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Strong Support

In colorectal cancers infected with bacteria that produce colibactin, a specific pattern of DNA damage caused by this toxin accounts for about one-quarter of harmful mutations in the APC gene, which is known to initiate tumor development.

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Evidence from Studies

Supporting (1)

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Community contributions welcome

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Geographic and age variations in mutational processes in colorectal cancer

Cross-Sectional Study
Human
2025 Jul

This study found that a toxin made by certain gut bacteria leaves a specific fingerprint in the DNA of colon cancers, and about one in four of the harmful DNA mistakes that start these cancers come from that toxin. So yes, the bacteria are directly linked to causing early changes that lead to colon cancer.

Contradicting (0)

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No contradicting evidence found

Gold Standard Evidence Needed

According to GRADE and EBM methodology, here is what ideal scientific evidence would look like to definitively prove or disprove this specific claim, ordered from strongest to weakest evidence.

Source Study

Geographic and age variations in mutational processes in colorectal cancer

Score: 48
DOI: 10.1038/s41586-025-09025-8

Science Topic

Does colibactin cause APC gene mutations in colorectal cancer?

Supported
Colibactin & APC Mutations

We analyzed the available evidence and found that in colorectal cancers infected with bacteria producing colibactin, this toxin is linked to a specific pattern of DNA damage that appears in about one-quarter of harmful mutations in the APC gene [1]. The APC gene plays a key role in controlling cell growth, and when it’s damaged, it can contribute to the early stages of tumor formation. What we’ve found so far is that colibactin’s signature damage matches up with these mutations in a consistent way across the studies reviewed. There are no studies in our analysis that contradict this link. The evidence we’ve reviewed leans toward colibactin playing a measurable role in shaping these particular genetic changes. However, we cannot say this is the only way APC mutations occur, or that colibactin always leads to cancer. The data shows a pattern, not a guaranteed cause. This suggests that if someone has colorectal cancer and their tumor carries this specific DNA damage pattern, it may be worth considering whether colibactin-producing bacteria were involved. But many other factors — like diet, genetics, and lifestyle — also influence cancer development. For now, this connection remains one piece of a much larger puzzle.

2 items of evidenceView full answer

Similar Assertions

Certain strains of E. coli that produce colibactin are linked to distinct patterns of DNA damage found in colorectal tumors, particularly in younger patients, and these damage patterns are found in a portion of the mutations that drive tumor development.

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Researchers found that DNA damage patterns linked to a specific bacterial toxin were present in 39% of colorectal tumors from individuals with APC gene variants, compared to 11% in individuals without these tumors. This suggests a statistical relationship between the bacterial toxin and the type of DNA damage observed in these cancers.

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DNA damage caused by the bacterial toxin colibactin is found in the earliest genetic changes in colorectal cancer, suggesting that exposure to this toxin happens early in life and helps create the initial mutations that lead to cancer.

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Colorectal cancers with colibactin-related DNA damage patterns show the same levels of overall mutations and known cancer-causing gene changes as other colorectal cancers, suggesting colibactin causes cancer through a different biological mechanism.

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Colorectal cancers diagnosed before age 40 are more likely to show specific DNA damage patterns linked to colibactin-producing bacteria than cancers diagnosed after age 70, suggesting that exposure to these bacteria earlier in life may be associated with faster development of tumors in the lower colon and rectum.

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