PML and acute promyelocytic leukemia: Promyelocytic leukemia protein (PML) is a tumor suppressor that was initially identified as a fusion partner of human retinoic acid receptor alpha (RARα) as a result of a chromosomal translocation found in the acute promyelocytic leukemia patients (APL; de Thé et al., 1991; Kakizuka et al., 1991).