Researchers have found new evidence that it's possible for a pregnant mother with some forms of cancer to pass the disease on to her unborn child.
In theory, it's been thought that a child's immune system and the placenta should block the spread of cancer from mother to fetus. But there have been rare cases of babies being diagnosed with the same cancers that have afflicted their mothers, usually leukemia or melanoma.
In this latest case, a British-led team, reporting in the Proceedings of the National Academy of Sciences, looked at the case of a Japanese woman who was diagnosed with leukemia shortly after giving birth; her daughter then developed a similar type of cancer at the age of 11 months.
Researchers performed genetic testing on the cancer cells in both the mother and the baby and found that the daughter's cancer cells shared a unique genetic match to her mother's.
They found both patients' leukemic cells carried the same mutated cancer gene (called BCR-ABL1), but while the mother had the gene, the infant had not inherited that gene. That meant the child could not have developed this type of leukemia on her own.
While previous cases of mothers' cancers being diagnosed in their babies have been reported over the years, until now, the possibility that cancer cells may be passed from mother to infant had not been confirmed genetically.
Additional testing showed that the infant's cancer cells lacked a portion of genetic material that would have flagged the cancer as intruder cells and targeted them for elimination by her immune system.
Researcher Takeshi Isoda of Tokyo Medical and Dental University and colleagues say this genetic trait likely enabled the mother's cancer cells to evade the infant's protective placental barrier.
Lead researcher Professor Mel Greaves of the Institute of Cancer Research, said in a statement: "It appears that in this and, we presume other cases of mother-to-offspring cancer, the maternal cancer cells did cross the placenta into the developing fetus and succeeded in implanting because they were invisible to the immune system.
"We are pleased to have resolved this longstanding puzzle. But we stress that such mother-to-offspring transfer of cancer is exceedingly rare and the chances of any pregnant woman with cancer passing it on to her child are remote."
