NEW YORK: Researchers say they have found a molecule that triggers breast cancer. The discovery eventually may enable doctors to head off the disease before tumors develop. The study, published in the April issue of The Journal of Clinical Investigation, was performed by researchers at the State University of New York at Stony Brook. The molecule, mitogen-activated protein kinase, or MAP kinase, is five to 20 percent more prevalent in women with breast cancer than in those without the affliction. Researchers say the molecule's migration into the nucleus of a breast cell causes the cell to begin replicating wildly, thus causing cancer. If confirmed, the discovery would allow doctors to test for high levels of MAP kinase and identify women at risk of the disease well before deadly tumors begin to develop.