaluated by using a combination of in silico and biophysical techniques for elucidating their in vitro binding and inhibition activity with recombinantly expressed AurB. Four identified hits presented an improved binding profile as compared to their parent analog anthrafuran 1. One derivative, anthrathiophene 2 demonstrated excellent in vitro inhibition of AurB (7.3 μM).

Targeting aurora kinases as a potential prognostic and therapeutical biomarkers in pediatric acute lymphoblastic leukaemia

Aurora kinases (AURKA and AURKB) are mitotic kinases with an important role in the regulation of several mitotic events, and in hematological malignancies, AURKA and AURKB hyperexpression are found in patients with cytogenetic abnormalities presenting a unfavorable prognosis. The aim of this study was evaluated the mRNA expression profile of pediatric Acute Lymphoblastic Leukaemia (ALL) patients and the efficacy of two AURKA and AURKB designed inhibitors (GW809897X and GW806742X) in a leukemia cell line as a potential novel therapy for ALL patients. Cellular experiments demonstrated that both inhibitors induced cell death with caspase activation and cell cycle arrest, however only the GW806742X inhibitor decreased with more efficacy AURKA and AURKB expression in K-562 leukemia cells. In ALL patients both AURKA and AURKB showed a significant overexpression, when compared to health controls. Moreover, AURKB expression level was significant higher than AURKA in patients, and predicted a poorer prognosis with significantly lower survival rates. No differences were found in AURKA and AURKB expression between gene fusions, immunophenotypic groups, white blood cells count, gender or age. In summary, the results in this study indicates that the AURKA and AURKB overexpression are important findings in pediatric ALL, and designed inhibitor, GW806742X tested in vitro were able to effectively inhibit the gene expression of both aurora kinases and induce apoptosis in K-562 cells, however our data clearly shown that AURKB proves to be a singular finding and potential prognostic biomarker that may be used as a promising therapeutic target to those patients.

A simple and robust cell-based assay for the discovery of novel cytokinesis inhibitors

Cytokinesis is the last step of mitotic cell division that separates the cytoplasm of dividing cells. Small molecule inhibitors targeting either the elements of the regulatory pathways controlling cytokinesis, or the terminal effectors have been of interest as potential drug candidates for the treatment of various diseases. Here we present a detailed protocol for a cell-based cytokinesis assay that can be used for the discovery of novel cytokinesis inhibitors. The assay is performed in a 96-well plate format in 48 h. Living cells, nuclei and nuclei of dead cells are identified by a single staining step using three fluorescent dyes, followed by rapid live cell imaging. The primary signal is the nuclei-to-cell ratio (NCR). In the presence of cytokinesis inhibitors, this ratio increases over time, as the ratio of multinucleated cells increases in the population. The ratio of dead nuclei to total nuclei provides a simultaneous measure of cytotoxicity. A screening window coefficient (Z`) of 0.65 indicates that the assay is suitable for screening purposes, as the positive and negative controls are well-separated. EC₅₀ values can be reliably determined in a single 96-well plate by using only six different compound concentrations, enabling the testing of 4 compounds per plate. An excellent test-retest reliability (R² = 0.998) was found for EC₅₀ values covering a ~1500-fold range of potencies. Established small molecule inhibitors of cytokinesis operating via direct action on actin dynamics or nonmuscle myosin II are used to demonstrate the robustness, simplicity and flexibility of the assay.

Phosphorylation by Aurora B kinase regulates caspase-2 activity and function

Mitotic catastrophe (MC) is an important oncosuppressive mechanism that serves to eliminate cells that become polyploid or aneuploid due to aberrant mitosis. Previous studies have demonstrated that the activation and catalytic function of caspase-2 are key steps in MC to trigger apoptosis and/or cell cycle arrest of mitotically defective cells. However, the molecular mechanisms that regulate caspase-2 activation and its function are unclear. Here, we identify six new phosphorylation sites in caspase-2 and show that a key mitotic kinase, Aurora B kinase (AURKB), phosphorylates caspase-2 at the highly conserved residue S384. We demonstrate that phosphorylation at S384 blocks caspase-2 catalytic activity and apoptosis function in response to mitotic insults, without affecting caspase-2 dimerisation. Moreover, molecular modelling suggests that phosphorylation at S384 may affect substrate binding by caspase-2. We propose that caspase-2 S384 phosphorylation by AURKB is a key mechanism that controls caspase-2 activation during mitosis.

RCC2 Promotes Esophageal Cancer Growth by Regulating Activity and Expression of the Sox2 Transcription Factor

Regulator of chromosome condensation 2 (RCC2) is a protein located in the centrosome, which ensures that cell division proceeds properly. Previous reports show that RCC2 is overexpressed in some cancers and could play a key role in tumor development, but the mechanisms concerning how this occurs are not understood. Furthermore, no evidence exists regarding its role in esophageal cancer. We studied the relevance of RCC2 in esophageal cancer growth and its regulation on Sox2, an important transcription factor promoting esophageal cancer. RCC2 was overexpressed in esophageal tumors compared with normal tissue, and this overexpression was associated with tumorigenicity by increasing cell proliferation, anchorage-independent growth, and migration. These oncogenic effects were accompanied by overexpression of Sox2. RCC2 upregulated and stabilized Sox2 expression and its target genes by inhibiting ubiquitination-mediated proteasome degradation. Likewise, RCC2 increased the transcriptional activity and promoter binding of Sox2. In vivo studies indicated that RCC2 and Sox2 were overexpressed in esophageal tumors compared with normal tissue, and this upregulation occurs in the esophageal basal cell layer for both proteins. In conditional knockout mice, RCC2 deletion decreased the tumor nodule formation and progression in the esophagus compared with wild-type mice. Proliferating cell nuclear antigen expression, a cell proliferation marker, was also downregulated in RCC2 knockout mice. Overall, our data show for the first time that RCC2 is an important protein for the stabilization and transcriptional activation of Sox2 and further promotion of malignancy in esophageal cancer. IMPLICATIONS: This study shows that RCC2 controls Sox2 expression and transcriptional activity to mediate esophageal cancer formation.

Inhibition of Aurora Kinase B attenuates fibroblast activation and pulmonary fibrosis

Fibroblast activation including proliferation, survival, and ECM production is central to initiation and maintenance of fibrotic lesions in idiopathic pulmonary fibrosis (IPF). However, druggable molecules that target fibroblast activation remain limited. In this study, we show that multiple pro‐fibrotic growth factors, including TGFα, CTGF, and IGF1, increase aurora kinase B (AURKB) expression and activity in fibroblasts. Mechanistically, we demonstrate that Wilms tumor 1 (WT1) is a key transcription factor that mediates TGFα‐driven AURKB upregulation in fibroblasts. Importantly, we found that inhibition of AURKB expression or activity is sufficient to attenuate fibroblast activation. We show that fibrosis induced by TGFα is highly dependent on AURKB expression and treating TGFα mice with barasertib, an AURKB inhibitor, reverses fibroblast activation, and pulmonary fibrosis. Barasertib similarly attenuated fibrosis in the bleomycin model of pulmonary fibrosis. Together, our preclinical studies provide important proof‐of‐concept that demonstrate barasertib as a possible intervention therapy for IPF.

Common and specific gene signatures among three different endometriosis subtypes

Aims

To identify the common and specific molecular mechanisms of three well-defined subtypes of endometriosis (EMs): ovarian endometriosis (OE), peritoneal endometriosis (PE), and deep infiltrating endometriosis (DIE).

Methods

Four microarray datasets: GSE7305 and GSE7307 for OE, E-MTAB-694 for PE, and GSE25628 for DIE were downloaded from public databases and conducted to compare ectopic lesions (EC) with eutopic endometrium (EU) from EMs patients. Differentially expressed genes (DEGs) identified by limma package were divided into two parts: common DEGs among three subtypes and specific DEGs in each subtype, both of which were subsequently performed with the Kyoto Encyclopedia of Genes (KEGG) pathway enrichment analysis. The protein-protein interaction (PPI) network was constructed by common DEGs and five hub genes were screened out from the PPI network. Besides, these five hub genes together with selected interested pathway-related genes were further validated in an independent OE RNA-sequencing dataset GSE105764.

Results

A total of 54 EC samples from three EMs subtypes (OE, PE, DIE) and 58 EU samples were analyzed, from which we obtained 148 common DEGs among three subtypes, and 729 specific DEGs in OE, 777 specific DEGs in PE and 36 specific DEGs in DIE. The most enriched pathway of 148 shared DEGs was arachidonic acid (AA) metabolism, in which most genes were up-regulated in EC, indicating inflammation was the most common pathogenesis of three subtypes. Besides, five hub genes AURKB, RRM2, DTL, CCNB1, CCNB2 identified from the PPI network constructed by 148 shared DEGs were all associated with cell cycle and mitosis, and down-regulated in EC, suggesting a slow and controlled proliferation in ectopic lesions. The KEGG pathway analysis of specific DEGs in each subtype revealed that abnormal ovarian steroidogenesis was a prominent feature in OE; OE and DIE seems to be at more risk of malignant development since both of their specific DEGs were enriched in the pathways in cancer, though enriched genes were different, while PE tended to be more associated with dysregulated peritoneal immune and inflammatory microenvironment.

Conclusion

By integrated bioinformatic analysis, we explored common and specific molecular signatures among different subtypes of endometriosis: activated arachidonic acid (AA) metabolism-related inflammatory process and a slow and controlled proliferation in ectopic lesions were common features in OE, PE and DIE; OE and DIE seemed to be at more risk of malignant development while PE tended to be more associated with dysregulated peritoneal immune and inflammatory microenvironment, all of which could deepen our perception of endometriosis.

Kinase Chemodiversity from the Arctic: The Breitfussins

In this work, we demonstrate that the indole-oxazole-pyrrole framework of the breitfussin family of natural products is a promising scaffold for kinase inhibition. Six new halogenated natural products, breitfussin C-H (3 - 8) were isolated and characterized from the Arctic, marine hydrozoan Thuiaria breitfussi. The structures of two of the new natural products were also confirmed by total synthesis. Two of the breitfussins (3 and 4) were found to selectively inhibit the survival of several cancer cell lines, with the lowest IC₅₀ value of 340 nM measured against the drug-resistant triple negative breast cancer cell line MDA-MB-468, while leaving the majority of the tested cell lines not or significantly less affected. When tested against panels of protein kinases, 3 gave IC₅₀ and K_d values as low as 200 and 390 nM against the PIM1 and DRAK1 kinases, respectively. The activity was confirmed to be mediated through ATP competitive binding in the ATP binding pocket of the kinases. Furthermore, evaluation of potential off-target and toxicological effects, as well as relevant in vitro ADME parameters for 3 revealed that the breitfussin scaffold holds promise for the development of selective kinase inhibitors.

Selective inhibition of Aurora A and B kinases effectively induces cell cycle arrest in t(8;21) acute myeloid leukemia

The fusion gene AML1-ETO initially dysregulates various cell cycle molecules in t(8;21) acute myeloid leukemia. Aurora kinases have shown great promise in treating tumors. However, the efficacy of Aurora kinase (AURK) A and B inhibition in t(8;21) AML remains unclear. We found that AURK-A inhibitor Alisertib and AURK-B inhibitor Barasertib strongly inhibited the growth and proliferation of t(8;21) AML cells. The quantity and size of cell colonies were markedly decreased after a 14-d drug exposure. The cell cycle distribution was blocked at the G2/M phase in both dose- and time-dependent manner. The expression of p53 family and cdc2-p34 significantly changed as well. Notably, we found that t(8;21) AML cells are more sensitive to Aurora B inhibition. In each set of experiments, Barasertib took less time or a lower concentration to achieve similar efficacy. Taken together, our data highlighted the potential role of Aurora kinases as promising cell cycle targets for the treatment of t(8;21) AML and hereby provided a theoretical basis to guide relevant clinical trials.