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Breast cancer is caused by complex interactions between a large number of genetic variants and our environment. The inherited component of breast cancer risk is due to a combination of rare variants in genes such as BRCA1 and BRCA2 that confer a high risk of the disease, and many genetic variants that each confer only a small risk.
The newly identified risk regions nearly double the number that are already known, thereby bringing the number of known common variants associated with breast cancer to about 180.
One in five women are in greater danger of getting breast cancer because of faults in their genes. Women are at risk of breast cancer if their mother, daughter or sister has breast cancer.
For one in five women, the errors written into their genes mean they have almost a third higher chance of getting breast cancer. An unlucky one per cent have three times the risk of the other 99 per cent of the population.
These gene changes now have the potential to be incorporated into existing models to accurately predict an individual’s risk, and to improve both prevention and early detection of the disease. The study looked at 11.8 million single-letter ‘spelling mistakes’ in women’s DNA which increase their risk of breast cancer.
The researchers discovered nine more variations affecting the gene BRCA1. In total, they have confirmed 107 genetic variants and discovered 72 new ones. The discovery allowed the team to calculate that one in ten women have a 70 per cent higher risk of getting breast cancer.
About 70 per cent of all breast cancers are fuelled by the sex hormone oestrogen and respond to hormone therapies such as tamoxifen.
Others, known as oestrogen-receptor negative, are not affected by the hormone and are more difficult to treat.
In a second study, the researchers found 10 new variants linked to these cancers, the two cancer types are biologically distinct and develop differently.
Breast cancer susceptibility is due to the effect of a large number of inherited genetic variants, each of which may only confers a slight increase in breast cancer risk, when the strongly predisposing genes such as BRCA1 and BRCA2 are not considered.
The study discovered 65 new variants, some of which are common, have each of which has only a small effect on breast cancer risk, but cumulatively they could be very important in altering a woman’s risk of breast cancer.
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