Borealin/Dasra B is a cell cycle-regulated chromosomal passenger protein and its nuclear accumulation is linked to poor prognosis for human gastric cancer

The noncanonical function of borealin, a component of chromosome passenger complex, promotes glycolysis via stabilization of survivin in squamous cell carcinoma cells

The chromosome passenger complex (CPC) is a kinase complex formed by Aurora B, borealin, survivin and inner centromere protein (INCENP). The CPC is active during mitosis and contributes to proper chromosome segregation via the phosphorylation of various substrates. Overexpression of each CPC component has been reported in most cancers. However, its significance remains unclear, as only survivin is known to confer chemoresistance. This study showed that the overexpression of borealin, a CPC component, stabilized survivin protein depending on its interaction with survivin. Unexpectedly, the accumulation of survivin by borealin overexpression did not affect the well-characterized functions of survivin, such as chemoresistance and cell proliferation. Interestingly, the overexpression of borealin promoted lactate production but not the overexpression of the deletion mutant that lacks the ability to bind to survivin. Consistent with these findings, the expression levels of glycolysis-related genes were enhanced in borealin-overexpressing cancer cells. Meanwhile, the overexpression of survivin alone did not promote lactate production. Overall, the accumulation of the borealin-survivin complex promoted glycolysis in squamous cell carcinoma cells. This mechanism may contribute to cancer progression via excessive lactate production.

A 1-kb human CDCA8 promoter directs the spermatogonia-specific luciferase expression in adult testis

Cell division cycle associated 8 (CDCA8) is a component of the chromosomal passenger complex and plays an essential role in mitosis, meiosis, cancer growth, and undifferentiated state of embryonic stem cells. However, its expression and role in adult tissues remain largely uncharacterized. Here, we studied the CDCA8 transcription in adult tissues by generating a transgenic mouse model, in which the luciferase was driven by a 1-kb human CDCA8 promoter. Our previous study showed that this 1-kb promoter was active enough to dictate reporter expression faithfully reflecting endogenous CDCA8 expression. Two founder mice carrying the transgene were identified. In vivo imaging and luciferase assays in tissue lysates revealed that CDCA8 promoter was highly activated and drove robust luciferase expression in testes. Subsequently, immunohistochemical and immunofluorescent staining showed that in adult transgenic testes, the expression of luciferase was restricted to a subset of spermatogonia that were located along the basement membrane and positive for the expression of GFRA1, a consensus marker for early undifferentiated spermatogonia. These findings for the first time indicate that the CDCA8 was transcriptionally activated in testis and thus may play a role in adult spermatogenesis. Moreover, the 1-kb CDCA8 promoter could be used for spermatogonia-specific gene expression in vivo and the transgenic lines constructed here could also be used for recovery of spermatogonia from adult testes.

CDCA8 induced by NF-YA promotes hepatocellular carcinoma progression by regulating the MEK/ERK pathway

BACKGROUND

Hepatocellular carcinoma (HCC) is one of the most lethal malignant tumors. Cell division cycle associated 8 (CDCA8) is an important multifactorial regulator in cancers. However, its up and downstream targets and effects in HCC are still unclear.

METHODS

A comprehensive bioinformatics analysis was performed using The Cancer Genome Atlas dataset (TCGA) to explore novel core oncogenes. We quantified CDCA8 levels in HCC tumors using qRT-PCR. HCC cell's proliferative, migratory, and invasive abilities were detected using a Cell Counting Kit-8 (CCK-8) assay, 5-ethynyl-2'-deoxyuridine (EdU) assay, clone formation, and a Transwell assay. An orthotopic tumor model and tail vein model were constructed to determine the effects of CDCA8 inhibition in vivo. The mechanism underlying CDCA8 was investigated using RNA sequencing. The prognostic value of CDCA8 was assessed with immunohistochemical staining of the tissue microarrays.

RESULTS

CDCA8 was identified as a novel oncogene during HCC development. The high expression of CDCA8 was an independent predictor for worse HCC outcomes both in publicly available datasets and in our cohort. We found that CDCA8 knockdown inhibited HCC cell proliferation, colony formation, and migration by suppressing the MEK/ERK pathway in vitro. Moreover, CDCA8 deficiency significantly inhibited tumorigenesis and metastasis. Next-generation sequencing and laboratory validation showed that CDCA8 silencing inhibited the expression of TPM3, NECAP2, and USP13. Furthermore, NA-YA overexpression upregulated the expression of CDCA8. CDCA8 knockdown could attenuate NF-YA-mediated cell invasion in vitro. The expression of NF-YA alone or in combined with CDCA8 were validated as significant independent risk factors for patient survival.

CONCLUSION

Our findings revealed that the expression of CDCA8 alone or in combined with NF-YA contributed to cancer progression, and could serve as novel potential therapeutic targets for HCC patients.

Common Core Genes Play Vital Roles in Gastric Cancer With Different Stages

Background: Owing to complex molecular mechanisms in gastric cancer (GC) oncogenesis and progression, existing biomarkers and therapeutic targets could not significantly improve diagnosis and prognosis. This study aims to identify the key genes and signaling pathways related to GC oncogenesis and progression using bioinformatics and meta-analysis methods.

Methods: Eligible microarray datasets were downloaded and integrated using the meta-analysis method. According to the tumor stage, GC gene chips were classified into three groups. Thereafter, the three groups’ differentially expressed genes (DEGs) were identified by comparing the gene data of the tumor groups with those of matched normal specimens. Enrichment analyses were conducted based on common DEGs among the three groups. Then protein–protein interaction (PPI) networks were constructed to identify relevant hub genes and subnetworks. The effects of significant DEGs and hub genes were verified and explored in other datasets. In addition, the analysis of mutated genes was also conducted using gene data from The Cancer Genome Atlas database.

Results: After integration of six microarray datasets, 1,229 common DEGs consisting of 1,065 upregulated and 164 downregulated genes were identified. Alpha-2 collagen type I (COL1A2), tissue inhibitor matrix metalloproteinase 1 (TIMP1), thymus cell antigen 1 (THY1), and biglycan (BGN) were selected as significant DEGs throughout GC development. The low expression of ghrelin (GHRL) is associated with a high lymph node ratio (LNR) and poor survival outcomes. Thereafter, we constructed a PPI network of all identified DEGs and gained 39 subnetworks and the top 20 hub genes. Enrichment analyses were performed for common DEGs, the most related subnetwork, and the top 20 hub genes. We also selected 61 metabolic DEGs to construct PPI networks and acquired the relevant hub genes. Centrosomal protein 55 (CEP55) and POLR1A were identified as hub genes associated with survival outcomes.

Conclusion: The DEGs, hub genes, and enrichment analysis for GC with different stages were comprehensively investigated, which contribute to exploring the new biomarkers and therapeutic targets.

Synthetic Antibodies Detect Distinct Cellular States of Chromosome Passenger Complex Proteins

High performance affinity reagents are essential tools to enable biologists to profile the cellular location and composition of macromolecular complexes undergoing dynamic reorganization. To support further development of such tools, we have assembled a high-throughput phage display pipeline to generate Fab-based affinity reagents that target different dynamic forms of a large macromolecular complex, using the Chromosomal Passenger Complex (CPC), as an example. The CPC is critical for the maintenance of chromosomal and cytoskeleton processes during cell division. The complex contains 4 protein components: Aurora B kinase, survivin, borealin and INCENP. The CPC acts as a node to dynamically organize other partnering subcomplexes to build multiple functional structures during mitotic progression. Using phage display mutagenesis, a cohort of synthetic antibodies (sABs) were generated against different domains of survivin, borealin and INCENP. Immunofluorescence established that a set of these sABs can discriminate between the form of the CPC complex in the midbody versus the spindle. Others localize to targets, which appear to be less organized, in the nucleus or cytoplasm. This differentiation suggests that different CPC epitopes have dynamic accessibility depending upon the mitotic state of the cell. An Immunoprecipitation/Mass Spectrometry analysis was performed using sABs that bound specifically to the CPC in either the midbody or MT spindle macromolecular assemblies. Thus, sABs can be exploited as high performance reagents to profile the accessibility of different components of the CPC within macromolecular assemblies during different stages of mitosis suggesting this high throughput approach will be applicable to other complex macromolecular systems.

CDCA8 Contributes to the Development and Progression of Thyroid Cancer through Regulating CDK1

Background: This study aims to reveal regulatory role of cell division cycle associated 8 (CDCA8) in thyroid cancer progression and metastasis.

Methods: A series of experiments in vivo and in vitro were performed to explore the function of CDCA8 in thyroid cancer.

Results: Immunohistochemical analysis showed that CDCA8 expression levels were upregulated in thyroid cancer tissues compared with normal tissues, and were statistically correlated with tumor stage. Results of in vitro loss-of-function assay showed that downregulation of endogenous expression of CDCA8 could significantly inhibit cell proliferation, colony formation, cell migration, and promote apoptosis. Thyroid cancer cells lacking CDCA8 expression also had reduced tumorigenicity in vivo. Further, results of preliminary mechanistic exploration showed that CDK1 may be a potential downstream molecule of CDCA8 in regulating thyroid cancer progression. We subsequently confirmed that CDK1 itself exerted a significant regulatory function in thyroid cancer by loss- and gain-of-function experiments. Moreover, overexpression of CDK1 could weaken the tumor suppressive effect caused by CDCA8 knockdown.

Conclusions: CDCA8 functions as an oncogene in thyroid cancer, and CDCA8 knockdown suppresses cancer development in vitro and in vivo. Additionally, CDK1 was further identified as a potential target of CDCA8 in thyroid cancer.

Borealin Promotes Tumor Growth and Metastasis by Activating the Wnt/β-Catenin Signaling Pathway in Hepatocellular Carcinoma

Background and Aims

Hepatocellular carcinoma (HCC) is a common malignant disease with high morbidity and mortality throughout the world. While Borealin is a putative oncogene that is dysregulated in multiple tumors, its exact role in HCC remains less investigated.

Methods

Quantitative reverse transcription polymerase chain reaction (qRT-PCR) and immunohistochemistry (IHC) assays were employed to examine the relative amount of Borealin. Gene set enrichment analysis (GSEA) and other bioinformatic analyses were implemented to probe into the potential functions of Borealin. The biological roles and mechanisms of Borealin in the tumorigenesis and development of HCC were further evaluated using a battery of functional assays in vivo and in vitro.

Results

Borealin was enhanced in the HCC tissue samples and hepatoma cells when compared with the nontumor tissues and normal liver cells. Higher Borealin expression was positively linked with advanced pathological phenotypes and inferior overall survival. The overexpression of Borealin promoted the cells’ abilities on proliferation, invasion and epithelial–mesenchymal transition (EMT) in vitro, facilitated tumor growth and lung metastasis in vivo, whereas the silencing of Borealin inhibited these capabilities in vitro. Furthermore, Borealin interacted with β-catenin and further activated the Wnt/β-catenin signaling pathway, which endowed HCC cells with highly aggressive and metastatic capabilities.

Conclusion

Borealin was identified as an oncogene that could promote HCC growth and metastasis by activating the WNT/β-catenin signaling pathway. These findings extended the understanding of Borealin in HCC tumorigenesis and development and highlighted the significance of Borealin in HCC diagnosis and treatment.

Screening of Potential Key Biomarkers for Ewing Sarcoma: Evidence from Gene Array Analysis

Background

Ewing’s sarcoma (ES) is a common bone cancer in children and adolescents. There are ethnic differences in the incidence and treatment effects. People have made great efforts to clarify the cause; however, the molecular mechanism of ES is still poorly understood.

Methods

We download the microarray datasets GSE68776, GSE45544 and GSE17674 from the Gene Expression Omnibus (GEO) database. The differentially expressed genes (DEGs) of the three datasets were screened and enrichment analysis was performed. STRING and Cytoscape were used to carry out module analysis, building a protein–protein interaction (PPI) network. Finally, a series of analyses such as survival analysis and immune infiltration analysis were performed on the selected genes.

Results

A total of 629 differentially expressed genes were screened, including 206 up-regulated genes and 423 down-regulated genes. The pathways and rich-functions of DEGs include protein activation cascade, carbohydrate binding, cell-cell adhesion junctions, mitotic cell cycle, p53 pathway, and cancer pathways. Then, a total of 10 hub genes were screened out. Biological process analysis showed that these genes were mainly enriched in mitotic nuclear division, protein kinase activity, cell division, cell cycle, and protein phosphorylation.

Conclusion

Survival analysis and multiple gene comparison analysis showed that CDCA8, MAD2L1 and FANCI may be involved in the occurrence and prognosis of ES. The purpose of our study is to clarify the DEG and key genes, which will help us know more about the molecular mechanisms of ES, provide potential pathway or targets for the diagnosis and treatment.

Expression and Prognostic Role of E2F2 in Hepatocellular Carcinoma

Introduction

Hepatocellular carcinoma (HCC) is a common clinical malignancy. Recent studies reported that E2F transcription factor 2 (E2F2) plays a significant role in tumor progression. However, its expression and biological function in HCC are still unclear. Therefore, we explored the relationship between E2F2 expression and tumor progression in HCC.

Methods

In this study, we utilized some online tools to explore the E2F2 expression in pan-carcinoma and HCC. The association of E2F2 expression with the clinical characteristics and prognosis of HCC was further studied. In addition, we explored the co-expressed genes of E2F2 and mined the positively/negatively corrected significant genes and excavated the possible functions. Meanwhile, the hub gene set was constructed based on protein-protein interaction (PPI) network, and the relationship between E2F2 and immunity was discovered.

Results

We observed that the expression level of E2F2 was generally upregulated in HCC. However, E2F2 expression was not significantly different between HCC and normal tissues in regard to the disease stage 4. Furthermore, we also observed the poor prognosis in patients with high E2F2 expression. The co-expressed genes of E2F2 were identified and further detected. Thereafter, we identified the positively/negatively corrected significant genes and constructed the hub gene network of E2F2 based on PPI network. We also found that E2F2 expression was positively correlated with the infiltration levels of CD4+ T, CD8+ T cells, macrophages, neutrophils, and dendritic cells.

Conclusion

Our findings suggested that E2F2 could be a potential prognostic factor for HCC, which could provide a therapeutic target for the molecular treatment of HCC.

Cell division cycle associated 8: A novel diagnostic and prognostic biomarker for hepatocellular carcinoma

The cell division cycle associated 8 (CDCA8) is a crucial component of the chromosome passenger complex (CPC). It has been implicated in the regulation of cell dynamic localization during mitosis. However, its role in hepatocellular carcinoma (HCC) is not clearly known. In this study, data of 374 patients with HCC were retrieved from the Cancer Genome Atlas (TCGA) database. Pan analysis of Gene Expression Profiling Interactive Analysis (GEPIA) database was performed to profile the mRNA expression of CDCA8 in HCC. Then, the Kaplan‐Meier plotter database was analysed to determine the prognostic value of CDCA8 in HCC. In addition, samples of tumour and adjacent normal tissues were collected from 88 HCC patients to perform immunohistochemistry (IHC), reverse transcription‐quantitative polymerase chain reaction (qRT‐PCR) and Western blotting. The results obtained from bioinformatic analyses were validated through CCK‐8 assay, EdU assay, colony formation assay, cell cycle assays and Western blotting experiments. Analysis of the Kaplan‐Meier plotter database showed that high expression of CDCA8 may lead to poor overall survival (OS, p = 4.06e‐05) in patients with HCC. For the 88 patients with HCC, we found that stages and grades appeared to be strongly linked with CDCA8 expression. Furthermore, the high expression of CDCA8 was found to be correlated with poor OS (p = 0.0054) and progression‐free survival (PFS, p = 0.0009). In vitro experiments revealed that inhibition of CDCA8 slowed cell proliferation and blocked the cell cycle at the G0/G1 phase. In vivo experiments demonstrated that inhibition of CDCA8 inhibited tumour growth. Finally, blockade of CDCA8 reduced the expression levels of cyclin A2, cyclin D1, CDK4, CDK6, Ki67 and PCNA. And, there is an interaction between CDCA8 and E2F1. In conclusion, this research demonstrates that CDCA8 may serve as a biomarker for early diagnosis and prognosis prediction of HCC patients. In addition, CDCA8 could be an effective therapeutic target in HCC.

miR-133b inhibits cell proliferation, migration, and invasion of lung adenocarcinoma by targeting CDCA8

OBJECTIVE

Lung adenocarcinoma (LUAD) is the most common type of lung cancer. This study aims to explore the mechanism by which CDCA8 regulates cell proliferation, invasion, and migration of LUAD, and to generate novel insights into targeted therapy of LUAD.

METHODS

Expression profiles of mature microRNAs (miRNAs) and mRNAs, along with clinical data of LUAD were downloaded from TCGA database for differential analysis and survival analysis to mine differentially expressed mRNAs. qRT-PCR was used to detect the expression of CDCA8 and miR-133b in LUAD cell lines, and western blot was used to detect protein expression. The effects of CDCA8 on the proliferation, migration, and invasion of LUAD cells were detected by CCK-8 assay, scratch healing assay, and Transwell assay. Bioinformatics predicted the target miRNA of CDCA8, and dual-luciferase reporter gene assay was used to verify the binding relationship between miR-133b and CDCA8.

RESULTS

Data from TCGA-LUAD showed that CDCA8 was significantly overexpressed in LUAD tissue, while its upstream miRNA (miR-133b) was significantly lowly expressed. The result of dual-luciferase test showed that miR-133b targeted CDCA8. The results of in vitro functional experiments showed that overexpression of CDCA8 could promote the proliferation, invasion, and migration of LUAD cells, and miR-133b could reverse this promotion by targeting CDCA8.

CONCLUSION

This study found that CDCA8 was a carcinogenic factor in LUAD cells and it was regulated by upstream miR-133b. miR-133b could inhibit proliferation, invasion, and migration of LUAD cells by targeting CDCA8.

CDCA8 as an independent predictor for a poor prognosis in liver cancer

Background

Human cell division cycle associated 8 (CDCA8) a key regulator of mitosis, has been described as a potential prognostic biomarker for a variety of cancers, such as breast, colon and lung cancers. We aimed to evaluate the potential role of CDCA8 expression in the prognosis of liver cancer by analysing data from The Cancer Genome Atlas (TCGA).

Methods

The Wilcoxon rank-sum test was used to compare the difference in CDCA8 expression between liver cancer tissues and matched normal tissues. Then, we applied logistic regression and the Wilcoxon rank-sum test to identify the association between CDCA8 expression and clinicopathologic characteristics. Cox regression and the Kaplan–Meier method were used to examine the clinicopathologic features correlated with overall survival (OS) in patients from the TCGA. Gene set enrichment analysis (GSEA) was performed to explore possible mechanisms of CDCA8 according to the TCGA dataset.

Results

CDCA8 expression was higher in liver cancer tissues than in matched normal tissues. Logistic regression and the Wilcoxon rank-sum test revealed that the increased level of CDCA8 expression in liver cancer tissues was notably related to T stage (OR = 1.64 for T1/2 vs. T3/4), clinical stage (OR = 1.66 for I/II vs. III/IV), histologic grade (OR = 6.71 for G1 vs. G4) and histological type (OR = 0.24 for cholangiocarcinoma [CHOL] vs. hepatocellular carcinoma [LIHC]) (all P-values < 0.05). Kaplan–Meier survival analysis indicated that high CDCA8 expression was related to a poor prognosis in liver cancer (P = 2.456 × 10⁻⁶). Univariate analysis showed that high CDCA8 expression was associated with poor OS in liver cancer patients, with a hazard ratio (HR) of 1.85 (95% confidence interval [CI]: 1.47–2.32; P = 1.16 × 10^–7). Multivariate analysis showed that CDCA8 expression was independently correlated with OS (HR = 1.74; CI: 1.25–12.64; P = 1.27 × 10^–5). GSEA revealed that the apoptosis, cell cycle, ErbB, MAPK, mTOR, Notch, p53 and TGF-β signaling pathways were differentially enriched in the CDCA8 high expression phenotype.

Conclusions

High CDCA8 expression is a potential molecular predictor of a poor prognosis in liver cancer.

Silencing CDCA8 Suppresses Hepatocellular Carcinoma Growth and Stemness via Restoration of ATF3 Tumor Suppressor and Inactivation of AKT/β-Catenin Signaling

Simple Summary

Although the overexpression of CDCA8 is frequently observed in hepatocellular carcinoma (HCC) tissues, the functions of CDCA8 during HCC development remain to be clarified. The aim of our study was to investigate if targeting CDCA8 could affect liver tumor phenotypes in vitro and in vivo and to identify underlying molecular mechanisms to exert its therapeutic effect. We found that silencing of CDCA8 by siRNA inhibits the growth of parental cancer cell culture and mice tumors and suppresses stemness of CD133⁺ cancer stem cell population through the common responses of the upregulation of the tumor suppressive ATF3/GADD34 functional pathway and inactivation of the Akt/β–catenin signaling axis. These findings suggest CDCA8 as a novel therapeutic target for both primary HCC treatment and the prevention of metastasis or recurrence providing mode of action performed by a CDCA8 inhibitor.

Abstract

Big data analysis has revealed the upregulation of cell division cycle associated 8 (CDCA8) in human hepatocellular carcinoma (HCC) and its poorer survival outcome. However, the functions of CDCA8 during HCC development remain unknown. Here, we demonstrate in vitro that CDCA8 silencing inhibits HCC cell growth and long-term colony formation and migration through the accumulation of the G2/M phase cell population. Conversely, CDCA8 overexpression increases the ability to undergo long-term colony formation and migration. RNA sequencing and bioinformatic analysis revealed that CDCA8 knockdown led to the same directional regulation in 50 genes (25 down- and 25 upregulated). It was affirmed based on protein levels that CDCA8 silencing downregulates the levels of cyclin B1 and p-cdc2 and explains how it could induce G2/M arrest. The same condition increased the protein levels of tumor-suppressive ATF3 and GADD34 and inactivated AKT/β–catenin signaling, which plays an important role in cell growth and stemness, reflecting a reduction in sphere-forming capacity. Importantly, it was demonstrated that the extent of CDCA8 expression is much greater in CD133⁺ cancer stem cells than in CD133⁻ cancer cells, and that CDCA8 knockdown decreases levels of CD133, p-Akt and β-catenin and increases levels of ATF3 and GADD34 in the CD133⁺ cancer stem cell (CSC) population. These molecular changes led to the inhibition of cell growth and sphere formation in the CD133⁺ cell population. Targeting CDCA8 also effectively suppressed tumor growth in a murine xenograft model, showing consistent molecular alterations in tumors injected with CDCA8siRNA. Taken together, these findings indicate that silencing CDCA8 suppresses HCC growth and stemness via restoring the ATF3 tumor suppressor and inactivating oncogenic AKT/β–catenin signaling, and that targeting CDCA8 may be the next molecular strategy for both primary HCC treatment and the prevention of metastasis or recurrence.

Identification of CDCA8, DSN1 and BIRC5 in Regulating Cell Cycle and Apoptosis in Osteosarcoma Using Bioinformatics and Cell Biology

Introduction:

Osteosarcoma is the most common primary tumor of bone, although some molecular markers have been identified, the detailed molecular mechanisms underlying osteosarcoma are currently not fully understood. In the present study, we attempted to identify the potential key genes and pathways in osteosarcoma using bioinformatics analysis.

Methods:

GSE14359 was downloaded from the GEO database, and analyzed using Limma package. Gene Ontology and pathway enrichment analyses of the DEGs were performed in the DAVID database, followed by the construction of a protein–protein interaction (PPI) network with software Cytoscape, subnetwork modules were subsequently identified and analyzed, and further validation in human osteosarcoma tissues and osteosarcoma cells line was performed.

Results:

964 Differentially expressed genes (DEGs) identified, of which 222 were up-regulated and 742 were down-regulated. Among them, 10 genes (including BIRC5, MAD2L1, Bub1, DSN1, SPC24, CDCA8, STAG2, CENPA, MLF1IP and Mis12) were identified as hub genes and they were mainly enriched in pathways, including mRNA surveillance, RNA transport and PI3K-Akt signaling pathways. Further validation indicated 6 gene (DSN1, BIRC5, CDCA8, MLF1IP, MAD2L1 and SPC24) is highly expressed in osteosarcoma tissues. Among them, CDCA8, DSN1 and BIRC5 significantly promoted the proliferation of osteosarcoma cells in vitro. In terms of mechanism, DSN1 and CDCA8 were mainly involved in cell cycle regulation, while BIRC5 was mainly involved in the regulation of apoptosis pathway.

Conclusions:

We identified some key genes and pathways in osteosarcoma, which might be used as molecular targets or diagnostic biomarker for the diagnosis and therapy of osteosarcoma.

APC/CCdh1 is required for the termination of chromosomal passenger complex activity upon mitotic exit

During mitosis, the chromosomal passenger complex (CPC) ensures the faithful transmission of the genome. The CPC is composed of the enzymatic component Aurora B (AURKB) and the three regulatory and targeting components borealin, INCENP, and survivin (also known as BIRC5). Although the CPC is known to be involved in diverse mitotic events, it is still unclear how CPC function terminates after mitosis. Here we show that borealin is ubiquitylated by the anaphase promoting complex/cyclosome (APC/C) and its cofactor Cdh1 (also known as FZR1) and is subsequently degraded in G1 phase. Cdh1 binds to regions within the N terminus of borealin that act as a non-canonical degron. Aurora B has also been shown previously to be degraded by the APC/C^Cdh1 from late mitosis to G1. Indeed, Cdh1 depletion sustains an Aurora B activity with stable levels of borealin and Aurora B throughout the cell cycle, and causes reduced efficiency of DNA replication after release from serum starvation. Notably, inhibition of Aurora B kinase activity improves the efficiency of DNA replication in Cdh1-depleted cells. We thus propose that APC/C^Cdh1 terminates CPC activity upon mitotic exit and thereby contributes to proper control of DNA replication.

Summary: APC/C^Cdh1 ubiquitylates both borealin, via a non-canonical degron motif, and Aurora B to terminate activity of the CPC in G1 phase. Disruption of this ubiquitylation reduces the efficiency of DNA replication.

Knockdown of CDCA8 inhibits the proliferation and enhances the apoptosis of bladder cancer cells

Bladder cancer is a tumour of the urinary system with high mortality, and there is also a great lack of therapeutic targets in the clinic. Cell division cycle associated 8 (CDCA8), an important component of the vertebrate chromosomal passenger complex, is highly expressed in various tumours and promotes tumour development. However, the role of CDCA8 in bladder cancer is not fully understood. This study aimed to reveal the function of CDCA8 in bladder cancer by determining the relationship between CDCA8 expression and proliferation, metastasis and apoptosis of bladder cancer cells. Firstly, we studied the mRNA expression of CDCA8 through the Gene Expression Omnibus (GEO) and the Cancer Genome Atlas (TCGA) databases and analysed the correlation between CDCA8 expression and prognosis of patients with bladder cancer. We also verified CDCA8 expression in bladder cancer tissues by immunohistochemistry. In addition, CDCA8 expression was inhibited in bladder cancer T24 and 5637 cells, and the effects of CDCA8 on the proliferation, migration and invasion of bladder cancer cell lines were investigated using cell counting kit-8, colony formation, cell cycle, apoptosis, wound healing and Transwell invasion assays. Results showed that CDCA8 was highly expressed in bladder cancer compared with normal tissues, and the high CDCA8 expression was significantly correlated with the poor prognosis of patients. Inhibiting CDCA8 expression inhibited the proliferation, migration and invasion of T24 and 5637 cells and induced the apoptosis of bladder cancer cells. CDCA8 was involved in the regulation of the growth cycle of bladder cancer cells. Bioinformatics-based mechanism analysis revealed that high CDCA8 expression may affect the cell cycle and P53 signalling pathways. In conclusion, our results suggest that CDCA8 is highly expressed in bladder cancer and can promote tumour development. Hence, CDCA8 may serve as an effective therapeutic target for treatment of bladder cancer.

Possible Molecular Mechanisms for the Roles of MicroRNA-21 Played in Lung Cancer

Background:

We aimed to find the possible molecular mechanisms for the roles of microRNA-21 underlying lung cancer development.

Methods:

MicroRNA-21-5p inhibitor was transfected into A549 cells. Total RNA was isolated from 10 samples, including 3 in control group (A549 cells), 3 in negative control group (A549 cells transferred with microRNA-21 negative control), and 4 in SH group (A549 cells transferred with microRNA-21 inhibitor), followed by RNA sequencing. Then, differentially expressed genes were screened for negative control group versus control group, SH group versus control group, and SH group versus negative control group. Functional enrichment analyses, protein–protein interaction network, and modules analyses were conducted. Target genes of hsa-miR-21-5p and transcription factors were predicted, followed by the regulatory network construction.

Results:

Minichromosome maintenance 10 replication initiation factor and cell division cycle associated 8 were important nodes in protein–protein interaction network with higher degrees. Cell division cycle associated 8 was enriched in cell division biological process. Furthermore, maintenance 10 replication initiation factor and cell division cycle associated 8 were significantly enriched in cluster 1 and micro-RNA-transcription factor-target genes regulating network. In addition, transcription factor Dp family member 3 (transcription factor of maintenance 10 replication initiation factor and cell division cycle associated 8) and RAD21 cohesin complex component (transcription factor of maintenance 10 replication initiation factor) were target genes of hsa-miR-21-5p.

Conclusions:

Micro-RNA-21 may play a key role in lung cancer partly via maintenance 10 replication initiation factor and cell division cycle associated 8. Furthermore, microRNA-21 targeted cell division cycle associated 8 and then played roles in lung cancer via the process of cell division. Transcription factor Dp family member 3 and RAD21 cohesin complex component are important transcription factors in microRNA-21-interfered lung cancer.

Molecular portraits and trastuzumab responsiveness of estrogen receptor-positive, progesterone receptor-positive, and HER2-positive breast cancer

Background: Estrogen receptor-positive, progesterone receptor-positive, and HER2-positive breast cancers (triple-positive breast cancers, TPBCs) account for 5% to 10% of all breast cancers. The clinical and molecular features of TPBCs remain elusive. In this study, we aim to analyze the multiomics landscape and responsiveness of TPBCs to trastuzumab. Methods: We employed five cohorts. The first cohort was from the Surveillance, Epidemiology, and End Results database (n=32,056) and was used to determine the clinical characteristics of TPBC. The second, third and fourth cohorts were from The Cancer Genome Atlas (n=162), GSE2603 (n=37) and GSE2109 (n=30) datasets, respectively, and were used to examine the genomic features and molecular classification of TPBC. The fifth cohort comprised TPBC patients treated at Fudan University Shanghai Cancer Center (FUSCC, n=171) and was used to investigate an immunohistochemistry-defined luminal A-like subgroup of TPBC. Results: Patients with TPBC had a significantly better prognosis than those with ER-PR-HER2+ breast cancer. Genomic analysis revealed that TPBCs showed a lower TP53 mutation rate (30% vs. 69%, P < 0.001) and lower levels of HER2 mRNA and protein expression than ER-PR-HER2+ breast cancers. More than 40% of TPBCs were classified as the luminal A intrinsic subtype, with an even lower HER2 expression level. Based on the immunohistochemical detection of CDCA8, BCL2 and STC2, we identified a luminal A-like subgroup of TPBCs in the FUSCC cohort (CDCA8-negative, BCL2- and/or STC2-positive). Patients with luminal A-like TPBC had a better prognosis and benefited less from trastuzumab than those with TPBC of other subtypes. Conclusions: TPBCs consist of clinically and genomically heterogeneous subgroups that may require different therapeutic strategies. The luminal A-like subgroup of TPBCs is associated with a better prognosis and reduced benefit from trastuzumab.

Identifying novel biomarkers in hepatocellular carcinoma by weighted gene co-expression network analysis

Hepatocellular carcinoma (HCC) is a highly malignant tumor found in the bile duct epithelial cells, and the second most common tumor of the liver. However, the pivotal roles of most molecules of tumorigenesis in HCC are still unclear. Hence, it is essential to detect the tumorigenic mechanism and develop novel prognostic biomarkers for clinical application. The data of HCC mRNA-seq and clinical information from The Cancer Genome Atlas (TCGA) database were analyzed by weighted gene co-expression network analysis (WGCNA). Co-expression modules and clinical traits were constructed by the Pearson correlation analysis, interesting modules were selected and gene ontology and pathway enrichment analysis were performed. Intramodule analysis and protein-protein interaction construction of selected modules were conducted to screen hub genes. In addition, upstream transcription factors and microRNAs of hub genes were predicted by miRecords and NetworkAnalyst database. Afterward, a high connectivity degree of hub genes from two networks was picked out to perform the differential expression validation in the Gene Expression Profiling Interactive Analysis database and Human Protein Atlas database and survival analysis in Kaplan-Meier plotter online tool. By utilizing WGCNA, several hub genes that regulate the mechanism of tumorigenesis in HCC were identified, which was associated with clinical traits including the pathological stage, histological grade, and liver function. Surprisingly, ZWINT, CENPA, RACGAP1, PLK1, NCAPG, OIP5, CDCA8, PRC1, and CDK1 were identified statistically as hub genes in the blue module, which were closely implicated in pathological T stage and histologic grade of HCC. Moreover, these genes also were strongly associated with the HCC cell growth and division. Network and survival analyses found that nine hub genes may be considered theoretically as indicators to predict the prognosis of patients with HCC or clinical treatment target, it will be necessary for basic experiments and large-scale cohort studies to validate further.

Cell Division Cycle Associated 8 Is a Key Regulator of Tamoxifen Resistance in Breast Cancer

Purpose

Breast cancer (BC) is one of the most common malignancies globally, and millions of women worldwide are diagnosed with BC every year. Up to 70% of BC patients are estrogen receptor (ER)-positive. Numerous studies have shown that tamoxifen has a significant therapeutic effect on both primary and metastatic ER-positive BC patients. Although tamoxifen is currently one of the most successful therapeutic agents for BC, a significant proportion of patients will eventually become resistant to tamoxifen, leading to tumor recurrence and metastasis. Knowledge about the development of tamoxifen resistance in BC patients is still limited.

Methods

We applied a loss-and-gain method to study the biological functional role of cell division cycle associated 8 (CDCA8) in tamoxifen resistance in BC cells.

Results

We found that CDCA8 was significantly elevated in tamoxifen-resistant BC cells. Knockdown of CDCA8 expression significantly inhibited the proliferation of tamoxifen-resistant BC cells and reduced their resistance to tamoxifen. In contrast, overexpression of CDCA8 promoted the growth of tamoxifen-sensitive BC cells and induced their resistance to tamoxifen.

Conclusion

In this study, we reported that CDCA8 is a key regulator of tamoxifen resistance in BC, suggesting that CDCA8 may serve as a potential therapeutic target for BC treatment.

Identification of Potential Biomarkers in Glioblastoma through Bioinformatic Analysis and Evaluating Their Prognostic Value

Glioblastoma is a common malignant tumor in the central nervous system with an extremely poor outcome; understanding the mechanisms of glioblastoma at the molecular level is essential for clinical treatment. In the present study, we used bioinformatics analysis to identify potential biomarkers associated with prognosis in glioblastoma and elucidate the underlying mechanisms. The result revealed that 552 common genes were differentially expressed between glioblastoma and normal tissues based on TCGA, GSE4290, and GSE 50161 datasets. Gene Oncology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment and protein-protein interaction (PPI) network were carried out to gain insight into the actions of differentially expressed genes (DEGs). As a result, 20 genes (CALB1, CDC20, CDCA8, CDK1, CEP55, DLGAP5, KIF20A, KIF4A, NDC80, PBK, RRM2, SYN1, SYP, SYT1, TPX2, TTK, VEGFA, BDNF, GNG3, and TOP2A) were found as hub genes via CytoHubba in Cytoscape and functioned mainly by participating in cell cycle and p53 signaling pathway; among them, RRM2 and CEP55 were considered to have relationship with the prognosis of glioblastoma, especially RRM2. High expression of RRM2 was consistent with shorter overall survival time. In conclusion, our study displayed the bioinformatic analysis methods in screening potential oncogenes in glioblastoma and underlying mechanisms. What is more is that we successfully identified RRM2 as a novel biomarker linked with prognosis, which might be expected to be a promising target for the therapy of glioblastoma.

CDCA8 expression and its clinical relevance in patients with bladder cancer

Cell division cycle associated 8 (CDCA8) overexpression is detected in various malignant tumors and closely associated with tumor growth. However, the correlations of CDCA8 expression with clinicopathological factors and prognosis of bladder cancer (BC) remain unclear. The purpose of this study was to identify the expression of CDCA8 and its clinical relevance in BC patients.GEO datasets were employed to obtain CDCA8 expression data and its clinical information in BC samples. Real-time PCR (RT-PCR) was performed to detect the expression of CDCA8 in BC and the adjacent normal tissues. Nonpaired t test was used to statistically analyze the difference between the 2 groups. Cox univariable and multivariable analyses of overall survival (OS) and cancer specific survival (CSS) among BC patients were performed. Biological processes or signaling pathways that might mediate the activity of CDCA8 in BC were analyzed.CDCA8 levels were significantly higher in BC (8.870 ± 0.08281 vs 7.472 ± 0.07035, P < .0001). CDCA8 expression was significantly associated with tumor progression (P = .001), T stage (P < .0001), N stage (P = .013), and grade (P < .0001). Higher expression of CDCA8 predicted poor cancer-specific survival (P < .0001, HR = 0.2752, 95% CI:0.1364-0.5554) and overall survival (P < .0001, HR = 0.4270, 95% CI: 0.2630-0.6930) in patients with BC. Cox univariable and multivariable analyses showed that intravesical therapy, N stage and progression were the independent influence factors of overall survival among bladder cancer patients, CDCA8 expression, tumor grade and progression were the independent influence factors of cancer specific survival among bladder cancer patients. The results of GSEA indicated that CDCA8-regulated gene sets associated with spermatogenesis, G2M checkpoint, E2F targets, Myc targets, mTORC1 signaling, mitotic spindle angiogenesis, PI3K/AKT/mTOR signaling, cholesterol homeostasis and glycolysis. Finally, RT-PCR results confirmed that CDCA8 expression was upregulated in BC (P = .0039).CDCA8 is overexpressed in BC and its high levels are correlated with poor clinicopathological features of BC patients. Therefore, CDCA8 may act as a novel prognostic marker and therapeutical target in the diagnosis and treatment of patients with BC.

Gene expression profiling of the mouse gut: Effect of intestinal flora on intestinal health

The present study aimed to investigate the molecular mechanisms, including potential genes, pathways and interactions, underlying the effect of intestinal flora on intestinal health. The gene expression profiles of GSE22648 were downloaded from the Gene Expression Omnibus database to screen differentially expressed genes (DEGs). The Database for Annotation, Visualization and Integrated Discovery was used for Gene Ontology (GO) functional and pathway enrichment analysis of the DEGs. DEG‑associated literature was mined using the GenCLip 2.0 online tool. Finally, GO and pathway enrichment analyses of the DEGs in the literature were processed. By comparing microbiota‑depleted mouse samples and control mouse samples, a total of 115 DEGs, including 58 upregulated genes and 57 downregulated genes, were screened. The upregulated genes were enriched into various GO terms, including microsome, oxidation reduction and heme binding, whereas the 57 downregulated DEGs were enriched in different functions, including DNA packaging and linoleic acid metabolism. A total of 19 genes, including baculoviral IAP repeat containing 5, aurora kinase A, angiotensin I converting enzyme 2 and free fatty acid receptor 2 were identified and enriched in four modules, including cell division, chromosome segregation, inflammatory bowel disease and inflammatory response. AURKA, inner centromere protein antigens 135/155 kDa, baculoviral IAP repeat containing 5, aurora kinase B and solute carrier family 22 (organic cation/zwitterion transporter) member 4 were identified as potential important genes for intestinal flora and intestinal disease treatment through their involvement in various functions, including cell division, chromosome segregation, inflammatory bowel disease and inflammatory response.

The Ins and Outs of Aurora B Inner Centromere Localization

Error-free chromosome segregation is essential for the maintenance of genomic integrity during cell division. Aurora B, the enzymatic subunit of the Chromosomal Passenger Complex (CPC), plays a crucial role in this process. In early mitosis Aurora B localizes predominantly to the inner centromere, a specialized region of chromatin that lies at the crossroads between the inter-kinetochore and inter-sister chromatid axes. Two evolutionarily conserved histone kinases, Haspin and Bub1, control the positioning of the CPC at the inner centromere and this location is thought to be crucial for the CPC to function. However, recent studies sketch a subtler picture, in which not all functions of the CPC require strict confinement to the inner centromere. In this review we discuss the molecular pathways that direct Aurora B to the inner centromere and deliberate if and why this specific localization is important for Aurora B function.

Hepatic Loss of Borealin Impairs Postnatal Liver Development, Regeneration, and Hepatocarcinogenesis

Borealin, a member of the chromosomal passenger complex, plays a key regulatory role at centromeres and the central spindle during mitosis. Loss of Borealin leads to defective cell proliferation and early embryonic lethality. The in vivo functions of Borealin in mammalian postnatal development, tissue homeostasis, and tumorigenesis remain elusive. We specifically analyzed the role of Borealin in regulating postnatal liver development, damage-induced liver regeneration, and liver carcinogenesis using mice carrying conditional Borealin alleles. Perinatal loss of Borealin caused increased genome ploidy and enlarged cell size in hepatocytes, likely due to the impaired function of the chromosomal passenger complex in mitosis. Borealin deletion also showed attenuated expansion of Sox9⁺HNF4α⁺ progenitor-like cells in liver regeneration during 3,5-diethoxycarbonyl-1,4-dihydrocollidine diet-induced liver injury. Moreover, ΔN90-β-Catenin and c-Met-induced hepatocarcinogenesis development was largely impeded by Borealin deletion. These findings indicate that Borealin plays a key role in liver development, regeneration, and tumorigenesis and suggests that Borealin could be a potential target for related liver diseases.

Transcriptional activation of human CDCA8 gene regulated by transcription factor NF-Y in embryonic stem cells and cancer cells

The cell division cycle associated 8 (CDCA8) gene plays an important role in mitosis. Overexpression of CDCA8 was reported in some human cancers and is required for cancer growth and progression. We found CDCA8 expression was also high in human ES cells (hESCs) but dropped significantly upon hESC differentiation. However, the regulation of CDCA8 expression has not yet been studied. Here, we characterized the CDCA8 promoter and identified its cis-elements and transcription factors. Three transcription start sites were identified. Reporter gene assays revealed that the CDCA8 promoter was activated in hESCs and cancer cell lines. The promoter drove the reporter expression specifically to pluripotent cells during early mouse embryo development and to tumor tissues in tumor-bearing mice. These results indicate that CDCA8 is transcriptionally activated in hESCs and cancer cells. Mechanistically, two key activation elements, bound by transcription factor NF-Y and CREB1, respectively, were identified in the CDCA8 basic promoter by mutation analyses and electrophoretic motility shift assays. NF-Y binding is positively correlated with promoter activities in different cell types. Interestingly, the NF-YA subunit, binding to the promoter, is primarily a short isoform in hESCs and a long isoform in cancer cells, indicating a different activation mechanism of the CDCA8 transcription between hESCs and cancer cells. Finally, enhanced CDCA8 promoter activities by NF-Y overexpression and reduced CDCA8 transcription by NF-Y knockdown further verified that NF-Y is a positive regulator of CDCA8 transcription. Our study unearths the molecular mechanisms underlying the activation of CDCA8 expression in hESCs and cancer cells, which provides a better understanding of its biological functions.

A chromosomal passenger complex protein signature model predicts poor prognosis for non-small-cell lung cancer

AIM

The chromosomal passenger complex (CPC) acts as a key modulator for mitosis and cell cytokinesis. High levels of CPC proteins are frequently observed in multiple cancers and are correlated with more progressive malignant behaviors. The aim of the study was to evaluate whether CPC components or their combinations could be used to assess the clinical risk of patients with non-small-cell lung cancer (NSCLC).

METHODS

The expression levels of four CPC proteins - aurora B kinase (AURKB), borealin, inner centromere protein (INCENP), and survivin - were evaluated using immunohistochemistry in an independent cohort of NSCLC specimens. A molecular predictor model was developed based on the combination of the four CPC proteins.

RESULTS

All the CPC components were overexpressed in NSCLC tumors compared with their paired adjacent normal lung tissues. Survivin overexpression was significantly correlated with late tumor stage (P=0.0166). High expressions of AURKB, INCENP, and survivin, but not borealin, were associated with shorter survival in patients with NSCLC. The constructed 4-CPC-gene model divided the cohort into two different subgroups with significantly different prognoses (hazard ratio, HR =2.8915 [95% confidence interval, CI: 1.5187-5.5052]; P=0.0013) and was retained as an independent prognostic factor in multivariate analysis (HR =2.4398 [95% CI: 1.2631-4.7127], P=0.0082). Moreover, the 4-CPC-gene model demonstrated a higher predictive ability for overall survival than each individual CPC biomarker.

CONCLUSION

Taken together, our study suggests that a molecular prognostic model based on simultaneous detection of CPC components could serve as a complement to current clinical risk stratification approaches for patients with NSCLC.

Borealin/Dasra B is overexpressed in colorectal cancers and contributes to proliferation of cancer cells

Borealin/Dasra B, also called cell division cycle associated 8, is a member of the chromosomal passenger complex and plays a crucial role during mitosis and cell division. The expression of this gene has been investigated in several kinds of cancers, but its role in colorectal cancers (CRC) remains to be elucidated. In this study, our in silico analysis using the Oncomine database showed that Borealin was overexpressed in CRC tissues, which was further validated by immunohistochemistry in a cohort of 81 pairs of primary CRC and adjacent non-cancerous tissues. In CRC, Borealin expression was positively correlated with age (P = 0.0079), lymph node metastasis (P = 0.0086), and TNM stage (P = 0.0050). Significant difference in the overall survival time was seen between patients with high and low expression (P < 0.0001). Furthermore, high Borealin expression remained independently prognostic in multivariate analysis (HR 4.556, 95 % CI 1.964-10.567, P = 0.0004). Functional studies showed that suppression of Borealin expression with siRNA could significantly inhibit the growth and induce apoptosis in HCT-116 cells (P < 0.01). These results suggest that Borealin might act as an independent prognostic factor and a potential therapeutic target for patients with CRC.

Role of survivin as prognostic and clinicopathological marker in gastric cancer: a meta-analysis

Survivin has been implicated as a potential prognostic marker in a wide range of malignant tumours. However, the prognostic impact of survivin in gastric cancer remains to be controversial and published data are sometimes heterogeneous. Thus, aim of this study was to review the literature by performing an electronical database search via PubMed and EMBASE to identify eligible studies that assessed the impact of survivin as prognostic marker and its association with clinicopathological variables. Database search until November 21st 2012 retrieved 20 studies comprising 2,695 gastric cancer patients that assessed expression of survivin by immunohistochemistry or RT-PCR analyses in gastric cancer specimens. Meta-analyses of clinicopathological variables revealed an association between the expression of survivin and the presence of lymph node metastases (pooled OR: 0.58; 95 % CI 0.35-0.96). In addition, a correlation between the expression of survivin and overall survival for patients with gastric cancer (pooled HR 1.93; 95 % CI 1.51-2.48) became evident. More importantly, we were able to exclude a severe heterogeneity (I(2) = 31 %) or publication bias for the survival analyses. Furthermore, one-way sensitivity analysis and subgroup analyses regarding the method used to detect survivin, the type of survival analysis, the study quality and whether information was provided regarding neoadjuvant therapy supported our initial results. In conclusion, this meta-analysis indicates the prognostic significance of survivin in patients with gastric cancer.

Prognostic value of survivin in patients with gastric cancer: a systematic review with meta-analysis

OBJECTIVE

The prognostic significance of survivin for the survival of patients with gastric cancer remains controversial. Thus, the objective of this study was to conduct a systematic review of the literature evaluating survivin expression in gastric cancer as a prognostic indicator.

METHODS

Relevant literature was searched using PubMed, EMBASE, and Chinese biomedicine databases. A meta-analysis of the association between survivin expression and overall survival in patients with gastric cancer was performed. Studies were pooled and summary hazard ratios (HRs) were calculated. Subgroup analyses were also conducted.

RESULTS

Final analysis of 1365 patients from 16 eligible studies was performed. Combined HR suggested that survivin expression had an unfavorable impact on survival of gastric cancer patients (HR=1.39, 95% CI: 1.16-1.68). The unfavorable impact also appeared significant when stratified according to the studies categorized by patients' ethnicity, detection methods, type of sample, and HR estimate. The combined HR in the English literature showed an inverse effect on survival (HR=1.40, 95% CI: 1.13-1.75), while HR in the non-English literature did not (HR=1.38, 95% CI: 0.93-2.05). When stratified according to the location of survivin expression, combined HR showed that expression in cytoplasm was significantly associated with poor prognosis of gastric cancer patients (HR=1.46, 95% CI: 1.12-1.90). While expression in nucleus was not significantly associated with poor prognosis (HR=1.29, 95% CI: 0.72-2.31), the heterogeneity was highly significant (chi-squared=11.5, I(2)=74%, p=0.009).

CONCLUSIONS

This study showed that survivin expression was associated with a poor prognosis in patients with gastric cancer. Cytoplasmic expression of survivin may be regarded as a prognostic factor for gastric cancer patients. In contrast, survivin expression in nucleus did not have a significant impact on patients' overall survival.

Centrosome clustering and chromosomal (in)stability: a matter of life and death

Centrosome abnormalities occur commonly in cancer, and contribute to chromosomal instability and tumorigenesis. New evidence on a phylogenetically conserved mechanism termed 'centrosomal clustering' provides exciting insights into how cells with supernumerary centrosomes adapt to avoid lethal multipolar divisions. Here, we highlight the emerging molecular basis of centrosome clustering, and its impact on asymmetric divisions of stem cells, chromosomal (in)stability and malignant transformation. Finally, pharmacological inhibition of centrosome clustering promises to selectively target tumor cells.

INCENP (inner centromere protein) is overexpressed in high grade non-Hodgkin B-cell lymphomas

Inner centromere protein (INCENP) is a member of the Chromosomal Passenger Complex (CPC), which is a four member protein complex essential for proper completion of mitosis and cell division (cytokinesis). Inappropriate chromosomal segregation and cytokinesis due to deregulated expression of chromosome passenger proteins may lead to aneuploidy and cancer including lymphomas. According to our knowledge this is the first study investigating immunohistochemical expression of INCENP in lymphoma cases and cancer tissues in general. Our purpose was to characterize the expression of INCENP in cases of non-Hodgkin B-cell lymphomas, to compare the immunoreactivity between low and high grades and to evaluate the correlation between INCENP and MIB-1 labeling indices. We examined INCENP and MIB-1 immunoreactivity in paraffin sections of 55 samples of non-Hodgkin B-cell lymphomas, obtained from 55 patients, 31 men and 24 women. Thirty were of high grade and 25 were of low grade. Our results showed significantly higher nuclear immunohistochemical expression of INCENP in high grade B-cell lymphomas versus low grade ones. Also INCENP expression was significantly correlated with MIB-1 labeling index. Taken together our results point to a possible association between increased INCENP immunostaining and B-cell lymphoma aggressiveness and also stress the need for further investigating the expression of INCENP and other mitotic regulatory proteins in lymphomas and other malignant neoplasms.

Borealin is differentially expressed in ES cells and is essential for the early development of embryonic cells

Maintaining undifferentiated state and self-renewal ability of embryonic stem cells is a process that many genes and factors participate in. Using bioinformatics analyses and suppression subtractive hybridization we cloned a novel human gene related to the proliferation of human embryonic stem (hES) cells and its mouse homologue and identified them as being borealin. Our data demonstrated that borealin was highly expressed in undifferentiated ES cells, mouse pre-implantation embryos and the brain of 8.5-9.5 day post-coitum mouse embryos. Furthermore, following Borealin depletion by microinjecting anti-Borealin antibody into the zygotes the mouse embryos were arrested at the 2 or 4-cell stage and chromosomes could not correctly localize at the equator plane of the mitotic spindle and most cells had two or more nuclei. Taken together, these results indicate that Borealin plays a crucial role in the early mouse embryonic development.

Loss of Borealin/DasraB leads to defective cell proliferation, p53 accumulation and early embryonic lethality

Borealin/DasraB is a member of the chromosomal passenger protein complex (CPC) required for proper segregation of chromosomes during mitosis. In Drosophila melanogaster, inactivation of Borealin/DasraB results in polyploidy, delayed mitosis and abnormal tissue development, indicating its critical role for cell proliferation. However, the in vivo role of mammalian Borealin/DasraB remains unclear. Here, we analyzed the expression of Borealin/DasraB and found that borealin is widely expressed in embryonic tissues and later restricted to adult tissues which relies on rapid cell proliferation. To determine the role of borealin during mouse development, we generated borealin-null mice through targeted disruption. While heterozygous mice developed normally, disruption of both borealin alleles resulted in early embryonic lethality by 5.5 dpc (days postcoitus) due to mitotic defects and apoptosis in blastocyst cells that showed microtubule disorganization and no CPC enrichment. At 5.5 dpc, borealin-null embryos exhibited excessive apoptosis and elevated expression of p53. However, loss of p53 did not abrogate or delay embryonic lethality, revealing that Borealin/DasraB inactivation triggered impaired mitosis and apoptosis though p53-independent mechanisms. Our data show that Borealin/DasraB is essential for cell proliferation during early embryonic development, and its early embryonic lethality cannot be rescued by the loss of p53.

Borealin is repressed in response to p53/Rb signaling

Rb/E2F regulates many genes that encode proteins required for the cell cycle. Using affymetrix microarrays we previously identified genes regulated by the Rb proteins p130 and p107, many of which are involved in the cell cycle. Several genes with unknown functions were also repressed by p130 and p107, of which some have recently been found to have various roles in mitosis, the spindle checkpoint and cytokinesis. This study focuses on the regulation of borealin/dasra/cdca8, which encodes a recently discovered member of the chromosomal passenger complex. It is recorded that borealin is a cell cycle regulator, down-regulated in response to p53/Rb-signaling, and up-regulated in many types of cancerous tissues.

Analysis of mitotic phosphorylation of borealin

Background

The main role of the chromosomal passenger complex is to ensure that Aurora B kinase is properly localized and activated before and during mitosis. Borealin, a member of the chromosomal passenger complex, shows increased expression during G2/M phases and is involved in targeting the complex to the centromere and the spindle midzone, where it ensures proper chromosome segregation and cytokinesis. Borealin has a consensus CDK1 phosphorylation site, threonine 106 and can be phosphorylated by Aurora B Kinase at serine 165 in vitro.

Results

Here, we show that Borealin is phosphorylated during mitosis in human cells. Dephosphorylation of Borealin occurs as cells exit mitosis. The phosphorylated form of Borealin is found in an INCENP-containing complex in mitosis. INCENP-containing complexes from cells in S phase are enriched in the phosphorylated form suggesting that phosphorylation may encourage entry of Borealin into the chromosomal passenger complex. Although Aurora B Kinase is found in complexes that contain Borealin, it is not required for the mitotic phosphorylation of Borealin. Mutation of T106 or S165 of Borealin to alanine does not alter the electrophoretic mobility shift of Borealin. Experiments with cyclohexamide and the phosphatase inhibitor sodium fluoride suggest that Borealin is phosphorylated by a protein kinase that can be active in interphase and mitosis and that the phosphorylation may be regulated by a short-lived phosphatase that is active in interphase but not mitosis.

Conclusion

Borealin is phosphorylated during mitosis. Neither residue S165, T106 nor phosphorylation of Borealin by Aurora B Kinase is required to generate the mitotic, shifted form of Borealin. Suppression of phosphorylation during interphase is ensured by a labile protein, possibly a cell cycle regulated phosphatase.