title: Role of apoptotic nuclease caspase-activated DNase in etoposide-induced treatment-related acute myelogenous leukemia.
abstract: Etoposide-induced treatment-related acute myelogenous leukemia (t-AML) is characterized by rearrangements of the mixed lineage leukemia (MLL) gene with one of its >50 partner genes, most probably as a consequence of etoposide-induced DNA double-strand breaks (DSBs). Recent studies have shown that etoposide-induced DSBs occur predominantly within the breakpoint cluster region (bcr) of the MLL gene. However, bcr-specific DSBs induced by etoposide are not topoisomerase II-linked but the result of apoptotic nuclease-mediated DNA cleavage. Here, we test the involvement of caspase-activated DNase (CAD) and other apoptotic components in etoposide-induced gene rearrangements using two methods. First, we measured the effect of etoposide on the integration frequency of a transfected plasmid. Etoposide strongly stimulated plasmid integration in CAD cDNA-complemented mouse embryonic fibroblasts (MEFs) but not in CAD knockout (KO) MEFs. Consistently, down-regulation of ICAD (inhibitor of CAD, also required for proper folding of CAD) in an HT29-derived cell line, which leads to decreased CAD activity, significantly reduced etoposide-induced plasmid integration. Second, we used long-template inverse PCR to focus on gene rearrangements at the MLL locus. Etoposide stimulated MLL fusion product formation in CAD cDNA-complemented MEFs but not in CAD KO MEFs. Together, these results suggest that CAD and other apoptotic components may play an important role in etoposide-induced t-AML.
authors.affiliation: Department of Pharmacology, University of Medicine and Dentistry of New Jersey-Robert Wood Johnson Medical School, Piscataway, New Jersey 08854, USA.
authors.forename: Eszter S
authors.initials: ES
authors.lastname: Hars
authors.forename: Yi Lisa
authors.initials: YL
authors.lastname: Lyu
authors.forename: Chao-Po
authors.initials: CP
authors.lastname: Lin
authors.forename: Leroy F
authors.initials: LF
authors.lastname: Liu
mesh_terms: D000818:Animals; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D017209:Apoptosis / Q000502:physiology; D003851:Deoxyribonucleases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D005047:Etoposide / Q000494:pharmacology*; D015321:Gene Rearrangement / Q000187:drug effects; D019073:HT29 Cells; D006801:Humans; D015470:Leukemia, Myeloid, Acute / Q000139:chemically induced* / Q000201:enzymology*; D051379:Mice; D018345:Mice, Knockout; D051788:Myeloid-Lymphoid Leukemia Protein / Q000235:genetics
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D051788:Myeloid-Lymphoid Leukemia Protein; D005047:Etoposide; D003851:Deoxyribonucleases; C109663:caspase-activated deoxyribonuclease