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 5

Absence of NLRC4 in macrophages alters the tumor cytokine and chemokine milieu.

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Absence of NLRC4 in macrophages alters the tumor cytokine and chemokine ...
(A–F) WT and Nlrc4–/– mice were injected s.c. with 1 × 105 B16F10 cells. On day 12 after inoculation, total RNA was isolated from homogenized tumors and used to determine cytokine and chemokine expression via quantitative qPCR utilizing a PCR array. Selected genes from the array are displayed; data are pooled from 3 separate experiments (n = 3 mice per group). (G and H) WT and Nlrc4–/– mice were injected s.c. with 1 × 105 B16F10 cells; 14 days after inoculation, tumors were harvested, pooled, and FACS sorted based on CD45.2 and F4/80 staining. RNA was isolated from CD45.2- and CD45.2+F4/80+ cells and used to determine Cxcl9, Cxcl10, Cxcl13, and Cxcl16 expression by qPCR; data are representative of 2 independent experiments with n ≥ 5 pooled tumors per group. (I) WT and Nlrc4–/– BMDMs were challenged for 9 hours with B16F10 whole tumor homogenate. Cxcl9, Cxcl10, and Cxcl13 expression was determined by qPCR. Data are pooled from 3 independent experiments, and fold change in gene expression is relative to unstimulated samples. (J and K) WT and Nlrc4–/– BMDMs were challenged with 50 ng/ml LPS, 50 μg/ml LTA, 100 ng/ml FSL-1, and 1 μg/ml Pam3CSK4. Twenty hours later, supernatants were collected and levels of IL-6 (J) and IL-12p40 (K) determined by ELISA; data are representative of 3 independent experiments. (A–F and I) Error bars represent SEM. (J and K) Error bars represent SD. (I–K) *P ≤ 0.05, **P ≤ 0.01, and ***P ≤ 0.001, unpaired 2-tailed Student’s t test.