Liquid biopsy refers to the sampling and molecular analysis of the biofluids of circulating tumor cells, extracellular vesicles, nucleic acids, and so forth. Exosomes are small extracellular vesicles with sizes between 30-150 nm. They are secreted by multivesicular bodies through exocytosis in live cells and can participate in intercellular communication due to their contents, including nucleic acids, proteins, and lipids. Herein, we investigate publication frequencies on exosomes over the past 10 years, and review recent clinical studies on liquid biopsy of exosomes in the fields of oncology, pregnancy disorders, cardiovascular diseases, and organ transplantation. We also describe the advantages of exosomes as an effective liquid biopsy tool and the progression of exosome extraction methods. Finally, we depict the commercial development of exosome research and discuss the future role of exosomes in liquid biopsy.

Myeloid-derived suppressor cells (MDSCs) potently suppress the anti-tumor immune responses and also orchestrate the tumor microenvironment that favors tumor angiogenesis and metastasis. The molecular networks regulating the accumulation and functions of tumor-expanded MDSCs are largely unknown. In this study, we identified microRNA-494 (miR-494), whose expression was dramatically induced by tumor-derived factors, as an essential player in regulating the accumulation and activity of MDSCs by targeting of phosphatase and tensin homolog (PTEN) and activation of the Akt pathway. TGF-β1 was found to be the main tumor-derived factor responsible for the upregulation of miR-494 in MDSCs. Expression of miR-494 not only enhanced CXCR4-mediated MDSC chemotaxis but also altered the intrinsic apoptotic/survival signal by targeting of PTEN, thus contributing to the accumulation of MDSCs in tumor tissues. Consequently, downregulation of PTEN resulted in increased activity of the Akt pathway and the subsequent upregulation of MMPs for facilitation of tumor cell invasion and metastasis. Knockdown of miR-494 significantly reversed the activity of MDSCs and inhibited the tumor growth and metastasis of 4T1 murine breast cancer in vivo. Collectively, our findings reveal that TGF-β1–induced miR-494 expression in MDSCs plays a critical role in the molecular events governing the accumulation and functions of tumor-expanded MDSCs and might be identified as a potential target in cancer therapy.

MicroRNAs are small non-coding RNA molecules that regulate gene expression by either translational inhibition or mRNA degradation. MicroRNAs play pivotal roles in the regulation of both innate and adaptive immune responses, including TLR-triggered inflammatory response. Here we reported that the expression of microRNA-223 (miR-223) was significantly decreased in murine macrophages during activation by lipopolysaccharide (LPS) or poly (I∶C) stimulation. The inducible miR-223 down-regulation resulted in the activation of signal transducer and activator of transcription 3 (STAT3), which is directly targeted by miR-223, thus promoting the production of pro-inflammatory cytokines IL-6 and IL-1β, but not TNF-α. Interestingly, IL-6 was found to be a main factor in inducing the decrease in miR-223 expression after LPS stimulation, which formed a positive feedback loop to regulate IL-6 and IL-1β. Herein, our findings provide a new explanation characterizing the molecular mechanism responsible for the regulation of IL-6 production after TLR-triggered macrophage activation.

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a b s t r a c tInterleukin 10 (IL-10) is a potent anti-inflammatory cytokine that is crucial for dampening the inflammatory response after pathogen invasion, and was found to be produced by macrophages after exposure to lipopolysaccharide (LPS). It remains unclear whether microRNA-mediated regulatory mechanism is involved in LPS-induced IL-10 production. Here we reported that miR-98 expression in macrophages significantly decreased following LPS stimulation. We also found that miR-98 targets the 3'untranslated region of IL-10 transcript. Overexpression of miR-98 inhibited TLR4-triggered IL-10 production and promoted COX-2 expression. We further demonstrated that miR-98 significantly mitigated the induction of endotoxin tolerance, suggesting that miR-98-mediated posttranscriptional control could potentially be involved in fine tuning the critical level of IL-10 production in endotoxin tolerance.

Background: microRNAs (miRNAs) participate in innate immune responses. Results: miR-92a decreases rapidly in macrophages once stimulated with TLR ligands, and miR-92a controls inflammatory response by targeting MKK4/JNK/c-Jun pathway. Conclusion: TLR-mediated miR-92a reduction feedback enhances TLR-triggered inflammatory response. Significance: Our findings reveal a novel positive feedback loop in which TLR-reduced miR-92a expression functions to regulate the innate inflammatory responses.

Tumor-induced, myeloid-derived suppressor cells (MDSCs)-mediated immune dysfunction is an important mechanism that leads to tumor immune escape and the inefficacy of cancer immunotherapy. Importantly, tumor-infiltrating MDSCs have much stronger ability compared to MDSCs in the periphery. However, the mechanisms that tumor microenvironment induces the accumulation and function of MDSCs are poorly understood. Here, we report that Interleukin-33 (IL-33) - a cytokine which can be abundantly released in tumor tissues both in 4T1-bearing mice and breast cancer patients, is crucial for facilitating the expansion of MDSCs. IL-33 in tumor microenvironment reduces the apoptosis and sustains the survival of MDSCs through induction of autocrine secretion of GM-CSF, which forms a positive amplifying loop for MDSC accumulation. This is in conjunction with IL-33-driven induction of arginase-1 expression and activation of NF-κB and MAPK signaling in MDSCs which augments their immunosuppressive ability, and histone modifications were involved in IL-33 signaling in MDSCs. In ST2 mice, the defect of IL-33 signaling in MDSCs attenuates the immunosuppressive and pro-tumoral capacity of MDSCs. Our results identify IL-33 as a critical mediator that contributes to the abnormal expansion and enhanced immunosuppressive function of MDSCs within tumor microenvironment, which can be potentially targeted to reverse MDSC-mediated tumor immune evasion.

2E) and F4/80 + macrophages (Figure 2F) after DSS treatment for 5 days compared with expression in the colons of healthy mice. These results suggest that increased FBXW7 expression in monocytes and macrophages was correlated with local colonic inflammation in both humans and mice. Fbxw7 deficiency attenuates experimental colitis. To investigate the role of Fbxw7 in macrophages in colitis, LysM-Cre + Fbxw7 fl/fl (LysM + Fbxw7 fl/fl) mice and their control littermates (Fbxw7 fl/fl) were subjected to acute colitis induction using 3% DSS. Colitisinduced macroscopic changes (body weight loss, diarrhea, and rectal bleeding) were significantly alleviated in the LysM + Fbxw7 fl/fl mice compared with Fbxw7 fl/fl littermates (Figure 3A). LysM + Fbxw7 fl/fl mice sacrificed on day 9 displayed significantly longer colons (Figure 3B), milder epithelial damage, and deceased areas of mucosal ulceration (Figure 3C and Supplemental Figure 2A) compared with Fbxw7 fl/fl littermates. Moreover, expression levels of the tight junction genes Cldn1, Cldn2, Ocln, and Tjp1 (Supplemental Figure 2B) and of TJP1 protein (Supplemental Figure 2C) were significantly higher in the epithelia of LysM + Fbxw7 fl/fl mice compared with Fbxw7 fl/fl littermates after DSS treatment, which indicated that the epithelial barrier integrity was less disrupted in mice with myeloid-specific Fbxw7 deficiency. At the same time, LysM + Fbxw7 fl/fl mice showed significantly improved survival rates compared with Fbxw7 fl/fl littermates after 4% DSS treatment (Figure 3D), indicating that Fbxw7 deficiency protects mice from DSS-induced colitis. During the recovery period of intestinal inflammation, the rate of body weight gain was more rapid in LysM + Fbxw7 fl/fl mice than in Fbxw7 fl/fl littermates (Figure 3E). Moreover, LysM + Fbxw7 fl/fl mice had longer colon lengths than did their Fbxw7 fl/fl littermates (Figure 3F) on day 15. Similarly, TNBS-induced colon shortening, the disease activity index (DAI), body weight loss, and epithelial damage were also alleviated in LysM + Fbxw7 fl/fl mice compared with Fbxw7 fl/fl littermates (Supplemental Figure 3, AD). These findings indicate that myeloid Fbxw7 deficiency attenuates experimental colitis. Fbxw7 deficiency decreases proinflammatory MPh accumulation. Microbiota-induced inflammation is critical for the regulation of intestinal homeostasis. To determine whether the decreased DSS colitis susceptibility in LysM + Fbxw7 fl/fl mice was mediated by shifts in gut microbiota, we analyzed the fecal microbiota composition in LysM + Fbxw7 fl/fl mice and Fbxw7 fl/fl littermates. The relative abundance of bacteria at the phylum level and the species composition cluster according to operational taxonomic units (OTUs) among LysM + Fbxw7 fl/fl mice and Fbxw7 fl/fl littermates are shown in Supplemental Figure 4A and Figure 4A, respectively. Moreover, microbial community diversity (Figure 4B) and microbial community composition (Supplemental Figure 4B) were not significantly different between LysM + Fbxw7 fl/fl mice and Fbxw7 fl/fl li...