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World-first study of faulty genes for breast cancer

Monday 28 May, 2007

Cancer Council epidemiological researcher Graham Giles is part of an international team that recently published results of a world-first large-scale study of faulty genes and breast cancer.

The results have been published in Nature.

Researchers at Cambridge University brought together an international team in the world's first large-scale ‘whole genome search' for faulty genes for breast cancer. The study involved the analysis of DNA from nearly 50,000 women worldwide.

The hunt for genes that cause familial breast cancer has been a challenge. it has been known for over a decade that women who carry rare mutations in genes such as BRCA1 and BRCA2 are at very high risk of breast cancer, but these account for less than 25 % of all familial breast cancers.

It has long been suspected, therefore, that there must also exist some very common genetic faults that only increase breast cancer risk by a small amount.

The international study shows that if a woman carries one faulty copy of one of these low risk genes, her risk of getting breast cancer might increase by about 20 percent but if she carries two faulty copies, her risk increases by between 40 and 60 percent.

According to the Cambridge researchers, the increased risks associated with the common faulty low-risk genes found in this study are relatively small and would not be suitable for genetic testing. But as more of these low risk genes are found, it may be possible to design tests for a combination of genes.

Three Australian research groups contributed to the study including the University of Melbourne, The Cancer Council Victoria and KConFab.

Genetic epidemiology studies led in the third stage of the international study by Professor John Hopper (School of Population Health) and Associate Professor Melissa Southey (Department of Pathology) and Professor Graham Giles, (School of Population Health and The Cancer Council Victoria) have been critical to the identification and characterisation of these common low risk mutations in these genes.

The involvement of the Australian studies of women in the general population (the Australian Breast Cancer Family Study and The Melbourne Collaborative Cohort Study) may lead to new information with wide relevance to breast cancer control.

"This research discovery is a step towards explaining genetic influences on breast cancer risk, not just for women with a family history of breast cancer but also for the majority of women in the general population," said Professor John Hopper of the University of Melbourne's School of Population Health, a co-author of the paper.

"Their discovery will promote new research efforts to further our understanding of biological mechanisms," said Professor Graham Giles, an honorary professorial fellow in the School of Population Health and Director of the Cancer Epidemiology Centre at The Cancer Council Victoria.

The Australian Breast Cancer Family Study led by Professor John Hopper contributed genotype data from 1485 women with breast cancer and 839controls. 

The Melbourne Collaborative Cohort Study led by Professor Graham Giles contributed genotype data from 519 women with breast cancer and 578 controls.

KConFab contributed genotype data from 387 women with breast cancer.

Professor Giles said a future step would be to investigate other factors that contribute to the risk associated with these common genetic variants, such as interactions with other genes and with environment and lifestyle factors.

"These factors are much harder to measure than genotypes and again we will need an enormous international effort and population studies probably in excess of 100,000 people."

View more information from Nature


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