Cancer Vaccines
An interesting new approach to the treatment of cancer is
the development of "cancer vaccines". Unlike conventional vaccines, which
are designed to prevent disease, these vaccines are designed to combat
it. A patient's tumor cells are removed from the body. Genes whose products
are known to stimulate the immune system are then inserted into the cells.
The modified tumor cells are then irradiated to kill them and reintroduced
into the body.
The "vaccine" works in the following manner, according to Dr. Richard Mulligan, of the Whitehead institute: "The hope is that when the immune system encounters these substances (inserted gene products) in close proximity to tumor antigens -- protein markers on the surface or inside of tumor cells -- it will be stimulated to kill all similarly marked tumor cells throughout the body."1 Genes that have been investigated for use in modifying cancer cells include those coding for interleukin-2, Interleukin tumor necrosis factor-alpha (TNF-a), and other cytokines and growth factors. One of the most promising anti-cancer agents used in this manner was granulocyte-macrophage colony stimulating factor, or GM-CSF. This method of treatment is promising in that it shows an effect on pre-established tumors, protects against unmodified cells, and does not seem to attack normal cells. This is an area of research that is still under investigation and is not yet completely understood. Early results are, however, promising. Problems associated with this method include difficulties in cultivating tumor cells outside the body and the time it takes to develop a vaccine. Because a vaccine must be prepared from a patient's specific cancer cells, this soaks up valuable time while a patient is suffering from cancer. Alternatively, recent work has investigated the use of cell-free vaccines. These vaccines use tumor antigen-derived peptides to stimulate the immune system's attack of cancer cells.2 Cancer vaccines are a new area of research and must continue to be investigated. However, they show promise in their effectiveness toward attack of cancerous cells and their lack of attack on normal, healthy cells. Side effects are minimal. References:
2. Proc. Natl. Acad. Sci. USA Vol. 94, pp. 3262-3267,
April 1997
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