Mechanisms of aneuploidy in thyroid cancer cell lines and tissues: evidence for mitotic checkpoint dysfunction without mutations in BUB1 and BUBR1

On discovery of novel hub genes for ER+ and TN breast cancer types through RNA seq data analyses and classification models

Breast cancer (BC) is a malignant neoplasm which is classified into various types defined by underlying molecular factors such as estrogen receptor positive (ER+), progesterone receptor positive (PR+), human epidermal growth factor positive (HER2+) and triple negative (TNBC). Early detection of ER+ and TNBC is crucial in the choice of diagnosis and appropriate treatment strategy. Here we report the key genes associated to ER+ and TNBC using RNA-Seq analysis and machine learning models. Three ER+ and TNBC RNA seq datasets comprising 164 patients in-toto were selected for standard NGS hierarchical data processing and data analyses protocols. Enrichment pathway analysis and network analysis was done and finally top hub genes were identified. To come with a reliable classifier which could distinguish the distinct transcriptome patterns associated to ER+ and TNBC, ML models were built employing Naïve Bayes, SVM and kNN. 1730 common DEG's exhibiting significant logFC values with 0.05 p-value threshold were identified. A list of top ten hub genes were screened on the basis of maximal clique centrality (MCC) which included CDC20, CDK1, BUB1, AURKA, CDCA8, RRM2, TTK, CENPF, CEP55 and NDC80.These genes were found to be involved in crucial cell cycle pathways. k-Nearest Neighbor (kNN) model was observed to be best classifier with accuracy 84%, specificity 66% and sensitivity 95% to differentiate between ER+ and TNBC RNA-Seq transcriptomes. Our screened list of 10 hub genes can thus help unearth novel molecular signatures implicated in ER+ and TNBC onset, prognosis and design of novel protocols for breast cancer diagnostics and therapeutics.

Budding uninhibited by benzimidazoles 1 might be a poor prognosis biomarker promoting the progression of papillary thyroid cancer

BACKGROUND

Papillary thyroid carcinoma (PTC) is one of the most widespread malignant tumors of the endocrine system, with a high incidence. Budding uninhibited by benzimidazoles 1 (BUB1), one of the spindle assembly checkpoint (SAC) genes, is a multitask protein kinase required for eukaryotic chromosome segregation. Although BUB1 has been explored in several types of cancer, its biological role and molecular mechanisms in PTC remain unclear.

METHODS

In this study, we performed an examination of four public datasets along with local PTC cohorts and discovered that BUB1 was elevated in PTC compared to non-cancer tissues. High BUB1 expression was linked with the status of BRAFV600E , RAS, and TERT after statistical analysis.

RESULTS

Clinically, BUB1 is associated with a variety of clinicopathological features in PTC patients. Interestingly, analysis of the TCGA database showed that BUB1 was closely associated with poor prognosis of PTC and significantly correlated with PFS. As determined by regression analysis, BUB1, and T stage were independent predictors of PTC and were related to BRAFV600E and lymph node metastatic status. By RT-qPCR, BUB1 was considerably overexpressed in PTC cell lines in comparison with normal thyroid epithelial cells.

CONCLUSION

We confirmed that the knockdown of BUB1 in BCPAP and TPC1 cell lines significantly inhibited cell proliferation, cloning, and migration in vitro experiments. These results imply that BUB1 may be a significant oncogenic gene that is directly associated with the prognosis of PTC and may represent a future target for therapeutic intervention.

Key signaling networks are dysregulated in patients with the adipose tissue disorder, lipedema

Objectives

Lipedema, a poorly understood chronic disease of adipose hyper-deposition, is often mistaken for obesity and causes significant impairment to mobility and quality-of-life. To identify molecular mechanisms underpinning lipedema, we employed comprehensive omics-based comparative analyses of whole tissue, adipocyte precursors (adipose-derived stem cells (ADSCs)), and adipocytes from patients with or without lipedema.

Methods

We compared whole-tissues, ADSCs, and adipocytes from body mass index–matched lipedema (n = 14) and unaffected (n = 10) patients using comprehensive global lipidomic and metabolomic analyses, transcriptional profiling, and functional assays.

Results

Transcriptional profiling revealed >4400 significant differences in lipedema tissue, with altered levels of mRNAs involved in critical signaling and cell function-regulating pathways (e.g., lipid metabolism and cell-cycle/proliferation). Functional assays showed accelerated ADSC proliferation and differentiation in lipedema. Profiling lipedema adipocytes revealed >900 changes in lipid composition and >600 differentially altered metabolites. Transcriptional profiling of lipedema ADSCs and non-lipedema ADSCs revealed significant differential expression of >3400 genes including some involved in extracellular matrix and cell-cycle/proliferation signaling pathways. One upregulated gene in lipedema ADSCs, Bub1, encodes a cell-cycle regulator, central to the kinetochore complex, which regulates several histone proteins involved in cell proliferation. Downstream signaling analysis of lipedema ADSCs demonstrated enhanced activation of histone H2A, a key cell proliferation driver and Bub1 target. Critically, hyperproliferation exhibited by lipedema ADSCs was inhibited by the small molecule Bub1 inhibitor 2OH-BNPP1 and by CRISPR/Cas9-mediated Bub1 gene depletion.

Conclusion

We found significant differences in gene expression, and lipid and metabolite profiles, in tissue, ADSCs, and adipocytes from lipedema patients compared to non-affected controls. Functional assays demonstrated that dysregulated Bub1 signaling drives increased proliferation of lipedema ADSCs, suggesting a potential mechanism for enhanced adipogenesis in lipedema. Importantly, our characterization of signaling networks driving lipedema identifies potential molecular targets, including Bub1, for novel lipedema therapeutics.

Spindle assembly checkpoint competence in aneuploid canine malignant melanoma cell lines

The spindle assembly checkpoint (SAC) is a surveillance mechanism that prevents unequal segregation of chromosomes during mitosis. Abnormalities in the SAC are associated with chromosome instability and resultant aneuploidy. This study was performed to evaluate the SAC competence in canine malignant melanoma (CMM) using four aneuploid cell lines (CMeC1, CMeC2, KMeC, and LMeC). After treatment with nocodazole, a microtubule disrupting agent, CMeC1, KMeC, and LMeC cells were arrested in M phase, whereas CMeC2 cells were not arrested, and progressed into the next cell cycle phase without cytokinesis. Chromosome spread analysis revealed a significantly increased rate of premature sister chromatid separation in CMeC2 cells. Expression of the phosphorylated form of the SAC regulator, monopolar spindle 1 (Mps1), was lower in CMeC2 cells than in the other CMM cell lines. These results indicate that the SAC is defective in CMeC2 cells, which may partially explain aneuploidy in CMM. Thus, CMeC2 cells may be useful for further studies of the SAC mechanism in CMM and in determining the relationship between SAC incompetence and aneuploidy.

Unravelling the molecular mechanisms of nickel in woodlice

During the last few years, there has been an alarming increase in the amount of nickel (Ni) being released into the environment, primarily due to its use in the production of stainless steel but also from other sources such as batteries manufacturing and consequent disposal. The established biotic ligand models provide precise estimates for Ni bioavailability, in contrast, studies describing the mechanisms underpinning toxicological effect of Ni are scarce. This study exploits RNA-seq to determine the transcriptomic responses of isopods using Porcellionides pruinosus as an example of a terrestrial metal-resistant woodlouse. Furthermore, the recently proposed model for Ni adverse outcome pathways (Ni-AOP) presents an unprecedented opportunity to fit isopod responses to Ni toxicity and define Porcellionides pruinosus as a metalomic model. Prior to this study, P. pruinosus represented an important environmental sentinel, though lacking genetic/omic data. The reference transcriptome generated here thus represents a major advance and a novel resource. A detailed annotation of the transcripts obtained is presented together with the homology to genes/gene products from Metazoan and Arthropoda phylum, Gene Ontology (GO) classification, clusters of orthologous groups (COG) and assignment to KEGG metabolic pathways. The differential gene expression comparison was determined in response to nickel (Ni) exposure and used to derive the enriched pathways and processes. It revealed a significant impact on ion trafficking and storage, oxidative stress, neurotoxicity, reproduction impairment, genetics and epigenetics. Many of the processes observed support the current Ni-AOP although the data highlights that the current model can be improved by including epigenetic endpoints, which represents key chronic risks under a scenario of Ni toxicity.

Identification of Key Pathways and Genes in Anaplastic Thyroid Carcinoma via Integrated Bioinformatics Analysis

BACKGROUND To provide a better understanding of anaplastic thyroid carcinoma (ATC) at the molecular level, this study aimed to identify the genes and key pathways associated with ATC by using integrated bioinformatics analysis. MATERIAL AND METHODS Based on the microarray data GSE9115, GSE65144, and GSE53072 derived from the Gene Expression Omnibus, the differentially expressed genes (DEGs) between ATC samples and normal controls were identified. With DEGs, we performed a series of functional enrichment analyses. Then, a protein-protein interaction (PPI) network was constructed and visualized, with which the hub gene nodes were screened out. Finally, modules analysis for the PPI network was performed to further investigate the potential relationships between DEGs and ATC. RESULTS A total of 537 common DEGs were screened out from all 3 datasets, among which 247 genes were upregulated and 275 genes were downregulated. GO analysis indicated that upregulated DEGs were mainly involved in cell division and mitotic nuclear division and the downregulated DEGs were significantly enriched in ventricular cardiac muscle cell action potential. KEGG pathway analysis showed that the upregulated DEGs were mainly enriched in cell cycle and ECM-receptor interaction and the downregulated DEGs were mainly enriched in thyroid hormone synthesis, insulin resistance, and pathways in cancer. The top 10 hub genes in the constructed PPI network were CDK1, CCNB1, TOP2A, AURKB, CCNA2, BUB1, AURKA, CDC20, MAD2L1, and BUB1B. The modules analysis showed that genes in the top 2 significant modules of PPI network were mainly associated with mitotic cell cycle and positive regulation of mitosis, respectively. CONCLUSIONS We identified a series of key genes along with the pathways that were most closely related with ATC initiation and progression. Our results provide a more detailed molecular mechanism for the development of ATC, shedding light on the potential biomarkers and therapeutic targets.

In silico spatial simulations reveal that MCC formation and excess BubR1 are required for tight inhibition of the anaphase-promoting complex

In response to the activation of the mitotic spindle assembly checkpoint (SAC), distinct inhibitory pathways control the activity of the anaphase-promoting complex (APC/C). It remains unclear whether the different regulatory mechanisms function in separate pathways or as part of an integrated signalling system. Here, five variant models of APC/C regulation were constructed and analysed. The simulations showed that all variant models were able to reproduce the wild type behaviour of the APC. However, only one model, which included both the mitotic checkpoint complex (MCC) as well as BubR1 as direct inhibitors of the APC/C, was able to reproduce both wild and mutant type behaviour of APC/C regulation. Interestingly, in this model, the MCC as well as the BubR1 binding rate to the APC/C was comparable to the known Cdc20-Mad2 binding rate and could not be made higher. Mad2 active transport towards the spindle mid-zone accelerated the inhibition speed of the APC/C but not its concentration level. The presented study highlights the principle that a systems biology approach is critical for the SAC mechanism and could also be used for predicting hypotheses to design future experiments. The presented work has successfully distinguished between five potent inhibitors of the APC/C using a systems biology approach. Here, the favoured model contains both BubR1 and MCC as direct inhibitors of the APC/C.

Systems Biology Modeling of Five Pathways for Regulation and Potent Inhibition of the Anaphase-Promoting Complex (APC/C): Pivotal Roles for MCC and BubR1

Correct DNA segregation is a fundamental process that ensures the precise and reliable inheritance of genomic information for the propagation of cell life. Eukaryotic cells have evolved a conserved surveillance control mechanism for DNA segregation named the Spindle Assembly Checkpoint (SAC).The SAC ensures that the sister chromatids of the duplicated genome are not separated and distributed to the spindle poles before all chromosomes have been properly linked to the microtubules of the mitotic spindle. Biochemically, the SAC delays cell cycle progression by preventing activation of the anaphase-promoting complex (APC/C) or cyclosome whose activation by Cdc20 is required for sister-chromatid separation; this marks the transition into anaphase. In response to activation of the checkpoint, various species control the activity of both APC/C and Cdc20. However, the underlying regulatory pathways remain largely elusive. In this study, five possible model variants of APC/C regulation were constructed, namely BubR1, Mad2, MCC, MCF2, and an all-pathways model variant. These models were validated with experimental data from the literature. A wide range of parameter values has been tested to find the critical values of the APC/C binding rate. The results show that all variants are able to capture the wild-type behavior of the APC/C. However, only one model variant, which included both MCC as well as BubR1 as potent inhibitors of the APC/C, was able to reproduce both wild-type and mutant type behavior of APC/C regulation. In conclusion, the presented work informs the regulation of fundamental processes such as SAC and APC/C in cell biology and has successfully distinguished between five competing dynamical models using a systems biology approach. The results attest that systems-level approaches are vital for molecular and cell biology.

Spindle assembly checkpoint is sufficient for complete Cdc20 sequestering in mitotic control

The spindle checkpoint assembly (SAC) ensures genome fidelity by temporarily delaying anaphase onset, until all chromosomes are properly attached to the mitotic spindle. The SAC delays mitotic progression by preventing activation of the ubiquitin ligase anaphase-promoting complex (APC/C) or cyclosome; whose activation by Cdc20 is required for sister-chromatid separation marking the transition into anaphase. The mitotic checkpoint complex (MCC), which contains Cdc20 as a subunit, binds stably to the APC/C. Compelling evidence by Izawa and Pines (Nature 2014; 10.1038/nature13911) indicates that the MCC can inhibit a second Cdc20 that has already bound and activated the APC/C. Whether or not MCC per se is sufficient to fully sequester Cdc20 and inhibit APC/C remains unclear. Here, a dynamic model for SAC regulation in which the MCC binds a second Cdc20 was constructed. This model is compared to the MCC, and the MCC-and-BubR1 (dual inhibition of APC) core model variants and subsequently validated with experimental data from the literature. By using ordinary nonlinear differential equations and spatial simulations, it is shown that the SAC works sufficiently to fully sequester Cdc20 and completely inhibit APC/C activity. This study highlights the principle that a systems biology approach is vital for molecular biology and could also be used for creating hypotheses to design future experiments.

Emerging molecular markers for the prognosis of differentiated thyroid cancer patients

Epithelial thyroid cancers are represented by the differentiated papillary and follicular thyroid carcinomas which, following dedifferentiation, are thought to give rise to the highly aggressive and incurable anaplastic thyroid carcinomas. Although derived from the same cell type, the different thyroid tumors show specific histological features, biological behavior and degree of differentiation as a consequence of different genetic alterations. Over the last few years, our knowledge regarding the molecular alterations underlying thyroid cell malignant transformation and cancer progression has considerably increased; however, the prognosis of differentiated thyroid cancer patients still relies on high-risk clinic-pathological variables. In particular, the actual staging systems provides only a rough prediction for cancer mortality and risk of recurrences, including in each risk group patients with highly different tumor-specific progression, disease-free interval and survival time. In order to improve DTC patient's risk stratification, both the European and the American Thyroid Associations proposed practical guidelines to integrate the actual staging systems with additional clinical features such as the tumor histological variant, the results of post-ablative whole body scan and the serum thyroglobulin levels. Despite that, patients within the same risk group still show a very heterogeneous behavior in terms of disease-free interval. As a consequence, the identification of new prognostic molecular biomarkers able to testify tumor aggressiveness is highly required. Here we'll review recently characterized new molecular markers potentially able to ameliorate the prognosis in DTC patients.

Kinesin family member 4A: a potential predictor for progression of human oral cancer

BACKGROUND

Kinesin family member 4A (KIF4A), a microtubule-based motor protein, was implicated in regulation of chromosomal structure and kinetochore microtubule dynamics. Considering the functions of KIF4A, we assumed that KIF4A is involved in progression of oral squamous cell carcinomas (OSCCs) via activation of the spindle assembly checkpoint (SAC). However, little is known about the relevance of KIF4A in the behavior of OSCC. We investigated the KIF4A expression status and its functional mechanisms in OSCC.

METHODS

The KIF4A expression levels in seven OSCC-derived cells were analyzed by quantitative reverse transcriptase-polymerase chain reaction and immunoblotting analyses. Using a KIF4A knockdown model, we assessed the expression of (SAC)-related molecules (BUB1, MAD2, CDC20, and cyclin B1), cell-cycle, and cellular proliferation. In addition to in vitro data, the clinical correlation between the KIF4A expression levels in primary OSCCs (n = 106 patients) and the clinicopathologic status by immunohistochemistry (IHC) also were evaluated.

RESULTS

KIF4A mRNA and protein were up-regulated significantly (P < 0.05) in seven OSCC-derived cells compared with human normal oral keratinocytes. In the KIF4A knockdown cells, SAC activation was observed via increased BUB1 expression on the kinetochores, appropriate kinetochore localization of MAD2, down-regulation of CDC20, up-regulation of cyclin B1, and cell-cycle arrested at G2/M phase. The results showed that cellular proliferation of KIF4A knockdown cells decreased significantly (P < 0.05) compared with control cells. IHC showed that KIF4A expression in primary OSCCs was significantly (P < 0.05) greater than in the normal oral counterparts and that KIF4A-positive OSCCs were correlated closely (P < 0.05) with tumoral size.

CONCLUSIONS

Our results proposed for the first time that KIF4A controls cellular proliferation via SAC activation. Therefore, KIF4A might be a key regulator for tumoral progression in OSCCs.

New insights into the role of BubR1 in mitosis and beyond

BubR1 is a critical component of the spindle assembly checkpoint, the surveillance mechanism that helps maintain the high fidelity of mitotic chromosome segregation by preventing cells from initiating anaphase if one or more kinetochores are not attached to the spindle. BubR1 also helps promote the establishment of stable kinetochore-microtubule attachments during prometaphase. In this chapter, we review the structure, functions, and regulation of BubR1 in these "classical roles" at the kinetochore. We discuss its recruitment to kinetochores, its assembly into the inhibitor of anaphase progression, and the importance of its posttranslational modifications. We also consider the evidence for its participation in other roles beyond mitosis, such as the meiosis-specific processes of recombination and prophase arrest of the first meiotic division, the cellular response to DNA damage, and in the regulation of centrosome and basal body function. Finally, studies are presented linking BubR1 dysfunction or misregulation to aging and human disease, particularly cancer.

Genetic instability: tipping the balance

Tumor cells typically contain a genome that is highly divergent from the genome of normal, non-transformed cells. This genetic divergence is caused by a number of distinct changes that the tumor cell acquires during its transformation from a normal cell into a tumorigenic counterpart. Changes to the genome include mutations, deletions, insertions, and also gross chromosomal aberrations, such as chromosome translocations and whole chromosome gains or losses. This genetic disorder of the tumor cell has complicated the identification of crucial driver mutations that cause cancer. Moreover, the large genetic divergence between different tumors causes them to behave very differently, and makes it difficult to predict response to therapy. In addition, tumor cells are genetically unstable and frequently acquire new mutations and/or gross chromosomal aberrations as they divide. This is beneficial for the overall capacity of a tumor to adapt to changes in its environment, but newly acquired genetic alterations can also compromise the genetic dominance of the tumor cell and thus affect tumor cell viability. Here, we review the mechanisms that can cause gross chromosomal aberrations, and discuss how these affect tumor cell viability.

Up-regulation of the mitotic checkpoint component Mad1 causes chromosomal instability and resistance to microtubule poisons

The mitotic checkpoint is the major cell cycle checkpoint acting during mitosis to prevent aneuploidy and chromosomal instability, which are hallmarks of tumor cells. Reduced expression of the mitotic checkpoint component Mad1 causes aneuploidy and promotes tumors in mice [Iwanaga Y, et al. (2007) Cancer Res 67:160-166]. However, the prevalence and consequences of Mad1 overexpression are currently unclear. Here we show that Mad1 is frequently overexpressed in human cancers and that Mad1 up-regulation is a marker of poor prognosis. Overexpression of Mad1 causes aneuploidy and chromosomal instability through weakening mitotic checkpoint signaling caused by mislocalization of the Mad1 binding partner Mad2. Cells overexpressing Mad1 are resistant to microtubule poisons, including currently used chemotherapeutic agents. These results suggest that levels of Mad1 must be tightly regulated to prevent aneuploidy and transformation and that Mad1 up-regulation may promote tumors and cause resistance to current therapies.

BUBR1 expression in oral squamous cell carcinoma and its relationship to tumor stage and survival

BACKGROUND

Defects in the mitotic spindle checkpoint have been proposed to contribute to the chromosomal instability observed in human cancers, including oral squamous cell carcinoma (OSCC). BUBR1 is a key component of the spindle checkpoint, whose role in oral carcinogenesis still needs to be clarified.

METHODS

We have analyzed the expression of BUBR1 in 49 cases of OSCC by immunohistochemistry and compared the findings with clinicopathologic parameters, proliferative activity, and DNA ploidy.

RESULTS

BUBR1 was overexpressed in 11 cases (22.4%). Tumors with overexpression of BUBR1 were associated with a less advanced pathologic stage (p = .05) and showed longer survival periods (p = .38) but shorter recurrence-free survival periods (p = .13) than those without it.

CONCLUSIONS

Our data imply the possibility that BUBR1 may be involved in the progression of OSCC, and suggest that BUBR1 may be a promising prognostic marker in patients with OSCC.

BUB1 and BUBR1: multifaceted kinases of the cell cycle

The multidomain protein kinases BUB1 and BUBR1 (Mad3 in yeast, worms and plants) are central components of the mitotic checkpoint for spindle assembly (SAC). This evolutionarily conserved and essential self-monitoring system of the eukaryotic cell cycle ensures the high fidelity of chromosome segregation by delaying the onset of anaphase until all chromosomes are properly bi-oriented on the mitotic spindle. Despite their amino acid sequence conservation and similar domain organization, BUB1 and BUBR1 perform different functions in the SAC. Recent structural information provides crucial molecular insights into the regulation and recognition of BUB1 and BUBR1, and a solid foundation to dissect the roles of these proteins in the control of chromosome segregation in normal and oncogenic cells.

Bub1 regulates chromosome segregation in a kinetochore-independent manner

The kinetochore-bound protein kinase Bub1 performs two crucial functions during mitosis: it is essential for spindle checkpoint signaling and for correct chromosome alignment. Interestingly, Bub1 mutations are found in cancer tissues and cancer cell lines. Using an isogenic RNA interference complementation system in transformed HeLa cells and untransformed RPE1 cells, we investigate the effect of structural Bub1 mutants on chromosome segregation. We demonstrate that Bub1 regulates mitosis through the same mechanisms in both cell lines, suggesting a common regulatory network. Surprisingly, Bub1 can regulate chromosome segregation in a kinetochore-independent manner, albeit at lower efficiency. Its kinase activity is crucial for chromosome alignment but plays only a minor role in spindle checkpoint signaling. We also identify a novel conserved motif within Bub1 (amino acids 458–476) that is essential for spindle checkpoint signaling but does not regulate chromosome alignment, and we show that several cancer-related Bub1 mutants impair chromosome segregation, suggesting a possible link to tumorigenesis.

Clinicopathological relevance of UbcH10 in breast cancer

Abrogated mitotic progression is a common hallmark of cancer. UbcH10, one of the components of the ubiquitin/proteasome pathway, plays a pivotal role in the regulation of mitotic progression. Abnormal UbcH10 activity is reported in certain types of human cancers; its overexpression is occasionally encountered in cancerous tissue compared with adjacent normal tissue. Current studies have suggested the critical role of UbcH10 in the spindle assembly checkpoint and the subsequent accurate separation of sister chromatids, which is orchestrated by a series of molecular interactions governed by the complex and diverse cell cycle machinery. To validate the potential role of UbcH10 in cell proliferation in cancer, we have analyzed the clinicopathological relevance of UbcH10 in progression of breast cancer using a combinatorial approach of human tumor arrays and biochemical analyses. Our results show that the percentage of tested samples which stained positive for UbcH10 in breast cancer tissues is significantly higher compared to the adjacent nonmalignant tissue. Furthermore, results from the clinicopathological analysis have revealed that elevated expression of UbcH10 is associated with higher histological grade tumors. In addition, depletion of UbcH10 by RNA interference in breast cancer cells resulted in decreased cellular proliferation, while overexpression of UbcH10 significantly enhanced cellular growth in breast cancer. Our results suggest a pathological correlation between UbcH10 and cell proliferation in breast cancer. Thus, aberrant UbcH10 activity may induce the dysfunction of proper cell cycle progression and result in the aggressive behavior of tumor cells in patients with breast cancer.

Re-expression of ABI3-binding protein suppresses thyroid tumor growth by promoting senescence and inhibiting invasion

Loss of ABI gene family member 3-binding protein (ABI3BP) expression may be functionally involved in the pathogenesis of cancer. Previous reports have indicated a loss of expression in lung cancer and a presumed role in inducing cellular senescence. We show here that ABI3BP expression is significantly decreased in most malignant thyroid tumors of all types. To better understand ABI3BP's role, we created a model by re-expressing ABI3BP in two thyroid cancer cell lines. Re-expression of ABI3BP in thyroid cells resulted in a decrease in transforming activity, cell growth, cell viability, migration, invasion, and tumor growth in nude mice. ABI3BP re-expression appears to trigger cellular senescence through the p21 pathway. Additionally, ABI3BP induced formation of heterochromatin 1-binding protein gamma-positive senescence-associated (SA) heterochromatin foci and accumulation of SA beta-galactosidase. The combination of a decrease in cell growth, invasion, and other effects upon ABI3BP re-expression in vitro helps to explain the large reduction in tumor growth that we observed in nude mice. Together, our data provide evidence that the loss of ABI3BP expression could play a functional role in thyroid tumorigenesis. Activation of ABI3BP or its pathway may represent a possible basis for targeted therapy of certain cancers.

Studying chromosome instability in the mouse

Aneuploidy has long been recognized as one of the hallmarks of cancer. It nonetheless remains uncertain whether aneuploidy occurring early in the development of a cancer is a primary cause of oncogenic transformation, or whether it is an epiphenomenon that arises from a general breakdown in cell cycle control late in tumorigenesis. The accuracy of chromosome segregation is ensured both by the intrinsic mechanics of mitosis and by an error-checking spindle assembly checkpoint. Many cancers show altered expression of proteins involved in the spindle checkpoint or in proteins implicated in other mitotic processes. To understand the role of aneuploidy in the initiation and progression of cancer, a number of spindle checkpoint genes have been disrupted in mice, most through conventional gene targeting (to create germ-line knockouts). We describe the consequence of these mutations with respect to embryonic development, tumor progression and an unexpected link to premature aging; readers are referred elsewhere [1] for a discussion of other cell cycle regulators.

Intragenic mutations in thyroid cancer

The close genotype-phenotype relationship that characterizes thyroid oncology stimulated the authors to address this article by using a mixed, genetic and phenotypic approach. As such, this article addresses the following aspects of intragenic mutations in thyroid cancer: thyroid stimulating hormone receptor and guanine-nucleotide-binding proteins of the stimulatory family mutations in hyperfunctioning tumors; mutations in RAS and other genes and aneuploidy; PAX8-PPARgamma rearrangements; BRAF mutations; mutations in oxidative phosphorylation and Krebs cycle genes in Hürthle cell tumors; mutations in succinate dehydrogenase genes in medullary carcinoma and C-cell hyperplasia; and mutations in TP53 and other genes in poorly differentiated and anaplastic carcinomas.

Preventing aneuploidy: the contribution of mitotic checkpoint proteins

Aneuploidy, an abnormal number of chromosomes, is a trait shared by most solid tumors. Chromosomal instability (CIN) manifested as aneuploidy might promote tumorigenesis and cause increased resistance to anti-cancer therapies. The mitotic checkpoint or spindle assembly checkpoint is a major signaling pathway involved in the prevention of CIN. We review current knowledge on the contribution of misregulation of mitotic checkpoint proteins to tumor formation and will address to what extent this contribution is due to chromosome segregation errors directly. We propose that both checkpoint and non-checkpoint functions of these proteins contribute to the wide array of oncogenic phenotypes seen upon their misregulation.

A novel role for thyroid hormone receptor beta in cellular radiosensitivity

Thyroid hormone receptors (THRs) widely govern cell growth, differentiation and metabolism acting in a ligand- and cofactor-dependent manner to modulate tissue-specific gene expression. Given a large variety of genes regulated by THRs and multiplicity of cellular processes potentially influenced by THRs, we addressed the role of THRB (thyroid hormone receptor beta) in cellular radiosensitivity. Wild-type and mutant THRB were overexpressed in several cell lines using an adenovirus-mediated gene delivery and their effects were examined after cell exposure to gamma-rays. Wild-type THRB decreased clonogenic survival of the cell lines with low levels of endogenous THRB, retarded their growth and synergized with radiation in decreasing proliferative potential and promoting cellular senescence. These changes were accompanied by the accumulation of p21 (CDKN1A, CIP1, WAF1) and p16 (CDKN2A, INK4a) inhibitors of cyclin-dependent kinases and by the decrease of Rb (retinoblastoma protein) phosphorylation. Mutant THRB produced a radioprotective effect, attenuated radiation-induced growth inhibition and cellular senescence. The results suggest that THRB may modulate cellular radiosensitivity and stress-induced senescence.

Aneuploidy and RAS mutations are mutually exclusive events in the development of well-differentiated thyroid follicular tumours

OBJECTIVE

Follicular thyroid tumours present several genetic alterations such as aneuploidy, RAS mutations and PAX8/PPARgammarearrangements. The molecular basis of aneuploidy remains undefined in the majority of human cancers. It has been proposed that mutations in RAS oncogenes could be related to chromosomal instability, although this issue remains controversial. The aim of our study was to investigate the correlation between aneuploidy, RAS mutations and PAX8/PPARgamma gene rearrangement in thyroid follicular tumours.

DESIGN

Ploidy status was determined by flow cytometry in 111 thyroid lesions (42 follicular thyroid adenomas, 27 follicular thyroid carcinomas, 19 follicular variants of papillary thyroid carcinoma, 20 poorly differentiated thyroid carcinomas and 3 anaplastic thyroid carcinomas). RAS mutations and PAX8/PPARgamma fusion gene were investigated in 101 and 87 of these samples, respectively.

RESULTS

Altogether, 12 of 50 (24%) diploid tumours presented RAS mutation which contrasts with 3 of 51 (5.9%; P = 0.0124) RAS mutations in the group of aneuploid tumours. The aneuploid tumours harbouring RAS mutations were two poorly differentiated carcinomas and one follicular variant of papillary thyroid carcinoma with poorly differentiated areas. None of the tumours with RAS mutations expressed the PAX8/PPARgamma fusion gene. Three of five (60%) follicular thyroid adenomas and 1 of 7 (14%) follicular thyroid carcinomas, with the PAX8/PPARgamma fusion gene, were aneuploid.

CONCLUSIONS

Our data suggest that aneuploidy and RAS mutations are mutually exclusive events in the development of well-differentiated thyroid follicular tumours.

Spindle assembly checkpoint and centrosome abnormalities in oral cancer

Like many solid tumours, oral squamous cell carcinomas (OSCC) invariably exhibit chromosomal instability (CIN) leading to aneuploidy. The mechanisms responsible for CIN in OSCC, however, are largely unknown. This study examined the fidelity of the spindle checkpoint, together with the number, structure and function of centrosomes in a series of well-characterised aneuploid immortal OSCC-derived cell lines that harbour p53 and p16(INK4A) defects. The spindle checkpoints were fully functional in 2 of 7 cell lines and attenuated in the remaining 5 cell lines. Overexpression of the spindle checkpoint protein, Cdc20, was observed in 2 of the cell lines with attenuated checkpoints. Defects in centrosome number, size and localisation were detected in 5 of the cell lines. Clonal cell populations contained cells with both normal and abnormal numbers of centrosomes, suggesting that the control of centrosome number may be inherently unstable in OSCC-derived cell lines. Centrosomal abnormalities were then examined in tissue samples of oral epithelial dysplasias and carcinomas. Abnormal centrosomes were detected in all the tissues examined albeit in a low percentage of cells (<1% to >5%). The percentage of cells containing centrosome abnormalities was significantly higher in the carcinomas than in the dysplasias (p<0.02) and in the poorly differentiated SCCs relative to their moderately differentiated (p<0.04) and well-differentiated (p<0.01) counterparts. We suggest that the genetic alterations associated with the development of the immortal phenotype, together with spindle checkpoint and centrosome defects, are responsible, albeit in part, for the complex karyotypes observed in OSCC. The presence of centrosome abnormalities in oral dysplasias raises the possibility that such defects might contribute to malignant progression.

Transforming acidic coiled-coil 3 and Aurora-A interact in human thyrocytes and their expression is deregulated in thyroid cancer tissues

Aurora-A kinase has recently been shown to be deregulated in thyroid cancer cells and tissues. Among the Aurora-A substrates identified, transforming acidic coiled-coil (TACC3), a member of the TACC family, plays an important role in cell cycle progression and alterations of its expression occur in different cancer tissues. In this study, we demonstrated the expression of the TACC3 gene in normal human thyroid cells (HTU5), and its modulation at both mRNA and protein levels during cell cycle. Its expression was found, with respect to HTU5 cells, unchanged in cells derived from a benign thyroid follicular tumor (HTU42), and significantly reduced in cell lines derived from follicular (FTC-133), papillary (B-CPAP), and anaplastic thyroid carcinomas (CAL-62 and 8305C). Moreover, in 16 differentiated thyroid cancer tissues, TACC3 mRNA levels were found, with respect to normal matched tissues, reduced by twofold in 56% of cases and increased by twofold in 44% of cases. In the same tissues, a correlation between the expression of the TACC3 and Aurora-A mRNAs was observed. TACC3 and Aurora-A interact in vivo in thyroid cells and both proteins localized onto the mitotic structure of thyroid cells. Finally, TACC3 localization on spindle microtubule was no more observed following the inhibition of Aurora kinase activity by VX-680. We propose that Aurora-A and TACC3 interaction is important to control the mitotic spindle organization required for proper chromosome segregation.

Genomic instability and increased expression of BUB1B and MAD2L1 genes in ductal breast carcinoma

In a series of invasive ductal breast carcinoma, we investigated the status of chromosomal and intrachromosomal instability by fluorescence in situ hybridisation and determined the level of mRNA expression for two genes involved in the mitotic spindle checkpoint pathway, BUB1B and MAD2L1. All breast cancers demonstrated higher chromosomal instability rates in tumor samples (average: 56.86%, range: 36.24-76.78%) than in controls (average: 11.54%, range: 9.91-14.84%) (P<0.0001). As well as intrachromosomal instability rates were elevated in tumor (average: 18.45% range: 8.34-35.8%) as compared with controls (average: 4.18% range: 3.47-4.81%) (P<0.0001). An increase in BUB1B and MAD2L1 transcripts was demonstrated in the majority of the tumor tested. BUB1B mRNA levels but not MAD2L1 levels correlated with intrachromosomal instability (r=0.722, P=0.018).

Overexpression of BUBR1 is associated with chromosomal instability in bladder cancer

BUBR1, a mitotic checkpoint protein, is a key component of the mitotic spindle checkpoint machinery. Defective BUBR1 has been proposed to contribute to chromosomal instability (CIN). To elucidate the relationship of BUBR1 expression with CIN, expression of BUBR1, numbers of centrosomes, numerical aberrations of chromosomes, and DNA ploidy were examined, and BUBR1 expression status was compared with clinicopathological parameters in 104 human urothelial bladder carcinomas. Expression of BUBR1 and numbers of centrosomes were assessed by immunohistochemistry. Numerical aberrations of chromosomes 7, 9, and 17 were evaluated by fluorescence in situ hybridization. Cancers with a large intercellular variation in centromere copy number were designated as CIN cancers. Tumors with BUBR1 overexpression were associated with CIN, DNA aneuploidy, and centrosome amplification. Array CGH revealed that BUB1B amplification and loss rarely occurred, indicating that the overexpression of BUBR1 in these bladder cancers was independent of BUB1B copy number. Overexpression of BUBR1 significantly correlated with higher histological grade, advanced pathological stage, and high cell proliferation. Overexpression of BUBR1 predicted tumor recurrence and disease progression. These data suggest that overexpression of BUBR1 is potentially a new tumor marker for estimating biological characteristics of bladder cancer.

Expression changes of the MAD mitotic checkpoint gene family in renal cell carcinomas characterized by numerical chromosome changes

Papillary and chromophobe renal cell carcinomas are characterized by multiple trisomies and monosomies, respectively, but the molecular mechanisms behind the acquisition of these numerical chromosome changes are unknown. To evaluate the role of mitotic checkpoint defects for the karyotypic patterns characteristic of these two renal cell cancer subtypes, we analyzed the messenger RNA expression levels of the major mitotic checkpoint genes of the budding uninhibited by benzimidazole family (BUB1, BUBR1, BUB3) and of the mitotic arrest deficiency family (MAD1, MAD2L1, MAD2L2) by real-time quantitative polymerase chain reaction in 30 renal cell cancer samples (11 chromophobe and 19 papillary) and 36 normal kidney tissue samples. MAD1, MAD2L1, and MAD2L2 showed significant expression differences in tumor tissue compared to controls. Chromophobe tumors presented underexpression of MAD1, and MAD2L2, whereas papillary tumors showed overexpression of MAD2L1. The expression level of the BUB gene family did not differ significantly from that of normal kidney. We conclude that expression changes in mitotic arrest deficiency genes (MAD1, MAD2L1, and MAD2L2) play a role in renal carcinogenesis characterized by multiple numerical chromosome abnormalities.

Does aneuploidy cause cancer?

Aneuploidy has been recognized as a common characteristic of cancer cells for >100 years. Aneuploidy frequently results from errors of the mitotic checkpoint, the major cell cycle control mechanism that acts to prevent chromosome missegregation. The mitotic checkpoint is often compromised in human tumors, although not as a result of germline mutations in genes encoding checkpoint proteins. Less obviously, aneuploidy of whole chromosomes rapidly results from mutations in genes encoding several tumor suppressors and DNA mismatch repair proteins, suggesting cooperation between mechanisms of tumorigenesis that were previously thought to act independently. Cumulatively, the current evidence suggests that aneuploidy promotes tumorigenesis, at least at low frequency, but a definitive test has not yet been reported.

Synuclein gamma inhibits the mitotic checkpoint function and promotes chromosomal instability of breast cancer cells

Aberrant expressions of the neuronal protein synuclein gamma (SNCG) in malignant mammary epithelial cells are strongly associated with the progression of breast cancer. SNCG is not expressed in normal breast tissues but abundantly expressed in a high percentage of invasive and metastatic breast carcinomas. Several studies have demonstrated that SNCG expression significantly stimulates proliferation, invasion, and metastasis of breast cancer cells. To elucidate the molecular and cellular mechanisms underlying the tumorigenic functions of SNCG, we investigated the effects of SNCG expression on the mitotic checkpoint function of breast cancer cells. By conducting several different lines of investigations, we now demonstrate that SNCG expression in breast cancer cells overrides the mitotic checkpoint control and confers the cellular resistance to anti-microtubule drug-caused apoptosis. We further show that the inhibitory effects of SNCG on mitotic checkpoint can be overthrown by enforced overexpression of the mitotic checkpoint protein BubR1 in SNCG-expressing cells. These new findings combined with our previous observation that SNCG intracellularly associates with BubR1 together suggest that SNCG expression compromises the mitotic checkpoint control by inhibition of the normal function of BubR1, thereby promoting genetic instability. Genetic instability is recognized as an important contributing factor in tumorigenesis. Hence, our studies gain insight into the mechanisms whereby SNCG expression advances breast cancer disease progression and fasters tumor metastasis.

Expression of Aurora kinases in human thyroid carcinoma cell lines and tissues

The Aurora kinases are involved in the regulation of cell cycle progression, and alterations in their expression have been shown to associate with cell malignant transformation. In the present study, we demonstrated that human thyrocytes express all 3 Aurora kinases (A, B and C) at both protein and mRNA level and this expression is cell cycle-regulated. An increase in the protein level of the 3 kinases was found, with respect to normal human thyrocytes (HTU5), in the human cell lines derived from follicular (FTC-133), papillary (B-CPAP) and anaplastic (8305C) thyroid carcinomas, but not in cells derived from a follicular adenoma (HTU42). These observations were mirrored in RT-PCR experiments for Aurora-A and B. In contrast, Aurora-C mRNA levels were not significantly different among the different cell types analyzed, suggesting that posttranscriptional mechanism(s) modulate its expression. The expression at the protein level of all 3 Aurora kinases was significantly higher in 3 thyroid papillary carcinomas with respect to normal matched tissues obtained from the same patients. Similar modifications, at the mRNA level, could be observed in 7 papillary carcinoma tissues for Aurora-A and B, but not for Aurora-C. In conclusion, we demonstrated that normal human thyrocytes express all 3 members of the Aurora kinase family, and their expression is amplified in malignant thyroid cell lines and tissues. These results suggest that the Aurora kinases may play a relevant role in malignant thyroid cancers, and may represent a putative therapeutic target for thyroid neoplasms.

On the road to cancer: aneuploidy and the mitotic checkpoint

Abnormal chromosome content - also known as aneuploidy - is the most common characteristic of human solid tumours. It has therefore been proposed that aneuploidy contributes to, or even drives, tumour development. The mitotic checkpoint guards against chromosome mis-segregation by delaying cell-cycle progression through mitosis until all chromosomes have successfully made spindle-microtubule attachments. Defects in the mitotic checkpoint generate aneuploidy and might facilitate tumorigenesis, but more severe disabling of checkpoint signalling is a possible anticancer strategy.

Aurora B overexpression associates with the thyroid carcinoma undifferentiated phenotype and is required for thyroid carcinoma cell proliferation

Alterations in chromosome number (aneuploidy) are common in human neoplasias. Loss of mitotic regulation is believed to induce aneuploidy in cancer cells and act as a driving force during the malignant progression. The serine/theronine protein kinases of aurora family genes play a critical role in the regulation of key cell cycle processes. Aurora B mediates chromosome segregation by ensuring orientation of sister chromatids and overexpression of Aurora B in diploid human cells NHDF (normal human diploid fibroblast) induces multinuclearity. We analyzed Aurora B expression in human thyroid carcinomas. Cell lines originating from different histotypes showed an increase in Aurora B expression. Immunohistochemical analysis of archive samples showed a high expression of Aurora B in anaplastic thyroid carcinomas; conversely, Aurora B expression was not detectable in normal thyroid tissue. Real-time PCR analysis confirmed a strong expression of Aurora B in anaplastic thyroid carcinomas. The block of Aurora B expression induced by RNA interference or by using an inhibitor of Aurora kinase activity significantly reduced the growth of thyroid anaplastic carcinoma cells.

Stuck in division or passing through: what happens when cells cannot satisfy the spindle assembly checkpoint

Cells that cannot satisfy the spindle assembly checkpoint (SAC) are delayed in mitosis (D-mitosis), a fact that has useful clinical ramifications. However, this delay is seldom permanent, and in the presence of an active SAC most cells ultimately escape mitosis and enter the next G1 as tetraploid cells. This review defines and discusses the various factors that determine how long a cell remains in mitosis when it cannot satisfy the SAC and also discusses the cell's subsequent fate.

Elevated level of spindle checkprotein MAD2 correlates with cellular mitotic arrest, but not with aneuploidy and clinicopathological characteristics in gastric cancer

AIM: To study the relevance of spindle assembly checkprotein MAD2 to cellular mitotic status, aneuploidy and other clinicopathological characteristics in gastric cancer.

METHODS: Western blot analyses were performed to analyze the protein levels of MAD2 and cyclin B1 in the tumorous and adjacent nontumorous tissues of 34 gastric cancer patients. Cell cycle distribution and DNA ploidy of cancer tissues were also determined by flow cytometry. Conventional statistical methods were adopted to determine the relevance of abnormal MAD2 level to mitotic status, aneuploidy and clinicopathological parameters.

RESULTS: Out of 34 gastric cancer patients 25 (74%) exhibited elevated MAD2 levels in their tumorous tissues compared with the corresponding nontumorous tissues. Elevation of MAD2 levels significantly correlated with the increased levels of cyclin B1 expression and G₂/M-phase distribution (P = 0.038 and P = 0.033, respectively), but was not relevant to aneuploidy. The gastric cancer patients with elevated MAD2 levels showed a tendency toward better disease-free and overall survival (P > 0.05). However, no association was found between elevated MAD2 levels and patients’ clinicopathological characteristics.

CONCLUSION: Elevation of MAD2 level is present in 74% of gastric cancer patients, and correlates with increased mitotic checkpoint activity. However, elevation of MAD2 level is not associated with patients aneuploidy and any of the clinicopathological characteristics.

Expression of BUB1 protein in gastric cancer correlates with the histological subtype, but not with DNA ploidy or microsatellite instability

During mitosis, the spindle checkpoint delays the onset of anaphase until all chromosomes have attached properly to the mitotic spindle, preventing chromosome missegregation. BUB (budding uninhibited by benzimidazole) 1 is one of the key components of this checkpoint. BUB1 mutations are rare in cancer tissues and no mutations have been identified in gastric cancer. In mice, immunodepletion of BUB1 abolished the spindle checkpoint. Thus, aberrant expression of BUB1 protein could impair mitotic checkpoint function, resulting in aneuploidy, a common phenomenon in gastric cancer. In the present study, an antibody was generated against BUB1 and its expression was studied in gastric cancer tissue sections (n = 80) by immunohistochemistry. Nuclear BUB1 expression was found in all gastric cancer cases. The proportion of tumour cells expressing BUB1 was significantly greater in diffuse-type than in intestinal-type gastric carcinoma (p < 0.001). No correlation was found between BUB1 expression and deoxyribonucleic acid (DNA) ploidy, microsatellite instability or any other histopathological parameters investigated. To the authors' knowledge, this is the first study of BUB1 protein expression in gastric cancer tissues. Different BUB1 protein expression levels in intestinal- and diffuse-type gastric cancer may provide further evidence of a potential link between different genetic pathways and morphological phenotype in gastric carcinogenesis. However, further studies are needed to establish whether there is an association between BUB1 protein expression level and mitotic spindle checkpoint function in gastric cancer.

The spindle checkpoint: from normal cell division to tumorigenesis

Faithful chromosome segregation during each cell division is regulated by the spindle checkpoint. This surveillance mechanism monitors kinetochore-microtubule attachment and the integrity of the mitotic apparatus, delaying mitotic exit until all chromosomes are properly aligned at the metaphase plate. Failure of this mechanism can generate gross aneuploidy. Since its discovery, mutations in genes involved in the spindle checkpoint response were predicted to be serious candidates for the chromosomal instability phenotype observed in many tumors. During the last few years, significant advances have been made in understanding the molecular basis of the spindle checkpoint. However, many studies of tumor cell lines and primary cancer isolates have failed to show a direct correlation with mutations in spindle checkpoint components. Nevertheless, it was shown that many tumor cells have an abnormal spindle checkpoint. Therefore, better understanding of the molecular mechanisms involved in regulation of spindle checkpoint response are expected to provide important clues regarding the mechanisms underlying the emergence of neoplasia.

AuroraA overexpression overrides the mitotic spindle checkpoint triggered by nocodazole, a microtubule destabilizer

AuroraA, a mitotic kinase, is reported to be amplified and overexpressed in a variety of human tumors. Active mutants of AuroraA can transform mouse fibroblasts and form tumors in nude mice. However, the mechanism behind this oncogenic potential remains elusive. In this study, we investigated the consequences of AuroraA overexpression and showed that increased AuroraA levels compromise the mitotic spindle checkpoint triggered by nocodazole, a microtubule polymerization inhibitor. This is accomplished by disrupting the proper assembly of the mitotic checkpoint complex at the level of the Cdc20-BubR1 interaction. As a result, the spindle checkpoint complex fails to form and cells progress through mitosis without proper arrest in response to nocodazole. This ability to override the mitotic spindle checkpoint was found to be independent of AuroraA kinase activity. We conclude that maintenance of a functional balance between AuroraA and mitotic checkpoint proteins is essential for the proper progression through mitosis. This study therefore offers a possible explanation of how deregulation of AuroraA can contribute to genetic instability and tumorigenesis.

Breast cancer-specific gene 1 interacts with the mitotic checkpoint kinase BubR1

The abnormal expression of breast cancer-specific gene 1 (BCSG1) in malignant mammary epithelial cells is highly associated with the development and progression of breast cancer. A series of in vitro and in vivo studies performed in our laboratory and others have demonstrated that BCSG1 expression significantly stimulates proliferation, invasion, and metastasis of breast cancer cells. However, currently little is known about how BCSG1 exerts its oncogenic functions. To elucidate the cellular mechanisms underlying the effects of BCSG1 in breast cancer cells, we used a yeast two-hybrid system to screen for proteins that could associate with BCSG1. Through this screening, we identified the mitotic checkpoint protein BubR1 as a novel binding partner of BCSG1. The specific association of BCSG1 with BubR1 in breast cancer cells was demonstrated by immunoprecipitation and GST pull-down assays. Intriguingly, experiments conducted in four different cell lines all showed that exogenous expressions of BCSG1 consistently reduce the cellular levels of the BubR1 protein without affecting BubR1 mRNA expression. The tendency of endogenous BCSG1 expression coinciding with lower BubR1 protein levels was also observed in seven out of eight breast cancer cell lines. We further showed that the reducing effect of BCSG1 on BubR1 protein expression could be prevented by treating BCSG1-transfected cells with MG-132, a selective 26S proteasome inhibitor, implying that the proteasome machinery may be involved in the BCSG1-induced reduction of the BubR1 protein. Accompanied with a reduction of BubR1 protein level, BCSG1 expression resulted in multinucleation of breast cancer cells upon treatment with spindle inhibitor nocodazole, indicating an impaired mitotic checkpoint. Taken together, our novel findings suggest that BCSG1 may accelerate the progression of breast cancer at least in part by compromising the mitotic checkpoint control through inactivation of BubR1.

Thyroid carcinoma

Thyroid carcinomas are fairly uncommon and include disease types that range from indolent localised papillary carcinomas to the fulminant and lethal anaplastic disease. Several attempts to formulate a consensus about treatment of thyroid carcinoma have resulted in published guidelines for diagnosis and initial disease management. Multimodality treatments are widely recommended, although there is little evidence from prospective trials to support this approach. Surgical resection to achieve local disease control remains the cornerstone of primary treatment for most thyroid cancers, and is often followed by adjuvant radioiodine treatment for papillary and follicular types of disease. Thyroid hormone replacement therapy is used not only to rectify postsurgical hypothyroidism, but also because there is evidence to suggest that high doses that suppress thyroid stimulating hormone prevent disease recurrence in patients with papillary or follicular carcinomas. Treatment for progressive metastatic disease is often of limited benefit, and there is a pressing need for novel approaches in treatment of patients at high risk of disease-related death. In families with inherited thyroid cancer syndromes, early diagnosis and intervention based on genetic testing might prevent poor disease outcomes. Care should be carefully coordinated by members of an experienced multidisciplinary team, and patients should be provided with education about diagnosis, prognosis, and treatment options to allow them to make informed contributions to decisions about their care.