Doctors from the Imperial Cancer Research Fund, London, England have taken a step closer to identifying people who should be screened for bowel cancer. In new findings published this month (September 1998) in the Proceedings of the National Academy of Sciences* the research team confirm that two variants of the APC gene (a gene already associated with familial bowel cancer) do make people more susceptible to developing pre-cancerous polyps and thus predisposes them to bowel cancer.
Sir Walter Bodmer, head of the charity's Cancer and Immunogenetics Laboratory, Oxford explained: "We have found a new category of susceptibility to bowel cancer. What is interesting about these variants is that although they are hereditary their effect is not so strong as the other mutations which have already been identified with familial bowel cancer."
Dr Ian Frayling, Clincial Research Fellow with Imperial Cancer's Bowel Cancer Unit at St Mark's Hospital, added: "Not everyone who carries these variants of the APC gene will develop bowel cancer and so someone who carries the gene won't necessarily have a family history of the disease, but they might be at an increased risk of bowel cancer nonetheless."
Inherited mutations in the APC gene are responsible for a condition called Familial Adenomatous Polyposis (FAP) in which gene carriers get hundreds, often thousands, of polyps in their bowel and if the condition is not treated by surgery bowel cancer will develop. FAP is very rare (1 in 8000 individuals), but accounts for about one half a per cent of bowel cancer.
Added Dr Ian Tomlinson, head of Imperial Cancer's Molecular and Population
Genetics Laboratory: "These new variants have a much more subtle effect and
could be more common than the ones responsible for FAP. Someone who carries a
standard APC gene mutation will have a risk of bowel cancer 40 times higher
than normal. The risk for someone with one of these weaker variants may only be
5 times normal."
Contact: Christine Suggars
Imperial Cancer Research Fund