One of the overarching challenges of PCRP is to develop effective treatments for advanced prostate cancer. As nano-meter sized vesicles released by many cell types, exosomes serve as vehicles for long range intercellular communications, with the bioactive contents of exosomes as the messengers. It is hypothesized that normal prostate epithelial cells secrete exosomes to keep neighboring epithelial cells from undergoing uncontrolled growth. On the other hand, due to the altered contents of exosomes, those from prostate cancer cells (tumor exosomes) no longer have tumor suppressive functions. If this hypothesis is proven true, the tumor suppressive exosomes can be characterized and reconstructed as therapeutic agents used for the treatment of prostate cancer. To develop this concept, exosomes will be isolated from normal prostate epithelial cells by differential centrifugations or affinity purifications and evaluated for tumor suppressing activities against various prostate cancer cells (Aim 1). Then the components of the tumor suppressing exosomes will be separated, identified and characterized using biochemical, molecular, and analytical methods and compared with those found in tumor exosomes (Aim 2). Then the exosomes will be additively manufactured by recombining the identified components in parts or as a whole, and evaluated for their therapeutic utilities against prostate cancer (Aim 3). The proposed studies address the focus area of therapy. In short term, the studies will identify potential tumor suppressing exosomes that can inhibit prostate cancer. In the long term, the studies will lead new approaches to harness the tumor suppressive powers of normal prostate epithelial and to develop new biological therapeutics for treatment of prostate cancer.