“The way we look at it, Alzheimer’s disease is really cancer of the brain,” says Rachael Neve, Harvard Medical School associate professor of psychiatry at McLean Hospital. “But neurons cannot divide and form tumors so they undergo apoptosis (cell death) instead.” Neve; Donna McPhie, Harvard Medical School instructor in psychiatry; and their colleagues show in a study appearing in the July 30, 2003 Journal of Neuroscience that a substance known as amyloid precursor protein, or APP, is implicated in Alzheimer’s disease. The study shows not only that APP kills neurons but also how it carries out its killing. More important, they provide a new and surprising conception of the nature of Alzheimer’s disease, one that could lead to a fundamental shift in how the disease is viewed and treated.