Israeli researchers have discovered a protein that seems to prevent the growth of pancreatic cancer.

The protein could potentially be effective against other aggressive cancers as well.

Researchers from the Cancer Research Center at Sheba Medical Center in Tel Hashomer studied the behavior of the protein klotho, a natural hormone emitted by the brain and kidneys that is known to retard the aging process. (The protein is named after the Greek mythological fate that spun thread to keep a person alive. )

A study done by Sheba in 2008 found that when injected into laboratory cultures of breast cancer cells, klotho prevented them from multiplying.

Later, researchers discovered that mutations of this protein greatly increase the risk of women developing breast cancer: Women carrying the BRCA1 or BRCA2 mutation have a 50 to 85 percent chance of developing breast cancer, while the rate in the general population is only 11 percent.

The current study for the first time examined whether klotho could be used to treat cancer in mice.

The mice used had pancreatic cancer, which is considered a particularly aggressive cancer that spreads rapidly: The average life expectancy of someone with advanced pancreatic cancer is only six months, and there are no effective treatments.

The researchers first noticed that healthy pancreatic cells contained klotho, whereas cancerous cells did not.

That means that testing pancreatic cells for klotho could provide an early indication of the presence of the cancer.

They then injected the cancerous mice with klotho, and discovered that it not only prevented the cancer from spreading, but actually caused it to shrink.

"Within a week or two after the protein was injected, the [cancerous] growths stopped spreading and began to shrink," said Dr. Ido Wolf, the lead researcher on the study, who heads both Sheba's oncology department and one of the labs at the Cancer Research Center. Dr. Lilach Abramovitz and Dr. Tami Rubinek were also on the research team.

The results of the study, which was funded by the Israel Cancer Association, are due to be published soon in the journal "Clinical Cancer Research."

The researchers' next goal is to search for ways to reduce the side effects. "This protein is vital for controlling the level of calcium and phosphorus in the body, and administering the protein is like administering any other hormone: It has the side effect of increasing hormonal activity," Wolf explained.

The researchers are also looking into cooperating with commercial firms to advance the project.

The Israeli study follows recent findings by researchers elsewhere about klotho's role in preventing the spread of liver and cervical cancer.

That hormones play some role in the growth of cancer cells has been known for some time.

"There is a known connection between cancer and diabetes, [a disease] that involves unusual hormonal activity, and the current research provides an additional source for examining the connection between hormones and cancer," Wolf said.

A study by the Maccabi health maintenance organization published in April 2010 found that diabetes raises the risk of women developing some form of cancer by 25 percent, and raises the risk of their developing pancreatic cancer specifically by 89 percent.

On average, 610 Israelis are diagnosed with pancreatic cancer every year.

This form of cancer accounts for eight out of every 100,000 deaths among Israeli men and six out of every 100,000 deaths among Israeli women.