GM mouse immune to cancer
Cancer tumours somehow escape the body's immune system, even when that immune system is primed by a vaccine designed to specifically target the cancer.
Recent work with a GM strain of mice helps explain why. Many 'normal' cancers are made up of a mixture of cell-types including a small proportion of cells that produce a protein called FAP (fibroblast activation protein).
FAP is usually produced in normal cells that heal wounds. By producing FAP, cancer fools the body into thinking the cancer is a wound. FAP not only stops rejection, it also encourages the production of blood vessels that nourish the cancer. The evidence was seen in GM mice that developed cancers and could also have their FAP production altered. When FAP production was turned off in these mice, the mouse immune system was able to attack and reduce the volume of the cancers.
Because of FAP's role in normal wound healing, it is unlikely that FAP could be the basis of a vaccine against cancer. Instead, a treatment based on the new understanding of FAP's role in cancer may be possible.