Retinoids in haematology: a timely revival?

The retinoic acid receptors (RARA, RARB, RARG) are ligand-regulated nuclear receptors which act as transcriptional switches. These master genes drew significant interest in the 1990s due to their key roles in embryogenesis and involvement in a rare malignancy, acute promyelocytic leukemia (APL), in which the RARA (and very rarely RARG or RARB) genes are rearranged, underscoring the central role of deregulated retinoid signaling in leukemogenesis. A number of recent provocative observations have revived interest in the roles of retinoids in non-APL acute myeloid leukemia (AMLs), as well as in normal hematopoietic differentiation. Here we review the role of retinoids in hematopoiesis, as well as in the treatment of non-APL AMLs. From this perspective, broader uses of retinoids in the management of hematopoietic tumors is discussed.