The promyelocytic leukemia gene, PML was originally discovered because of its involvement in acute promyelocytic leukemia (APL) (1–4), and was later shown to encode a homo-multimeric protein with predominant nuclear localization, wide tissue expression, and prevalent tumor suppressive functions, both in hematological and solid malignancies (Figure 1). This evidence concerns the gene PML and acute promyelocytic leukemia.