Johns Hopkins scientists have developed a vaccine that, in mice, can alert the immune system to the presence of stray cancer cells and significantly reduce their blood-borne spread.
"Metastatic cancer, or cancer that is spreading from its site of origin, is among the toughest stages of cancer to treat," says Hongxiu Ji, M.D., postdoctoral fellow. "Our findings suggest cancer vaccines could be an important tool for preventing and treating the spread of cancers."
Giving the vaccine prior to a tail vein injection of cancer cells prevented development of metastatic lung tumors in eight of 10 mice, while all the mice in two control groups that received cancer cells but no vaccine developed tumors. A second test against established lung cancer showed that the vaccine completely eliminated tumors in 50 percent of mice.
Ji presents her results, funded by the National Institutes of Health and the Richard W. TeLinde endowment, at this week's meeting of the American Society of Gene Therapy in Seattle.
The vaccine takes advantage of a protein, E7, produced by the human papilloma virus and commonly found in cervical cancers and their metastatic cancers. To make the vaccine, scientists altered vaccinia, a common virus, to include a gene for E7 and a molecular signal. The vaccine infects cells in the body, causing them to make E7, and the molecular signal triggers a chain reaction that calls E7 to the immune system's attention. This leads to an immune system attack on all cells that contain the protein--including the cancer cells.
To test whether the vaccine is effective against metastatic cervical cancer, Ji and her colleagues developed a line of tumor cells by genetically altering mouse lung cells to include E7. This made the cells similar to cervical cancer cells. She then showed that a tail vein injection of the cancer cells could cause lung tumors in mice in two weeks.