Fetal Cells Protect Against Breast Cancer

[October 2007] October is Breast Cancer Awareness Month and a well-known risk factor for breast cancer has just received validation.

Not having children is often cited as a risk factor in the development of cancer. According to the American Cancer Society (ACS), women who have had no children or who had their first child after age 30, have a slightly higher breast cancer risk. Having multiple pregnancies and becoming pregnant at an early age also seems to reduce breast cancer risk.

Child-Bearing Women Have Less Risk for Breast Cancer

Some benefits of motherhood are intangible, but one has been validated through biostatistical research. Women who bear children have a reduced risk of developing breast cancer. Researchers at the University of Washington and Fred Hutchinson Cancer Research Center believe they have identified a source of this protective effect - fetal cells taking up residence in the mother before birth.

Their findings are presented in Cancer Research, a journal of the American Association for Cancer Research (AACR).

Male DNA Found in the Mothers

To test the idea, the researchers recruited 82 women, 35 of whom had been diagnosed with breast cancer. Approximately two-thirds of the women studied had given birth and more than half of the participants had given birth to at least one son.

The researchers took blood samples from each participant and searched them for male DNA. The rationale for this is that it is a relatively definitive matter to detect the male Y chromosome amid the mother’s native - and obviously female - cells within a blood sample.

Among the women with breast cancer, only five had male DNA in their bloodstream. Three of the five previously gave birth to sons, one had had an abortion and the other had never been knowingly pregnant.

In total, about 14 percent of all women in the breast cancer group had male DNA in their bloodstream compared to 43 percent of women in the non-breast cancer group.

"Our research found that these persisting fetal cells may be giving a woman an edge against breast cancer," says Dr. Vijayakrishna K. Gadi, assistant professor at the University of Washington and research associate at the Fred Hutchinson Cancer Research Center. "This experiment of nature is all the more fascinating because for years doctors treated a number of different cancers by transplanting cells from one person to another."

How Baby's Cells Affect Moms

The ability of cells from a growing fetus to take up long-term residence within its mother is a phenomenon called fetal microchimerism.

According to the researchers, while fetal microchimerism has been implicated as a mechanism of autoimmune disease, it may also benefit mothers by putting the immune system on alert for malignant cells to destroy.

Future Research May Help Prevent Cancer

According to Dr. Gadi, these findings could provide a starting point for future research on the role of fetal microchimerism in the prevention of cancer.

In addition, there are other reasons for male DNA to be in a woman’s peripheral blood, reasons such as miscarriage and abortion – or possibly even blood transfusion or a male twin that was reabsorbed into the womb at an early stage of the pregnancy. Hopefully researchers will be able to find a way to use this information to prevent breast cancer in women who do not have children.

If you have concerns about your breast cancer risk, consult your physician for more information.