Researchers may be on track to finding a preventive for breast cancer.

Scientists have discovered the body produces a protein during pregnancy that directly inhibits growth of the cancer. The researchers say those proteins, produced by the liver of a fetus, might be used as a natural agent for the treatment and even prevention of the disease.

"The body has a natural defense system against breast cancer," said lead researcher Herbert Jacobson of Albany Medical College. He adds the protein known by the initials AFP "needs to be safely harnessed and developed into a drug."

Medical experts caution this research doesn't directly demonstrate the cancer preventive activity of AFP. Cancer Prevention Research Editorial Board Member Dr. Powel Brown says while pre-clinical findings are important and suggest a role of AFP in breast cancer prevention, the discovery isn't yet ready for prime time.

Research details are published in "Cancer Prevention Research," the journal of the American Association for Cancer Research.