Positive feedback between NF-κB and TNF-α promotes leukemia-initiating cell capacity
Yuki Kagoya, … , Yoichiro Iwakura, Mineo Kurokawa
Yuki Kagoya, … , Yoichiro Iwakura, Mineo Kurokawa
Published January 2, 2014
Citation Information: J Clin Invest. 2014;124(2):528-542. https://doi.org/10.1172/JCI68101.
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Research Article Oncology

Positive feedback between NF-κB and TNF-α promotes leukemia-initiating cell capacity

Abstract

Acute myeloid leukemia (AML) is a heterogeneous hematologic malignancy that originates from leukemia-initiating cells (LICs). The identification of common mechanisms underlying LIC development will be important in establishing broadly effective therapeutics for AML. Constitutive NF-κB pathway activation has been reported in different types of AML; however, the mechanism of NF-κB activation and its importance in leukemia progression are poorly understood. Here, we analyzed myeloid leukemia mouse models to assess NF-κB activity in AML LICs. We found that LICs, but not normal hematopoietic stem cells or non-LIC fractions within leukemia cells, exhibited constitutive NF-κB activity. This activity was maintained through autocrine TNF-α secretion, which formed an NF-κB/TNF-α positive feedback loop. LICs had increased levels of active proteasome machinery, which promoted the degradation of IκBα and further supported NF-κB activity. Pharmacological inhibition of the proteasome complex markedly suppressed leukemia progression in vivo. Conversely, enhanced activation of NF-κB signaling expanded LIC frequency within leukemia cell populations. We also demonstrated a strong correlation between NF-κB activity and TNF-α secretion in human AML samples. Our findings indicate that NF-κB/TNF-α signaling in LICs contributes to leukemia progression and provide a widely applicable approach for targeting LICs.

Authors

Yuki Kagoya, Akihide Yoshimi, Keisuke Kataoka, Masahiro Nakagawa, Keiki Kumano, Shunya Arai, Hiroshi Kobayashi, Taku Saito, Yoichiro Iwakura, Mineo Kurokawa

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Figure 3

Autocrine TNF-α secretion maintains constitutive NF-κB activity and confers proliferative advantage in LICs.

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Autocrine TNF-α secretion maintains constitutive NF-κB activity and conf...
(A) Thorough investigation of genes with elevated expression in murine and human LICs compared with that in normal HSPCs in the published gene expression data. (B) TNF-α ELISA in extracellular fluid of normal or leukemic BM (n = 4 each). Error bars indicate SD. (C) TNF-α secretory ability in LICs compared with that of non-LICs and normal GMPs assessed by ELISA in cultured media (n = 4 each). Error bars indicate SD. (D) Immunofluorescence assessment for p65 nuclear translocation in LICs in serum-free culture medium with neutralizing antibody against TNF-α or isotype control. Scale bars: 10 μm. (E) Quantification of p65 nuclear translocation of LICs treated with neutralizing antibody against TNF-α or isotype control assessed by the mean nucleus/cytoplasm intensity ratio. More than 50 cells were scored in each specimen, and the average intensity ratio with SD is shown. (F) Schematic representation of the experiments. BM cells derived from WT or Tnf-knockout mice were transduced with MLL-ENL, MOZ-TIF2, and BCR-ABL plus NUP98-HOXA9 and transplanted into sublethally irradiated mice. (G) Survival curves of mice in the experiments shown in F (n = 7 each). (H) Schematic representation of the experiments. WT or Tnf–/– leukemia cells were secondarily transplanted into WT or Tnf–/– recipient mice. (I) Survival curves of mice in the experiments shown in H (n = 5 each).