Comparative genomics reveals multistep pathogenesis of E2A-PBX1 acute lymphoblastic leukemia
Jesús Duque-Afonso, Jue Feng, Florian Scherer, Chiou-Hong Lin, Stephen H.K. Wong, Zhong Wang, Masayuki Iwasaki, Michael L. Cleary
Jesús Duque-Afonso, Jue Feng, Florian Scherer, Chiou-Hong Lin, Stephen H.K. Wong, Zhong Wang, Masayuki Iwasaki, Michael L. Cleary
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Research Article Oncology

Comparative genomics reveals multistep pathogenesis of E2A-PBX1 acute lymphoblastic leukemia

Abstract

Acute lymphoblastic leukemia (ALL) is the most common childhood cancer; however, its genetic diversity limits investigation into the molecular pathogenesis of disease and development of therapeutic strategies. Here, we engineered mice that conditionally express the E2A-PBX1 fusion oncogene, which results from chromosomal translocation t(1;19) and is present in 5% to 7% of pediatric ALL cases. The incidence of leukemia in these mice varied from 5% to 50%, dependent on the Cre-driving promoter (Cd19, Mb1, or Mx1) used to induce E2A-PBX1 expression. Two distinct but highly similar subtypes of B cell precursor ALLs that differed by their pre–B cell receptor (pre-BCR) status were induced and displayed maturation arrest at the pro-B/large pre–B II stages of differentiation, similar to human E2A-PBX1 ALL. Somatic activation of E2A-PBX1 in B cell progenitors enhanced self-renewal and led to acquisition of multiple secondary genomic aberrations, including prominent spontaneous loss of Pax5. In preleukemic mice, conditional Pax5 deletion cooperated with E2A-PBX1 to expand progenitor B cell subpopulations, increasing penetrance and shortening leukemia latency. Recurrent secondary activating mutations were detected in key signaling pathways, most notably JAK/STAT, that leukemia cells require for proliferation. These data support conditional E2A-PBX1 mice as a model of human ALL and suggest targeting pre-BCR signaling and JAK kinases as potential therapeutic strategies.

Authors

Jesús Duque-Afonso, Jue Feng, Florian Scherer, Chiou-Hong Lin, Stephen H.K. Wong, Zhong Wang, Masayuki Iwasaki, Michael L. Cleary

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Figure 4

E2A-PBX1 confers self-renewal properties and impedes differentiation of preleukemic B cell progenitors.

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E2A-PBX1 confers self-renewal properties and impedes differentiation of ...
(A) Peripheral blood B cell populations were assessed by flow cytometry at the indicated ages in control and preleukemic (#1 and #2) mice. (B) Bar graphs summarize B cell subset quantification following culture of prospectively isolated progenitor B cells from Tg(E2A-PBX1) Cd19-Cre preleukemic (n = 3) or control mice (n = 3). (C) Flow cytometric analysis at the end of culture for representative control and Tg(E2A-PBX1) Cd19-Cre mice. Bar graphs summarize cell proliferation. (D) WT (n = 4) and preleukemic Tg(E2A-PBX1) Cd19-Cre mice (n = 4) were sublethally irradiated and assessed by flow cytometry for B cell progenitor recovery at 2, 4, 6, and 8 weeks. Results at 6 weeks showed markedly skewed BM repopulation by GFP+ versus control GFP– pro-B cells. Similar results were found at the different time points analyzed. (E) BM CD19+ cells (equally composed of GFP+ and GFP– cells) isolated from Tg(E2A-PBX1) Cd19-Cre preleukemic mice were transplanted into sublethally irradiated NSG mice (n = 5). GFP+ B cell progenitors had a substantially enhanced engraftment and/or expansion advantage at the analyzed time points (2, 4, and 6 weeks), as shown by flow cytometry. (F) The percentage of GFP+ cells in Lin–CD19+CD43+ cells from preleukemic Tg(E2A-PBX1) Cd19-Cre (n = 8) and Tg(E2A-PBX1) Mb1-Cre (n = 8) mice was analyzed by flow cytometry. Horizontal bars denote the mean. Statistical analysis was performed using a 2-sided Student’s t test. (G) Lin–CD19+CD43+GFP+ cells from the previous experiment were sorted and cultured in methylcellulose. CFU were enumerated after 7 days. Horizontal bars denote the mean. Statistical analysis was performed using a 2-sided Student’s t test.