Inheriting the wrong version of a gene called CHEK2 doubles a woman's risk of developing breast cancer, Cancer Research UK scientists confirm in a major new international study published in the American Journal of Human Genetics.
CHEK2 is the first 'low risk' gene to have been definitely established as a risk factor. It follows the identification in the mid-nineties of the high-risk genes, BRCA1 and BRCA2. The possibility of offering genetic testing for this gene in women with a strong family history of breast cancer is now being researched.
The link between CHEK2 and breast cancer was first proposed in 2002, when a faulty version of the gene was found to be present in some cases with a strong family history of breast cancer. 'Strong family history' indicates at least two close family members have had the disease.
This new research, coordinated and analyzed by Cancer Research UK's Genetic Epidemiology Unit at the University of Cambridge, examined the genes of breast cancer patients and the wider population in the UK, Australia, Finland, Germany and the Netherlands.
The report confirms that the faulty version of the gene, called CHEK2*1100delC, was more common in women diagnosed with breast cancer than in healthy women. In total, they examined the CHEK2 genes of 10,860 women with breast cancer and 9,065 healthy women.
The 1100delC variant was found in 201 women with breast cancer (1.9%) and in 64 healthy individuals (0.7%). Scientists calculate from this that having the variant CHEK2 gene approximately doubles the risk of developing breast cancer, whether or not there is a history of breast cancer in the family.
CHEK2*1100delC is only found in about 2% of all breast cancer patients, which is why general testing would be impractical. For women with a strong family history of breast cancer, however, screening for the variant would help in assessing each woman's individual risk.
Lead researcher Professor Doug Easton, of the Cancer Research UK Genetic Epidemiology Unit, says: "As we identify more genes that impact on hereditary breast cancer, we move closer to a comprehensive genetic test to accurately assess the risk of inheriting the disease."
SOURCES:
American Journal of Human Genetics, June 2004
Cancer Research UK (http://www.cancerresearchuk.org)
