Retinoic acid-induced remission

Acute promyelocytic leukaemia, APL, is a rare type of acute myeloid leukaemia (AML). It is distinguished from other acute leukaemias by the presence in the bone marrow of large numbers of abnormal promyelocytes, with characteristic granules; by a potentially fatal bleeding disorder, often aggravated by chemotherapy; by a diagnostic chromosomal translocation, t(15; 17) (q22; q11-22); and by its unique response to retinoic acid (RA) in vivo and in vitro. Cloning of the translocation breakpoint associated with APL has revealed that the translocation disrupts the RA receptor alpha (RARA) gene on chromosome 17 and the previously uncharacterized promyelocytic leukaemia (PML) gene on chromosome 15. RAR alpha is one of the steroid/thyroid hormone receptors, a sub-family of nuclear receptors, with binding domains for its ligand, RA, and for DNA. In the presence of RA, the RAR can activate or inhibit the transcription of genes that possess RA response elements.