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Mayo-led study finds smoking related to subset of colorectal cancers 

Smoking puts older women at significant risk for loss of DNA repair proteins that are critical for defending against development of some colorectal cancers, according to research from a team led by Mayo Clinic scientists.

In a study being presented at the annual meeting of the American Association for Cancer Research (AACR), the researchers found that women who smoked were at increased risk for developing colorectal tumors that lacked some or all of four proteins, known as DNA mismatch repair (MMR) proteins. These proteins keep cells lining the colon and rectum healthy because they recognize and repair genetic damage as well as mistakes that occur during cell division.

Researchers believe that, in this study population, few if any of the four proteins were absent because of an inherited genetic alteration. "We think that smoking induces a condition within intestinal cells that does not allow MMR genes to express their associated proteins, and this loss leads to formation of tumors in some women," says the study's lead author, Mayo gastroenterologist Paul Limburg, M.D.

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