Many women who have had children carry fetal cells with Y chromosomes (male chromosomes) in their bloodstreams for many years, and the presence of these have been linked with breast cancer, as well as with some autoimmune disorders. New research published in the European Journal of Cancer shows that these cells can mark a lower chance of breast cancer, but the flip side is that they could also signal a higher risk of colon cancer.
The researchers looked at blood samples from women who were between the ages of 50 and 64 that had no signs of cancer from 1993 to 1997, when they took part in the diet, cancer and health cohort study in Denmark. They tracked the women's cancer status 10 years on by looking at the Danish breast and colon cancer registries.
Of the women who were cancer-free, 70% had signs of the Y-chromosome-bearing cells (known as male microchimerism) in their blood. In the women who went on to develop breast cancer, 40% had levels of the cells in their blood, as did 90% of women who developed colon cancer. The levels of cells had an influence--women with the lowest levels of fetal cells were 70% less likely to go on to get breast cancer, and women with the highest levels had a four-fold increased risk of colon cancer.
According to senior author Vijayakrishna K. Gadi of the Fred Hutchinson Cancer Research Center, the colon cancer finding was unexpected; no prior studies had ever associated that cancer with fetal microchimerism. Screening for these cells could be used to select those women who should be screened more closely for colon cancer, and further research could find out whether the cells can be linked with other tumors.
An additional outcome of this study is that there was no obvious link between live born sons and male microchimerism--in fact, around 65% of women with no live-born sons tested positive for Y-chromosome fetal cells, which could suggest miscarriages of male fetuses, including those so early that the woman did not realize that she was pregnant, leave a trace in the mothers' blood, and would mean that the screening tool could still be of use in women who have no sons.
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- see the abstract