A striking case in Japan confirmed that pregnant women with cancer can transmit the disease to their fetuses. These transmissions normally blocked by the placenta are rare, so the work will not likely change how doctors screen or care for pregnant women. But scientists say the case could help illuminate how cancer foils the body's immune system.
In early 07, a 28-year-old Japanese woman gave birth to a daughter. Thirty-six days later, the mother was hospitalized with vaginal bleeding, which became uncontrollable. Doctors diagnosed leukemia, and she died soon. The baby developed normally until age 11 months, when a huge tumor appeared in her cheek. A biopsy determined the cancer has not been sarcoma - a cancer of some connective tissues -. But leukemic tumor somehow trapped in the cheek of the child
The doctors alerted cell biologist Mel Greaves of the Institute of Cancer Research in Sutton Surrey, UK, who studies transmissible cancers. Scientists had suspected the mother-fetus cancer in other cases with circumstantial evidence (especially leukemia and melanoma, which both metastasize easily). But nobody had done genetic tests to prove that the cancer had grown from a single source and was not just an unfortunate coincidence.
In their investigation, Greaves and his colleagues discovered incipient cancer cells in routine blood samples taken from the child at birth, which strongly suggests that transmission happened in utero. They also examined a unique DNA sequence in each case of leukemia, BCR-ABL1 sequence. It was identical to the mother and daughter. Finally, the tests showed the cancer cells of children were almost all maternal cells without genetic material from the father. This indicated that the route of transmission is from mother to fetus, and not the reverse. The team has its evidence in a paper published online October 12 in the Proceedings of the National Academy of Sciences .
Greaves and his colleagues also determined how cancer survived inside the fetus, whose immune system would destroy the cells of the mother. They found that the cancer cells are absent a large area from a section of the sixth human chromosome known under the name 6p, which produces surface markers of immune cells which bind to the. In short, Greaves said, "Cancer has succeeded because it was immunologically invisible."
Knowing the molecular details of how evaded detection cells enable scientists to probe how other cancers slide by our immune system, said Howard Weinstein, a pediatric cancer specialist at Massachusetts General Hospital in Boston.
Despite the findings, mothers should not panic, says Greaves. with only a few dozen cases of transmission of cancer mother-fetus reported since the first in 1866, the risk for pregnant women is minimal, he said, and the transfer of advanced cancer in infants are not necessarily fatal. - the Japanese girl was successfully treated and is still alive. But Greaves said his team's work challenges the assumption that the placenta is a fully effective barrier between mothers and fetuses. "I'm more inclined to think that perhaps the cells obtained by modest numbers all the time," he said. "You can learn a lot of very strange case in medicine."
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