Etoposide induces chimeric Mll gene fusions.
MLL gene fusions are the hallmark of more than 70% of therapy-related leukemias (t-ML) associated with topoisomerase II inhibitors (e.g., etoposide) and cause leukemia in murine transgenic models. To determine whether Mll genomic fusions can occur after exposure to topoisomerase II inhibitors, we developed a long-distance inverse PCR DNA-based assay for chimeric Mll fusions in mouse embryonic stem cells. We detected Mll fusions at a higher frequency following 100 microM etoposide for 8 h (16x10(-6) cell(-1)) than in no-drug controls (1.0x10(-6) cell(-1), P=0.0002) or after treatment with a comparably cytotoxic exposure to the antimicrotubule drug vincristine (1.0x10(-6) cell(-1), P=0.0047). The fusion points in Mll chimeric products induced by etoposide were localized to a 1.5 kb region between exons 9 and 11, analogous to the MLL breakpoint cluster region in human leukemia. All 49 Mll fusion partners analyzed matched known genomic murine sequences, with 40 (82%) matching annotated genes covering eighteen murine autosomes. One partner was Runx1, the murine homologue of the transcription factor AML-1, a target of human translocations in therapy-related leukemia. These findings indicate that etoposide triggers the formation of Mll gene fusions, a critical step for the development of treatment-induced leukemic transformation.
Blanco
Javier G
JG
Department of Pharmaceutical Sciences, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, USA.
Edick
Mathew J
MJ
Relling
Mary V
MV
D000818:Animals; D000972:Antineoplastic Agents, Phytogenic / Q000633:toxicity*; D019677:Artificial Gene Fusion; D004268:DNA-Binding Proteins / Q000235:genetics*; D004791:Enzyme Inhibitors / Q000633:toxicity; D005047:Etoposide / Q000633:toxicity*; D011495:Histone-Lysine N-Methyltransferase; D006801:Humans; D007938:Leukemia / Q000139:chemically induced / Q000235:genetics; D051379:Mice; D051788:Myeloid-Lymphoid Leukemia Protein; D015514:Oncogene Proteins, Fusion / Q000235:genetics*; D011519:Proto-Oncogenes; D059005:Topoisomerase II Inhibitors; D014157:Transcription Factors
D000972:Antineoplastic Agents, Phytogenic; D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; C497422:KMT2A protein, human; D015514:Oncogene Proteins, Fusion; D059005:Topoisomerase II Inhibitors; D014157:Transcription Factors; D051788:Myeloid-Lymphoid Leukemia Protein; D005047:Etoposide; D011495:Histone-Lysine N-Methyltransferase; C497423:Kmt2a protein, mouse