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.
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 have had children, 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, as they reasoned 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 developing breast cancer," said lead author Vijayakrishna K. Gadi, M.D., Ph.D., 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."
"To our knowledge, the current results provide the first indication that FMc could impart a protective effect against breast cancer," Gadi said.
Prior research into FMc, some of it performed at the Hutchinson Center, indicates that while the presence of fetal cells in women may confer immune protection and promote cell repair, such cells also may be harbingers of some autoimmune diseases.
Two observations provided a rationale for the study hypothesis of the potential beneficial role of fetal cells, according to the authors. It is well established that women who have given birth have a lower risk of breast cancer. And, allogeneic (from another individual) stem-cell transplants are used to treat many types of blood cancers by replacing a diseased immune system with a healthy one
Additionally, fetal cells are commonly found in the circulating blood of healthy women who have given birth. Fetal cells represent a naturally acquired source of allogeneic immune cells; in prior studies the prevalence of T, B, natural-killer (NK) and antigen-presenting cells of fetal origin in healthy women ranged from 30 percent to 70 percent, depending on the cell type.
The research was funded by the National Institutes of Health and Amgen Inc.
The findings are published in the Oct. 1 issue of Cancer Research.
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