Dataset Information

Mutational signature in colorectal cancer induced by genotoxic pks+ E. coli

ABSTRACT: Various species of the intestinal microbiota have been associated with the development of colorectal cancer (CRC), yet a direct role of bacteria in the occurrence of oncogenic mutations has not been established. Escherichia coli can carry the pathogenicity island pks, which encodes a set of enzymes that synthesize colibactin. This compound alkylates DNA on adenine residues and induces double strand breaks in cultured cells. Here, we exposed human intestinal organoids to genotoxic pks+ Escherichia coli by repeated luminal injection over a period of 5 months. Whole genome sequencing (WGS) of clonal organoids before and after this exposure reveals a distinct mutational signature, absent from organoids injected with isogenic pks-mutant bacteria. The same mutational signature is detected in a subset of 3668 human metastatic cancer genomes, predominantly in a subset of CRC cases. Our study describes a distinct mutational signature in CRC and implies that the underlying mutational process directly results from past exposure to bacteria carrying the colibactin-producing pks pathogenicity island.

PROVIDER: EGAS00001003934 | EGA |

REPOSITORIES: EGA

ACCESS DATA

Similar Datasets

Project description:In Rspondin-based three-dimensional cultures, Lgr5 stem cells from multiple organs form ever-expanding epithelial organoids that retain their tissue identity. Here we report the establishment of tumor organoid cultures from 20 consecutive colorectal carcinoma (CRC) patients. For most, organoids were also generated from adjacent normal tissue. Organoids closely resemble the original tumor. The spectrum of genetic changes within the 'living biobank' agrees well with previous large-scale mutational analyses of CRC. Gene expression analysis indicates that the major CRC molecular subtypes are represented. Tumor organoids are amenable to high-throughput drug screens allowing detection of gene-drug associations. As an example, a single organoid culture was exquisitely sensitive to Wnt secretion (porcupine) inhibitors and carried a mutation in the negative Wnt feedback regulator RNF43, rather than in APC. Organoid technology may fill the gap between cancer genetics and patient trials, complement cell line- and xenograft-based drug studies and allow personalized therapy design. Self-renewal of the intestinal epithelium is driven by Lgr5 stem cells located in crypts. We have recently developed a long-term culture system that maintains basic crypt physiology. Wnt signals are required for the maintenance of active crypt stem cells. Indeed, the Wnt agonist R-spondin1 induces dramatic crypt hyperplasia in vivo. R-spondin-1 is the ligand for Lgr5. Epidermal growth factor (EGF) signaling is associated with intestinal proliferation, while transgenic expression of Noggin induces a dramatic increase in crypt numbers. The combination of R-spondin-1, EGF, and Noggin in Matrigel sustains ever-expanding small intestinal organoids, which display all hallmarks of the original tissue in terms of architecture, cell type composition, and self-renewal dynamics. We adapted the culture condition for long-term expansion of human colonic epithelium and primary colonic adenocarcinoma, by adding nicotinamide, A83-01 (Alk inhibitor), Prostaglandin E2 and the p38 inhibitor SB202190. Of note, a two-dimensional culture method for cells from normal and malignant primary tissue has been described by Schlegel and colleagues. Here, we explore organoid technology to routinely establish and phenotypically annotate ‘paired organoids’ derived from adjacent tumor and healthy epithelium from CRC patients.

Project description:Regeneration capacity of intestinal epithelial cells are highly dependent on the status of stemness. In the homeostasis, only a small subset of stem cells is responsible for the turnover of the intestinal epithelium. However, at the injury, such as caused by radiation, intestinal epithelial cells show substantial plasticity for regeneration. Most of the colorectal cancers (CRCs) are differentiated adenocarcinoma, which maintain the expression of both stemness and differentiation markers, suggesting an existence of a similar regeneration system as in normal cells, although the role of such fluctuation of stemness in regeneration of cancer after irradiation is not well understood. In the present study, we first examined the effect of radiation on growth, stemness and differentiation using organoids derived from differentiated CRC. Both proliferation and stemness markers were once drastically decreased after sub-lethal dose of irradiation, meanwhile differentiation markers remained. After the static phase, regrowth foci consisting of proliferating cells with expression of the stem cell markers reappeared. We applied the foci formation to a radio-sensitivity assay in CRC organoids. Radio-sensitivity, the ability of foci formation, differed among the examined lines, and correlated well with the in vivo radiation sensitivity. The radio-sensitivity decreased after mechanical disruption of the organoids, which we have reported to increase the stemness of CRC organoids in a WNT dependent manner. Pre-treatment of organoids with histone deacetylase inhibitors increased radiation sensitivity, accompanied with suppressed expression of WNT target genes, and WNT inhibitors increased radio-sensitivity, suggesting that not all but some of the cancer cells with high WNT activity at the timing of radiation is the origin of the foci formation. The radiation sensitivity assay using CRC organoids established in the present study would provide a novel platform to evaluate the radiosensitizers against differentiated adenocarcinoma of CRC.

Dataset Information

Mutational signature in colorectal cancer induced by genotoxic pks+ E. coli

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure