HoxA10 Regulates Transcription of the Gene Encoding Transforming Growth Factor β2 (TGFβ2) in Myeloid Cells

Abstract

HoxA10 is a homeodomain transcription factor that is maximally expressed in myeloid progenitor cells. HoxA10 is overexpressed in a poor prognosis subset of human acute myeloid leukemia (AML) and in vivo overexpression of HoxA10 in murine bone marrow induces myeloid leukemia. HoxA10 contributes to myeloid progenitor expansion and differentiation block, but few target genes have been identified that explain the influence of HoxA10 on these processes. The current study identifies the gene encoding transforming growth factor ␤2 (TGF␤2) as a HoxA10 target gene. We found that HoxA10 activated TGF␤2 transcription by interacting with tandem cis elements in the promoter. We also determined that HoxA10 overexpression in myeloid progenitor cells increased Tgf␤2 production by the cells. Tgf␤2 stimulates proliferation of hematopoietic stem and progenitor cells. Therefore, these studies identified autocrine stimulation of myeloid progenitors by Tgf␤2 as one mechanism by which HoxA10 expands this population. Because HoxA proteins had not been previously known to influence expression of pro-proliferative cytokines, this has implications for understanding molecular mechanisms involved in progenitor expansion and the pathobiology of AML.

The Leukemia-associated Mll-Ell Oncoprotein Induces Fibroblast Growth Factor 2 (Fgf2)-dependent Cytokine Hypersensitivity in Myeloid Progenitor Cells

“…Bi-potential granulocyte/monocyte progenitor cells (GMPs) were cultured (2 ϫ 10 5 cells/ml) for 48 h in DME media supplemented with 10% fetal calf serum, 1% pen-strep, 10 ng/ml murine GM-CSF (R & D Systems Inc., Minneapolis, MN), 10 ng/ml murine recombinant IL-3 (R & D Systems), and 100 ng/ml SCF (R & D Systems) followed by separation of CD34 ϩ cells using the Miltenyi magnetic bead system (Miltenyi Biotechnology, Auburn, CA) (18,23,26). Some cells were CD34-separated after 24 h under these conditions followed by 24 h of differentiation in DME supplemented with 10% fetal calf serum, 1% pen-strep, 20 ng/ml G-CSF (R & D Systems) and 10 ng/ml IL3.…”

“…Other cells were incubated with the Fgf-R1 inhibitor, PD173074 (Cayman Chemical, Ann Arbor, MI). Cell proliferation was determined by incorporation of [ 3 H]thymidine (23,26).…”

“…Some cells were incubated with Fgf2 blocking antibody (or control antibody) or Fgf-R1 inhibitor (or buffer control). Cell proliferation was determined as above (23,26).…”

“…Bone marrow mononuclear cells were cultured for 24 h in 10 ng/ml GM-CSF, 10 ng/ml IL3, and 100 ng/ml SCF. Cells were transduced by incubation with retroviral supernatant supplemented with Polybrene (6 g/ml) as described (18,23,26). Transduced cells were selected for 48 h in puromycin followed by CD34 selection and culture in GM-CSF, IL3, and SCF (as above).…”

“…We used chromatin immunoprecipitation-based screening techniques to identify HoxA10 target genes that might be relevant to leukemogenesis (21)(22)(23)(24)(25)(26). In these studies we identified the gene encoding fibroblast growth factor 2 (Fgf2, or basic Fgf) as a HoxA10 target gene (26).…”