Breast Cancer Gene Altered More Often In African-American Women

P53 Gene Contains The Mutation

< August 11, 2004 > -- African-American women with breast cancer are four times more likely than Caucasian women with breast cancer to have mutations in a gene known to help suppress tumors, according to a report in the medical journal Cancer.

The mutations occur in a well-studied gene called p53. When the p53 gene is suppressed, breast cancer is often more aggressive.

"P53 tumor mutations have for several years been known to be associated with a poor prognosis for breast cancer," says study author Dr. Beth A. Jones, an assistant professor of epidemiology at the Yale University School of Medicine.

"But this is the first population-based study that shows a clearly significant race difference in p53 tumor mutations, once you adjust for other factors such as tumor stage," Dr. Jones adds.

P53 Gene Stands Out Over Others Tested

Dr. Jones and her team evaluated the breast tumors of 145 African-American women and 177 Caucasian women, looking for differences in the p53 gene. Although they found African-American women were more likely to have p53 gene mutations, they did not find significant differences by race in any other cancer-related genes.

In the study, 24.5 percent of the African-American women had a p53 mutation, compared to 7.1 percent of the Caucasian women.

"Overall, the rates of breast cancer in African-American women are slightly lower than in white women," Dr. Jones says, "but the death rate from breast cancer in African-American women is slightly higher than in white women."

Discoveries of racial differences in genetic alterations such as the p53 gene mutation may explain why.

In an editorial accompanying the study in Cancer, Dr. Lisa A. Newman, director of the Breast Care Center at the University of Michigan, notes the largest magnitude of difference in outcomes for breast cancer within the US have been observed between African-American women and Caucasian women.

For those under the age of 45, the incidence of breast cancer is higher in African-American women than in Caucasian women, Newman writes.

"Numerous studies, for at least 50 years, have been showing that African-American women are more likely to die from breast cancer than white American women, " Dr. Newman says.

But researchers, she says, have never been able to sort out conclusively whether that is due to socioeconomic factors, poorer access to screening, diagnosis at an advanced stage, or other factors.

"Studies like this that look at some of the biological enhancers help us to figure out whether some women are more likely to develop inherently more aggressive tumors," Dr. Newman says.

Future May Hold Specialized Testing

Dr. Denise Johnson, associate professor of surgery at Stanford University Medical Center, and a member of the African-American Outreach Committee for the American Cancer Society, praised the study.

"It isn't the first study on the topic, but it is the largest," she says.

Eventually, Dr. Johnson says, the finding may provide more tools to determine the outlook for a woman with breast cancer, especially if she has the gene mutation.

Still, Dr. Johnson explains that more study is needed. If the finding holds up, she adds, perhaps a recommendation will someday be made to analyze the presence or absence of the p53 gene mutation in all women.

Always consult your physician for more information.

Online Resources

American Cancer Society

American Society of Clinical Oncology

Centers for Disease Control and Prevention (CDC)

HealthierUS.Gov

National Cancer Institute

National Institutes of Health (NIH)

National Library of Medicine

National Women's Health Information Center

Susan G. Komen Breast Cancer Foundation

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ACS Explains Breast Cancer Genetic Risks

According to the American Cancer Society (ACS), although some of the risk factors that increase a woman's chance of developing breast cancer are known, it is not yet known what causes most breast cancers or exactly how some of these risk factors cause cells to become cancerous.

The ACS states that "we know that a woman’s hormones somehow stimulate breast cancer growth. Just how this comes about has not yet been worked out."

Another area is understanding how certain changes in DNA can cause normal breast cells to become cancerous. DNA is the chemical that carries the instructions for nearly everything our cells do. We usually resemble our parents because they are the source of our DNA. However, DNA affects more than our outward appearance, the ACS explains.

Some genes (parts of DNA) contain instructions for controlling when our cells grow, divide, and die. Certain genes that promote cell division are called oncogenes.

Others that slow down cell division, or cause cells to die at the right time, are called tumor suppressor genes. It is known that cancers can be caused by DNA mutations (changes) that "turn on" oncogenes or "turn off" tumor suppressor genes.

The BRCA gene is a tumor suppressor gene. When it is mutated, it no longer functions to suppress abnormal growth and cancer is more likely to develop. Certain inherited DNA changes can cause a high risk for developing cancer in people who carry these changes and are responsible for the cancers that run in some families.

Most DNA mutations related to breast cancer, however, occur in single breast cells during a woman's life rather than having been inherited.

Acquired mutations of oncogenes and/or tumor suppressor genes may result from radiation or cancer-causing chemicals.

So far, however, studies have not been able to identify any chemical in the environment or in our diets that is likely to cause these mutations, or a subsequent breast cancer. The cause of most acquired mutations remains unknown.

Women have already begun to benefit in several ways from recent advances in understanding the genetic basis of breast cancer.

The ACS states that genetic testing can identify some women who have inherited abnormal BRCA1, BRCA2, or p53 tumor suppressor genes. These women can then take steps to reduce their risk of developing breast cancers and to monitor changes in their breasts carefully to find cancer at an earlier, more treatable stage.

Most breast cancers have several gene mutations. The mutations are not inherited and cannot be passed on, but instead they develop during a woman's lifetime.

Tests to identify other acquired changes in oncogenes or tumor suppressor genes (such as p53) may help doctors more accurately predict the survival outcome of some women with breast cancer.

But, with the exception of the HER2 oncogene, these tests have not yet been shown to be useful in making decisions about treatment and are used only for research purposes.

Always consult your physician for more information.