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 6

NLRC4 regulates STAT3 and p38 MAPK signaling in the tumor microenvironment.

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NLRC4 regulates STAT3 and p38 MAPK signaling in the tumor microenvironme...
(A and B) B16F10 tumors from WT and Nlrc4–/– mice at day 14 after inoculation were homogenized and immunoblotted for phospho-STAT3 and STAT3 (A), phospho-p38 MAPK and p38 MAPK (B), and GAPDH (A and B). Each lane represents a tumor from an individual mouse. (A and B) Densitometry of the ratio of phosphorylated to total protein is shown. (C) WT and Nlrc4–/– BMDMs were challenged for 4, 5, 6, 7, and 8 hours with 50 ng/ml LPS. Cell lysates were immunoblotted with antibodies against phospho-STAT3, STAT3, and GAPDH. (D) WT and Nlrc4–/– BMDMs were challenged for 15, 30, 60, and 90 minutes with 50 ng/ml LPS. Cell lysates were immunoblotted with antibodies against phospho-p38 MAPK, p38 MAPK, and GAPDH. (E) WT and Nlrc4–/– BMDMs were challenged for 5, 10, 15, 30, and 60 minutes with 10 ng/ml recombinant IL-6. Cell lysates were immunoblotted with antibodies against phospho-STAT3, STAT3, and GAPDH. (C–E) Data are representative of 3 independent experiments. (A and B) *P ≤ 0.05, unpaired 2-tailed Student’s t test.