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Dataset ID
Description
Technology
Samples
EGAD00001008092
Lynch Syndrome (LS) is an autosomal dominant disease conferring a high risk of colorectal cancer due to germline heterozygous mutations in a DNA mismatch repair (MMR) gene. Although cancers in LS patients show elevated somatic mutation burdens, information on mutation rates in normal tissues and understanding of the trajectory from normal to cancer cell is limited. Here we whole-genome sequenced 152 crypts from normal and neoplastic epithelial tissues from LS patients. In normal tissues the repertoire of mutational processes and mutation rates were similar to those found in wild type individuals. A morphologically normal colonic crypt with an increased mutation burden and mutational signatures consistent with MMR deficiency was identified, which may represent a very early stage of LS pathogenesis. Phylogenetic tress of tumour crypts indicated that the most recent ancestor cell of each tumour was already MMR deficient and had experienced multiple clonal evolution cycles. This study demonstrates the genomic stability of epithelial cells with heterozygous germline MMR gene mutations and highlights important differences in the pathogenesis of LS from other colorectal cancer predisposition syndromes.
Illumina NovaSeq 6000
1
EGAD00001008764
The single base substitution mutational signatures SBS2 and SBS13, likely caused by APOBEC cytosine deaminases, are common in many human cancer types. However, the stimulus activating APOBEC mutagenesis is unknown and understanding of when it occurs in the progression from normal to cancer cell is limited. Here, as part of a wider survey of human tissues, we whole genome sequenced 342 microdissected normal epithelial crypts from the small intestines of 39 individuals. SBS2/13 mutations were present in 17% normal small intestine crypts and were likely due to APOBEC3A activity. Localised clusters of SBS2/13 mutations (kataegis) were also commonly found. APOBEC mutation burdens were variable between individuals and between crypts from the same individual. Crypts with SBS2/13 often had immediate crypt neighbours without SBS2/13, suggesting that the underlying cause of SBS2/13 is cell-intrinsic rather than a widely distributed microenvironmental exposure, or needs to be permitted by cell-intrinsic conditions. APOBEC mutagenesis occurred throughout the human lifespan, including in young children, and was episodic with a small number of episodes occurring during the life history of a single cell. The results indicate that APOBEC mutagenesis is more common in the small intestine epithelium than in many other cell types, and is an episodic process in vivo initiated or permitted by cell intrinsic factors.
HiSeq X Ten
Illumina NovaSeq 6000
31
EGAD00001015471
Familial Adenomatous Polyposis (FAP) is caused by constitutional inactivating mutations in APC, the central gatekeeper gene of colorectal cancer, and is associated with a substantially increased lifetime-risk of colorectal cancer. To investigate the earliest stages of neoplastic change due to APC inactivation we microdissected and individually whole-genome sequenced 522 normal and abnormal colorectal crypts from 16 individuals with FAP. Colorectal crypts were isolated by laser capture microdissection and individually whole genome sequenced: 192 normal crypts; 34 crypts with regenerative changes; 23 crypts from 9 bifurcating crypts; 86 crypts from 17 aberrant crypt aggregates; 2 monocryptal adenomas which represent the simplest dysplastic crypt structures we were able to identify; 29 crypts from 9 oligocryptal adenomas; 156 crypts from 23 adenomatous polyps including 135 from 20 diminutive polyps and 21 from three large polyps.
HiSeq X Ten
Illumina NovaSeq 6000
1
EGAD00001015477
Familial Adenomatous Polyposis (FAP) is caused by constitutional inactivating mutations in APC, the central gatekeeper gene of colorectal cancer, and is associated with a substantially increased lifetime-risk of colorectal cancer. To investigate the earliest stages of neoplastic change due to APC inactivation we microdissected and individually whole-genome sequenced 522 normal and abnormal colorectal crypts from 16 individuals with FAP. Colorectal crypts were isolated by laser capture microdissection and individually whole genome sequenced: 192 normal crypts; 34 crypts with regenerative changes; 23 crypts from 9 bifurcating crypts; 86 crypts from 17 aberrant crypt aggregates; 2 monocryptal adenomas which represent the simplest dysplastic crypt structures we were able to identify; 29 crypts from 9 oligocryptal adenomas; 156 crypts from 23 adenomatous polyps including 135 from 20 diminutive polyps and 21 from three large polyps.
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