Targeted delivery of miR-99b reprograms tumor-associated macrophage phenotype leading to tumor regression

Abstract

BackgroundAccumulating evidence has shown that tumor-associated macrophages (TAMs) play a critical role in tumor progression. Targeting TAMs is a potential strategy for tumor immunotherapy. However, the mechanism underlying the TAM phenotype and function needs to be resolved. Our previous studies have demonstrated that miR-125a can reverse the TAM phenotype toward antitumor. Meanwhile, we have found that miR-125a and miR-99b cluster in the first intron of the same host gene, and are transcribed simultaneously in bone marrow-derived macrophages (BMDMs) following LPS+IFNγ stimulation. However, it remains unclear whether miR-99b by itself can exert an antitumor effect by regulating macrophage phenotype.MethodsmiR-99b and/or miR-125a were delivered into TAMs of orthotopic hepatocellular carcinoma (HCC) or subcutaneous Lewis lung cancer (LLC) mice. The effect of treatment was evaluated by live imaging, TUNEL staining and survival tests. The phenotype of the immune cells was determined by qRT-PCR, ELISA, western blot and FACS. The capability of miR-99b-mediated macrophage phagocytosis and antigen presentation was detected by FACS and immunofluorescence staining. The underlying molecular mechanism was examined by qRT-PCR, reporter assay and western blot, and further verified in the tumor model. The expression of miR-99b and its target genes was determined in TAMs sorted from tumor and adjacent tissues in patients with liver cancer.ResultsTargeted delivery of miR-99b and/or miR-125a into TAMs significantly impeded the growth of HCC and LLC, especially after miR-99b delivery. More importantly, the delivery of miR-99b re-educated TAM toward antitumor phenotype with enhanced immune surveillance. Further investigation of mechanisms showed that macrophage-specific overexpression of miR-99b promoted M1 while suppressing M2 macrophage polarization by targeting κB-Ras2 and/or mTOR, respectively. miR-99b-overexpressed M1 macrophage was characterized by stronger capability of phagocytosis and antigen presentation. Additionally, delivery of simTOR or siκB-Ras2 into TAMs inhibited miR-99b antagomir-triggered tumor growth. Finally, miR-99b expression was lower in TAMs of patients with liver cancer than that in adjacent tissues, while the expression of κB-Ras2 and mTOR was reversed.ConclusionsOur results reveal the mechanism of miR-99b-mediated TAM phenotype, indicating that TAM-targeted delivery of miR-99b is a potential strategy for cancer immunotherapy.

MFG-E8 regulated by miR-99b-5p protects against osteoarthritis by targeting chondrocyte senescence and macrophage reprogramming via the NF-κB pathway

“…In acute lung injury, NF-κB (p65) promotion of miR-99b-5p accelerates the disease progression 34 . In tumor-associated phenotypes, miR-99b-5p promotes M1 while suppressing M2 subtype polarization 35 . Moreover, overexpression of miR-99b-5p downregulates protein synthesis in muscle 36 .…”

Therapeutic Targeting of MicroRNAs in the Tumor Microenvironment

“…In a mouse model of lung cancer, the combinatorial delivery of the pro-inflammatory miR-125b mimic together with wt-p53 cells using CD44/epidermal growth factor receptor (EGFR)-targeted hyaluronic acid-based nanoparticles repolarized TAMs towards the M1 phenotype and inhibited tumor growth [ 91 ]. Similarly, the targeted delivery of miR-99b in HCC or subcutaneous Lewis lung cancer mice re-educated TAMs from M2 to M1 phenotype by targeting κB-Ras2 and/or mTOR, thereby enhancing immune surveillance and impeded tumor growth [ 92 ]. In a xenograft mouse model of oral squamous cell carcinoma, overexpression of miR-34a-5p by miR mimic significantly inhibited tumorigenesis [ 93 ].…”

Role of Exosomes in Immune Microenvironment of Hepatocellular Carcinoma

“…e M0 macrophage can polarize to the M1 macrophage with immune surveillance effect or the M2 phenotype with a proinflammatory effect [119]. Although M1 macrophage is the cell type with a stronger capacity of phagocytosis and antigen presentation, M2 macrophage is the major phenotype in the tumor microenvironment and promotes tumor progression [120]. Multiple factors affect the polarization of macrophages, and exosomes serve as an important medium in the interaction between macrophages and HCC [121].…”