Overexpression of the signaling coordinator GAB2 can play an important role in acute myeloid leukemia progression
Michael H. Kramer, Stephanie N. Richardson, Yang Li, Tiankai Yin, Nichole M. Helton, Daniel R. George, Michelle Cai, Sai Mukund Ramakrishnan, Casey D.S. Katerndahl, Christopher A. Miller, Timothy J. Ley
Michael H. Kramer, Stephanie N. Richardson, Yang Li, Tiankai Yin, Nichole M. Helton, Daniel R. George, Michelle Cai, Sai Mukund Ramakrishnan, Casey D.S. Katerndahl, Christopher A. Miller, Timothy J. Ley
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Research Article Genetics Oncology

Overexpression of the signaling coordinator GAB2 can play an important role in acute myeloid leukemia progression

Abstract

Mutations that initiate acute myeloid leukemia (AML) can cause clonal expansion without transformation (clonal hematopoiesis). Cooperating mutations, usually in signaling genes, are needed to cause overt disease, but these may require a specific fitness state to be tolerated. Here, we show that nearly all AMLs arising in a mouse model expressing 2 common AML-initiating mutations (Dnmt3aR878H and Npm1cA) acquired a single copy amplification of chromosome 7 (chr7), followed by activating mutations in signaling genes. We show that overexpression of a single gene on chr7 (Gab2, which coordinates signaling pathways) was tolerated in the presence of the Npm1cA mutation, could accelerate the development of AML, and was important for the survival of fully transformed AML cells. GAB2 is likewise overexpressed in many human AMLs with mutations in NPM1 and/or signaling genes, and also in acute promyelocytic leukemia initiated by PML::RARA; the PML::RARA fusion protein may activate GAB2 by directly binding to its 5′ flanking region. A similar pattern of GAB2 overexpression preceding mutations in signaling genes has been described in other human malignancies. GAB2 overexpression may represent an oncogene-driven adaptation that facilitates the action of signaling mutations, suggesting an important (and potentially targetable) missing link between the initiating and progression mutations associated with AML.

Authors

Michael H. Kramer, Stephanie N. Richardson, Yang Li, Tiankai Yin, Nichole M. Helton, Daniel R. George, Michelle Cai, Sai Mukund Ramakrishnan, Casey D.S. Katerndahl, Christopher A. Miller, Timothy J. Ley

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Figure 2

Retroviral overexpression of Gab2 causes the expansion of HSPCs and accelerates the development of AML in the presence of Npm1cA and Dnmt3aR878H mutations.

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Retroviral overexpression of Gab2 causes the expansion of HSPCs and acce...
(A) Retroviral vectors were transduced into lineage-depleted primary murine CD45.2+ bone marrow cells to create a mixed population of transduced (GFP+) and untransduced (GFP–) cells. Cells were split into 2 groups, with 1 maintained in vitro and 1 transplanted into CD45.1+ recipient mice. The fraction of GFP+ cells was measured over time using flow cytometry. This illustration was created in BioRender. (B) Overexpression of Gab2 in Dnmt3aR878H/+ × Npm1cA/+ marrow shows a growth advantage in vitro, with GFP+ (Gab2-overexpressing) cells expanding over time. No effect was observed in cells transduced with the IRES-eGFP or Pak1-IRES-eGFP vectors. Representative data from 1 of 4 biological replicates are shown. (C and D) Overexpression of Gab2 in (C) WT or (D) Dnmt3aR878H/+ bone marrow caused a selective disadvantage compared with IRES-eGFP vector–only cells or untransduced cells. Data shown in C and D are representative of 1 of 2 biological replicates. (E) Overexpression of Gab2 in Npm1cA/+ bone marrow did not show a marked advantage or disadvantage compared with IRES-eGFP vector or untransduced cells. Data shown are representative of 1 of 2 biological replicates. (F) GFP positivity of CD45.2+ peripheral WBCs was measured by flow cytometry in CD45.1 mice transplanted with retrovirally transduced cells of the indicated genotypes. Dots show mean values at each time point, and error bars show SD. P values were calculated at each time point for the Gab2-IRES-eGFP curve using a 2-sided, 1-sample t test for change from baseline compared with a null hypothesis of a mean change of 0, with Benjamini-Hochberg multiple hypothesis correction. (G) Mice of the indicated genotypes were monitored for AML development. Retroviral overexpression of Gab2 in the Dnmt3aR878H/+ × Npm1cA/+ background significantly accelerated AML development. P values were determined by pairwise log-rank test.