Families Against Cancer & Toxics

• First proven case of cells crossing placental barrier.
• Discovery hailed as vital to research into the disease.

Sarah Boseley


Scientists have found that cancer can be passed from mother to foetus.

Scientists have established beyond doubt that in rare cases cancer can be
transmitted in the womb, following the birth of a baby to a woman with
leukaemia.

A team at the Institute of Cancer Research, a college of the University of
London, working with colleagues in Japan, found that the cancer had defied
accepted theories of biology. Leukaemia cells had crossed the placenta and
spread from the 28-year-old mother to her unborn baby.

There have been suspicions for years that cancer could be passed on in the
womb. About 17 cases of suspected mother-to-child transmission have been
noted – usually leukaemia or melanoma. But until now researchers have been
unable to establish whether it had happened and, if so, how.

If the cells did cross the placental barrier, the child's immune system should
have recognised them as foreign invaders and destroyed them.

In the latest case no one knew the mother, who was Japanese, had cancer during her pregnancy. She had a normal delivery in hospital, giving birth to an
apparently healthy baby girl.

But just over a month later the mother developed vaginal bleeding, which
became uncontrollable. She was diagnosed with an advanced stage of leukaemia and died.

When the baby was 11 months old she was brought to hospital with a swollen
right cheek. Tests showed she had a tumour in her jaw and the cancer had
spread to her lungs.

Although the cancers were not the same – the baby had a lymphoma and is now in remission – the Japanese doctors suspected a link to the leukaemia that had
killed her mother.

They called in the team at the Institute of Cancer Research, which has done a
lot of work in recent years on the genetics of cancers of identical twins. In
the journal Proceedings of the National Academy of Sciences, the researchers
explain how they used genetic "fingerprinting" techniques to establish that
the child's cancer cells came from the mother.

They found the cancer cells of mother and baby carried the identical mutated
cancer gene (called BCR-ABL1), but the infant had not inherited this gene.
This meant that the child could not have developed the cancer in isolation –
the cells must have come from the mother.

To investigate how leukaemia cells could have crossed the placental barrier
and survived in the baby, the scientists looked for evidence of some form of
immunological acceptance or tolerance of the foreign cells by the foetus.

They examined the genes of the cancer cells in the infant and found a
deletion mutation – some DNA missing in the region that controls expression
of the major histocompatibility locus (HLA).

This was significant because HLA molecules primarily distinguish one
individual, and his or her cells, from another, so the absence of these on
the cancer cells meant the infant's immune system would not have recognised
that they were foreign.

Professor Mel Greaves, who led the study, said: "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 foetus and succeeded in
implanting because they were invisible to the immune system. We are pleased
to have resolved this longstanding puzzle.

"But we stress … the chances of any pregnant woman with cancer passing it on
to her child are remote."

Dr David Grant, scientific director at Leukaemia Research, said: "The
important message from this … is that leukaemia cells can be destroyed by the
immune system. Harnessing the power of the immune system to cure and protect patients from leukaemia is one of our priority areas of research."