The idea, said Dr. Jeffrey Miller, one of the researchers, is that the man-made cell won't die so it can stimulate the immune system longer than a living cell. So many variations are now in the works, including such seemingly far-out agents as tobacco proteins and pregnancy hormones in cancer vaccines. Now researchers have to see if, and how well, they work in humans. Even if they do work, experts say that vaccines are unlikely to be a panacea that replaces current treatments. For one thing, they're probably not very effective against large tumors, Amatruda said.
Tumors can overwhelm the body's defenses with hundreds of millions of cancer cells.
Some experts suggest that vaccines may work best as a kind of clean-up crew, mopping up cancer cells that surgery or other treatments miss. Those cells, they note, can be the most dangerous. In the long run, however, some experts say cancer vaccines may do more than treat disease. But because the vaccines would be tailored to specific types of cancer, they'd be limited to people at high risk of such diseases. The fear is that the vaccine might cause the very illness it's supposed to prevent, which has sometimes happened with other vaccines.