Acute promyelocytic leukaemia and the t(15;17) translocation.

Acute promyelocytic leukaemia (APL) is a rare acute myeloid leukaemia characterized by a distinctive coagulopathy, the differentiation of promyelocytes in response to all-trans retinoic acid and a reciprocal chromosomal translocation, t(15;17)(q22;q12-q21). Molecular analysis of the APL breakpoint has revealed the involvement of the retinoic acid receptor alpha (RARA) gene on chromosome 17 and the promyelocytic leukaemia (PML) gene on chromosome 15. Both reciprocal fusion products which arise as a result of the translocation, PML/RAR alpha and RAR alpha/PML, are expressed in many patients. PML/RAR alpha, is implicated in leukaemogenesis, and may block myeloid differentiation directly and/or interfere with the normal function(s) of PML and/or RAR alpha.