IDO, ITO, tryptophan, and Cancer Immunotherapy

One for the archives but this is interesting because it has long been known that tumours often express proteins that inhibit immune responses. http://medicalxpress.com/news/2012-01-cancer-therapy-preclinical.html ...

Scientists from the Ludwig Institute for Cancer Research (LICR) in Brussels identified a new target for cancer therapy, an enzyme which prevents the immune system from recognizing and destroying certain types of tumors. Called tryptophan 2,3-dioxygenase or TDO, the enzyme works by depriving immune cells of tryptophan, an amino acid essential to their activity. TDO is produced by a significant number of human tumors. Scientists also show that blocking TDO activity with a novel TDO inhibitor promotes tumor rejection in mice. The study findings were published online today in the January 30 issue of the Proceedings of the National Academy of Sciences (PNAS).