An antibiotic added to the drinking water of mice stops the progress of leukemia. Harvard researcher Claudia Huettner cannot do the same thing in humans, unfortunately, but through such experiments Huettner and her colleagues are gaining an understanding of how human leukemias arise. The new knowledge they have gained is providing them with a means to easily test new treatments for cancer. For example, new drugs are being developed to prolong the lives of people with acute lymphoblastic leukemia (ALL), the most common bone marrow cancer in children. Experiments with mice that get an equivalent disease in the same way as children with ALL do – by genetic mutation – could speed up testing of these and other therapies designed to prolong the lives of ALL patients.