New research by Dana-Farber Cancer Institute scientists raises the prospect of cancer therapy that works by converting a tumor's best friends in the immune system into its gravest enemies.In a study published in the journal Science, an international collaboration of investigators from Dana-Farber, Harvard Medical School, Boston Children's Hospital, and the University of Strasbourg uncovered a mechanism that allows key immune system cells to keep a steady rein on their more belligerent brother cells, thereby protecting normal, healthy tissue from assault. The discovery has powerful implications for cancer immunotherapy researchers say: by blocking the mechanism with a drug, it may be possible to turn the attack-suppressing cells into tumor-attacking cells.