title: Near-precise interchromosomal recombination and functional DNA topoisomerase II cleavage sites at MLL and AF-4 genomic breakpoints in treatment-related acute lymphoblastic leukemia with t(4;11) translocation.
abstract: We analyzed the der(11) and der(4) genomic breakpoint junctions of a t(4;11) in the leukemia of a patient previously administered etoposide and dactinomycin by molecular and biochemical approaches to gain insights about the translocation mechanism and the relevant drug exposure. The genomic breakpoint junctions were amplified by PCR. Cleavage of DNA substrates containing the normal homologues of the MLL and AF-4 translocation breakpoints was examined in vitro upon incubation with human DNA topoisomerase IIalpha and etoposide, etoposide catechol, etoposide quinone, or dactinomycin. The der(11) and der(4) genomic breakpoint junctions both involved MLL intron 6 and AF-4 intron 3. Recombination was precise at the sequence level except for the overall gain of a single templated nucleotide. The translocation breakpoints in MLL and AF-4 were DNA topoisomerase II cleavage sites. Etoposide and its metabolites, but not dactinomycin, enhanced cleavage at these sites. Assuming that DNA topoisomerase II was the mediator of the breakage, processing of the staggered nicks induced by DNA topoisomerase II, including exonucleolytic deletion and template-directed polymerization, would have been required before ligation of the ends to generate the observed genomic breakpoint junctions. These data are inconsistent with a translocation mechanism involving interchromosomal recombination by simple exchange of DNA topoisomerase II subunits and DNA-strand transfer; however, consistent with reciprocal DNA topoisomerase II cleavage events in MLL and AF-4 in which both breaks became stable, the DNA ends were processed and underwent ligation. Etoposide and/or its metabolites, but not dactinomycin, likely were the relevant exposures in this patient.
authors.affiliation: Division of Oncology, Research Institute, Children's Hospital of Philadelphia, PA 19104, USA.
authors.forename: B D
authors.initials: BD
authors.lastname: Lovett
authors.forename: L
authors.initials: L
authors.lastname: Lo Nigro
authors.forename: E F
authors.initials: EF
authors.lastname: Rappaport
authors.forename: I A
authors.initials: IA
authors.lastname: Blair
authors.forename: N
authors.initials: N
authors.lastname: Osheroff
authors.forename: N
authors.initials: N
authors.lastname: Zheng
authors.forename: M D
authors.initials: MD
authors.lastname: Megonigal
authors.forename: W R
authors.initials: WR
authors.lastname: Williams
authors.forename: P C
authors.initials: PC
authors.lastname: Nowell
authors.forename: C A
authors.initials: CA
authors.lastname: Felix
mesh_terms: D000951:Antigens, Neoplasm; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000009:adverse effects* / Q000627:therapeutic use; D002396:Catechols / Q000494:pharmacology; D002648:Child; D019457:Chromosome Breakage; D002880:Chromosomes, Human, Pair 11 / Q000235:genetics* / Q000648:ultrastructure; D002894:Chromosomes, Human, Pair 4 / Q000235:genetics* / Q000648:ultrastructure; D003131:Combined Modality Therapy; D003520:Cyclophosphamide / Q000008:administration & dosage; D004250:DNA Topoisomerases, Type II / Q000378:metabolism*; D004273:DNA, Neoplasm / Q000187:drug effects; D004268:DNA-Binding Proteins / Q000235:genetics; D003609:Dactinomycin / Q000008:administration & dosage / Q000009:adverse effects* / Q000494:pharmacology; D005047:Etoposide / Q000008:administration & dosage / Q000009:adverse effects* / Q000494:pharmacology; D005260:Female; D011495:Histone-Lysine N-Methyltransferase; D006801:Humans; D007069:Ifosfamide / Q000008:administration & dosage; D007527:Isoenzymes / Q000378:metabolism*; D008957:Models, Genetic; D008969:Molecular Sequence Data; D051788:Myeloid-Lymphoid Leukemia Protein; D009363:Neoplasm Proteins / Q000378:metabolism; D016609:Neoplasms, Second Primary / Q000139:chemically induced / Q000235:genetics*; D009687:Nuclear Proteins / Q000235:genetics; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma / Q000139:chemically induced / Q000235:genetics*; D011519:Proto-Oncogenes; D018714:Radiotherapy, Adjuvant; D011995:Recombination, Genetic; D018232:Rhabdomyosarcoma, Alveolar / Q000188:drug therapy / Q000532:radiotherapy; D012983:Soft Tissue Neoplasms / Q000188:drug therapy / Q000532:radiotherapy; D014157:Transcription Factors; D035602:Transcriptional Elongation Factors; D014178:Translocation, Genetic / Q000235:genetics*; D014750:Vincristine / Q000008:administration & dosage
chemical_list: D000951:Antigens, Neoplasm; D002396:Catechols; D004273:DNA, Neoplasm; D004268:DNA-Binding Proteins; D007527:Isoenzymes; C497422:KMT2A protein, human; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D014157:Transcription Factors; D035602:Transcriptional Elongation Factors; D051788:Myeloid-Lymphoid Leukemia Protein; C081449:AFF1 protein, human; D003609:Dactinomycin; D014750:Vincristine; D005047:Etoposide; D003520:Cyclophosphamide; D011495:Histone-Lysine N-Methyltransferase; D004250:DNA Topoisomerases, Type II; C034221:catechol; D007069:Ifosfamide