beta-Catenin is a Nek2 substrate involved in centrosome separation

YBX1 as a therapeutic target to suppress the LRP1-β-catenin-RRM1 axis and overcome gemcitabine resistance in pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is highly malignant and has a poor prognosis, without effective therapeutic targets in common gene mutations. Gemcitabine, a first-line chemotherapeutic for PDAC, confers <10 % 5-year survival rate because of drug resistance. Y-box binding protein 1 (YBX1), associated with multidrug-resistance gene activation, remains unelucidated in PDAC gemcitabine resistance. In vivo and in vitro, we verified YBX1's promotional effects, especially gemcitabine resistance, in pancreatic cancer cells. YBX1-induced LRP1 transcription by binding to the LRP1 promoter region significantly altered the concentration and distribution of β-catenin in pancreatic cancer cells. Through TCF3, β-catenin bound to the promoter region of RRM1, a key gene for gemcitabine resistance, that promotes RRM1 expression. Combination therapy with the YBX1 inhibitor SU056 and gemcitabine effectively reduced gemcitabine resistance in in vivo and in vitro experiments. High YBX1 expression promoted pathogenesis and gemcitabine resistance in pancreatic cancer through the YBX1-LRP1-β-catenin-RRM1 axis. Combining YBX1 inhibitors with gemcitabine may provide a new direction for combination chemotherapy to overcome gemcitabine resistance, which frequently occurs during chemotherapy for pancreatic cancer.

Comprehensive proteomics analysis reveals novel Nek2-regulated pathways and therapeutic targets in cancer

The mitotic kinase Nek2, often overexpressed in various cancers, plays a pivotal role in key cellular processes like the cell cycle, proliferation, and drug resistance. As a result, targeting Nek2 has become an appealing strategy for cancer therapy. To gain a comprehensive understanding of the cellular changes associated with Nek2 activity modulation, we performed a global proteomics analysis using LC-MS/MS. Through bioinformatics tools, we identified molecular pathways that are differentially regulated in cancer cells with Nek2 overexpression or depletion. Of the 1815 proteins identified, 358 exceeded the 20 % significance threshold. By integrating LC-MS/MS data with cancer patient datasets, we observed a strong correlation between Nek2 expression and the levels of KIF20B and RRM1. Silencing Nek2 led to a significant reduction in KIF20B and RRM1 protein levels, and potential phosphorylation sites for these proteins by Nek2 were identified. In summary, our data suggests that KIF20B and RRM1 are promising therapeutic targets, either independently or alongside Nek2 inhibitors, to improve clinical outcomes. Further analyses are necessary to fully understand Nek2's interactions with these proteins and their clinical relevance.

NEK2 plays an essential role in porcine embryonic development by maintaining mitotic division and DNA damage response via the Wnt/β-catenin signalling pathway

NIMA-related kinase 2 (NEK2) is a serine/threonine protein kinase that regulates mitosis and plays pivotal roles in cell cycle regulation and DNA damage repair. However, its function in porcine embryonic development is unknown. In this study, we used an NEK2-specific inhibitor, JH295 (JH), to investigate the role of NEK2 in embryonic development and the underlying regulatory mechanisms. Inhibition of NEK2 after parthenogenesis activation or in vitro fertilization significantly reduced the rates of cleavage and blastocyst formation, the numbers of trophectoderm and total cells and the cellular survival rate compared with the control condition. NEK2 inhibition delayed cell cycle progression at all stages from interphase to cytokinesis during the first mitotic division; it caused abnormal nuclear morphology in two- and four-cell stage embryos. Additionally, NEK2 inhibition significantly increased DNA damage and apoptosis, and it altered the expression levels of DNA damage repair- and apoptosis-related genes. Intriguingly, NEK2 inhibition downregulated the expression of β-catenin and its downstream target genes. To validate the relationship between Wnt/β-catenin signalling and NEK2 during porcine embryonic development, we cultured porcine embryos in JH-treated medium with or without CHIR99021, a Wnt activator. CHIR99021 co-treatment strongly restored the developmental parameters reduced by NEK2 inhibition to control levels. Our findings suggest that NEK2 plays an essential role in porcine embryonic development by regulating DNA damage repair and normal mitotic division via the Wnt/β-catenin signalling pathway.

Mitotic kinases are emerging therapeutic targets against metastatic breast cancer

This review aims to outline mitotic kinase inhibitors' roles as potential therapeutic targets and assess their suitability as a stand-alone clinical therapy or in combination with standard treatments for advanced-stage solid tumors, including triple-negative breast cancer (TNBC). Breast cancer poses a significant global health risk, with TNBC standing out as the most aggressive subtype. Comprehending the role of mitosis is crucial for understanding how TNBC advances from a solid tumor to metastasis. Chemotherapy is the primary treatment used to treat TNBC. Some types of chemotherapeutic agents target cells in mitosis, thus highlighting the need to comprehend the molecular mechanisms governing mitosis in cancer. This understanding is essential for devising targeted therapies to disrupt these mitotic processes, prevent or treat metastasis, and improve patient outcomes. Mitotic kinases like Aurora kinase A, Aurora Kinase B, never in mitosis gene A-related kinase 2, Threonine-Tyrosine kinase, and Polo-kinase 1 significantly impact cell cycle progression by contributing to chromosome separation and centrosome homeostasis. When these kinases go awry, they can trigger chromosome instability, increase cell proliferation, and activate different molecular pathways that culminate in a transition from epithelial to mesenchymal cells. Ongoing clinical trials investigate various mitotic kinase inhibitors as potential biological treatments against advanced solid tumors. While clinical trials against mitotic kinases have shown some promise in the clinic, more investigation is necessary, since they induce severe adverse effects, particularly affecting the hematopoietic system.

The interplay between Wnt signaling pathways and microtubule dynamics

Wnt signaling pathways represent an evolutionarily highly conserved, intricate network of molecular interactions that regulates various aspects of cellular behavior, including embryonic development and tissue homeostasis. Wnt signaling pathways share the β-catenin-dependent (canonical) and the multiple β-catenin-independent (non-canonical) pathways. These pathways collectively orchestrate a wide range of cellular processes through distinct mechanisms of action. Both the β-catenin-dependent and β-catenin-independent pathways are closely intertwined with microtubule dynamics, underscoring the complex crosstalk between Wnt signaling and the cellular cytoskeleton. This interplay involves several mechanisms, including how the components of Wnt signaling can influence the stability, organization, and distribution of microtubules. The modulation of microtubule dynamics by Wnt signaling plays a crucial role in coordinating cellular behaviors and responses to external signals. In this comprehensive review, we discussed the current understanding of how Wnt signaling and microtubule dynamics intersect in various aspects of cellular behavior. This study provides insights into our understanding of these crucial cellular processes.

Bifunctional Inhibitor Reveals NEK2 as a Therapeutic Target and Regulator of Oncogenic Pathways in Lymphoma

Expression of the serine/threonine kinase never in mitosis gene A (NIMA)-related kinase 2 (NEK2) is essential for entry into mitosis via its role in facilitating centrosome separation. Its overactivity can lead to tumorigenesis and drug resistance through the activation of several oncogenic pathways, including AKT. Although the cancer-enabling activities of NEK2 are documented in many malignancies, including correlations with poor survival in myeloma, breast, and non-small cell lung cancer, little is known about the role of NEK2 in lymphoma. Here, in tumors from patients with diffuse large B-cell lymphoma (DLBCL), the most common, aggressive non-Hodgkin lymphoma, we found a high abundance of NEK2 mRNA and protein associated with an inferior overall survival. Using our recently developed NEK2 inhibitor, NBI-961, we discovered that DLBCL cell lines and patient-derived cells exhibit a dependency on NEK2 for their viability. This compromised cell fitness was directly attributable to efficient NEK2 inhibition and proteasomal degradation by NBI-961. In a subset of particularly sensitive DLBCL cells, NBI-961 induced G2/mitosis arrest and apoptosis. In contrast, an existing indirect NEK2 inhibitor, INH154, did not prevent NEK2 autophosphorylation, induce NEK2 proteasomal degradation, or affect cell viability. Global proteomics and phospho-proteomics revealed that NEK2 orchestrates cell-cycle and apoptotic pathways through regulation of both known and new signaling molecules. We show the loss of NEK2-sensitized DLBCL to the chemotherapy agents, doxorubicin and vincristine, and effectively suppressed tumor growth in mice. These studies establish the oncogenic activity of NEK2 in DLBCL and set the foundation for development of anti-NEK2 therapeutic strategies in this frequently refractory and relapse-prone cancer.

Dual roles of CCDC102A in governing centrosome duplication and cohesion

In animal cells, the dysregulation of centrosome duplication and cohesion maintenance leads to abnormal spindle assembly and chromosomal instability, contributing to developmental disorders and tumorigenesis. However, the molecular mechanisms involved in maintaining accurate centrosome number control and tethering are not fully understood. Here, we identified coiled-coil domain-containing 102A (CCDC102A) as a centrosomal protein exhibiting a barrel-like structure in the proximal regions of parent centrioles, where it prevents centrosome overduplication by restricting interactions between Cep192 and Cep152 on centrosomes, thereby ensuring bipolar spindle formation. Additionally, CCDC102A regulates the centrosome linker by recruiting and binding C-Nap1; it is removed from the centrosome after Nek2A-mediated phosphorylation at the onset of mitosis. Overall, our results indicate that CCDC102A participates in controlling centrosome number and maintaining centrosome cohesion, suggesting that a well-tuned system regulates centrosome structure and function throughout the cell cycle.

β-catenin mediates growth defects induced by centrosome loss in a subset of APC mutant colorectal cancer independently of p53

Colorectal cancer is the third most common cancer and the second leading cause of cancer-related deaths worldwide. The centrosome is the main microtubule-organizing center in animal cells and centrosome amplification is a hallmark of cancer cells. To investigate the importance of centrosomes in colorectal cancer, we induced centrosome loss in normal and cancer human-derived colorectal organoids using centrinone B, a Polo-like kinase 4 (Plk4) inhibitor. We show that centrosome loss represses human normal colorectal organoid growth in a p53-dependent manner in accordance with previous studies in cell models. However, cancer colorectal organoid lines exhibited different sensitivities to centrosome loss independently of p53. Centrinone-induced cancer organoid growth defect/death positively correlated with a loss of function mutation in the APC gene, suggesting a causal role of the hyperactive WNT pathway. Consistent with this notion, β-catenin inhibition using XAV939 or ICG-001 partially prevented centrinone-induced death and rescued the growth two APC-mutant organoid lines tested. Our study reveals a novel role for canonical WNT signaling in regulating centrosome loss-induced growth defect/death in a subset of APC-mutant colorectal cancer independently of the classical p53 pathway.

Vinculin is required for interkinetic nuclear migration (INM) and cell cycle progression

Vinculin is an actin-binding protein (ABP) that strengthens the connection between the actin cytoskeleton and adhesion complexes. It binds to β-catenin/N-cadherin complexes in apical adherens junctions (AJs), which maintain cell-to-cell adhesions, and to talin/integrins in the focal adhesions (FAs) that attach cells to the basal membrane. Here, we demonstrate that β-catenin targets vinculin to the apical AJs and the centrosome in the embryonic neural tube (NT). Suppression of vinculin slows down the basal-to-apical part of interkinetic nuclear migration (BAINM), arrests neural stem cells (NSCs) in the G2 phase of the cell cycle, and ultimately dismantles the apical actin cytoskeleton. In the NSCs, mitosis initiates when an internalized centrosome gathers with the nucleus during BAINM. Notably, our results show that the first centrosome to be internalized is the daughter centrosome, where β-catenin and vinculin accumulate, and that vinculin suppression prevents centrosome internalization. Thus, we propose that vinculin links AJs, the centrosome, and the actin cytoskeleton where actomyosin contraction forces are required.

A Shortcut from Genome to Drug: The Employment of Bioinformatic Tools to Find New Targets for Gastric Cancer Treatment

Gastric cancer (GC) is a highly heterogeneous, complex disease and the fifth most common cancer worldwide (about 1 million cases and 784,000 deaths worldwide in 2018). GC has a poor prognosis (the 5-year survival rate is less than 20%), but there is an effort to find genes highly expressed during tumor establishment and use the related proteins as targets to find new anticancer molecules. Data were collected from the Gene Expression Omnibus (GEO) bank to obtain three dataset matrices analyzing gastric tumor tissue versus normal gastric tissue and involving microarray analysis performed using the GPL570 platform and different sources. The data were analyzed using the GEPIA tool for differential expression and KMPlot for survival analysis. For more robustness, GC data from the TCGA database were used to corroborate the analysis of data from GEO. The genes found in in silico analysis in both GEO and TCGA were confirmed in several lines of GC cells by RT-qPCR. The AlphaFold Protein Structure Database was used to find the corresponding proteins. Then, a structure-based virtual screening was performed to find molecules, and docking analysis was performed using the DockThor server. Our in silico and RT-qPCR analysis results confirmed the high expression of the AJUBA, CD80 and NOLC1 genes in GC lines. Thus, the corresponding proteins were used in SBVS analysis. There were three molecules, one molecule for each target, MCULE-2386589557-0-6, MCULE-9178344200-0-1 and MCULE-5881513100-0-29. All molecules had favorable pharmacokinetic, pharmacodynamic and toxicological properties. Molecular docking analysis revealed that the molecules interact with proteins in critical sites for their activity. Using a virtual screening approach, a molecular docking study was performed for proteins encoded by genes that play important roles in cellular functions for carcinogenesis. Combining a systematic collection of public microarray data with a comparative meta-profiling, RT-qPCR, SBVS and molecular docking analysis provided a suitable approach for finding genes involved in GC and working with the corresponding proteins to search for new molecules with anticancer properties.

Phosphorylation of the prolyl isomerase Cyclophilin A regulates its localisation and release from the centrosome during mitosis

The centrosome acts as a protein platform from which proteins are deployed to function throughout the cell cycle. Previously, we have shown that the prolyl isomerase Cyclophilin A (CypA) localizes to the centrosome in interphase and re-localizes to the midbody during mitosis where it functions in cytokinesis. In this study, investigation of CypA by SDS-PAGE during the cell cycle reveals that it undergoes a mobility shift during mitosis, indicative of a post-translational modification, which may correlate with its subcellular re-localization. Due to the lack of a phospho-specific antibody, we used site-directed mutagenesis to demonstrate that the previously identified serine 77 phosphorylation site within CypA is important for control of CypA centrosome localization. Furthermore, CypA is shown to interact with the mitotic NIMA-related kinase 2 (Nek2) during interphase and mitosis, while also interacting with the Nek2-antagonist PP1 during interphase but not during mitosis, suggesting a potential role for the Nek2-PP1 complex in CypA phospho-regulation. In support of this, Nek2 is capable of phosphorylating CypA in vitro. Overall, this work reveals that phosphorylation of CypA at serine 77 is important for its release from the centrosome during mitosis and may be regulated by the activity of Nek2 and PP1 during the cell cycle.

N6-Methyladenosine-Mediated Up-Regulation of FZD10 Regulates Liver Cancer Stem Cells' Properties and Lenvatinib Resistance Through WNT/β-Catenin and Hippo Signaling Pathways

BACKGROUND & AIMS

Hepatocellular carcinoma (HCC) is one of the leading causes of cancer-related deaths worldwide, but there is a deficiency of early diagnosis biomarkers and therapeutic targets. Drug resistance accounts for most HCC-related deaths, yet the mechanisms underlying drug resistance remain poorly understood.

METHODS

Expression of Frizzled-10 (FZD10) in liver cancer stem cells (CSCs) was identified by means of RNA sequencing and validated by means of real-time polymerase chain reaction and immunohistochemistry. In vitro and in vivo experiments were used to assess the effect of FZD10 on liver CSC expansion and lenvatinib resistance. RNA sequencing, RNA binding protein immunoprecipitation, and luciferase report assays were applied to explore the mechanism underlying FZD10-mediated liver CSCs expansion and lenvatinib resistance.

RESULTS

Activation of FZD10 in liver CSCs was mediated by METTL3-dependent N6-methyladenosine methylation of FZD10 messenger RNA. Functional studies revealed that FZD10 promotes self-renewal, tumorigenicity, and metastasis of liver CSCs via activating β-catenin and YAP1. The FZD10-β-catenin/YAP1 axis is activated in liver CSCs and predicts poor prognosis. Moreover, FZD10-β-catenin/c-Jun axis transcriptionally activates METTL3 expression, forming a positive feedback loop. Importantly, the FZD10/β-catenin/c-Jun/MEK/ERK axis determines the responses of hepatoma cells to lenvatinib treatment. Analysis of patient cohort, patient-derived tumor organoids, and patient-derived xenografts further suggest that FZD10 might predict lenvatinib clinical benefit in patients with HCC. Furthermore, treatment of lenvatinib-resistant HCC with adeno-associated virus targeting FZD10 or a β-catenin inhibitor restored lenvatinib response.

CONCLUSIONS

Elevated FZD10 expression promotes expansion of liver CSCs and lenvatinib resistance, indicating that FZD10 expression is a novel prognostic biomarker and therapeutic target for human HCC.

The NEK family of serine/threonine kinases as a biomarker for cancer

Cancer is defined by unrestrained cell proliferation due to impaired protein activity. Cell cycle-related proteins are likely to play a role in human cancers, including proliferation, invasion, and therapeutic resistance. The serine/threonine NEK kinases are the part of Never In Mitosis A Kinases (NIMA) family, which are less explored kinase family involved in the cell cycle, checkpoint regulation, and cilia biology. They comprise of eleven members, namely NEK1, NEK2, NEK3, NEK4, NEK5, NEK6, NEK7, NEK8, NEK9, NEK10, and NEK11, located in different cellular regions. Recent research has shown the role of NEK family in various cancers by perversely expressing. Therefore, this review aimed to provide a systematic account of our understanding of NEK kinases; structural details; and its role in the cell cycle regulation. Furthermore, we have comprehensively reviewed the NEK kinases in terms of their expression and regulation in different cancers. Lastly, we have emphasized on some of the potential NEK inhibitors reported so far.

Emerging roles of centrosome cohesion

The centrosome, consisting of centrioles and the associated pericentriolar material, is the main microtubule-organizing centre (MTOC) in animal cells. During most of interphase, the two centrosomes of a cell are joined together by centrosome cohesion into one MTOC. The most dominant element of centrosome cohesion is the centrosome linker, an interdigitating, fibrous network formed by the protein C-Nap1 anchoring a number of coiled-coil proteins including rootletin to the proximal end of centrioles. Alternatively, centrosomes can be kept together by the action of the minus end directed kinesin motor protein KIFC3 that works on interdigitating microtubules organized by both centrosomes and probably by the actin network. Although cells connect the two interphase centrosomes by several mechanisms into one MTOC, the general importance of centrosome cohesion, particularly for an organism, is still largely unclear. In this article, we review the functions of the centrosome linker and discuss how centrosome cohesion defects can lead to diseases.

Superresolution microscopy localizes endogenous Dvl2 to Wnt signaling-responsive biomolecular condensates

Wnt signaling governs cell fate and tissue polarity across species. The Dishevelled proteins are central to Wnt signaling cascades. Wnt-mediated multiprotein complexes such as the “signalosome” and the “destruction complex” have been proposed to represent biomolecular condensates. These nonmembranous, specialized compartments have been suggested to form through liquid–liquid phase separation and ensure correctly proceeding physiological reactions. Although biomolecular condensates have increasingly been studied, key questions remain regarding, for example, their architecture and physiological regulation. Here, superresolution microscopy after endogenous labeling of Dishevelled-2 gives insights into protein functions and Wnt signaling at physiological levels. It reveals the distinct molecular architecture of endogenous Wnt condensates at single-molecule resolution and illustrates close interactions at the centrosome.

During organismal development, homeostasis, and disease, Dishevelled (Dvl) proteins act as key signaling factors in beta-catenin–dependent and beta-catenin–independent Wnt pathways. While their importance for signal transmission has been genetically demonstrated in many organisms, our mechanistic understanding is still limited. Previous studies using overexpressed proteins showed Dvl localization to large, punctate-like cytoplasmic structures that are dependent on its DIX domain. To study Dvl’s role in Wnt signaling, we genome engineered an endogenously expressed Dvl2 protein tagged with an mEos3.2 fluorescent protein for superresolution imaging. First, we demonstrate the functionality and specificity of the fusion protein in beta-catenin–dependent and beta-catenin–independent signaling using multiple independent assays. We performed live-cell imaging of Dvl2 to analyze the dynamic formation of the supramolecular cytoplasmic Dvl2_mEos3.2 condensates. While overexpression of Dvl2_mEos3.2 mimics the previously reported formation of abundant large “puncta,” supramolecular condensate formation at physiological protein levels is only observed in a subset of cells with approximately one per cell. We show that, in these condensates, Dvl2 colocalizes with Wnt pathway components at gamma-tubulin and CEP164-positive centrosomal structures and that the localization of Dvl2 to these condensates is Wnt dependent. Single-molecule localization microscopy using photoactivated localization microscopy (PALM) of mEos3.2 in combination with DNA-PAINT demonstrates the organization and repetitive patterns of these condensates in a cell cycle–dependent manner. Our results indicate that the localization of Dvl2 in supramolecular condensates is coordinated dynamically and dependent on cell state and Wnt signaling levels. Our study highlights the formation of endogenous and physiologically regulated biomolecular condensates in the Wnt pathways at single-molecule resolution.

Moonlighting at the Poles: Non-Canonical Functions of Centrosomes

Centrosomes are best known as the microtubule organizing centers (MTOCs) of eukaryotic cells. In addition to their classic role in chromosome segregation, centrosomes play diverse roles unrelated to their MTOC activity during cell proliferation and quiescence. Metazoan centrosomes and their functional doppelgängers from lower eukaryotes, the spindle pole bodies (SPBs), act as important structural platforms that orchestrate signaling events essential for cell cycle progression, cellular responses to DNA damage, sensory reception and cell homeostasis. Here, we provide a critical overview of the unconventional and often overlooked roles of centrosomes/SPBs in the life cycle of eukaryotic cells.

Factor quinolinone inhibitors disrupt spindles and multiple LSF (TFCP2)-protein interactions in mitosis, including with microtubule-associated proteins

Factor quinolinone inhibitors (FQIs), a first-in-class set of small molecule inhibitors targeted to the transcription factor LSF (TFCP2), exhibit promising cancer chemotherapeutic properties. FQI1, the initial lead compound identified, unexpectedly induced a concentration-dependent delay in mitotic progression. Here, we show that FQI1 can rapidly and reversibly lead to mitotic arrest, even when added directly to mitotic cells, implying that FQI1-mediated mitotic defects are not transcriptionally based. Furthermore, treatment with FQIs resulted in a striking, concentration-dependent diminishment of spindle microtubules, accompanied by a concentration-dependent increase in multi-aster formation. Aberrant γ-tubulin localization was also observed. These phenotypes suggest that perturbation of spindle microtubules is the primary event leading to the mitotic delays upon FQI1 treatment. Previously, FQIs were shown to specifically inhibit not only LSF DNA-binding activity, which requires LSF oligomerization to tetramers, but also other specific LSF-protein interactions. Other transcription factors participate in mitosis through non-transcriptional means, and we recently reported that LSF directly binds α-tubulin and is present in purified cellular tubulin preparations. Consistent with a microtubule role for LSF, here we show that LSF enhanced the rate of tubulin polymerization in vitro, and FQI1 inhibited such polymerization. To probe whether the FQI1-mediated spindle abnormalities could result from inhibition of mitotic LSF-protein interactions, mass spectrometry was performed using as bait an inducible, tagged form of LSF that is biotinylated by endogenous enzymes. The global proteomics analysis yielded expected associations for a transcription factor, notably with RNA processing machinery, but also to nontranscriptional components. In particular, and consistent with spindle disruption due to FQI treatment, mitotic, FQI1-sensitive interactions were identified between the biotinylated LSF and microtubule-associated proteins that regulate spindle assembly, positioning, and dynamics, as well as centrosome-associated proteins. Probing the mitotic LSF interactome using small molecule inhibitors therefore supported a non-transcriptional role for LSF in mediating progression through mitosis.

In Mitosis You Are Not: The NIMA Family of Kinases in Aspergillus, Yeast, and Mammals

The Never in mitosis gene A (NIMA) family of serine/threonine kinases is a diverse group of protein kinases implicated in a wide variety of cellular processes, including cilia regulation, microtubule dynamics, mitotic processes, cell growth, and DNA damage response. The founding member of this family was initially identified in Aspergillus and was found to play important roles in mitosis and cell division. The yeast family has one member each, Fin1p in fission yeast and Kin3p in budding yeast, also with functions in mitotic processes, but, overall, these are poorly studied kinases. The mammalian family, the main focus of this review, consists of 11 members named Nek1 to Nek11. With the exception of a few members, the functions of the mammalian Neks are poorly understood but appear to be quite diverse. Like the prototypical NIMA, many members appear to play important roles in mitosis and meiosis, but their functions in the cell go well beyond these well-established activities. In this review, we explore the roles of fungal and mammalian NIMA kinases and highlight the most recent findings in the field.

The Wnt Pathway: From Signaling Mechanisms to Synthetic Modulators

The Wnt pathway is central to a host of developmental and disease-related processes. The remarkable conservation of this intercellular signaling cascade throughout metazoan lineages indicates that it coevolved with multicellularity to regulate the generation and spatial arrangement of distinct cell types. By regulating cell fate specification, mitotic activity, and cell polarity, Wnt signaling orchestrates development and tissue homeostasis, and its dysregulation is implicated in developmental defects, cancer, and degenerative disorders. We review advances in our understanding of this key pathway, from Wnt protein production and secretion to relay of the signal in the cytoplasm of the receiving cell. We discuss the evolutionary history of this pathway as well as endogenous and synthetic modulators of its activity. Finally, we highlight remaining gaps in our knowledge of Wnt signal transduction and avenues for future research. Expected final online publication date for the Annual Review of Biochemistry, Volume 91 is June 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Keep Calm and Carry on with Extra Centrosomes

Simple Summary

Precise chromosome segregation during mitosis is a vital event orchestrated by formation of bipolar spindle poles. Supernumerary centrosomes, caused by centrosome amplification, deteriorates mitotic processes, resulting in segregation defects leading to chromosomal instability (CIN). Centrosome amplification is frequently observed in various types of cancer and considered as a significant contributor to destabilization of chromosomes. This review provides a comprehensive overview of causes and consequences of centrosome amplification thoroughly describing molecular mechanisms.

Abstract

Aberrations in the centrosome number and structure can readily be detected at all stages of tumor progression and are considered hallmarks of cancer. Centrosome anomalies are closely linked to chromosome instability and, therefore, are proposed to be one of the driving events of tumor formation and progression. This concept, first posited by Boveri over 100 years ago, has been an area of interest to cancer researchers. We have now begun to understand the processes by which these numerical and structural anomalies may lead to cancer, and vice-versa: how key events that occur during carcinogenesis could lead to amplification of centrosomes. Despite the proliferative advantages that having extra centrosomes may confer, their presence can also lead to loss of essential genetic material as a result of segregational errors and cancer cells must deal with these deadly consequences. Here, we review recent advances in the current literature describing the mechanisms by which cancer cells amplify their centrosomes and the methods they employ to tolerate the presence of these anomalies, focusing particularly on centrosomal clustering.

Nek2 Kinase Signaling in Malaria, Bone, Immune and Kidney Disorders to Metastatic Cancers and Drug Resistance: Progress on Nek2 Inhibitor Development

Cell cycle kinases represent an important component of the cell machinery that controls signal transduction involved in cell proliferation, growth, and differentiation. Nek2 is a mitotic Ser/Thr kinase that localizes predominantly to centrosomes and kinetochores and orchestrates centrosome disjunction and faithful chromosomal segregation. Its activity is tightly regulated during the cell cycle with the help of other kinases and phosphatases and via proteasomal degradation. Increased levels of Nek2 kinase can promote centrosome amplification (CA), mitotic defects, chromosome instability (CIN), tumor growth, and cancer metastasis. While it remains a highly attractive target for the development of anti-cancer therapeutics, several new roles of the Nek2 enzyme have recently emerged: these include drug resistance, bone, ciliopathies, immune and kidney diseases, and parasitic diseases such as malaria. Therefore, Nek2 is at the interface of multiple cellular processes and can influence numerous cellular signaling networks. Herein, we provide a critical overview of Nek2 kinase biology and discuss the signaling roles it plays in both normal and diseased human physiology. While the majority of research efforts over the last two decades have focused on the roles of Nek2 kinase in tumor development and cancer metastasis, the signaling mechanisms involving the key players associated with several other notable human diseases are highlighted here. We summarize the efforts made so far to develop Nek2 inhibitory small molecules, illustrate their action modalities, and provide our opinion on the future of Nek2-targeted therapeutics. It is anticipated that the functional inhibition of Nek2 kinase will be a key strategy going forward in drug development, with applications across multiple human diseases.

Immune Milieu and Genomic Alterations Set the Triple-Negative Breast Cancer Immunomodulatory Subtype Tumor Behavior

Simple Summary

Triple-negative breast cancer (TNBC) is an aggressive and highly heterogeneous breast cancer subtype, both molecular and transcriptomic. Gene expression patterns identified seven TNBC subtypes; basal-like 1 (BL1), basal-like 2 (BL2), immunomodulatory (IM), mesenchymal (M), mesenchymal stem-like (MSL), luminal androgen receptor (LAR), and unstable (UNS). Herein, we contrasted the IM subtype with non-IM TNBC, including clinical, histopathological, and molecular variables. Our results showed that the IM subtype featured an increased FOXP3+ TILs infiltration and a higher CTLA-4 and PD-L1 expression compared with non-IM tumors. Long intergenic non-coding RNAs associated with the immune response through transcriptomic and enrichment analyses characterized the IM-subtype enriched by the β-catenin signaling pathway. Additionally, DNA sequencing identified differences in mutation rates as well as some specific mutations. These results should motivate the design of future clinical trials in which the benefit of immune-based therapy in this subgroup of patients could be evaluated.

Abstract

Triple-negative breast cancer (TNBC) is an aggressive and heterogeneous disease. Seven subtypes have been described based on gene expression patterns. Herein, we characterized the tumor biology and clinical behavior of the immunomodulatory (IM) subtype. Methods: Formalin-fixed paraffin-embedded tumor samples from 68 high-risk (stage III-IV) TNBC patients were analyzed through microarrays, immunohistochemistry, and DNA sequencing. Results: The IM subtype was identified in 24% of TNBC tumor samples and characterized by a higher intratumoral (intT) and stromal (strml) infiltration of FOXP3+ TILs (Treg) compared with non-IM subtypes. Further, PD-L1+ (>1%) expression was significantly higher, as well as CTLA-4+ intT and strml expression in the IM subtype. Differential expression and gene set enrichment analysis identified biological processes associated with the immune system. Pathway analysis revealed enrichment of the β-catenin signaling pathway. The non-coding analysis led to seven Long Intergenic Non-Protein Coding RNAs (lincRNAs) (6 up-regulated and 1 down-regulated) that were associated with a favorable prognosis in the TNBC-IM subtype. The DNA sequencing highlighted two genes relevant to immune system responses: CTNNB1 (Catenin β-1) and IDH1. Conclusion: the IM subtype showed a distinct immune microenvironment, as well as subtype-specific genomic alterations. Characterizing TNBC at a molecular and transcriptomic level might guide immune-based therapy in this subgroup of patients.

Phosphorylation of β-catenin Ser60 by polo-like kinase 1 drives the completion of cytokinesis

β-Catenin is a multifunctional protein and participates in numerous processes required for embryonic development, cell proliferation, and homeostasis through various molecular interactions and signaling pathways. To date, however, there is no direct evidence that β-catenin contributes to cytokinesis. Here, we identify a novel p-S60 epitope on β-catenin generated by Plk1 kinase activity, which can be found at the actomyosin contractile ring of early telophase cells and at the midbody of late telophase cells. Depletion of β-catenin leads to cytokinesis-defective phenotypes, which eventually result in apoptotic cell death. In addition, phosphorylation of β-catenin Ser60 by Plk1 is essential for the recruitment of Ect2 to the midbody, activation of RhoA, and interaction between β-catenin, Plk1, and Ect2. Time-lapse image analysis confirmed the importance of β-catenin phospho-Ser60 in furrow ingression and the completion of cytokinesis. Taken together, we propose that phosphorylation of β-catenin Ser60 by Plk1 in cooperation with Ect2 is essential for the completion of cytokinesis. These findings may provide fundamental knowledge for the research of cytokinesis failure-derived human diseases.

Roles of RACK1 in centrosome regulation and carcinogenesis

Receptor for activated C kinase 1 (RACK1) regulates various cellular functions and signaling pathways by interacting with different proteins. Recently, we showed that RACK1 interacts with breast cancer gene 1 (BRCA1), which regulates centrosome duplication. RACK1 localizes to centrosomes and spindle poles and is involved in the proper centrosomal localization of BRCA1. The interaction between RACK1 and BRCA1 is critical for the regulation of centrosome number. In addition, RACK1 contributes to centriole duplication by regulating polo-like kinase 1 (PLK1) activity in S phase. RACK1 binds directly to PLK1 and Aurora A, promoting the phosphorylation of PLK1 and activating the Aurora A/PLK1 signaling axis. Overexpression of RACK1 causes centrosome amplification, especially in mammary gland epithelial cells, inducing overactivation of PLK1 followed by premature centriole disengagement and centriole re-duplication. Other proteins, including hypoxia-inducible factor α, von Hippel-Lindau protein, heat-shock protein 90, β-catenin, and glycogen synthase kinase-3β, interact with RACK1 and play roles in centrosome regulation. In this review, we focus on the roles and underlying molecular mechanisms of RACK1 in centrosome regulation mediated by its interaction with different proteins and the modulation of their functions.

FILIP1L Loss Is a Driver of Aggressive Mucinous Colorectal Adenocarcinoma and Mediates Cytokinesis Defects through PFDN1

Aneuploid mucinous colorectal adenocarcinoma (MAC) is an aggressive subtype of colorectal cancer with poor prognosis. The tumorigenic mechanisms in aneuploid MAC are currently unknown. Here we show that downregulation of Filamin A-interacting protein 1-like (FILIP1L) is a driver of MAC. Loss of FILIP1L increased xenograft growth, and, in colon-specific knockout mice, induced colonic epithelial hyperplasia and mucin secretion. The molecular chaperone prefoldin 1 (PFDN1) was identified as a novel binding partner of FILIP1L at the centrosomes throughout mitosis. FILIP1L was required for proper centrosomal localization of PFDN1 and regulated proteasome-dependent degradation of PFDN1. Importantly, increased PFDN1, caused by downregulation of FILIP1L, drove multinucleation and cytokinesis defects in vitro and in vivo, which were confirmed by time-lapse imaging and 3D cultures of normal epithelial cells. Overall, these findings suggest that downregulation of FILIP1L and subsequent upregulation of PFDN1 is a driver of the unique neoplastic characteristics in aggressive aneuploid MAC. SIGNIFICANCE: This study identifies FILIP1L as a tumor suppressor in mucinous colon cancer and demonstrates that FILIP1L loss results in aberrant stabilization of a centrosome-associated chaperone protein to drive aneuploidy and disease progression.

HN1 interacts with γ-tubulin to regulate centrosomes in advanced prostate cancer cells

Prostate cancer is one of the most common cancer for men worldwide with advanced forms showing supernumerary or clustered centrosomes. Hematological and neurological expressed 1 (HN1) also known as Jupiter Microtubule Associated Homolog 1 (JPT1) belongs to a small poorly understood family of genes that are evolutionarily conserved across vertebrate species. The co-expression network of HN1 from the TCGA PRAD dataset indicates the putative role of HN1 in centrosome-related processes in the context of prostate cancer. HN1 expression is low in normal RWPE-1 cells as compared to cancerous androgen-responsive LNCaP and androgen insensitive PC-3 cells. HN1 overexpression resulted in differential response for cell proliferation and cell cycle changes in RWPE-1, LNCaP, and PC-3 cells. Since HN1 overexpression increased the proliferation rate in PC-3 cells, these cells were used for functional characterization of HN1 in advanced prostate carcinogenesis. Furthermore, alterations in HN expression led to an increase in abnormal to normal nuclei ratio and increased chromosomal aberrations in PC-3 cells. We observed the co-localization of HN1 with γ-tubulin foci in prostate cancer cells, further validated by immunoprecipitation. HN1 was observed as physically associated with γ-tubulin and its depletion led to increased γ-tubulin foci and disruption in microtubule spindle assembly. Higher HN1 expression was correlated with prostate cancer as compared to normal tissues. The restoration of HN1 expression after silencing suggested that it has a role in centrosome clustering, implicating a potential role of HN1 in cell division as well as in prostate carcinogenesis warranting further studies.

Phospho-β-catenin expression in primary and metastatic melanomas and in tumor-free visceral tissues, and associations with expression of PD-L1 and PD-L2

β-catenin (βcat) is an important downstream effector in the Wnt signaling pathway and plays important roles in the development and progression of many cancers including melanoma. βcat expression is regulated by GSK-3β-mediated phosphorylation at positions 33, 37 and 41. In normal cells, phosphorylation at these sites triggers proteasomal degradation, which prevents accumulation of free cytoplasmic βcat. In cancer cells, stabilized β-catenin translocates into the nucleus, where it associates with TCF/Lef proteins to activate transcription of genes that promote tumorigenesis and metastasis, including PD-L1. It has been suggested that nuclear phospho-βcat (pβcat) staining may be diagnostically useful in differentiating primary from metastatic melanoma. Also, a pβcat peptide (residues 30-39, with only S33 phosphorylated) is naturally presented by melanoma cells as a T-cell target. We evaluated expression of pS33-βcat in primary and metastatic melanomas by immunohistochemistry and found its expression varied widely but was most commonly cytoplasmic. Nuclear staining was identified in only 18% of metastatic melanomas. Staining with antibodies to pS33-βcat and pS33/37/T41-βcat was most intense in mitotic melanoma cells; however, pS33-βcat intensity was not significantly associated with AJCC stage, tumor location, BRAF mutation status, or immune infiltrates. Yet, PD-L1 and PD-L2 expression by tumor cells were significantly higher in tumors with high pS33-βcat expression. The low rate of nuclear pS33-βcat expression suggests that pS33-βcat may have limited utility for identifying metastatic melanomas. However, high expression in dividing cells and strong associations with PD-L1 and PD-L2 expression may inform future personalized therapies for tumors with high pS33-βcat expression.

Mutant Presenilin 1 Dysregulates Exosomal Proteome Cargo Produced by Human-Induced Pluripotent Stem Cell Neurons

The accumulation and propagation of hyperphosphorylated tau (p-Tau) is a neuropathological hallmark occurring with neurodegeneration of Alzheimer's disease (AD). Extracellular vesicles, exosomes, have been shown to initiate tau propagation in the brain. Notably, exosomes from human-induced pluripotent stem cell (iPSC) neurons expressing the AD familial A246E mutant form of presenilin 1 (mPS1) are capable of inducing tau deposits in the mouse brain after in vivo injection. To gain insights into the exosome proteome cargo that participates in propagating tau pathology, this study conducted proteomic analysis of exosomes produced by human iPSC neurons expressing A246E mPS1. Significantly, mPS1 altered the profile of exosome cargo proteins to result in (1) proteins present only in mPS1 exosomes and not in controls, (2) the absence of proteins in the mPS1 exosomes which were present only in controls, and (3) shared proteins which were upregulated or downregulated in the mPS1 exosomes compared to controls. These results show that mPS1 dysregulates the proteome cargo of exosomes to result in the acquisition of proteins involved in the extracellular matrix and protease functions, deletion of proteins involved in RNA and protein translation systems along with proteasome and related functions, combined with the upregulation and downregulation of shared proteins, including the upregulation of amyloid precursor protein. Notably, mPS1 neuron-derived exosomes displayed altered profiles of protein phosphatases and kinases involved in regulating the status of p-tau. The dysregulation of exosome cargo proteins by mPS1 may be associated with the ability of mPS1 neuron-derived exosomes to propagate tau pathology.

PLK4-phosphorylated NEDD1 facilitates cartwheel assembly and centriole biogenesis initiations

Centrosome duplication occurs under strict spatiotemporal regulation once per cell cycle, and it begins with cartwheel assembly and daughter centriole biogenesis at the lateral sites of the mother centrioles. However, although much of this process is understood, how centrosome duplication is initiated remains unclear. Here, we show that cartwheel assembly followed by daughter centriole biogenesis is initiated on the NEDD1-containing layer of the pericentriolar material (PCM) by the recruitment of SAS-6 to the mother centriole under the regulation of PLK4. We found that PLK4-mediated phosphorylation of NEDD1 at its S325 amino acid residue directly promotes both NEDD1 binding to SAS-6 and recruiting SAS-6 to the centrosome. Overexpression of phosphomimicking NEDD1 mutant S325E promoted cartwheel assembly and daughter centriole biogenesis initiations, whereas overexpression of nonphosphorylatable NEDD1 mutant S325A abolished the initiations. Collectively, our results demonstrate that PLK4-regulated NEDD1 facilitates initiation of the cartwheel assembly and of daughter centriole biogenesis in mammals.

The Nek2 centrosome-mitotic kinase contributes to the mesenchymal state, cell invasion, and migration of triple-negative breast cancer cells

Nek2 (NIMA-related kinase 2) is a serine/threonine-protein kinase that localizes to centrosomes and kinetochores, controlling centrosome separation, chromosome attachments to kinetochores, and the spindle assembly checkpoint. These processes prevent centrosome amplification (CA), mitotic dysfunction, and chromosome instability (CIN). Our group and others have suggested that Nek2 maintains high levels of CA/CIN, tumor growth, and drug resistance. We identified that Nek2 overexpression correlates with poor survival of breast cancer. However, the mechanisms driving these phenotypes are unknown. We now report that overexpression of Nek2 in MCF10A cells drives CA/CIN and aneuploidy. Besides, enhanced levels of Nek2 results in larger 3D acinar structures, but could not initiate tumors in a p53+/+ or a p53-/- xenograft model. Nek2 overexpression induced the epithelial-to-mesenchymal transition (EMT) while its downregulation reduced the expression of the mesenchymal marker vimentin. Furthermore, either siRNA-mediated downregulation or INH6's chemical inhibition of Nek2 in MDA-MB-231 and Hs578t cells showed important EMT changes and decreased invasion and migration. We also showed that Slug and Zeb1 are involved in Nek2 mediated EMT, invasion, and migration. Besides its role in CA/CIN, Nek2 contributes to breast cancer progression through a novel EMT mediated mechanism.

Overlapping roles for PLK1 and Aurora A during meiotic centrosome biogenesis in mouse spermatocytes

The establishment of bipolar spindles during meiotic divisions ensures faithful chromosome segregation to prevent gamete aneuploidy. We analyzed centriole duplication, as well as centrosome maturation and separation during meiosis I and II using mouse spermatocytes. The first round of centriole duplication occurs during early prophase I, and then, centrosomes mature and begin to separate by the end of prophase I to prime formation of bipolar metaphase I spindles. The second round of centriole duplication occurs at late anaphase I, and subsequently, centrosome separation coordinates bipolar segregation of sister chromatids during meiosis II. Using a germ cell-specific conditional knockout strategy, we show that Polo-like kinase 1 and Aurora A kinase are required for centrosome maturation and separation prior to metaphase I, leading to the formation of bipolar metaphase I spindles. Furthermore, we show that PLK1 is required to block the second round of centriole duplication and maturation until anaphase I. Our findings emphasize the importance of maintaining strict spatiotemporal control of cell cycle kinases during meiosis to ensure proficient centrosome biogenesis and, thus, accurate chromosome segregation during spermatogenesis.

Phospho-regulation of mitotic spindle assembly

The assembly of the bipolar mitotic spindle requires the careful orchestration of a myriad of enzyme activities like protein posttranslational modifications. Among these, phosphorylation has arisen as the principle mode for spatially and temporally activating the proteins involved in early mitotic spindle assembly processes. Here, we review key kinases, phosphatases, and phosphorylation events that regulate critical aspects of these processes. We highlight key phosphorylation substrates that are important for ensuring the fidelity of centriole duplication, centrosome maturation, and the establishment of the bipolar spindle. We also highlight techniques used to understand kinase-substrate relationships and to study phosphorylation events. We conclude with perspectives on the field of posttranslational modifications in early mitotic spindle assembly.

A look into the link between centrosome amplification and breast cancer

Centrosome amplification (CA) is a common feature of human tumors, but it is not clear whether this is a cause or a consequence of cancer. The centrosome amplification observed in tumor cells may be explained by a series of events, such as failure of cell division, dysregulation of centrosome cycle checkpoints, and de novo centriole biogenesis disorder. The formation and progression of breast cancer are characterized by genomic abnormality. The centrosomes in breast cancer cells show characteristic structural aberrations, caused by centrosome amplification, which include: an increase in the number and volume of centrosomes, excessive increase of pericentriolar material (PCM), inappropriate phosphorylation of centrosomal molecular, and centrosome clustering formation induced by the dysregulation of important genes. The mechanism of intracellular centrosome amplification, the impact of which on breast cancer and the latest breast cancer target treatment options for centrosome amplification are exhaustively elaborated in this review.

Principal Postulates of Centrosomal Biology. Version 2020

The centrosome, which consists of two centrioles surrounded by pericentriolar material, is a unique structure that has retained its main features in organisms of various taxonomic groups from unicellular algae to mammals over one billion years of evolution. In addition to the most noticeable function of organizing the microtubule system in mitosis and interphase, the centrosome performs many other cell functions. In particular, centrioles are the basis for the formation of sensitive primary cilia and motile cilia and flagella. Another principal function of centrosomes is the concentration in one place of regulatory proteins responsible for the cell's progression along the cell cycle. Despite the existing exceptions, the functioning of the centrosome is subject to general principles, which are discussed in this review.

Live imaging of hair bundle polarity acquisition demonstrates a critical timeline for transcription factor Emx2

Directional sensitivity of hair cells (HCs) is conferred by the aymmetric apical hair bundle, comprised of a kinocilium and stereocilia staircase. The mother centriole (MC) forms the base of the kinocilium and the stereocilia develop adjacent to it. Previously, we showed that transcription factor Emx2 reverses hair bundle orientation and its expression in the mouse vestibular utricle is restricted, resulting in two regions of opposite bundle orientation (Jiang et al., 2017). Here, we investigated establishment of opposite bundle orientation in embryonic utricles by live-imaging GFP-labeled centrioles in HCs. The daughter centriole invariably migrated ahead of the MC from the center to their respective peripheral locations in HCs. Comparing HCs between utricular regions, centriole trajectories were similar but they migrated toward opposite directions, suggesting that Emx2 pre-patterned HCs prior to centriole migration. Ectopic Emx2, however, reversed centriole trajectory within hours during a critical time-window when centriole trajectory was responsive to Emx2.

Design, synthesis, and structure activity relationship (SAR) studies of novel imidazo[1,2-a] pyridine derivatives as Nek2 inhibitors

Never in mitosis (NIMA) related kinase 2 (Nek2) is involved in multiple cellular processes such as cell cycle checkpoint regulation, cell division, DNA damage response and cell apoptosis. Nek2 has been reported to be overexpressed in various tumors and correlated with poor prognosis. Herein, a series of imidazo[1,2-a] pyridines Nek2 inhibitors were designed, synthesized, and their biological activities were investigated. Besides, structure activity relationship analysis of these compounds were performed in the MGC-803 cell. The screening results are promising, and compound 28e shows good proliferation inhibitory activity with an IC₅₀ of 38 nM. The results would be helpful to design and develop more effective Nek2 inhibitors for the treatment of gastric cancer.

Regulation of myonuclear positioning and muscle function by the skeletal muscle-specific CIP protein

The appropriate arrangement of myonuclei within skeletal muscle myofibers is of critical importance for normal muscle function, and improper myonuclear localization has been linked to a variety of skeletal muscle diseases, such as centronuclear myopathy and muscular dystrophies. However, the molecules that govern myonuclear positioning remain elusive. Here, we report that skeletal muscle-specific CIP (sk-CIP) is a regulator of nuclear positioning. Genetic deletion of sk-CIP in mice results in misalignment of myonuclei along the myofibers and at specialized structures such as neuromuscular junctions (NMJs) and myotendinous junctions (MTJs) in vivo, impairing myonuclear positioning after muscle regeneration, leading to severe muscle dystrophy in mdx mice, a mouse model of Duchenne muscular dystrophy. sk-CIP is localized to the centrosome in myoblasts and relocates to the outer nuclear envelope in myotubes upon differentiation. Mechanistically, we found that sk-CIP interacts with the Linker of Nucleoskeleton and Cytoskeleton (LINC) complex and the centriole Microtubule Organizing Center (MTOC) proteins to coordinately modulate myonuclear positioning and alignment. These findings indicate that sk-CIP may function as a muscle-specific anchoring protein to regulate nuclear position in multinucleated muscle cells.

High expression of NEK2 promotes lung cancer progression and drug resistance and is regulated by mutant EGFR

Activating mutations within the tyrosine kinase (TK) domain of epidermal growth factor receptor (EGFR) gene are observed in 10 ~ 30% of the patients diagnosed with non-small cell lung cancer (NSCLC), and are causally related to NSCLC initiation and progression. Treatments with tyrosine kinase inhibitors (TKIs) targeting EGFR significantly improve the outcome of NSCLC patients with EGFR mutation, but are often associated with drug resistance, which is the main cause of treatment failure and cancer relapse. In the present study, by screening the transcriptome of NSCLC patients, we found that EGFR activation is highly correlated with the up-regulation of mitotic regulator, never in mitosis gene A-related kinase 2 (NEK2). NEK2 overexpression is associated with the poor survival of EGFR-mutant patients but not the wild-type patients. Further functional validation revealed that EGFR mutation induces NEK2 expression by activating ERK signaling pathway. Elevated NEK2 level promotes the rapid cell cycle progression and favors the rapid proliferation of EGFR-mutant NSCLC cells. Of note, NEK2 overexpression also impairs the efficacy of TKI treatment via inhibiting apoptosis, while depleting NEK2 suppresses cell growth and restored the sensitivity of TKI in NSCLC cells. Taken together, our study revealed that NEK2 is an oncogene regulated by EGFR mutation and is involved in disease progression and treatment response in NSCLC with EGFR mutation. These findings will pave the road for optimizing personalized treatment strategies to overcome drug resistance and improve the prognosis of lung cancer patients with EGFR mutation.

Single-cell RNA-seq analysis revealed long-lasting adverse effects of tamoxifen on neurogenesis in prenatal and adult brains

The CreER/LoxP system is widely accepted to track neural lineages and study gene functions upon tamoxifen (TAM) administration. We have observed that prenatal TAM treatment caused high rates of delayed delivery and fetal mortality. This substance could produce undesired results, leading to data misinterpretation. Here, we report that administration of TAM during early stages of cortical neurogenesis promoted precocious neural differentiation, while it inhibited neural progenitor cell (NPC) proliferation. The TAM-induced inhibition of NPC proliferation led to deficits in cortical neurogenesis, dendritic morphogenesis, synaptic formation, and cortical patterning in neonatal and postnatal offspring. Mechanistically, by employing single-cell RNA-sequencing (scRNA-seq) analysis combined with in vivo and in vitro assays, we show TAM could exert these drastic effects mainly through dysregulating the Wnt-Dmrta2 signaling pathway. In adult mice, administration of TAM significantly attenuated NPC proliferation in both the subventricular zone and the dentate gyrus. This study revealed the cellular and molecular mechanisms for the adverse effects of TAM on corticogenesis, suggesting that care must be taken when using the TAM-induced CreER/LoxP system for neural lineage tracing and genetic manipulation studies in both embryonic and adult brains.

FAM110B Inhibits Non-Small Cell Lung Cancer Cell Proliferation and Invasion Through Inactivating Wnt/β-Catenin Signaling

PURPOSE

FAM110B is a member of the FAM110 family (family with sequence similarity 110), which is a component of the centrosome associated proteins. Previous studies have shown that FAM110B may be involved in the process of cell cycle and may play a role in carcinogenesis and tumor progression. Using an online database, we found that FAM110B may predict favorable prognosis in non-small cell lung cancer (NSCLC). Therefore, the role of FAM110B playing in NSCLC needs to be further investigated.

PATIENTS AND METHODS

Online databases and immunohistochemistry were used to predict the expression and prognostic value of FAM110B in NSCLC samples. Immunofluorescence staining was used to investigate the subcellular distribution of FAM110B. Western blot, MTT, colony formation, and matrigel invasion assay were used to detect the expression and the effect of FAM110B on mediating proliferation and invasion in NSCLC cell lines.

RESULTS

In this study, immunohistochemistry results showed that FAM110B expression significantly correlated with early TNM staging (P=0.020) and negative regional lymph node metastasis (P=0.006). Kaplan-Meier survival analysis found that the median survival time of patients with positive FAM110B expression (56.181±2.348 months) was significantly longer than those with negative FAM110B expression (47.701±2.997 months, P=0.024). Moreover, overexpression of FAM110B inhibited the proliferation and invasion of A549, H1299, and LK2 cell lines. Conversely, FAM110B RNAi exerted opposite effects in the above cell lines. Furthermore, FAM110B overexpression downregulated the active β-catenin, phosphorylation of GSK-3β (p-GSK-3β), cyclin B1, cyclin D1, MMP2, and MMP7, and upregulated the phosphorylation of β-catenin (p-β-catenin) in A549 and H1299 cells. Besides, the FAM110B-induced depressions of p-GSK-3β and active β-catenin were reversed after being treated with Wnt/β-catenin inhibitor, XAV-939.

CONCLUSION

In summary, our results demonstrated that the overexpression of FAM110B restricts the proliferation and invasion of NSCLC cells by inhibiting Wnt/β-catenin signaling. Our study reveals the antitumor function of FAM110B in NSCLC and indicates that FAM110B is a potential therapeutic target.

Zika virus NS5 localizes at centrosomes during cell division

Zika virus (ZIKV) nonstructural protein 5 (NS5) plays a critical role in viral RNA replication and mediates key virus-host cell interactions. As with other flavivirus NS5 proteins, ZIKV NS5 is primarily found in the nucleus. We previously reported that the NS5 protein of dengue virus, another flavivirus, localized to centrosomes during cell division. Here we show that ZIKV NS5 also relocalizes from the nucleus to centrosomes during mitosis. In infected cells with supernumerary centrosomes, NS5 was present at all centrosomes. Transient expression of NS5 in uninfected cells confirmed that centrosomal localization was independent of other viral proteins. Live-cell imaging demonstrated that NS5-GFP accumulated at centrosomes shortly after break down of nuclear membrane and remained there through mitosis. Cells expressing NS5-GFP took longer to complete mitosis than control cells. Finally, an analysis of ZIKV NS5 binding partners revealed several centrosomal proteins, providing potential direct links between NS5 and centrosomes.

Re-enforcing hypoxia-induced polyploid cardiomyocytes enter cytokinesis through activation of β-catenin

Cardiomyocyte (CM) loss is a characteristic of various heart diseases, including ischaemic heart disease. Cardiac regeneration has been suggested as a promising strategy to address CM loss. Although many studies of regeneration have focused mainly on mononucleated or diploid CM, the limitations associated with the cytokinesis of polyploid and multinucleated CMs remain less well known. Here, we show that β-catenin, a key regulator in heart development, can increase cytokinesis in polyploid multinucleated CMs. The activation of β-catenin increases the expression of the cytokinesis-related factor epithelial cell transforming 2 (ECT2), which regulates the actomyosin ring and thus leads to the completion of cytokinesis in polyploid CMs. In addition, hypoxia can induce polyploid and multinucleated CMs by increasing factors related to the G1-S-anaphase of the cell cycle, but not those related to cytokinesis. Our study therefore reveals that the β-catenin can promote the cytokinesis of polyploid multinucleated CMs via upregulation of ECT2. These findings suggest a potential field of polyploid CM research that may be exploitable for cardiac regeneration therapy.

Nek2 augments sorafenib resistance by regulating the ubiquitination and localization of β-catenin in hepatocellular carcinoma

BACKGROUND

Sorafenib is the first-line treatment for advanced-stage hepatocellular carcinoma (HCC). Several studies have shown that the up-regulation of β-catenin plays a role in sorafenib resistance in HCC; however, the mechanism associated with this phenomenon remains elusive.

METHODS

Western blotting, flow cytometry, and an evaluation of IC50 values were used to confirm the role of β-catenin in HCC sorafenib resistance. Immunoprecipitation and western blotting were then performed to identify regulatory interactions between β-catenin and Nek2. Further, western blotting, flow cytometry, and an in vivo xenograft model were used to evaluate the function of Nek2 in HCC sorafenib resistance, whereas rescue experiments were performed to confirm that Nek2 induces sorafenib resistance via β-catenin. Finally, western blotting and immunohistochemistry were used to evaluate the expression level of Nek2 in paired HCC and non-tumor tissues.

RESULTS

We showed that β-catenin could suppress sorafenib-induced apoptosis and cell growth inhibition in HCC cell lines. By screening β-catenin-interacting proteins, we found that Nek2 could bind β-catenin in sorafenib-treated HCC cell lines. Our results also showed that Nek2 stabilizes β-catenin and promotes its translocation to the nucleus, consequently activating the transcription of downstream target genes. We further confirmed that Nek2 could induce sorafenib resistance in HCC cell lines, and that β-catenin was the key element involved in this process. Further, a xenograft tumor model showed that Nek2 knockdown could improve the anti-tumor effect of sorafenib, whereas an analysis of tumor proteins showed that Nek2 regulates β-catenin protein levels and its nuclear translocation in vivo. In addition, Nek2 was found to be up-regulated in HCC tissue, and especially in advanced-stage disease.

CONCLUSIONS

Our study proves that Nek2 induces HCC sorafenib resistance via β-catenin and suggests a novel therapeutic strategy to improve the anti-tumor effects of sorafenib in HCC.

Nek2B activates the wnt pathway and promotes triple-negative breast cancer chemothezrapy-resistance by stabilizing β-catenin

Background

The chemotherapy-resistance of triple-negative breast cancer (TNBC) remains a major challenge. The Nek2B kinase and β-catenin serve as crucial regulators of mitotic processes. The aim of this study was to test the correlation between Nek2B and TNBC chemotherapy sensitivity, and to determine the regulation of Nek2B on β-catenin and wnt/β-catenin signal pathway.

Methods

Gene Expression Omnibus(GEO) databases were used to gather gene exprsssion data of TNBC patients who undergoing chemotherapy. The co-expression of Nek2B and β-catenin in TNBC surgical sections and cells were analysed by immunohistochemistry, Q-RT-PCR, Western-blot and immunofluorescent staining. The impact of the expression of Nek2B and β-catenin in prognosis was also assessed using the Kaplan-Meier curves. CCK8 assay was used to detect the IC50 value of TNBC cell line. The endogenous binding capacity of Nek2B and β-catenin and phosphorylation of β-catenin by Nek2B were detected using co-immunoprecipitation (CO-IP). Chromatin immune-precipitation (ChIP) analysis and Luciferase Assays were used to evaluate the binding ability of the Nek2B, β-catenin and TCF4 complex with LEF-1 promoter. Nek2B-siRNA and Nek2B plasmid were injected into nude mice, and tumorigenesis was monitored.

Results

We found that overexpression of Nek2B and β-catenin in TNBC samples, was associated with patients poor prognosis. Patients with positive Nek2B expression were less sensitive to paclitaxel-containing neoadjuvant chemotherapy. Interestingly, in a panel of established TNBC cell line, Nek2B and β-catenin were highly expressed in cells exhibiting paclitaxel resistance. Our data also suggest that β-catenin binded to and was phosphorylated by Nek2B, and was in a complex with TCF4. Nek2B mainly regulates the expression of β-catenin in TNBC nucleus. Nek2B, β-catenin and TCF4 can be binded with the WRE functional area of LEF-1 promoter. Nek2B can activite wnt signaling pathway and wnt downstream target genes. The tumors treated by Nek2B siRNA associated with paclitaxel were the smallest in nude mouse, and Nek2B can regulate the expression of β-catenin and wnt downstream target genes in vivo.

Conclusion

Our study suggested that Nek2B can bind to β-catenin and the co-expression correlated with TNBC patients poor prognosis. It appears that Nek2B and β-catenin might synergize to promote chemotherapy resistance.

Presence of aggregates of smooth endoplasmic reticulum in MII oocytes affects oocyte competence: molecular-based evidence

STUDY QUESTION

Does the presence of aggregates of smooth endoplasmic reticulum (SERa) impact the transcriptome of human metaphase II (MII) oocytes?.

SUMMARY ANSWER

The presence of SERa alters the molecular status of human metaphase II oocytes.

WHAT IS KNOWN ALREADY

Oocytes presenting SERa are considered dysmorphic. Oocytes with SERa (SERa+) have been associated with reduced embryological outcome and increased risk of congenital anomalies, although some authors have reported that SERa+ oocytes can lead to healthy newborns. The question of whether or not SERa+ oocytes should be discarded is still open for debate, and no experimental information about the effect of the presence of SERa on the oocyte molecular status is available.

STUDY DESIGN, SIZE, DURATION

This study included 28 women, aged <38 years, without any ovarian pathology, and undergoing IVF treatment. Supernumerary MII oocytes with no sign of morphological alterations as well as SERa+ oocytes were donated after written informed consent. A total of 31 oocytes without SERa (SERa-) and 24 SERa+ oocytes were analyzed.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Pools of 8-10 oocytes for both group were prepared. Total RNA was extracted from each pool, amplified, labeled and hybridized on oligonucleotide microarrays. Analyses were performed by R software using the limma package.

MAIN RESULTS AND THE ROLE OF CHANCE

The expression profiles of SERa+ oocytes significantly differed from those of SERa- oocytes in 488 probe sets corresponding to 102 down-regulated and 283 up-regulated unique transcripts. Gene Ontology analysis by DAVID bioinformatics disclosed that genes involved in three main biological processes were significantly down-regulated in SERa+ oocytes respective to SERa- oocytes: (i) cell and mitotic/meiotic nuclear division, spindle assembly, chromosome partition and G2/M transition of mitotic cell cycle; (ii) organization of cytoskeleton and microtubules; and (iii) mitochondrial structure and activity. Among the transcripts up-regulated in SERa+ oocytes, the most significantly (P = 0.002) enriched GO term was 'GoLoco motif', including the RAP1GAP, GPSM3 and GPSM1 genes.

LARGE SCALE DATA

Raw microarray data are accessible through GEO Series accession number GSE106222 (https://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE106222).

LIMITATIONS, REASONS FOR CAUTION

Data validation in a larger cohort of samples would be beneficial, although we applied stringent criteria for gene selection (fold-change >3 or <1/3 and FDR < 0.1). Surveys on clinical outcomes, malformation rates and follow-up of babies born after transfer of embryos from SERa+ oocytes are necessary.

WIDER IMPLICATIONS OF THE FINDINGS

We provide information on the molecular status of SERa+ oocytes, highlighting possible associations between presence of SERa, altered oocyte physiology and reduced developmental competence. Our study may offer further information that can assist embryologists to make decisions on whether, and with what possible implications, SERa+ oocytes should be used. We believe that the presence of SERa should be still a 'red flag' in IVF practices and that the decision to inseminate SERa+ oocytes should be discussed on a case-by-case basis.

STUDY FUNDING/COMPETING INTEREST(s)

This study was partially supported by Ferring Pharmaceuticals. The authors have no conflicts of interest to declare.

Role of β-Catenin Activation Levels and Fluctuations in Controlling Cell Fate

Cells have developed numerous adaptation mechanisms to external cues by controlling signaling-pathway activity, both qualitatively and quantitatively. The Wnt/β-catenin pathway is a highly conserved signaling pathway involved in many biological processes, including cell proliferation, differentiation, somatic cell reprogramming, development, and cancer. The activity of the Wnt/β-catenin pathway and the temporal dynamics of its effector β-catenin are tightly controlled by complex regulations. The latter encompass feedback loops within the pathway (e.g., a negative feedback loop involving Axin2, a β-catenin transcriptional target) and crosstalk interactions with other signaling pathways. Here, we provide a review shedding light on the coupling between Wnt/β-catenin activation levels and fluctuations across processes and cellular systems; in particular, we focus on development, in vitro pluripotency maintenance, and cancer. Possible mechanisms originating Wnt/β-catenin dynamic behaviors and consequently driving different cellular responses are also reviewed, and new avenues for future research are suggested.

Cancer upregulated gene (CUG)2 elevates YAP1 expression, leading to enhancement of epithelial-mesenchymal transition in human lung cancer cells

Although our previous studies have showed that a novel oncogene, cancer upregulated gene (CUG)2 induced epithelial-mesenchymal transition (EMT), the detailed molecular mechanism remains unknown. Because several lines of evidence documented that Yes-Associated Protein (YAP)1 is closely associated with cancer stem cell (CSC)-like phenotypes including EMT, stemness, and drug resistance, we wondered if YAP1 is involved in CUG2-induced EMT. We herein found that the overexpression of CUG2 increased YAP1 expression at the transcriptional as well as protein levels. Chromatin immunoprecipitation assay revealed that the elevated YAP1 transcripts are attributed to c-Jun and AP2 bindings to the YAP1 promoter. Akt and MAPK kinases including ERK, JNK, and p38 MAPK enhanced the level of YAP1 protein. In spite of a close relationship between β-catenin and YAP1, not β-catenin but NEK2 played the role in increasing YAP1 expression. Silencing YAP1 inhibited CUG2-induced cell migration and invasion. N-cadherin and vimentin expressions were decreased during YAP1 knockdown. The suppression of YAP1 diminished TGF-β transcriptional activity and expression as well as phosphorylation level of Smad2 and Twist protein. Conversely, LY2109761 or Smad2 siRNA treatment reduced YAP1 protein levels, indicating a close interplay between YAP1 and TGF-β signaling. Taken together, we suggest that CUG2 induces up-regulation of YAP1 expression, leading to enhancing CUG2-induced EMT via a close crosstalk between YAP1 and TGF-β signaling.

Phosphatases in Mitosis: Roles and Regulation

Mitosis requires extensive rearrangement of cellular architecture and of subcellular structures so that replicated chromosomes can bind correctly to spindle microtubules and segregate towards opposite poles. This process originates two new daughter nuclei with equal genetic content and relies on highly-dynamic and tightly regulated phosphorylation of numerous cell cycle proteins. A burst in protein phosphorylation orchestrated by several conserved kinases occurs as cells go into and progress through mitosis. The opposing dephosphorylation events are catalyzed by a small set of protein phosphatases, whose importance for the accuracy of mitosis is becoming increasingly appreciated. This review will focus on the established and emerging roles of mitotic phosphatases, describe their structural and biochemical properties, and discuss recent advances in understanding the regulation of phosphatase activity and function.

CCDC102B functions in centrosome linker assembly and centrosome cohesion

The proteinaceous centrosome linker is an important structure that allows the centrosome to function as a single microtubule-organizing center (MTOC) in interphase cells. However, the assembly mechanism of the centrosome linker components remains largely unknown. In this study, we identify CCDC102B as a new centrosome linker protein that is required for maintaining centrosome cohesion. CCDC102B is recruited to the centrosome by C-Nap1 (also known as CEP250) and interacts with the centrosome linker components rootletin and LRRC45. CCDC102B decorates and facilitates the formation of rootletin filaments. Furthermore, CCDC102B is phosphorylated by Nek2A (an isoform encoded by NEK2) and is disassociated from the centrosome at the onset of mitosis. Together, our findings reveal a molecular role for CCDC102B in centrosome cohesion and centrosome linker assembly.This article has an associated First Person interview with the first authors of the paper.