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 7

IRAK1/4 inhibition impacts the expression levels of signaling molecules critical for T-ALL survival.

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IRAK1/4 inhibition impacts the expression levels of signaling molecules ...
(A) CCRF-CEM cells were treated with IRAK1/4 inhibitor (5 μM) or DMSO for 48 hours, at which point the expression levels of the indicated proteins were determined by Western blot analysis. Average densitometric values (± SD) of 3 independent experiments are shown. *P < 0.05 and **P < 0.01 by Student’s t test. (B) NSG mice (n = 3) were injected with T-ALL cells from 4 different patients, followed by treatment with IRAK1/4 inhibitor (5 mg/kg i.p.) or vehicle control on days 3, 6, and 9. T-ALL cells were collected on day 21, and expression levels of the indicated proteins were determined by Western blot analysis. Change in protein expression levels in DMSO and IRAK1/4 inhibitor–treated samples is shown. (C) Top panel: Representative polysomal A260 profile (of 3 independent experiments) from IRAK1/4 inhibitor– or DMSO-treated CCRF-CEM cells separated by velocity sedimentation on a 10%–50% sucrose gradient. Middle and bottom panels: Distribution of MCL1 and β-actin mRNA as a percentage of total mRNA in CCRF-CEM cells treated with IRAK1/4 inhibitor or DMSO control quantified by RT-PCR from the indicated fractions.