Researchers reveal new insights into how acute myeloid leukemia (AML) develops and progresses. Normal isocitrate dehydrogenase enzymes (IDH) are important in cellular metabolism, but mutants produce the carcinogen 2-hydroxyglutarate (2-HG) that causes cancer cells to die at higher concentrations. The team has worked out the threshold at which 2-HG switches from a carcinogen to a cancer-killing agent and the mechanism by which AML cells prevent this switch to keep dividing.