Kinetochore scaffold 1 downregulation suppressed the development of non-small cell lung cancer by inactivating the phosphatidylinositol 3 kinase/protein kinase B (AKT)/nuclear factor-kappa B pathway.

Kinetochore scaffold 1 (KNL1) is indispensable for generating motile micro-tubule attachments and isolating chromosomes. KNL1 is highly expressed in multiple middle-route tissues and promotes tumor development. However, how it functions in non-small cell lung cancer (NSCLC) is unclear. Real-time quantitative PCR (RT-qPCR) and Western blotting (WB) were used to determine KNL1 expression in NSCLC tissues and cells. The sh-KNL1 or oe-KNL1 was transfected into NSCLC cells. The colony formation assay, cell counting kit-8 (CCK-8) assay, and flow cytometry were used to evaluate cell proliferation and apoptosis. A transwell assay was used to monitor invasion and migration. The CCK-8 assay was used to measure NSCLC cell sensitivity to chemotherapy drugs. WB confirmed the protein levels of apoptosis-related proteins, cell cycle-associated proteins, and the phosphatidylinositol 3 kinase (PI3K)/protein kinase B (AKT)/nuclear factor kappaB (NF-κB) pathway. A PI3K/AKT/NF-κB pathway inhibitor was used to intervene in NSCLC cell transfection along with oe-KNL1, thus revealing the function of the pathway in carcinogenicity mediated by KNL1. In result KNL1 expression was substantially increased in NSCLC tissues and cells. High-level KNL1 expression is related to the poor prognosis of NSCLC patients. KNL1 silencing bolstered promoted NSCLC cell apoptosis and inhibited proliferation, cell cycle progression, invasion, and EMT, whereas KNL1 silencing had the opposite effect. KNL1 knockdown increased NSCLC cell sensitivity to chemical drugs. KNL1 promoted PI3K/AKT/NF-κB pathway activation, while PI3K/AKT/NF-κB pathway inhibition weakened the procancer effect mediated by KNL1 overexpression but had little influence on KNL1 levels. We conclude that KNL1 activates the PI3K/AKT/NF-κB pathway to increase NSCLC progression and attenuate NSCLC sensitivity to chemotherapy drugs.

Spindle and kinetochore-related complex subunit 3 has a protumour function in osteosarcoma by activating the Notch pathway.

Increasing expression of spindle and kinetochore-related complex subunit 3 (SKA3) is related to the progression of multiple malignancies. However, the role of SKA3 in osteosarcoma remains unexplored. The present study aimed to investigate the relevance of SKA3 in osteosarcoma. Preliminarily, SKA3 expression in osteosarcoma was assessed through The Cancer Genome Atlas (TCGA) analysis, which revealed high levels of SKA3 transcripts in osteosarcoma tissues. Subsequent examination of clinical tissues confirmed the abundant expression of SKA3 in osteosarcoma. Downregulation of SKA3 expression in osteosarcoma cell lines resulted in repressive effects on cell proliferation, migration, invasion, and epithelial-to-mesenchymal transition (EMT), while upregulation of SKA3 expression had the opposite effect. Gene set enrichment analysis (GSEA) revealed that the Notch pathway is enriched in SKA3 high groups based on different expressed genes from the TCGA data. Further investigation showed that the levels of Notch1, Notch1 intracellular domain (NICD1), hairy and enhancer of split 1 (HES1), and hairy/enhancer-of-split related with YRPW motif protein 1 (HEY1) were downregulated in SKA3-silenced osteosarcoma cells, and upregulated in SKA3-overexpressed osteosarcoma cells. Activation of the Notch pathway by increasing NICD1 expression reversed the antitumour effects induced by SKA3 silencing, while deactivation of the Notch pathway diminished the protumour effects induced by SKA3 overexpression. Moreover, SKA3-silenced osteosarcoma cells exhibited a reduced capacity for xenograft formation in nude mice. In conclusion, SKA3 plays a cancer-enhancing role in osteosarcoma through its effect on the Notch pathway. Reducing the expression of SKA3 could be a potential therapeutic approach for treating osteosarcoma.

Spindle and kinetochore-associated complex 3 promotes cell growth via the PI3K/AKT/GSK3ß and PI3K/AKT/FOXO1 pathways and is a potential prognostic biomarker for oral squamous cell carcinoma.

OBJECTIVE: This study elucidated the clinical significance, functions, and mechanism of action of spindle and kinetochore-associated complex 3 (SKA3) in oral squamous cell carcinoma (OSCC). STUDY DESIGN: The SKA3 levels within the patients with OSCC were determined using the The cancer genome atlas (TCGA) database and clinical samples. The functions of SKA3 in OSCC cells were evaluated by cell counting Kit-8 (Beyotime Biotechnology, Haimen, China), 5-ethynyl-2'-deoxyuridine, wound healing, transwell invasion, flow cytometry, and xenograft nude mice model assays. A quantitative reverse transcription-polymerase chain reaction (qRT-PCR) and Western blot were performed to assess mRNA and protein expression levels in specimens and cells, respectively. RESULTS: The SKA3 was highly expressed in OSCC tissues, and its knockdown suppressed OSCC cell proliferation, migration, and invasion, and promoted their apoptosis. Mechanistically, SKA3 was shown to modulate OSCC cell proliferation and apoptosis via the PI3K/AKT/GSK3ß and PI3K/AKT/FOXO1 pathways. CONCLUSIONS: Biologically, SKA3 has a potential carcinogenic role in OSCC progression and is a promising prognostic biomarker and therapeutic target.

Chromosome Missegregation as a Modulator of Radiation Sensitivity.

Chromosome missegregation over the course of multiple cell divisions, termed chromosomal instability (CIN), is a hallmark of cancer. Multiple causes of CIN have been identified, including defects in the mitotic checkpoint, altered kinetochore-microtubule dynamics, centrosome amplification, and ionizing radiation. Here we review the types, mechanisms, and cellular implications of CIN. We discuss the evidence that CIN can promote tumors, suppress them, or do neither, depending on the rates of chromosome missegregration and the cellular context. Very high rates of chromosome missegregation lead to cell death due to loss of essential chromosomes; thus elevating CIN above a tolerable threshold provides a mechanistic opportunity to promote cancer cell death. Lethal rates of CIN can be achieved by a single insult or through a combination of insults. Because ionizing radiation induces CIN, additional therapies that increase CIN may serve as useful modulators of radiation sensitivity. Ultimately, quantifying the intrinsic CIN in a tumor and modulating this level pharmacologically as well as with radiation may allow for a more rational, personalized radiation therapy prescription, thereby decreasing side effects and increasing local control.

Integrative analysis of prognostic value and immune infiltration of spindle and kinetochore-associated family members in breast cancer.

Spindle and kinetochore associated (SKA) complex subunit, which maintains the stability of mitotic metaphase, with emerging research implying its effect as a carcinogenic regulator in cancer. However, its potential role in BC has not been fully elucidated. ONCOMINE, UALCAN, GEPIA, Kaplan-Meier Plotter, cBioPortal and TIMER databases were performed to analyze the expression, prognosis, mutation, immune infiltration and potential biological mechanisms of SKA1/2/3 in BC. Our results showed that SKA1/2/3 expression was upregulated in BC. Survival analysis reveals that SKA3 overexpression was associated with poor overall survival (OS), relapse-free survival (RFS), post-progression survival (PPS) and distant metastasis-free survival (DMFS). SKA1 overexpression was associated with poor OS, RFS and DMFS while SKA2 overexpression was only associated with RFS and DMFS. Notably, the results implied that SKA1 has a good prognostic value in HER2-positive BC. Besides, the genetic alterations of SKA were investigated and the altered group correlated with shorter progress-free survival (PFS) and disease-specific survival (DSS). GO and KEGG analysis showed that SKA1/2/3 were implicated in regulating cell cycle, p53 signaling pathway and DNA replication. The 10 Hub genes in the protein network were upregulated in BC and related to poorer prognosis. Additionally, SKA1/2/3 expression was negatively correlated with infiltration of various immune cells with antitumor effects, whereas positively correlated with the expression of immune checkpoints molecules. Further experiments revealed that SKA1/2/3 silencing markedly impeded the proliferation and migration of BC cells. Herein, our study firmly shows that SKA genes may serve as a promising therapeutic target for patients with BC.

CENP-A overexpression promotes aneuploidy with karyotypic heterogeneity.

Chromosomal instability (CIN) is a hallmark of many cancers. Restricting the localization of centromeric histone H3 variant CENP-A to centromeres prevents CIN. CENP-A overexpression (OE) and mislocalization have been observed in cancers and correlate with poor prognosis; however, the molecular consequences of CENP-A OE on CIN and aneuploidy have not been defined. Here, we show that CENP-A OE leads to its mislocalization and CIN with lagging chromosomes and micronuclei in pseudodiploid DLD1 cells and xenograft mouse model. CIN is due to reduced localization of proteins to the kinetochore, resulting in defects in kinetochore integrity and unstable kinetochore-microtubule attachments. CENP-A OE contributes to reduced expression of cell adhesion genes and higher invasion of DLD1 cells. We show that CENP-A OE contributes to aneuploidy with karyotypic heterogeneity in human cells and xenograft mouse model. In summary, our results provide a molecular link between CENP-A OE and aneuploidy, and suggest that karyotypic heterogeneity may contribute to the aggressive phenotype of CENP-A-overexpressing cancers.

HDAC11 promotes meiotic apparatus assembly during mouse oocyte maturation via decreasing H4K16 and α-tubulin acetylation.

The smallest histone deacetylase (HDAC) and the solely member of class IV, HDAC11, is reported to regulate mitosis process and tumorigenesis, yet its roles in meiosis process remain unknown. In the present study, we first analyzed the expression of HDAC11 in mouse oocytes. HDAC11 showed gradual lower expression from GV (Germinal Vesicle) to MII (Metaphase II) stage oocytes. Then, the specific inhibitor of HDAC11, JB3-22 was used to explore the role of HDAC11 during mouse oocytes maturation. We found that inhibition of HDAC11 significantly interrupted mouse oocytes meiosis progress, caused abnormal spindle organization and misaligned chromosomes, impaired kinetochore-microtubule attachment and spindle assembly checkpoint (SAC) function. Moreover, HDAC11 inhibition significantly increased the acetylation level of α-tubulin that is associated with microtubule stability, and increased acetylation level of H4K16 that is important for kinetochore function. In conclusion, our study indicates that HDAC11 is an essential factor for oocytes maturation and it promotes meiotic process most likely though decreasing acetylation status of α-tubulin and H4K16.

Dynamic kinetochore size regulation promotes microtubule capture and chromosome biorientation in mitosis.

Faithful chromosome segregation depends on the ability of sister kinetochores to attach to spindle microtubules. The outer layer of kinetochores transiently expands in early mitosis to form a fibrous corona, and compacts following microtubule capture. Here we show that the dynein adaptor Spindly and the RZZ (ROD-Zwilch-ZW10) complex drive kinetochore expansion in a dynein-independent manner. C-terminal farnesylation and MPS1 kinase activity cause conformational changes of Spindly that promote oligomerization of RZZ-Spindly complexes into a filamentous meshwork in cells and in vitro. Concurrent with kinetochore expansion, Spindly potentiates kinetochore compaction by recruiting dynein via three conserved short linear motifs. Expanded kinetochores unable to compact engage in extensive, long-lived lateral microtubule interactions that persist to metaphase, and result in merotelic attachments and chromosome segregation errors in anaphase. Thus, dynamic kinetochore size regulation in mitosis is coordinated by a single, Spindly-based mechanism that promotes initial microtubule capture and subsequent correct maturation of attachments.

Kinetochore Malfunction in Human Pathologies.

The cell cycle culminates in mitosis with the purpose of dividing the cell's DNA content equally over two daughter cells. Error-free segregation relies on correct connections between chromosomes and spindle microtubules. Kinetochores are complex multi-protein assemblies that mediate these connections and are the platforms for attachment-error-correction and spindle assembly checkpoint signaling. Proper kinetochore function is therefore key in preventing aneuploidization. Mutations in genes encoding kinetochore proteins are associated with several severe developmental disorders associated with microcephaly, and kinetochore defects contribute to chromosomal instability in certain cancers. This chapter gives an overview of the processes necessary for faithful chromosome segregation and how kinetochore malfunction causes various human pathologies.

The small molecule inhibitor YK-4-279 disrupts mitotic progression of neuroblastoma cells, overcomes drug resistance and synergizes with inhibitors of mitosis.

Neuroblastoma is a biologically and clinically heterogeneous pediatric malignancy that includes a high-risk subset for which new therapeutic agents are urgently required. As well as MYCN amplification, activating point mutations of ALK and NRAS are associated with high-risk and relapsing neuroblastoma. As both ALK and RAS signal through the MEK/ERK pathway, we sought to evaluate two previously reported inhibitors of ETS-related transcription factors, which are transcriptional mediators of the Ras-MEK/ERK pathway in other cancers. Here we show that YK-4-279 suppressed growth and triggered apoptosis in nine neuroblastoma cell lines, while BRD32048, another ETV1 inhibitor, was ineffective. These results suggest that YK-4-279 acts independently of ETS-related transcription factors. Further analysis reveals that YK-4-279 induces mitotic arrest in prometaphase, resulting in subsequent cell death. Mechanistically, we show that YK-4-279 inhibits the formation of kinetochore microtubules, with treated cells showing a broad range of abnormalities including multipolar, fragmented and unseparated spindles, together leading to disrupted progression through mitosis. Notably, YK-4-279 does not affect microtubule acetylation, unlike the conventional mitotic poisons paclitaxel and vincristine. Consistent with this, we demonstrate that YK-4-279 overcomes vincristine-induced resistance in two neuroblastoma cell-line models. Furthermore, combinations of YK-4-279 with vincristine, paclitaxel or the Aurora kinase A inhibitor MLN8237/Alisertib show strong synergy, particularly at low doses. Thus, YK-4-279 could potentially be used as a single-agent or in combination therapies for the treatment of high-risk and relapsing neuroblastoma, as well as other cancers.

Catalytic and functional roles of conserved amino acids in the SET domain of the S. cerevisiae lysine methyltransferase Set1.

In S. cerevisiae, the lysine methyltransferase Set1 is a member of the multiprotein complex COMPASS. Set1 catalyzes mono-, di- and trimethylation of the fourth residue, lysine 4, of histone H3 using methyl groups from S-adenosylmethionine, and requires a subset of COMPASS proteins for this activity. The methylation activity of COMPASS regulates gene expression and chromosome segregation in vivo. To improve understanding of the catalytic mechanism of Set1, single amino acid substitutions were made within the SET domain. These Set1 mutants were evaluated in vivo by determining the levels of K4-methylated H3, assaying the strength of gene silencing at the rDNA and using a genetic assessment of kinetochore function as a proxy for defects in Dam1 methylation. The findings indicate that no single conserved active site base is required for H3K4 methylation by Set1. Instead, our data suggest that a number of aromatic residues in the SET domain contribute to the formation of an active site that facilitates substrate binding and dictates product specificity. Further, the results suggest that the attributes of Set1 required for trimethylation of histone H3 are those required for Pol II gene silencing at the rDNA and kinetochore function.

Cancer cell micronucleus: an update on clinical and diagnostic applications.

Micronucleus (MN) is the small nucleus that forms whenever a chromosome or its fragment is not incorporated into one of the daughter nuclei during cell division. Any form of genotoxic stress due to extraneous or internal factors leads to formation of a MN, which serves as an indicator of chromosomal instability. Chromosomal damage and formation of MN are believed to play a significant role in the pathogenesis of many malignancies. Studies have shown that MN assay can be used as a tool for risk prediction, screening, diagnosis, prognosis and as a treatment-response indicator in cancers. With the advancements in technology, greater details are becoming available regarding the molecular events in carcinogenesis. The micronuclei (MNi) in the cancer cells are now being used as tools to understand the pathogenetics of the malignancies. However, despite large number of studies on MNi in lymphocytes or exfoliated cells of cancer patients, the data regarding a cancer cell MN remain scarce. This review article tries to unleash some of the mysteries related to the formation of MN inside the cancer cell. Also, it discusses the possible effects and the events post MN formation in the cancer cell.

ECRG2 disruption leads to centrosome amplification and spindle checkpoint defects contributing chromosome instability.

Cancer cells contain an abnormal number of chromosomes (aneuploidy), which is a prevalent form of genetic instability in human cancers. Abnormal amplification of centrosomes and defects of spindle assembly checkpoint are the major causes of chromosome instability in cancer cells. Here we present biochemical evidence to suggest a role of ECRG2, a novel tumor suppressor gene, in maintaining chromosome stability. ECRG2 localized to centrosomes during interphase and kinetochores during mitosis. Further analysis revealed that ECRG2 participates in centrosome amplification in a p53-dependent manner. Depletion of ECRG2 not only destabilized p53, down-regulated p21, and increased the cyclin E/CDK2 activity, thus initiating centrosome amplification, but also abolished the ability of p53 localize to centrosomes. Overexpression of ECRG2 restored the p53-dependent suppression of centrosome duplication. Furthermore, ECRG2-depleted cells show severely disrupted spindle phenotype but fail to maintain the mitotic arrest due to minimal BUBR1 protein levels. Taken together, our results indicate that ECRG2 is important for ensuring centrosome duplication, spindle assembly checkpoint, and accurate chromosome segregation, and its depletion may contribute to chromosome instability and aneuploidy in human cancers.

Chromosome instability and kinetochore dysfunction.

Chromosomal instability (CIN) has been recognized as a hallmark of human cancer and is caused by continuous chromosome missegregation during mitosis. Proper chromosome segregation requires a physical connection between spindle microtubules and centromeric DNA and this attachment occurs at proteinaceous structures called kinetochore. Thus, defect in kinetochore function is a candidate source for CIN and the generation of aneuploidy. Recently, a number of kinetochore components have been shown to be mutated and/or aberrantly expressed in human cancers, which suggests an important role of kinetochore for CIN and carcinogenesis. In this article, we will discuss about how kinetochore dysfunction causes CIN and might lead to the development of cancer.

Suppression of microtubule dynamics by benomyl decreases tension across kinetochore pairs and induces apoptosis in cancer cells.

We found that benomyl, a benzimidazole fungicide, strongly suppressed the reassembly of cold-depolymerized spindle microtubules in HeLa cells. Benomyl perturbed microtubule-kinetochore attachment and chromosome alignment at the metaphase plate. Benomyl also significantly decreased the distance between the sister kinetochore pairs in metaphase cells and increased the level of the checkpoint protein BubR1 at the kinetochore region, indicating that benomyl caused loss of tension across the kinetochores. In addition, benomyl decreased the intercentrosomal distance in mitotic HeLa cells and blocked the cells at mitosis. Further, we analyzed the effects of benomyl on the signal transduction pathways in relation to mitotic block, bcl2 phosphorylation and induction of apoptosis. The results suggest that benomyl causes loss of tension across the kinetochores, blocks the cell cycle progression at mitosis and subsequently, induces apoptosis through the bcl2-bax pathway in a manner qualitatively similar to the powerful microtubule targeted anticancer drugs like the vinca alkaloids and paclitaxel. Considering the very high toxicity of the potent anticancer drugs and the low toxicity of benomyl in humans, we suggest that benomyl could be useful as an adjuvant in combination with the powerful anticancer drugs in cancer therapy.

Histone H1 is essential for mitotic chromosome architecture and segregation in Xenopus laevis egg extracts.

During cell division, condensation and resolution of chromosome arms and the assembly of a functional kinetochore at the centromere of each sister chromatid are essential steps for accurate segregation of the genome by the mitotic spindle, yet the contribution of individual chromatin proteins to these processes is poorly understood. We have investigated the role of embryonic linker histone H1 during mitosis in Xenopus laevis egg extracts. Immunodepletion of histone H1 caused the assembly of aberrant elongated chromosomes that extended off the metaphase plate and outside the perimeter of the spindle. Although functional kinetochores assembled, aligned, and exhibited poleward movement, long and tangled chromosome arms could not be segregated in anaphase. Histone H1 depletion did not significantly affect the recruitment of known structural or functional chromosomal components such as condensins or chromokinesins, suggesting that the loss of H1 affects chromosome architecture directly. Thus, our results indicate that linker histone H1 plays an important role in the structure and function of vertebrate chromosomes in mitosis.