title: Frequency of acute myeloid leukaemia-associated mouse chromosome 2 deletions in X-ray exposed immature haematopoietic progenitors and stem cells.
abstract: Exposure to ionising radiation can lead to an increased risk of cancer, particularly leukaemia. In radiation-induced acute myeloid leukaemia (rAML), a partial hemizygous deletion of mouse chromosome 2 is a common feature in several susceptible strains. The deletion is an early event detectable 24h after exposure in bone marrow cells using cytogenetic techniques. Expanding clones of bone marrow cells with chromosome 2 deletions can be detected less than a year after exposure to ionising radiation in around half of the irradiated mice. Ultimately, 15-25% of exposed animals develop AML. It is generally assumed that leukaemia originates in an early progenitor cell or haematopoietic stem cell, but it is unknown whether the original chromosome damage occurs at a similar frequency in committed progenitors and stem cells. In this study, we monitored the frequency of chromosome 2 deletions in immature bone marrow cells (Lin(-)) and haematopoietic stem cells/multipotent progenitor cells (LSK) by several techniques, fluorescent in situ hybridisation (FISH) and through use of a reporter gene model, flow cytometry and colony forming units in spleen (CFU-S) following ex vivo or in vivo exposure. We showed that partial chromosome 2 deletions are present in the LSK subpopulation, but cannot be detected in Lin(-) cells and CFU-S12 cells. Furthermore, we transplanted irradiated Lin(-) or LSK cells into host animals to determine whether specific irradiated cell populations acquire an increased proliferative advantage compared to unirradiated cells. Interestingly, the irradiated LSK subpopulation containing cells carrying chromosome 2 deletions does not appear to repopulate as well as the unirradiated population, suggesting that the chromosomal deletion does not provide an advantage for growth and in vivo repopulation, at least at early stages following occurrence.
authors.affiliation: Cancer Genetics and Cytogenetics Group, Biological Effects Department, Centre for Radiation Chemical and Environmental Hazards, Public Health England, Didcot, Oxfordshire OX11 ORQ, United Kingdom.
authors.forename: C-H
authors.initials: CH
authors.lastname: Olme
authors.forename: N
authors.initials: N
authors.lastname: Brown
authors.forename: R
authors.initials: R
authors.lastname: Finnon
authors.forename: S D
authors.initials: SD
authors.lastname: Bouffler
authors.forename: C
authors.initials: C
authors.lastname: Badie
mesh_terms: D000818:Animals; D000950:Antigens, Ly / Q000378:metabolism; D001853:Bone Marrow / Q000378:metabolism / Q000473:pathology*; D019070:Cell Lineage; D002478:Cells, Cultured; D002872:Chromosome Deletion; D002875:Chromosomes / Q000235:genetics*; D005434:Flow Cytometry; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006412:Hematopoietic Stem Cells / Q000378:metabolism / Q000473:pathology*; D018189:Immunomagnetic Separation; D017404:In Situ Hybridization, Fluorescence; D015470:Leukemia, Myeloid, Acute / Q000235:genetics* / Q000473:pathology; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D008808:Mice, Inbred CBA; D019009:Proto-Oncogene Proteins c-kit / Q000378:metabolism; D014965:X-Rays
chemical_list: D000950:Antigens, Ly; C074650:Ly6a protein, mouse; D008565:Membrane Proteins; D049452:Green Fluorescent Proteins; D019009:Proto-Oncogene Proteins c-kit
keywords: 7-AAD; 7-aminoactinomycin D; BAC-FISH; BMCs; CFU-S12; CMP; CSC; Chromosome deletion; GFP; HSC; IMDM; IR; Iscove's modified Dulbecco's medium; LSK; Lin(−); Lin(−) Sca-1(+) c-Kit(+); MEP; MMP; Mouse model; Myeloid leukaemia; Radiation; Sfpi1(GFP/+); Sfpi1(GFP/GFP); Sfpi1/PU.1; Stem cells; bacterial artificial chromosome-fluorescent in situ hybridisation; bone marrow cells; cancer stem cell; colony forming unit spleen on day 12; common myeloid progenitor; del2; green fluorescent protein; haematopoietic stem cell; heterozygous for the Sfpi1-GFP reporter gene; homozygous for the Sfpi1-GFP reporter gene; interstitial deletion of chromosome 2; ionising radiation; lineage negative immature bone marrow cells; multi-potent progenitor; myeloid-erythroid progenitor; rAML; radiation-induced acute myeloid leukaemia