SUMMARY Centrosome amplification is a common feature of human tumors, but whether this is a cause or a consequence of cancer remains unclear. Here, we test the consequence of centrosome amplification by creating mice in which centrosome number can be chronically increased in the absence of additional genetic defects. We show that increasing centrosome number elevated tumor initiation in a mouse model of intestinal neoplasia. Most importantly, we demonstrate that supernumerary centrosomes are sufficient to drive aneuploidy and the development of spontaneous tumors in multiple tissues. Tumors arising from centrosome amplification exhibit frequent mitotic errors and possess complex karyotypes, recapitulating a common feature of human cancer. Together, our data support a direct causal relationship between centrosome amplification, genomic instability and tumor development.

BackgroundChromosome instability leads to aneuploidy, a state in which cells have abnormal numbers of chromosomes, and is found in two out of three cancers. In a chromosomal instable p53 deficient mouse model with accelerated lymphomagenesis, we previously observed whole chromosome copy number changes affecting all lymphoma cells. This suggests that chromosome instability is somehow suppressed in the aneuploid lymphomas or that selection for frequently lost/gained chromosomes out-competes the CIN-imposed mis-segregation.ResultsTo distinguish between these explanations and to examine karyotype dynamics in chromosome instable lymphoma, we use a newly developed single-cell whole genome sequencing (scWGS) platform that provides a complete and unbiased overview of copy number variations (CNV) in individual cells. To analyse these scWGS data, we develop AneuFinder, which allows annotation of copy number changes in a fully automated fashion and quantification of CNV heterogeneity between cells. Single-cell sequencing and AneuFinder analysis reveals high levels of copy number heterogeneity in chromosome instability-driven murine T-cell lymphoma samples, indicating ongoing chromosome instability. Application of this technology to human B cell leukaemias reveals different levels of karyotype heterogeneity in these cancers.ConclusionOur data show that even though aneuploid tumours select for particular and recurring chromosome combinations, single-cell analysis using AneuFinder reveals copy number heterogeneity. This suggests ongoing chromosome instability that other platforms fail to detect. As chromosome instability might drive tumour evolution, karyotype analysis using single-cell sequencing technology could become an essential tool for cancer treatment stratification.Electronic supplementary materialThe online version of this article (doi:10.1186/s13059-016-0971-7) contains supplementary material, which is available to authorized users.

U. (2021).Aneuploidy renders cancer cells vulnerable to mitotic checkpoint inhibition. Nature, 590(7846).

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Cancer relies upon frequent or abnormal cell division but how the tumor microenvironment affects mitotic processes in vivo remains unclear, largely due to the technical challenges of optical access, spatial resolution, and motion. We developed high-resolution in vivo microscopy methods to visualize mitosis in a murine xenograft model of human cancer. Using these methods, we determined whether the single-cell response to the anti-mitotic drug paclitaxel was the same in tumors as in cell culture; observed the impact of paclitaxel (Ptx) on the tumor response as a whole; and evaluated the single-cell pharmacodynamics of paclitaxel (by in vivo pharmacodynamic microscopy [IPDM]). Mitotic initiation was generally less frequent in tumors than in cell culture, but subsequently it proceeded normally. Paclitaxel treatment caused spindle assembly defects and mitotic arrest, followed by slippage from mitotic arrest, multinucleation and apoptosis. Compared to cell culture, the peak mitotic index in tumors exposed to paclitaxel was lower and the tumor cells survived longer after mitotic arrest, becoming multinucleated rather than dying directly from mitotic arrest. Thus, the tumor microenvironment was much less pro-apoptotic than cell culture. The morphologies associated with mitotic arrest were dose- and time-dependent, thereby providing a semi-quantitative, single-cell measure of pharmacodynamics. Although many tumor cells did not progress through Ptx-induced mitotic arrest, tumor significantly regressed in the model. Our findings demonstrate that in vivo microscopy offers a useful tool to visualize mitosis during tumor progression, drug responses, and cell fate at the single cell level.

The presence of an abnormal karyotype has been shown to be profoundly detrimental at the cellular and organismal levels but is an overt hallmark of cancer. Aneuploidy can lead to p53 activation and thereby prevents proliferation, but the exact trigger for p53 activation has remained controversial. Here, we have used a system to induce aneuploidy in untransformed human cells to explore how cells deal with different segregation errors. We show that p53 is activated only in a subset of the cells with altered chromosome content. Importantly, we find that at least a subset of whole-chromosome aneuploidies can be propagated in p53-proficient cells, indicating that aneuploidy does not always lead to activation of p53. Finally, we demonstrate that propagation of structural aneuploidies (gain or loss of part of a chromosome) induced by segregation errors is limited to p53-deficient cells.

BackgroundAlzheimer’s disease (AD) is a neurodegenerative disease of the brain and the most common form of dementia in the elderly. Aneuploidy, a state in which cells have an abnormal number of chromosomes, has been proposed to play a role in neurodegeneration in AD patients. Several studies using fluorescence in situ hybridization have shown that the brains of AD patients contain an increased number of aneuploid cells. However, because the reported rate of aneuploidy in neurons ranges widely, a more sensitive method is needed to establish a possible role of aneuploidy in AD pathology.ResultsIn the current study, we used a novel single-cell whole genome sequencing (scWGS) approach to assess aneuploidy in isolated neurons from the frontal cortex of normal control individuals (n = 6) and patients with AD (n = 10). The sensitivity and specificity of our method was shown by the presence of three copies of chromosome 21 in all analyzed neuronal nuclei of a Down’s syndrome sample (n = 36). Very low levels of aneuploidy were found in the brains from control individuals (n = 589) and AD patients (n = 893). In contrast to other studies, we observe no selective gain of chromosomes 17 or 21 in neurons of AD patients.ConclusionscWGS showed no evidence for common aneuploidy in normal and AD neurons. Therefore, our results do not support an important role for aneuploidy in neuronal cells in the pathogenesis of AD. This will need to be confirmed by future studies in larger cohorts.Electronic supplementary materialThe online version of this article (doi:10.1186/s13059-016-0976-2) contains supplementary material, which is available to authorized users.

SummaryInhibitors of poly(ADP-ribose) polymerase (PARP) have demonstrated efficacy in women with BRCA-mutant ovarian cancer. However, only 15%–20% of ovarian cancers harbor BRCA mutations, therefore additional therapies are required. Here, we show that a subset of ovarian cancer cell lines and ex vivo models derived from patient biopsies are sensitive to a poly(ADP-ribose) glycohydrolase (PARG) inhibitor. Sensitivity is due to underlying DNA replication vulnerabilities that cause persistent fork stalling and replication catastrophe. PARG inhibition is synthetic lethal with inhibition of DNA replication factors, allowing additional models to be sensitized by CHK1 inhibitors. Because PARG and PARP inhibitor sensitivity are mutually exclusive, our observations demonstrate that PARG inhibitors have therapeutic potential to complement PARP inhibitor strategies in the treatment of ovarian cancer.