Biological features of primary APL blasts: their relevance to the understanding of granulopoiesis, leukemogenesis and patient management

In recent years, discovery of the in vitro and in giro differentiation of A PL blasts by all-trans retinoic acid (ATRA) has modified the therapeutic ap proach of APL and lead to important advances in understanding the biology o f APL. Since it became apparent that differentiation therapy of APL with AT RA was indeed a true model of targetted therapy, evidencing the molecular t argets of retinoic acid efficacy became crucial. These molecular targets ar e closely related to the biological features of APL cells, some of which ar e well-known and have contributed to the morphological and cytogenetic defi nition of the leukemia, others have just been defined or re-discovered in t he light of a better understanding of molecular controls of cell growth and differentiation. The aims of characterizing the biological features of APL cells should allow a better management of APL therapy and the identificati on of potential markers for differentiation therapies in other leukemias or solid tumors.