A stress-responsive enhancer induces dynamic drug resistance in acute myeloid leukemia
Mark S. Williams, … , Fabrizio Simeoni, Tim C.P. Somervaille
Mark S. Williams, … , Fabrizio Simeoni, Tim C.P. Somervaille
Published November 26, 2019
Citation Information: J Clin Invest. 2020;130(3):1217-1232. https://doi.org/10.1172/JCI130809.
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A stress-responsive enhancer induces dynamic drug resistance in acute myeloid leukemia

Abstract

The drug efflux pump ABCB1 is a key driver of chemoresistance, and high expression predicts treatment failure in acute myeloid leukemia (AML). In this study, we identified and functionally validated the network of enhancers that controls expression of ABCB1. We show that exposure of leukemia cells to daunorubicin activated an integrated stress response–like transcriptional program to induce ABCB1 through remodeling and activation of an ATF4-bound, stress-responsive enhancer. Protracted stress primed enhancers for rapid increases in activity following re-exposure of cells to daunorubicin, providing an epigenetic memory of prior drug treatment. In primary human AML, exposure of fresh blast cells to daunorubicin activated the stress-responsive enhancer and led to dose-dependent induction of ABCB1. Dynamic induction of ABCB1 by diverse stressors, including chemotherapy, facilitated escape of leukemia cells from targeted third-generation ABCB1 inhibition, providing an explanation for the failure of ABCB1 inhibitors in clinical trials. Stress-induced upregulation of ABCB1 was mitigated by combined use of the pharmacologic inhibitors U0126 and ISRIB, which inhibit stress signaling and have potential for use as adjuvants to enhance the activity of ABCB1 inhibitors.

Authors

Mark S. Williams, Fabio M.R. Amaral, Fabrizio Simeoni, Tim C.P. Somervaille

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Figure 1

Resistance to daunorubicin due to stereotypical induction of ABCB1.

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Resistance to daunorubicin due to stereotypical induction of ABCB1. (A) ...
(A) Outline of experiment. (B) Dose-response curves for sensitive and resistant lines following 72 hours of treatment with the indicated doses of daunorubicin. (C) Bar chart shows mean ± SEM IC50 values for daunorubicin for all lines (n = 4). ***P < 0.001 by unpaired t test. (D) Volcano plot shows differential gene expression between sensitive (K562_S1–3) and resistant (K562_R1–3) cell lines. (E) ABCB1 is the most highly upregulated gene in each resistant line compared with its sensitive parental line. (F) Mean ± SEM fold increase in ABCB1 expression, as determined by quantitative PCR (n = 4). ***P < 0.001 by unpaired t test. (G) Mean ± SEM fold increase in ABCB1 median fluorescence intensity (MFI), as determined by flow cytometry (n = 3). ***P < 0.001 by unpaired t test. (H and I) Representative flow histograms show calcein AM retention in the indicated lines in the presence or absence of verapamil 40 μM (H) or tariquidar 50 nM (I). (J) Summary of calcein AM retention data for all 3 line pairs for verapamil and tariquidar (n = 3).