In two studies, published in the September 20, 2002, issue of the journal Science, collaborative teams of scientists present evidence that a mutation in one of two copies of the Bloom syndrome gene (BLM) is sufficient to raise the risk of cancer in mice and humans. The results are the first to show that being a carrier of a recessive cancer syndrome gene can raise the risk of cancer, even if that individual does not have the disease itself.

"The findings remind us that knowing your family history of disease is very important," said Howard Hughes Medical Institute investigator Joanna Groden, who led the team that conducted the experiments in mice. "Even cancers that we think of as common and age-related can have a hereditary component."

In the case of Bloom syndrome, people who have two defective copies of the BLM gene are generally of short stature and have a variety of physical defects and a predisposition to developing many types of cancer. Bloom syndrome occurs in all ethnic populations, but it is more common in Jewish people of European descent (Ashkenazi Jews).

The BLM protein plays a role in helping ensure that chromosomes are copied properly during cell division. When the BLM protein is defective or missing, cells are more likely to acquire or keep DNA-copying errors that result in mutation. The chromosomes in cells without BLM also may have trouble getting untangled during cell division, sometimes causing pieces of chromosomes to break off.

Groden and her colleagues at the University of Cincinnati conducted a series of experiments in mice that were engineered to carry a single copy of the mutant Blm gene. These mice, which also had one normal copy of the
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Contact: Jim Keeley
keeleyj@hhmi.org
301-215-8858
Howard Hughes Medical Institute
19-Sep-2002