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  • American Association for Cancer Research (AACR)  (4)
  • Van Loo, Peter  (4)
  • 1
    Online Resource
    Online Resource
    American Association for Cancer Research (AACR) ; 2020
    In:  Cancer Research Vol. 80, No. 16_Supplement ( 2020-08-15), p. 1320-1320
    In: Cancer Research, American Association for Cancer Research (AACR), Vol. 80, No. 16_Supplement ( 2020-08-15), p. 1320-1320
    Abstract: Somatic mutation calling from bulk DNA sequencing is a complex problem susceptible to elevated false positive rates. High mapping quality is considered an important feature of reliable variant calls. At the resolution of short reads, ~10% of the genome displays high sequence similarity with at least one other genomic region and is assigned low mapping quality by alignment algorithms. These low-mapping-quality regions represent recurrent blind spots for mutation callers, which discard many of the variants they harbor, overlooking true biological variation. Here, we developed a pipeline to call substitutions in the low-mapping-quality genome. We used a published thesaurus approach to annotate the variant positions with their high-similarity links. We trained a classifier to emulate high-quality consensus calls made in unique regions using 20 features unrelated to mapping quality, reaching ~95% accuracy in those regions. In an independent sample more than 90% of the thesaurus calls were validated through linked-read sequencing. We then applied the classifier to all candidate substitutions of 2,658 cancer whole genomes from the PCAWG/ICGC consortium including variants falling in low-mapability regions. We retrieve hidden thesaurus variants genome-wide in ~6% of the genome, including genic, coding, and promoter regions. Thesaurus calls are directly proportional in numbers to somatic calls falling in the low-mapping-quality genome and share a similar trinucleotide context spectrum. Rescuing these mutations reveal hidden signal in known cancer genes, including PIK3CA, and excess of mutations genome-wide in promoter, untranslated, and coding regions of many other genes. We also find potential excess of non-synonymous mutations, including in genes from the TRIM and POTE families, having been previously implicated in multiple cancer types. Altogether, we developed a pipeline to call somatic substitutions in the low-mapping-quality genome and uncovered hidden somatic changes along the genomes of human cancers. In the future, this pipeline could be extended to indels and structural variants, and applied to the study of de novo germline variants. Citation Format: Maxime Tarabichi, Jonas Demeulemeester, Annelien Verfaillie, Peter Van Loo, Tomasz Konopka. The landscape of somatic substitutions in the repetitive genome across cancer types [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1320.
    Type of Medium: Online Resource
    ISSN: 0008-5472 , 1538-7445
    RVK:
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    Language: English
    Publisher: American Association for Cancer Research (AACR)
    Publication Date: 2020
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  • 2
    In: Cancer Research, American Association for Cancer Research (AACR), Vol. 82, No. 12_Supplement ( 2022-06-15), p. 1606-1606
    Abstract: Background Malignant peripheral nerve sheath tumors (MPNSTs) are rare, highly aggressive soft tissue sarcomas derived from Schwann cells with poor prognosis. Previous studies, although limited in scale and depth, have shown that these tumors are typically genomically complex, with a moderate burden of single nucleotide variants but extensive copy number aberrations (CNAs). Methods We applied a multi-omics approach to scrutinize the evolution and heterogeneity of a primary MPNST and five recurrence regions from one patient with an NF1 phenotype. Techniques utilized included bulk whole genome sequencing (WGS), single-cell DNA sequencing (scDNA-seq), single-cell RNA sequencing (scRNA-seq), simultaneous genome and transcriptome sequencing (G & T-seq), spatial transcriptomics, and laser capture microdissection (LCM)-based spatial genomics. Results We find significant heterogeneity in copy number profiles, suggestive of ongoing chromosomal instability and evolution. We perform in-depth tumor phylogenetic reconstruction from bulk WGS data. scDNA-seq revealed further CNA heterogeneity across and within regions, allowing us to refine the tree down to single-cell resolution. De novo somatic variant calling in scDNA-seq data confirms the reconstructed tree and identifies additional subclonal mutations. We also profile different populations of tumor and non-tumor cells and confirmed this with a genotyping approach. CNA profiles inferred from scRNA-seq reflect the within-region heterogeneity seen in scDNA-seq. We find tumor cells with similar CNA profiles typically cluster together by their gene expression profiles as well, implying that the majority of gene expression heterogeneity in this tumor is underpinned by copy number changes. By using CNA profiles as a native barcoding system, we link genetic subclones to clusters of cells and their transcriptomes to characterize the effects of gene dosage. Finally, we explore the spatial relationships between tumor subclones using LCM. We detect heterogeneity within tissue sections evidencing local clonal expansions and CNA events that follow spatial distributions. Using spatial transcriptomics, we show tumor cells are homogeneously admixed with tumor microenvironment populations. Conclusions Our work demonstrates the power of combining spatial multi-omics at the single-cell and bulk levels to study cancer evolution. This enables a spatio-temporal representation of a tumor’s development with annotation of genetic and transcriptomic events. Citation Format: Haixi Yan, Jonas Demeulemeester, Annelien Verfaillie, Cristina Cotobal Martin, Tom Kaufmann, Roland Schwarz, Thierry Voet, Simone Zaccaria, Adrienne Flanagan, Maxime Tarabichi, Peter Van Loo. Chromosomal instability drives spatial and temporal phenotypic diversity in Schwann cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1606.
    Type of Medium: Online Resource
    ISSN: 1538-7445
    Language: English
    Publisher: American Association for Cancer Research (AACR)
    Publication Date: 2022
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  • 3
    Online Resource
    Online Resource
    American Association for Cancer Research (AACR) ; 2022
    In:  Cancer Research Vol. 82, No. 12_Supplement ( 2022-06-15), p. 2286-2286
    In: Cancer Research, American Association for Cancer Research (AACR), Vol. 82, No. 12_Supplement ( 2022-06-15), p. 2286-2286
    Abstract: Genomic rearrangements are key mutational processes in a number of bone and soft tissue tumors (sarcomas). These events are used for both disease classification and as prognostic and predictive biomarkers. However, the rearrangement architecture and mutational processes giving rise to many of these events remain poorly characterized. Recent data indicate that sarcomas show particularly high frequencies of complex structural rearrangements, including patterns which do not fit those of known mutational mechanisms. As the largest whole genome sequencing (WGS) dataset of sarcomas to date, the Genomics England (GE) 100,000 Genomes Project represents a unique cohort in which to examine these events. Structural variants (SVs) were identified using five SV callers (Manta, Delly, LUMPY, SvABA and GRIDSS) in WGS data from 1330 GE samples. SVs were filtered to retain only those passing the quality filter, and to remove variants present in either matched germline samples or & gt;1% of a panel of normal variants. Caller performance was evaluated by comparison of distances between SV and copy number call breakpoints generated by Battenberg. SVs identified by at least two callers were taken forward as high-quality calls. Chromothriptic events, extrachromosomal DNA (ecDNA) and breakage-fusion-bridges were identified using established algorithms. In keeping with previous data, the prevalence of structural variants varies by tumor type, with particularly high numbers of SVs observed in liposarcoma and osteosarcoma. Many tumor types included notable outlier samples; these were more likely to show evidence of chromothripsis, as identified by a dedicated chromothripsis caller. Liposarcomas show the highest frequency of chromothripsis, as described previously. In addition, we have examined some tumor types at higher granularity than previously available, demonstrating directly that the prevalence of chromothripsis varies by histological subtype. For example, chromothriptic events are identified in 100% of well-differentiated liposarcomas, but less than 10% of myxoid liposarcomas. Similarly, the presence of ecDNA varies by tumor type, with the novel observation of particularly high rates in angiosarcoma. Despite recent advances in histological classification, the survival for patients with sarcoma has remained largely static for over 40 years. Determination of the mutational processes generating these rearrangements will shed light on the pathogenesis of these tumors. Citation Format: Sara Waise, Tom Lesluyes, Jonas Demeulemeester, Maxime Tarabichi, Sarcoma Genomics England Clinical Interpretation Partnership, Nischalan Pillay, Adrienne M. Flanagan, Peter Van Loo. Profiling the complex rearrangement landscape of sarcoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2286.
    Type of Medium: Online Resource
    ISSN: 1538-7445
    Language: English
    Publisher: American Association for Cancer Research (AACR)
    Publication Date: 2022
    detail.hit.zdb_id: 2036785-5
    detail.hit.zdb_id: 1432-1
    detail.hit.zdb_id: 410466-3
    Location Call Number Limitation Availability
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  • 4
    Online Resource
    Online Resource
    American Association for Cancer Research (AACR) ; 2022
    In:  Cancer Research Vol. 82, No. 12_Supplement ( 2022-06-15), p. 1698-1698
    In: Cancer Research, American Association for Cancer Research (AACR), Vol. 82, No. 12_Supplement ( 2022-06-15), p. 1698-1698
    Abstract: Introduction Cancers commonly accrue copy number gains and losses during their development. An improved understanding of their contribution to tumorigenesis can be gained by studying their distribution and evolution within and across tumor types. Materials and Methods We analyzed copy number profiles of 16,765 tumours from the Hartwig Medical Foundation, Pan-Cancer Analysis of Whole Genomes (PCAWG) and The Cancer Genome Atlas (TCGA) cohorts. We used a novel timing method, ComplexTiming, to time the occurrence of copy number gains, and a permutation-based approach to assess the distribution of copy number events relative to a null distribution. Results Complex copy number states in cancers that have undergone a whole-genome duplication (WGD) are commonly assumed to develop through a most parsimonious route, where the series of events leading to the complex copy number state requiring the least number of steps, is proposed to be the most likely one. Our newly developed ComplexTiming approach allows unique insights into the actual routes that led to these complex copy number states. In our large pan-cancer cohort, we found that the most parsimonious set of events does not occur in approximately 40% of cases. Additional gains more frequently occurred after WGD than before, reflecting a previously observed increase in instability. In squamous cell lung cancer, gains of 3q were frequently found before WGD. Additionally, 5q and 1q were significantly more likely to be gained before WGD in colorectal and melanoma metastases, respectively. Evaluating the distribution of copy number events, we found that the majority of copy number events are distributed across tumors consistent with a permutation model that assigns copy number events randomly. However, interestingly, in the majority of cancer types, we found copy number events that occurred more often than expected in individual tumors with low numbers of events, such as loss of chromosome 9 in bladder cancer, loss of 20p in colorectal adenocarcinomas, and gain of 1q in breast adenocarcinomas. These results suggest that the high-frequency of these specific copy number events is due to selection, while other copy number changes may occur neutrally due to innate chromosome instability. Conclusion The landscape of copy number gains in tumors is diverse. By analyzing the timing of these events as well as their distribution, we identify a subset of frequent copy number changes in different cancer types that are likely under selection. Citation Format: Toby Baker, Stefan Dentro, Paul Spellman, Maxime Tarabichi, Peter Van Loo. Copy number diversity within and across tumor types [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1698.
    Type of Medium: Online Resource
    ISSN: 1538-7445
    Language: English
    Publisher: American Association for Cancer Research (AACR)
    Publication Date: 2022
    detail.hit.zdb_id: 2036785-5
    detail.hit.zdb_id: 1432-1
    detail.hit.zdb_id: 410466-3
    Location Call Number Limitation Availability
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