US colon cancer gene traced to early settlers

A couple who sailed to America from England around 1630 took with
them a gene that has put their thousands of descendants at an
increased risk of colon cancer.

An American team traced back a mutation found in two large families
living in Utah and New York to a couple who were among the early
settlers of America.

The team, from the Huntsman Cancer Institute in Utah, did not name
the families but said thousands of people across the country may have
the mutation that spread widely as the couple's descendants branched
apart over many generations.

"The fact that this mutation can be traced so far back in time
suggests it could be carried by many more families in the United
States than is currently known," said Deb Neklason, who led the
study. "In fact, this founder mutation might be related to many colon
cancer cases in the United States."

The study did not investigate whether the same mutation may also be
responsible for colon cancers in the UK, but that appears possible.

Less than 1 per cent of cases in the US are due to this particular
genetic mutation, according to the study published in Clinical
Gastroenterology and Hepatology.

The team first focused on the Utah branch of the family, which
numbers about 5,000 people, 14 years ago because its members had an
unusually high risk of colon cancer.

The Mormon faith of the family meant the researchers were able to
mine a wealth of genealogical information taken from detailed church
records over the years that is now part of a large genetics database
in Utah, Neklason said.

While most of the records in the study related to the Utah part of
the family, the researchers eventually identified the New York branch
as well.

"We just know about these two branches of the family," Neklason
said. "The significance of it going so far back is there are probably
many branches of the family out there that aren't aware of the
mutation."

In the study, the team identified the mutation that causes a
condition called attenuated familial adenomatous polyposis (AFAP),
which makes people more prone to developing the polyps that can cause
colon cancer.

Without proper treatment, people with this mutation have a greater
than 2 in 3 risk of developing colon cancer by age 80, compared to
about 1 in 24 for the general population. Early treatment, however,
can just about eliminate this risk.

"This study highlights that you need to pay attention to your family
history," Neklason said."With intervention to remove the polyps, the
risk goes to near nothing."

Colon cancer gene traced to early settlers