PML and acute promyelocytic leukemia: Acute promyelocytic leukemia (APL) is characterized by chromosomal translocations between the retinoic acid receptor alpha (RARA or PARα) gene and the promyelocytic leukaemia (PML) or promyelocytic leukaemia zinc finger (PLZF) genes among which PML-RARA is the most common gene fusion APL cells expressing the PLZF/RARα fusion protein are largely resistant to standard treatments and are associated with poor prognosis.