By injecting leukemia patients with part of a protein found in greater abundance on cancerous cells than on healthy ones, researchers have been able to induce some patients’ immune systems to fight this blood cancer.

Jeffrey J. Molldrem of the University of Texas M.D. Anderson Cancer Center in Houston and his colleagues fashioned the cancer vaccine from a piece of proteinase 3, a compound overproduced by malignant blood cells in leukemia patients. Earlier research suggested that the piece, called PRI, stimulates production of immune system T cells that specifically target proteinase 3.

Molldrem’s group identified 15 patients with leukemia that had resisted other treatment. Each patient received three PRI injections, each separated by 3 weeks. In five people, the leukemia went into remission and their T cells showed a strong attraction to the leukemia cells. Three other patients in the group showed partial responses.

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