In a recent study, researchers found that a bacterium known for causing stomach cancer might also increase the risk of certain colorectal cancers.
The study was led by Duke Cancer Institute researchers.
It describes an association between antibodies to H. pylori bacteria and an increased risk of colorectal cancers.
In an analysis of more than 4,000 colorectal cancer cases culled from large, diverse cohort studies, the researchers found a significant correlation between colorectal cancer incidence and those who had been infected with a virulent strain of H. pylori.
The team collected data from 10 large regional and national studies, including the Southern Community Cohort Study, the Nurses Health Study, the Women’s Health Initiative and the American Cancer Society’s Cancer Prevention Study-II, among others.
They analyzed blood samples from more than 8,400 ethnically and regionally diverse study participants—half who went on to develop colorectal cancer and the other half with no such diagnosis.
The researchers found that H. pylori infections were equally common in both cancer and non-cancer group, with 4 in 10 patients in both groups testing positive for exposure to the bacterium.
But stark racial differences also appeared. White patients had below average H. pylori infection rates, and Asian Americans had average rates.
But for black and Latino patients, the rates were much higher.
Among African Americans, 65% of the non-cancer patients and 71% of the colorectal cancer patients had H. pylori antibodies; among Latinos, 77% of the non-cancer group and 74% of the cancer group had antibodies.
Further analysis showed that antibodies to four H. pylori proteins were most often present among the different ethnic groups with colorectal cancer.
One H. pylori protein, in particular, VacA, had the strongest association with increased odds of colorectal cancer among the African American patients in the study.
It was surprising to find VacA antibodies increased the odds of colorectal cancer in African Americans and Asian Americans, and not in whites and Latinos.
This is a big question—are people harboring different bacteria based on genetic origin or heritage? This is part of what the team plans to figure out.
Additional studies might also determine whether antibodies to the H. pylori VacA protein could serve as a marker of colorectal cancer risk if it isn’t causing cancer directly.
The lead author is Meira Epplein, Ph.D., co-leader of Cancer Control and Population Sciences at Duke Cancer Institute.
The study is published in the journal Gastroenterology.
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