NLRC4 suppresses melanoma tumor progression independently of inflammasome activation
Ann M. Janowski, … , Suzanne L. Cassel, Fayyaz S. Sutterwala
Ann M. Janowski, … , Suzanne L. Cassel, Fayyaz S. Sutterwala
Published September 12, 2016
Citation Information: J Clin Invest. 2016;126(10):3917-3928. https://doi.org/10.1172/JCI86953.
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Research Article Immunology

NLRC4 suppresses melanoma tumor progression independently of inflammasome activation

Abstract

Members of the NLR family can assemble inflammasome complexes with the adaptor protein ASC and caspase-1 that result in the activation of caspase-1 and the release of IL-1β and IL-18. Although the NLRC4 inflammasome is known to have a protective role in tumorigenesis, there is an increased appreciation for the inflammasome-independent actions of NLRC4. Here, we utilized a syngeneic subcutaneous murine model of B16F10 melanoma to explore the role of NLRC4 in tumor suppression. We found that NLRC4-deficient mice exhibited enhanced tumor growth that was independent of the inflammasome components ASC and caspase-1. Nlrc4 expression was critical for cytokine and chemokine production in tumor-associated macrophages and was necessary for the generation of protective IFN-γ–producing CD4+ and CD8+ T cells. Tumor progression was diminished when WT or caspase-1–deficient, but not NLRC4-deficient, macrophages were coinjected with B16F10 tumor cells in NLRC4-deficient mice. Finally, examination of human primary melanomas revealed the extensive presence of NLRC4+ tumor-associated macrophages. In contrast, there was a paucity of NLRC4+ tumor-associated macrophages observed in human metastatic melanoma, supporting the concept that NLRC4 expression controls tumor growth. These results reveal a critical role for NLRC4 in suppressing tumor growth in an inflammasome-independent manner.

Authors

Ann M. Janowski, Oscar R. Colegio, Emma E. Hornick, Jennifer M. McNiff, Matthew D. Martin, Vladimir P. Badovinac, Lyse A. Norian, Weizhou Zhang, Suzanne L. Cassel, Fayyaz S. Sutterwala

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Figure 7

NLRC4 is required for IFN-γ+ tumor-infiltrating effector CD4+ and CD8+ T cells.

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NLRC4 is required for IFN-γ+ tumor-infiltrating effector CD4+ and CD8+ T...
(A–I) WT and Nlrc4–/– mice were injected s.c. with 1 × 105 B16F10 cells. (A–D and F–I) On day 14 after inoculation, tumors were made into single-cell suspensions for flow cytometry; the CD45.2+ population was gated on and the frequency of Thy1.2+CD4+ T cells (A), Thy1.2+CD8+ T cells (B), F4/80+ macrophages (F), CD11c+MHCII+ dendritic cells (G), CD11b+GR1+ monocytes (H), and Foxp3+CD4+ regulatory T cells (I) determined. (C and D) Single-cell suspensions of tumor cells were stimulated with PMA and ionomycin, followed by intracellular cytokine staining for IFN-γ. Frequency of CD4+IFN-γ+ T cells (C) and CD8+IFN-γ+ T cells (D) was determined by flow cytometry. Data are representative of at least 3 independent experiments with n ≥ 3 mice per experiment. (E) IFN-γ gene expression in WT and Nlrc4–/– tumors on day 12 after inoculation was determined by qPCR; data are pooled from 3 independent experiments with n = 11 WT and n = 12 Nlrc4–/– mice. Error bars represent SEM. (A–I) *P ≤ 0.05, ***P ≤ 0.001, unpaired 2-tailed Student’s t test.