Topoisomerase II inhibitors are among the most successful chemotherapy drugs used to treat human cancer. But a small percentage of patients treated with these agents recover from their initial malignancy only to develop a second cancer, leukemia. Researchers at UC Davis Cancer Center have shed new light on this poorly understood process. In a study to be published in the Nov. 22 issue of the journal Leukemia, the researchers report that topoisomerase II inhibitors do not directly cause leukemia -- and suggest that it may be possible to prevent therapy-induced leukemia. (The study was posted online in the journal on Sept. 29.)