Suppressing miR-21 activity in tumor-associated macrophages promotes an antitumor immune response
Mahnaz Sahraei, Balkrishna Chaube, Yuting Liu, Jonathan Sun, Alanna Kaplan, Nathan L. Price, Wen Ding, Stanley Oyaghire, Rolando García-Milian, Sameet Mehta, Yana K. Reshetnyak, Raman Bahal, Paolo Fiorina, Peter M. Glazer, David L. Rimm, Carlos Fernández-Hernando, Yajaira Suárez
Mahnaz Sahraei, Balkrishna Chaube, Yuting Liu, Jonathan Sun, Alanna Kaplan, Nathan L. Price, Wen Ding, Stanley Oyaghire, Rolando García-Milian, Sameet Mehta, Yana K. Reshetnyak, Raman Bahal, Paolo Fiorina, Peter M. Glazer, David L. Rimm, Carlos Fernández-Hernando, Yajaira Suárez
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Research Article Angiogenesis Immunology

Suppressing miR-21 activity in tumor-associated macrophages promotes an antitumor immune response

Abstract

microRNA-21 (miR-21) is the most commonly upregulated miRNA in solid tumors. This cancer-associated microRNA (oncomiR) regulates various downstream effectors associated with tumor pathogenesis during all stages of carcinogenesis. In this study, we analyzed the function of miR-21 in noncancer cells of the tumor microenvironment to further evaluate its contribution to tumor progression. We report that the expression of miR-21 in cells of the tumor immune infiltrate, and in particular in macrophages, was responsible for promoting tumor growth. Absence of miR-21 expression in tumor- associated macrophages (TAMs), caused a global rewiring of their transcriptional regulatory network that was skewed toward a proinflammatory angiostatic phenotype. This promoted an antitumoral immune response characterized by a macrophage-mediated improvement of cytotoxic T-cell responses through the induction of cytokines and chemokines, including IL-12 and C-X-C motif chemokine 10. These effects translated to a reduction in tumor neovascularization and an induction of tumor cell death that led to decreased tumor growth. Additionally, using the carrier peptide pH (low) insertion peptide, we were able to target miR-21 in TAMs, which decreased tumor growth even under conditions where miR-21 expression was deficient in cancer cells. Consequently, miR-21 inhibition in TAMs induced an angiostatic and immunostimulatory activation with potential therapeutic implications.

Authors

Mahnaz Sahraei, Balkrishna Chaube, Yuting Liu, Jonathan Sun, Alanna Kaplan, Nathan L. Price, Wen Ding, Stanley Oyaghire, Rolando García-Milian, Sameet Mehta, Yana K. Reshetnyak, Raman Bahal, Paolo Fiorina, Peter M. Glazer, David L. Rimm, Carlos Fernández-Hernando, Yajaira Suárez

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Figure 13

Targeting macrophage miR-21 leads to improved T-cell responses and decreased angiogenesis.

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Targeting macrophage miR-21 leads to improved T-cell responses and decre...
(A) Tumor progression in WT mice injected s.c. with 106 LLCs in the dorsal flank and treated with 1 mg/kg pHLIP anti–miR-21 or pHLIP anti–miR-21-mismatch control on indicated days (n = 6). (B) Tumor progression in WT mice injected s.c. with 106 with miR-21–/– LLC and treated with 1 mg/kg pHLIP anti–miR-21 or pHLIP anti–miR-21-mistmatch on indicated days (n = 6). (C) Representative images of TUNEL and DAPI staining of cross sections of miR-21–/– LLC tumors of WT mice treated as in B. Right: Quantification of % DAPI+ TUNEL+ cells (n = 4 out of 6 randomly selected). (D) Representative images of CD31 staining of cross sections of miR-21–/– LLC tumors of WT mice treated as in B. Right: Quantification of CD31+ vessel-like structures (n = 4 out of 6 randomly selected). (E) qRT-PCR analysis of relative mRNA levels of validated or predicted targets of miR-21 (Il12, Tnf, and Cxcl10) in sorted TAMs (CD45+ CD11b+ MHC II+ F4/80+) of miR-21–/– LLC tumors of WT mice treated as in B (n = 3 out of 6 randomly selected). (F) Right: Flow cytometry analysis of average % of CD8+ TILs expressing GZMB. Left: % CD8+ TILs with extracellular CD107a in miR-21–/– LLC tumors of WT mice treated as in B (n = 4 out 6 randomly selected). (G) Left: Representative images of immunofluorescence costaining of CD68 and CXCL10 in frozen sections of miR-21–/– LLC tumors of WT mice treated as in B. Right: Average of quantification of CXCL10 intensity per CD68+ cell (n = 4 out 6 randomly selected). Results are mean ± SEM. *P < 0.05. (A and B) Two-way ANOVA (time and genotype) with Bonferroni correction, #P < 0.05 individual comparisons. (C–G) Mann-Whitney U test. Scale bars: 70 μm.