Analysis of t(15;17) chromosomal breakpoint sequences in therapy-related versus de novo acute promyelocytic leukemia: association of DNA breaks with specific DNA motifs at PML and RARA loci.

We compared genomic breakpoints at the PML and RARA loci in 23 patients with therapy-related acute promyelocytic leukemia (t-APL) and 25 de novo APL cases.Eighteen of 23 t-APL cases received the topoisomerase II poison mitoxantrone for their primary disorder. DNA breaks were clustered in a previously reported 8 bp "hot spot" region of PML corresponding to a preferred site of mitoxantrone-induced DNA topoisomerase II-mediated cleavage in 39% of t-APL occurring in patients exposed to this agent and in none of the cases arising de novo (P = 0.