Genes May Explain Role of Race in Colon Cancer Risk

Differences in a key piece of DNA seem important, scientists say

WEDNESDAY, Nov. 28 (HealthDay News) -- Genes may contribute to disparities in colorectal cancer rates between ethnic and racial groups, a new U.S. review suggests.

The research team, led by investigators at the University of Pittsburgh, analyzed 26 studies that included more than 25,000 people.

They found that people who have two "T" copies of the MTHFR gene that metabolizes folate -- a chemical needed to produce and maintain new cells -- are 19 percent less likely to develop colorectal cancer than people with two "C" copies of the gene.

When they looked at specific racial/ethnic groups, the reviewers found that the risk of colorectal cancer in people with the two "T" copies, compared to those with the two "C" copies, was 31 percent less in Asians, 8 percent less in whites, and 4 percent less in black Americans.

They also found that Hispanics who had one "T" copy and one "C" copy of the gene were 20 percent more likely to develop colorectal cancer than Hispanics with two "C" copies of the gene. However, the researchers said this finding was not statistically significant.

The results of the analysis were to be presented Wednesday at the American Association for Cancer Research's conference on The Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved, in Atlanta.

The study shows that two copies of the "T" version of the gene "may be protective in different degrees against colorectal cancer in some populations but not in others," lead investigator Mary A. Garza, deputy director of the Center for Minority Health in the University of Pittsburgh's Graduate School of Public Health, said in a prepared statement.

The finding that two "T" copies of the MTHFR gene may help protect against colorectal cancer in certain racial/ethnic groups warrants further study, she said.

This is the first pooled analysis to examine the association between specific genes and the risk of developing colorectal cancer in racial/ethnic groups, according to Garza.

"We are trying to unlock the role genetics, through gene-environment interactions, may play in understanding the underlying causes of health disparities," she said.

Overall, colorectal cancer death rates in the United States have been declining, but blacks and other minorities account for a disproportionate share of colorectal cancer patients.

"This disparity exists even after accounting for various environmental and social factors, so it makes sense that genetics could play a contributing role in this cancer disparity," Garza said.

More information

The U.S. National Cancer Institute has more about colorectal cancer risk.

SOURCE: American Association for Cancer Research, news release, Nov. 28, 2007
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