These studies revealed that besides specifically targeting the promyelocytic leukemia gene product (PML) and the APL-specific fusion protein of PML with the retinoic acid receptor alpha (PML-RAR-a) thereby promoting cell differentiation of leukemia cells, ATO can interfere with mitochondrial functions, the cellular redox system, the cell cycle and apoptosis. The gene discussed is PML; the disease is leukemia.