DNA damage from certain bacteria in early childhood may lead to colorectal cancer that appears later in adulthood.

A bacterial toxin called colibactin can cause DNA damage in children, and this damage can be found as one of the earliest genetic changes in tumors that develop in the colon later in life.

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.

Colorectal cancers diagnosed before age 50 are three to four times more likely to carry a specific DNA mutation pattern linked to colibactin-producing bacteria than cancers diagnosed after age 50, indicating that exposure to these bacteria earlier in life may be linked to the increase in early-onset colorectal cancer.

Certain strains of E. coli that produce a toxin called colibactin are linked to a specific pattern of DNA damage found in colorectal tumors. This DNA damage pattern is more commonly found in tumors from people diagnosed with colorectal cancer before age 55 compared to those diagnosed at age 59 or older.

Colorectal tumors with specific DNA damage patterns caused by colibactin often do not contain the bacteria that produce it at the time of diagnosis, suggesting the bacteria were present earlier and have since been cleared.