June 24, 2008

Vaccine Stops Colon Cancer's Spread in Mice

TUESDAY, June 24 (HealthDay News) -- A new vaccine to treat and prevent metastatic colon cancer appears to work in mice, researchers report.

The vaccine has one unique property: It acts on the immune system in the intestines, a separate immune system from the one that protects the body generally.

"There are two independent immune systems in our bodies, the central one and one in the gut," said lead researcher Dr. Scott Waldman, chairman of Pharmacology and Experimental Therapeutics at Jefferson Medical College at Thomas Jefferson University in Philadelphia.

The theory behind the new vaccine is to take advantage of the immune system in the intestines where colon cancer starts, Waldman said. By targeting this immune system, a vaccine could develop antibodies to the cancer, he explained.

The vaccine targets a protein called guanylyl cyclase C (GCC), which is normally made in the intestines, Waldman said. "This protein is actually over expressed when cells lining the intestines transform from normal intestinal cells to colorectal cancer cells," he said.

"The idea was to take GCC and immunize the animals to see if the animals would mount an immune response," Waldman said.

The report is published in the June 24 online issue of the Journal of the National Cancer Institute.

In the experiments, Waldman's team engineered a vaccine that expressed GCC, and injected it into mice that had been given colon cancer cells.

"The vaccine did produce an immune response," Waldman said. "That immune response is effective in preventing metastatic colon cancer and actually extended the lives of these animals."

The animals that received the vaccine developed fewer tumors in the liver and lung compared with unvaccinated mice, Waldman said. In addition, the vaccine also improved survival to an average of 38 days, compared with 29 days in unvaccinated mice.

Waldman envisions the vaccine being used to treat patients with metastatic colon cancer. In addition, he believes the vaccine can be used to prevent the recurrence of colon cancer in people who have had the disease.

In addition, the vaccine might be useful in preventing colon cancer from developing in people who are at high risk for the disease, Waldman said. These include people who are prone to developing colorectal polyps, those with a family history of the disease, and people who are genetically predisposed to colon cancer.

Waldman's team is working on a new vaccine, what he calls a "souped-up" version that he believes will be even more effective. Ultimately the goal is to try the vaccine on people in a phase I trial, Waldman said.

More information

For more information on colon cancer, visit the American Cancer Society .

SOURCES: Scott Waldman, M.D., Ph.D., professor and chairman, Pharmacology and Experimental Therapeutics, Jefferson Medical College of Thomas Jefferson University, Philadelphia; June 24, 2008, Journal of the National Cancer Institute, online
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