PML and axial length measurement: AL results from clonal proliferation of myeloid and lymphoid progenitor cells.268 Acute promyelocytic leukemia (APL, the most curable AML subtype) has been labeled a paradigm for targeted differentiation therapy.269 APL results from a t(15;17)(q22;q21) translocation that fuses RARA (a gene encoding retinoic acid receptor α, RARα) on 17q21 to PML (a gene encoding promyelocytic leukemia protein, PML) on 15q22.