Although the experiments have only been in mice, researchers believe they have relevance for female cancer patients and women who suffer premature menopause, a condition that puts them at risk of early infertility, osteoporosis and heart disease.

In a paper to be published in the November 9 issue of the journal Molecular Cell, scientists in Australia found that egg cells, or oocytes, are killed not by radiation, but by two proteins -- puma and noxa -- which snap into action when they detect DNA damage to egg cells.

In experiments using mice that did not carry these proteins, the scientists found that their eggs survived radiation and they went on to produce normal offspring.

"This is very exciting. It means if you get rid of those proteins that kill, the oocytes or specialized egg cells can actually repair their DNA and that has never been known before," said lead author Clare Scott, an associate professor and oncologist at The Royal Melbourne and Royal Women's Hospitals.

Between 50 to 80 percent of eggs survived in these mice.

"These were enough to result in normal fertility in those mice and they could produce normal pups. Those pups went on to be fertile themselves and lived a normal lifespan with no evidence of tumors or other abnormalities," she said by telephone.

Scott's colleagues are conducting similar trials on human egg cells to see if the two proteins work in the same way. If all goes well, they hope a drug can be designed to block the two proteins from killing egg cells.

"If that pans out well, then we would hope that a drug that could target (the protein) puma ... be provided as a therapy for three to six months during cancer therapy," Scott said.

Such a drug that blocks the action of the proteins could possibly prevent premature menopause or infertility, she added.

"In a woman, premature menopause is caused by (early) death of specialized egg cells. And if you can get specialized egg cells to survive, then premature menopause won't occur."

(Reporting by Tan Ee Lyn; Editing by Ron Popeski)

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