Cancer Vaccine Shows Promise in Mice

Scientists have overcome major hurdle, but treatments could still be decades away

TUESDAY, May 23, 2006 (HealthDay News) -- A new type of vaccine, tested in mice, could be a longer lasting form of cancer treatment and may even lead the way toward preventing cancer, Swedish researchers report.

The DNA-based vaccine was shown to prevent cancer growth in mice. The vaccine works by mimicking the effects of angiostatin, a piece of a protein that suppresses tumor growth by preventing new blood vessels from forming in tumors. This is a treatment strategy known as antiangiogenesis.

"This is a whole different approach," said Dr. Len Lichtenfeld, deputy chief medical officer of the American Cancer Society. "It's a way of using the body's own defense mechanisms to fight cancer. The implications are significant."

The findings appear in this week's issue of the Proceedings of the National Academies of Science.

According study author Dr. Lars Holmgren, of the Cancer Center at the Karolinska Institute in Stockholm, "the problem with angiostatin has been that it has a low half-life when given to patients," meaning it stays active in the body for only a short time.

"Therefore, we decided to find the [cell] receptor for angiostatin, which we did," he said. The researchers named that receptor "angiomotin."

In their study, Holmgren's team developed a method using a DNA vaccine to block the receptor by inserting the gene for angiomotin. Once the gene was inside mouse cells, it became a free-floating copy of the target receptor, he explained.

This caused the mice to develop immune antibodies to angiomotin, extending the effects of tumor-suppressing angiostatin.

The result: Vaccinated mice showed reduced growth of breast cancer tumors.

"We may have solved the problem of the low half-life of angiostatin by using either DNA vaccination or therapeutical antibodies," Holmgren said. "This opens up a new way of inhibiting angiogenesis," he said.

This method could be used to target angiogenesis-driven diseases, Holmgren said. In addition to cancer, these include eye diseases such as macular degeneration and atherosclerosis.

It has also been suggested that this approach could be used to prevent the growth of smaller tumors, Holmgren said. "But with this type of DNA vaccination, it's too early to say," he said.

Lichtenfeld said the discovery could be a breakthrough in researcher for the treatment and prevention of cancer. But he also cautioned that real applications are a long way off.

"This is an exciting study," Lichtenfeld said. "[But] it's a long way from the laboratory to the bedside to prove that this works. But if it does, we are talking about something that could be a preventive strategy for cancer. Of course, it's decades away."

More information

For more on cancer vaccine research, head to the U.S. National Cancer Institute.

SOURCES: Lars Holmgren, M.D., Ph.D., Cancer Center, Karolinska Institute, Stockholm, Sweden; Len Lichtenfeld, M.D., deputy chief medical officer, American Cancer Society, Atlanta; May 22-26, 2006, Proceedings of the National Academy of Sciences online
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