Therapy-related acute myeloid leukemia–like MLL rearrangements are induced by etoposide in primary human CD34+ cells and remain stable after clonal expansion

• Published in: Blood Vol. 105; no. 5; pp. 2124 - 2131
• Main Authors: Libura, Jolanta, Slater, Diana J., Felix, Carolyn A., Richardson, Christine
• Format: Journal Article
• Language: English
• Published: Washington, DC Elsevier Inc 01.03.2005; The Americain Society of Hematology
• Subjects: Acute Disease; Antigens, CD34; Biological and medical sciences; Cell Proliferation; Cells, Cultured; Clone Cells; DNA-Binding Proteins - genetics; Drug toxicity and drugs side effects treatment; Etoposide - adverse effects; Fetal Blood; Gene Rearrangement - drug effects; Hematologic and hematopoietic diseases; Hematopoietic Stem Cells - drug effects; Hematopoietic Stem Cells - pathology; Histone-Lysine N-Methyltransferase; Humans; Leukemia, Myeloid - chemically induced; Leukemia, Myeloid - genetics; Leukemias. Malignant lymphomas. Malignant reticulosis. Myelofibrosis; Medical sciences; Miscellaneous (drug allergy, mutagens, teratogens...); Myeloid-Lymphoid Leukemia Protein; Neoplasms, Second Primary - genetics; Pharmacology. Drug treatments; Proto-Oncogenes - genetics; Transcription Factors - genetics; Translocation, Genetic; Chromosomal aberration; Antineoplastic agent; Human; DNA topoisomerase (ATP-hydrolysing); Enzyme; Toxicity; Acute; Enzyme inhibitor; Etoposide; Malignant hemopathy; Malignant tumor; Carcinogenesis; Clonal expansion; Podophyllotoxine derivatives; Isomerases; Treatment; Second cancer; Gene rearrangement; Abnormal chromosome; Leukemogenesis; Antimitotic; Acute myelocytic leukemia; Chromosome translocation
• ISSN: 0006-4971; 1528-0020
• DOI: 10.1182/blood-2004-07-2683

Rearrangements involving the MLL gene on chromosome band 11q23 are a hallmark of therapy-related acute myeloid leukemias following treatment with topoisomerase II poisons including etoposide. Therapy-related and de novo genomic translocation breakpoints cluster within a well-characterized 8.3-kb fragment of MLL. Repair of etoposide-stabilized DNA topoisomerase II covalent complexes may initiate MLL rearrangements observed in patients. We used a culture system of primary human hematopoietic CD34+ cells and inverse polymerase chain reaction to characterize the spectrum of stable genomic rearrangements promoted by etoposide exposure originating within an MLL translocation hotspot in therapy-related leukemia. Alterations to the region were observed at a readily detectable frequency in etoposide-treated cells. Illegitimate repair events after minimal repair included MLL tandem duplications and translocations, with minor populations of deletions or insertions. In stably repaired cells that proliferated for 10 to 14 days, the significant majority of illegitimate events were MLL tandem duplications, and several deletions, inversions, insertions, and translocations. Thus, etoposide promotes specific rearrangements of MLL consistent with the full spectrum of oncogenic events identified in leukemic samples. Although etoposide-initiated rearrangements are frequent, only a small subset of translocations occurs in cells that proliferate significantly.