Granulocyte-Macrophage Progenitors as Candidate Leukemic Stem Cells in Blast-Crisis CML

TL;DR: Activation of beta-catenin in CML granulocyte-macrophage progenitors appears to enhance the self-renewal activity and leukemic potential of these cells.

Abstract: methods We used fluorescence-activated cell sorting to isolate hematopoietic stem cells, common myeloid progenitors, granulocyte–macrophage progenitors, and megakaryocyte–erythroid progenitors from marrow during several phases of CML and from normal marrow. BCR-ABL, b -catenin , and LEF-1 transcripts were compared by means of a quantitative reverse-transcriptase–polymerase-chain-reaction assay in normal and CML hematopoietic stem cells and granulocyte–macrophage progenitors. Confocal fluorescence microscopy and a lymphoid enhancer factor/T-cell factor reporter assay were used to detect nuclear b -catenin in these cells. In vitro replating assays were used to identify self-renewing cells as candidate leukemic stem cells, and the dependence of self-renewal on b -catenin activation was tested by lentiviral transduction of hematopoietic progenitors with axin, an inhibitor of the b -catenin pathway. results The granulocyte–macrophage progenitor pool from patients with CML in blast crisis and imatinib-resistant CML was expanded, expressed BCR-ABL, and had elevated levels of nuclear b -catenin as compared with the levels in progenitors from normal marrow. Unlike normal granulocyte–macrophage progenitors, CML granulocyte–macrophage progenitors formed self-renewing, replatable myeloid colonies, and in vitro self-renewal capacity was reduced by enforced expression of axin. conclusions Activation of b -catenin in CML granulocyte–macrophage progenitors appears to enhance the self-renewal activity and leukemic potential of these cells.