Moving closer to a vaccine for cancer.

In cancer, the immune system fails to protect the body. The goal of a cancer vaccine is basically to prod the system into marshaling a successful attack against tumor cells it might otherwise tolerate. That promise appears to be nearing reality. Researchers this week announced advances in two types of vaccines, one of which has already been used successfully in human trials. Their results were reported at an American Cancer Society seminar in San Diego.

Michael G. Hanna Jr. of Litton Bionetics, Inc., in Rockville, Md., has been working on a vaccine that uses a cancer patient's own tumor cells to prevent recurrence. Hanna, with H.C. Hoover Jr., now at the State University of New York at Stony Brook, and others, began a trial on colorectal cancer victims in 1981, and the results from the ongoing study are encouraging. Twently patients whose tumors were surgically removed were given three vaccinations of their own tumor cells, which has been irradiated so they wouldn't reproduce. The first two shots were combined with an immune system booster. To date, none of the 20 has died and only four have had recurrences, whereas of 20 colorectal cancer patients undergoing surgery around the same time, four have died and another five have suffered recurrences.

To check for a true immune response the researchers inoculated the skin with weakened tumor cells. All of the vaccinated patients reacted to it, while none of the nonvaccinated patients did. "We were indeed getting biological modifications," says Hanna.

Several medical centers in the United States are now conducting a larger trial, the results of which should be available within three years. If the tests are successful, Hanna says, the vaccine should be available for clinical use as soon as it can be produced on a large scale. Meanwhile, he and others are working on improving the procedure. "While [the technique is] important, I don't think it is sufficient for complete control of solid tumors," he says. The key may be in combining vaccination with chemotherapy. Hanna and his co-workers have found that the initial immune response following vaccination opens up the tumor so that more chemotherapy can reach it. "In this situation, when we give chemotherapy, there is a greater effect," he says.

Other vaccine approaches are also being tried. Heinz Kohler and his colleagues at Roswell Park Memorial Institute in Buffalo are working on something called an anti-idiotype vaccine. By Presenting tumor antigens to the body in a new way, the vaccine breaks the body's preexisting tolerance to the tumor.

To get an anti-idiotype vaccine, researchers inject human tumor cells into a mouse, which responds by making antibody-producing cells. These cells can be harvested and fused with an immortal cell line, so that a good supply of antibody can be collected. This antibody is in turn injected into another mouse, where the procedure is repeated and a second antibody is collected.

The second antibody approximates the shape of the antigen that induced the first antibody. The procedure works something like a hall of mirrors--the reflection of a man raising his right hand will be raising its left hand, but a reflection of that image will be raising its right hand.

"The 'idiotype' cascade provides an antibody that could be a substitute for the original antigen," Kohler says. "The immune system seesn shapes, and doesn't care what is behind those shapes."

While an anti-idiopathic cancer vaccine has yet to reach the animal-testing stage, according to Kohler this type of vaccine has proved successful against viruses, bacteria and parasites. "I think within a year we'll have an anti-idiotype [cancer] vaccine that will work in an animal model," he says. Human trials, he estimates, are two to three years away.