Etoposide-initiated MLL rearrangements detected at high frequency in human primitive hematopoietic stem cells with in vitro and in vivo long-term repopulating potential.
Rearrangements initiating within the well-characterized break-point cluster region of the mixed lineage leukemia (MLL) gene on 11q23 are a hallmark of therapy-related leukemias following treatment with topoisomerase II poisons including etoposide. Hematopoietic stem cells (HSC) are believed to be the target cell for leukemia-initiating MLL rearrangement events. Although etoposide treatment is sufficient to induce readily detectable MLL rearrangements in primary human CD34+ cells, the majority of cells that gain translocations do not proliferate in culture possibly due to reduced proliferative capacity of most CD34+ cells during normal differentiation [Blood 2005;105:2124]. We characterized the impact of etoposide on primary human long-term repopulating HSC that represent only a minor portion of CD34+ cells. The proliferative capacity of HSC is dramatically increased following both a single and multiple exposures to etoposide as determined by their ability to engraft bone marrow of immune-deficient non-obese diabetic/severe combined immunodeficient mice and to initiate hematopoiesis in long-term initiating cultures. Similar to results in CD34+ cells, a significant proportion of etoposide-treated HSC-derived clones harbored stable MLL rearrangements, including duplications, inversions and translocations. These results indicate HSC are highly susceptible to etoposide-induced and potentially oncogenic rearrangements initiating within MLL, and these HSC are particularly proficient for continued long-term proliferation both in vivo and in vitro.
Department of Pathology, Institute for Cancer Genetics, Columbia University, New York, NY 10032, USA. jl2278@columbia.edu
Jolanta
J
Libura
Maureen
M
Ward
Joanna
J
Solecka
Christine
C
Richardson
D000818:Animals; D018952:Antigens, CD34 / Q000187:drug effects / Q000276:immunology; D000970:Antineoplastic Agents / Q000633:toxicity*; D001483:Base Sequence; D002448:Cell Adhesion / Q000187:drug effects; D002454:Cell Differentiation / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D002869:Chromosome Aberrations / Q000139:chemically induced*; D005047:Etoposide / Q000633:toxicity*; D020869:Gene Expression Profiling; D006412:Hematopoietic Stem Cells / Q000166:cytology / Q000187:drug effects* / Q000276:immunology; D006801:Humans; D008055:Lipids / Q000096:biosynthesis; D051379:Mice; D016688:Mice, Inbred NOD; D016513:Mice, SCID; D018613:Microscopy, Confocal; D008969:Molecular Sequence Data; D051788:Myeloid-Lymphoid Leukemia Protein / Q000235:genetics*; D020411:Oligonucleotide Array Sequence Analysis / Q000379:methods; D016133:Polymerase Chain Reaction / Q000379:methods
D018952:Antigens, CD34; D000970:Antineoplastic Agents; D008055:Lipids; D051788:Myeloid-Lymphoid Leukemia Protein; D005047:Etoposide