Chromosome missegregation rate predicts whether aneuploidy will promote or suppress tumors

Chromosomal instability increases radiation sensitivity

Continuous chromosome missegregation over successive mitotic divisions, known as chromosomal instability (CIN), is common in cancer. Increasing CIN above a maximally tolerated threshold leads to cell death due to loss of essential chromosomes. Here, we show in two tissue contexts that otherwise isogenic cancer cells with higher levels of CIN are more sensitive to ionizing radiation, which itself induces CIN. CIN also sensitizes HPV-positive and HPV-negative head and neck cancer patient derived xenograft (PDX) tumors to radiation. Moreover, laryngeal cancers with higher CIN prior to treatment show improved response to radiation therapy. In addition, we reveal a novel mechanism of radiosensitization by docetaxel, a microtubule stabilizing drug commonly used in combination with radiation. Docetaxel causes cell death by inducing CIN due to abnormal multipolar spindles rather than causing mitotic arrest, as previously assumed. Docetaxel-induced CIN, rather than mitotic arrest, is responsible for the enhanced radiation sensitivity observed in vitro and in vivo, challenging the mechanistic dogma of the last 40 years. These results implicate CIN as a potential biomarker and inducer of radiation response, which could provide valuable cancer therapeutic opportunities.

Statement of Significance

Cancer cells and laryngeal tumors with higher chromosome missegregation rates are more sensitive to radiation therapy, supporting chromosomal instability as a promising biomarker of radiation response.

Kinesin-7 CENP-E mediates centrosome organization and spindle assembly to regulate chromosome alignment and genome stability

Chromosome congression and alignment are essential for cell cycle progression and genomic stability. Kinesin-7 CENP-E, a plus-end-directed kinesin motor, is required for chromosome biorientation, congression and alignment in cell division. However, it remains unclear how chromosomes are aligned and segregated in the absence of CENP-E in mitosis. In this study, we utilize the CRISPR-Cas9 gene editing method and high-throughput screening to establish CENP-E knockout cell lines and reveal that CENP-E deletion results in defects in chromosome congression, alignment and segregation, which further promotes aneuploidy and genomic instability in mitosis. Both CENP-E inhibition and deletion lead to the dispersion of spindle poles, the formation of the multipolar spindle and spindle disorganization, which indicates that CENP-E is necessary for the organization and maintenance of spindle poles. In addition, CENP-E heterozygous deletion in spleen tissues also leads to the accumulation of dividing lymphocytes and cell cycle arrest in vivo. Furthermore, CENP-E deletion also disrupts the localization of key kinetochore proteins and triggers the activation of the spindle assembly checkpoint. In summary, our findings demonstrate that CENP-E promotes kinetochore-microtubule attachment and spindle pole organization to regulate chromosome alignment and spindle assembly checkpoint during cell division.

Patterns of Aneuploidy and Signaling Consequences in Cancer

Aneuploidy, or a change in the number of whole chromosomes or chromosome arms, is a near-universal feature of cancer. Chromosomes affected by aneuploidy are not random, with observed cancer-specific and tissue-specific patterns. Recent advances in genome engineering methods have allowed the creation of models with targeted aneuploidy events. These models can be used to uncover the downstream effects of individual aneuploidies on cancer phenotypes including proliferation, apoptosis, metabolism, and immune signaling. Here, we review the current state of research into the patterns of aneuploidy in cancer and their impact on signaling pathways and biological processes.

Molecular evolution of the mammalian kinetochore complex

Mammalian centromeres are satellite-rich chromatin domains that serve as sites for kinetochore complex assembly. Centromeres are highly variable in sequence and satellite organization across species, but the processes that govern the co-evolutionary dynamics between rapidly evolving centromeres and their associated kinetochore proteins remain poorly understood. Here, we pursue a course of phylogenetic analyses to investigate the molecular evolution of the complete kinetochore complex across primate and rodent species with divergent centromere repeat sequences and features. We show that many protein components of the core centromere associated network (CCAN) harbor signals of adaptive evolution, consistent with their intimate association with centromere satellite DNA and roles in the stability and recruitment of additional kinetochore proteins. Surprisingly, CCAN and outer kinetochore proteins exhibit comparable rates of adaptive divergence, suggesting that changes in centromere DNA can ripple across the kinetochore to drive adaptive protein evolution within distant domains of the complex. Our work further identifies kinetochore proteins subject to lineage-specific adaptive evolution, including rapidly evolving proteins in species with centromere satellites characterized by higher-order repeat structure and lacking CENP-B boxes. Thus, features of centromeric chromatin beyond the linear DNA sequence may drive selection on kinetochore proteins. Overall, our work spotlights adaptively evolving proteins with diverse centromere-associated functions, including centromere chromatin structure, kinetochore protein assembly, kinetochore-microtubule association, cohesion maintenance, and DNA damage response pathways. These adaptively evolving kinetochore protein candidates present compelling opportunities for future functional investigations exploring how their concerted changes with centromere DNA ensure the maintenance of genome stability.

The yin and yang of chromosomal instability in prostate cancer

Metastatic prostate cancer remains an incurable lethal disease. Studies indicate that prostate cancer accumulates genomic changes during disease progression and displays the highest levels of chromosomal instability (CIN) across all types of metastatic tumours. CIN, which refers to ongoing chromosomal DNA gain or loss during mitosis, and derived aneuploidy, are known to be associated with increased tumour heterogeneity, metastasis and therapy resistance in many tumour types. Paradoxically, high CIN levels are also proposed to be detrimental to tumour cell survival, suggesting that cancer cells must develop adaptive mechanisms to ensure their survival. In the context of prostate cancer, studies indicate that CIN has a key role in disease progression and might also offer a therapeutic vulnerability that can be pharmacologically targeted. Thus, a comprehensive evaluation of the causes and consequences of CIN in prostate cancer, its contribution to aggressive advanced disease and a better understanding of the acquired CIN tolerance mechanisms can translate into new tumour classifications, biomarker development and therapeutic strategies.

A survey of chromosomal instability measures across mechanistic models

Chromosomal instability (CIN) is the persistent reshuffling of cancer karyotypes via chromosome mis-segregation during cell division. In cancer, CIN exists at varying levels that have differential effects on tumor progression. However, mis-segregation rates remain challenging to assess in human cancer despite an array of available measures. We evaluated measures of CIN by comparing quantitative methods using specific, inducible phenotypic CIN models of chromosome bridges, pseudobipolar spindles, multipolar spindles, and polar chromosomes. For each, we measured CIN fixed and timelapse fluorescence microscopy, chromosome spreads, six-centromere FISH, bulk transcriptomics, and single-cell DNA sequencing (scDNAseq). As expected, microscopy of tumor cells in live and fixed samples significantly correlated (R = 0.72; P < 0.001) and sensitively detect CIN. Cytogenetics approaches include chromosome spreads and 6-centromere FISH, which also significantly correlate (R = 0.76; P < 0.001) but had limited sensitivity for lower rates of CIN. Bulk genomic DNA signatures and bulk transcriptomic scores, CIN70 and HET70, did not detect CIN. By contrast, scDNAseq detects CIN with high sensitivity, and significantly correlates with imaging methods (R = 0.82; P < 0.001). In summary, single-cell methods such as imaging, cytogenetics, and scDNAseq can measure CIN, with the latter being the most comprehensive method accessible to clinical samples. To facilitate the comparison of CIN rates between phenotypes and methods, we propose a standardized unit of CIN: Mis-segregations per Diploid Division. This systematic analysis of common CIN measures highlights the superiority of single-cell methods and provides guidance for measuring CIN in the clinical setting.

Kinesin-7 CENP-E in tumorigenesis: Chromosome instability, spindle assembly checkpoint, and applications

Kinesin motors are a large family of molecular motors that walk along microtubules to fulfill many roles in intracellular transport, microtubule organization, and chromosome alignment. Kinesin-7 CENP-E (Centromere protein E) is a chromosome scaffold-associated protein that is located in the corona layer of centromeres, which participates in kinetochore-microtubule attachment, chromosome alignment, and spindle assembly checkpoint. Over the past 3 decades, CENP-E has attracted great interest as a promising new mitotic target for cancer therapy and drug development. In this review, we describe expression patterns of CENP-E in multiple tumors and highlight the functions of CENP-E in cancer cell proliferation. We summarize recent advances in structural domains, roles, and functions of CENP-E in cell division. Notably, we describe the dual functions of CENP-E in inhibiting and promoting tumorigenesis. We summarize the mechanisms by which CENP-E affects tumorigenesis through chromosome instability and spindle assembly checkpoints. Finally, we overview and summarize the CENP-E-specific inhibitors, mechanisms of drug resistances and their applications.

Theory and application of TTFields in newly diagnosed glioblastoma

BACKGROUND

Glioblastoma is the most common primary malignant brain tumor in adults. TTFields is a therapy that use intermediate-frequency and low-intensity alternating electric fields to treat tumors. For patients with ndGBM, the addition of TTFields after the concurrent chemoradiotherapy phase of the Stupp regimen can improve prognosis. However, TTFields still has the potential to further prolong the survival of ndGBM patients.

AIM

By summarizing the mechanism and application status of TTFields in the treatment of ndGBM, the application prospect of TTFields in ndbm treatment is prospected.

METHODS

We review the recent literature and included 76 articles to summarize the mechanism of TTfields in the treatment of ndGBM. The current clinical application status and potential health benefits of TTFields in the treatment of ndGBM are also discussed.

RESULTS

TTFields can interfere with tumor cell mitosis, lead to tumor cell apoptosis and increased autophagy, hinder DNA damage repair, induce ICD, activate tumor immune microenvironment, reduce cancer cell metastasis and invasion, and increase BBB permeability. TTFields combines with chemoradiotherapy has made progress, its optimal application time is being explored and the problems that need to be considered when retaining the electrode patches for radiotherapy are further discussed. TTFields shows potential in combination with immunotherapy, antimitotic agents, and PARP inhibitors, as well as in patients with subtentorial gliomas.

CONCLUSION

This review summarizes mechanisms of TTFields in the treatment of ndGBM, and describes the current clinical application of TTFields in ndGBM. Through the understanding of its principle and application status, we believe that TTFields still has the potential to further prolong the survival of ndGBM patients. Thus,research is still needed to explore new ways to combine TTFields with other therapies and optimize the use of TTFields to realize its full potential in ndGBM patients.

Targeting chromosomal instability and aneuploidy in cancer

Cancer development and therapy resistance are driven by chromosomal instability (CIN), which causes chromosome gains and losses (i.e., aneuploidy) and structural chromosomal alterations. Technical limitations and knowledge gaps have delayed therapeutic targeting of CIN and aneuploidy in cancers. However, our toolbox for creating and studying aneuploidy in cell models has greatly expanded recently. Moreover, accumulating evidence suggests that seven conventional antimitotic chemotherapeutic drugs achieve clinical response by inducing CIN instead of mitotic arrest, although additional anticancer activities may also contribute in vivo. In this review, we discuss these recent developments. We also highlight new discoveries, which together show that 25 chromosome arm aneuploidies (CAAs) may be targetable by 36 drugs across 14 types of cancer. Collectively, these advances offer many new opportunities to improve cancer treatment.

The reckoning of chromosomal instability: past, present, future

Quantitative measures of CIN are crucial to our understanding of its role in cancer. Technological advances have changed the way CIN is quantified, offering increased accuracy and insight. Here, we review measures of CIN through its rise as a field, discuss considerations for its measurement, and look forward to future quantification of CIN.

X-ray-downregulated nucleophosmin induces abnormal polarization by anchoring to G-actin

Ionizing radiation poses significant risks to astronauts during deep space exploration. This study investigates the impact of radiation on nucleophosmin (NPM), a protein involved in DNA repair, cell cycle regulation, and proliferation. Using X-rays, a common space radiation, we found that radiation suppresses NPM expression. Knockdown of NPM increases DNA damage after irradiation, disrupts cell cycle distribution and enhances cellular radiosensitivity. Additionally, NPM interacts with globular actin (G-actin), affecting its translocation and centrosome binding during mitosis. These findings provide insights into the role of NPM in cellular processes in responding to radiation. This article enhances our comprehension of radiation-induced genomic instability and provides a foundational platform for prospective investigations within the realm of space radiation and its implications for cancer therapy.

Aneuploidy and complex genomic rearrangements in cancer evolution

Mutational processes that alter large genomic regions occur frequently in developing tumors. They range from simple copy number gains and losses to the shattering and reassembly of entire chromosomes. These catastrophic events, such as chromothripsis, chromoplexy and the formation of extrachromosomal DNA, affect the expression of many genes and therefore have a substantial effect on the fitness of the cells in which they arise. In this review, we cover large genomic alterations, the mechanisms that cause them and their effect on tumor development and evolution.

Targeting CENP-E augments immunotherapy in non-small cell lung cancer via stabilizing PD-L1

Centromere-associated protein E (CENP-E) plays a critical role in mitosis and chromosome misalignment, which may represent a potential therapeutic target in tumors. CENP-E is frequently overexpressed in lung cancer and act as a driver gene. However, it remains unclear whether CENP-E regulates the immune microenvironment in non-small cell lung cancer (NSCLC). Our study revealed that CENP-E is highly expressed and predicts a worse survival in NSCLC patients; inhibition of CENP-E leads to an upregulation of PD-L1 expression, consequently impacting the immune microenvironment of NSCLC by modulating the balance between CD8+ T cells and regulatory T cells (Tregs). Mechanistically, we demonstrated that downregulation of CENP-E could stabilize PD-L1 mRNA through the targeting of its 3'UTR by TTP. The genetic knockdown or pharmacological inhibition of CENP-E, in combination with PD-L1 antibody, could enhance the antitumor effect in NSCLC. Thus, our findings have revealed a role of CENP-E in immunotherapy and suggest that combination of CENP-E inhibitor with PD-L1 antibody could be an effective treatment option for NSCLC.

Chronic chromosome instability induced by Plk1 results in immune suppression in breast cancer

Chromosome instability (CIN) contributes to resistance to therapies and tumor evolution. Although natural killer (NK) cells can eliminate cells with complex karyotypes, high-CIN human tumors have an immunosuppressive phenotype. To understand which CIN-associated molecular features alter immune recognition during tumor evolution, we overexpress Polo-like kinase 1 (Plk1) in a Her2+ breast cancer model. These high-CIN tumors activate a senescence-associated secretory phenotype (SASP), upregulate PD-L1 and CD206, and induce non-cell-autonomous nuclear factor κB (NF-κβ) signaling, facilitating immune evasion. Single-cell RNA sequencing from pre-neoplastic mammary glands unveiled the presence of Arg1+ macrophages, NK cells with reduced effector functions, and increased resting regulatory T cell infiltration. We further show that high PLK1-expressing human breast tumors display gene expression patterns associated with SASP, NF-κβ signaling, and immune suppression. These findings underscore the need to understand the immune landscape in CIN tumors to identify more effective therapies, potentially combining immune checkpoint or NF-κβ inhibitors with current treatments.

Transcriptomic correlates of cell cycle checkpoints with distinct prognosis, molecular characteristics, immunological regulation, and therapeutic response in colorectal adenocarcinoma

Backgrounds

Colorectal adenocarcinoma (COAD), accounting for the most common subtype of colorectal cancer (CRC), is a kind of malignant digestive tumor. Some cell cycle checkpoints (CCCs) have been found to contribute to CRC progression, whereas the functional roles of a lot of CCCs, especially the integrated role of checkpoint mechanism in the cell cycle, remain unclear.

Materials and methods

The Genomic Data Commons (GDC) The Cancer Genome Atlas (TCGA) COAD cohort was retrieved as the training dataset, and GSE24551 and GSE29623 were downloaded from Gene Expression Omnibus (GEO) as the validation datasets. A total of 209 CCC-related genes were derived from the Gene Ontology Consortium and were subsequently enrolled in the univariate, multivariate, and least absolute shrinkage and selection operator (LASSO) Cox regression analyses, finally defining a CCC signature. Cell proliferation and Transwell assay analyses were utilized to evaluate the functional roles of signature-related CCCs. The underlying CCC signature, molecular characteristics, immune-related features, and therapeutic response were finally estimated. The Genomics of Drug Sensitivity in Cancer (GDSC) database was employed for the evaluation of chemotherapeutic responses.

Results

The aberrant gene expression of CCCs greatly contributed to COAD development and progression. Univariate Cox regression analysis identified 27 CCC-related genes significantly affecting the overall survival (OS) of COAD patients; subsequently, LASSO analysis determined a novel CCC signature. Noticeably, CDK5RAP2, MAD1L1, NBN, RGCC, and ZNF207 were first identified to be correlated with the prognosis of COAD, and it was proven that all of them were significantly correlated with the proliferation and invasion of HCT116 and SW480 cells. In TCGA COAD cohort, CCC signature robustly stratified COAD patients into high and low CCC score groups (median OS: 57.24 months vs. unreached, p< 0.0001), simultaneously, with the good AUC values for OS prediction at 1, 2, and 3 years were 0.74, 0.78, and 0.77. Furthermore, the prognostic capacity of the CCC signature was verified in the GSE24551 and GSE29623 datasets, and the CCC signature was independent of clinical features. Moreover, a higher CCC score always indicated worse OS, regardless of clinical features, histological subtypes, or molecular subgroups. Intriguingly, functional enrichment analysis confirmed the CCC score was markedly associated with extracellular, matrix and immune (chemokine)-related signaling, cell cycle-related signaling, and metabolisms. Impressively, a higher CCC score was positively correlated with a majority of chemokines, receptors, immunostimulators, and anticancer immunity, indicating a relatively immune-promoting microenvironment. In addition, GSE173839, GSE25066, GSE41998, and GSE194040 dataset analyses of the underlying CCC signature suggested that durvalumab with olaparib and paclitaxel, taxane-anthracycline chemotherapy, neoadjuvant cyclophosphamide/doxorubicin with ixabepilone or paclitaxel, and immunotherapeutic strategies might be suitable for COAD patients with higher CCC score. Eventually, the GDSC database analysis showed that lower CCC scores were likely to be more sensitive to 5-fluorouracil, bosutinib, gemcitabine, gefitinib, methotrexate, mitomycin C, and temozolomide, while patients with higher CCC score seemed to have a higher level of sensitivity to bortezomib and elesclomol.

Conclusion

The novel CCC signature exhibited a good ability for prognosis prediction for COAD patients, and the CCC score was found to be highly correlated with molecular features, immune-related characteristics, and therapeutic responses, which would greatly promote clinical management and precision medicine for COAD.

Targeting mitotic regulators in cancer as a strategy to enhance immune recognition

Eukaryotic DNA has evolved to be enclosed within the nucleus to protect the cellular genome from autoinflammatory responses driven by the immunogenic nature of cytoplasmic DNA. Cyclic GMP-AMP Synthase (cGAS) is the cytoplasmic dsDNA sensor, which upon activation of Stimulator of Interferon Genes (STING), mediates production of pro-inflammatory interferons (IFNs) and interferon stimulated genes (ISGs). However, although this pathway is crucial in detection of viral and microbial genetic material, cytoplasmic DNA is not always of foreign origin. It is now recognised that specifically in genomic instability, a hallmark of cancer, extranuclear material in the form of micronuclei (MN) can be generated as a result of unresolved DNA lesions during mitosis. Activation of cGAS-STING in cancer has been shown to regulate numerous tumour-immune interactions such as acquisition of 'immunologically hot' phenotype which stimulates immune-mediated elimination of transformed cells. Nonetheless, a significant percentage of poorly prognostic cancers is 'immunologically cold'. As this state has been linked with low proportion of tumour-infiltrating lymphocytes (TILs), improving immunogenicity of cold tumours could be clinically relevant by exhibiting synergy with immunotherapy. This review aims to present how inhibition of vital mitotic regulators could provoke cGAS-STING response in cancer and improve the efficacy of current immunotherapy regimens.

RIT1 regulates mitosis and promotes proliferation by interacting with SMC3 and PDS5 in hepatocellular carcinoma

BACKGROUND

As a small G protein of Ras family, Ras-like-without-CAAX-1 (RIT1) plays a critical role in various tumors. Our previous study has demonstrated the involvement of RIT1 in promoting malignant progression of hepatocellular carcinoma (HCC). However, its underlying mechanism remains unclear.

METHODS

Gene set enrichment analysis (GSEA) was conducted in the TCGA LIHC cohort to investigate the underlying biological mechanism of RIT1. Live cell imaging, immunofluorescence (IF) and flow cytometry assays were used to verify biological function of RIT1 in HCC mitosis. Subcutaneous xenografting of human HCC cells in BALB/c nude mice was utilized to assess tumor proliferation in vivo. RNA-seq, co-immunoprecipitation (Co-IP), mass spectrometry analyses, western blot and IF assays were employed to elucidate the mechanisms by which RIT1 regulates mitosis and promotes proliferation in HCC.

RESULTS

Our findings demonstrate that RIT1 plays a crucial role in regulating mitosis in HCC. Knockdown of RIT1 disrupts cell division, leading to G2/M phase arrest, mitotic catastrophe, and apoptosis in HCC cells. SMC3 is found to interact with RIT1 and knockdown of SMC3 attenuates the proliferative effects mediated by RIT1 both in vitro and in vivo. Mechanistically, RIT1 protects and maintains SMC3 acetylation by binding to SMC3 and PDS5 during mitosis, thereby promoting rapid cell division and proliferation in HCC. Notably, we have observed an upregulation of SMC3 expression in HCC tissues, which is associated with poor patient survival and promotion of HCC cell proliferation. Furthermore, there is a significant positive correlation between the expression levels of RIT1, SMC3, and PDS5. Importantly, HCC patients with high expression of both RIT1 and SMC3 exhibit worse prognosis compared to those with high RIT1 but low SMC3 expression.

CONCLUSIONS

Our findings underscore the crucial role of RIT1 in regulating mitosis in HCC and further demonstrate its potential as a promising therapeutic target for HCC treatment.

Contribution of histone variants to aneuploidy: a cancer perspective

Histone variants, which generally differ in few amino acid residues, can replace core histones (H1, H2A, H2B, and H3) to confer specific structural and functional features to regulate cellular functions. In addition to their role in DNA packaging, histones modulate key processes such as gene expression regulation and chromosome segregation, which are frequently dysregulated in cancer cells. During the years, histones variants have gained significant attention as gatekeepers of chromosome stability, raising interest in understanding how structural and functional alterations can contribute to tumourigenesis. Beside the well-established role of the histone H3 variant CENP-A in centromere specification and maintenance, a growing body of literature has described mutations, aberrant expression patterns and post-translational modifications of a variety of histone variants in several cancers, also coining the term "oncohistones." At the molecular level, mechanistic studies have been dissecting the biological mechanisms behind histones and missegregation events, with the potential to uncover novel clinically-relevant targets. In this review, we focus on the current understanding and highlight knowledge gaps of the contribution of histone variants to aneuploidy, and we have compiled a database (HistoPloidyDB) of histone gene alterations linked to aneuploidy in cancers of the The Cancer Genome Atlas project.

Permission to pass: on the role of p53 as a gatekeeper for aneuploidy

Aneuploidy-the karyotype state in which the number of chromosomes deviates from a multiple of the haploid chromosome set-is common in cancer, where it is thought to facilitate tumor initiation and progression. However, it is poorly tolerated in healthy cells: during development and tissue homeostasis, aneuploid cells are efficiently cleared from the population. It is still largely unknown how cancer cells become, and adapt to being, aneuploid. P53, the gatekeeper of the genome, has been proposed to guard against aneuploidy. Aneuploidy in cancer genomes strongly correlates with mutations in TP53, and p53 is thought to prevent the propagation of aneuploid cells. Whether p53 also participates in preventing the mistakes in cell division that lead to aneuploidy is still under debate. In this review, we summarize the current understanding of the role of p53 in protecting cells from aneuploidy, and we explore the consequences of functional p53 loss for the propagation of aneuploidy in cancer.

SIRT1 and HSP90α feed-forward circuit safeguards chromosome segregation integrity in diffuse large B cell lymphomas

Diffuse large B-cell lymphoma (DLBCL) is the most common aggressive non-Hodgkin lymphoma in adults, exhibiting highly heterogenous clinical behavior and complex molecular background. In addition to the genetic complexity, different DLBCL subsets exhibit phenotypic features independent of the genetic background. For example, a subset of DLBCLs is distinguished by increased oxidative phosphorylation and unique transcriptional features, including overexpression of certain mitochondrial genes and a molecular chaperone, heat shock protein HSP90α (termed "OxPhos" DLBCLs). In this study, we identified a feed-forward pathogenetic circuit linking HSP90α and SIRT1 in OxPhos DLBCLs. The expression of the inducible HSP90α isoform remains under SIRT1-mediated regulation. SIRT1 knockdown or chemical inhibition reduced HSP90α expression in a mechanism involving HSF1 transcription factor, whereas HSP90 inhibition reduced SIRT1 protein stability, indicating that HSP90 chaperones SIRT1. SIRT1-HSP90α interaction in DLBCL cells was confirmed by co-immunoprecipitation and proximity ligation assay (PLA). The number of SIRT1-HSP90α complexes in PLA was significantly higher in OxPhos- dependent than -independent cells. Importantly, SIRT1-HSP90α interactions in OxPhos DLBCLs markedly increased in mitosis, suggesting a specific role of the complex during this cell cycle phase. RNAi-mediated and chemical inhibition of SIRT1 and/or HSP90 significantly increased the number of cells with chromosome segregation errors (multipolar spindle formation, anaphase bridges and lagging chromosomes). Finally, chemical SIRT1 inhibitors induced dose-dependent cytotoxicity in OxPhos-dependent DLBCL cell lines and synergized with the HSP90 inhibitor. Taken together, our findings define a new OxPhos-DLBCL-specific pathogenetic loop involving SIRT1 and HSP90α that regulates chromosome dynamics during mitosis and may be exploited therapeutically.

MCAK Inhibitors Induce Aneuploidy in Triple-Negative Breast Cancer Models

Standard of care for triple-negative breast cancer (TNBC) involves the use of microtubule poisons such as paclitaxel, which are proposed to work by inducing lethal levels of aneuploidy in tumor cells. While these drugs are initially effective in treating cancer, dose-limiting peripheral neuropathies are common. Unfortunately, patients often relapse with drug-resistant tumors. Identifying agents against targets that limit aneuploidy may be a valuable approach for therapeutic development. One potential target is the microtubule depolymerizing kinesin, MCAK, which limits aneuploidy by regulating microtubule dynamics during mitosis. Using publicly available datasets, we found that MCAK is upregulated in triple-negative breast cancer and is associated with poorer prognoses. Knockdown of MCAK in tumor-derived cell lines caused a two- to five-fold reduction in the IC50 for paclitaxel, without affecting normal cells. Using FRET and image-based assays, we screened compounds from the ChemBridge 50 k library and discovered three putative MCAK inhibitors. These compounds reproduced the aneuploidy-inducing phenotype of MCAK loss, reduced clonogenic survival of TNBC cells regardless of taxane-resistance, and the most potent of the three, C4, sensitized TNBC cells to paclitaxel. Collectively, our work shows promise that MCAK may serve as both a biomarker of prognosis and as a therapeutic target.

MYO10 regulates genome stability and cancer inflammation through mediating mitosis

Genomic instability can promote inflammation and tumor development. Previous research revealed an unexpected layer of regulation of genomic instability by a cytoplasmic protein MYO10; however, the underlying mechanism remained unclear. Here, we report a protein stability-mediated mitotic regulation of MYO10 in controlling genome stability. We characterized a degron motif and phosphorylation residues in the degron that mediate β-TrCP1-dependent MYO10 degradation. The level of phosphorylated MYO10 protein transiently increases during mitosis, which is accompanied by a spatiotemporal cellular localization change first accumulating at the centrosome then at the midbody. Depletion of MYO10 or expression of MYO10 degron mutants, including those found in cancer patients, disrupts mitosis, increases genomic instability and inflammation, and promotes tumor growth; however, they also increase the sensitivity of cancer cells to Taxol. Our studies demonstrate a critical role of MYO10 in mitosis progression, through which it regulates genome stability, cancer growth, and cellular response to mitotic toxins.

Mechanisms of chromosomal instability (CIN) tolerance in aggressive tumors: surviving the genomic chaos

Chromosomal instability (CIN) is a pervasive feature of human cancers involved in tumor initiation and progression and which is found elevated in metastatic stages. CIN can provide survival and adaptation advantages to human cancers. However, too much of a good thing may come at a high cost for tumor cells as excessive degree of CIN-induced chromosomal aberrations can be detrimental for cancer cell survival and proliferation. Thus, aggressive tumors adapt to cope with ongoing CIN and most likely develop unique susceptibilities that can be their Achilles' heel. Determining the differences between the tumor-promoting and tumor-suppressing effects of CIN at the molecular level has become one of the most exciting and challenging aspects in cancer biology. In this review, we summarized the state of knowledge regarding the mechanisms reported to contribute to the adaptation and perpetuation of aggressive tumor cells carrying CIN. The use of genomics, molecular biology, and imaging techniques is significantly enhancing the understanding of the intricate mechanisms involved in the generation of and adaptation to CIN in experimental models and patients, which were not possible to observe decades ago. The current and future research opportunities provided by these advanced techniques will facilitate the repositioning of CIN exploitation as a feasible therapeutic opportunity and valuable biomarker for several types of human cancers.

HPV16 E6 induces chromosomal instability due to polar chromosomes caused by E6AP-dependent degradation of the mitotic kinesin CENP-E

Chromosome segregation during mitosis is highly regulated to ensure production of genetically identical progeny. Recurrent mitotic errors cause chromosomal instability (CIN), a hallmark of tumors. The E6 and E7 oncoproteins of high-risk human papillomavirus (HPV), which causes cervical, anal, and head and neck cancers (HNC), cause mitotic defects consistent with CIN in models of anogenital cancers, but this has not been studied in the context of HNC. Here, we show that HPV16 induces a specific type of CIN in patient HNC tumors, patient-derived xenografts, and cell lines, which is due to defects in chromosome congression. These defects are specifically induced by the HPV16 oncogene E6 rather than E7. We show that HPV16 E6 expression causes degradation of the mitotic kinesin CENP-E, whose depletion produces chromosomes that are chronically misaligned near spindle poles (polar chromosomes) and fail to congress. Though the canonical oncogenic role of E6 is the degradation of the tumor suppressor p53, CENP-E degradation and polar chromosomes occur independently of p53. Instead, E6 directs CENP-E degradation in a proteasome-dependent manner via the E6-associated ubiquitin protein ligase E6AP/UBE3A. This study reveals a mechanism by which HPV induces CIN, which may impact HPV-mediated tumor initiation, progression, and therapeutic response.

cGAS-STING signalling in cancer: striking a balance with chromosomal instability

Chromosomal instability (CIN) is a hallmark of cancer that drives tumour evolution. It is now recognised that CIN in cancer leads to the constitutive production of misplaced DNA in the form of micronuclei and chromatin bridges. These structures are detected by the nucleic acid sensor cGAS, leading to the production of the second messenger 2'3'-cGAMP and activation of the critical hub of innate immune signalling STING. Activation of this immune pathway should instigate the influx and activation of immune cells, resulting in the eradication of cancer cells. That this does not universally occur in the context of CIN remains an unanswered paradox in cancer. Instead, CIN-high cancers are notably adept at immune evasion and are highly metastatic with typically poor outcomes. In this review, we discuss the diverse facets of the cGAS-STING signalling pathway, including emerging roles in homeostatic processes and their intersection with genome stability regulation, its role as a driver of chronic pro-tumour inflammation, and crosstalk with the tumour microenvironment, which may collectively underlie its apparent maintenance in cancers. A better understanding of the mechanisms whereby this immune surveillance pathway is commandeered by chromosomally unstable cancers is critical to the identification of new vulnerabilities for therapeutic exploitation.

Oncogene-like addiction to aneuploidy in human cancers

Most cancers exhibit aneuploidy, but its functional significance in tumor development is controversial. Here, we describe ReDACT (Restoring Disomy in Aneuploid cells using CRISPR Targeting), a set of chromosome engineering tools that allow us to eliminate specific aneuploidies from cancer genomes. Using ReDACT, we created a panel of isogenic cells that have or lack common aneuploidies, and we demonstrate that trisomy of chromosome 1q is required for malignant growth in cancers harboring this alteration. Mechanistically, gaining chromosome 1q increases the expression of MDM4 and suppresses TP53 signaling, and we show that TP53 mutations are mutually-exclusive with 1q aneuploidy in human cancers. Thus, specific aneuploidies play essential roles in tumorigenesis, raising the possibility that targeting these "aneuploidy addictions" could represent a novel approach for cancer treatment.

Novel assay to measure chromosome instability identifies Punica granatum extract that elevates CIN and has a potential for tumor- suppressing therapies

Human artificial chromosomes (HACs) have provided a useful tool to study kinetochore structure and function, gene delivery, and gene expression. The HAC propagates and segregates properly in the cells. Recently, we have developed an experimental high-throughput imaging (HTI) HAC-based assay that allows the identification of genes whose depletion leads to chromosome instability (CIN). The HAC carries a GFP transgene that facilitates quantitative measurement of CIN. The loss of HAC/GFP may be measured by flow cytometry or fluorescence scanning microscope. Therefore, CIN rate can be measured by counting the proportion of fluorescent cells. Here, the HAC/GFP-based assay has been adapted to screen anticancer compounds for possible induction or elevation of CIN. We analyzed 24 cytotoxic plant extracts. Punica granatum leaf extract (PLE) indeed sharply increases CIN rate in HT1080 fibrosarcoma cells. PLE treatment leads to cell cycle arrest, reduction of mitotic index, and the increased numbers of micronuclei (MNi) and nucleoplasmic bridges (NPBs). PLE-mediated increased CIN correlates with the induction of double-stranded breaks (DSBs). We infer that the PLE extract contains a component(s) that elevate CIN, making it a candidate for further study as a potential cancer treatment. The data also provide a proof of principle for the utility of the HAC/GFP-based system in screening for natural products and other compounds that elevate CIN in cancer cells.

Micronuclei from misaligned chromosomes that satisfy the spindle assembly checkpoint in cancer cells

Chromosome alignment to the spindle equator is a hallmark of mitosis thought to promote chromosome segregation fidelity in metazoans. Yet chromosome alignment is only indirectly supervised by the spindle assembly checkpoint (SAC) as a byproduct of chromosome bi-orientation, and the consequences of defective chromosome alignment remain unclear. Here, we investigated how human cells respond to chromosome alignment defects of distinct molecular nature by following the fate of live HeLa cells after RNAi-mediated depletion of 125 proteins previously implicated in chromosome alignment. We confirmed chromosome alignment defects upon depletion of 108/125 proteins. Surprisingly, in all confirmed cases, depleted cells frequently entered anaphase after a delay with misaligned chromosomes. Using depletion of prototype proteins resulting in defective chromosome alignment, we show that misaligned chromosomes often satisfy the SAC and directly missegregate without lagging behind in anaphase. In-depth analysis of specific molecular perturbations that prevent proper kinetochore-microtubule attachments revealed that misaligned chromosomes that missegregate frequently result in micronuclei. Higher-resolution live-cell imaging indicated that, contrary to most anaphase lagging chromosomes that correct and reintegrate the main nuclei, misaligned chromosomes are a strong predictor of micronuclei formation in a cancer cell model of chromosomal instability, but not in non-transformed near-diploid cells. We provide evidence supporting that intrinsic differences in kinetochore-microtubule attachment stability on misaligned chromosomes account for this distinct outcome. Thus, misaligned chromosomes that satisfy the SAC may represent a previously overlooked mechanism driving chromosomal/genomic instability during cancer cell division, and we unveil genetic conditions predisposing for these events.

Mitotic Checkpoint Imbalances in Familial Cancer

Numerical chromosomal aberrations are highly frequent in cancer cells. However, tumor-associated mutations in regulators of the mitotic machinery that controls chromosome segregation are rather rare. By sequencing families with hereditary cancer, Chen and colleagues report two novel heterozygous mutations in CDC20, a coactivator of the anaphase-promoting complex (APC/C) and a target of the spindle assembly checkpoint (SAC) that prevents chromosome missegregation during mitosis. CDC20 mutations result in partial SAC functionality and segregate with tumor susceptibility in families with aneuploid ovarian cancers and other malignancies. The expression of these mutations in a knock-in mouse model accelerates the development of Myc-induced lymphomas and mortality, strongly supporting the notion that partial dysfunction of mitotic regulators may have profound implications in spontaneous and hereditary cancer. See related article by Chen et al., p. 3499.

Kinesin-7 CENP-E is essential for chromosome alignment and spindle assembly of mouse spermatocytes

Genome stability depends on chromosome congression and alignment during cell division. Kinesin-7 CENP-E is critical for kinetochore-microtubule attachment and chromosome alignment, which contribute to genome stability in mitosis. However, the functions and mechanisms of CENP-E in the meiotic division of male spermatocytes remain largely unknown. In this study, by combining the use of chemical inhibitors, siRNA-mediated gene knockdown, immunohistochemistry, and high-resolution microscopy, we have found that CENP-E inhibition results in chromosome misalignment and metaphase arrest in dividing spermatocyte during meiosis. Strikingly, we have revealed that CENP-E regulates spindle organization in metaphase I spermatocytes and cultured GC-2 spd cells. CENP-E depletion leads to spindle elongation, chromosome misalignment, and chromosome instability in spermatocytes. Together, these findings indicate that CENP-E mediates the kinetochore recruitment of BubR1, spindle assembly checkpoint and chromosome alignment in dividing spermatocytes, which finally contribute to faithful chromosome segregation and chromosome stability in the male meiotic division.

Genomic instability genes in lung and colon adenocarcinoma indicate organ specificity of transcriptomic impact on Copy Number Alterations

Genomic instability (GI) in cancer facilitates cancer evolution and is an exploitable target for therapy purposes. However, specific genes involved in cancer GI remain elusive. Causal genes for GI via expressions have not been comprehensively identified in colorectal cancers (CRCs). To fill the gap in knowledge, we developed a data mining strategy (Gene Expression to Copy Number Alterations; "GE-CNA"). Here we applied the GE-CNA approach to 592 TCGA CRC datasets, and identified 500 genes whose expression levels associate with CNA. Among these, 18 were survival-critical (i.e., expression levels correlate with significant differences in patients' survival). Comparison with previous results indicated striking differences between lung adenocarcinoma and CRC: (a) less involvement of overexpression of mitotic genes in generating genomic instability in the colon and (b) the presence of CNA-suppressing pathways, including immune-surveillance, was only partly similar to those in the lung. Following 13 genes (TIGD6, TMED6, APOBEC3D, EP400NL, B3GNT4, ZNF683, FOXD4, FOXD4L1, PKIB, DDB2, MT1G, CLCN3, CAPS) were evaluated as potential drug development targets (hazard ratio [> 1.3 or < 0.5]). Identification of specific CRC genomic instability genes enables researchers to develop GI targeting approach. The new results suggest that the "targeting genomic instability and/or aneuploidy" approach must be tailored for specific organs.

Clonal heterogeneity and rates of specific chromosome gains are risk predictors in childhood high-hyperdiploid B-cell acute lymphoblastic leukemia

B‐cell acute lymphoblastic leukemia (B‐ALL) is the commonest childhood cancer. High hyperdiploidy (HHD) identifies the most frequent cytogenetic subgroup in childhood B‐ALL. Although hyperdiploidy represents an important prognostic factor in childhood B‐ALL, the specific chromosome gains with prognostic value in HHD‐B‐ALL remain controversial, and the current knowledge about the hierarchy of chromosome gains, clonal heterogeneity and chromosomal instability in HHD‐B‐ALL remains very limited. We applied automated sequential‐iFISH coupled with single‐cell computational modeling to identify the specific chromosomal gains of the eight typically gained chromosomes in a large cohort of 72 primary diagnostic (DX, n = 62) and matched relapse (REL, n = 10) samples from HHD‐B‐ALL patients with either favorable or unfavorable clinical outcome in order to characterize the clonal heterogeneity, specific chromosome gains and clonal evolution. Our data show a high degree of clonal heterogeneity and a hierarchical order of chromosome gains in DX samples of HHD‐B‐ALL. The rates of specific chromosome gains and clonal heterogeneity found in DX samples differ between HHD‐B‐ALL patients with favorable or unfavorable clinical outcome. In fact, our comprehensive analyses at DX using a computationally defined risk predictor revealed low levels of trisomies +18+10 and low levels of clonal heterogeneity as robust relapse risk factors in minimal residual disease (MRD)‐negative childhood HHD‐B‐ALL patients: relapse‐free survival beyond 5 years: 22.1% versus 87.9%, P < 0.0001 and 33.3% versus 80%, P < 0.0001, respectively. Moreover, longitudinal analysis of matched DX‐REL HHD‐B‐ALL samples revealed distinct patterns of clonal evolution at relapse. Our study offers a reliable prognostic sub‐stratification of pediatric MRD‐negative HHD‐B‐ALL patients.

Polar Chromosomes-Challenges of a Risky Path

The process of chromosome congression and alignment is at the core of mitotic fidelity. In this review, we discuss distinct spatial routes that the chromosomes take to align during prometaphase, which are characterized by distinct biomolecular requirements. Peripheral polar chromosomes are an intriguing case as their alignment depends on the activity of kinetochore motors, polar ejection forces, and a transition from lateral to end-on attachments to microtubules, all of which can result in the delayed alignment of these chromosomes. Due to their undesirable position close to and often behind the spindle pole, these chromosomes may be particularly prone to the formation of erroneous kinetochore-microtubule interactions, such as merotelic attachments. To prevent such errors, the cell employs intricate mechanisms to preposition the spindle poles with respect to chromosomes, ensure the formation of end-on attachments in restricted spindle regions, repair faulty attachments by error correction mechanisms, and delay segregation by the spindle assembly checkpoint. Despite this protective machinery, there are several ways in which polar chromosomes can fail in alignment, mis-segregate, and lead to aneuploidy. In agreement with this, polar chromosomes are present in certain tumors and may even be involved in the process of tumorigenesis.

Quantifying chromosomal instability from intratumoral karyotype diversity using agent-based modeling and Bayesian inference

Chromosomal instability (CIN)-persistent chromosome gain or loss through abnormal mitotic segregation-is a hallmark of cancer that drives aneuploidy. Intrinsic chromosome mis-segregation rate, a measure of CIN, can inform prognosis and is a promising biomarker for response to anti-microtubule agents. However, existing methodologies to measure this rate are labor intensive, indirect, and confounded by selection against aneuploid cells, which reduces observable diversity. We developed a framework to measure CIN, accounting for karyotype selection, using simulations with various levels of CIN and models of selection. To identify the model parameters that best fit karyotype data from single-cell sequencing, we used approximate Bayesian computation to infer mis-segregation rates and karyotype selection. Experimental validation confirmed the extensive chromosome mis-segregation rates caused by the chemotherapy paclitaxel (18.5 ± 0.5/division). Extending this approach to clinical samples revealed that inferred rates fell within direct observations of cancer cell lines. This work provides the necessary framework to quantify CIN in human tumors and develop it as a predictive biomarker.

Chromosome Changes in Soma and Germ Line: Heritability and Evolutionary Outcome

The origin and inheritance of chromosome changes provide the essential foundation for natural selection and evolution. The evolutionary fate of chromosome changes depends on the place and time of their emergence and is controlled by checkpoints in mitosis and meiosis. Estimating whether the altered genome can be passed to subsequent generations should be central when we consider a particular genome rearrangement. Through comparative analysis of chromosome rearrangements in soma and germ line, the potential impact of macromutations such as chromothripsis or chromoplexy appears to be fascinating. What happens with chromosomes during the early development, and which alterations lead to mosaicism are other poorly studied but undoubtedly essential issues. The evolutionary impact can be gained most effectively through chromosome rearrangements arising in male meiosis I and in female meiosis II, which are the last divisions following fertilization. The diversity of genome organization has unique features in distinct animals; the chromosome changes, their internal relations, and some factors safeguarding genome maintenance in generations under natural selection were considered for mammals.

Role of Senescence in Tumorigenesis and Anticancer Therapy

Although the role of senescence in many physiological and pathological processes is becoming more identifiable, many aspects of senescence are still enigmatic. A special attention is paid to the role of this phenomenon in tumor development and therapy. This review mainly deals with a large spectrum of oncological issues, beginning with therapy-induced senescence and ending with oncogene-induced senescence. Moreover, the role of senescence in experimental approaches, such as primary cancer cell culture or reprogramming into stem cells, is also beginning to receive further consideration. Additional focus is made on senescence resulting from mitotic catastrophe processes triggered by events occurring during mitosis and jeopardizing chromosomal stability. It has to be also realized that based on recent findings, the basics of senescent cell property interpretation, such as irreversibility of proliferation blockade, can be undermined. It shows that the definition of senescence probably requires updating. Finally, the role of senescence is lately more understandable in the immune system, especially since senescence can diminish the effectiveness of the chimeric antigen receptor T-cell (CAR-T) therapy. In this review, we summarize the current knowledge regarding all these issues.

Differential gene expression and network analysis in head and neck squamous cell carcinoma

Head and neck squamous cell carcinoma (HNSCC) is a prevalent malignancy with a poor prognosis, whose biomarkers have not been studied in great detail. We have collected genomic data of HNSCC patients from The Cancer Genome Atlas (TCGA) and analyzed them to get deeper insights into the gene expression pattern. Initially, 793 differentially expressed genes (DEGs) were categorized, and their enrichment analysis was performed. Later, a protein-protein interaction network for the DEGs was constructed using the STRING plugin in Cytoscape to study their interactions. A set of 10 hub genes was selected based on Maximal Clique Centrality score, and later their survival analysis was studied. The elucidated set of 10 genes, i.e., PRAME, MAGEC2, MAGEA12, LHX1, MAGEA3, CSAG1, MAGEA6, LCE6A, LCE2D, LCE2C, referred to as potential candidates to be explored as HNSCC biomarkers. The Kaplan-Meier overall survival of the selected genes suggested that the alterations in the candidate genes were linked to the decreased survival of the HNSCC patients. Altogether, the results of this study signify that the genomic alterations and differential expression of the selected genes can be explored in therapeutic interpolations of HNSCC, exploiting early diagnosis and target-propelled therapy.

Clinical Applications of Aneuploidies in Evolution of NSCLC Patients: Current Status and Application Prospect

As one of the first characteristics of cancer cells, chromosomal aberrations during cell division have been well documented. Aneuploidy is a feature of most cancer cells accompanied by an elevated rate of mis-segregation of chromosomes, called chromosome instability (CIN). Aneuploidy causes ongoing karyotypic changes that contribute to tumor heterogeneity, drug resistance, and treatment failure, which are considered predictors of poor prognosis. Lung cancer (LC) is the leading cause of cancer-related deaths worldwide, and its genome map shows extensive aneuploid changes. Elucidating the role of aneuploidy in the pathogenesis of LC will reveal information about the key factors of tumor occurrence and development, help to predict the prognosis of cancer, clarify tumor evolution, metastasis, and drug response, and may promote the development of precision oncology. In this review, we describe many possible causes of aneuploidy and provide evidence of the role of aneuploidy in the evolution of LC, providing a basis for future biological and clinical research.

Cell cycle control in cancer

Cancer is a group of diseases in which cells divide continuously and excessively. Cell division is tightly regulated by multiple evolutionarily conserved cell cycle control mechanisms, to ensure the production of two genetically identical cells. Cell cycle checkpoints operate as DNA surveillance mechanisms that prevent the accumulation and propagation of genetic errors during cell division. Checkpoints can delay cell cycle progression or, in response to irreparable DNA damage, induce cell cycle exit or cell death. Cancer-associated mutations that perturb cell cycle control allow continuous cell division chiefly by compromising the ability of cells to exit the cell cycle. Continuous rounds of division, however, create increased reliance on other cell cycle control mechanisms to prevent catastrophic levels of damage and maintain cell viability. New detailed insights into cell cycle control mechanisms and their role in cancer reveal how these dependencies can be best exploited in cancer treatment.

Chromosome Missegregation as a Modulator of Radiation Sensitivity

Chromosome missegregation over the course of multiple cell divisions, termed chromosomal instability (CIN), is a hallmark of cancer. Multiple causes of CIN have been identified, including defects in the mitotic checkpoint, altered kinetochore-microtubule dynamics, centrosome amplification, and ionizing radiation. Here we review the types, mechanisms, and cellular implications of CIN. We discuss the evidence that CIN can promote tumors, suppress them, or do neither, depending on the rates of chromosome missegregration and the cellular context. Very high rates of chromosome missegregation lead to cell death due to loss of essential chromosomes; thus elevating CIN above a tolerable threshold provides a mechanistic opportunity to promote cancer cell death. Lethal rates of CIN can be achieved by a single insult or through a combination of insults. Because ionizing radiation induces CIN, additional therapies that increase CIN may serve as useful modulators of radiation sensitivity. Ultimately, quantifying the intrinsic CIN in a tumor and modulating this level pharmacologically as well as with radiation may allow for a more rational, personalized radiation therapy prescription, thereby decreasing side effects and increasing local control.

Centrosome Aberrations as Drivers of Chromosomal Instability in Breast Cancer

Chromosomal instability (CIN), or the dynamic change in chromosome number and composition, has been observed in cancer for decades. Recently, this phenomenon has been implicated as facilitating the acquisition of cancer hallmarks and enabling the formation of aggressive disease. Hence, CIN has the potential to serve as a therapeutic target for a wide range of cancers. CIN in cancer often occurs as a result of disrupting key regulators of mitotic fidelity and faithful chromosome segregation. As a consequence of their essential roles in mitosis, dysfunctional centrosomes can induce and maintain CIN. Centrosome defects are common in breast cancer, a heterogeneous disease characterized by high CIN. These defects include amplification, structural defects, and loss of primary cilium nucleation. Recent studies have begun to illuminate the ability of centrosome aberrations to instigate genomic flux in breast cancer cells and the tumor evolution associated with aggressive disease and poor patient outcomes. Here, we review the role of CIN in breast cancer, the processes by which centrosome defects contribute to CIN in this disease, and the emerging therapeutic approaches that are being developed to capitalize upon such aberrations.

Capturing cancer evolution using genetically engineered mouse models (GEMMs)

Initiating from a single cell, cancer undergoes clonal evolution, leading to a high degree of intratumor heterogeneity (ITH). The arising genetic heterogeneity between cancer cells is influenced by exogenous and endogenous forces that shape the composition of clones within tumors. Preclinical mouse models have provided a valuable tool for understanding cancer, helping to build a fundamental understanding of tumor initiation, progression, and metastasis. Until recently, genetically engineered mouse models (GEMMS) of cancer had lacked the genetic diversity found in human tumors, in which evolution may be driven by long-term carcinogen exposure and DNA damage. However, advances in sequencing technology and in our understanding of the drivers of genetic instability have given us the knowledge to generate new mouse models, offering an approach to functionally explore mechanisms of tumor evolution.

Chromosomal instability and aneuploidy as causes of cancer drug resistance

High levels of aneuploidy and chromosomal instability (CIN) are correlated with poor patient outcomes, though the mechanism(s) underlying this relationship have not been established. Recent evidence has demonstrated that chromosome copy number changes can function as point mutation-independent sources of drug resistance in cancer, which may partially explain this clinical association. CIN generates intratumoral heterogeneity in the form of gene dosage alterations, upon which the selective pressures induced by drug treatments can act. Thus, although CIN and aneuploidy impair cell fitness under most conditions, CIN can augment cellular adaptability, establishing CIN as a bet-hedging mechanism in tumor evolution. CIN may also endow cancers with unique vulnerabilities, which could be exploited therapeutically to achieve better patient outcomes.

Studying the Role of Chromosomal Instability (CIN) in GI Cancers Using Patient-derived Organoids

Chromosomal instability (CIN) is associated with the initiation and progression of gastrointestinal (GI) tract cancers. Cancers of the GI tract are typically characterized by altered chromosome numbers. While the dynamics of CIN have been extensively characterized in 2D monolayer cell cultures derived from GI tumors, the tumor microenvironment and 3D tumor architecture also contribute to the progression of CIN, which is not captured in 2D cell culture systems. To overcome these limitations, self-organizing cellular structures that retain organ-specific 3D architecture, namely organoids, have been derived from various tissues of the GI tract. Organoids derived from normal tissue and patient tumors serve as a useful paradigm to study the crosstalk between tumor cells in the context of a tissue microenvironment and its impact on chromosomal stability. Such a paradigm, therefore, has a considerable advantage over 2D cell culture systems in drug screening and personalized medicine. Here, we review the importance of patient-derived tumor organoids (PDTOs) as a model to study CIN in cancers of the GI tract.

Therapeutic targeting of the PLK1-PRC1-axis triggers cell death in genomically silent childhood cancer

Chromosomal instability (CIN) is a hallmark of cancer1. Yet, many childhood cancers, such as Ewing sarcoma (EwS), feature remarkably 'silent' genomes with minimal CIN2. Here, we show in the EwS model how uncoupling of mitosis and cytokinesis via targeting protein regulator of cytokinesis 1 (PRC1) or its activating polo-like kinase 1 (PLK1) can be employed to induce fatal genomic instability and tumor regression. We find that the EwS-specific oncogenic transcription factor EWSR1-FLI1 hijacks PRC1, which physiologically safeguards controlled cell division, through binding to a proximal enhancer-like GGAA-microsatellite, thereby promoting tumor growth and poor clinical outcome. Via integration of transcriptome-profiling and functional in vitro and in vivo experiments including CRISPR-mediated enhancer editing, we discover that high PRC1 expression creates a therapeutic vulnerability toward PLK1 inhibition that can repress even chemo-resistant EwS cells by triggering mitotic catastrophe.Collectively, our results exemplify how aberrant PRC1 activation by a dominant oncogene can confer malignancy but provide opportunities for targeted therapy, and identify PRC1 expression as an important determinant to predict the efficacy of PLK1 inhibitors being used in clinical trials.

Cancer Cell Fusion and Post-Hybrid Selection Process (PHSP)

Fusion of cancer cells either with other cancer cells (homotypic fusion) in local vicinity of the tumor tissue or with other cell types (e.g., macrophages, cancer-associated fibroblasts (CAFs), mesenchymal stromal-/stem-like cells (MSC)) (heterotypic fusion) represents a rare event. Accordingly, the clinical relevance of cancer-cell fusion events appears questionable. However, enhanced tumor growth and/or development of certain metastases can originate from cancer-cell fusion. Formation of hybrid cells after cancer-cell fusion requires a post-hybrid selection process (PHSP) to cope with genomic instability of the parental nuclei and reorganize survival and metabolic functionality. The present review dissects mechanisms that contribute to a PHSP and resulting functional alterations of the cancer hybrids. Based upon new properties of cancer hybrid cells, the arising clinical consequences of the subsequent tumor heterogeneity after cancer-cell fusion represent a major therapeutic challenge. However, cellular partners during cancer-cell fusion such as MSC within the tumor microenvironment or MSC-derived exosomes may provide a suitable vehicle to specifically address and deliver anti-tumor cargo to cancer cells.

Chromosomal instability sensitizes patient breast tumors to multipolar divisions induced by paclitaxel

Paclitaxel (Taxol) is a cornerstone of cancer treatment. However, its mechanism of cytotoxicity is incompletely understood and not all patients benefit from treatment. We show that patients with breast cancer did not accumulate sufficient intratumoral paclitaxel to induce mitotic arrest in tumor cells. Instead, clinically relevant concentrations induced multipolar mitotic spindle formation. However, the extent of early multipolarity did not predict patient response. Whereas multipolar divisions frequently led to cell death, multipolar spindles focused into bipolar spindles before division at variable frequency, and maintaining multipolarity throughout mitosis was critical to induce the high rates of chromosomal instability necessary for paclitaxel to elicit cell death. Increasing multipolar divisions in paclitaxel resulted in improved cytotoxicity. Conversely, decreasing paclitaxel-induced multipolar divisions reduced paclitaxel efficacy. Moreover, we found that preexisting chromosomal instability sensitized breast cancer cells to paclitaxel. Both genetic and pharmacological methods of inducing chromosomal instability were sufficient to increase paclitaxel efficacy. In patients, the amount of pretreatment chromosomal instability directly correlated with taxane response in metastatic breast cancer such that patients with a higher rate of preexisting chromosomal instability showed improved response to taxanes. Together, these results support the use of baseline rates of chromosomal instability as a predictive biomarker for paclitaxel response. Furthermore, they suggest that agents that increase chromosomal instability or maintain multipolar spindles throughout mitosis will improve the clinical utility of paclitaxel.

Gene Duplication and Gene Fusion Are Important Drivers of Tumourigenesis during Cancer Evolution

Chromosomal rearrangement and genome instability are common features of cancer cells in human. Consequently, gene duplication and gene fusion events are frequently observed in human malignancies and many of the products of these events are pathogenic, representing significant drivers of tumourigenesis and cancer evolution. In certain subsets of cancers duplicated and fused genes appear to be essential for initiation of tumour formation, and some even have the capability of transforming normal cells, highlighting the importance of understanding the events that result in their formation. The mechanisms that drive gene duplication and fusion are unregulated in cancer and they facilitate rapid evolution by selective forces akin to Darwinian survival of the fittest on a cellular level. In this review, we examine current knowledge of the landscape and prevalence of gene duplication and gene fusion in human cancers.

Transcriptomic Changes Following Partial Depletion of CENP-E in Normal Human Fibroblasts

The centromere is a fundamental chromosome structure in which the macro-molecular kinetochore assembles and is bound by spindle microtubules, allowing the segregation of sister chromatids during mitosis. Any alterations in kinetochore assembly or functioning or kinetochore-microtubule attachments jeopardize chromosome stability, leading to aneuploidy, a common feature of cancer cells. The spindle assembly checkpoint (SAC) supervises this process, ensuring a faithful segregation of chromosomes. CENP-E is both a protein of the kinetochore and a crucial component of the SAC required for kinetochore-microtubule capture and stable attachment, as well as congression of chromosomes to the metaphase plate. As the function of CENP-E is restricted to mitosis, its haploinsufficiency has been used to study the induced cell aneuploidy; however, the gene expression profile triggered by CENP-E reduction in normal cells has never been explored. To fill this gap, here we investigated whether a gene network exists that is associated with an siRNA-induced 50% reduction in CENP-E and consequent aneuploidy. Gene expression microarray analyses were performed at early and late timepoints after transfection. Initially, cell cycle regulation and stress response pathways were downregulated, while afterwards pathways involved in epithelial-mesenchymal transition, hypoxia and xenobiotic metabolism were altered. Collectively, our results suggest that CENP-E reduction triggers a gene expression program that recapitulates some features of tumor cells.

Transient genomic instability drives tumorigenesis through accelerated clonal evolution

In this study, Shoshani et al. tested the role of aneuploidy in tumor initiation and progression, and generated mice with random aneuploidies by transient induction of polo-like kinase 4 (Plk4), a master regulator of centrosome number. Their findings show how transient CIN generates cells with random aneuploidies from which ones that acquire a karyotype with specific chromosome gains are sufficient to drive cancer formation, and that distinct CIN mechanisms can lead to similar karyotypic cancer-causing outcomes.

Abnormal numerical and structural chromosome content is frequently found in human cancer. To test the role of aneuploidy in tumor initiation and progression, we generated mice with random aneuploidies by transient induction of polo-like kinase 4 (Plk4), a master regulator of centrosome number. Short-term chromosome instability (CIN) from transient Plk4 induction resulted in formation of aggressive T-cell lymphomas in mice with heterozygous inactivation of one p53 allele and accelerated tumor development in the absence of p53. Transient CIN increased the frequency of lymphoma-initiating cells with a specific karyotype profile, including trisomy of chromosomes 4, 5, 14, and 15 occurring early in tumorigenesis. Tumor development in mice with chronic CIN induced by an independent mechanism (through inactivation of the spindle assembly checkpoint) gradually trended toward a similar karyotypic profile, as determined by single-cell whole-genome DNA sequencing. Overall, we show how transient CIN generates cells with random aneuploidies from which ones that acquire a karyotype with specific chromosome gains are sufficient to drive cancer formation, and that distinct CIN mechanisms can lead to similar karyotypic cancer-causing outcomes.