The Nek2 protein kinase: a novel regulator of centrosome structure

NEK2 contributes to radioresistance in esophageal squamous cell carcinoma by inducing protective autophagy via regulating TRIM21

BACKGROUND

Radiotherapy (RT) has been identified as a vital treatment for esophageal squamous cell carcinoma (ESCC), while the development of radioresistance remains a major obstacle in ESCC management. The aim of this study was to investigate the effect of NIMA-related kinase 2 (NEK2) on radioresistance in ESCC cells and to reveal potential molecular mechanisms.

METHODS

Human esophageal epithelial cells (HEEC) and human ESCC cell lines were obtained from the Research Center of the Fourth Hospital of Hebei Medical University (Shijiazhuang, China). Cell Counting Kit-8 (CCK-8) and flow cytometry assays were applied to assess the proliferation ability, cell cycle, apoptosis rates, and ROS production of ESCC cells. The colony-forming assay was used to estimate the effect of NEK2 on radiosensitivity. Autophagy was investigated by western blotting analysis, GFP-mRFP-LC3 fluorescence assay, and transmission electron microscopy (TEM).

RESULTS

In the present study, our results showed that NEK2 was associated with radioresistance, cell cycle arrest, apoptosis, ROS production, and survival of ESCC. NEK2 knockdown could significantly inhibit growth while enhancing radiosensitivity and ROS production in ESCC cells. Interestingly, NEK2 knockdown inhibited ESCC cell autophagy and reduced autophagic flux, ultimately reversing NEK2-induced radioresistance. Mechanistically, NEK2 bound to and regulated the stability of tripartite motif-containing protein 21 (TRIM21). The accumulation of NEK2-induced light chain 3 beta 2 (LC3B II) can be reversed by the knockdown of TRIM21.

CONCLUSION

These results demonstrated that NEK2 activated autophagy through TRIM21, which may provide a promising therapeutic strategy for elucidating NEK2-mediated radioresistance in ESCC.

Nek2A prevents centrosome clustering and induces cell death in cancer cells via KIF2C interaction

Unlike normal cells, cancer cells frequently exhibit supernumerary centrosomes, leading to formation of multipolar spindles that can trigger cell death. Nevertheless, cancer cells with supernumerary centrosomes escape the deadly consequences of unequal segregation of genomic material by coalescing their centrosomes into two poles. This unique trait of cancer cells presents a promising target for cancer therapy, focusing on selectively attacking cells with supernumerary centrosomes. Nek2A is a kinase involved in mitotic regulation, including the centrosome cycle, where it phosphorylates linker proteins to separate centrosomes. In this study, we investigated if Nek2A also prevents clustering of supernumerary centrosomes, akin to its separation function. Reduction of Nek2A activity, achieved through knockout, silencing, or inhibition, promotes centrosome clustering, whereas its overexpression results in inhibition of clustering. Significantly, prevention of centrosome clustering induces cell death, but only in cancer cells with supernumerary centrosomes, both in vitro and in vivo. Notably, none of the known centrosomal (e.g., CNAP1, Rootletin, Gas2L1) or non-centrosomal (e.g., TRF1, HEC1) Nek2A targets were implicated in this machinery. Additionally, Nek2A operated via a pathway distinct from other proteins involved in centrosome clustering mechanisms, like HSET and NuMA. Through TurboID proximity labeling analysis, we identified novel proteins associated with the centrosome or microtubules, expanding the known interaction partners of Nek2A. KIF2C, in particular, emerged as a novel interactor, confirmed through coimmunoprecipitation and localization analysis. The silencing of KIF2C diminished the impact of Nek2A on centrosome clustering and rescued cell viability. Additionally, elevated Nek2A levels were indicative of better patient outcomes, specifically in those predicted to have excess centrosomes. Therefore, while Nek2A is a proposed target, its use must be specifically adapted to the broader cellular context, especially considering centrosome amplification. Discovering partners such as KIF2C offers fresh insights into cancer biology and new possibilities for targeted treatment.

The Mitochondrial Connection: The Nek Kinases' New Functional Axis in Mitochondrial Homeostasis

Mitochondria provide energy for all cellular processes, including reactions associated with cell cycle progression, DNA damage repair, and cilia formation. Moreover, mitochondria participate in cell fate decisions between death and survival. Nek family members have already been implicated in DNA damage response, cilia formation, cell death, and cell cycle control. Here, we discuss the role of several Nek family members, namely Nek1, Nek4, Nek5, Nek6, and Nek10, which are not exclusively dedicated to cell cycle-related functions, in controlling mitochondrial functions. Specifically, we review the function of these Neks in mitochondrial respiration and dynamics, mtDNA maintenance, stress response, and cell death. Finally, we discuss the interplay of other cell cycle kinases in mitochondrial function and vice versa. Nek1, Nek5, and Nek6 are connected to the stress response, including ROS control, mtDNA repair, autophagy, and apoptosis. Nek4, in turn, seems to be related to mitochondrial dynamics, while Nek10 is involved with mitochondrial metabolism. Here, we propose that the participation of Neks in mitochondrial roles is a new functional axis for the Nek family.

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.

The Impact of Centrosome Pathologies on Ovarian Cancer Development and Progression with a Focus on Centrosomes as Therapeutic Target

The impact of centrosome abnormalities on cancer cell proliferation has been recognized as early as 1914 (Boveri, Zur Frage der Entstehung maligner Tumoren. Jena: G. Fisher, 1914), but vigorous research on molecular levels has only recently started when it became fully apparent that centrosomes can be targeted for new cancer therapies. While best known for their microtubule-organizing capabilities as MTOC (microtubule organizing center) in interphase and mitosis, centrosomes are now further well known for a variety of different functions, some of which are related to microtubule organization and consequential activities such as cell division, migration, maintenance of cell shape, and vesicle transport powered by motor proteins, while other functions include essential roles in cell cycle regulation, metabolic activities, signal transduction, proteolytic activity, and several others that are now heavily being investigated for their role in diseases and disorders (reviewed in Schatten and Sun, Histochem Cell Biol 150:303-325, 2018; Schatten, Adv Anat Embryol Cell Biol 235:43-50, 2022a; Schatten, Adv Anat Embryol Cell Biol 235:17-35, 2022b).Cancer cell centrosomes differ from centrosomes in noncancer cells in displaying specific abnormalities that include phosphorylation abnormalities, overexpression of specific centrosomal proteins, abnormalities in centriole and centrosome duplication, formation of multipolar spindles that play a role in aneuploidy and genomic instability, and several others that are highlighted in the present review on ovarian cancer. Ovarian cancer cell centrosomes, like those in other cancers, display complex abnormalities that in part are based on the heterogeneity of cells in the cancer tissues resulting from different etiologies of individual cancer cells that will be discussed in more detail in this chapter.Because of the critical role of centrosomes in cancer cell proliferation, several lines of research are being pursued to target centrosomes for therapeutic intervention to inhibit abnormal cancer cell proliferation and control tumor progression. Specific centrosome abnormalities observed in ovarian cancer will be addressed in this chapter with a focus on targeting such aberrations for ovarian cancer-specific therapies.

Behavior of intracellular lipid droplets during cell division in HuH7 hepatoma cells

Intracellular lipid droplets (LDs) are ubiquitous organelles found in many cell types. During mitosis, membranous organelles, including mitochondria, are divided into small pieces and transferred to daughter cells; however, the process of LD transfer to daughter cells is not fully elucidated. Herein, we investigated the behavior of LDs during mitosis in HuH7 human hepatoma cells. While fragments of the Golgi apparatus were scattered in the cytosol during mitosis, intracellular LDs retained their size and spherical morphology as they translocated to the two daughter cells. LDs were initially distributed throughout the cell during prophase but positioned outside the spindle in metaphase, aligning at the far sides of the centrioles. A similar distribution of LDs during mitosis was observed in another hepatocarcinoma HepG2 cells. When the spindle was disrupted by nocodazole treatment or never in mitosis gene A-related kinase 2A knockdown, LDs were localized in the area outside the chromosomes, suggesting that spindle formation is not necessary for LD localization at metaphase. The amount of major LD protein perilipin 2 reduced while LDs were enriched in perilipin 3 during mitosis, indicating the potential alteration of LD protein composition. Conclusively, the behavior of LDs during mitosis is distinct from that of other organelles in hepatocytes.

Phosphate NIMA-Related Kinase 2-Dependent Epigenetic Pathways in Dorsal Root Ganglion Neurons Mediates Paclitaxel-Induced Neuropathic Pain

BACKGROUND

The microtubule-stabilizing drug paclitaxel (PTX) is an important chemotherapeutic agent for cancer treatment and causes peripheral neuropathy as a common side effect that substantially impacts the functional status and quality of life of patients. The mechanistic role for NIMA-related kinase 2 (NEK2) in the progression of PTX-induced neuropathic pain has not been established.

METHODS

Adult male Sprague-Dawley rats intraperitoneally received PTX to induce neuropathic pain. The protein expression levels in the dorsal root ganglion (DRG) of animals were measured by biochemical analyses. Nociceptive behaviors were evaluated by von Frey tests and hot plate tests.

RESULTS

PTX increased phosphorylation of the important microtubule dynamics regulator NEK2 in DRG neurons and induced profound neuropathic allodynia. PTX-activated phosphorylated NEK2 (pNEK2) increased jumonji domain-containing 3 (JMJD3) protein, a histone demethylase protein, to specifically catalyze the demethylation of the repressive histone mark H3 lysine 27 trimethylation (H3K27me3) at the Trpv1 gene, thereby enhancing transient receptor potential vanilloid subtype-1 (TRPV1) expression in DRG neurons. Moreover, the pNEK2-dependent PTX response program is regulated by enhancing p90 ribosomal S6 kinase 2 (RSK2) phosphorylation. Conversely, intrathecal injections of kaempferol (a selective RSK2 activation antagonist), NCL 00017509 (a selective NEK2 inhibitor), NEK2-targeted siRNA, GSK-J4 (a selective JMJD3 inhibitor), or capsazepine (an antagonist of TRPV1 receptor) into PTX-treated rats reversed neuropathic allodynia and restored silencing of the Trpv1 gene, suggesting the hierarchy and interaction among phosphorylated RSK2 (pRSK2), pNEK2, JMJD3, H3K27me3, and TRPV1 in the DRG neurons in PTX-induced neuropathic pain.

CONCLUSIONS

pRSK2/JMJD3/H3K27me3/TRPV1 signaling in the DRG neurons plays as a key regulator for PTX therapeutic approaches.

Breaking barriers: NEK2 inhibition shines in multiple myeloma treatment

In their article, Cheng et al.1 reveal that NEK2 loss reshapes the tumor microenvironment, reducing tumor-associated macrophages and decreasing T cell exhaustion. They show that this ultimately favors the immune system's anti-cancer response in multiple myeloma.

Sexual Dimorphism of the Mouse Plasma Metabolome Is Associated with Phenotypes of 30 Gene Knockout Lines

Although metabolic alterations are observed in many monogenic and complex genetic disorders, the impact of most mammalian genes on cellular metabolism remains unknown. Understanding the effect of mouse gene dysfunction on metabolism can inform the functions of their human orthologues. We investigated the effect of loss-of-function mutations in 30 unique gene knockout (KO) lines on plasma metabolites, including genes coding for structural proteins (11 of 30), metabolic pathway enzymes (12 of 30) and protein kinases (7 of 30). Steroids, bile acids, oxylipins, primary metabolites, biogenic amines and complex lipids were analyzed with dedicated mass spectrometry platforms, yielding 827 identified metabolites in male and female KO mice and wildtype (WT) controls. Twenty-two percent of 23,698 KO versus WT comparison tests showed significant genotype effects on plasma metabolites. Fifty-six percent of identified metabolites were significantly different between the sexes in WT mice. Many of these metabolites were also found to have sexually dimorphic changes in KO lines. We used plasma metabolites to complement phenotype information exemplified for Dhfr, Idh1, Mfap4, Nek2, Npc2, Phyh and Sra1. The association of plasma metabolites with IMPC phenotypes showed dramatic sexual dimorphism in wildtype mice. We demonstrate how to link metabolomics to genotypes and (disease) phenotypes. Sex must be considered as critical factor in the biological interpretation of gene functions.

Conserved NIMA kinases regulate multiple steps of endocytic trafficking

Human NIMA-related kinases have primarily been studied for their roles in cell cycle progression (NEK1/2/6/7/9), checkpoint-DNA-damage control (NEK1/2/4/5/10/11), and ciliogenesis (NEK1/4/8). We previously showed that Caenorhabditis elegans NEKL-2 (NEK8/9 homolog) and NEKL-3 (NEK6/7 homolog) regulate apical clathrin-mediated endocytosis (CME) in the worm epidermis and are essential for molting. Here we show that NEKL-2 and NEKL-3 also have distinct roles in controlling endosome function and morphology. Specifically, loss of NEKL-2 led to enlarged early endosomes with long tubular extensions but showed minimal effects on other compartments. In contrast, NEKL-3 depletion caused pronounced defects in early, late, and recycling endosomes. Consistently, NEKL-2 was strongly localized to early endosomes, whereas NEKL-3 was localized to multiple endosomal compartments. Loss of NEKLs also led to variable defects in the recycling of two resident cargoes of the trans-Golgi network (TGN), MIG-14/Wntless and TGN-38/TGN38, which were missorted to lysosomes after NEKL depletion. In addition, defects were observed in the uptake of clathrin-dependent (SMA-6/Type I BMP receptor) and independent cargoes (DAF-4/Type II BMP receptor) from the basolateral surface of epidermal cells after NEKL-2 or NEKL-3 depletion. Complementary studies in human cell lines further showed that siRNA knockdown of the NEKL-3 orthologs NEK6 and NEK7 led to missorting of the mannose 6-phosphate receptor from endosomes. Moreover, in multiple human cell types, depletion of NEK6 or NEK7 disrupted both early and recycling endosomal compartments, including the presence of excess tubulation within recycling endosomes, a defect also observed after NEKL-3 depletion in worms. Thus, NIMA family kinases carry out multiple functions during endocytosis in both worms and humans, consistent with our previous observation that human NEKL-3 orthologs can rescue molting and trafficking defects in C. elegans nekl-3 mutants. Our findings suggest that trafficking defects could underlie some of the proposed roles for NEK kinases in human disease.

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.

In silico analysis revealed the potential circRNA-miRNA-mRNA regulative network of non-small cell lung cancer (NSCLC)

BACKGROUND

The primary source of death in the world is non-small cell lung cancer (NSCLC). However, NSCLCs pathophysiology is still not completely understood. The current work sought to study the differential expression of mRNAs involved in NSCLC and their interactions with miRNAs and circRNAs.

METHODS

We utilized three microarray datasets (GSE21933, GSE27262, and GSE33532) from the GEO NCBI database to identify the differentially expressed genes (DEGs) in NSCLC. We employed DAVID Functional annotation tool to investigate the underlying GO biological process, molecular functions, and KEGG pathways involved in NSCLC. We performed the Protein-protein interaction (PPI) network, MCODE, and CytoHubba analysis from Cytoscape software to identify the significant DEGs in NSCLC. We utilized miRnet to anticipate and build interaction between miRNAs and mRNAs in NSCLC and ENCORI to predict the miRNA-circRNA relationships and build the ceRNA regulatory network. Finally, we executed the gene expression and Kaplan-Meier survival analysis to validate the significant DEGs in the ceRNA network utilizing TCGA NSCLC and GEPIA data.

RESULTS

We revealed a total of 156 overlapped DEGs (47 upregulated and 109 downregulated genes) in NSCLC. The PPI network, MCODE, and CytoHubba analysis revealed 12 hub genes (cdkn3, rrm2, ccnb1, aurka, nuf2, tyms, kif11, hmmr, ccnb2, nek2, anln, and birc5) that are associated with NSCLC. We identified that these 12 genes encode 12 mRNAs that are strongly linked with 8 miRNAs, and further, we revealed that 1 circRNA was associated with this 5 miRNA. We constructed the ceRNAs network that contained 1circRNA-5miRNAs-7mRNAs. The expression of these seven significant genes in LUAD & LUSC (NSCLC) was considerably higher in the TCGA database than in normal tissues. Kaplan-Meier survival plot reveals that increased expression of these hub genes was related to a poor survival rate in LUAD.

CONCLUSION

Overall, we developed a circRNA-miRNA-mRNA regulation network to study the probable mechanism of NSCLC.

Alterations in hepatic mitotic and cell cycle transcriptional networks during the metabolic switch in broiler chicks

During embryonic life, chicks mainly derive energy from hepatic oxidation of yolk lipids. After hatch, chicks must rely on carbohydrate-rich feed to obtain energy. This requires an abrupt and intensive switch of metabolic processes, particularly in the liver. We recently identified a number of transcriptional and post-transcriptional regulatory networks that work concordantly to tune metabolic processes during the metabolic switch. Here, we used delayed feeding post-hatch (48 h) to impede the metabolic switch in broilers. We used RNA-seq to identify hepatic transcriptome differences between late stage embryos (E18) and two-day-old chicks (D2), which were either fed-from-hatch (FED) or not fed (DLY). Between FED and E18, 2,430 genes were differentially expressed (fold-change≥ 2; FDR p-value 0.05), of these 1,237 were downregulated in FED birds and 1,193 were upregulated. Between DLY and E18, 1979 genes were differentially expressed, of these 1,043 were downregulated and 936 were upregulated in DLY birds. Between DLY and FED, 880 genes were differentially expressed, of these 543 were downregulated and 337 were upregulated in DLY birds. We found that in addition to disturbances in a number of metabolic pathways, unfed chicks had a widespread suppression of gene networks associated with cell proliferation, cell cycle progression and mitosis. Expression patterns suggest that hepatocytes of delayed-fed birds have abnormal mitosis and increased polyploidization. This suggests that post-hatch feed consumption maintains the rate and integrity of liver growth immediately, which in turn, likely helps facilitate the appropriate programming of hepatic metabolic networks.

Plasma cell-free RNA profiling distinguishes cancers from pre-malignant conditions in solid and hematologic malignancies

Cell-free RNA (cfRNA) in plasma reflects phenotypic alterations of both localized sites of cancer and the systemic host response. Here we report that cfRNA sequencing enables the discovery of messenger RNA (mRNA) biomarkers in plasma with the tissue of origin-specific to cancer types and precancerous conditions in both solid and hematologic malignancies. To explore the diagnostic potential of total cfRNA from blood, we sequenced plasma samples of eight hepatocellular carcinoma (HCC) and ten multiple myeloma (MM) patients, 12 patients of their respective precancerous conditions, and 20 non-cancer (NC) donors. We identified distinct gene sets and built classification models using Random Forest and linear discriminant analysis algorithms that could distinguish cancer patients from premalignant conditions and NC individuals with high accuracy. Plasma cfRNA biomarkers of HCC are liver-specific genes and biomarkers of MM are highly expressed in the bone marrow compared to other tissues and are related to cell cycle processes. The cfRNA level of these biomarkers displayed a gradual transition from noncancerous states through precancerous conditions and cancer. Sequencing data were cross-validated by quantitative reverse transcription PCR and cfRNA biomarkers were validated in an independent sample set (20 HCC, 9 MM, and 10 NC) with AUC greater than 0.86. cfRNA results observed in precancerous conditions require further validation. This work demonstrates a proof of principle for using mRNA transcripts in plasma with a small panel of genes to distinguish between cancers, noncancerous states, and precancerous conditions.

Depletion of NIMA-related kinase Nek2 induces aberrant self-renewal and apoptosis in stem/progenitor cells of aged muscular tissues

Frailty of the locomotory organs has become a widespread problem in the geriatric population. The major factor leading to frailty is an age-associated decrease in muscular mass and a reduced number of muscular cells and myofibers. In aged muscular tissues, muscular satellite cells (MuSCs) are reduced due to abnormalities in their self-renewal and the induction of apoptosis. However, the molecular mechanisms connecting aging-associated physiological changes and the reduction of MuSCs are largely unknown. NIMA-related kinase 2 (Nek2), a member of the Nek family of serine/threonine kinases, was found to be downregulated in aged MuSCs/progenitors. Further, Nek2 downregulation was found to inhibit self-renewal and apoptotic cell death by activating the p53-dependent checkpoint. Attenuated NEK2 expression was also observed in the muscular tissues of elderly donors, and its function was confirmed to be conserved in humans. Overall, this study proposes a novel mechanism for inducing muscular atrophy to understand aging-associated muscular diseases.

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.

Centrosome Aberrations as Drivers of Chromosomal Instability in Breast Cancer

Chromosomal instability (CIN), or the dynamic change in chromosome number and composition, has been observed in cancer for decades. Recently, this phenomenon has been implicated as facilitating the acquisition of cancer hallmarks and enabling the formation of aggressive disease. Hence, CIN has the potential to serve as a therapeutic target for a wide range of cancers. CIN in cancer often occurs as a result of disrupting key regulators of mitotic fidelity and faithful chromosome segregation. As a consequence of their essential roles in mitosis, dysfunctional centrosomes can induce and maintain CIN. Centrosome defects are common in breast cancer, a heterogeneous disease characterized by high CIN. These defects include amplification, structural defects, and loss of primary cilium nucleation. Recent studies have begun to illuminate the ability of centrosome aberrations to instigate genomic flux in breast cancer cells and the tumor evolution associated with aggressive disease and poor patient outcomes. Here, we review the role of CIN in breast cancer, the processes by which centrosome defects contribute to CIN in this disease, and the emerging therapeutic approaches that are being developed to capitalize upon such aberrations.

Centrosomal-associated Proteins: Potential therapeutic targets for solid tumors?

The centrosome is a special organelle in human cells and an organizing unit for microtubules and signaling molecules. In addition, the centrosome is tightly restricted during the cell cycle and forms the basal body of the cilia in ciliated cells. Centrosome abnormality is frequently observed in malignant tumors. The dysregulation of centrosome-associated proteins leads to multipolar mitosis, aneuploidy, and nondirected cell migration, and therefore promotes cancer progression. The overduplication of primary centrosome and the accumulation of chromosome, comprise the majority cause of chromosomal mis-segregation in cancer cells. This review discusses the structure and function of the centrosome and the role of its associated proteins in the progression of solid tumors. We summarized the effects of centrosome amplification abnormalities and other centrosome-related phenotypes on tumors. The mechanism of the delineation of centrosome amplification with tumor malignancy remains to be decided. A better understanding of centrosome abnormality in tumorigenesis may be useful to screen novel therapeutic strategies for the treatment of solid tumors.

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.

Polo-Like Kinase 4's Critical Role in Cancer Development and Strategies for Plk4-Targeted Therapy

Polo-like kinases (Plks) are critical regulatory molecules during the cell cycle process. This family has five members: Plk1, 2, 3, 4, and 5. Plk4 has been identified as a master regulator of centriole replication, and its aberrant expression is closely associated with cancer development. In this review, we depict the DNA, mRNA, and protein structure of Plk4, and the regulation of Plk4 at a molecular level. Then we list the downstream targets of Plk4 and the hallmarks of cancer associated with these targets. The role of Plk4 in different cancers is also summarized. Finally, we review the inhibitors that target Plk4 in the hope of discovering effective anticancer drugs. From authors' perspective, Plk4 might represent a valuable tumor biomarker and critical target for cancer diagnosis and therapy.

The role and underlying mechanism of miR-1299 in cancer

A type of evolutionarily conserved, noncoding, small, endogenous, single-stranded RNA, miRNAs are widely distributed in eukaryotes, where they participate in various biological processes as critical regulatory molecules. miR-1299 has mainly been investigated in cancers. miR-1299 is a tumor suppressor that regulates the expression of its target genes, activating or inhibiting the transcription of genes regulating biological activities including cell proliferation, migration, survival and programmed cell death. miR-1299 has become a hotspot in research of disease mechanisms and biomarkers; elucidation of the regulatory roles of miR-1299 in tumorigenesis, proliferation, apoptosis, invasion, migration and angiogenesis may provide a new perspective for understanding its biological functions as a tumor suppressor.

As key regulatory molecules, microRNAs participate in various biological processes and have become a widespread research focus. This article discusses how the microRNA miR-1299 plays a role as a tumor suppressor and participates in the regulation of tumor pathogenesis. We provide an overview of the role of miR-1299 in tumor diseases and discuss the pathogenesis and regulation mechanisms of miR-1299 in different specific cancers.

On Broken Ne(c)ks and Broken DNA: The Role of Human NEKs in the DNA Damage Response

NIMA-related kinases, or NEKs, are a family of Ser/Thr protein kinases involved in cell cycle and mitosis, centrosome disjunction, primary cilia functions, and DNA damage responses among other biological functional contexts in vertebrate cells. In human cells, there are 11 members, termed NEK1 to 11, and the research has mainly focused on exploring the more predominant roles of NEKs in mitosis regulation and cell cycle. A possible important role of NEKs in DNA damage response (DDR) first emerged for NEK1, but recent studies for most NEKs showed participation in DDR. A detailed analysis of the protein interactions, phosphorylation events, and studies of functional aspects of NEKs from the literature led us to propose a more general role of NEKs in DDR. In this review, we express that NEK1 is an activator of ataxia telangiectasia and Rad3-related (ATR), and its activation results in cell cycle arrest, guaranteeing DNA repair while activating specific repair pathways such as homology repair (HR) and DNA double-strand break (DSB) repair. For NEK2, 6, 8, 9, and 11, we found a role downstream of ATR and ataxia telangiectasia mutated (ATM) that results in cell cycle arrest, but details of possible activated repair pathways are still being investigated. NEK4 shows a connection to the regulation of the nonhomologous end-joining (NHEJ) repair of DNA DSBs, through recruitment of DNA-PK to DNA damage foci. NEK5 interacts with topoisomerase IIβ, and its knockdown results in the accumulation of damaged DNA. NEK7 has a regulatory role in the detection of oxidative damage to telomeric DNA. Finally, NEK10 has recently been shown to phosphorylate p53 at Y327, promoting cell cycle arrest after exposure to DNA damaging agents. In summary, this review highlights important discoveries of the ever-growing involvement of NEK kinases in the DDR pathways. A better understanding of these roles may open new diagnostic possibilities or pharmaceutical interventions regarding the chemo-sensitizing inhibition of NEKs in various forms of cancer and other diseases.

High expression of NEK2 promotes gastric cancer progression via activating AKT signaling

Never in mitosis gene A-related kinase 2 (NEK2) has been recognized as an oncogene involved in the initiation and progression of various human cancers. However, our knowledge is still lacking in regard to the function of NEK2 in gastric cancer, the most common cancer in Eastern Asia associated with poor prognosis. Therefore, in the present study, we investigated the association of NEK2 with gastric cancer. We found that the development of gastric cancer is associated with NEK2 overexpression, particularly in patients with large tumor size and lymph node metastasis. We also provided evidence that NEK2 overexpression binds to and inhibits protein phosphatase 1 (PP1), which subsequently activates AKT and the downstream oncogenic pathways. As a result, via AKT/HIF1α axis, the glucose metabolism is reprogrammed towards aerobic glycolysis to provide rapid energy for the growth of gastric cancer cells. Moreover, the autophagic activity is suppressed via AKT/mTOR axis, leading to impaired response to cancer treatment and enhanced cell survival. In contrast, inactivating AKT by NEK2 silencing decreases aerobic glycolysis and promotes autophagic cell death, which eventually inhibits the growth of gastric cancer cell. All these results revealed that NEK2 promotes gastric cancer progression via activating AKT-mediated signaling pathways, which expanded our knowledge on gastric cancer pathogenesis and also provided novel target for clinical treatment.

Involvement of NEK2 and its interaction with NDC80 and CEP250 in hepatocellular carcinoma

BACKGROUND

NEK2 has an established involvement in hepatocellular carcinoma (HCC) but the roles of NEK2 and its interacting proteins in HCC have not been systematically explored.

METHODS

This study examined NEK2 and its interacting proteins in HCC based on multiple databases.

RESULTS

NEK2 mRNA was highly expressed in HCC tissues compared with normal liver tissues. The survival of HCC patients with high NEK2 mRNA expression was shorter than those with low expression. MAD1L1, CEP250, MAPK1, NDC80, PPP1CA, PPP1R2 and NEK11 were the interacting proteins of NEK2. Among them, NDC80 and CEP250 were the key interacting proteins of NEK2. Mitotic prometaphase may be the key pathway that NEK2 and its interacting proteins contributed to HCC pathogenesis. NEK2, NDC80 and CEP250 mRNAs were highly expressed in HCC tissues compared with normal liver tissues. The mRNA levels of NEK2 were positively correlated with those of NDC80 or CEP250. Univariate regression showed that NEK2, NDC80 and CEP250 mRNA expressions were significantly associated with HCC patients' survival. Multivariate regression showed that NDC80 mRNA expression was an independent predictor for HCC patients' survival. Methylations and genetic alterations of NEK2, NDC80 and CEP250 were observed in HCC samples. The alterations of NEK2, NDC80 and CEP250 genes were co-occurrence. Patients with high mRNA expression and genetic alterations of NEK2, NDC80 and CEP250 had poor prognosis.

CONCLUSIONS

NEK2 and its interacting proteins NDC80 and CEP250 play important roles in HCC development and progression and thus may be potentially used as biomarkers and therapeutic targets of HCC.

Targeting NEK2 impairs oncogenesis and radioresistance via inhibiting the Wnt1/β-catenin signaling pathway in cervical cancer

BACKGROUND

NEK2, a serine/threonine kinase involved in mitosis, has been found to function in chromosome instability, tumor progression and metastasis, but its role in cervical cancer radioresistance remains unknown.

METHODS

We detected the protein levels of NEK2 in cervical carcinoma tissues and paired paracarcinoma tissues by immunohistochemistry. The roles of NEK2 in oncogenesis were examined using cell growth and colony formation assays, EdU assay, apoptosis assay as well as in vivo mouse model. γ-H2AX and Rad51 foci formation, neutral comet assay and clonogenic cell survival assay were applied to determine the radiosensitivity of cervical cancer cells. RNA-seq was performed to identify the downstream effector of NEK2. The gene expression levels were measured by Real-time PCR.

RESULTS

We report that NEK2 protein level is overexpressed and correlated with the tumor stage and lymph node metastasis in cervical cancer tissues. Furthermore, we provided evidence that depletion of NEK2 impairs oncogenesis and enhances radiosensitivity in cervical cancer. Using RNA sequencing, we identify Wnt1 as a key downstream effector of NEK2. Knockdown of NEK2 downregulates the mRNA and protein levels of Wnt1, thereby inhibiting the activation of the Wnt/β-catenin signaling pathway. More importantly, the observed consequences induced by NEK2 depletion in cervical cancer cells can be partially rescued by Wnt1 overexpression.

CONCLUSIONS

Our results demonstrate that NEK2 activates the Wnt/β-catenin signaling pathway via Wnt1 to drive oncogenesis and radioresistance in cervical cancer, indicating that NEK2 may be a promising target for the radiosensitization of cervical cancer.

Circular RNA circTNPO3 Regulates Paclitaxel Resistance of Ovarian Cancer Cells by miR-1299/NEK2 Signaling Pathway

Circular RNAs (circRNAs) were recently reported to be involved in the pathogenesis of ovarian cancer (OC); however, the molecular mechanisms of circRNAs in tumor progression and paclitaxel (PTX) resistance of OC remain largely undetermined. Here, we focused on circTNPO3 (hsa_circ_0001741), which is located on chromosome 7 (chr7): 128655032–128658211 and derived from TNPO3 gene, and thus we termed as circTNPO3. By microarray and qRT-PCR we identified circTNPO3 to be dramatically high expressed in OC samples and correlated with PTX resistance. Functionally, knockdown of circTNPO3 enhanced cell sensitivity to PTX via promoting PTX-induced apoptosis in vitro and in vivo. In mechanism, circTNPO3 acted as a sponge for microRNA-1299 (miR-1299), and NEK2 (NIMA-related kinase 2) was revealed to be target gene of miR-1299. Subsequently, functional assays illustrated that the oncogenic effects of circTNPO3 were attributed to the regulation of miR-1299/NEK2 axis. In conclusion, circTNPO3 contributed to PTX resistance of OC cells at least partly through upregulating NEK2 expression by sponging miR-1299. circTNPO3/miR-1299/NEK2 signaling pathway might play vital roles in the tumorigenesis and chemoresistance of OC.

Checking NEKs: Overcoming a Bottleneck in Human Diseases

In previous years, several kinases, such as phosphoinositide 3-kinase (PI3K), mammalian target of rapamycin (mTOR), and extracellular-signal-regulated kinase (ERK), have been linked to important human diseases, although some kinase families remain neglected in terms of research, hiding their relevance to therapeutic approaches. Here, a review regarding the NEK family is presented, shedding light on important information related to NEKs and human diseases. NEKs are a large group of homologous kinases with related functions and structures that participate in several cellular processes such as the cell cycle, cell division, cilia formation, and the DNA damage response. The review of the literature points to the pivotal participation of NEKs in important human diseases, like different types of cancer, diabetes, ciliopathies and central nervous system related and inflammatory-related diseases. The different known regulatory molecular mechanisms specific to each NEK are also presented, relating to their involvement in different diseases. In addition, important information about NEKs remains to be elucidated and is highlighted in this review, showing the need for other studies and research regarding this kinase family. Therefore, the NEK family represents an important group of kinases with potential applications in the therapy of human diseases.

NIMA related kinase 2 promotes gastric cancer cell proliferation via ERK/MAPK signaling

BACKGROUND

NIMA related kinase 2 (NEK2) is closely related to mitosis, and it is currently considered to be over-expressed frequently in many poorly prognostic cancers. However, the effect of the up-regulated NEK2 on cellular signaling in tumors, such as gastric cancer (GC), is con-fusing.

AIM

To determine the role of the up-regulation of NEK2 in GC.

METHODS

To investigate the pathological significance of NEK2 in GC, the expression pattern of NEK2 in GC was investigated based on the “Oncomain” database and compared between 30 pairs of cancer samples and adjacent tissues. The co-expression of NEK2 and ERK in GC was analyzed using The Cancer Genome Atlas (TCGA) database and confirmed in clinical samples by quantitative real-time PCR (qRT-PCR), and the survival curve was also plotted. Western blot or qRT-PCR was used to analyze the effect of NEK2 on the phosphorylation levels of ERK and c-JUN in two GC cell lines (BGC823 and SGC7901) with NEK2 overexpression, and the expression of the downstream effector cyclin D1. Furthermore, CCK8, EdU incorporation assay, and flow cytometry were used to detect the proliferative ability of BGC823 and SGC7901 cells with stably silenced ERK.

RESULTS

NEK2 was significantly up-regulated in human GC tissues. ERK was significantly associated with NEK2 expression in human clinical specimens, and combined overexpression of NEK2 and ERK potentially forecasted a poor prognosis and survival in GC patients. NEK2 knockdown in GC cells inhibited ERK and c-JUN phosphory-lation and reduced the transcription of cyclin D1. More interestingly, NEK2 can rescue the inhibition of cellular viability, proliferation, and cell cycle progression due to ERK knockdown.

CONCLUSION

Our results indicate that NEK2 plays a carcinogenic role in the malignant proliferation of GC cells via the ERK/MAPK signaling, which may be important for treatment and improving patient survival.

Cryo-Electron Tomography and Proteomics studies of centrosomes from differentiated quiescent thymocytes

We have used cryo Electron Tomography, proteomics and immunolabeling to study centrosomes isolated from the young lamb thymus, an efficient source of quiescent differentiated cells. We compared the proteome of thymocyte centrosomes to data published for KE37 cells, focusing on proteins associated with centriole disengagement and centrosome separation. The data obtained enhances our understanding of the protein system joining the centrioles, a system comprised of a branched network of fibers linked to an apparently amorphous density that was partially characterized here. A number of proteins were localized to the amorphous density by immunolabeling (C-NAP1, cohesin SMC1, condensin SMC4 and NCAPD2), yet not DNA. In conjuction, these data not only extend our understanding of centrosomes but they will help refine the model that focus on the protein system associated with the centriolar junction.

Diagnostic and Prognostic Biomarkers of Adrenal Cortical Carcinoma

The diagnosis of low-grade adrenal cortical carcinoma (ACC) confined to the adrenal gland can be challenging. Although there are diagnostic and prognostic molecular tests for ACC, they remain largely unutilized. We examined the diagnostic and prognostic value of altered reticulin framework and the immunoprofile of biomarkers including IGF-2, proteins involved in cell proliferation and mitotic spindle regulation (Ki67, p53, BUB1B, HURP, NEK2), DNA damage repair (PBK, γ-H2AX), telomere regulation (DAX, ATRX), wnt-signaling pathway (beta-catenin) and PI3K signaling pathway (PTEN, phospho-mTOR) in a tissue microarray of 50 adenomas and 43 carcinomas that were characterized for angioinvasion as defined by strict criteria, Weiss score, and mitotic rate-based tumor grade. IGF-2 and proteins involved in cell proliferation and mitotic spindle regulation (Ki67, p53, BUB1B, HURP, NEK2), DNA damage proteins (PBK, γ-H2AX), regulators of telomeres (DAXX, ATRX), and beta-catenin revealed characteristic expression profiles enabling the distinction of carcinomas from adenomas. Not all biomarkers were informative in all carcinomas. IGF-2 was the most useful biomarker of malignancy irrespective of tumor grade and cytomorphologic features, as juxtanuclear Golgi-pattern IGF-2 reactivity optimized for high specificity was identified in up to 80% of carcinomas and in no adenomas. Loss rather than qualitative alterations of the reticulin framework yielded statistical difference between carcinoma and adenoma. Angioinvasion defined as tumor cells invading through a vessel wall and intravascular tumor cells admixed with thrombus proved to be the best prognostic parameter, predicting adverse outcome in the entire cohort as well as within low-grade ACCs. Low mitotic tumor grade, Weiss score, global loss of DAXX expression, and high phospho-mTOR expression correlated with disease-free survival, but Weiss score and biomarkers failed to predict adverse outcome in low-grade disease. Our results underscore the importance of careful morphologic assessment coupled with ancillary diagnostic and prognostic biomarkers of ACC.

Controlling the dynamics of the Nek2 leucine zipper by engineering of "kinetic" disulphide bonds

Nek2 is a dimeric serine/ threonine protein kinase that belongs to the family of NIMA-related kinases (Neks). Its N-terminal catalytic domain and its C-terminal regulatory region are bridged by a leucine zipper, which plays an important role in the activation of Nek2's catalytic activity. Unusual conformational dynamics on the intermediary/slow timescale has thwarted all attempts so far to determine the structure of the Nek2 leucine zipper by means of X-ray crystallography and Nuclear Magnetic Resonance (NMR). Disulfide engineering, the strategic placement of non-native disulfide bonds into flexible regions flanking the coiled coil, was used to modulate the conformational exchange dynamics of this important dimerization domain. The resulting reduction in exchange rate leads to substantial improvements of important features in NMR spectra, such as line width, coherence transfer leakage and relaxation. These effects were comprehensively analyzed for the wild type protein, two single disulfide bond-bearing mutants and another double disulfide bonds-carrying mutant. Furthermore, exchange kinetics were measured across a wide temperature range, allowing for a detailed analysis of activation energy (ΔG‡) and maximal rate constant (k'ex). For one mutant carrying a disulfide bond at its C-terminus, a full backbone NMR assignment could be obtained for both conformers, demonstrating the benefits of the disulfide engineering. Our study demonstrates the first successful application of 'kinetic' disulfide bonds for the purpose of controlling the adverse effects of protein dynamics. Firstly, this provides a promising, robust platform for the full structural and functional investigation of the Nek2 leucine zipper in the future. Secondly, this work broadens the toolbox of protein engineering by disulfide bonds through the addition of a kinetic option in addition to the well-established thermodynamic uses of disulfide bonds.

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.

Prognostic value of NEK2 overexpression in digestive system cancers: a meta-analysis and systematic review

Background and objective

Many studies have reported that NEK2 is overexpressed in digestive system cancers (DSCs) and is also correlated with patient survival. We performed a meta-analysis to comprehensively evaluate the prognostic role of NEK2 expression in DSCs.

Materials and methods

A comprehensive literature search was performed using PubMed, EMBASE, and Web of Science. Synthesized hazard ratios (HRs) and odds ratios (ORs) with 95% confidence intervals (CIs) were used to evaluate the influence of NEK2 overexpression on the prognosis and clinicopathological features of patients with DSCs.

Results

A total of 13 studies involving 1,917 patients was included. Overall, patients with high NEK2 expression had poorer overall survival (HR =1.45; 95% CI: 1.15–1.83; P=0.002) and disease-free survival/recurrence-free survival (HR =2.28; 95% CI: 1.54–3.37; P<0.0001). Furthermore, subgroup analysis also suggested that elevated NEK2 expression was associated with poorer overall survival in patients with hepatocellular carcinoma (HR =1.45; 95% CI: 1.05–2.00; P=0.02) and colorectal cancer (HR =2.03; 95% CI: 1.16–3.54; P=0.01). Additionally, NEK2 overexpression was also associated with pretreatment serum AFP level (OR =1.79; 95% CI: 1.23–2.61; P<0.01) and portal vein thrombosis (OR =2.74; 95% CI: 1.22–6.17; P=0.01) in hepatocellular carcinoma.

Conclusion

NEK2 might act as a useful prognostic predictor and a potential therapeutic target in DSCs. However, multicenter homogeneous studies with larger sample sizes are needed to further confirm our findings owing to some limitations in our meta-analysis.

Immunohistochemical Biomarkers of Adrenal Cortical Neoplasms

Careful morphological evaluation forms the basis of the workup of an adrenal cortical neoplasm. However, the adoption of immunohistochemical biomarkers has added tremendous value to enhance diagnostic accuracy. The authors provide a brief review of immunohistochemical biomarkers that have been used in the confirmation of adrenal cortical origin and in the detection of the source of functional adrenal cortical proliferations, as well as diagnostic, predictive, and prognostic biomarkers of adrenal cortical carcinoma. In addition, a brief section on potential novel theranostic biomarkers in the prediction of treatment response to mitotane and other relevant chemotherapeutic agents is also provided. In the era of precision and personalized medical practice, adoption of combined morphology and immunohistochemistry provides a new approach to the diagnostic workup of adrenal cortical neoplasms, reflecting the evolution of clinical responsibility of pathologists.

PLK4: a link between centriole biogenesis and cancer

INTRODUCTION

Polo like kinase (PLK) is known to play a pivotal role in various cell cycle processes to perpetuate proper division and growth of the cells. Polo like kinase-4 (PLK4) is one such kinase that appears in low abundance and plays a well-characterized role in centriole duplication. PLK4 deregulation (i.e. both overexpression and depletion of PLK4), leads to altered mitotic fidelity and thereby triggers tumorigenesis. Hence, over the last few years PLK4 has emerged as a potential therapeutic target for the treatment of various advanced cancers. Areas covered: In this review, we discuss the basic structure, expression, localization and functions of PLK4 along with its regulation by various proteins. We also discuss the role of altered PLK4 activity in the onset of cancer and the current pre-clinical and clinical inhibitors to regulate PLK4. Expert opinion: PLK4 mediated centriole duplication has a crucial role in maintaining mitotic correctness in normal cells, while its deregulation has a greater impact on genesis of cancer. Henceforth, a deep knowledge of the PLK4 levels, its role and interactions with various proteins in cancer is required to design effective inhibitors for clinical use.

Genome-scale analysis identifies NEK2, DLGAP5 and ECT2 as promising diagnostic and prognostic biomarkers in human lung cancer

This study aims to identify promising biomarkers for the early detection of lung cancer and evaluate the prognosis of lung cancer patients. Genome-wide mRNA expression data obtained from the Gene Expression Omnibus (GSE19188, GSE18842 and GSE40791), including 231 primary tumor samples and 210 normal samples, were used to discover differentially expressed genes (DEGs). NEK2, DLGAP5 and ECT2 were found to be highly expressed in tumor samples. These results were experimentally confirmed by quantitative reverse transcription-polymerase chain reaction (qRT-PCR). The elevated expression of the three candidate genes was also validated using the Cancer Genome Atlas (TCGA) datasets, which consist of 349 tumor and 58 normal tissues. Furthermore, we performed receiver operating characteristics (ROC) analysis to assess the diagnostic value of these lung cancer biomarkers, and the results suggested that NEK2, DLGAP5 and ECT2 expression levels could robustly distinguish lung cancer patients from normal subjects. Finally, Kaplan-Meier analysis revealed that elevated NEK2, DLGAP5 and ECT2 expression was negatively correlated with both overall survival (OS) and relapse-free survival (RFS). Taken together, these findings indicate that these three genes might be used as promising biomarkers for the early detection of lung cancer, as well as predicting the prognosis of lung cancer patients.

Effect of NIMA-related kinase 2B on the sensitivity of breast cancer to paclitaxel in vitro and vivo

NIMA-related kinase 2B has been known to be an important centrosome regulatory factor. The aim of this study was to investigate the effect of NIMA-related kinase 2B on the sensitivity of breast cancer to paclitaxel. We detected the expression of NIMA-related kinase 2B messenger RNA in MCF-10 cells, including MCF-10A, MCF-10AT, MCF-10DCIS.com , and MCF-10CA1a. The influence of NIMA-related kinase 2B in nude mouse was also detected. The association between NIMA-related kinase 2B and clinicopathological factors was explored in invasive ductal carcinoma tissues. NIMA-related kinase 2B was lowly expressed in the precancerous cells, MCF-10A and MCF-10AT, and it was highly expressed in carcinomatous cells, MCF-10DCIS.com and MCF-10CA1a. The upregulation of NIMA-related kinase 2B can introduce the growth of MCF-10AT cells, knockdown of NIMA-related kinase 2B could remarkably inhibit cell proliferation in MCF-10DCIS.com and MCF-10 CA1a cells. Comparing the volume of the xenografts in nude mouse, we found that the tumors treated by NIMA-related kinase 2B small interfering RNA associated with paclitaxel were the smallest among all the groups. Expression of NIMA-related kinase 2B messenger RNA was associated with higher histological grades, positive lymph node, and high Ki67 index (>20%). The partial response rates were 75.0% in NIMA-related kinase 2B negative (NIMA-related kinase 2B-) patients and 15.8% in NIMA-related kinase 2B++ patients. The progressive disease rates were 10.0% in NIMA-related kinase 2B- patients and 52.6% in NIMA-related kinase 2B++ patients ( p = 0.002). Our findings suggested that NIMA-related kinase 2B could play a role in the development and progression of breast cancer. Combination treatment using NIMA-related kinase 2B small interfering RNA and paclitaxel might be a novel potential therapy method for breast cancer.

MiR-486-5p negatively regulates oncogenic NEK2 in hepatocellular carcinoma

NEK2 is a member of the NIMA-related family of serine/threonine centrosomal kinases. We analyzed the relationship between differential expression of NEK2 and hepatocellular carcinoma (HCC) patient outcomes after liver transplants. We also studied the microRNAs that affect NEK2 expression. Analysis of multiple microarrays in the Oncomine database revealed that NEK2 expression was higher in HCC tissues than adjacent normal liver tissues. High NEK2 expression correlated with tumor size, pathological grade and macro- and microvascular invasion. Consequently, patients exhibiting high NEK2 expression had poorer prognosis. This was corroborated by our multivariate analysis that showed NEK2 to be an independent prognostic factor for HCC patient survival. Further, high NEK2 expression promoted proliferation, colony formation, migration and invasion of HCC cell lines. Tumor xenograft data from Balb/c nude mice demonstrated that HCC cells with high NEK2 expression formed larger tumors than those with low NEK2 expression. Finally, we showed that miR-486-5p suppressed NEK2 by directly binding to its transcript 3′UTR. We also demonstrated an inverse relationship between miR-486-5p and NEK2 expression in HCC patients. These findings suggest miR-486-5p negatively regulates NEK2, which is a critical prognostic indicator of HCC patient survival after liver transplantation.

Overexpression of NIMA-related kinase 2 is associated with poor prognoses in malignant glioma

Eleated expression of NIMA-related kinase 2 (NEK2) was frequently observed in a variety of malignant cancers, and it appears to be involved in the initiation, maintenance, progression, metastasis of cancer and is positively associated with poor prognosis. We sought to investigate NEK2 expression and its predictive roles in malignant gliomas, and study the correlation of NEK2 protein expression with proliferation, clinical parameters, overall survival and some other parameters. We investigate NEK2 protein expression in 99 samples of malignant gliomas, including 35 WHO grade II, 22 grade III, and 42 grade IV gliomas, by immunohistochemistry and western blot (n = 50). We then made correlative analysis of protein overexpression using the Kaplan-Meier method, Log rank test, and Cox proportional-hazards model analysis. NEK2 protein was overexpressed in malignant gliomas, but not in normal brain tissues. Overexpression of NEK2 correlated with malignancy, proliferation and adverse overall survival in gliomas. Moreover, chemotherapy, resection extent and WHO grade also correlate with overall survival in gliomas. However, within WHO grade II glioma subgroup, NEK2 overexpression showed no impact on overall survival. The present study firstly reveals that NEK2 protein is widely overexpressed in gliomas. NEK2 overexpression correlates significantly with malignancy (WHO grades), proliferation (Ki-67) and prognosis in malignant gliomas. NEK2 is a potential gene therapy target and prognostic indicator.

Structure-guided design of purine-based probes for selective Nek2 inhibition

Nek2 (NIMA-related kinase 2) is a cell cycle-dependent serine/threonine protein kinase that regulates centrosome separation at the onset of mitosis. Overexpression of Nek2 is common in human cancers and suppression can restrict tumor cell growth and promote apoptosis. Nek2 inhibition with small molecules, therefore, offers the prospect of a new therapy for cancer. To achieve this goal, a better understanding of the requirements for selective-inhibition of Nek2 is required. 6-Alkoxypurines were identified as ATP-competitive inhibitors of Nek2 and CDK2. Comparison with CDK2-inhibitor structures indicated that judicious modification of the 6-alkoxy and 2-arylamino substituents could achieve discrimination between Nek2 and CDK2. In this study, a library of 6-cyclohexylmethoxy-2-arylaminopurines bearing carboxamide, sulfonamide and urea substituents on the 2-arylamino ring was synthesized. Few of these compounds were selective for Nek2 over CDK2, with the best result being obtained for 3-((6-(cyclohexylmethoxy)-9H-purin-2-yl)amino)-N,N-dimethylbenzamide (CDK2 IC50 = 7.0 μM; Nek2 IC50 = 0.62 μM) with >10-fold selectivity. Deletion of the 6-substituent abrogated activity against both Nek2 and CDK2. Nine compounds containing an (E)-dialkylaminovinyl substituent at C-6, all showed selectivity for Nek2, e.g. (E)-6-(2-(azepan-1-yl)vinyl)-N-phenyl-9H-purin-2-amine (CDK2 IC50 = 2.70 μM; Nek2 IC50 = 0.27 μM). Structural biology of selected compounds enabled a partial rationalization of the observed structure activity relationships and mechanism of Nek2 activation. This showed that carboxamide 11 is the first reported inhibitor of Nek2 in the DFG-in conformation.

Hepatoma cell functions modulated by NEK2 are associated with liver cancer progression

NEK2 (NIMA-related expressed kinase 2) is a serine/threonine centrosomal kinase that acts as a critical regulator of centrosome structure and function. Aberrant NEK2 activities lead to failure in regulating centrosome duplication. NEK2 overexpression promotes tumorigenesis and is associated with poor prognosis in several cancers. Increased NEK2 expression during the late pathological stage has been detected in the Oncomine liver dataset and hepatocellular carcinoma (HCC) specimens. Elevated NEK2 protein is associated with poor overall survival in patients with HCC. However, the precise roles and mechanisms of NEK2 in liver cancer progression remain largely unknown. An earlier functional study revealed that NEK2 mediates drug resistance (cisplatin or lipo-doxorubicin) via expression of an ABCC10 transporter. Active angiogenesis and metastasis underlie the rapid recurrence and poor survival of HCC. Results from the current study showed that NEK2 mediates tumor growth, metastasis and angiogenesis in vivo. NEK2-mediated drug resistance was blocked by a specific PI3K or AKT inhibitor. Moreover, NEK2 mediated liver cancer cell migration via pAKT/NF-κB signaling and matrix metalloproteinase (MMP) activation. Angiogenesis was induced via the same signaling pathway and IL-8 stimulation. Our findings collectively indicate that NEK2 modulates hepatoma cell functions, including growth, drug resistance, metastasis and angiogenesis via downstream genes activation.

NIMA-related kinase 2 regulates hepatocellular carcinoma cell growth and proliferation

NIMA-related kinase 2 (Nek2) is often upregulated in human cancer and is important in regulating the cell cycle and gene expression, and maintaining centrosomal structure and function. The present study aimed to investigate the expression pattern, clinical significance, and biological function of Nek2 in hepatocellular carcinoma (HCC). mRNA and protein levels of Nek2 were examined in HCC and corresponding normal liver tissues. The MTT and soft agar colony formation assays, and flow cytometry were employed to assess the roles of Nek2 in cell proliferation and growth. In addition, western blot analysis was performed to assess the expression of cell cycle- and proliferation-related proteins. The results revealed that Nek2 was upregulated in HCC tissues and cell lines. The clinical significance of Nek2 expression was also analyzed. Inhibiting Nek2 expression by siRNA suppressed cell proliferation, growth, and colony formation in hepatocellular carcinoma cell line HepG2 cells, induced cell cycle arrest in the G2/M phase by retarding the S-phase, and promoted apoptosis. Furthermore, Nek2 depletion downregulated β-catenin expression in HepG2 cells and diminished expression of Myc proto-oncogene protein (c-Myc), cyclins D1, B1, and E and cyclin-dependent kinase 1, whilst increasing protein levels of p27. This demonstrates that overexpression of Nek2 is associated with the malignant evolution of HCC. Targeting Nek2 may inhibit HCC cell growth and proliferation through the regulation of β-catenin by the Wnt/β-catenin pathway and therefore may be developed as a novel therapeutic strategy to treat HCC.

NEK2 serves as a prognostic biomarker for hepatocellular carcinoma

Never in mitosis gene A (NIMA)-related kinase 2 (NEK2) is a microtubule-associated protein that regulates spindle assembly in human cells and is overexpressed in various malignancies. However, the role of NEK2 in hepatocellular carcinoma (HCC) remains undetermined. We performed RNA-seq of the HCC cell line SMMC-7721 and the normal liver cell line HL-7702 using the Ion Proton System. NEK2 expression was detected using quantitative reverse transcription polymerase chain reaction in two cell lines and 5 matched HCC and adjacent non-tumorous liver tissues. The correlation between survival and NEK2 expression was analyzed in 359 patients with HCC using RNASeqV2 data available from The Cancer Genome Atlas (TCGA) website (https://tcga-data.nci.nih.gov/tcga/). The expression of NEK2, phospho-AKT and MMP-2 was evaluated by immunohistochemistry in 63 cases of HCC and matched adjacent non-tumorous liver tissues. Relationships between protein expression and clinicopathological parameters were assessed, and the correlations between NEK2 with phospho-AKT and MMP-2 expressions were evaluated. A total of 610 differentially expressed genes (DEGs) were revealed in the transcriptome comparison, 297 of which were upregulated and 313 were downregulated in HCC. NEK2, as the most obviously different DEG in cells and tissues from the RNA-seq data, was listed as an HCC candidate biomarker for further verification. NEK2 was overexpressed in HCC cells and tissues (P=0.002, P=0.013) and HCC patients with a high expression of NEK2 had a poor prognosis (P=0.0145). Clinical analysis indicated that the overexpression of NEK2 in HCC was significantly correlated with diolame complete (P<0.001), tumor nodule number (P=0.012) and recurrence (P=0.004). NEK2 expression was positively correlated with the expression of phospho-AKT (r=0.883, P<0.01) and MMP-2 (r=0.781, P<0.01). Overexpression of NEK2 was associated with clinicopathological characteristics and poor patient outcomes, suggesting that NEK2 serves as a prognostic biomarker for HCC. Alteration of NEK2 protein levels may contribute to invasion and metastasis of HCC, which may occur through activation of AKT signaling and promotion of MMP-2 expression.

APC/CFzr/Cdh1-Dependent Regulation of Planar Cell Polarity Establishment via Nek2 Kinase Acting on Dishevelled

The Anaphase-Promoting Complex/Cyclosome (APC/C) is an E3 ubiquitin ligase, well known for its role in cell-cycle progression. However, it has been linked to additional functions, mainly in neuronal contexts, when using the co-activator Cdh1/Fzr. Here, our data indicate a post-mitotic requirement for the APC/C^Fzr/Cdh1 in epithelial cell patterning and planar cell polarity (PCP) in Drosophila. PCP signaling is critical for development by establishing cellular asymmetries and orientation within the plane of an epithelium, via differential localization of distinct complexes of core PCP factors. Loss of APC/C function leads to reduced levels of Dishevelled (Dsh), a core PCP factor. The effect of APC/C on Dsh is mediated by Nek2 kinase, which can phosphorylate Dsh and is a direct APC/C^Fzr/Cdh1 substrate. We have thus uncovered a pathway of regulation whereby APC/C^Fzr/Cdh1 negatively regulates Nek2, which negatively regulates Dsh, to ensure its proper stoichiometric requirement and localization during PCP establishment.

The APC/C Coordinates Retinal Differentiation with G1 Arrest through the Nek2-Dependent Modulation of Wingless Signaling

The cell cycle is coordinated with differentiation during animal development. Here we report a cell-cycle-independent developmental role for a master cell-cycle regulator, the anaphase-promoting complex or cyclosome (APC/C), in the regulation of cell fate through modulation of Wingless (Wg) signaling. The APC/C controls both cell-cycle progression and postmitotic processes through ubiquitin-dependent proteolysis. Through an RNAi screen in the developing Drosophila eye, we found that partial APC/C inactivation severely inhibits retinal differentiation independently of cell-cycle defects. The differentiation inhibition coincides with hyperactivation of Wg signaling caused by the accumulation of a Wg modulator, Drosophila Nek2 (dNek2). The APC/C degrades dNek2 upon synchronous G1 arrest prior to differentiation, which allows retinal differentiation through local suppression of Wg signaling. We also provide evidence that decapentaplegic signaling may posttranslationally regulate this APC/C function. Thus, the APC/C coordinates cell-fate determination with the cell cycle through the modulation of developmental signaling pathways.

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APC/C inactivation disrupts retinal differentiation in the Drosophila eye

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APC/C inactivation causes the ectopic activation of Wg signaling

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APC/C^Fzr downregulates a Wg modulator, dNek2, by proteolysis upon G1 arrest

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Local dNek2 degradation ensures the coordination of retinal differentiation

Increased NEK2 in hepatocellular carcinoma promotes cancer progression and drug resistance by promoting PP1/Akt and Wnt activation

NIMA-related expressed kinase 2 (NEK2) participates in the carcinogenesis and progression of certain types of cancer, however, its expression and roles in the development of hepatocellular carcinoma (HCC) remains unknown. Here, we found that NEK2 expression was significantly upregulated in both human HCC tissues and cell lines, and increased NEK2 expression in HCC was significantly correlated with clinical progression of HCC in patients. Knockdown of NEK2 in HCC cells inhibited HCC progression, as determined by the suppressed cell proliferation, invasion and metastasis. Furthermore, knockdown of NEK2 inhibited drug resistance of HCC cells, as shown by the promoted suppression of cell viability in 5-fluorouracil (5‑FU)‑treated HCC cells. Mechanistically, protein phosphatase 1 (PP1)/Akt and Wnt signaling activation are significantly inhibited by NEK2 knockdown, which is responsible for the HCC progression and involved in NEK2‑induced cancer cell abnormal biological behavior. Thus, enhanced NEK2 expression in HCC promotes HCC progression and drug resistance by promoting PP1/Akt and Wnt pathway activation, which may represent a new therapeutic target for HCC.

The benefits of local depletion: The centrosome as a scaffold for ubiquitin-proteasome-mediated degradation

The centrosome is the major microtubule-organizing center in animal cells but is dispensable for proper microtubule spindle formation in many biological contexts and is thus thought to fulfill additional functions. Recent observations suggest that the centrosome acts as a scaffold for proteasomal degradation in the cell to regulate a variety of biological processes including cell fate acquisition, cell cycle control, stress response, and cell morphogenesis. Here, we review the body of studies indicating a role for the centrosome in promoting proteasomal degradation of ubiquitin-proteasome substrates and explore the functional relevance of this system in different biological contexts. We discuss a potential role for the centrosome in coordinating local degradation of proteasomal substrates, allowing cells to achieve stringent spatiotemporal control over various signaling processes.

Epigallocatechin gallate hinders human hepatoma and colon cancer sphere formation

BACKGROUND AND AIM

The long-term survival of patients with hepatocellular carcinoma remains unsatisfactory because of the presence of cancer stem cells (CSCs), which are responsible for tumor recurrence and chemoresistance after hepatectomy. Drugs that selectively target CSCs thus offer great promise for cancer treatment. Although the antitumor effects of epigallocatechin gallate (EGCG) have been reported in some cancer cells, its effects on CSCs remain poorly studied. In this study, we investigated the effects of EGCG on human hepatoma and colon CSCs.

METHODS

HepG2 and HCT-116 cell lines were enriched by sphere formation, and their gene-expression profiles were analyzed by quantitative real-time polymerase chain reaction. EGCG-induced growth inhibition in the parental cells was determined by WST-8 assay, and protein expression was assessed by western blotting. Cell cycle profile and apoptosis analysis was performed using flow cytometer.

RESULTS

Sphere-derived cells grown in serum-free, nonadherent cultures showed increased expression of stem cell markers, Nek2, and ATP-binding cassette transporter genes, compared with parental cells grown in conventional culture. EGCG induced growth inhibition in the parental cells in a dose-dependent manner. EGCG also inhibited self-renewal in hepatoma and colon CSCs, attenuated the expression of stem cell markers and ATP-binding cassette transporter genes, which are putative molecules associated with treatment resistance in CSCs, and decreased the transcription of Nek2 and p-Akt, resulting in the inhibition of Akt signaling. EGCG also altered cell cycle profile and apoptosis, which may in part play an important role in EGCG-induced cancer cell death.

CONCLUSIONS

Overall, these results suggest that EGCG could be a useful chemopreventive agent for targeting hepatocellular carcinoma and colon CSCs, in combination with standard chemotherapies.