Stepwise progression of centrosome defects associated with local tumor growth and metastatic process of human pancreatic carcinoma cells transplanted orthotopically into nude mice

Centrosome amplification is a frequent event in circulating tumor cells from subjects with metastatic breast cancer

Centrosome amplification (CA) is a common phenomenon in cancer, promotes genomic stability and cancer evolution, and has been reported to promote metastasis. CA promotes a stochastic gain/loss of chromosomes during cell division, known as chromosomal instability (CIN). However, it is unclear whether CA is present in circulating tumor cells (CTCs), the seeds for metastasis. Here, we surveyed CA in CTCs from human subjects with metastatic breast cancer. CTCs were captured by CD45 exclusion and selection of EpCAM‐positive cells using an exclusion‐based sample preparation technology platform known as VERSA (versatile exclusion‐based rare sample analysis). Centriole amplification (centrin foci> 4) is the definitive assay for CA. However, determination of centrin foci is technically challenging and incompatible with automated analysis. To test if the more technically accessible centrosome marker pericentrin could serve as a surrogate for centriole amplification in CTCs, cells were stained with pericentrin and centrin antibodies to evaluate CA. This assay was first validated using breast cancer cell lines and a nontransformed epithelial cell line model of inducible CA, then translated to CTCs. Pericentrin area and pericentrin area x intensity correlate well with centrin foci, validating pericentrin as a surrogate marker of CA. CA is found in CTCs from 75% of subjects, with variability in the percentage and extent of CA in individual circulating cells in a given subject, similar to the variability previously seen in primary tumors and cell lines. In summary, we created, validated, and implemented a novel method to assess CA in CTCs from subjects with metastatic breast cancer. Such an assay will be useful for longitudinal monitoring of CA in cancer patients and in prospective clinical trials for assessing the impact of CA on response to therapy.

FF-10502, an Antimetabolite with Novel Activity on Dormant Cells, Is Superior to Gemcitabine for Targeting Pancreatic Cancer Cells

In this paper, we report that 1-(2-deoxy-2-fluoro-4-thio-β-d-arabinofuranosyl) cytosine (FF-10502), a pyrimidine nucleoside antimetabolite with a chemical structure similar to gemcitabine, shows beneficial anticancer activity via a novel mechanism of action on dormant cells. The growth inhibition of pancreatic cancer cell lines by FF-10502 (IC₅₀, 60-330 nM) was moderately weaker than that by gemcitabine in vitro. In contrast, an in vivo orthotopic implantation model in mice with established human pancreatic cancer cell line, SUIT-2, revealed no mortality with FF-10502 intravenous treatment, which was related to regression of implanted tumor and little metastasis, whereas 75% of the mice treated with gemcitabine died by day 128. Two in vivo patient-derived xenograft models with gemcitabine-resistant pancreatic cancer cells also demonstrated complete tumor growth suppression with FF-10502, but only partial inhibition with gemcitabine. We also investigated the mechanism of action of FF-10502 by using dormant cancer cells, which are reportedly involved in the development of resistance to chemotherapy. In vitro serum starvation-induced dormant SUIT-2 cells developed resistance to gemcitabine even in combination with DNA damage inducers (DDIs; H₂O₂, cisplatin, and temozolomide). Interestingly, FF-10502 in combination with DDIs significantly induced concentration-dependent cell death in accordance with enhanced DNA damage. FF-10502 was far more potent than gemcitabine in inhibiting DNA polymerase β, which may explain the difference in dormant cell injury, although further investigations for direct evidences are necessary. In conclusion, our study demonstrated the beneficial antitumor effects of FF-10502 in clinically relevant in vivo models, and suggests the importance of preventing DNA repair unlike gemcitabine.

Centrosome amplification, chromosomal instability and cancer: mechanistic, clinical and therapeutic issues

Centrosomes, the main microtubule-organizing centers in most animal cells, are of crucial importance for the assembly of a bipolar mitotic spindle and subsequent faithful segregation of chromosomes into two daughter cells. Centrosome abnormalities can be found in virtually all cancer types and have been linked to chromosomal instability (CIN) and tumorigenesis. Although our knowledge on centrosome structure, replication, and amplification has greatly increased within recent years, still only very little is known on nature, causes, and consequences of centrosome aberrations in primary tumor tissues. In this review, we summarize our current insights into the mechanistic link between centrosome aberrations, aneuploidy, CIN and tumorigenesis. Mechanisms of induction and cellular consequences of aneuploidy, tetraploidization and CIN, as well as origin and effects of supernumerary centrosomes will be discussed. In addition, animal models for both CIN and centrosome amplification will be outlined. Finally, we describe approaches to exploit centrosome amplification, aneuploidy and CIN for novel and specific anticancer treatment strategies based on the modulation of chromosome missegregation rates.

Hypoxia-inducible factor-targeting prodrug TOP3 combined with gemcitabine or TS-1 improves pancreatic cancer survival in an orthotopic model

Pancreatic cancer is one of the most lethal digestive system cancers with a 5‐year survival rate of 4–7%. Despite extensive efforts, recent chemotherapeutic regimens have provided only limited benefits to pancreatic cancer patients. Gemcitabine and TS‐1, the current standard‐of‐care chemotherapeutic drugs for treatment of this severe cancer, have a low response rate. Hypoxia is one of the factors contributing to treatment resistance. Specifically, overexpression of hypoxia‐inducible factor, a master transcriptional regulator of cell adaption to hypoxia, is strongly correlated with poor prognosis in many human cancers. TAT‐ODD‐procaspase‐3 (TOP3) is a protein prodrug that is specifically processed and activated in hypoxia‐inducible factor‐active cells in cancers, leading to cell death. Here, we report combination therapies in which TOP3 was combined with gemcitabine or TS‐1. As monotherapy, gemcitabine and TS‐1 showed a limited effect on hypoxic and starved pancreatic cancer cells, whereas co‐treatment with TOP3 successfully overcame this limitation in vitro. Furthermore, combination therapies of TOP3 with these drugs resulted in a significant improvement in survival of orthotopic pancreatic cancer models involving the human pancreatic cancer cell line SUIT‐2. Overall, our study indicates that the combination of TOP3 with current chemotherapeutic drugs can significantly improve treatment outcome, offering a promising new therapeutic option for patients with pancreatic cancer.

Amplified centrosomes may underlie aggressive disease course in pancreatic ductal adenocarcinoma

Centrosome amplification (CA), the presence of centrosomes that are abnormally numerous or enlarged, is a well-established driver of tumor initiation and progression associated with poor prognosis across a diversity of malignancies. Pancreatic ductal adenocarcinoma (PDAC) carries one of the most dismal prognoses of all cancer types. A majority of these tumors are characterized by numerical and structural centrosomal aberrations, but it is unknown how CA contributes to the disease and patient outcomes. In this study, we sought to determine whether CA was associated with worse clinical outcomes, poor prognostic indicators, markers of epithelial-mesenchymal transition (EMT), and ethnicity in PDAC. We also evaluated whether CA could precipitate more aggressive phenotypes in a panel of cultured PDAC cell lines. Using publicly available microarray data, we found that increased expression of genes whose dysregulation promotes CA was associated with worse overall survival and increased EMT marker expression in PDAC. Quantitative analysis of centrosomal profiles in PDAC cell lines and tissue sections uncovered varying levels of CA, and the expression of CA markers was associated with the expression of EMT markers. We induced CA in PDAC cells and found that CA empowered them with enhanced invasive and migratory capabilities. In addition, we discovered that PDACs from African American (AA) patients exhibited a greater extent of both numerical and structural CA than PDACs from European American (EA) patients. Taken together, these findings suggest that CA may fuel a more aggressive disease course in PDAC patients.

Centrosome amplification and clonal evolution in multiple myeloma: Short review

Multiple myeloma (MM) is composed of an array of multiple clones, each potentially associated with different clinical behavior. Previous studies focused on clinical implication of centrosome amplification (CA) in MM show contradictory results. It seems that the role of CA as well as CA formation in MM differ from other malignancies. This has brought about a question about the role of CA positive clone which is--is it going to be a more aggressive clone evolutionally arising under pressure of negative conditions or can CA serve as a marker of cell abnormality and lead to cell death and further elimination of this damaged subpopulation? This current review is devoted to the discussion of the existence of MM subclones with centrosome amplification (CA), its evolutionary behaviour within intraclonal heterogeneity as well as its potential impact on the disease progression and MM treatment.

USP33 regulates centrosome biogenesis via deubiquitination of the centriolar protein CP110

Centrosome duplication is critical for cell division, and genome instability can result if duplication is not restricted to a single round per cell cycle. Centrosome duplication is controlled in part by CP110, a centriolar protein that positively regulates centriole duplication while restricting centriole elongation and ciliogenesis. Maintenance of normal CP110 levels is essential, as excessive CP110 drives centrosome over-duplication and suppresses ciliogenesis, whereas its depletion inhibits centriole amplification and leads to highly elongated centrioles and aberrant assembly of cilia in growing cells. CP110 levels are tightly controlled, partly through ubiquitination by the ubiquitin ligase complex SCF(cyclin F) during G2 and M phases of the cell cycle. Here, using human cells, we report a new mechanism for the regulation of centrosome duplication that requires USP33, a deubiquitinating enzyme that is able to regulate CP110 levels. USP33 interacts with CP110 and localizes to centrioles primarily in S and G2/M phases, the periods during which centrioles duplicate and elongate. USP33 potently and specifically deubiquitinates CP110, but not other cyclin-F substrates. USP33 activity antagonizes SCF(cyclin F)-mediated ubiquitination and promotes the generation of supernumerary centriolar foci, whereas ablation of USP33 destabilizes CP110 and thereby inhibits centrosome amplification and mitotic defects. To our knowledge, we have identified the first centriolar deubiquitinating enzyme whose expression regulates centrosome homeostasis by countering cyclin-F-mediated destruction of a key substrate. Our results point towards potential therapeutic strategies for inhibiting tumorigenesis associated with centrosome amplification.

Clinical implication of centrosome amplification and expression of centrosomal functional genes in multiple myeloma

Background

Multiple myeloma (MM) is a low proliferative tumor of postgerminal center plasma cell (PC). Centrosome amplification (CA) is supposed to be one of the mechanisms leading to chromosomal instability. Also, CA is associated with deregulation of cell cycle, mitosis, DNA repair and proliferation. The aim of our study was to evaluate the prognostic significance and possible role of CA in pathogenesis and analysis of mitotic genes as mitotic disruption markers.

Design and methods

A total of 173 patients were evaluated for this study. CD138+ cells were separated by MACS. Immunofluorescent labeling of centrin was used for evaluation of centrosome amplification in PCs. Interphase FISH with cytoplasmic immunoglobulin light chain staining (cIg FISH) and qRT-PCR were performed on PCs.

Results

Based on the immunofluorescent staining results, all patients were divided into two groups: CA positive (38.2%) and CA negative (61.8%). Among the newly diagnosed patients, worse overall survival was indicated in the CA negative group (44/74) in comparison to the CA positive group (30/74) (P = 0.019).

Gene expression was significantly down-regulated in the CA positive group in comparison to CA negative in the following genes: AURKB, PLK4, TUBG1 (P < 0.05). Gene expression was significantly down-regulated in newly diagnosed in comparison to relapsed patients in the following genes: AURKA, AURKB, CCNB1, CCNB2, CETN2, HMMR, PLK4, PCNT, and TACC3 (P < 0.05).

Conclusions

Our findings indicate better prognosis for CA positive newly diagnosed patients. Considering revealed clinical and gene expression heterogeneity between CA negative and CA positive patients, there is a possibility to characterize centrosome amplification as a notable event in multiple myeloma pathogenesis.

Losses at chromosome 4q are associated with poor survival in operable ductal pancreatic adenocarcinoma

Here we tested the prognostic impact of genomic alterations in operable localized pancreatic ductal adenocarcinoma (PDAC). Fifty-two formalin-fixed and paraffin-embedded primary PDAC were laser micro-dissected and were investigated by comparative genomic hybridization after whole genome amplification using an adapter-linker PCR. Chromosomal gains and losses were correlated to clinico-pathological parameters and clinical follow-up data. The most frequent aberration was loss on chromosome 17p (65%) while the most frequent gains were detected at 2q (41%) and 8q (41%), respectively. The concomitant occurrence of losses at 9p and 17p was found to be statistically significant. Higher rates of chromosomal losses were associated with a more advanced primary tumor stage and losses at 9p and 18q were significantly associated with presence of lymphatic metastasis (chi-square: p = 0.03, p = 0.05, respectively). Deletions on chromosome 4 were of prognostic significance for overall survival and tumor recurrence (Cox-multivariate analysis: p = 0.026 and p = 0.021, respectively). In conclusion our data suggest the common alterations at chromosome 8q, 9p, 17p and 18q as well as the prognostic relevant deletions on chromosome 4q as relevant for PDAC progression. Our comprehensive data from 52 PDAC should provide a basis for future studies with a higher resolution to discover the relevant genes located within the chromosomal aberrations identified.

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.

Analysis of the cellular centrosome in fine-needle aspirations of the breast

Background

The purpose of the present investigation is to determine whether centrosome amplifications are present in breast tumor cells, whether there are differences of centrosome amplification between benign breast lesions and breast carcinomas, and whether centrosomal analysis can be of value in the diagnosis and prognosis of breast carcinoma.

Methods

Using immunofluorescence analysis with an antibody against γ-tubulin, we analyzed centrosome abnormalities in fine-needle aspirations of 100 breast lesions (25 cases with benign lesions and 75 cases with carcinomas).

Results

We found that centrosome amplifications, including numerical centrosome amplification and structural centrosome amplification, were present in most breast tumors. Cells with numerical centrosome amplification were found in 23 of 25 benign lesions, and in all 75 cases of breast carcinomas. Cells with structural centrosome amplification were found in three of 25 benign lesions, and in 69 of 75 breast carcinomas. The breast carcinomas showed a mean percentage of cells with numerical centrosome amplification of 4.86% and a mean percentage of cells with structural centrosome amplification of 3.98%. These percentages were significantly higher than those in benign lesions, with a numerical centrosome amplification of 2.77% and a structural centrosome amplification of 0.10%. Furthermore, the mean percentage of cells with structural centrosome amplification was significantly associated with HER2/neu overexpression (P < 0.05) and with negative estrogen receptor status (P < 0.05), and had a borderline association with negative progesterone receptor status (P = 0.056) in breast carcinomas.

Conclusion

Structural centrosome amplification may bear a close relationship with breast carcinoma and may be a potential biomarker for diagnosis and prognosis of breast carcinoma.

Chromosomal instability and supernumerary centrosomes represent precursor defects in a mouse model of T-cell lymphoma

A hallmark of carcinogenesis is resistance to cell death. However, recent studies indicate that Bax expression increased apoptosis and promoted oncogenesis. In this study, we hypothesized that Bax promotes tumor formation by increasing chromosomal instability (CIN). Consistent with this hypothesis, spectral karyotype analysis (SKY) of lymphomas derived from Lck-Bax38/1 mice were consistently aneuploid. To determine if CIN precedes tumor formation, quantitative cytogenetic analysis, SKY analysis, and quantitative centrosome staining were done on thymocytes from young premalignant mice. Between 6 and 10 weeks of age, thymi from Bax-expressing mice (either p53+/+ or p53-/-) had an increased percentage of aneuploid cells as well as an increase in cells with supernumerary centrosomes. For 3- to 6-week-old mice, Bax expression increased aneuploidy and supernumerary centrosomes in p53-/- mice but not in p53+/+ animals. Importantly, both aneuploidy and supernumerary centrosomes were attenuated by Bcl-2. Remarkably, SKY analysis showed multiple independent aneuploid populations in the p53-/- Bax-expressing mice between 3 and 6 weeks of age. These results indicate that oligoclonal aneuploidy and supernumerary centrosomes are early hallmarks of Bax-induced lymphoma formation and support a novel link between the Bcl-2 family and CIN. The data provide an attractive model for the paradoxical effects of the Bcl-2 family on carcinogenesis that have been observed in multiple studies of both humans and mice.

Establishment and characterization of a high metastatic potential in the peritoneum for human gastric cancer by orthotopic tumor cell implantation

The aim of this study was to establish an orthotopic implantation model with high metastasis of gastric cancer to the peritoneum which is more faithful to clinical metastasis. A human gastric carcinoma cell line, GC9811, was injected as a single-cell suspension into the stomach of nude mice. The cells from some peritoneum metastatic foci were expanded in vitro and subsequently implanted to the stomach wall of nude mice. By repeating the in vivo stepwise selection method for four rounds and cloning culture, we obtained a cell line designated GC9811-P, which developed peritoneal metastasis in 13 of 13 (100%) of mice, compared with only 20% of those implanted with parental GC9811. The metastatic foci in the peritoneum showed essentially the same histological appearance as those induced by parental cells. Tumor cell growth of GC9811-P in vitro was faster than that of GC9811. Motility assays demonstrated higher motility of GC9811-P than of GC9811. The adhesive ability of GC9811-P cells to laminin was lower than that of GC9811 cells, whereas the ability of GC9811-P cells to adhere to fibronectin was significantly higher than that of parental cells. Differences between GC9811-P and their parental GC9811 cells were found in expression levels of various molecules by flow cytometric and western blot. The findings indicated that up-regulation in the expressions of CD155, VEGF, syndecan-1, and syndecan-2 or down-regulation in the expressions of IL-6 and E-cadherin play an important role in the peritoneal metastasis of human gastric carcinoma cells. The high-metastatic cell line appears to be useful for investigating the mechanisms of peritoneal metastasis and preventing peritoneal metastasis of human gastric cancer.

Centrosomal proteins Nde1 and Su48 form a complex regulated by phosphorylation

The centrosome modulates spindle formation and plays a critical role in guiding proper segregation of chromosomes during cell division. Centrosome aberrations, frequently seen in human tumors, may cause abnormal chromosome segregation and contribute to malignant transformation. To explore the components of the centrosomes, we previously identified a novel centrosomal protein called Su48. To further characterize the Su48-containing protein ensemble in the centrosome, we performed yeast two-hybrid screens and isolated a number of Su48-interacting molecules, including the centrosomal protein Nde1. Here, we demonstrate that Su48 can associate with Nde1. Moreover, we found that Nde1 is subjected to phosphorylation in vivo. In particular, we identified six putative Cdc2 phosphorylation sites in Nde1 and found that alteration of these sites diminishes phosphorylation by Cdc2 in vitro and affects the stability of Su48-Nde1 interactions and the centrosomal localization of Nde1. Ablation of Nde1 by gene specific small interfering RNA causes mitotic delay and cell death, coupled with a modest decrease in the incidence of the cells that harbor excessive centrosomes. Collectively, our findings indicate that Nde1 can form a protein complex with Su48 in the centrosome and plays an important role for successful mitosis.

p78/MCRS1 forms a complex with centrosomal protein Nde1 and is essential for cell viability

The centrosome, an organelle that functions as the major microtubule-organizing center, plays an essential role in the formation of the mitotic spindle and guiding accurate chromosome segregation. Centrosome aberrations are frequently associated with various forms of human cancers and it is thought that defects in this organelle contribute to genomic instability and malignant transformation. We recently identified and characterized a centrosome-localized protein complex that is comprised of Su48 and Nde1. Disruption of the normal function of these proteins leads to abnormal cell division. To extend our understanding of how this protein complex operates, we sought to identify Nde1-interacting molecules by the yeast two-hybrid screening method. Here, we demonstrate that both Nde1 and Su48 can associate with p78/MCRS1, a protein implicated in cancer development. We found that, whereas the majority of p78 localizes to the nucleus as reported in earlier studies, a fraction of the p78 protein can be detected in the centrosome. Moreover, we determined that a region containing the forkhead-associated domain of p78 is involved in association with Nde1 and Su48, as well as in centrosomal localization. We also provide evidence that the association between p78 and Nde1 is regulated by phosphorylation on Nde1. Furthermore, abrogation of the endogenous p78 function by small interfering RNA knockdown causes cell death and a modest delay in mitosis. These results indicate that a subset of the p78 proteins comprises a component of the centrosome and that p78 is essential for cell viability.

AURKA amplification, chromosome instability, and centrosome abnormality in human pancreatic carcinoma cells

To test the hypothesis that AURKA amplification contributes to pancreatic tumorigenesis by increasing centrosome abnormality and chromosome instability, the current study explored the associations between AURKA amplification, chromosome instability, centrosome abnormality, and the expression of several important proteins that are involved in cell proliferation (Ki-67), cell cycle regulation (p53, p16), and apoptosis (survivin) in 12 human pancreatic carcinoma cell lines. Using fluorescence in situ hybridization (FISH), we observed that 5 of the 12 cell lines had an AURKA amplification index (AI) (percentage of cells with more than three signals) >60%. Both the AURKA AI and the average number of signals per cell (ANSPC) were significantly associated with the copy number of chromosome 9 but not chromosome 17. The AURKA ANSPC was positively associated with the percentage of cells with the centrosome abnormality. Furthermore, centrosome abnormality was significantly associated with the frequency of cells with abnormal nuclei and abnormal mitotic figures, but no direct association was detected between the frequency of centrosome abnormalities and chromosome instabilities. The AURKA AI was also associated with a lower expression of Ki-67, a higher expression of survivin, and the lack of expression of p16. These associations support our hypothesis that AURKA amplification contributes to pancreatic carcinogenesis by increasing chromosome instability and centrosome abnormality.

Centrosomal amplification and spindle multipolarity in cancer cells

Recent developments have highlighted the important role centrosomal defects play in the cellular changes associated with tumorigenesis. This article reviews recent developments addressing the impact of numerical centrosomal amplification on chromosomal segregational defects in the cancer cell. Probably, the most significant is the change to the structure of the spindle that leads to increased numbers of spindle poles and abnormal partitioning of the chromosomes in mitosis. I address how centrosomal changes are initiated and how they may lead to spindle multipolarity.

Centrosome aberrations as a possible mechanism for chromosomal instability in non-Hodgkin's lymphoma

Recently, centrosome aberrations have been described as a possible cause of aneuploidy in many solid tumors. To investigate whether centrosome aberrations occur in non-Hodgkin's lymphoma (NHL) and correlate with histologic subtype, karyotype, and other biological disease features, we examined 24 follicular lymphomas (FL), 18 diffuse large-B-cell lymphomas (DLCL), 33 mantle cell lymphomas (MCL), and 17 extranodal marginal zone B-cell lymphomas (MZBCL), using antibodies to centrosomal proteins. All 92 NHL displayed numerical and structural centrosome aberrations as compared to nonmalignant lymphoid tissue. Centrosome abnormalities were detectable in 32.3% of the cells in NHL, but in only 5.5% of lymphoid cells from 30 control individuals (P<0.0001). Indolent FL and MZBCL contained only 25.8 and 28.8% cells with abnormal centrosomes. In contrast, aggressive DLCL and MCL harbored centrosome aberrations in 41.8 and 35.0% of the cells, respectively (P<0.0001). Centrosomal aberrations correlated to lymphoma grade, mitotic, and proliferation indices, but not to the p53 labeling index. Importantly, diploid MCL contained 31.2% cells with abnormal centrosomes, while tetraploid samples harbored centrosome aberrations in 55.6% of the cells (P<0.0001). These results indicate that centrosome defects are common in NHL and suggest that they may contribute to the acquisition of chromosomal instability typically seen in NHL.

The good, the bad and the ugly: the practical consequences of centrosome amplification

Centrosome amplification (the presence of more than two centrosomes at mitosis) is characteristic of many human cancers. Extra centrosomes can cause the assembly of multipolar spindles, which unequally distribute chromosomes to daughter cells; the resulting genetic imbalances may contribute to cellular transformation. However, this raises the question of how a population of cells with centrosome amplification can survive such chaotic mitoses without soon becoming non-viable as a result of chromosome loss. Recent observations indicate that a variety of mechanisms partially mute the practical consequences of centrosome amplification. Consequently, populations of cells propagate with good efficiency, despite centrosome amplification, yet have an elevated mitotic error rate that can fuel the evolution of the transformed state.

Centrosomal aberrations in primary invasive breast cancer are associated with nodal status and hormone receptor expression

Our purpose was to assess the presence of centrosomal aberrations as measured by immunohistochemistry in primary invasive breast cancer and their association with established and proposed prognostic factors. Tissue sections of 103 primary invasive breast cancers were examined using centrosome-specific antibodies to pericentrin and gamma-tubulin. At least 3 different tumor regions per case were examined to determine maximum centrosomal aberration levels, which represent the proportion of cells with abnormal centrosomes in the region with the highest percentage of cells with centrosomal aberrations. The chi(2) test was performed to evaluate the association of maximum centrosomal aberration levels with patient age; tumor size; nodal status; nuclear grade; hormone receptor and Her2/neu expression; proportion of Ki67-, p53- and Bcl-2-positive tumor cells; DNA index; S-phase fraction; and proliferation index. With pericentrin immunohistochemistry, maximum centrosomal aberration levels >35% were detectable in 92 of the 103 breast carcinomas (89%). We found a highly significant correlation of maximum centrosomal aberration levels above 35% with axillary nodal tumor involvement (p < 0.0001) and the absence of hormone receptors (p < 0.0001). In addition, there was a borderline significant relationship with age <50 years (p = 0.050) and Her2/neu overexpression (p = 0.050). Among node-negative patients, maximum centrosomal aberration levels >35% were also associated with an increased DNA index (p = 0.006). In a subset of patients, additional staining of centrosomes with a monoclonal anti-gamma-tubulin antibody essentially confirmed these results. In primary invasive breast cancer, centrosomal aberrations are associated with those factors predicting a more aggressive course of disease. This might indicate a fundamental role of centrosomal dysfunction in disease evolution, possibly as a result of chromosome missegregation during mitosis.

Centrosomal abnormality is common in and a potential biomarker for bladder cancer

Centrosomal abnormalities have been implicated in chromosomal segregation aberrations that result from the formation of multipolar mitotic spindles and lead to aneuploidy. Aneuploidy is a characteristic of neoplasia and underlies the development and progression of bladder cancer. Therefore, centrosomal abnormality may play a key role in urothelial tumor transformation. The purpose of our investigation was to determine whether centrosomal abnormalities are present in malignant urothelial cells, define the relationship between centrosomal abnormalities and aneuploidy and determine whether the presence of centrosomal abnormalities might be a potential diagnostic marker for bladder cancer. Bladder wash specimens obtained from patients with and without a history of urothelial carcinoma were analyzed for centrosomal abnormalities using an immunoassay with a gamma-tubulin antibody. FISH with centromeric probes for chromosomes 4 and 9 and DNA ploidy image analysis were performed to detect aneuploidy. Defective centrosomes were found in 40 of 45 bladder wash specimens from patients with bladder cancer but in none of the 10 samples from patients without it. A large percentage (69%) of grade 1 tumors were positive for centrosomal abnormalities, and these abnormalities were increasing in numbers and size in grade 2 (93%) and grade 3 (100%) specimens. Centrosomal abnormalities and numerical chromosomal aberrations frequently appeared concomitantly in the same malignant cells. All of the specimens showing aneuploidy also exhibited centrosomal abnormalities: centrosomal defects and aneuploidy occurred together in 80% of malignant bladder tumors, with an especially high percentage in higher-grade tumors. The overall positivity of centrosomal abnormalities was higher than that of aneuploidy (88% vs. 80%), especially in grade 1 tumors (69% vs. 46%), whereas aneuploidy was strongly associated with grade 2 and grade 3 tumors. Centrosomal abnormalities are common in bladder cancer, even in low-grade tumors, and strongly associated with cancer grade and aneuploidy, especially in high-grade neoplasms. Centrosomal abnormalities appear to be intrinsic to aneuploidy and tumorigenesis and may be potential markers for early detection of bladder cancer.

Centrosomal abnormalities, multipolar mitoses, and chromosomal instability in head and neck tumours with dysfunctional telomeres

Carcinomas of the head and neck typically exhibit complex chromosome aberrations but the underlying mutational mechanisms remain obscure. Evaluation of cell division dynamics in low-passage cell lines from three benign and five malignant head and neck tumours revealed a strong positive correlation between multipolarity of the mitotic spindle and the formation of bridges at anaphase in both benign and malignant tumours. Cells exhibiting a high rate of mitotic abnormalities also showed several chromosome termini lacking TTAGGG repeats and a high frequency of dicentric chromosomes. Multicolour karyotyping demonstrated a preferential involvement in structural rearrangements of chromosomes with deficient telomeres. The majority of malignant, mitotically unstable tumours expressed the reverse transcriptase subunit of telomerase. These data indicate that some of the genomic instability in head and neck tumours is initiated by telomere dysfunction, leading to the formation of dicentric chromosomes. These form chromosome bridges at mitosis that could prevent the normal anaphase-telophase transition. In turn, this may cause an accumulation of centrosomes and mitotic multipolarity. Telomerase expression does not confer total stability to the tumour genome but could be crucial for moderating the rate of chromosomal evolution.

Centrosome replication, genomic instability and cancer

Karyotypic alterations, including whole chromosome loss or gain, ploidy changes, and a variety of chromosome aberrations are common in cancer cells. If proliferating cells fail to coordinate centrosome duplication with DNA replication, this will inevitably lead to a change in ploidy, and the formation of monopolar or multipolar spindles will generally provoke abnormal segregation of chromosomes. Indeed, it has long been recognized that errors in the centrosome duplication cycle may be an important cause of aneuploidy and thus contribute to cancer formation. This view has recently received fresh impetus with the description of supernumerary centrosomes in almost all solid human tumors. As the primary microtubule organizing center of most eukaryotic cells, the centrosome assures symmetry and bipolarity of the cell division process, a function that is essential for accurate chromosome segregation. In addition, a growing body of evidence indicates that centrosomes might be important for initiating S phase and completing cytokinesis. Centrosomes undergo duplication precisely once before cell division. Recent reports have revealed that this process is linked to the cell division cycle via cyclin-dependent kinase (cdk) 2 activity that couples centriole duplication to the onset of DNA replication at the G(1)/S phase transition. Alterations in G(1)/S phase regulating proteins like the retinoblastoma protein, cyclins D and E, cdk4 and 6, cdk inhibitors p16(INK4A) and p15(INK4B), and p53 are among the most frequent aberrations observed in human malignancies. These alterations might not only lead to unrestrained proliferation, but also cause karyotypic instability by uncontrolled centrosome replication. Since several excellent reports on cell cycle regulation and cancer have been published, this review will focus on the role of centrosomes in cell cycle progression, as well as causes and consequences of aberrant centrosome replication in human neoplasias.

Aurora-A overexpression reveals tetraploidization as a major route to centrosome amplification in p53-/- cells

Aberrations in centrosome numbers have long been implicated in aneuploidy and tumorigenesis, but their origins are unknown. Here we have examined how overexpression of Aurora-A kinase causes centrosome amplification in cultured cells. We show that excess Aurora-A does not deregulate centrosome duplication but gives rise to extra centrosomes through defects in cell division and consequent tetraploidization. Over expression of other mitotic kinases (Polo-like kinase 1 and Aurora-B) also causes multinucleation and concomitant increases in centrosome numbers. Absence of a p53 checkpoint exacerbates this phenotype, providing a plausible explanation for the centrosome amplification typical of p53-/- cells. We propose that errors during cell division, combined with the inability to detect the resulting hyperploidy, constitute a major cause for numerical centrosome aberrations in tumors.