MicroRNA profile of cells and exosomes

The goal of this study is to report that breast cancer associated exosomes contain microRNAs (miRNAs) associated with the RISC Loading Complex (RLC) and display cell-independent capacity to process precursor microRNAs (pre-miRNAs) into mature miRNAs. Pre-miRNAs, along with Dicer, AGO2, and TRBP, are present in exosomes of cancer cells. CD43 mediates the accumulation of Dicer specifically in cancer exosomes. Cancer exosomes mediate an efficient and rapid silencing of mRNAs to reprogram the target cell transcriptome. Exosomes derived from cells and sera of patients with breast cancer instigate non-tumorigenic epithelial cells to form tumors in a Dicer-dependent manner. These findings offer opportunities for the development of exosomes based biomarkers and therapies. Exosomes from cancer cells and non-tumorigenic cells were isolated using established ultracentrifugation methods. The global miRNA content of cancer exosomes and normosomes was investigated. Profiling of cells themselves was also used as a control. Exosomes with Dicer down regulation (MCF10AshDicer and MDA-MB-231shDicer exosomes), as well as MDA-MB-231 exosomes that contain a Dicer antibody inside were used to study the function Dicer protein in the microRNA biogenesis in exosomes.