Transcription factor c-Maf is a checkpoint that programs macrophages in lung cancer
Min Liu, … , Xiang Zhang, Jun Yan
Min Liu, … , Xiang Zhang, Jun Yan
Published January 16, 2020
Citation Information: J Clin Invest. 2020;130(4):2081-2096. https://doi.org/10.1172/JCI131335.
View: Text | PDF
Research Article Immunology

Transcription factor c-Maf is a checkpoint that programs macrophages in lung cancer

Abstract

Macrophages have been linked to tumor initiation, progression, metastasis, and treatment resistance. However, the transcriptional regulation of macrophages driving the protumor function remains elusive. Here, we demonstrate that the transcription factor c-Maf is a critical controller for immunosuppressive macrophage polarization and function in cancer. c-Maf controls many M2-related genes and has direct binding sites within a conserved noncoding sequence of the Csf-1r gene and promotes M2-like macrophage–mediated T cell suppression and tumor progression. c-Maf also serves as a metabolic checkpoint regulating the TCA cycle and UDP-GlcNAc biosynthesis, thus promoting M2-like macrophage polarization and activation. Additionally, c-Maf is highly expressed in tumor-associated macrophages (TAMs) and regulates TAM immunosuppressive function. Deletion of c-Maf specifically in myeloid cells results in reduced tumor burden with enhanced antitumor T cell immunity. Inhibition of c-Maf partly overcomes resistance to anti–PD-1 therapy in a subcutaneous LLC tumor model. Similarly, c-Maf is expressed in human M2 and tumor-infiltrating macrophages/monocytes as well as circulating monocytes of human non–small cell lung carcinoma (NSCLC) patients and critically regulates their immunosuppressive activity. The natural compound β-glucan downregulates c-Maf expression on macrophages, leading to enhanced antitumor immunity in mice. These findings establish a paradigm for immunosuppressive macrophage polarization and transcriptional regulation by c-Maf and suggest that c-Maf is a potential target for effective tumor immunotherapy.

Authors

Min Liu, Zan Tong, Chuanlin Ding, Fengling Luo, Shouzhen Wu, Caijun Wu, Sabrin Albeituni, Liqing He, Xiaoling Hu, David Tieri, Eric C. Rouchka, Michito Hamada, Satoru Takahashi, Andrew A. Gibb, Goetz Kloecker, Huang-ge Zhang, Michael Bousamra II, Bradford G. Hill, Xiang Zhang, Jun Yan

×

Figure 6

c-Maf is highly expressed in TAMs and knockdown or deficiency of c-Maf reduces TAM immunosuppressive function and tumor-promoting activity.

Options: View larger image (or click on image) Download as PowerPoint
c-Maf is highly expressed in TAMs and knockdown or deficiency of c-Maf r...
(A) c-Maf expression in TAMs was determined by WB (left). Macrophages from different tissues of naive mice and TAMs were assayed for c-Maf mRNA expression by qPCR analysis (right). SpM, Splenic macrophages; PeM, Peritoneal macrophages; AM, alveolar macrophages; IM, Interstitial macrophages. (B) TAMs transfected with c-Maf siRNA (Si c-Maf) or control siRNA (Si C) were assayed for the specific gene mRNA expression. **P < 0.01, ***P < 0.001, ****P < 0.0001 by 2-tailed, unpaired t test. (C) c-Maf– or control siRNA–transfected TAMs were cocultured with splenocytes from OVA-Tg OT-I or OT-II mice in the presence of OVA. IFN-γ–producing T cells were analyzed. Cells were gated on CD4+ or CD8+ cells. Representative dot plots and summarized data are shown (n = 3). *P < 0.05; ****P < 0.0001 by 1-way ANOVA with post hoc t test and Bonferroni’s correction. (D) TAMs were treated with the c-Maf inhibitor Nivalenol (NIV) or vehicle control for 24 hours and the expression of CD115 and CD301 was determined by flow cytometry. Representative histograms and summarized data are shown. ***P < 0.001; ****P < 0.0001 by 1-way ANOVA with Dunnett’s multiple-comparisons test. (E) TAMs were treated with c-Maf inhibitor (100 ng/mL) or vehicle control for 24 hours and then collected and seeded in a Seahorse XF24 analyzer. Real-time OCR, basal and ATP-linked OCR, as well as the OCR/ECAR ratio were determined as described above. Each symbol represents 1 independent experiment with 5 replicates per group in each experiment. Data shown are combined from 2 independent experiments. ***P < 0.001 by 2-tailed, unpaired t test. (F) LLC cells mixed with M2 BMDMs from WT or c-Maf–KO chimeric mice in Matrigel were injected into mice (n = 8) and tumor progression was monitored. **P < 0.01, ***P < 0.001 by 2-way repeated-measures ANOVA with Sidak’s multiple-comparisons test.