A catalog of numerical centrosome defects in epithelial ovarian cancers.

Centrosome amplification, the presence of more than two centrosomes in a cell is a common feature of most human cancer cell lines. However, little is known about centrosome numbers in human cancers and whether amplification or other numerical aberrations are frequently present. To address this question, we have analyzed a large cohort of primary human epithelial ovarian cancers (EOCs) from 100 patients. We found that rigorous quantitation of centrosome number in tumor samples was extremely challenging due to tumor heterogeneity and extensive tissue disorganization. Interestingly, even if centrosome clusters could be identified, the incidence of centrosome amplification was not comparable to what has been described in cultured cancer cells. Surprisingly, centrosome loss events where a few or many nuclei were not associated with centrosomes were clearly noticed and overall more frequent than centrosome amplification. Our findings highlight the difficulty of characterizing centrosome numbers in human tumors, while revealing a novel paradigm of centrosome number defects in EOCs.

Genetic instability from a single S phase after whole-genome duplication.

Diploid and stable karyotypes are associated with health and fitness in animals. By contrast, whole-genome duplications-doublings of the entire complement of chromosomes-are linked to genetic instability and frequently found in human cancers1-3. It has been established that whole-genome duplications fuel chromosome instability through abnormal mitosis4-8; however, the immediate consequences of tetraploidy in the first interphase are not known. This is a key question because single whole-genome duplication events such as cytokinesis failure can promote tumorigenesis9. Here we find that human cells undergo high rates of DNA damage during DNA replication in the first S phase following induction of tetraploidy. Using DNA combing and single-cell sequencing, we show that DNA replication dynamics is perturbed, generating under- and over-replicated regions. Mechanistically, we find that these defects result from a shortage of proteins during the G1/S transition, which impairs the fidelity of DNA replication. This work shows that within a single interphase, unscheduled tetraploid cells can acquire highly abnormal karyotypes. These findings provide an explanation for the genetic instability landscape that favours tumorigenesis after tetraploidization.

Centrosomes in disease: how the same music can sound so different?

Centrosomes are the major microtubule organizing center of animal cells. Centrosomes contribute to timely bipolar spindle assembly during mitosis and participate in the regulation of other processes such as polarity establishment and cell migration. Centrosome numbers are tightly controlled during the cell cycle to ensure that mitosis is initiated with only two centrosomes. Deviations in centrosome number or structure are known to impact cell or tissue homeostasis and can impact different processes as diverse as proliferation, death or disease. Interestingly, defects in centrosome number seem to culminate with common responses, which depend on p53 activation even in different contexts such as development or cancer. p53 is a tumor suppressor gene with essential roles in the maintenance of genetic stability normally stimulated by various cellular stresses. Here, we review current knowledge and discuss how defects in centrosome structure and number can lead to different human pathologies.

ShallowHRD: detection of homologous recombination deficiency from shallow whole genome sequencing.

SUMMARY: We introduce shallowHRD, a software tool to evaluate tumor homologous recombination deficiency (HRD) based on whole genome sequencing (WGS) at low coverage (shallow WGS or sWGS; ∼1X coverage). The tool, based on mining copy number alterations profile, implements a fast and straightforward procedure that shows 87.5% sensitivity and 90.5% specificity for HRD detection. shallowHRD could be instrumental in predicting response to poly(ADP-ribose) polymerase inhibitors, to which HRD tumors are selectively sensitive. shallowHRD displays efficiency comparable to most state-of-art approaches, is cost-effective, generates low-storable outputs and is also suitable for fixed-formalin paraffin embedded tissues. AVAILABILITY AND IMPLEMENTATION: shallowHRD R script and documentation are available at https://github.com/aeeckhou/shallowHRD. SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online.

Chromosomes function as a barrier to mitotic spindle bipolarity in polyploid cells.

Ploidy variations such as genome doubling are frequent in human tumors and have been associated with genetic instability favoring tumor progression. How polyploid cells deal with increased centrosome numbers and DNA content remains unknown. Using Drosophila neuroblasts and human cancer cells to study mitotic spindle assembly in polyploid cells, we found that most polyploid cells divide in a multipolar manner. We show that even if an initial centrosome clustering step can occur at mitotic entry, the establishment of kinetochore-microtubule attachments leads to spatial chromosome configurations, whereby the final coalescence of supernumerary poles into a bipolar array is inhibited. Using in silico approaches and various spindle and DNA perturbations, we show that chromosomes act as a physical barrier blocking spindle pole coalescence and bipolarity. Importantly, microtubule stabilization suppressed multipolarity by improving both centrosome clustering and pole coalescence. This work identifies inhibitors of bipolar division in polyploid cells and provides a rationale to understand chromosome instability typical of polyploid cancer cells.

PML-Regulated Mitochondrial Metabolism Enhances Chemosensitivity in Human Ovarian Cancers.

High-grade serous ovarian cancer (HGSOC) remains an unmet medical challenge. Here, we unravel an unanticipated metabolic heterogeneity in HGSOC. By combining proteomic, metabolomic, and bioergenetic analyses, we identify two molecular subgroups, low- and high-OXPHOS. While low-OXPHOS exhibit a glycolytic metabolism, high-OXPHOS HGSOCs rely on oxidative phosphorylation, supported by glutamine and fatty acid oxidation, and show chronic oxidative stress. We identify an important role for the PML-PGC-1α axis in the metabolic features of high-OXPHOS HGSOC. In high-OXPHOS tumors, chronic oxidative stress promotes aggregation of PML-nuclear bodies, resulting in activation of the transcriptional co-activator PGC-1α. Active PGC-1α increases synthesis of electron transport chain complexes, thereby promoting mitochondrial respiration. Importantly, high-OXPHOS HGSOCs exhibit increased response to conventional chemotherapies, in which increased oxidative stress, PML, and potentially ferroptosis play key functions. Collectively, our data establish a stress-mediated PML-PGC-1α-dependent mechanism that promotes OXPHOS metabolism and chemosensitivity in ovarian cancer.

Ovarian Cancers Harboring Inactivating Mutations in CDK12 Display a Distinct Genomic Instability Pattern Characterized by Large Tandem Duplications.

CDK12 is a recurrently mutated gene in serous ovarian carcinoma, whose downregulation is associated with impaired expression of DNA damage repair genes and subsequent hypersensitivity to DNA-damaging agents and PARP1/2 inhibitors. In this study, we investigated the genomic landscape associated with CDK12 inactivation in patients with serous ovarian carcinoma. We show that CDK12 loss was consistently associated with a particular genomic instability pattern characterized by hundreds of tandem duplications of up to 10 megabases (Mb) in size. Tandem duplications were characterized by a bimodal (∼0.3 and ∼3 Mb) size distribution and overlapping microhomology at the breakpoints. This genomic instability, denoted as the CDK12 TD-plus phenotype, is remarkably distinct from other alteration patterns described in breast and ovarian cancers. The CDK12 TD-plus phenotype was associated with a greater than 10% gain in genomic content and occurred at a 3% to 4% rate in The Cancer Genome Atlas-derived and in-house cohorts of patients with serous ovarian carcinoma. Moreover, CDK12-inactivating mutations together with the TD-plus phenotype were also observed in prostate cancers. Our finding provides new insight toward deciphering the function of CDK12 in genome maintenance and oncogenesis. Cancer Res; 76(7); 1882-91. ©2016 AACR.

Histo-genomic stratification reveals the frequent amplification/overexpression of CCNE1 and BRD4 genes in non-BRCAness high grade ovarian carcinoma.

The treatment of epithelial ovarian cancer (EOC) is narrowly focused despite the heterogeneity of this disease in which outcomes remain poor. To stratify EOC patients for targeted therapy, we developed an approach integrating expression and genomic analyses including the BRCAness status. Gene expression and genomic profiling were used to identify genes recurrently (>5%) amplified and overexpressed in 105 EOC. The LST (Large-scale State Transition) genomic signature of BRCAness was applied to define molecular subgroups of EOC. Amplified/overexpressed genes clustered mainly in 3q, 8q, 19p and 19q. These changes were generally found mutually exclusive. In the 85 patients for which the genomic signature could be determined, genomic BRCAness was found in 52 cases (61.1%) and non-BRCAness in 33 (38.8%). A striking mutual exclusivity was observed between BRCAness and amplification/overexpression data. Whereas 3q and 8q alterations were preferentially observed in BRCAness EOC, most alterations on chromosome 19 were in non-BRCAness cases. CCNE1 (19q12) and BRD4 (19p13.1) amplification/overexpression was found in 19/33 (57.5%) of non-BRCAness cases. Such disequilibrium was also found in the TCGA EOC data set used for validation. Potential target genes are frequently amplified/overexpressed in non-BRCAness EOC. We report that BRD4, already identified as a target in several tumor models, is a new potential target in high grade non-BRCAness ovarian carcinoma.

Akt and RhoA inhibition promotes anoikis of aggregated B16F10 melanoma cells.

In the highly metastatic B16F10 melanoma cell line, activation of the signalling molecules that promote cell proliferation and survival on conventional adhesive culture dishes may also be responsible for the growth and resistance to anoikis of aggregates on a non-adhesive substratum. We have examined the influence of bacterial ADP-ribosyltransferases C3-like exoenzymes, which selectively modify RhoA, B and C proteins and inhibit signal pathways controlled by them. RNA interference [siRNA (small interfering RNA) Akt (also known as protein kinase B)] and a PI3K (phosphoinositide 3-kinase) inhibitor were used to analyse the changes caused by inhibiting the PI3K/Akt pathway. Inhibiting the activation of RhoA, B, C and Akt expression resulted in a decrease of the number of cells cultured in aggregates, and caspase 3 activation. RhoA activation and RhoB and RhoC expression were controlled by Akt, but not RhoA expression. Inhibiting Akt and RhoA reduced the expression of α5 integrin, and inactivated FAK (focal adhesion kinase) in B16F10 cells cultured as aggregates. Thus, inhibiting Rho subfamily proteins and Akt expression inactivates the FAK pathway and induces anoikis in anoikis-resistant cells. The activation of RhoA in melanoma cells can depend on PI3K/Akt activation, suggesting that PI3K/Akt is a suitable target for new therapeutic approaches.

Growth and survival signalling in B16F10 melanoma cells in 3D culture.

The two-way communication between the ECM (extracellular matrix) and the cytoplasm via the integrins has many functions in cancer cells, including the suppression of apoptosis. As cells in a 3D (three-dimensional) architecture resemble the in vivo situation more closely than do cells in more conventional 2D cultures, we have employed a substratum that prevents cell adhesion and induces cell aggregation to determine why highly metastatic B16F10 melanoma cells resist anoikis. We compared the behaviour of B16F10 cells in 2D [on tPS (tissue culture polystyrene)] and 3D culture {on polyHEMA [poly(2-hydroxyethylmethacrylate)]} configurations. For this, we analysed cell morphology, proliferation, apoptosis and the activation status of several proteins involved in cell proliferation and survival [RhoA, FAK (focal adhesion kinase), Akt, ERK1/2 (extracellular-signal-regulated kinase 1/2)]. B16F10 cells in 3D architecture were able to proliferate as cell aggregates for 3 days, after which the number of cells decreased. The normal Swiss 3T3 cells used as an anoikis-sensitive control did not proliferate on the anti-adhesive substratum. Rho A was activated in B16F10 aggregates throughout their time in culture, whereas it was not in Swiss 3T3 aggregates. An absence of apoptotic activity was correlated with the proliferation of B16F10 cells in aggregates: caspase 3 was significantly activated only after 3 days in culture on polyHEMA. FAK and Akt were transiently activated, and their inactivation was correlated with the induction of apoptosis. ERK1/2 were activated throughout the 3D culture. No survival protein was activated in Swiss 3T3 aggregates. Data obtained from cells in 3D culture suggest that B16F10 cells are resistant to anoikis through the activation of the FAK and Akt signalling pathways.

Antiproliferative and proapoptotic actions of okra pectin on B16F10 melanoma cells.

The proliferation and apoptosis of metastatic melanoma cells are often abnormal. We have evaluated the action of a pectic rhamnogalacturonan obtained by hot buffer extraction of okra pods (okra RG-I) on melanoma cell growth and survival in vitro. We added okra RG-I containing an almost pure RG-I carrying very short galactan side chains to 2D (on tissue culture polystyrene, tPS) and 3D (on poly(2-hydroxyethylmethacrylate), polyHEMA) cultures of highly metastatic B16F10 mouse melanoma cells. We then analyzed cell morphology, proliferation index, apoptosis, cell cycle progression and the expression of adhesion molecules. Immunostaining and western blotting were used to assay galectin-3 (Gal-3) protein.Incubation with okra RG-I altered the morphology of B16F10 cells and significantly reduced their proliferation on both tPS and polyHEMA. The cell cycle was arrested in G2/M, and apoptosis was induced, particularly in cells on polyHEMA. The expression of N-cadherin and alpha5 integrin subunit was reduced and that of the multifunctional carbohydrate-binding protein, Gal-3, at the cell membrane increased.These findings suggest that okra RG-I induces apoptosis in melanoma cells by interacting with Gal-3. As these interactions might open the way to new melanoma therapies, the next step will be to determine just how they occur.