Aurora B Overexpression Causes Aneuploidy and p21Cip1 Repression during Tumor Development

Synthesis and antitumor activities of novel 3-(6-aminopyridin-3-yl)benzamide derivatives: Inducing cell cycle arrest and apoptosis via AURKB transcription inhibition

Here, a series of 3-(6-aminopyridin-3-yl) benzamide derivatives were designed and synthesized. Cell viability assay indicated that most compounds exhibited potent antiproliferative activity against all the tested cancer cells. Among them, compound 7l displayed the best antiproliferative activity particularly in A549 cells, with an IC50 value of 0.04 ± 0.01 μM. RNA-seq analysis was employed to explore the potential pathways related to the antiproliferative activity of compound 7l. The data revealed that 7l exerted antiproliferative activity mainly by regulating cell cycle, DNA replication and p53 signaling pathway. Indeed, compound 7l induced G2/M phase arrest by AURKB transcription inhibition and resulted in cell apoptosis via p53 signaling pathway. Most importantly, compound 7l demonstrated potent antitumor activity in A549 xenograft tumor model. Collectively, 7l might be a promising lead compound for the development of new therapeutic agents for AURKB overexpressed or mutated cancers.

AURKB promotes colorectal cancer progression by triggering the phosphorylation of histone H3 at serine 10 to activate CCNE1 expression

Aurora kinase B (AURKB) initiates the phosphorylation of serine 10 on histone H3 (pH3S10), a crucial process for chromosome condensation and cytokinesis in mammalian mitosis. Nonetheless, the precise mechanisms through which AURKB regulates the cell cycle and contributes to tumorigenesis as an oncogenic factor in colorectal cancer (CRC) remain unclear. Here, we report that AURKB was highly expressed and positively correlated with Ki-67 expression in CRC. The abundant expression of AURKB promotes the growth of CRC cells and xenograft tumors in animal model. AURKB knockdown substantially suppressed CRC proliferation and triggered cell cycle arrest in G2/M phase. Interestingly, cyclin E1 (CCNE1) was discovered as a direct downstream target of AURKB and functioned synergistically with AURKB to promote CRC cell proliferation. Mechanically, AURKB activated CCNE1 expression by triggering pH3S10 in the promoter region of CCNE1. Furthermore, it was showed that the inhibitor specific for AURKB (AZD1152) can suppress CCNE1 expression in CRC cells and inhibit tumor cell growth. To conclude, this research demonstrates that AURKB accelerated the tumorigenesis of CRC through its potential to epigenetically activate CCNE1 expression, suggesting AURKB as a promising therapeutic target in CRC.

Influence of different pH milieu on the structure and function of human Aurora kinase B protein (AURK-B): Amalgamation of both spectroscopic and computational approach

Aurora kinase B (AURK-B) is a serine/threonine kinase protein that plays an essential role in chromosomal separation during the cell cycle event. AURK-B is highly expressed in various types of cancer such as human seminoma, thyroid carcinoma, non-small cell lung carcinoma (NSCLC), oral carcinoma, and gastric cancer. Hence, it is a potential therapeutic target in the treatment of various cancers. The structure of AURK-B in complex with one of its substrate inner centromeric protein (INCENP) is present, but the structural and functional characterization of native AURK-B at different pH environment is still unexplored.This study determines the effect of different pH milieu on the structure and function of AURK-B protein wherein the influence of pH on the protein conformation was probed using Circular dichroism (CD) and fluorescence spectroscopy. The structural studies were further combined with functional activity assay to observe the change in kinase activity at various pH milieu (2.0-11.0). CD and fluorescence spectroscopy experiments dictate that at high acidic conditions (pH 2.0 - 5.0), the secondary and tertiary structures of AURK-B become distorted, leading to diminished activity. The protein, however, was observed to stabilize towards pH 7.0 - 8.0 with minimal structure alteration over the basic pH range (pH 9.0 -11.0). The measured spectroscopic structural features were found to be in-line with obtained experimental kinase activity assays. Further, in-vitro experiments indicate that the enzyme is maximally active at pH 8.0. More ordered conformation and compact structure was observed at this pH (pH 8.0) as compared to other pH values through molecular dynamics simulation studies (MDS). As AURK-B localizes itself in the intracellular compartment, this study may provide a clue about the role of different pH environments in enhancing cancer growth, proliferation, and invasion.

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.

Roles of ubiquitin‑specific protease 13 in normal physiology and tumors (Review)

Ubiquitin-specific protease 13 (USP13) is one of the most important deubiquitinases involved in various diseases. As deubiquitinases are components of the deubiquitination process, a significant post-translational modification, they are potential treatment targets for different diseases. With recent technological developments, the structure of USP13 and its pathological and physiological functions have been investigated. However, USP13 expression and function differ in various diseases, especially in tumors, and the associated mechanisms are complex and remain to be fully investigated. The present review summarized the recent discoveries and the current understanding of the USP13 function in tumors.

microRNA-486-5p Regulates DNA Damage Inhibition and Cisplatin Resistance in Lung Adenocarcinoma by Targeting AURKB

Lung adenocarcinoma (LUAD) severely affects human health, and cisplatin (DDP) resistance is the main obstacle in LUAD treatment, the mechanism of which is unknown. Bioinformatics methods were utilized to predict expression and related pathways of AURKB in LUAD tissues, as well as the upstream regulated microRNAs. qRT-PCR assayed expression of AURKB and microRNA-486-5p. RIP and dual-luciferase experiments verified the binding and interaction between the two genes. CCK-8 was used to detect cell proliferation ability and IC50 values. Flow cytometry was utilized to assess the cell cycle. Comet assay and western blot tested DNA damage and γ-H2AX protein expression, respectively. In LUAD, AURKB was upregulated, but microRNA-486-5p was downregulated. The targeted relationship between the two was confirmed by RIP and dual-luciferase experiments. Cell experiments showed that AURKB knock-down inhibited cell proliferation, reduced IC50 values, induced cell cycle arrest, and caused DNA damage. The rescue experiment presented that high expression of microRNA-486-5p could weaken the impact of AURKB overexpression on LUAD cell behavior and DDP resistance. microRNA-486-5p regulated DNA damage to inhibit DDP resistance in LUAD by targeting AURKB, implying that microRNA-486-5p/AURKB axis may be a possible therapeutic target for DDP resistance in LUAD patients.

Targeting mitotic regulators in cancer as a strategy to enhance immune recognition

Eukaryotic DNA has evolved to be enclosed within the nucleus to protect the cellular genome from autoinflammatory responses driven by the immunogenic nature of cytoplasmic DNA. Cyclic GMP-AMP Synthase (cGAS) is the cytoplasmic dsDNA sensor, which upon activation of Stimulator of Interferon Genes (STING), mediates production of pro-inflammatory interferons (IFNs) and interferon stimulated genes (ISGs). However, although this pathway is crucial in detection of viral and microbial genetic material, cytoplasmic DNA is not always of foreign origin. It is now recognised that specifically in genomic instability, a hallmark of cancer, extranuclear material in the form of micronuclei (MN) can be generated as a result of unresolved DNA lesions during mitosis. Activation of cGAS-STING in cancer has been shown to regulate numerous tumour-immune interactions such as acquisition of 'immunologically hot' phenotype which stimulates immune-mediated elimination of transformed cells. Nonetheless, a significant percentage of poorly prognostic cancers is 'immunologically cold'. As this state has been linked with low proportion of tumour-infiltrating lymphocytes (TILs), improving immunogenicity of cold tumours could be clinically relevant by exhibiting synergy with immunotherapy. This review aims to present how inhibition of vital mitotic regulators could provoke cGAS-STING response in cancer and improve the efficacy of current immunotherapy regimens.

Identifying possible hub genes and biological mechanisms shared between bladder cancer and inflammatory bowel disease using machine learning and integrated bioinformatics

BACKGROUND

Recent studies have shown that inflammatory bowel disease (IBD) is associated with bladder cancer (BC) incidence. But there is still a lack of understanding regarding its pathogenesis. Thus, this study aimed to identify potential hub genes and their important pathways and pathological mechanisms of interactions between IBD and BC using bioinformatics methods.

METHODS

The data from Gene Expression Omnibus (GEO) and the cancer genome atlas (TCGA) were analyzed to screen common differentially expressed genes (DEGs) between IBD and BC. The "clusterProfiler" package was used to analyze GO term and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment in DEGs. After that, we conducted a weighted gene co-expression network analysis (WGCNA) on these DEGs to determine the vital modules and genes significantly related to BC. Protein-protein interaction (PPI) networks was used to identify hub genes. Further, the hub genes were used to develop a prognostic signature by Cox analysis. The validity of the ten hub DEGs was tested using three classification algorithms. Finally, we analyzed the microRNAs (miRNA)-mRNA, transcription factors (TFs)-mRNA regulatory network.

RESULTS

Positive regulation of organelle fission, chromosomal region, tubulin binding, and cell cycle signaling pathway were the major enriched pathways for the common DEGs. PPI networks identified three hub proteins (AURKB, CDK1, and CCNA2) with high connectivity. Three machine-learning classification algorithms based on ten hub genes performed well for IBD and BC (accuracy > 0.80). The robust predictive model based on the ten hub genes could accurately classify BC cases with various clinical outcomes. Based on the gene-TFs and gene-miRNAs network construction, 9 TFs and 6 miRNAs were identified as potential critical TFs and miRNAs. There are 13 drugs that interact with the hub gene based on gene-drug interaction analysis.

CONCLUSIONS

This study explored common gene signatures and the potential pathogenesis of IBD and BC. We revealed that an unbalanced immune response, cell cycle pathway, and neutrophil infiltration might be the common pathogenesis of IBD and BC. Molecular mechanisms for the treatment of IBD and CC still require further investigation.

The Role of Aurora B Kinase in Normal and Cancer Cells

Aurora kinases are essential players in mammalian cell division. These kinases are involved in the regulation of spindle dynamics, microtubule-kinetochore interactions, and chromosome condensation and orientation during mitosis. At least three members of the Aurora family - Aurora kinases A, B, and C - have been identified in mammals. Aurora B is essential for maintaining genomic stability and normal cell division. Mutations and dysregulation of this kinase are implicated in tumor initiation and progression. In this review, we discuss the functions of Aurora B, the relationship between increased Aurora B activity and carcinogenesis, and the prospects for the use of Aurora B kinase inhibitors in antitumor therapy.

Combination Therapy as a Promising Way to Fight Oral Cancer

Oral cancer is a highly aggressive tumor with invasive properties that can lead to metastasis and high mortality rates. Conventional treatment strategies, such as surgery, chemotherapy, and radiation therapy, alone or in combination, are associated with significant side effects. Currently, combination therapy has become the standard practice for the treatment of locally advanced oral cancer, emerging as an effective approach in improving outcomes. In this review, we present an in-depth analysis of the current advancements in combination therapies for oral cancer. The review explores the current therapeutic options and highlights the limitations of monotherapy approaches. It then focuses on combinatorial approaches that target microtubules, as well as various signaling pathway components implicated in oral cancer progression, namely, DNA repair players, the epidermal growth factor receptor, cyclin-dependent kinases, epigenetic readers, and immune checkpoint proteins. The review discusses the rationale behind combining different agents and examines the preclinical and clinical evidence supporting the effectiveness of these combinations, emphasizing their ability to enhance treatment response and overcome drug resistance. Challenges and limitations associated with combination therapy are discussed, including potential toxicity and the need for personalized treatment approaches. A future perspective is also provided to highlight the existing challenges and possible resolutions toward the clinical translation of current oral cancer therapies.

Identification, characterization, and prognosis investigation of pivotal genes shared in different stages of breast cancer

One of the leading causes of death (20.1 per 100,000 women per year), breast cancer is the most prevalent cancer in females. Statistically, 95% of breast cancer are categorized as adenocarcinomas, and 55% of all patients may go into invasive phases; however, it can be successfully treated in approximately 70-80% of cases if diagnosed in the nascent stages. The emergence of breast tumor cells which are intensely resistant to conventional therapies, along with the high rate of metastasis occurrence, has highlighted the importance of finding novel strategies and treatments. One of the most advantageous schemes to alleviate this complication is to identify the common differentially expressed genes (DEGs) among primary and metastatic cancerous cells to use resultants for designing new therapeutic agents which are able to target both primary and metastatic breast tumor cells. In this study, the gene expression dataset with accession number GSE55715 was analyzed containing two primary tumor samples, three bone-metastatic samples, and three normal samples to distinguish the up- and down regulated genes in each stage compared to normal cells as control. In the next step, the common upregulated genes between the two experimental groups were detected by Venny online tool. Moreover, gene ontology, functions and pathways, gene-targeting microRNA, and influential metabolites were determined using EnrichR 2021 GO, KEGG pathways miRTarbase 2017, and HMDB 2021, respectively. Furthermore, elicited from STRING protein-protein interaction networks were imported to Cytoscape software to identify the hub genes. Then, identified hub genes were checked to validate the study using oncological databases. The results of the present article disclosed 1263 critical common DEGs (573 upregulated + 690 downregulated), including 35 hub genes that can be broadly used as new targets for cancer treatment and as biomarkers for cancer detection by evaluation of expression level. Besides, this study opens a new horizon to reveal unknown aspects of cancer signaling pathways by providing raw data evoked from in silico experiments. This study's outcomes can also be widely utilized in further lab research since it contains diverse information on common DEGs of varied stages and metastases of breast cancer, their functions, structures, interactions, and associations.

Interaction between Human Papillomavirus-Encoded E6 Protein and AurB Induces Cell Immortalization and Proliferation-A Potential Target of Intervention

The human papillomavirus E6 and E7 oncoproteins interact with a different subset of host proteins, leading to dysregulation of the apoptotic, cell cycle, and signaling pathways. In this study, we identified, for the first time, that Aurora kinase B (AurB) is a bona fide interacting partner of E6. We systematically characterized the AurB-E6 complex formation and its consequences in carcinogenesis using a series of in vitro and cell-based assays. We also assessed the efficacy of Aurora kinase inhibitors in halting HPV-mediated carcinogenesis using in vitro and in vivo models. We showed that AurB activity was elevated in HPV-positive cells, and this correlated positively with the E6 protein level. E6 interacted directly with AurB in the nucleus or mitotic cells. A previously unidentified region of E6, located upstream of C-terminal E6-PBM, was important for AurB-E6 complex formation. AurB-E6 complex led to reduced AurB kinase activity. However, the AurB-E6 complex increased the hTERT protein level and its telomerase activity. On the other hand, AurB inhibition led to the inhibition of telomerase activity, cell proliferation, and tumor formation, even though this may occur in an HPV-independent manner. In summary, this study dissected the molecular mechanism of how E6 recruits AurB to induce cell immortalization and proliferation, leading to the eventual cancer development. Our findings revealed that the treatment of AZD1152 exerted a non-specific anti-tumor effect. Hence, a continuous effort to seek a specific and selective inhibitor that can halt HPV-mediated carcinogenesis should be warranted.

Mechanisms of chromosomal instability (CIN) tolerance in aggressive tumors: surviving the genomic chaos

Chromosomal instability (CIN) is a pervasive feature of human cancers involved in tumor initiation and progression and which is found elevated in metastatic stages. CIN can provide survival and adaptation advantages to human cancers. However, too much of a good thing may come at a high cost for tumor cells as excessive degree of CIN-induced chromosomal aberrations can be detrimental for cancer cell survival and proliferation. Thus, aggressive tumors adapt to cope with ongoing CIN and most likely develop unique susceptibilities that can be their Achilles' heel. Determining the differences between the tumor-promoting and tumor-suppressing effects of CIN at the molecular level has become one of the most exciting and challenging aspects in cancer biology. In this review, we summarized the state of knowledge regarding the mechanisms reported to contribute to the adaptation and perpetuation of aggressive tumor cells carrying CIN. The use of genomics, molecular biology, and imaging techniques is significantly enhancing the understanding of the intricate mechanisms involved in the generation of and adaptation to CIN in experimental models and patients, which were not possible to observe decades ago. The current and future research opportunities provided by these advanced techniques will facilitate the repositioning of CIN exploitation as a feasible therapeutic opportunity and valuable biomarker for several types of human cancers.

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.

Drugging Hijacked Kinase Pathways in Pediatric Oncology: Opportunities and Current Scenario

Childhood cancer is considered rare, corresponding to ~3% of all malignant neoplasms in the human population. The World Health Organization (WHO) reports a universal occurrence of more than 15 cases per 100,000 inhabitants around the globe, and despite improvements in diagnosis, treatment and supportive care, one child dies of cancer every 3 min. Consequently, more efficient, selective and affordable therapeutics are still needed in order to improve outcomes and avoid long-term sequelae. Alterations in kinases' functionality is a trademark of cancer and the concept of exploiting them as drug targets has burgeoned in academia and in the pharmaceutical industry of the 21st century. Consequently, an increasing plethora of inhibitors has emerged. In the present study, the expression patterns of a selected group of kinases (including tyrosine receptors, members of the PI3K/AKT/mTOR and MAPK pathways, coordinators of cell cycle progression, and chromosome segregation) and their correlation with clinical outcomes in pediatric solid tumors were accessed through the R2: Genomics Analysis and Visualization Platform and by a thorough search of published literature. To further illustrate the importance of kinase dysregulation in the pathophysiology of pediatric cancer, we analyzed the vulnerability of different cancer cell lines against their inhibition through the Cancer Dependency Map portal, and performed a search for kinase-targeted compounds with approval and clinical applicability through the CanSAR knowledgebase. Finally, we provide a detailed literature review of a considerable set of small molecules that mitigate kinase activity under experimental testing and clinical trials for the treatment of pediatric tumors, while discuss critical challenges that must be overcome before translation into clinical options, including the absence of compounds designed specifically for childhood tumors which often show differential mutational burdens, intrinsic and acquired resistance, lack of selectivity and adverse effects on a growing organism.

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.

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.

Increased Aurora B expression reduces substrate phosphorylation and induces chromosomal instability

Increased Aurora B protein expression, which is common in cancers, is expected to increase Aurora B kinase activity, yielding elevated phosphorylation of Aurora B substrates. In contrast, here we show that elevated expression of Aurora B reduces phosphorylation of six different Aurora B substrates across three species and causes defects consistent with Aurora B inhibition. Complexes of Aurora B and its binding partner INCENP autophosphorylate in trans to achieve full Aurora B activation. Increased expression of Aurora B mislocalizes INCENP, reducing the local concentration of Aurora B:INCENP complexes at the inner centromere/kinetochore. Co-expression of INCENP rescues Aurora B kinase activity and mitotic defects caused by elevated Aurora B. However, INCENP expression is not elevated in concert with Aurora B in breast cancer, and increased expression of Aurora B causes resistance rather than hypersensitivity to Aurora B inhibitors. Thus, increased Aurora B expression reduces, rather than increases, Aurora B kinase activity.

Comprehensive analysis identifies as a critical prognostic prediction gene in breast cancer

BACKGROUND

Aurora kinases (AURKs) family plays a vital role not only in cell division but also in tumorigenesis. However, there are still rare systematic analyses of the diverse expression patterns and prognostic value of the AURKs family in breast cancer (BC). Systematic bioinformatics analysis was conducted to explore the biological role, prognostic value, and immunologic function of AURKs family in BC.

METHODS

The expression, prognostic value, and clinical functions of AURKs family in BC were evaluated with several bioinformatics web portals: ONCOMINE Gene Expression Profiling Interactive Analysis, Kaplan-Meier plotter, cBioPortal, Metascape, GeneMANIA, and LinkedOmics; and the result was verified using human tissues.

RESULTS

The expression of AURKA and AURKB were upregulated in BC in subgroup analyses based on tumor stage (all P   <  0.05). BC patients with high AURKA and AURKB expression had a worse overall survival, relapse-free survival, and distant metastasis-free survival (all P   <  0.05). Verification experiment revealed that AURKA and AURKB were upregulated in BC ( P  < 0.05). AURKA and AURKB were specifically associated with several tumor-associated kinases (polo-like kinase 1 and cyclin-dependent kinase 1), miRNAs (miR-507 and miR-381), and E2F transcription factor 1. Moreover, AURKA and AURKB were correlated with immune cell infiltration. Functional enrichment analysis revealed that AURKA and AURKB were involved in the cell cycle signaling pathway, platinum drug resistance signaling pathway, ErbB signaling pathway, Hippo signaling pathway, and nucleotide-binding and oligomerization domain-like receptor signaling pathway.

CONCLUSIONS

Aurora kinases AURKA and AURKB could be employed as novel prognostic biomarkers or promising therapeutic targets for BC.

Cohesin in DNA damage response and double-strand break repair

Cohesin, a four-subunit ring comprising SMC1, SMC3, RAD21 and SA1/2, tethers sister chromatids by DNA replication-coupled cohesion (RC-cohesion) to guarantee correct chromosome segregation during cell proliferation. Postreplicative cohesion, also called damage-induced cohesion (DI-cohesion), is an emerging critical player in DNA damage response (DDR). In this review, we sum up recent progress on how cohesin regulates the DNA damage checkpoint activation and repair pathway choice, emphasizing postreplicative cohesin loading and DI-cohesion establishment in yeasts and mammals. DI-cohesion and RC-cohesion show distinct features in many aspects. DI-cohesion near or far from the break sites might undergo different regulations and execute different tasks in DDR and DSB repair. Furthermore, some open questions in this field and the significance of this new scenario to our understanding of genome stability maintenance and cohesinopathies are discussed.

Clinical outcomes associated with expression of aurora kinase and p53 family members in muscle‑invasive bladder cancer

Biomarkers are needed in muscle-invasive bladder cancer (MIBC). We previously reported that high tumor aurora kinase (AURK) A expression identifies patients with MIBC with poor prognosis. Aberrant p53 expression has also been associated with poor outcomes in MIBC, though to the best of our knowledge, co-expression rates of p53 and aurora kinases have not been previously described in MIBC. As aurora kinase and p53 family members may co-regulate each other, the present study investigated whether tumor p53 or p63 protein expression influenced the prognostic value of AURKA in a pilot study of 50 patients with MIBC treated with curative intent. Immunohistochemistry for AURKA, AURKB, p53 and p63 were performed on archival pre-treatment tumor specimens and correlated with clinical outcomes in patients with MIBC who received neoadjuvant chemotherapy (NAC) prior to cystectomy. Baseline p53 [hazard ratio (HR) 1.46; 95% confidence interval (CI)=0.55-3.9; P=0.448) and p63 (HR 2.02; 95% CI=0.51-8.1; P=0.313) protein expression did not predict for overall survival (OS). Low p53 protein expression did not correlate with high AURKA (φ=0.190) or AURKB (φ=0.075) expression. However, in tumors with low p53 expression (n=17), the presence of either high AURKA or AURKB expression levels predicted an increased risk for relapse (HR 27.1; 95% CI=2.7-270.1; P=0.005) and mortality (HR 14.9; 95% CI=2.3-95.6; P=0.004) compared to tumors with both low AURKA and AURKB levels. The relationship between p63 and AURKA/B expression levels was not tested due to the prevalence (80%) of high p63 expression in the present cohort. In tumors with low AURKA expression, p53 status did not predict for OS (HR 0.62; 95% CI 0.2-3.2; P=0.572). In multivariable analysis, only high baseline AURKA expression predicted for inferior OS (HR 4.9; 95% CI 1.7-14.1; P=0.003). To the best of our knowledge, the present study was the first to report co-expression of p53 and aurora kinase family members in MIBC, and although wild-type p53 may regulate the aurora kinases in preclinical models, the adverse prognostic value of tumor AURKA overexpression was independent from baseline tumor p53 protein expression in the present cohort. AURKA remains an important prognostic biomarker in patients with MIBC and warrants further evaluation in prospective studies to validate whether baseline AURKA can identify patients that are unlikely to benefit from standard of care with NAC.

Identification of key regulators associated with colon cancer prognosis and pathogenesis

Colon cancer (CC) is the fourth deadliest cancer in the world. New insights into prognostication might be helpful to define the optimal adjuvant treatments for patients in routine clinical practice. Here, a microarray dataset with 30 primary tumors and 30 normal samples was analyzed using GEO2R to find differentially expressed genes (DEGs). Then, DAVID, KEGG, ChEA and X2K were used to analyze DEGs-related Gene Ontology, pathways, transcription factors (TFs) and kinases, respectively. Protein-protein interaction (PPI) networks were constructed using the STRING database and Cytoscape. The modules and hub genes of DEGs was determined through MCODE and CytoHubba plugins, and the expression of hub genes was verified using GEPIA. To find microRNAs and metabolites associated with DEGs, miRTarBase and HMDB were used, respectively. It was found that 233 and 373 genes were upregulated and downregulated in CC, respectively. GO analysis showed that the upregulated DEGs were mainly involved in mitotic nuclear division and cell division. Top 10 hub genes were identified, including AURKB, CDK1, DLGAP5, AURKA, CCNB2, CCNB1, BUB1B, CCNA2, KIF20A and BUB1. Whereas, FOMX1, E2F7, E2F1, E2F4 and AR were identified as top 5 TFs in CC. Moreover, CDK1, CDC2, MAPK14, ATM and CK2ALPHA was identified as top 5 kinases in CC. miRNAs analysis showed that Hsa-miR-215-5p hsa-miR-193b-3p, hsa-miR-192-5p and hsa-miR-16-5p could target the largest number of CC genes. Taken together, CC-related genes, especially the hub genes, TFs, and metabolites might be used as novel biomarkers for CC, as well as for diagnosis and guiding therapeutic strategies for CC.

Aurora Kinases as Therapeutic Targets in Head and Neck Cancer

ABSTRACT

The Aurora kinases (AURKA and AURKB) have attracted attention as therapeutic targets in head and neck squamous cell carcinomas. Aurora kinases were first defined as regulators of mitosis that localization to the centrosome (AURKA) and centromere (AURKB), governing formation of the mitotic spindle, chromatin condensation, activation of the core mitotic kinase CDK1, alignment of chromosomes at metaphase, and other processes. Subsequently, additional roles for Aurora kinases have been defined in other phases of cell cycle, including regulation of ciliary disassembly and DNA replication. In cancer, elevated expression and activity of Aurora kinases result in enhanced or neomorphic locations and functions that promote aggressive disease, including promotion of MYC expression, oncogenic signaling, stem cell identity, epithelial-mesenchymal transition, and drug resistance. Numerous Aurora-targeted inhibitors have been developed and are being assessed in preclinical and clinical trials, with the goal of improving head and neck squamous cell carcinoma treatment.

Mitotic and DNA Damage Response Proteins: Maintaining the Genome Stability and Working for the Common Good

Cellular function is highly dependent on genomic stability, which is mainly ensured by two cellular mechanisms: the DNA damage response (DDR) and the Spindle Assembly Checkpoint (SAC). The former provides the repair of damaged DNA, and the latter ensures correct chromosome segregation. This review focuses on recently emerging data indicating that the SAC and the DDR proteins function together throughout the cell cycle, suggesting crosstalk between both checkpoints to maintain genome stability.

CDK4 has the ability to regulate Aurora B and Cenpp expression in mouse keratinocytes

Cyclin-dependent kinase 4 (CDK4) is a critical molecule that regulates key aspects of cell proliferation through phosphorylation of the retinoblastoma (Rb) family of proteins. In the last few years, it has been suggested that CDK4 plays alternative roles in cell proliferation and tumorigenesis. The main aim of the present study was to define a novel CDK4 function as a transcriptional regulator of genes involved in chromosome segregation, contributing to the G2/M phase transition. Herein, chromatin-immunoprecipitation reverse transcription-quantitative PCR assays were performed to demonstrate that CDK4 could occupy the promoter region of genes associated with chromosomal segregation, such as Aurora-B (Aurkb) and Centromere Protein P (CENP-P). Moreover, gain- and loss-of-function experiments showed that CDK4 participated in the transcriptional regulation of Aurkb and CENP-P. The finding that Aurkb may have a crucial role in chromosome bi-orientation and the spindle assembly checkpoint, and that CENP-P could be required for proper kinetochore function suggests that dysregulation of CDK4 expression induces chromosomal instability and, in some cases, cancer development.

Human RecQL4 as a Novel Molecular Target for Cancer Therapy

Human RecQ helicases play diverse roles in the maintenance of genomic stability. Inactivating mutations in 3 of the 5 human RecQ helicases are responsible for the pathogenesis of Werner syndrome (WS), Bloom syndrome (BS), Rothmund-Thomson syndrome (RTS), RAPADILINO, and Baller-Gerold syndrome (BGS). WS, BS, and RTS patients are at increased risk for developing many age-associated diseases including cancer. Mutations in RecQL1 and RecQL5 have not yet been associated with any human diseases so far. In terms of disease outcome, RecQL4 deserves special attention because mutations in RecQL4 result in 3 autosomal recessive syndromes (RTS type II, RAPADILINO, and BGS). RecQL4, like other human RecQ helicases, has been demonstrated to play a crucial role in the maintenance of genomic stability through participation in diverse DNA metabolic activities. Increased incidence of osteosarcoma in RecQL4-mutated RTS patients and elevated expression of RecQL4 in sporadic cancers including osteosarcoma suggest that loss or gain of RecQL4 expression is linked with cancer susceptibility. In this review, current and future perspectives are discussed on the potential use of RecQL4 as a novel cancer therapeutic target.

Genetic variations in AURORA cell cycle kinases are associated with glioblastoma multiforme

Glioblastoma multiforme (GBM) is the most frequent type of primary astrocytomas. We examined the association between single nucleotide polymorphisms (SNPs) in Aurora kinase A (AURKA), Aurora kinase B (AURKB), Aurora kinase C (AURKC) and Polo-like kinase 1 (PLK1) mitotic checkpoint genes and GBM risk by qPCR genotyping. In silico analysis was performed to evaluate effects of polymorphic biological sequences on protein binding motifs. Chi-square and Fisher statistics revealed a significant difference in genotypes frequencies between GBM patients and controls for AURKB rs2289590 variant (p = 0.038). Association with decreased GBM risk was demonstrated for AURKB rs2289590 AC genotype (OR = 0.54; 95% CI = 0.33-0.88; p = 0.015). Furthermore, AURKC rs11084490 CG genotype was associated with lower GBM risk (OR = 0.57; 95% CI = 0.34-0.95; p = 0.031). Bioinformatic analysis of rs2289590 polymorphic region identified additional binding site for the Yin-Yang 1 (YY1) transcription factor in the presence of C allele. Our results indicated that rs2289590 in AURKB and rs11084490 in AURKC were associated with a reduced GBM risk. The present study was performed on a less numerous but ethnically homogeneous population. Hence, future investigations in larger and multiethnic groups are needed to strengthen these results.

Aurora kinases in ovarian cancer

Aurora kinases (AURK) are key regulators of the mitotic spindle formation. AURK is frequently overexpressed in ovarian cancer and this overexpression has been frequently associated with prognosis in these tumours. Interestingly, AURK have been shown to interact with DNA repair mechanisms and other cell cycle regulators. These functions have brought light to Aurora family as a potential target for anticancer therapy. In the last years, two clinical trials with different AURK inhibitors have shown activity in epithelial and clear-cell ovarian cancer. Although there is a lack of predictive factors of AURK inhibition activity, recent trials have identified some candidates. This review will focus in the functions of the AURK family, its role as prognostic factor in epithelial ovarian cancer and potential clinical implications.

A precisely adjustable, variation-suppressed eukaryotic transcriptional controller to enable genetic discovery

Conditional expression of genes and observation of phenotype remain central to biological discovery. Current methods enable either on/off or imprecisely controlled graded gene expression. We developed a 'well-tempered' controller, WTC₈₄₆, for precisely adjustable, graded, growth condition independent expression of genes in Saccharomyces cerevisiae. Controlled genes are expressed from a strong semisynthetic promoter repressed by the prokaryotic TetR, which also represses its own synthesis; with basal expression abolished by a second, 'zeroing' repressor. The autorepression loop lowers cell-to-cell variation while enabling precise adjustment of protein expression by a chemical inducer. WTC₈₄₆ allelic strains in which the controller replaced the native promoters recapitulated known null phenotypes (CDC42, TPI1), exhibited novel overexpression phenotypes (IPL1), showed protein dosage-dependent growth rates and morphological phenotypes (CDC28, TOR2, PMA1 and the hitherto uncharacterized PBR1), and enabled cell cycle synchronization (CDC20). WTC₈₄₆ defines an 'expression clamp' allowing protein dosage to be adjusted by the experimenter across the range of cellular protein abundances, with limited variation around the setpoint.

Aurora-B phosphorylates the myosin II heavy chain to promote cytokinesis

Cytokinesis, the final step of mitosis, is mediated by an actomyosin contractile ring, the formation of which is temporally and spatially regulated following anaphase onset. Aurora-B is a member of the chromosomal passenger complex, which regulates various processes during mitosis; it is not understood, however, how Aurora-B is involved in cytokinesis. Here, we show that Aurora-B and myosin-IIB form a complex in vivo during telophase. Aurora-B phosphorylates the myosin-IIB rod domain at threonine 1847 (T¹⁸⁴⁷), abrogating the ability of myosin-IIB monomers to form filaments. Furthermore, phosphorylation of myosin-IIB filaments by Aurora-B also promotes filament disassembly. We show that myosin-IIB possessing a phosphomimetic mutation at T¹⁸⁴⁷ was unable to rescue cytokinesis failure caused by myosin-IIB depletion. Cells expressing a phosphoresistant mutation at T¹⁸⁴⁷ had significantly longer intercellular bridges, implying that Aurora-B-mediated phosphorylation of myosin-IIB is important for abscission. We propose that myosin-IIB is a substrate of Aurora-B and reveal a new mechanism of myosin-IIB regulation by Aurora-B in the late stages of mitosis.

Clonal selection of stable aneuploidies in progenitor cells drives high-prevalence tumorigenesis

In this study Trakala et al. investigated how chromosome gains and losses, which are a frequent feature of human cancers, can overcome the detrimental effects of aneuploidy. They developed a novel mouse model that enables unprecedented levels of chromosome missegregation in the adult animal and their results show that the initial detrimental effects of random missegregation are outweighed by clonal selection, which is dependent on chromosomal location and the nature of specific genes and is sufficient to drive cancer.

Chromosome gains and losses are a frequent feature of human cancers. However, how these aberrations can outweigh the detrimental effects of aneuploidy remains unclear. An initial comparison of existing chromosomal instability (CIN) mouse models suggests that aneuploidy accumulates to low levels in these animals. We therefore developed a novel mouse model that enables unprecedented levels of chromosome missegregation in the adult animal. At the earliest stages of T-cell development, cells with random chromosome gains and/or losses are selected against, but CIN eventually results in the expansion of progenitors with clonal chromosomal imbalances. Clonal selection leads to the development of T-cell lymphomas with stereotypic karyotypes in which chromosome 15, containing the Myc oncogene, is gained with high prevalence. Expressing human MYC from chromosome 6 (MYC^Chr6) is sufficient to change the karyotype of these lymphomas to include universal chromosome 6 gains. Interestingly, while chromosome 15 is still gained in MYC^Chr6 tumors after genetic ablation of the endogenous Myc locus, this chromosome is not efficiently gained after deletion of one copy of Rad21, suggesting a synergistic effect of both MYC and RAD21 in driving chromosome 15 gains. Our results show that the initial detrimental effects of random missegregation are outbalanced by clonal selection, which is dictated by the chromosomal location and nature of certain genes and is sufficient to drive cancer with high prevalence.

Effect of the HDAC Inhibitor on Histone Acetylation and Methyltransferases in A2780 Ovarian Cancer Cells

Background andObjective: Epigenetic modifications are believed to play a significant role in the development of cancer progression, growth, differentiation, and cell death. One of the most popular histone deacetylases inhibitors (HDACIs), suberoylanilide hydroxamic acid (SAHA), also known as Vorinostat, can directly activate p21^WAF1/CIP1 gene transcription through hyperacetylation of histones by a p53 independent mechanism. In the present investigation, we evaluated the correlation between histone modifications and DNA methyltransferase enzyme levels following SAHA treatments in A2780 ovarian cancer cells. Materials and Methods: Acetylation of histones and methyltransferases levels were analyzed using RT² profiler PCR array, immunoblotting, and immunofluorescence methods in 2D and 3D cell culture systems. Results: The inhibition of histone deacetylases (HDAC) activities by SAHA can reduce DNA methyl transferases / histone methyl transferases (DNMTs/HMTs) levels through induction of hyperacetylation of histones. Immunofluorescence analysis of cells growing in monolayers and spheroids revealed significant up-regulation of histone acetylation preceding the above-described changes. Conclusions: Our results depict an interesting interplay between histone hyperacetylation and a decrease in methyltransferase levels in ovarian cancer cells, which may have a positive impact on the overall outcomes of cancer treatment.

Long non-coding RNA NORAD upregulation induced by airborne particulate matter (PM10) exposure leads to aneuploidy in A549 lung cells

Air pollution is a worldwide problem that affects human health predominantly in the largest cities. Particulate matter of 10 μm or less in diameter (PM₁₀) is considered a risk factor for multiple diseases, including lung cancer. The long non-coding RNA NORAD and the components of the spindle assembly checkpoint (SAC) ensure proper chromosomal segregation. Alterations in the SAC cause aneuploidy, a feature associated with carcinogenesis. In this study, we demonstrated that PM₁₀ treatment increased the expression levels of NORAD as well as those of SAC components mitotic arrest deficient 1 (MAD1L1), mitotic arrest deficient 2 (MAD2L1), BubR1 (BUB1B), aurora B (AURKB), and survivin (BIRC5) in the lung A549 cell line. We also demonstrated that MAD1L1, MAD2L1, and BUB1B expression levels were reduced when cells were transfected with small interfering RNAs (siRNAs) against NORAD. Interestingly, the expression levels of AURKB and BIRC5 (survivin) were not affected by transfection with NORAD siRNAs. Cells treated with PM₁₀ exhibited a decrease in mitotic arrest and an increase in micronuclei frequency in synchronized A549 cells. PM₁₀ exposure induced aneuploidy events as a result of SAC deregulation. We also observed a reduction in the protein levels of Pumilio 1 after PM₁₀ treatment. Our results provide novel clues regarding the effect of PM₁₀ in the generation of chromosomal instability, a phenotype observed in lung cancer cells.

Aurora Kinase B Expression, Its Regulation and Therapeutic Targeting in Human Retinoblastoma

Purpose

Aurora kinase B (AURKB) plays a pivotal role in the regulation of mitosis and is gaining prominence as a therapeutic target in cancers; however, the role of AURKB in retinoblastoma (RB) has not been studied. The purpose of this study was to determine if AURKB plays a role in RB, how its expression is regulated, and whether it could be specifically targeted.

Methods

The protein expression of AURKB was determined using immunohistochemistry in human RB patient specimens and immunoblotting in cell lines. Pharmacological inhibition and shRNA-mediated knockdown were used to understand the role of AURKB in cell viability, apoptosis, and cell cycle distribution. Cell viability in response to AURKB inhibition was also assessed in enucleated RB specimens. Immunoblotting was employed to determine the protein levels of phospho-histone H3, p53, p21, and MYCN. Chromatin immunoprecipitation-qPCR was performed to verify the binding of MYCN on the promoter region of AURKB.

Results

The expression of AURKB was found to be markedly elevated in human RB tissues, and the overexpression significantly correlated with optic nerve and anterior chamber invasion. Targeting AURKB with small-molecule inhibitors and shRNAs resulted in reduced cell survival and increased apoptosis and cell cycle arrest at the G2/M phase. More importantly, primary RB specimens showed decreased cell viability in response to pharmacological AURKB inhibition. Additional studies have demonstrated that the MYCN oncogene regulates the expression of AURKB in RB.

Conclusions

AURKB is overexpressed in RB, and targeting it could serve as a novel therapeutic strategy to restrict tumor cell growth.

Potential Therapeutic Targets of Quercetin, a Plant Flavonol, and Its Role in the Therapy of Various Types of Cancer through the Modulation of Various Cell Signaling Pathways

Polyphenolic flavonoids are considered natural, non-toxic chemopreventers, which are most commonly derived from plants, fruits, and vegetables. Most of these polyphenolics exhibit remarkable antioxidant, anti-inflammatory, and anticancer properties. Quercetin (Qu) is a chief representative of these polyphenolic compounds, which exhibits excellent antioxidant and anticancer potential, and has attracted the attention of researchers working in the area of cancer biology. Qu can regulate numerous tumor-related activities, such as oxidative stress, angiogenesis, cell cycle, tumor necrosis factor, proliferation, apoptosis, and metastasis. The anticancer properties of Qu mainly occur through the modulation of vascular endothelial growth factor (VEGF), apoptosis, phosphatidyl inositol-3-kinase (P13K)/Akt (proteinase-kinase B)/mTOR (mammalian target of rapamycin), MAPK (mitogen activated protein kinase)/ERK1/2 (extracellular signal-regulated kinase 1/2), and Wnt/β-catenin signaling pathways. The anticancer potential of Qu is documented in numerous in vivo and in vitro studies, involving several animal models and cell lines. Remarkably, this phytochemical possesses toxic activities against cancerous cells only, with limited toxic effects on normal cells. In this review, we present extensive research investigations aimed to discuss the therapeutic potential of Qu in the management of different types of cancers. The anticancer potential of Qu is specifically discussed by focusing its ability to target specific molecular signaling, such as p53, epidermal growth factor receptor (EGFR), VEGF, signal transducer and activator of transcription (STAT), PI3K/Akt, and nuclear factor kappa B (NF-κB) pathways. The anticancer potential of Qu has gained remarkable interest, but the exact mechanism of its action remains unclear. However, this natural compound has great pharmacological potential; it is now believed to be a complementary—or alternative—medicine for the prevention and treatment of different cancers.

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.

Aurora-B knockdown inhibits osteosarcoma metastasis by inducing autophagy via the mTOR/ULK1 pathway

Background

Autophagy plays an essential role in metastasis of malignancies. Although our studies showed that Aurora-B facilitate pulmonary metastasis in OS, the mechanism of Aurora-B kinase on autophagy and metastasis in OS has not been explored.

Methods

Clinical-pathological parameters and follow-up information was collected in OS patients. Immunohistochemical staining was performed to detect Aurora-B and LC3 protein in OS tissues. Short hairpin RNA transfection was used to silence Aurora-B in OS cells. Real-time quantitative PCR (RT-qPCR) was performed to detect Aurora-B mRNA expression in OS cells. Aurora-B and autophagy related protein were measured by Western blot. Transmission electron microscopy and laser scanning confocal microscopy were performed to observe the formation of autophagosomes and autolysosomes. Migratory and invasive ability of OS cells were measured by Wound healing and transwell assays. Orthotopic xenograft model was used to evaluate the effect of autophagy mediated by Aurora-B inhibition on pulmonary metastasis of OS.

Results

The elevated expression of Aurora-B protein in OS tissues negatively associated with the overall survival of OS patients. Further investigation has found that Aurora-B expression was negatively correlative with autophagy related protein LC3 in OS patient tissues. Knockdown Aurora-B stimulates autophagy and inhibits migratory and invasive ability of OS cells. Mechanistically, Aurora-B knockdown suppressed the mTOR/ULK1 signaling pathway and reactivation of the mTOR/ULK1 pathway decreased autophagy level. Furthermore, the inhibition effect of silencing Aurora-B on migration and invasion of OS was reversed by chloroquine and mTOR activator in vitro and vivo.

Conclusions

Our results suggest that silencing of Aurora-B stimulate autophagy via decreasing mTOR/ULK1 and result in inhibiting OS metastasis. Targeted Aurora-B/mTOR/ULK1 pathway may be a promising treatment strategy for OS patients.

Targeting DNA damage response kinases in cancer therapy

Cancer cells die when their decimated DNA damage response (DDR) unsuccessfully handles DNA damage. This notion has been successfully exploited when targeting PARP (poly ADP-ribose polymerase) in homologous recombination-deficient cells. With the greater understanding of DDR achieved in the last decade, new cancer therapy targets within the DDR network have been identified. Intriguingly, many of the molecules that have advanced into clinical trials are inhibitors of DDR kinases. This special issue is devoted to discussing the mechanism of cell killing and the level of success that such inhibitors have reached in pre-clinical and clinical settings.

Targeting DNA Repair, Cell Cycle, and Tumor Microenvironment in B Cell Lymphoma

The DNA double-strand break (DSB) is the most cytotoxic lesion and compromises genome stability. In an attempt to efficiently repair DSBs, cells activate ATM kinase, which orchestrates the DNA damage response (DDR) by activating cell cycle checkpoints and initiating DSB repair pathways. In physiological B cell development, however, programmed DSBs are generated as intermediates for effective immune responses and the maintenance of genomic integrity. Disturbances of these pathways are at the heart of B cell lymphomagenesis. Here, we review the role of DNA repair and cell cycle control on B cell development and lymphomagenesis. In addition, we highlight the intricate relationship between the DDR and the tumor microenvironment (TME). Lastly, we provide a clinical perspective by highlighting treatment possibilities of defective DDR signaling and the TME in mantle cell lymphoma, which serves as a blueprint for B cell lymphomas.

Inhibition of AURKB, regulated by pseudogene MTND4P12, confers synthetic lethality to PARP inhibition in skin cutaneous melanoma

Despite significant advances, skin cutaneous melanoma (SKCM) is a common life-threatening cancer worldwide. Recently, pseudogenes have been discovered to be functional in many physiological processes and the pathogenesis of various diseases, including cancer. However, their relevance to SKCM remains largely unknown. In this study, seven upregulated pseudogenes were identified based on TCGA data. Among them, MTND4P12 was negatively correlated with the overall survival of SKCM patients. After constructing a pseudogene-miRNA-mRNA regulatory network, MTND4P12 was found to regulate the expression of oncogene AURKB by serving as a ceRNA. Both genetic and chemical inhibition of AURKB reduced viability and induced apoptosis of melanoma cells. Interestingly, DNA repair pathway seems to be involved in the anti-tumor effect of AURKB inhibition. Indeed, a synergistic therapeutic effect of AURKB inhibition and PARP inhibitor was confirmed both in vitro and in vivo. In conclusion, AURKB plays an oncogenic role and is a novel therapeutic target in SKCM. The combination of AURKB inhibition and PARP inhibitor has a synergistic effect, representing a promising treatment for SKCM.

USP13 controls the stability of Aurora B impacting progression through the cell cycle

Aurora B kinase plays essential roles in mitosis. Its protein levels increase before the onset of mitosis and sharply decrease during mitosis exit. The latter decrease is due to a balance between the actions of the E3 ubiquitin ligase anaphase-promoting complex or cyclosome (activated by the Cdh1 adapter), and the deubiquitinating enzyme USP35. Aurora B also executes important functions in interphase. Abnormal modulation of Aurora B in interphase leads to cell cycle defects often linked to aberrant chromosomal condensation and segregation. Very little is however known about how Aurora B levels are regulated in interphase. Here we found that USP13-associates with and stabilizes Aurora B in cells, especially before their entry into mitosis. In order for USP13 to exert its stabilizing effect on Aurora B, their association is promoted by the Aurora B-mediated phosphorylation of USP13 at Serine 114. We also present evidence that USP13 instigates Aurora B deubiquitination and/or protect it from degradation in a non-catalytic manner. In addition, we report that genetic or chemical modulation of the cellular levels/activity of USP13 affects unperturbed cell-cycle progression. Overall our study unveils the molecular and cellular connections of the USP13-Aurora B axis, which potentially participates in the rewiring of the cell cycle happening in cancer cells.

A New Inhibitor of Tubulin Polymerization Kills Multiple Cancer Cell Types and Reveals p21-Mediated Mechanism Determining Cell Death after Mitotic Catastrophe

Induction of mitotic catastrophe through the disruption of microtubules is an established target in cancer therapy. However, the molecular mechanisms determining the mitotic catastrophe and the following apoptotic or non-apoptotic cell death remain poorly understood. Moreover, many existing drugs targeting tubulin, such as vincristine, have reduced efficacy, resulting from poor solubility in physiological conditions. Here, we introduce a novel small molecule 2-aminoimidazoline derivative—OAT-449, a synthetic water-soluble tubulin inhibitor. OAT-449 in a concentration range from 6 to 30 nM causes cell death of eight different cancer cell lines in vitro, and significantly inhibits tumor development in such xenograft models as HT-29 (colorectal adenocarcinoma) and SK-N-MC (neuroepithelioma) in vivo. Mechanistic studies showed that OAT-449, like vincristine, inhibited tubulin polymerization and induced profound multi-nucleation and mitotic catastrophe in cancer cells. HeLa and HT-29 cells within 24 h of treatment arrested in G2/M cell cycle phase, presenting mitotic catastrophe features, and 24 h later died by non-apoptotic cell death. In HT-29 cells, both agents altered phosphorylation status of Cdk1 and of spindle assembly checkpoint proteins NuMa and Aurora B, while G2/M arrest and apoptosis blocking was consistent with p53-independent accumulation in the nucleus and largely in the cytoplasm of p21/waf1/cip1, a key determinant of cell fate programs. This is the first common mechanism for the two microtubule-dissociating agents, vincristine and OAT-449, determining the cell death pathway following mitotic catastrophe demonstrated in HT-29 cells.

Aurora kinases and DNA damage response

It is well established that Aurora kinases perform critical functions during mitosis. It has become increasingly clear that the Aurora kinases also perform a myriad of non-mitotic functions including DNA damage response. The available evidence indicates that inhibition Aurora kinase A (AURKA) may contribute to the G₂ DNA damage checkpoint through AURKA's functions in PLK1 and CDC25B activation. Both AURKA and Aurora kinase B (AURKB) are also essential in mitotic DNA damage response that guard against DNA damage-induced chromosome segregation errors, including the control of abscission checkpoint and prevention of micronuclei formation. Dysregulation of Aurora kinases can trigger DNA damage in mitosis that is sensed in the subsequent G₁ by a p53-dependent postmitotic checkpoint. Aurora kinases are themselves linked to the G₁ DNA damage checkpoint through p53 and p73 pathways. Finally, several lines of evidence provide a connection between Aurora kinases and DNA repair and apoptotic pathways. Although more studies are required to provide a comprehensive picture of how cells respond to DNA damage, these findings indicate that both AURKA and AURKB are inextricably linked to pathways guarding against DNA damage. They also provide a rationale to support more detailed studies on the synergism between small-molecule inhibitors against Aurora kinases and DNA-damaging agents in cancer therapies.

Aurora-B Promotes Osteosarcoma Cell Growth and Metastasis Through Activation of the NPM1/ERK/NF-κβ/MMPs Axis

Purpose

Osteosarcoma (OS) is the most common primary malignant tumor of the bone in young adolescents and children. We explored the underlying mechanism of Aurora-B in promoting OS cell proliferation and metastasis.

Patient and Methods

Bioinformatics was employed to predict the substrate of Aurora-B. IHC and Western blot were used to confirm the correlation between Aurora-B and NPM1. ERK/NF-κβ pathway-related proteins were detected by Western blot and immunofluorescence (IF). CCK8, wound healing, transwell, and Tunel assays were used to identify the cell proliferation, migration and apoptosis potential. Spontaneous metastasis xenografts were established to confirm the role of Aurora-B and NPM1.

Results

Aurora-B promotes NPM1 phosphorylation on Ser125. The phosphorylation of NPM1^Ser125 induced by Aurora-B activates the ERK/NF-κβ signaling. Further study revealed that Aurora-B promotes proliferation, migration and inhibits apoptosis via phosphorylating NPM1 in vitro and in vivo.

Conclusion

Aurora-B promotes OS malignancy via phosphorylating NPM1^Ser125 and activating ERK/NF-κβ signaling.

Viral-Mediated AURKB Cleavage Promotes Cell Segregation and Tumorigenesis

Aurora kinase B (AURKB), a central regulator of chromosome segregation and cytokinesis, is aberrantly expressed in various cancer cells. However, the relationship of AURKB and oncogenic viruses in cancer progression remains unclear. Here, we reveal that N-cleaved isoforms of AURKB exist in several oncovirus-associated tumor cells and patient cancer tissues, including Kaposi's sarcoma-associated herpesvirus (KSHV), Epstein-Barr virus (EBV), and human papillomavirus virus (HPV). Mechanistically, in KSHV-infected tumor cells, the latent viral antigen LANA cleaves AURKB at Asp⁷⁶ in a serine protease-dependent manner. The N'-AURKB relocalizes to the spindle pole and promotes the metaphase-to-telophase transition in mitotic cells. Introduction of N'-AURKB but not C'-AURKB promotes colony formation and malignant growth of tumor cells in vitro and in vivo using a murine xenograft model. Altogether, our findings uncover a proteolytic cleavage mechanism by which oncoviruses induce cancer cell segregation and tumorigenesis.

The spindle assembly checkpoint and speciation

A mechanism is proposed by which speciation may occur without the need to postulate geographical isolation of the diverging populations. Closely related species that occupy overlapping or adjacent ecological niches often have an almost identical genome but differ by chromosomal rearrangements that result in reproductive isolation. The mitotic spindle assembly checkpoint normally functions to prevent gametes with non-identical karyotypes from forming viable zygotes. Unless gametes from two individuals happen to undergo the same chromosomal rearrangement at the same place and time, a most improbable situation, there has been no satisfactory explanation of how such rearrangements can propagate. Consideration of the dynamics of the spindle assembly checkpoint suggest that chromosomal fission or fusion events may occur that allow formation of viable heterozygotes between the rearranged and parental karyotypes, albeit with decreased fertility. Evolutionary dynamics calculations suggest that if the resulting heterozygous organisms have a selective advantage in an adjoining or overlapping ecological niche from that of the parental strain, despite the reproductive disadvantage of the population carrying the altered karyotype, it may accumulate sufficiently that homozygotes begin to emerge. At this point the reproductive disadvantage of the rearranged karyotype disappears, and a single population has been replaced by two populations that are partially reproductively isolated. This definition of species as populations that differ from other, closely related, species by karyotypic changes is consistent with the classical definition of a species as a population that is capable of interbreeding to produce fertile progeny. Even modest degrees of reproductive impairment of heterozygotes between two related populations may lead to speciation by this mechanism, and geographical isolation is not necessary for the process.

New landscapes and horizons in hepatocellular carcinoma therapy

Hepatocellular carcinoma (HCC), is the sixth most frequent form of cancer and leads to the fourth highest number of deaths each year. HCC results from a combination of environmental factors and aging as there are driver mutations at oncogenes which occur during aging. Most of HCCs are diagnosed at advanced stage preventing curative therapies. Treatment in advanced stage is a challenging and pressing problem, and novel and well-tolerated therapies are urgently needed. We will discuss further advances beyond sorafenib that target additional signaling pathways and immune checkpoint proteins. The scenario of possible systemic therapies for patients with advanced HCC has changed dramatically in recent years. Personalized genomics and various other omics approaches may identify actionable biochemical targets, which are activated in individual patients, which may enhance therapeutic outcomes. Further studies are needed to identify predictive biomarkers and aberrantly activated signaling pathways capable of guiding the clinician in choosing the most appropriate therapy for the individual patient.

Aurora B induces epithelial-mesenchymal transition by stabilizing Snail1 to promote basal-like breast cancer metastasis

Aurora B is a serine/threonine kinase that has been implicated in regulating cell proliferation in distinct cancers, including breast cancer. Here we show that Aurora B expression is elevated in basal-like breast cancer (BLBC) compared with other breast cancer subtypes. This high level of expression seems to correlate with poor metastasis-free survival and relapse-free survival in affected patients. Mechanistically, we show that elevated Aurora B expression in breast cancer cells activates AKT/GSK3β to stabilize Snail1 protein, a master regulator of epithelial-mesenchymal transition (EMT), leading to EMT induction in a kinase-dependent manner. Conversely, Aurora B knock down by short-hairpin RNAs (shRNAs) suppresses AKT/GSK3β/Snail1 signaling, reverses EMT and reduces breast cancer metastatic potential in vitro and in vivo. Finally, we identified a specific OCT4 phosphorylation site (T343) responsible for mediating Aurora B-induced AKT/GSK3β/Snail1 signaling and EMT that could be attenuated by Aurora B kinase inhibitor treatment. These findings support that Aurora B induces EMT to promote breast cancer metastasis via OCT4/AKT/GSK3β/Snail1 signaling. Pharmacologic Aurora B inhibition might be a potential effective treatment for breast cancer patients with metastatic disease.