Showing papers by "Michael R. Stratton published in 2023"
TL;DR: In this paper , the authors sequenced 342 microdissected normal epithelial crypts from the small intestines of 39 individuals and found that SBS2/SBS13 mutations were present in 17% of crypts, more frequent than most other normal tissues.
Abstract: APOBEC mutational signatures SBS2 and SBS13 are common in many human cancer types. However, there is an incomplete understanding of its stimulus, when it occurs in the progression from normal to cancer cell and the APOBEC enzymes responsible. Here we whole-genome sequenced 342 microdissected normal epithelial crypts from the small intestines of 39 individuals and found that SBS2/SBS13 mutations were present in 17% of crypts, more frequent than most other normal tissues. Crypts with SBS2/SBS13 often had immediate crypt neighbors without SBS2/SBS13, suggesting that the underlying cause of SBS2/SBS13 is cell-intrinsic. APOBEC mutagenesis occurred in an episodic manner throughout the human lifespan, including in young children. APOBEC1 mRNA levels were very high in the small intestine epithelium, but low in the large intestine epithelium and other tissues. The results suggest that the high levels of SBS2/SBS13 in the small intestine are collateral damage from APOBEC1 fulfilling its physiological function of editing APOB mRNA.
2 citations
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DOI•
TL;DR: SigProfilerAssignment as discussed by the authors is a desktop and an online computational framework for assigning all types of mutational signatures to individual samples, including copy-number signatures, to individual somatic mutations.
Abstract: Analysis of mutational signatures is a powerful approach for understanding the mutagenic processes that have shaped the evolution of a cancer genome. Here we present SigProfilerAssignment, a desktop and an online computational framework for assigning all types of mutational signatures to individual samples. SigProfilerAssignment is the first tool that allows both analysis of copy-number signatures and probabilistic assignment of signatures to individual somatic mutations. As its computational engine, the tool uses a custom implementation of the forward stagewise algorithm for sparse regression and nonnegative least squares for numerical optimization. Analysis of 2,700 synthetic cancer genomes with and without noise demonstrates that SigProfilerAssignment outperforms four commonly used approaches for assigning mutational signatures. SigProfilerAssignment is freely available at https://github.com/AlexandrovLab/SigProfilerAssignment with a web implementation at https://cancer.sanger.ac.uk/signatures/assignment/.
TL;DR: Stratton et al. as discussed by the authors reviewed the current understanding of the landscape of somatic mutations in normal cells, its causes and its consequences, and concluded that cancer is a recognized outcome of these mutations.
Abstract:
Mutations in DNA/RNA cause the phenotypic variation upon which natural selection acts during evolution. Mutations arise and are transmitted between generations of organisms and between generations of cells in the somatic tissues of multicellular organisms. However, our knowledge of the biological processes that generate mutations and the rates at which they occur in different cell types has been rudimentary until recently. Cancer is a recognized outcome of somatic mutations. However, we have limited understanding of the wider consequences of somatic mutations. I will review our current understanding of the landscape of somatic mutations in normal cells, its causes and its consequences.
Citation Format: Mike Stratton. Mutations in normal cell [abstract]. In: Proceedings of the AACR Special Conference: Aging and Cancer; 2022 Nov 17-20; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2022;83(2 Suppl_1):Abstract nr IA011.
TL;DR: Wang et al. as discussed by the authors used a Hierarchical Dirichlet Process (HDP) to extract mutational signatures from normal kidney tissue, which can be used to detect mutations in polyclonal tissues.
Abstract:
In recent years, large-scale whole genome sequencing of multiple types of cancer across multiple continents has been conducted as part of the “Mutographs” Cancer Grand Challenge to uncover unknown causes of cancer through detection of signatures of mutational processes operative during cancer development. Distinct mutational signatures have recently been detected by “Mutographs” in Renal Clear Cell Carcinomas (RCC) from different parts of the world. However, whether the detected mutational signatures are present in normal tissues or are initiated after tumorigenesis remains unknown.
In general, there has been a lack of knowledge of somatic mutations in normal cells primarily due to technological barriers to detection of somatic mutations in highly polyclonal normal tissues. However, a recently developed duplex sequencing technology, NanoSeq, uses copies of both strands of each DNA molecule to reduce sequencing errors to 10−9. With NanoSeq, we are able to detect somatic mutations in polyclonal tissues including the normal kidney. In this study, we used NanoSeq to sequence 288 tumor-adjacent normal kidney samples from multiple countries with varying RCC incidence. Subsequently, we conducted agnostic signature extraction using a Hierarchical Dirichlet Process to investigate whether the region specific mutational signatures found in cancers can be extracted from normal kidney tissue. The normal kidney tissues we sequenced have paired RCC whole genome sequencing data from the same individual. Therefore, the mutational profiles of normal kidney can be compared to paired cancer samples to ascertain the timing of the mutational processes causing the mutational signatures found in the cancers.
We confirmed that a predominantly T>C mutational signature that is highly enriched in Japanese RCC is present in normal kidney samples. A strong transcriptional strand bias in this signature provides circumstantial evidence that it is likely to have been caused by DNA damaging agents causing bulky DNA adducts which may be of environmental origin. A subset of RCC samples from Serbia and Romania had mutational signatures caused by aristolochic acids (AA). We found different dominant AA-related signatures in tumors compared to their matched normal tissues, potentially indicating different mutagenic or repair mechanisms between normal and cancer cells. Levels of SBS40, which is of unknown cause, were elevated in normal kidneys from the Czech Republic compared to other countries, and may contribute to the high RCC incidence in this country. In summary, this study provides the first systematic investigation of somatic mutations in normal kidney, revealing different mutational processes in different geographic regions and in cancer versus normal kidneys.
Citation Format: Yichen Wang, Sarah Moody, Behnoush Abedi-Ardekani, Calli Latimer, Saamin Cheema, Jingwei Wang, Stephen Fitzgerald, Laura Humphreys, Paul Brennan, Michael R. Stratton. Mutational processes in tumour-adjacent normal kidneys across countries with varying cancer incidence rates [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1168.