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Scientists discover new 'breast cancer' genes

An international study has found four mutations that may increase a woman's risk of breast cancer.

Jo Carlowe

Tuesday, 29 May 2007

A large scale genetic study, spanning 15 countries, has found four new genes that appear to significantly raise a woman's risk of getting breast cancer.

The four genes are called FGFR2, TNRC9, MAP3K1 and LSP1. It is hoped the discovery will help doctors improve their prediction of breast cancer risk and select better treatments to prevent and cure the disease.

However, speaking to OnMedica, Dr Paul Pharoah, of the University of Cambridge, Cancer Research UK Senior Clinical Research fellow, who was involved in the research, said the findings were 'only a part of the jigsaw'.

Until this new research, scientists could only account for around 25 per cent of the genetic part of breast cancer risk. They suspected that the residual genetic variance was likely due to a range of different gene mutations, but had 'no inkling' that these particular genes had anything to do with breast cancer

To look for further mutations, Pharoah and colleagues conducted a two-stage genome-wide association study in nearly 4,400 women with breast cancer and a similar number of controls. They then confirmed 30 suspected single nucleotide polymorphisms (SNPs) in nearly 22,000 women with breast cancer and a similar number of controls spanning 22 studies.

Overall they looked at over 225,000 SNPs and discovered that five in until now unknown loci in the genome showed strong and consistent links with breast cancer incidence. Four of these were found to be the most plausible: FGFR2, TNRC9, MAP3K1 and LSP1. The gene whose variants appears to confer the greatest risk of the four is fibroblast growth factor receptor 2, or FGFR2.

Women who have two copies of the high risk variants of this gene, estimated to be about 16 per cent of the female population, have a 60 per cent greater chance of getting breast cancer compared with women who have none.

Dr Pharoah believes more high risk variants will be found over the next three to five years but thinks it will be at least 10 years before this knowledge can be put to clinical use. He is aware that patients may ask GPs about screening for the new genes, and suggests GPs use the jigsaw analogy to help patients understand the current limitations.

"You could say BRCA1 makes up 10 per cent of the jigsaw, BRCA2 another 10 per cent, and the five we have discovered account for about 2 per cent, 1 per cent, and 0.5 per cent each."

He suggests at 'least half' of the puzzle needs to be completed before doctors will be able to scan women and tell them what their breast cancer risk is likely to be.

"On their own these findings will not have any clinical significance but as more and more similar genes are discovered - say about 30 or 40 of these genes - then it may be possible to put them together into a single test."

The study, conducted from Australia, Denmark, Finland, France, Germany, Korea, The Netherlands, New Zealand, Poland, Singapore, Sweden, Taiwan, Thailand, the UK and the US, is published in the early online edition of the journal Nature.

Two other studies - one from the US and one led from Iceland, reported in Nature Genetics, have also discovered genetic variants that appear to increase the risk of breast cancer.

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