Cell-derived exosomes have been demonstrated to be efficient carriers of small RNAs to neighbouring or distant cells, highlighting the preponderance of exosomes as carriers for gene therapy over other artificial delivery tools. In the present study, we employed modified exosomes expressing the neuron-specific rabies viral glycoprotein (RVG) peptide on the membrane surface to deliver opioid receptor mu (MOR) siRNA into the brain to treat morphine addiction. We found that MOR siRNA could be efficiently packaged into RVG exosomes and was associated with argonaute 2 (AGO2) in exosomes. These exosomes efficiently and specifically delivered MOR siRNA into Neuro2A cells and the mouse brain. Functionally, siRNA-loaded RVG exosomes significantly reduced MOR mRNA and protein levels. Surprisingly, MOR siRNA delivered by the RVG exosomes strongly inhibited morphine relapse via the down-regulation of MOR expression levels. In conclusion, our results demonstrate that targeted RVG exosomes can efficiently transfer siRNA to the central nervous system and mediate the treatment of morphine relapse by down-regulating MOR expression levels. Our study provides a brand new strategy to treat drug relapse and diseases of the central nervous system.

BackgroundThe origin and development of breast cancer remain complex and obscure. Recently, microRNA (miRNA) has been identified as an important regulator of the initiation and progression of breast cancer, and some studies have shown the essential role of miR-124-3p as a tumor suppressor in breast tumorigenesis. However, the detailed role of miR-124-3p in breast cancer remains poorly understood.MethodsQuantitative RT-PCR and western blotting assays were used to measure miR-124-3p and CBL expression levels in breast cancer tissues, respectively. Luciferase reporter assay was employed to validate the direct targeting of CBL by miR-124-3p. Cell proliferation and invasion assays were performed to analyze the biological functions of miR-124-3p and CBL in breast cancer cells.ResultsIn the present study, we found that miR-124-3p was consistently downregulated in breast cancer tissues. Moreover, we showed that miR-124-3p significantly suppressed the proliferation and invasion of breast cancer cells. In addition, we investigated the molecular mechanism through which miR-124-3p contributes to breast cancer tumorigenesis and identified CBL (Cbl proto-oncogene, E3 ubiquitin protein ligase) as a direct target gene of miR-124-3p. Moreover, we found that ectopic expression of CBL can attenuate the inhibitory effect of miR-124-3p on cell proliferation and invasion in breast cancer cells.ConclusionsThis study identified a new regulatory axis in which miR-124-3p and CBL regulate the proliferation and invasion of breast cancer cells.Electronic supplementary materialThe online version of this article (doi:10.1186/s12885-016-2862-4) contains supplementary material, which is available to authorized users.

MicroRNAs (miRNAs) have emerged as a major regulator of the initiation and progression of human cancers, including breast cancer. However, the cooperative effects and transcriptional regulation of multiple miRNAs, especially miRNAs that are present in clusters, remain largely undiscovered. Here we showed that all members of the miR-23~27~24 clusters are upregulated and function as oncogenes in breast cancer and simultaneously target HIC1. Furthermore, we found that HIC1 functions as a transcriptional repressor to negatively control the expression of miR-23~27~24 clusters and forms a double-negative (overall positive) feedback loop. This feedback regulatory pathway is important because overexpression of miR-23~27~24 clusters can remarkably accelerate tumor growth, whereas restoration of HIC1 significantly blocks tumor growth in vivo. A mathematical model was created to quantitatively illustrate the regulatory circuit. Our finding highlights the cooperative effects of miRNAs in a cluster and adds another layer of complexity to the miRNA regulatory network. This study may also provide insight into the molecular mechanisms of breast cancer progression.

Previous studies reported that the expression of miR-23b-27b cluster was downregulated in embryonic brain cortices during hypoxia-induced neuronal apoptosis. However, the mechanism underlying this downregulation is not completely understood. Here, we report that the transcription factor c-Myc plays an important role in regulating the expression of miR-23b-27b cluster during hypoxia. First, the c-Myc protein level was significantly elevated in embryonic brain cortices in a mouse model of fetal distress. Second, forced overexpression or knockdown of c-Myc could suppress or increase the expression of miR-23b-27b cluster polynucleotides. Third, we identified 2 conserved c-Myc binding sites (E-boxes) in the enhancer and promoter regions of miR-23b-27b cluster in the mouse genome. Finally, we showed that elevated c-Myc expression led to an increase in the Apaf-1 level by suppressing miR-23b-27b cluster expression and that this enhanced neuronal sensitivity to apoptosis. In summary, our study demonstrates that c-Myc may suppress the expression of the miR-23b-27b cluster, resulting in additional neuronal apoptosis during hypoxia.