Inhibition of IRAK1/4 sensitizes T cell acute lymphoblastic leukemia to chemotherapies
Zhaoyang Li, … , Patrick Brown, Eduardo Davila
Zhaoyang Li, … , Patrick Brown, Eduardo Davila
Published February 2, 2015
Citation Information: J Clin Invest. 2015;125(3):1081-1097. https://doi.org/10.1172/JCI75821.
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Research Article Oncology

Inhibition of IRAK1/4 sensitizes T cell acute lymphoblastic leukemia to chemotherapies

Abstract

Signaling via the MyD88/IRAK pathway in T cells is indispensable for cell survival; however, it is not known whether this pathway functions in the progression of T acute lymphoblastic leukemia (T-ALL). Here, we determined that compared with thymic and peripheral T cells, T-ALL cells from patients have elevated levels of IRAK1 and IRAK4 mRNA as well as increased total and phosphorylated protein. Targeted inhibition of IRAK1 and IRAK4, either with shRNA or with a pharmacological IRAK1/4 inhibitor, dramatically impeded proliferation of T-ALL cells isolated from patients and T-ALL cells in a murine leukemia model; however, IRAK1/4 inhibition had little effect on cell death. We screened several hundred FDA-approved compounds and identified a set of drugs that had enhanced cytotoxic activity when combined with IRAK inhibition. Administration of an IRAK1/4 inhibitor or IRAK knockdown in combination with either ABT-737 or vincristine markedly reduced leukemia burden in mice and prolonged survival. IRAK1/4 signaling activated the E3 ubiquitin ligase TRAF6, increasing K63-linked ubiquitination and enhancing stability of the antiapoptotic protein MCL1; therefore, IRAK inhibition reduced MCL1 stability and sensitized T-ALL to combination therapy. These studies demonstrate that IRAK1/4 signaling promotes T-ALL progression through stabilization of MCL1 and suggest that impeding this pathway has potential as a therapeutic strategy to enhance chemotherapeutic efficacy.

Authors

Zhaoyang Li, Kenisha Younger, Ronald Gartenhaus, Ann Mary Joseph, Fang Hu, Maria R. Baer, Patrick Brown, Eduardo Davila

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Figure 2

IRAK1/4 signaling inhibition impedes T-ALL proliferation.

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IRAK1/4 signaling inhibition impedes T-ALL proliferation. (A) IRAK4/1 in...
(A) IRAK4/1 inhibitor effects on the proliferation of various malignant T cell lines. Cells were cultured in the presence of IRAK1/4 inhibitor (0–10 μM) or control (DMSO), and proliferation was measured 72 hours later. Data are representative of 3 independent experiments, and the average OD490 (± SD) of triplicate readings is shown. (B) Patient T-ALL cells were cultured in the presence of control (DMSO) or IRAK1/4 inhibitor (0–12.5 μM), and proliferation was determined by measuring 3[H]thymidine incorporation. Data represent the average of triplicate readings (± SD) and are representative of 2 independent experiments, each yielding identical trends. *P <0.05 by Student’s t test (A and B). (C) Levels of the indicated proteins were examined in CCRF-CEM T-ALL cells after treatment with IRAK1/4 inhibitor (2.5 μM) or DMSO for 48 hours. (D) T-ALL cells were transiently transfected with the indicated plasmids. Transfected cells were sorted by flow cytometry according to GFP expression, and proliferation of CCRF-CEM and Jurkat cells was determined according to 3[H]thymidine uptake (top panels). Average cpm (± SD) of triplicate readings is shown. *P < 0.05 versus control shRNA by Student’s t test. Knockdown efficiency was examined by Western blotting. Data are representative of 3 independent experiments.