Genomic and molecular switching in relapsed acute promyelocytic leukemia

Acute promyelocytic leukemia (APL) is characterized by a recurrent translocation between chromosomes 15 and 17, resulting in the fusion of the promyelocytic leukemia gene (PML) to the retinoic acid receptor gene (RAR).1 Among APL cases with a PML-RAR rearrangement, chromosome 15 breakpoints fall within three breakpoint cluster regions (bcrs): bcr1 and bcr3 correspond to PML introns 6 and 3, respectively, whereas bcr2 is located within PML exon 6, or very occasionally within PML exon 5. On the contrary, a single RAR breakpoint region occurs within intron 2.2