Minimal PU.1 reduction induces a preleukemic state and promotes development of acute myeloid leukemia

Abstract

Modest transcriptional changes caused by genetic or epigenetic mechanisms are frequent in human cancer. Although loss or near-complete loss of the hematopoietic transcription factor PU.1 induces acute myeloid leukemia (AML) in mice, a similar degree of PU.1 impairment is exceedingly rare in human AML; yet moderate PU.1 inhibition is common in AML patients. We assessed functional consequences of modest reduction of PU.1 expression on leukemia development in mice harboring DNA lesions resembling those acquired during human stem cell aging. Heterozygous deletion of an enhancer of PU.1, which resulted in 35% reduction of PU.1 expression, was sufficient to induce myeloid biased preleukemic stem cells and subsequent transformation to AML in a DNA mismatch repair-deficient background. AML progression was mediated by inhibition of expression of a PU.1 cooperating transcription factor, Irf8. Strikingly, we found significant molecular similarities with human myelodysplastic syndrome and AML. This study demonstrates that minimal reduction of a key lineage-specific transcription factor that commonly occurs in human disease is sufficient to initiate cancer development and provides mechanistic insight into the formation and progression of preleukemic stem cells in AML.

Coordination of Myeloid Differentiation with Reduced Cell Cycle Progression by PU.1 Induction of MicroRNAs Targeting Cell Cycle Regulators and Lipid Anabolism

“…Small reductions in PU.1 levels lead to increased proliferation and reduced differentiation of hematopoietic stem cells and myeloid progenitor cells (6,7,10,11). Reintroduction of PU.1 into proliferating cells expressing low levels of PU.1 rapidly induces cell cycle arrest and differentiation (5,7,12).…”

“…Reduced PU.1 expression promotes increased cell cycle entry in hematopoietic stem cells (10). Minimal reductions in PU.1 levels are sufficient to induce a preleukemic state with increased proliferation of myeloid progenitors, leading to AML (11). Spi1 BN/BN mice (also called BN mice) express PU.1 at ϳ20% of normal levels, do not generate mature macrophages, and have increased proliferation of myeloid progenitors in the spleen (6,12).…”

Pharmacological inhibition of the transcription factor PU.1 in leukemia

“…Control (shCtrl) or shPU.1 sequences were cloned under an H1 promoter and inserted into the lentiviral vector pRRLsin-PGK-eGFP-WPRE (provided by Hana Raslova, Institut Gustave Roussy, Villejuif, France). PU.1 overexpression was performed using the lentiviral vector PCAD-PU.1-IRES-GFP or GFP alone as previously described (18). All viruses were produced using the 293T cell line.…”

“…On the basis of the general structural features of our initial PU.1 inhibitors (23), we designed and prepared a focused library of larger derivatives for screening using the solution and cellular analytical methods (vide infra). DB2115 and DB2313 were selected itself; how ever, it leads to myeloid bias in (preleukemic) stem cells and MDS and AML development in combination with cooperating events (18).…”

High expression of PU.1 is associated with Her‑2 and shorter survival in patients with breast cancer

“…In classical Hodgkin lymphoma cells, PU.1 is a potent tumor suppressor, and the induction of PU.1 expression is a potential therapeutic option for patients with classical Hodgkin lymphoma (13). It has also been recently reported that minimal PU.1 reduction induces a preleukemic state and promotes development of acute myeloid leukemia (14). PU.1 reduces the transcriptional activity of the p53 tumor suppressor family and thus inhibits the activation of genes important for cell cycle regulation and apoptosis (15).…”