Increased expression of centrosomal alpha, gamma-tubulin in atypical ductal hyperplasia and carcinoma of the breast

TuBG1 promotes hepatocellular carcinoma via ATR/P53-apoptosis and cycling pathways

BACKGROUND

As reported, γ-tubulin (TuBG1) is related to the occurrence and development of various types of malignant tumors. However, its role in hepatocellular cancer (HCC) is not clear. The present study was to investigate the relationship between TuBG1 and clinical parameters and survival in HCC patients.

METHODS

The correlation between TuBG1 and clinical parameters and survival in HCC patients was explored by bioinformatics analysis. Immunohistochemistry was used for the verification. The molecular function of TuBG1 was measured using colony formation, scratch assay, trans-well assay and flow cytometry. Gene set enrichment analysis (GSEA) was used to pick up the enriched pathways, followed by investigating the target pathways using Western blotting. The tumor-immune system interactions and drug bank database (TISIDB) was used to evaluate TuBG1 and immunity. Based on the TuBG1-related immune genes, a prognostic model was constructed and was further validated internally and externally.

RESULTS

The bioinformatic analysis found high expressed TuBG1 in HCC tissue, which was confirmed using immunohistochemistry and Western blotting. After silencing the TuBG1 in HCC cell lines, more G1 arrested cells were found, cell proliferation and invasion were inhibited, and apoptosis was promoted. Furthermore, the silence of TuBG1 increased the expressions of Ataxia-Telangiectasia and Rad-3 (ATR), phospho-P38 mitogen-activated protein kinase (P-P38MAPK), phospho-P53 (P-P53), B-cell lymphoma-2 associated X protein (Bax), cleaved caspase 3 and P21; decreased the expressions of B-cell lymphoma-2 (Bcl-2), cyclin D1, cyclin E2, cyclin-dependent kinase 2 (CDK2) and CDK4. The correlation analysis of immunohistochemistry and clinical parameters and survival data revealed that TuBG1 was negatively correlated with the overall survival. The constructed immune prognosis model could effectively evaluate the prognosis.

CONCLUSIONS

The increased expression of TuBG1 in HCC is associated with poor prognosis, which might be involved in the occurrence and development of HCC.

Epigenetic alterations impede epithelial-mesenchymal transition by modulating centrosome amplification and Myc/RAS axis in triple negative breast cancer cells

Alterations in centrosome proteins may result in centrosome abnormalities such as disorganized spindles and centrosome amplification, leading to aneuploidy and genomic instability. Centrosomes exhibit unique epigenetic properties in which structural or positional information is propagated through somatic lineage by non-genetic pathways. Excessive centrosome amplification in breast cancer is accompanied by efficient clustering and loss of E-cadherin, indicating an important adaptive mechanism of cancer. This study sought to elucidate the effect of epigenetic alterations on centrosome amplification, epithelial-mesenchymal transition (EMT) and apoptosis in triple negative human breast adenocarcinoma derived MDA-MB-231 cell line. The results obtained here show that siRNA mediated silencing of DNMT1 and specific inhibition of HDAC1 & HDAC2 by Tricostatin A (TSA) synergistically inhibit cell proliferation through modulation of centrosome proteins γ-tubulin, TUBGCP2 and pericentrin. In addition, induction of apoptosis was observed by downregulation of Bcl2, upregulation of Bax and activation of PARP cleavage. Inhibition of EMT was confirmed through upregulation of E-cadherin and downregulation of N-cadherin and vimentin. Similarly, downregulation of Myc, RAS and CDK2, which plays important roles in proliferation and survival, was observed. Nuclear protein analysis revealed downregulation in the nuclear translocation of E2F1, which regulates centrosome amplification and metastasis in breast cancer. In conclusion, this study confirmed the role of epigenetic regulators in centrosome amplification and suggests that inhibition of DNA methylation and histone deacetylation-mediated chromatin remodelling synergistically disrupt EMT through modulation of centrosome amplification and Myc/RAS axis to potentiate apoptosis and attenuate cell proliferation in triple negative breast cancer cells.

Kinesin Family Member C1 (KIFC1/HSET): A Potential Actionable Biomarker of Early Stage Breast Tumorigenesis and Progression of High-Risk Lesions

The enigma of why some premalignant or pre-invasive breast lesions transform and progress while others do not remains poorly understood. Currently, no radiologic or molecular biomarkers exist in the clinic that can successfully risk-stratify high-risk lesions for malignant transformation or tumor progression as well as serve as a minimally cytotoxic actionable target for at-risk subpopulations. Breast carcinogenesis involves a series of key molecular deregulatory events that prompt normal cells to bypass tumor-suppressive senescence barriers. Kinesin family member C1 (KIFC1/HSET), which confers survival of cancer cells burdened with extra centrosomes, has been observed in premalignant and pre-invasive lesions, and its expression has been shown to correlate with increasing neoplastic progression. Additionally, KIFC1 has been associated with aggressive breast tumor molecular subtypes, such as basal-like and triple-negative breast cancers. However, the role of KIFC1 in malignant transformation and its potential as a predictive biomarker of neoplastic progression remain elusive. Herein, we review compelling evidence suggesting the involvement of KIFC1 in enabling pre-neoplastic cells to bypass senescence barriers necessary to become immortalized and malignant. We also discuss evidence inferring that KIFC1 levels may be higher in premalignant lesions with a greater inclination to transform and acquire aggressive tumor intrinsic subtypes. Collectively, this evidence provides a strong impetus for further investigation into KIFC1 as a potential risk-stratifying biomarker and minimally cytotoxic actionable target for high-risk patient subpopulations.

Dysregulation of Microtubule Nucleating Proteins in Cancer Cells

Simple Summary

The dysfunction of microtubule nucleation in cancer cells changes the overall cytoskeleton organization and cellular physiology. This review focuses on the dysregulation of the γ-tubulin ring complex (γ-TuRC) proteins that are essential for microtubule nucleation. Recent research on the high-resolution structure of γ-TuRC has brought new insight into the microtubule nucleation mechanism. We discuss the effect of γ-TuRC protein overexpression on cancer cell behavior and new drugs directed to γ-tubulin that may offer a viable alternative to microtubule-targeting agents currently used in cancer chemotherapy.

Abstract

In cells, microtubules typically nucleate from microtubule organizing centers, such as centrosomes. γ-Tubulin, which forms multiprotein complexes, is essential for nucleation. The γ-tubulin ring complex (γ-TuRC) is an efficient microtubule nucleator that requires additional centrosomal proteins for its activation and targeting. Evidence suggests that there is a dysfunction of centrosomal microtubule nucleation in cancer cells. Despite decades of molecular analysis of γ-TuRC and its interacting factors, the mechanisms of microtubule nucleation in normal and cancer cells remains obscure. Here, we review recent work on the high-resolution structure of γ-TuRC, which brings new insight into the mechanism of microtubule nucleation. We discuss the effects of γ-TuRC protein dysregulation on cancer cell behavior and new compounds targeting γ-tubulin. Drugs inhibiting γ-TuRC functions could represent an alternative to microtubule targeting agents in cancer chemotherapy.

Cyanidin 3-glucoside modulated cell cycle progression in liver precancerous lesion, in vivo study

BACKGROUND

Cyanidin-3-O-glucoside (cyan) exhibits antioxidant and anticancer properties. The cell cycle proteins and antimitotic drugs might be promising therapeutic targets in hepatocellular carcinoma.

AIM

To investigate the effect of cyan administration on cell cycle in hepatic precancerous lesion (PCL) induced by diethylnitrosamine/2-acetylaminofluorene (DEN/2-AAF) in Wistar rats.

METHODS

In vivo, DEN/2-AAF-induced hepatic PCL, rats were treated with three doses of cyan (10, 15, and 20 mg/kg/d, for four consecutive days per week for 16 wk). Blood and liver tissue samples were collected for measurement of the followings; alpha fetoprotein (AFP) liver function and RNA panel differential expression was evaluated via real time polymerase chain reaction. Histopathological examination of liver sections stained with H&E and immunohistochemical study using glutathione S-transferase placental (GSTP) and proliferating cell nuclear antigen (PCNA) antibodies were assessed.

RESULTS

Cyan administration mitigated the effect of DEN/2-AFF induced PCL, decreased AFP levels, and improved liver function. Remarkably, treatment with cyan dose dependently decreased the long non-coding RNA MALAT1 and tubulin gamma 1 mRNA expressions and increased the levels of miR-125b, all of which are involved in cell cycle and mitotic spindle assembly. Of note, cyan decreased GSTP foci percent area and PCNA positively stained nuclei.

CONCLUSION

Our results indicated that cyan could be used as a potential therapeutic agent to inhibit liver carcinogenesis in rat model via modulation of cell cycle.

Gravin-associated kinase signaling networks coordinate γ-tubulin organization at mitotic spindle poles

Mitogenic signals that regulate cell division often proceed through multienzyme assemblies within defined intracellular compartments. The anchoring protein Gravin restricts the action of mitotic kinases and cell-cycle effectors to defined mitotic structures. In this report we discover that genetic deletion of Gravin disrupts proper accumulation and asymmetric distribution of γ-tubulin during mitosis. We utilize a new precision pharmacology tool, Local Kinase Inhibition, to inhibit the Gravin binding partner polo-like kinase 1 at spindle poles. Using a combination of gene-editing approaches, quantitative imaging, and biochemical assays, we provide evidence that disruption of local polo-like kinase 1 signaling underlies the γ-tubulin distribution defects observed with Gravin loss. Our study uncovers a new role for Gravin in coordinating γ-tubulin recruitment during mitosis and illuminates the mechanism by which signaling enzymes regulate this process at a distinct subcellular location.

Choreography of the centrosome

More than a century ago, the centrosome was discovered and described as “the true division organ of the cell”. Electron microscopy revealed that a centrosome is an amorphous structure or pericentriolar protein matrix that surrounds a pair of well-organized centrioles. Today, the importance of the centrosome as a microtubule-organizing center and coordinator of the mitotic spindle is questioned, because centrioles are absent in up to half of all known eukaryotic species, and various mechanisms for acentrosomal microtubule nucleation have been described. This review recapitulates the known functions of centrosome movements in cellular homeostasis and discusses knowledge gaps in this field.

Combined approach of homology modeling, molecular dynamics, and docking: computer-aided drug discovery

With the continuous development in software, algorithms, and increase in computer speed, the field of computer-aided drug design has been witnessing reduction in the time and cost of the drug designing process. Structure based drug design (SBDD), which is based on the 3D structure of the enzyme, is helping in proposing novel inhibitors. Although a number of crystal structures are available in various repositories, there are various proteins whose experimental crystallization is difficult. In such cases, homology modeling, along with the combined application of MD and docking, helps in establishing a reliable 3D structure that can be used for SBDD. In this review, we have reported recent works, which have employed these three techniques for generating structures and further proposing novel inhibitors, for cytoplasmic proteins, membrane proteins, and metal containing proteins. Also, we have discussed these techniques in brief in terms of the theory involved and the various software employed. Hence, this review can give a brief idea about using these tools specifically for a particular problem.

γ-Tubulin⁻γ-Tubulin Interactions as the Basis for the Formation of a Meshwork

In cytoplasm, protein γ-tubulin joins with various γ-tubulin complex proteins (GCPs) to form a heterotetramer γ-tubulin small complex (γ-TuSC) that can grow into a ring-shaped structure called the γ-tubulin ring complex (γ-TuRC). Both γ-TuSC and γ-TuRC are required for microtubule nucleation. Recent knowledge on γ-tubulin with regard to its cellular functions beyond participation in its creation of microtubules suggests that this protein forms a cellular meshwork. The present review summarizes the recognized functions of γ-tubulin and aims to unite the current views on this protein.

γ-tubulin as a signal-transducing molecule and meshwork with therapeutic potential

Knowledge of γ-tubulin is increasing with regard to the cellular functions of this protein beyond its participation in microtubule nucleation. γ-Tubulin expression is altered in various malignancies, and changes in the TUBG1 gene have been found in patients suffering from brain malformations. This review recapitulates the known functions of γ-tubulin in cellular homeostasis and discusses the possible influence of the protein on disease development and cancer.

Increased centrosome number in BRCA-related breast cancer specimens determined by immunofluorescence analysis

BRCA‐related breast carcinoma can be prevented through prophylactic surgery and an intensive follow‐up regimen. However, BRCA genetic tests cannot be routinely performed, and some BRCA mutations could not be defined as deleterious mutations or normal variants. Therefore, an easy functional assay of BRCA will be useful to evaluate BRCA status. As it has been reported that BRCA functions in the regulation of centrosome number, we focused on centrosome number in cancer tissues. Here, 70 breast cancer specimens with known BRCA status were analyzed using immunofluorescence of γ‐tubulin (a marker of centrosome) foci. The number of foci per cell was higher in cases with BRCA mutation compared to wild‐type cases, that is, 1.9 (95% confidence interval [CI], 1.5‐2.3) vs 0.5 (95% CI, 0.2‐0.8) (P < .001). Specifically, foci numbers per cell in BRCA1 and BRCA2 mutation cases were 1.2 (95% CI, 0.6‐1.8) and 2.2 (95% CI, 1.7‐2.6), respectively, both higher than those in wild‐type cases (P = .042 and P < .0001, respectively). The predictive value of γ‐tubulin foci as determined by area under the curve (AUC = 0.86) for BRCA status was superior to BRCAPRO (AUC = 0.69), Myriad Table (AUC = 0.61), and KOHBRA BRCA risk calculator (AUC = 0.65) pretest values. The use of γ‐tubulin foci to predict BRCA status had sensitivity = 83% (19/23), specificity = 89% (42/47), and positive predictive value = 77% (20/26). Thus, γ‐tubulin immunofluorescence, a functional assessment of BRCA, can be used as a new prospective test of BRCA status.

Familial resemblances in human whole blood transcriptome

Background

Considering the implication of gene expression in the susceptibility of chronic diseases and the familial clustering of chronic diseases, the study of familial resemblances in gene expression levels is then highly relevant. Few studies have considered the contribution of both genetic and common environmental effects to familial resemblances in whole blood gene expression levels. The objective is to quantify the contribution of genetic and common environmental effects in the familial resemblances of whole blood genome-wide gene expression levels. We also make comparisons with familial resemblances in blood leukocytes genome-wide DNA methylation levels in the same cohort in order to further investigate biological mechanisms.

Results

Maximal heritability, genetic heritability, and common environmental effect were computed for all probes (20.6%, 15.6%, and 5.0% respectively) and for probes showing a significant familial effect (78.1%, 60.1%, and 18.0% respectively). Pairwise phenotypic correlations between gene expression and DNA methylation levels adjusted for blood cell heterogeneity were computed for probes showing significant familial effect. A total of 78 probe pairs among the 7,618,401 possible pairs passed Bonferroni correction (corrected P-value = 6.56 × 10^− 9). Significant genetic correlations between gene expression and DNA methylation levels were found for 25 probe pairs (absolute genetic correlation of 0.97).

Conclusions

Familial resemblances in gene expression levels were mainly attributable to genetic factors, but common environmental effect also played a role especially in probes showing a significant familial effect. Probes and CpG sites with familial effect seem to be under a strong shared genetic control.

Electronic supplementary material

The online version of this article (10.1186/s12864-018-4698-6) contains supplementary material, which is available to authorized users.

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

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

Human TUBG2 gene is expressed as two splice variant mRNA and involved in cell growth

In mammals, γ-tubulin, a key protein in microtubule nucleation, is encoded by two genes, TUBG1 and TUBG2. Human TUBG1 and TUBG2 mRNA are expressed ubiquitously and predominantly in preimplantation embryos and the brain, respectively, but specific detection of γ-tubulin2 protein expression is difficult due to their high sequence similarity. Here, we describe a protocol for differential detection of two human γ-tubulins by western blotting. In several cancer cell lines and the brain, expression of γ-tubulin2 along with γ-tubulin1 and a novel TUBG2 splice variant are identified. Contribution of ectopically expressed γ-tubulin2 in cancer growth was determined by depletion of γ-tubulin2.

HSET overexpression fuels tumor progression via centrosome clustering-independent mechanisms in breast cancer patients

Human breast tumors harbor supernumerary centrosomes in almost 80% of tumor cells. Although amplified centrosomes compromise cell viability via multipolar spindles resulting in death-inducing aneuploidy, cancer cells tend to cluster extra centrosomes during mitosis. As a result cancer cells display bipolar spindle phenotypes to maintain a tolerable level of aneuploidy, an edge to their survival. HSET/KifC1, a kinesin-like minus-end directed microtubule motor has recently found fame as a crucial centrosome clustering molecule. Here we show that HSET promotes tumor progression via mechanisms independent of centrosome clustering. We found that HSET is overexpressed in breast carcinomas wherein nuclear HSET accumulation correlated with histological grade and predicted poor progression-free and overall survival. In addition, deregulated HSET protein expression was associated with gene amplification and/or translocation. Our data provide compelling evidence that HSET overexpression is pro-proliferative, promotes clonogenic-survival and enhances cell-cycle kinetics through G2 and M-phases. Importantly, HSET co-immunoprecipitates with survivin, and its overexpression protects survivin from proteasome-mediated degradation, resulting in its increased steady-state levels. We provide the first evidence of centrosome clustering-independent activities of HSET that fuel tumor progression and firmly establish that HSET can serve both as a potential prognostic biomarker and as a valuable cancer-selective therapeutic target.

γ-Tubulin complexes in microtubule nucleation and beyond

Tremendous progress has been made in understanding the functions of γ-tubulin and, in particular, its role in microtubule nucleation since the publication of its discovery in 1989. The structure of γ-tubulin has been determined, and the components of γ-tubulin complexes have been identified. Significant progress in understanding the structure of the γ-tubulin ring complex and its components has led to a persuasive model for how these complexes nucleate microtubule assembly. At the same time, data have accumulated that γ-tubulin has important but less well understood functions that are not simply a consequence of its function in microtubule nucleation. These include roles in the regulation of plus-end microtubule dynamics, gene regulation, and mitotic and cell cycle regulation. Finally, evidence is emerging that γ-tubulin mutations or alterations of γ-tubulin expression play an important role in certain types of cancer and in other diseases.

Combined molecular dynamics and continuum solvent approaches (MM-PBSA/GBSA) to predict noscapinoid binding to γ-tubulin dimer

γ-tubulin plays crucial role in the nucleation and organization of microtubules during cell division. Recent studies have also indicated its role in the regulation of microtubule dynamics at the plus end of the microtubules. Moreover, γ-tubulin has been found to be over-expressed in many cancer types, such as carcinomas of the breast and glioblastoma multiforme. These studies have led to immense interest in the identification of chemical leads that might interact with γ-tubulin and disrupt its function in order to explore γ-tubulin as potential chemotherapeutic target. Recently a colchicine-interacting cavity was identified at the interface of γ-tubulin dimer that might also interact with other similar compounds. In the same direction we theoretically investigated binding of a class of compounds, noscapinoids (noscapine and its derivatives) at the interface of the γ-tubulin dimer. Molecular interaction of noscapine and two of its derivatives, amino-noscapine and bromo-noscapine, was investigated by molecular docking, molecular dynamics simulation and binding free energy calculation. All noscapinoids displayed stable interaction throughout simulation of 25 ns. The predictive binding free energy (ΔGbind) indicates that noscapinoids bind strongly with the γ-tubulin dimer. However, bromo-noscapine showed the best binding affinity (ΔGbind = -37.6 kcal/mol) followed by noscapine (ΔGbind = -29.85 kcal/mol) and amino-noscapine (ΔGbind = -23.99 kcal/mol) using the MM-PBSA method. Similarly using the MM-GBSA method, bromo-noscapine showed highest binding affinity (ΔGbind = -43.64 kcal/mol) followed by amino-noscapine (ΔGbind = -37.56 kcal/mol) and noscapine (ΔGbind = -34.57 kcal/mol). The results thus generate compelling evidence that these noscapinoids may hold great potential for preclinical and clinical evaluation.

Emerging microtubule targets in glioma therapy

Major advances in the genomics and epigenomics of diffuse gliomas and glioblastoma to date have not been translated into effective therapy, necessitating pursuit of alternative treatment approaches for these therapeutically challenging tumors. Current knowledge of microtubules in cancer and the development of new microtubule-based treatment strategies for high-grade gliomas are the topic in this review article. Discussed are cellular, molecular, and pharmacologic aspects of the microtubule cytoskeleton underlying mitosis and interactions with other cellular partners involved in cell cycle progression, directional cell migration, and tumor invasion. Special focus is placed on (1) the aberrant overexpression of βIII-tubulin, a survival factor associated with hypoxic tumor microenvironment and dynamic instability of microtubules; (2) the ectopic overexpression of γ-tubulin, which in addition to its conventional role as a microtubule-nucleating protein has recently emerged as a transcription factor interacting with oncogenes and kinases; (3) the microtubule-severing ATPase spastin and its emerging role in cell motility of glioblastoma cells; and (4) the modulating role of posttranslational modifications of tubulin in the context of interaction of microtubules with motor proteins. Specific antineoplastic strategies discussed include downregulation of targeted molecules aimed at achieving a sensitization effect on currently used mainstay therapies. The potential role of new classes of tubulin-binding agents and ATPase inhibitors is also examined. Understanding the cellular and molecular mechanisms underpinning the distinct behaviors of microtubules in glioma tumorigenesis and drug resistance is key to the discovery of novel molecular targets that will fundamentally change the prognostic outlook of patients with diffuse high-grade gliomas.

PPM1D overexpression predicts poor prognosis in non-small cell lung cancer

It has been reported that protein phosphatase, Mg(2+)/Mn(2+) dependent, 1D (PPM1D) plays an important role in cancer tumorigenesis. However, the clinical and functional significance of PPM1D expression has not been characterized previously in non-small cell lung cancer (NSCLC). The purpose of this study was to assess PPM1D expression and to explore its contribution to NSCLC. We examined PPM1D messenger RNA (mRNA) expression in 53 NSCLC tissues and matched adjacent noncancerous tissues by quantitative reverse transcription PCR (qRT-PCR). Furthermore, the PPM1D protein expression was analyzed by immunohistochemistry in 157 NSCLC samples. The relationship between PPM1D expression and clinicopathological features was analyzed by appropriate statistics. Kaplan-Meier analysis and Cox proportional hazards regression models were used to investigate the correlation between PPM1D expression and prognosis of NSCLC patients. The relative mRNA expression of PPM1D was significantly elevated in NSCLC tissues as compared with adjacent noncancerous tissues (P < 0.001). The high expression of PPM1D in NSCLC tissues was significantly correlated with tumor grade (P = 0.006), tumor size (P = 0.017), clinical stage (P = 0.001), and lymph node metastases (P = 0.002). Kaplan-Meier survival analysis revealed that high PPM1D expression correlated with poor prognosis of NSCLC patients (P < 0.001). Multivariate analysis showed that PPM1D expression was an independent prognostic marker for overall survival of NSCLC patients. In conclusion, PPM1D plays an important role in the progression of NSCLC. PPM1D may potentially be used as an independent biomarker for the prognostic evaluation of NSCLC.

OCT4 expression and vasculogenic mimicry formation positively correlate with poor prognosis in human breast cancer

To evaluate the prognostic value of OCT4 expression and vasculogenic mimicry (VM) in human breast cancer, we examined OCT4 expression and VM formation using immunohistochemistry and CD31/PAS (periodic acid-schiff) double staining on 90 breast cancer specimens. All patients were followed up for five-149 months following surgery. Survival curves were generated using Kaplan-Meier method. Multivariate analysis was performed using Cox regression model to assess the prognostic values. Results showed positive correlation between OCT4 expression and VM formation (p<0.05). Both OCT4 expression and VM were also positively correlated with lymph node metastasis, higher histological grade, and Nottingham prognostic index (p<0.05). Patients with OCT4 expression or VM formation exhibited poorer overall survival (OS) and disease-free survival (DFS) than OCT4-negative or VM-negative patients (p<0.05). OCT4-positive/VM-positive patients also had the worst OS and DFS (p<0.05). In multivariate survival analysis, VM, Nottingham prognostic index (NPI), and Her2 were independent prognostic factors related to OS and OCT4-positive/VM-positive patients, whereas NPI and Her2 were independent predictors of DFS. These results suggest that a combined OCT4 expression/VM could improve the prognostic judgment for breast cancer patients.

Kinesin-14 and kinesin-5 antagonistically regulate microtubule nucleation by γ-TuRC in yeast and human cells

Bipolar spindle assembly is a critical control point for initiation of mitosis through nucleation and organization of spindle microtubules and is regulated by kinesin-like proteins. In fission yeast, the kinesin-14 Pkl1 binds the γ-tubulin ring complex (γ-TuRC) microtubule-organizing centre at spindle poles and can alter its structure and function. Here we show that kinesin-14 blocks microtubule nucleation in yeast and reveal that this inhibition is countered by the kinesin-5 protein, Cut7. Furthermore, we demonstrate that Cut7 binding to γ-TuRC and the Cut7 BimC domain are both required for inhibition of Pkl1. We also demonstrate that a yeast kinesin-14 peptide blocks microtubule nucleation in two human breast cancer cell lines, suggesting that this mechanism is evolutionarily conserved. In conclusion, using genetic, biochemical and cell biology approaches we uncover antagonistic control of microtubule nucleation at γ-TuRC by two kinesin-like proteins, which may represent an attractive anti-mitotic target for cancer therapies.

Mitotic spindle assembly requires strict control of microtubule nucleation by γ-tubulin ring complexes. Olmsted et al. report that the kinesin-like proteins Pkl1 and Cut7 antagonistically regulate nucleation in fission yeast, and show that a Pkl1 peptide blocks spindle assembly in human cancer cells.

Aberrant expression of NEK2 and its clinical significance in non-small cell lung cancer

The purpose of the present study was to identify a potential biomarker that is more effective than those already available for the prognosis of non-small cell lung cancer (NSCLC) patients. The expression of never in mitosis gene A (NIMA)-related kinase 2 (NEK2), minichromosome maintenance complex component 7 (Mcm7) and Ki67 was evaluated in 270 NSCLC tissues using immunohistochemical and immunofluorescence techniques. Associations between protein expression and clinicopathological characters were assessed, and the impact on overall survival was analyzed. High levels of NEK2, Mcm7 and Ki67 expression were detected in 25.9, 35.2 and 24.4% of the NSCLC tissues. Overexpression of NEK2 was detected more frequently in cases with high T and N stages (P<0.0001 and P=0.011, respectively). Correlations were present between the expression of NEK2, Mcm7 and Ki67. Kaplan-Meier curves indicated that the patients with overexpressed NEK2, Mcm7 and Ki67 had a poorer overall survival time compared to those with low expression for all stages (P<0.0001). In particular, the patients with NEK2 overexpression had a poorer prognosis. Multivariate Cox regression analysis showed that NEK2, Mcm7 and Ki67 are independent prognostic indicators for NSCLC. In conclusion, the data indicate that compared with Mcm7 and Ki67, NEK2 may be a more effective tumor proliferation marker of poor prognosis for NSCLC patients, and that NEK2 may represent a novel potential target for NSCLC therapeutic intervention.

Association of Aurora A and gamma-tubulin expression in astrocytomas and patient survival

OBJECTIVES

The purpose was to evaluate the association of Aurora A and gamma-tubulin expression with disease characteristics and survival in patients with astrocytoma.

METHODS

This is a retrospective study of patients who had surgical specimens that were pathologically diagnosed as astrocytoma. The expression level of Aurora A and gamma-tubulin in tumor tissue was evaluated by immunohistochemistry. Clinical information, Karnofsky performance status scale, and survival status of patients were collected.

RESULTS

We found that high protein levels of gamma-tubulin or Aurora A were associated with patients 45 years of age, high tumor grade, more advanced non-fully resectable tumors, and poorer survival status. The survival time for patients whose tumors had high gamma-tubulin and Aurora A expression was about 12 months compared with approximately 41 months for patients with low levels of expression of these proteins. Poor patient performance status following resection was also associated with high levels of gamma-tubulin and Aurora A expression.

DISCUSSION

The expression levels of gamma-tubulin or Aurora A kinase were associated with patients' age, astrocytoma grade, respectability, as well as patient survival and performance. These findings support the idea that these factors may potentially be important prognostic indicators for patients with astrocytomas.

Microtubule-Associated Protein Tau, α-Tubulin and βIII-Tubulin Expression in Breast Cancer

Background

The microtubule-associated protein Tau binds to both inner and outer surfaces of microtubules, leading to tubulin assembly and microtubule stabilization. The aim of this study was to evaluate the significance of Tau, α-tubulin, and βIII-tubulin expression in breast carcinoma and to assess their relationships with disease progression in the context of taxane treatment.

Methods

Immunohistochemical expressions of Tau, α-tubulin, and βIII-tubulin were assessed in 183 breast cancer cases. Expression was correlated with clinicopathologic parameters, disease progression and overall survival.

Results

Tau expression was correlated with lymph node metastasis and estrogen receptor (ER) positivity (p=.003 and p<.001, respectively). Loss of α-tubulin was significantly correlated with distant metastasis (p=.034). Loss of βIII-tubulin was correlated with lymph node metastasis and ER positivity (p=.004 and p<.001, respectively). In taxane-treated cases, Tau expression and loss of α-tubulin and βIII-tubulin expression were related to disease progression (p=.001, p=.028, and p=.030, respectively). Tau expression was associated with a worse survival rate in taxane-treated patients (p=.049).

Conclusions

Tau expression and loss of α-tubulin and βIII-tubulin expression were correlated with aggressive behavior in taxane-treated breast cancer. Further evaluation of Tau, α-tubulin and βIII-tubulin may be useful in predicting clinical behavior and seeking therapeutic measures in taxane-based chemotherapy for breast cancer.

Nek2A contributes to tumorigenic growth and possibly functions as potential therapeutic target for human breast cancer

Nek2A (NIMA-related kinases 2A) has been known as an important centrosome regulatory factor. The aim of this study was to investigate the expression of Nek2A and the role it played in different stages of breast cancer. We detected the expression of Nek2A in both mRNA and protein levels in MCF10 cell lines including MCF-10A, MCF-10DCIS.com, MCF-10CA1a and in human breast samples which contained normal breast tissue (NBT), breast ductal carcinoma in situ (DCIS), and invasive ductal carcinoma (IDC). Our study revealed that the mRNA and protein expression of Nek2A were significantly up-regulated in MCF-10DCIS.com and MCF-10CA1a cell lines as well as in human primary breast cancer tissue (DCIS and IDC). Our study also presented a correlation between Nek2A mRNA expression and some clinic pathological factors. We found that Nek2A mRNA expression was associated with molecular subtypes, ER, PR and Ki-67 immunoreactivity (P<0.05) in DCIS and associated with histological grade, lymph node metastasis, molecular subtypes, c-erbB-2, and Ki-67 expression (P<0.05) in IDC. In addition, we observed that ectopic expression of Nek2A in "normal" immortalized MCF-10A breast epithelial cell resulted in increased Nek2A which lead to abnormal centrosomes. Furthermore, knockdown of Nek2A in MCF-10DCIS.com could remarkably inhibit cell proliferation and induce cell cycle arrest in MCF-10DCIS.com cell line. These data suggested that Nek2A might bear a close relationship with development and progression of breast carcinoma, and highlighted its role as a novel potential biomarker for diagnosis and a possible therapeutic target for human breast cancer especially for DCIS.

Abnormal expression of Nek2 and β-catenin in breast carcinoma: clinicopathological correlations

AIMS

NIMA-related kinase 2 (Nek2) and β-catenin are important centrosome regulatory factors. The aim of this study was to detect the possible disparity in their expression among normal breast tissue, invasive ductal carcinoma (IDC), concomitant ductal carcinoma in situ (DCIS), and pure DCIS, and to explore its correlation with clinicopathological factors.

METHODS AND RESULTS

We used immunohistochemistry to detect protein expression of Nek2 and β-catenin in breast cancer tissues from 60 cases of pure DCIS, 348 cases of IDC and 137 cases of concomitant DCIS with that in normal breast tissues from the same 137 concomitant DCIS patients as controls. As compared with normal tissue, expression of Nek2 and β-catenin in the cytoplasm was significantly increased in IDC and DCIS (P < 0.05), and variation in expression was also observed in different grades of IDC (P < 0.01). Also, cytoplasmic expression of Nek2 and and of β-catenin were correlated with each other in IDC and DCIS (P < 0.01). In addition, they were both related to Ki67 immunoreactivity (P < 0.05). Furthermore, our study also revealed a correlation between their expression and some clinicopathological factors. We found that Nek2 cytoplasmic expression was associated with grade and tumour size (P < 0.01) in IDC, whereas β-catenin cytomembrane expression showed significant variation with grades, TNM stages, lymphoid node status, oestrogen receptor status, and molecular subtype (P < 0.05); a difference in expression was also observed between IDC and DCIS (P < 0.05). Also, β-catenin cytoplasmic expression was associated with TNM stage (P < 0.05). Expression of Nek2 at the mRNA level was detected in 50 pairs of breast cancer specimens and matched normal tissues by reverse transcriptase polymerase chain reaction, and the result showed increased expression in IDC.

CONCLUSIONS

This study suggests that abnormal expression of Nek2 and β-catenin might be one of the mechanisms of tumorigenesis, especially of abnormal tumour proliferation. They may represent new potential targets for therapeutic intervention.

Discovery of small molecule inhibitors that interact with γ-tubulin

Recent studies have shown an overexpression of γ-tubulin in human glioblastomas and glioblastoma cell lines. As the 2-year survival rate for glioblastoma is very poor, potential benefit exists for discovering novel chemotherapeutic agents that can inhibit γ-tubulin, which is known to form a ring complex that acts as a microtubule nucleation center. We present experimental evidence that colchicine and combretastatin A-4 bind to γ-tubulin, which are to our knowledge the first drug-like compounds known to interact with γ-tubulin. Molecular dynamics simulations and docking studies were used to analyze the hypothesized γ-tubulin binding domain of these compounds. The suitability of the potential binding modes was evaluated and suggests the subsequent rational design of novel targeted inhibitors of γ-tubulin.

Nuclear γ-tubulin associates with nucleoli and interacts with tumor suppressor protein C53

γ-Tubulin is assumed to be a typical cytosolic protein necessary for nucleation of microtubules from microtubule organizing centers. Using immunolocalization and cell fractionation techniques in combination with siRNAi and expression of FLAG-tagged constructs, we have obtained evidence that γ-tubulin is also present in nucleoli of mammalian interphase cells of diverse cellular origins. Immunoelectron microscopy has revealed γ-tubulin localization outside fibrillar centers where transcription of ribosomal DNA takes place. γ-Tubulin was associated with nucleolar remnants after nuclear envelope breakdown and could be translocated to nucleoli during mitosis. Pretreatment of cells with leptomycin B did not affect the distribution of nuclear γ-tubulin, making it unlikely that rapid active transport via nuclear pores participates in the transport of γ-tubulin into the nucleus. This finding was confirmed by heterokaryon assay and time-lapse imaging of photoconvertible protein Dendra2 tagged to γ-tubulin. Immunoprecipitation from nuclear extracts combined with mass spectrometry revealed an association of γ-tubulin with tumor suppressor protein C53 located at multiple subcellular compartments including nucleoli. The notion of an interaction between γ-tubulin and C53 was corroborated by pull-down and co-immunoprecipitation experiments. Overexpression of γ-tubulin antagonized the inhibitory effect of C53 on DNA damage G(2) /M checkpoint activation. The combined results indicate that aside from its known role in microtubule nucleation, γ-tubulin may also have nuclear-specific function(s).

A clinical overview of centrosome amplification in human cancers

The turn of the 21st century had witnessed a surge of interest in the centrosome and its causal relation to human cancer development - a postulate that has existed for almost a century. Centrosome amplification (CA) is frequently detected in a growing list of human cancers, both solid and haematological, and is a candidate "hallmark" of cancer cells. Several lines of evidence support the progressive involvement of CA in the transition from early to advanced stages of carcinogenesis, being also found in pre-neoplastic lesions and even in histopathologically-normal tissue. CA constitutes the major mechanism leading to chromosomal instability and aneuploidy, via the formation of multipolar spindles and chromosomal missegregation. Clinically, CA may translate to a greater risk for initiation of malignant transformation, tumour progression, chemoresistance and ultimately, poor patient prognosis. As mechanisms underlying CA are progressively being unravelled, the centrosome has emerged as a novel candidate target for cancer treatment. This Review summarizes mainly the clinical studies performed to date focusing on the mechanisms underlying CA in human neoplasia, and highlights the potential utility of centrosomes in the diagnosis, prognosis and treatment of human cancers.

Chromosome aberrations associated with centrosome defects: a study of comparative genomic hybridization in breast cancer

Centrosome abnormalities occur frequently in various tumors and can cause chromosomal instability and eventually promote cancer development. We investigated the chromosome aberrations associated with centrosome abnormalities in 30 cases of breast cancer, combining immunohistochemical staining and comparative genomic hybridization. Except for some common chromosome alterations (including gains of 1q, 8q, 17q, 20q, and Xq and losses of 8p, 11q, 13q, 14q, 16q, 17p, 22q, and Xp) that have also been seen more frequently in other studies, we discovered some new changes that have rarely been reported, including gains at 2p, 5p, 10p, 15q, 16p, 18q, 21q, and 22q and losses at 6p, 8p23, 11p13-pter, 13q34, and 14q32-qter. We also identified some changes (such as gains of 17q, 20q, and Xq and losses of 17p, 13q, and 14q) harboring candidate genes. We also explored the expression of centrosome protein in different molecular subtypes of breast cancer. Our findings provide a new way to explore the molecular mechanisms of breast tumorigenesis and accordingly potential new targets for therapy for this disease.

Differential expression and cellular distribution of gamma-tubulin and betaIII-tubulin in medulloblastomas and human medulloblastoma cell lines

In previous studies, we have shown overexpression and ectopic subcellular distribution of gamma-tubulin and betaIII-tubulin in human glioblastomas and glioblastoma cell lines (Katsetos et al., 2006, J Neuropathol Exp Neurol 65:455-467; Katsetos et al., 2007, Neurochem Res 32:1387-1398). Here we determined the expression of gamma-tubulin in surgically excised medulloblastomas (n = 20) and in the human medulloblastoma cell lines D283 Med and DAOY. In clinical tissue samples, the immunohistochemical distribution of gamma-tubulin labeling was pervasive and inversely related to neuritogenesis. Overexpression of gamma-tubulin was widespread in poorly differentiated, proliferating tumor cells but was significantly diminished in quiescent differentiating tumor cells undergoing neuritogenesis, highlighted by betaIII-tubulin immunolabeling. By quantitative real-time PCR, gamma-tubulin transcripts for TUBG1, TUBG2, and TUBB3 genes were detected in both cell lines but expression was less prominent when compared with the human glioblastoma cell lines. Immunoblotting revealed comparable amounts of gamma-tubulin and betaIII-tubulin in different phases of cell cycle; however, a larger amount of gamma-tubulin was detected in D283 Med when compared with DAOY cells. Interphase D283 Med cells exhibited predominantly diffuse cytoplasmic gamma-tubulin localization, in addition to the expected centrosome-associated distribution. Robust betaIII-tubulin immunoreactivity was detected in mitotic spindles of DAOY cells. Our data indicate that overexpression of gamma-tubulin may be linked to phenotypic dedifferentiation (anaplasia) and tumor progression in medulloblastomas and may potentially serve as a promising tumor marker.