Impaired DNA Replication within Progenitor Cell Pools Promotes Leukemogenesis
Figure 2
The Expression of Bcr-Abl Provides a Competitive Advantage to DKO Progenitors
Purified c-Kit+ cells from either E2f1+2+ or DKO donor mice (pooled sets of littermates) were transduced with MSCV-expressing p190 Bcr-Abl and GFP or GFP only (vector), and transplanted into lethally irradiated BALB/c recipients. The same pool of Bcr-Abl transduced DKO progenitors was either mixed with untransduced E2f1+2+ competitor progenitors (“DKO + E2F1+2+ competitors”) or with untransduced DKO progenitors (“DKO”). Bcr-Abl-transduced E2f1+2+ progenitors similarly were mixed with untransduced E2f1+2+ progenitors (“E2F1+2+”). Specifically, each recipient received 2.5 × 105 untransduced whole BM cells combined with 1.2 × 106 MSCV-transduced c-Kit+ cells. Initial infection efficiencies measured for the whole c-Kit-enriched population were 5.1% and 3.75% among E2f1+2+, and 4.73% and 3.4% among DKO progenitors for Bcr-Abl and vector, respectively. Tail blood isolated at 3 wk post-BMT was analyzed for the expression of GFP and B220 (upper bar graph; B-cell lineage) or GR-1 (lower bar graph; myeloid lineage) by flow cytometry.
(A) Each bar represents data from five mice with standard error (SE) indicated, and statistical significance determined using Student's unpaired t-test (for all figures in this paper).
(B) Representative flow cytometric profiles of peripheral B cells are shown, with the percentages of peripheral blood cells expressing both GFP and B220 indicated.
(C) BM cells were analyzed by flow cytometry for the expression of Lin antigens, Sca1, Flk2 and GFP. Lin antigens included GR-1, B220, Ter119, CD3, and CD4. Cells analyzed in the profiles shown were gated as Lin− Flk2−. The upper right quadrant represents progenitor-enriched Lin− Flk2− Sca1+ cells expressing either Bcr-Abl or vector, and the percentages of Lin− Flk2− cells that express Sca1 and/or GFP are indicated. In multiple experiments, recipients of Bcr-Abl transduced E2f1+2+ cells exhibited reduced percentages of GFP− Lin− Flk2− Sca1+ cells (the upper left quadrant) relative to vector controls, a phenomenon that we do not currently understand.