Despite the therapeutic potential of nucleic acid drugs, their clinical application has been limited in part by a lack of appropriate delivery systems. Exosomes or microvesicles are small endosomally derived vesicles that are secreted by a variety of cell types and tissues. Here, we show that exosomes can efficiently deliver microRNA (miRNA) to epidermal growth factor receptor (EGFR)-expressing breast cancer cells. Targeting was achieved by engineering the donor cells to express the transmembrane domain of platelet-derived growth factor receptor fused to the GE11 peptide. Intravenously injected exosomes delivered let-7a miRNA to EGFR-expressing xenograft breast cancer tissue in RAG2(-/-) mice. Our results suggest that exosomes can be used therapeutically to target EGFR-expressing cancerous tissues with nucleic acid drugs.

BackgroundMicroRNAs are a family of 19- to 25-nucleotides noncoding small RNAs that primarily function as gene regulators. Aberrant microRNA expression has been described for several human malignancies, and this new class of small regulatory RNAs has both oncogenic and tumor suppressor functions. Despite this knowledge, there is little information regarding microRNAs in plasma especially because microRNAs in plasma, if exist, were thought to be digested by RNase. Recent studies, however, have revealed that microRNAs exist and escape digestion in plasma.Methodology/Principal FindingsWe performed microRNA microaray to obtain insight into microRNA deregulation in the plasma of a leukemia patient. We have revealed that microRNA-638 (miR-638) is stably present in human plasmas, and microRNA-92a (miR-92a) dramatically decreased in the plasmas of acute leukemia patients. Especially, the ratio of miR-92a/miR-638 in plasma was very useful for distinguishing leukemia patients from healthy body.Conclusions/SignificanceThe ratio of miR-92a/miR-638 in plasma has strong potential for clinical application as a novel biomarker for detection of leukemia.

MicroRNAs (miRNAs) belong to a class of endogenously expressed non-coding small RNAs that function primarily as gene regulators. Growing evidence suggests that miRNAs play a significant role in tumor development, making them potential biomarkers for cancer diagnosis and prognosis. The miR-17-92 cluster has emerged as an important locus, being highly overexpressed in several cancers in association with cancer development and progression. The miR-17-92 miRNA cluster generates a single polycistronic primary transcript that yields six mature miRNAs: miR-17, miR-18a, miR-19a, miR-20a, miR-19b, and miR-92a. In colon cancer development, the pathophysiologic roles of these transcripts and their targets are largely unknown. In the present study, we performed copy number analyses of the six miRNAs transcribed from the miR-17-92 cluster in colon tumor tissues. We determined that miR-92a was transcribed at higher levels than the other five miRNAs in both adenomas and carcinoma. In addition, miR-92a directly targeted the anti-apoptotic molecule BCL-2-interacting mediator of cell death (BIM) in colon cancer tissues. An anti-miR-92a antagomir induced apoptosis of colon cancer-derived cell lines. These data indicate that miR-92a plays a pivotal role in the development of colorectal carcinoma. (Cancer Sci 2011; 102: 2264-2271 M icroRNAs (miRNAs) belong to a class of endogenously expressed non-coding small RNAs of approximately 22 nucleotides. These small RNAs influence gene regulation by pairing with mRNAs of protein-encoding genes to repress their expression via decreased translational efficiency and ⁄ or mRNA levels.(1) A growing body of evidence suggests that dysregulation of miRNA expression contributes to a wide variety of human diseases, including cancer. Almost 50% of known miRNAs are located within chromosomal regions frequently amplified or deleted in human cancers. (2) Colorectal cancer (CRC) is the second most common cause of cancer deaths in the Western world.(3) A heterogeneous disease, CRC develops from an accumulation of multiple genetic and epigenetic alterations that change global gene expression profiles; it is this genetic progression that contributes to the diverse phenotypes of CRC. A key step in the progression to cancer is genomic instability, which occurs in approximately 5% of adenomas through either microsatellite instability (MSI) or chromosomal instability (CIN). In CRC, CIN induces the development of aneuploid tumors, which exhibit a non-random pattern of chromosomal alterations that frequently include gains at 8q, 13q, and 20q and losses of 8p, 15q, 17p, and 18q.(4) The miR-17-92 cluster, located at 13q, encodes six miRNAs processed from a common precursor transcript. A role for miR-17-92 in the pathogenesis of human cancers has been implicated by the high incidence of amplification in multiple neoplasms, including diffuse large B cell lymphoma (5) and small cell lung cancer.(6,7)Furthermore, miR-92a derived from this cluster is highly expressed in leukemia (8) and hepatocellular carcinoma tissues....

MicroRNAs (miRNAs) belong to a class of the endogenously expressed non-coding small RNAs which primarily function as gene regulators. Growing evidence suggests that miRNAs have a significant role in tumor development and may constitute robust biomarkers for cancer diagnosis and prognosis. The miR-17-92 cluster especially is markedly overexpressed in several cancers, and is associated with the cancer development and progression. In this study, we have demonstrated that miR-92a is highly expressed in hepatocellular carcinoma (HCC). In addition, the proliferation of HCC-derived cell lines was enhanced by miR-92a and inhibited by the anti-miR-92a antagomir. On the other hand, we have found that the relative amount of miR-92a in the plasmas from HCC patients is decreased compared with that from the healthy donors. Interestingly, the amount of miR-92a was elevated after surgical treatment. Thus, although the physiological significance of the decrease of miR-92a in plasma is still unknown, deregulation of miR-92 expression in cells and plasma should be implicated in the development of HCC.

Peroxisome proliferator-activated receptor (PPAR)-␣, a transcriptional activator, regulates genes of fatty acid (FA) metabolic enzymes. To study the contribution of PPAR-␣ to exercise training-induced improvement of FA metabolic capacity in the aged heart, we investigated whether PPAR-␣ signaling and expression of its target genes in the aged heart are affected by exercise training. We used hearts of sedentary young rat (4 mo old), sedentary aged rat (23 mo old), and swim-trained aged rat (23 mo old, training for 8 wk). The mRNA and protein expression of PPAR-␣ in the heart was significantly lower in the sedentary aged rats compared with the sedentary young rats and was significantly higher in the swim-trained aged rats compared with the sedentary aged rats. The activity of PPAR-␣ DNA binding to the transcriptional regulating region on the FA metabolic enzyme genes, the mRNA expression of 3-hydroxyacyl CoA dehydrogenase (HAD) and carnitine palmitoyl transferase-I, which are PPAR-␣ target genes, and the enzyme activity of HAD in the heart altered in association with changes of the myocardial PPAR-␣ mRNA and protein levels. These findings suggest that exercise training improves aging-induced downregulation in myocardial PPAR-␣-mediated molecular system, thereby contributing to the improvement of the FA metabolic enzyme activity in the trained-aged hearts.peroxisome proliferator-activated receptor-␣; swimming training; aged rat; fatty acid THE HEART is known for its ability to produce energy from fatty acids (FA) because of its important ␤-oxidation equipment, but it can also derive energy from several other substrates, including glucose and lactate (10, 23). On a physiological condition, FA is considered to account for 60-70% of oxygen consumption for energy production in the heart (23). However, FA metabolic capacity in the heart is reduced by aging (19, 32).It has been reported that exercise training improved an aging-induced decrease of FA metabolic capacity in the heart (7, 18, 25, 32). However, the mechanisms for improving FA metabolic capacity in the heart by exercise training are unclear.Peroxisome proliferator-activated receptor (PPAR)-␣ is a member of the nuclear receptor transcription factor superfamily and is mainly expressed in the heart, liver, and kidney (2,13,29). The recent studies indicated that PPAR-␣ plays a critical role in the expression of genes involved in FA metabolism (13). PPAR-␣ heterodimerizes with the retinoid X receptor (RXR-␣) to bind to peroxisome proliferator-response elements (PPRE) in the upstream regions of a number of genes involved in metabolic homeostasis (13,29). PPAR-␣ regulates target genes encoding FA metabolic (␤-oxidation) enzymes and FA transporters such as FA binding protein, carnitine palmitoyl transferase-I (CPT-I), acyl-CoA synthase, 3-hydroxyacyl CoA dehydrogenase (HAD), apolipoproteins, and so on, suggesting that PPAR-␣ plays an important role in FA metabolic homeostasis (2,5,17,29). However, it is unknown whether the aging and subsequent exercise training affect...