Comparative genomics reveals multistep pathogenesis of E2A-PBX1 acute lymphoblastic leukemia
Jesús Duque-Afonso, … , Masayuki Iwasaki, Michael L. Cleary
Jesús Duque-Afonso, … , Masayuki Iwasaki, Michael L. Cleary
Published August 24, 2015
Citation Information: J Clin Invest. 2015;125(9):3667-3680. https://doi.org/10.1172/JCI81158.
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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 3

Expression of pre-BCR components in E2A-PBX1 leukemic blasts determines a phenotype very similar to that of human pre-BCR+ leukemias.

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Expression of pre-BCR components in E2A-PBX1 leukemic blasts determines ...
(A) Pie chart represents the proportion of analyzed leukemias (n = 16) with a productive or unproductive VDJ rearrangement. (B) Bcl6 expression was assessed by qPCR of sorted Lin–CD19+CD43+ cells from BM leukemias (n = 24). Leukemias were compared depending on their pre-BCR status. Horizontal bars denote the mean. (C) PLCγ2 phosphorylation was analyzed by phospho-flow after pre-BCR stimulation using polyclonal anti-IgM and H2O2 for 30 minutes (15). Pre-BCR+ and pre-BCR– results of 2 analyzed leukemias from each group are shown. Pervanadate was used as a positive control. (D) BM leukemic cells were cultured in the presence of increasing concentrations of dasatinib. Colonies were enumerated after 7 days. (E) E2A-PBX1 leukemia cells from pre-BCR+ leukemia were transplanted into sublethally irradiated secondary recipients. Mice were treated with vehicle (n = 5) or dasatinib (100 μg i.p. daily, n = 4) for 20 days. Statistical analysis was performed by log-rank test. BMT, BM transplantation. (F) Pre-BCR– leukemias were transduced retrovirally to ectopically express empty vector (EV) or functional μ heavy chain (μ HC). Results of a representative of 2 transduced leukemias are shown. Western blot shows expression of μ heavy chain and GAPDH as a loading control. (G) Cytoplasmic IgM (cyIgM) and surface VPREB (sVPREB) were assessed by flow cytometry. (H) Transduced pre-BCR– leukemias were cultured at increasing concentrations of dasatinib. Colonies were enumerated after 5 days, and results are expressed as the mean ± SEM of 3 independent experiments. Statistical analysis was performed using the F test.