Cancer gene linked to increased fertility

For those with a High Risk of Breast Cancer -BRCA1 and BRCA2 Genes, Family History, LCIS
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Janette
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Cancer gene linked to increased fertility

Postby Janette » Thu Oct 13, 2011 8:19 pm

Just for interest sake, of the possibility, not sure how reliable the study was.

Gene mutations that raise the risk of women having breast cancer are also linked to greater fertility, suggests new research.

The study of women with BRCA 1 and BRCA 2 gene mutations is reported today in the Proceedings of the Royal Society B.

"Elevated fertility of female mutation carriers indicates that they are more fecund despite their elevated post-reproductive mortality risks," write Dr Ken Smith of the University of Utah and colleagues.

Mutations in the BRCA1/2 genes have been linked to an increase risk of breast and ovarian cancer.

"They are really quite deleterious mutations," says Smith. "Usually natural selection eliminates such genes from the population."

"So for us the question was why are these particular genetic mutations still present in the population."

Indeed, BRCA1/2 has been hypothetically linked with lower fertility in the past.

Smith and colleagues looked at the family sizes of women who tested positive for BRCA1/2 mutations, and compared them to those of a control population.

To check for the impact of contraception, the researchers studied one group of women born before 1930 and another younger group born after 1930.

Those who had BRCA1/2 mutations were more likely to die earlier but also to have significantly more children than controls. They also had shorter birth intervals and ended childbearing later than controls.

The same trends applied to women in the younger 'post-1930' group, although those with BRCA1/2 mutations did not have as many children as their counterparts in the older group - probably due to the availability of contraception, say researchers.
Possible mechanism

BRCA1/2 are essential genes for the recognition of DNA damage and repair. Everyone has two copies of these genes, but a particular mutation knocks out one copy of the gene, lowering the capacity to repair DNA damage.

While this increases the risk of cancer, Smith and colleagues argue there is also a silver lining.

They say the protein expressed from BRCA1/2 genes suppresses the lengths of telomeres, which protect the end of chromosomes.

And having a mutation in your genes means your telomeres will be longer, and this has been linked to greater fertility, say the researchers.
Worth following up

Australian geneticist, Professor Rodney Scott of the University of Newcastle says the research is "intriguing", but more research is needed to confirm the findings.

"It's certainly worth following up," he says.

As discussed by Smith and colleagues, previous smaller-scale studies in other populations found no effect of BRCA1/2 mutations on fertility.

Scott wonders whether cultural factors could help explain the most recent findings, which fly in the face of these previous results. The new study was carried out in Utah, which has a large population of people who follow the Mormon Church.

He also has questions about the representativeness of the sample chosen by the researchers.

Scott says BRCA1/2 increases the risk of a woman getting breast cancer by age 70, by between 50 and 80 per cent, depending on other risk factors.

But he says the researchers only chose women from families with a high incidence of breast cancer and were at high risk for cancer.

"These families are not necessarily representative of women in the general population who carry BRCA1 or BRCA2 mutations," says Scott.

He says it may be that only women at high risk for breast cancer have greater fertility.

Scott says the exclusion of women who were never married or who had "incomplete spouse information" from the study could also have introduced a bias to the sample.

"[The findings] may well be true, but one needs to look more closely at some of these confounders to prove whether or not this is a real finding or a mysterious finding as a result of some bias," he says.
Evolutionary perspective

Scott says BRCA mutations may have an important evolutionary role because DNA damage can be a source of genetic diversity.

"So the idea that you get increased fertility in this small proportion of people, compared to the general population could in an evolutionary sense be very beneficial," he says.

Scott says in the future, IVF screening could well reduce the number of offspring by women with BRCA1/2 mutations if they choose to screen out embryos that have the mutations.
Janette


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