Passing cancer from mother to baby
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Infants can inherit a lot of things from their mothers – curly hair, high cheekbones, slender fingers. And, scientists now show, cancer.
Doctors have long believed that it was possible for babies to contract cancer in utero. The medical literature includes 17 case reports going back to 1866 of maternal tumors that probably spread to their infants during pregnancy.
In some instances, the evidence was quite strong. For example, there are three known cases of baby boys with leukemia whose bone marrow cells contained two X chromosomes instead of one X and one Y. The most likely explanation for the presence of female XX cells in the boys is that they were inherited from their mothers, but other scenarios were theoretically possible.
Writing this week in the online edition of Proceedings of the National Academy of Sciences, doctors in Japan and the United Kingdom describe a 28-year-old Japanese woman who gave birth to a healthy girl after a normal, uneventful pregnancy. About one month later, she developed vaginal bleeding that soon became uncontrollable. She was diagnosed with acute lymphoblastic leukemia and began chemotherapy. However, she developed encephalitis and died 19 days later.
The baby showed no signs of illness until she was 11 months old. Her right cheek was swollen, and it turned out she had a tumor and a pleural effusion.
By comparing DNA from the mother’s bone marrow to DNA in the baby’s pleural effusion, the medical team was able to confirm that the cancers were identical, according to the study. Both patients shared a unique genetic fingerprint.
The researchers also went back and re-analyzed a neonatal blood sample that was taken from the baby girl. The results confirmed that the cancer spread to the infant before she was born.
Further testing revealed how this could have happened. Normally, the cancer cells would be unable to cross the placental barrier, which is why cases of maternal-fetal cancer transmission are so rare. But the cells from the baby’s tumor were missing a key sequence of chromosome 6 that would have included the mother’s HLA genes, which play a key role in immune system function. Without those genes, the cancer cells were able to slip right past the baby’s immune system instead of being recognized as foreign invaders, the researchers wrote.
The little girl – now about 2½ years old – was treated with chemotherapy and has been in full remission for 18 months, according to the report.
-- Karen Kaplan
