SMAD4 promotes TGF-β–independent NK cell homeostasis and maturation and antitumor immunity
Youwei Wang, … , Michael A. Caligiuri, Jianhua Yu
Youwei Wang, … , Michael A. Caligiuri, Jianhua Yu
Published September 5, 2018
Citation Information: J Clin Invest. 2018;128(11):5123-5136. https://doi.org/10.1172/JCI121227.
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Research Article Immunology

SMAD4 promotes TGF-β–independent NK cell homeostasis and maturation and antitumor immunity

Abstract

SMAD4 is the only common SMAD in TGF-β signaling that usually impedes immune cell activation in the tumor microenvironment. However, we demonstrated here that selective deletion of Smad4 in NK cells actually led to dramatically reduced tumor cell rejection and augmented tumor cell metastases, reduced murine CMV clearance, as well as impeded NK cell homeostasis and maturation. This was associated with a downregulation of granzyme B (Gzmb), Kit, and Prdm1 in Smad4-deficient NK cells. We further unveiled the mechanism by which SMAD4 promotes Gzmb expression. Gzmb was identified as a direct target of a transcriptional complex formed by SMAD4 and JUNB. A JUNB binding site distinct from that for SMAD4 in the proximal Gzmb promoter was required for transcriptional activation by the SMAD4-JUNB complex. In a Tgfbr2 and Smad4 NK cell–specific double–conditional KO model, SMAD4-mediated events were found to be independent of canonical TGF-β signaling. Our study identifies and mechanistically characterizes unusual functions and pathways for SMAD4 in governing innate immune responses to cancer and viral infection, as well as NK cell development.

Authors

Youwei Wang, Jianhong Chu, Ping Yi, Wenjuan Dong, Jennifer Saultz, Yufeng Wang, Hongwei Wang, Steven Scoville, Jianying Zhang, Lai-Chu Wu, Youcai Deng, Xiaoming He, Bethany Mundy-Bosse, Aharon G. Freud, Li-Shu Wang, Michael A. Caligiuri, Jianhua Yu

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Figure 5

Smad4 deficiency impairs the maturation of NK cells.

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Smad4 deficiency impairs the maturation of NK cells. (A) Representative...
(A) Representative flow cytometric analysis of KLRG1 in lung NK cells. Gating was performed on the CD3–NKp46+ lymphocyte population in both WT and Smad4ΔNK mice. Results from 1 of 5 pairs of littermate mice with similar data are presented. (B) Cumulative data for KLRG1 expression in NKp46+ cells in the bone marrow, spleen, lungs, liver, blood, and lymph nodes (n = 5). Differences were evaluated between littermates. (C) Representative flow cytometric analysis and cumulative data showing the distribution of CD27 versus CD11b in NK cells from bone marrow, spleen, lungs, liver, blood, and lymph nodes (n = 10). Differences were evaluated between littermates. P values were calculated using a 2-tailed, paired t test. (D) Expression of Gzmb in NK cells at different stages of maturation was analyzed by real-time RT-PCR (n = 6). (E and F) Expression of Prdm1 in NK cells from Smad4+/+ and Smad4ΔNK mice (n = 5) was assessed by real-time RT-PCR (E) and immunoblotting (F). Data are presented as the mean ± SD. The circles and squares on the bar graphs denote data for individual mice. Differences were evaluated between littermates. *P < 0.05 and **P < 0.01, by 2-tailed, paired t test.