17 September 1998

DNA Based Vaccine Blows Away Rat Cancer

Scientists at Memorial Sloan-Kettering Cancer Center in New York have shown that a new DNA-based vaccine can successfully treat the deadly skin cancer, melanoma, in mice. The investigators, who report their findings in the September 15 issue of the Journal of Clinical Investigation, used a "needleless syringe" called a gene gun to drive tiny particles of human DNA at high speed into the mice's skin. The human protein differed just enough from its mouse counterpart to trick the immune system into producing a powerful immune attack. The immune cells attacked both the melanoma cells and the pigment cells in the skin of the mice, which share a protein called gp75 that is not found in other tissues.

"Our study shows how we can use DNA immunization to make the immune system recognize and attack cancer cells," said Dr. Alan Houghton, senior author of the study. "These DNA vaccines are unique because they can trigger immunity where other types of vaccines can fail to stimulate an immune response".

The mice were immunized with human DNA via a novel delivery system called a gene gun, in which microscopic gold particles were coated with the human DNA and injected into the mice's skin using a burst of helium gas. Once inside the skin cells, the DNA triggered an immune response.

In the study, Dr. Houghton and his research team attempted to induce an immune attack by using the gene gun to immunize the mice with either a purified form of mouse DNA, or the human DNA. When the investigators later examined the lungs of the mice, they found that the tumors were widespread in those who had received the mouse DNA and could not detect an immune response. However, the tumors had regressed by 86 per cent in the mice injected with human DNA and the researchers found a marked immune response.

The same strategy is being tested against prostate, breast and lymphoma cancers in mice, as they also share specific proteins with their normal cell counterparts. Dr. Houghton's research team plans to begin clinical trials using DNA from mice in melanoma patients some time next year.