Exosomes and microvesicles are nano-sized vesicles that are released from many cell types. Exosomes are being developed for various clinical and translational applications such as biomarkers of disease and drug delivery vehicles. Despite rapid advances in the field, there is still a limited understanding of many aspects of exosome biology, including their formation, cell entry and functions. In order to clarify aspects of exosome biology, a more complete understanding of their components is needed. While many proteomic and genomic analyses of exosomes have been published, very few studies investigated exosomes from different cell types. We propose here a detailed characterization of the small RNA cargo, in vivo biodistribution and metastatic potential of the exosomes from the NCI-60 cell line panel. The postdoctoral candidate will work closely with the research team to accomplish the aims of the study. In Aim 1 we will use small RNASeq technology to determine the RNA cargo in exosomes purified from cancer cells of the NCI-60 panel. In Aim 2, we will rigorously validate cell- and cancer-specific RNAs in distinct exosome populations. Aim 3 will characterize the in vivo bio-distribution of NCI-60 cell line exosomes in the mice. Aim 4 will determine the utility of circulating exosomal miRNAs in identifying cancer and tumor progression using preclinical human tumor xenograft models. Overall, completion of this project will result in proven methods for exosome purification, small RNA markers for internal and external validation of the presence and purity of exosome preparations and novel exosome-specific cancer markers confirmed in the circulation of pre-clinical xenograft models. Furthermore, we will obtain the in vivo organ targeting of exosomes from different cell lines. The data generated will result in major advancements in our understanding of exosome RNA content that will facilitate their use in cancer diagnostics and as therapeutic delivery vehicles.