MicroRNAs (miRNAs) are small noncoding RNAs, 19-24 nucleotides in length, that regulate gene expression and are expressed aberrantly in most types of cancer. MiRNAs also have been detected in the blood of cancer patients and can serve as circulating biomarkers. It has been shown that secreted miRNAs within exosomes can be transferred from cell to cell and can regulate gene expression in the receiving cells by canonical binding to their target messenger RNAs. Here we show that tumor-secreted miR-21 and miR-29a also can function by another mechanism, by binding as ligands to receptors of the Toll-like receptor (TLR) family, murine TLR7 and human TLR8, in immune cells, triggering a TLR-mediated prometastatic inflammatory response that ultimately may lead to tumor growth and metastasis. Thus, by acting as paracrine agonists of TLRs, secreted miRNAs are key regulators of the tumor microenvironment. This mechanism of action of miRNAs is implicated in tumor-immune system communication and is important in tumor growth and spread, thus representing a possible target for cancer treatment.icroRNAs (miRNAs) are small, noncoding RNAs, 19-24 nt in length, with gene-expression regulatory functions (1, 2) and are expressed aberrantly in most types of cancer (3, 4). MiRNAs also have been detected in the blood of cancer patients (5, 6) and can serve as circulating biomarkers (7). It has been shown that secreted miRNAs within exosomes can be transferred from cell to cell and can regulate gene expression in the receiving cells (8) by canonical binding to their target messenger RNAs (8, 9). More recently, it has been demonstrated that, in addition to their role as gene-expression regulators, miRNAs also directly interact with proteins (10).Members of the Toll-like receptor (TLR) family (namely, murine TLR7 and human TLR8) can recognize and bind viral single-stranded RNA (ssRNA) sequences on dendritic cells and B lymphocytes, leading to cell activation and cytokine production (11,12). TLRs are a family of receptors through which the mammalian innate immune system recognizes the presence of invading pathogens (13,14). Both murine TLR7 and human TLR8 bind to and are activated by 20-nt-long ssRNAs, which represent physiological ligands for these two receptors (12), located in intracellular endosomes. Circulating mature miRNAs are 19-24 nt in length and could represent tumor-released ligands of TLR7 and TLR8 involved in intercellular communication in the tumor microenvironment. Results and Discussion Identification of Specific miRNAs Released in Cancer Cell-DerivedExosomes. To identify which miRNAs are present in tumor-secreted exosomes, we isolated exosomes from the supernatant of A-549 and SK-MES lung cancer cell lines. First, we assessed the purified supernatant exosome fraction for enrichment in CD9 and CD63, two known exosome markers (SI Appendix, Fig. S1A) (8,15). By performing NanoString analysis, we observed that nine miRNAs (miR-16, -21, -27b, -29a, -133a, -193a-3p, -544, -563, and -1283) were present in exosomes derived from ...

BackgroundThe mechanisms underlying chronic obstructive pulmonary disease (COPD) remain unclear. MicroRNAs (miRNAs or miRs) are small non-coding RNA molecules that modulate the levels of specific genes and proteins. Identifying expression patterns of miRNAs in COPD may enhance our understanding of the mechanisms of disease. A study was undertaken to determine if miRNAs are differentially expressed in the lungs of smokers with and without COPD. miRNA and mRNA expression were compared to enrich for biological networks relevant to the pathogenesis of COPD. Methods Lung tissue from smokers with no evidence of obstructive lung disease (n¼9) and smokers with COPD (n¼26) was examined for miRNA and mRNA expression followed by validation. We then examined both miRNA and mRNA expression to enrich for relevant biological pathways.

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MicroRNA-29b (miR-29b) expression has been shown to be reduced in non-small–cell lung cancer (NSCLC) tissues. Here, we have identified the oncogene cyclin-dependent protein kinase 6 (CDK6) as a direct target of miR-29b in lung cancer. We hypothesized that in vivo restoration of miR-29b and thus targeting of genes important to tumor initiation and progression may represent an option for lung cancer treatment. We developed a cationic lipoplexes (LPs)-based carrier that efficiently delivered miR-29b both in vitro and in vivo. LPs containing miR-29b (LP-miR-29b) efficiently delivered miR-29b to NSCLC A549 cells, reduced the expression of key targets CDK6, DNMT3B, and myeloid cell leukemia sequence 1 (MCL1), as well as cell growth and clonogenicity of A549 cells. In addition, the IC50 for cisplatin in the miR-29b–treated cells was effectively reduced. In a xenograft murine model, LPs efficiently accumulated at tumor sites. Systemic delivery of LP-miR-29b increased the tumor miR-29b expression by approximately fivefold, downregulated the tumor mRNA expression of CDK6, DNMT3B, and MCL1 by ~57.4, ~40.5, and ~52.4%, respectively, and significantly inhibited tumor growth by ~60% compared with LP-miR-NC (negative control). Our results demonstrate that cationic LPs represent an efficient delivery system that holds great potential in the development of miRNA-based therapeutics for lung cancer treatment.