Chromosomal Instability In Cancer Research Articles

Inference of chromosome selection parameters and missegregation rate in cancer from DNA-sequencing data

Aneuploidy is frequently observed in cancers and has been linked to poor patient outcome. Analysis of aneuploidy in DNA-sequencing (DNA-seq) data necessitates untangling the effects of the Copy Number Aberration (CNA) occurrence rates and the selection coefficients that act upon the resulting karyotypes. We introduce a parameter inference algorithm that takes advantage of both bulk and single-cell DNA-seq cohorts. The method is based on Approximate Bayesian Computation (ABC) and utilizes CINner, our recently introduced simulation algorithm of chromosomal instability in cancer. We examine three groups of statistics to summarize the data in the ABC routine: (A) Copy Number-based measures, (B) phylogeny tip statistics, and (C) phylogeny balance indices. Using these statistics, our method can recover both the CNA probabilities and selection parameters from ground truth data, and performs well even for data cohorts of relatively small sizes. We find that only statistics in groups A and C are well-suited for identifying CNA probabilities, and only group A carries the signals for estimating selection parameters. Moreover, the low number of CNA events at large scale compared to cell counts in single-cell samples means that statistics in group B cannot be estimated accurately using phylogeny reconstruction algorithms at the chromosome level. As data from both bulk and single-cell DNA-sequencing techniques becomes increasingly available, our inference framework promises to facilitate the analysis of distinct cancer types, differentiation between selection and neutral drift, and prediction of cancer clonal dynamics.

Chromosomal instability as a driver of cancer progression.

Chromosomal instability (CIN) refers to an increased propensity of cells to acquire structural and numerical chromosomal abnormalities during cell division, which contributes to tumour genetic heterogeneity. CIN has long been recognized as a hallmark of cancer, and evidence over the past decade has strongly linked CIN to tumour evolution, metastasis, immune evasion and treatment resistance. Until recently, the mechanisms by which CIN propels cancer progression have remained elusive. Beyond the generation of genomic copy number heterogeneity, recent work has unveiled additional tumour-promoting consequences of abnormal chromosome segregation. These mechanisms include complex chromosomal rearrangements, epigenetic reprogramming and the induction of cancer cell-intrinsic inflammation, emphasizing the multifaceted role of CIN in cancer.

Abstract SY03-03: Thinking outside the chromosome: Interrogating epigenetic mechanisms in noncanonical chromatin species

Abstract The epigenetic regulation of DNA-templated processes is intricately tied to numerous events that determine cell phenotype and fate. The abrogation of epigenetic cascades drives various disease states, including cancer. Many of these pathological phenomena involve major chromosomal arrangements that can include the generation of non-canonical chromatin structures existing in the primary nuclei or encapsulated in spatially distinct micronuclei. Recently, we undertook a mechanistic approach to investigate the properties of unique non-chromosomal structures, revealing significant epigenetic contributions to their regulation. We found that micronuclei, the result of chromosomal instability in cancer, assume altered epigenetic landscapes upon departure from the nucleus. Moreover, chromosomes sequestered in micronuclei retain the epigenetic "scars" after reintegration into the primary nucleus, contributing to epigenetic reprogramming and heterogeneity in cancer. Additionally, we turned our attention to the Hepatitis B Virus' (HBV) covalently closed circular DNA (cccDNA) minichromosome, which forms from viral DNA and human histones following infection. We found that chromatinization drives the expression of the key viral oncogene, HBx, and thus promotes viral infection. Elucidating this new mechanism enabled us to halt infection by inhibiting histone remodeling, creating a potential first-in-class therapy for HBV. These exciting findings demonstrate the key role of chromatin in biomedical events and how a fundamental understanding of these processes can lead to the identification of new therapeutic avenues. Citation Format: Yael David. Thinking outside the chromosome: Interrogating epigenetic mechanisms in noncanonical chromatin species [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr SY03-03.

Abstract 2704: cGAS-STING drives myeloid inflammation in chromosomally unstable esophageal cancer

Abstract Esophageal adenocarcinoma (EAC) is an aggressive disease characterized by chromosomal instability (CIN), whereby cells continuously acquire chromosomal abnormalities that promote therapeutic resistance, immune evasion and metastasis. CIN in cancers also fuels the misplacement of genomic DNA in the form of structural abnormalities of the nucleus, such as micronuclei (MN), that lead to chronic activation of the cytosolic DNA sensing cGAS-STING pathway. However, how chronic cGAS-STING pathway activation is tolerated and shapes the tumor landscape of CINhigh EAC cancers is poorly understood. Using publicly available RNA-seq and genome sequencing data of EAC tumours and esophageal cancer cell lines as well as a panel of EAC cell lines, we demonstrate that the core cGAS-STING pathway machinery is rarely inactivated in EAC despite high levels of baseline CIN and aneuploidy. Through transcriptomic profiling of an isogenic EAC precursor cell line model of variable CIN and cGASKO/WT EAC cell lines we show that both chronic and transient CIN-driven cGAS-STING activation converge on the expression of CXCR1/2 ligands and other pro-inflammatory cytokines and chemokines rather than typical anti-tumor type I interferon signalling in EAC cells. Indeed, a novel transcriptional signature of cGAS+ micronuclear burden-correlated genes correlates with orthogonal measures of CIN in EAC tumours and esophagogastric cancer cell lines and is associated with an enrichment in myeloid-derived cells as well as poor prognosis. Correspondingly, using multiplexed immunofluorescence (IF) we find that a high preponderance of cGAS+MN and STING expression in human EAC samples is associated with decreased tumor purity, increased myeloid cell and macrophage infiltration, and increased peripheral blood neutrophil counts, indicative of tumor-promoting myeloid inflammation. Ongoing multiplexed IF and single-nuclei RNAseq analysis of cGAS+MNhigh and cGAS+MNlow EAC tumors will further help characterise the components that comprise the CIN EAC tumor microenvironment (TME) and the CIN- and cGAS-STING-dependent cell-cell interactions that govern it. Taken together, our findings provide an explanation for the observed maintenance of cGAS and STING in EAC and identify disruption of cGAS-STING-dependent myeloid cell inflammation and recruitment as a potential therapeutic target for CINhigh EAC. Citation Format: Bruno Beernaert, Erkin Erdal, Rose Clark, Tong Liu, Ester M. Hammond, Eileen E. Parkes. cGAS-STING drives myeloid inflammation in chromosomally unstable esophageal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2704.

A Paradoxical Role for Somatic Chromosomal Mosaicism and Chromosome Instability in Cancer: Theoretical and Technological Aspects.

Somatic chromosomal mosaicism, chromosome instability, and cancer are intimately linked together. Addressing the role of somatic genome variations (encompassing chromosomal mosaicism and instability) in cancer yields paradoxical results. Firstly, somatic mosaicism for specific chromosomal rearrangement causes cancer per se. Secondly, chromosomal mosaicism and instability are associated with a variety of diseases (chromosomal disorders demonstrating less severe phenotypes, complex diseases), which exhibit cancer predisposition. Chromosome instability syndromes may be considered the best examples of these diseases. Thirdly, chromosomal mosaicism and instability are able to result not only in cancerous diseases but also in non-cancerous disorders (brain diseases, autoimmune diseases, etc.). Currently, the molecular basis for these three outcomes of somatic chromosomal mosaicism and chromosome instability remains incompletely understood. Here, we address possible mechanisms for the aforementioned scenarios using a system analysis model. A number of theoretical models based on studies dedicated to chromosomal mosaicism and chromosome instability seem to be valuable for disentangling and understanding molecular pathways to cancer-causing genome chaos. In addition, technological aspects of uncovering causes and consequences of somatic chromosomal mosaicism and chromosome instability are discussed. In total, molecular cytogenetics, cytogenomics, and system analysis are likely to form a powerful technological alliance for successful research against cancer.

Small-molecule inhibition of kinesin KIF18A reveals a mitotic vulnerability enriched in chromosomally unstable cancers

Chromosomal instability (CIN) is a hallmark of cancer, caused by persistent errors in chromosome segregation during mitosis. Aggressive cancers like high-grade serous ovarian cancer (HGSOC) and triple-negative breast cancer (TNBC) have a high frequency of CIN and TP53 mutations. Here, we show that inhibitors of the KIF18A motor protein activate the mitotic checkpoint and selectively kill chromosomally unstable cancer cells. Sensitivity to KIF18A inhibition is enriched in TP53-mutant HGSOC and TNBC cell lines with CIN features, including in a subset of CCNE1-amplified, CDK4–CDK6-inhibitor-resistant and BRCA1-altered cell line models. Our KIF18A inhibitors have minimal detrimental effects on human bone marrow cells in culture, distinct from other anti-mitotic agents. In mice, inhibition of KIF18A leads to robust anti-cancer effects with tumor regression observed in human HGSOC and TNBC models at well-tolerated doses. Collectively, our results provide a rational therapeutic strategy for selective targeting of CIN cancers via KIF18A inhibition.

High-throughput electron tomography identifies centriole over-elongation as an early event in plasma cell disorders

Plasma cell disorders are clonal outgrowths of pre-malignant or malignant plasma cells, characterized by extensive chromosomal aberrations. Centrosome abnormalities are a major driver of chromosomal instability in cancer but their origin, incidence, and composition in primary tumor cells is poorly understood. Using cutting-edge, semi-automated high-throughput electron tomography, we characterized at nanoscale 1386 centrioles in CD138pos plasma cells from eight healthy donors and 21 patients with plasma cell disorders, and 722 centrioles from different control populations. In plasma cells from healthy individuals, over-elongated centrioles accumulated with age. In plasma cell disorders, centriole over-elongation was notably frequent in early, pre-malignant disease stages, became less pronounced in overt multiple myeloma, and almost entirely disappeared in aggressive plasma cell leukemia. Centrioles in other types of patient-derived B cell neoplasms showed no over-elongation. In contrast to current belief, centriole length appears to be highly variable in long-lived, healthy plasma cells, and over-elongation and structural aberrations are common in this cell type. Our data suggest that structural centrosome aberrations accumulate with age in healthy CD138pos plasma cells and may thus play an important role in early aneuploidization as an oncogenic driver in plasma cell disorders.

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.

Chromosomal Instability as Enabling Feature and Central Hallmark of Breast Cancer.

Chromosomal instability (CIN) has become a topic of great interest in recent years, not only for its implications in cancer diagnosis and prognosis but also for its role as an enabling feature and central hallmark of cancer. CIN describes cell-to-cell variation in the number or structure of chromosomes in a tumor population. Although extensive research in recent decades has identified some associations between CIN with response to therapy, specific associations with other hallmarks of cancer have not been fully evidenced. Such associations place CIN as an enabling feature of the other hallmarks of cancer and highlight the importance of deepening its knowledge to improve the outcome in cancer. In addition, studies conducted to date have shown paradoxical findings about the implications of CIN for therapeutic response, with some studies showing associations between high CIN and better therapeutic response, and others showing the opposite: associations between high CIN and therapeutic resistance. This evidences the complex relationships between CIN with the prognosis and response to treatment in cancer. Considering the above, this review focuses on recent studies on the role of CIN in cancer, the cellular mechanisms leading to CIN, its relationship with other hallmarks of cancer, and the emerging therapeutic approaches that are being developed to target such instability, with a primary focus on breast cancer. Further understanding of the complexity of CIN and its association with other hallmarks of cancer could provide a better understanding of the cellular and molecular mechanisms involved in prognosis and response to treatment in cancer and potentially lead to new drug targets.

Loss of RanGAP1 drives chromosome instability and rapid tumorigenesis of osteosarcoma.

Chromothripsis is a catastrophic event of chromosomal instability that involves intensive fragmentation and rearrangements within localized chromosomal regions. However, its cause remains unclear. Here, we show that reduction and inactivation of Ran GTPase-activating protein 1 (RanGAP1) commonly occur in human osteosarcoma, which is associated with a high rate of chromothripsis. In rapidly expanding mouse osteoprogenitors, RanGAP1 deficiency causes chromothripsis in chr1q, instant inactivation of Rb1 and degradation of p53, consequent failure in DNA damage repair, and ultrafast osteosarcoma tumorigenesis. During mitosis, RanGAP1 anchors to the kinetochore, where it recruits PP1-γ to counteract the activity of the spindle-assembly checkpoint (SAC) and prevents TOP2A degradation, thus safeguarding chromatid decatenation. Loss of RanGAP1 causes SAC hyperactivation and chromatid decatenation failure. These findings demonstrate that RanGAP1 maintains mitotic chromosome integrity and that RanGAP1 loss drives tumorigenesis through its direct effects on SAC and decatenation and secondary effects on DNA damage surveillance.

Replication stress generates distinctive landscapes of DNA copy number alterations and chromosome scale losses

BackgroundA major driver of cancer chromosomal instability is replication stress, the slowing or stalling of DNA replication. How replication stress and genomic instability are connected is not known. Aphidicolin-induced replication stress induces breakages at common fragile sites, but the exact causes of fragility are debated, and acute genomic consequences of replication stress are not fully explored.ResultsWe characterize DNA copy number alterations (CNAs) in single, diploid non-transformed cells, caused by one cell cycle in the presence of either aphidicolin or hydroxyurea. Multiple types of CNAs are generated, associated with different genomic regions and features, and observed copy number landscapes are distinct between aphidicolin and hydroxyurea-induced replication stress. Coupling cell type-specific analysis of CNAs to gene expression and single-cell replication timing analyses pinpointed the causative large genes of the most recurrent chromosome-scale CNAs in aphidicolin. These are clustered on chromosome 7 in RPE1 epithelial cells but chromosome 1 in BJ fibroblasts. Chromosome arm level CNAs also generate acentric lagging chromatin and micronuclei containing these chromosomes.ConclusionsChromosomal instability driven by replication stress occurs via focal CNAs and chromosome arm scale changes, with the latter confined to a very small subset of chromosome regions, potentially heavily skewing cancer genome evolution. Different inducers of replication stress lead to distinctive CNA landscapes providing the opportunity to derive copy number signatures of specific replication stress mechanisms. Single-cell CNA analysis thus reveals the impact of replication stress on the genome, providing insights into the molecular mechanisms which fuel chromosomal instability in cancer.

WRN rescues replication forks compromised by a BRCA2 deficiency: Predictions for how inhibition of a helicase that suppresses premature aging tilts the balance to fork demise and chromosomal instability in cancer.

Hereditary breast and ovarian cancers are frequently attributed to germline mutations in the tumor suppressor genes BRCA1 and BRCA2. BRCA1/2 act to repair double-strand breaks (DSBs) and suppress the demise of unstable replication forks. Our work elucidated a dynamic interplay between BRCA2 and the WRN DNA helicase/exonuclease defective in the premature aging disorder Werner syndrome. WRN and BRCA2 participate in complementary pathways to stabilize replication forks in cancer cells, allowing them to proliferate. Whether the functional overlap of WRN and BRCA2 is relevant to replication at gaps between newly synthesized DNA fragments, protection of telomeres, and/or metabolism of secondary DNA structures remain to be determined. Advances in understanding the mechanisms elicited during replication stress have prompted the community to reconsider avenues for cancer therapy. Insights from studies of PARP or topoisomerase inhibitors provide working models for the investigation of WRN's mechanism of action. We discuss these topics, focusing on the implications of the WRN-BRCA2 genetic interaction under conditions of replication stress.

Interplay between symmetric arginine dimethylation and ubiquitylation regulates TDP1 proteostasis for the repair of topoisomerase I-DNA adducts.

Tyrosyl-DNA phosphodiesterase (TDP1) hydrolyzes the phosphodiester bond between a DNA 3' end and a tyrosyl moiety and is implicated in the repair of trapped topoisomerase I (Top1)-DNA covalent complexes (Top1cc). Protein arginine methyltransferase 5 (PRMT5) catalyzes arginine methylation of TDP1 at the residues R361 and R586. Here, we establish mechanistic crosstalk between TDP1 arginine methylation and ubiquitylation, which is critical for TDP1 homeostasis and cellular responses to Top1 poisons. We show that R586 methylation promotes TDP1 ubiquitylation, which facilitates ubiquitin/proteasome-dependent TDP1 turnover by impeding the binding of UCHL3 (deubiquitylase enzyme) with TDP1. TDP1-R586 also promotes TDP1-XRCC1 binding and XRCC1 foci formation at Top1cc-damage sites. Intriguingly, R361 methylation enhances the 3'-phosphodiesterase activity of TDP1 in real-time fluorescence-based cleavage assays, and this was rationalized using structural modeling. Together, our findings establish arginine methylation as a co-regulator of TDP1 proteostasis and activity, which modulates the repair of trapped Top1cc.

Targeting the Mitotic Kinesin KIF18A in Chromosomally Unstable Cancers: Hit Optimization Toward an In Vivo Chemical Probe.

Chromosomal instability (CIN) is a hallmark of cancer that results from errors in chromosome segregation during mitosis. Targeting of CIN-associated vulnerabilities is an emerging therapeutic strategy in drug development. KIF18A, a mitotic kinesin, has been shown to play a role in maintaining bipolar spindle integrity and promotes viability of CIN cancer cells. To explore the potential of KIF18A, a series of inhibitors was identified. Optimization of an initial hit led to the discovery of analogues that could be used as chemical probes to interrogate the role of KIF18A inhibition. Compounds 23 and 24 caused significant mitotic arrest in vivo, which was sustained for 24 h. This would be followed by cell death either in mitosis or in the subsequent interphase. Furthermore, photoaffinity labeling experiments reveal that this series of inhibitors binds at the interface of KIF18A and tubulin. This study represents the first disclosure of KIF18A inhibitors with in vivo activity.

Abstract IA12: Cancer evolution: Chromosomal instability and immune evasion

Abstract Evidence supports complex subclonal relationships in solid tumors, manifested as intratumor heterogeneity. Parallel evolution of subclones, with distinct somatic events occurring in the same gene, signal transduction pathway or protein complex, suggests constraints to tumor evolution that might be therapeutically exploitable. Data from TRACERx, a longitudinal lung cancer evolution study will be presented. Drivers of tumor heterogeneity change during the disease course and contribute to the temporally distinct origins of lung cancer driver events. APOBEC driven mutagenesis appears to be enriched in subclones in multiple tumor types. Oncogene, tumor suppressor gene and drug-induced DNA replication stress are found to drive APOBEC mutagenesis. On-going chromosomal instability, manifested as Mirrored Subclonal Allelic Imbalance (MSAI) is found to be a major driver of intratumor heterogeneity across cancer types, contributing to parallel evolution and selection. Subclonal driver events, evidence of ongoing selection within subclones, combined with genome instability driving cell-to-cell variation is likely to limit the efficacy of targeted monotherapies, suggesting a need for new approaches to drug development and integration of cancer immunotherapeutic approaches. Multiple adaptive mechanisms to neo-antigen evolution have been found in TRACERx highlighting cancer chromosomal instability driving immune evasion and HLA loss and loss of clonal neo-antigens as well as epigenetic repression of neo-antigens. The clonal neo-antigenic architecture may act as a tumor vulnerability to mitigate resistance and treatment failure. Citation Format: Charles Swanton. Cancer evolution: Chromosomal instability and immune evasion [abstract]. In: Abstracts: AACR Virtual Special Conference: Tumor Immunology and Immunotherapy; 2021 Oct 5-6. Philadelphia (PA): AACR; Cancer Immunol Res 2022;10(1 Suppl):Abstract nr IA12.

Multi-Modality Imaging Reveals Structural Centrosome Aberrations As a Potential Driver of Chromosomal Instability in Early-Stage Plasma Cell Disorders

Multi-Modality Imaging Reveals Structural Centrosome Aberrations As a Potential Driver of Chromosomal Instability in Early-Stage Plasma Cell Disorders

First person – Daniel Bronder

ABSTRACTFirst Person is a series of interviews with the first authors of a selection of papers published in Disease Models & Mechanisms, helping early-career researchers promote themselves alongside their papers. Daniel Bronder is first author on ‘ TP53 loss initiates chromosomal instability in fallopian tube epithelial cells’, published in DMM. Daniel conducted the research described in this article while a doctoral student in Thomas Ried and Stephen Taylor's labs at the National Cancer Institute, Bethesda, MD, USA and the University of Manchester, Manchester, UK. He is now a postdoctoral fellow in the lab of Samuel Bakhoum at Memorial Sloan Kettering Cancer Center, New York, NY, USA, investigating the causes and consequences of chromosomal instability in cancer.

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.

367P The analysis of STAG2 variants in Chinese adult patients with glioma

Gliomas are the most frequently occurring primary tumor of the central nervous system, of which HGG is an aggressive form with no effective therapy. So far, standard therapy in the adult setting includes maximal safe surgical resection followed by adjuvant temozolomide and radiation therapy (RT). Stromal Antigen-2 (STAG2) is a component of the cohesion complex that is required for DNA replication, the cohesion of the sister chromatids, and transcriptional regulation. Inactivating mutations in STAG2 can lead to aneuploidy and chromosomal instability in cancer.

Unraveling pathologies underlying chromosomal instability in cancers.

Aneuploidy is a widespread feature of malignant tumors that arises through persistent chromosome mis‐segregation in mitosis associated with a pathological condition called chromosomal instability, or CIN. Since CIN is known to have a causal relationship with poor prognosis accompanying by multi‐drug resistance, tumor relapse, and metastasis, many research groups have endeavored to understand the mechanisms underlying CIN. In this review, we overview possible etiologies of CIN. The key processes to achieve faithful chromosome segregation include the regulation of sister chromatid cohesion, kinetochore‐microtubule attachment, bipolar spindle formation, spindle‐assembly checkpoint, and the activity of separase. Aberrant chromosome structures during DNA replication might also be a potential cause of CIN. Defective regulation in these processes can lead to chromosome mis‐segregation, manifested by lagging chromosomes, and DNA bridges in anaphase, leading to gross chromosome rearrangements. Investigation into the molecular etiologies of CIN should allow us to explore novel strategies to intervene in CIN to control cancers.