Summary – Overall Component Cellular communication between diverse cells is now recognized to heavily influence both cancer initiation and progression. Recently, several new forms of intercellular communication have been recognized, including exchange of proteins and RNAs via extracellular vesicles (EVs) and other carriers. Extracellular RNA (ExRNA) is particularly interesting, as it has the potential to influence gene expression and potentially epigenetic states. MicroRNAs (miRNAs) in particular have been shown to be transferred from one cell type to another to influence gene expression; however, it is clear that many kinds of exRNAs are selectively secreted from cells. What is less clear is how those exRNAs (including miRNAs) are packaged into EVs and other carriers. In addition, the overall impact of these exRNAs on cells and tissues is not yet understood. In this program, we propose to elucidate the “rules of the game” for extracellular RNA communication, using colorectal carcinoma (CRC) as a model system. Our Program will be highly synergistic, because each Project focuses on a different aspect of this problem. Thus, Project 1 will determine how subcellular contacts between organelles drive RNA and RNA-binding protein (RBP) transfer to EVs in CRC. Project 2 will identify RNA modifications and sequences that drive molecular selection of RNAs for transfer into EVs in CRC. Project 3 will identify how EVs and exomeres mediate EGFR-Wnt crosstalk in CRC. All Projects use common experimental systems, including CRC isogenic cell models, and have common biological focus (e.g. how miR-100 and miR-125b are trafficked and influence recipient cell function in CRC). Integration, synergy, and progress of the Projects will be highly enhanced by the proposed Administrative and Shared Resource Cores. Together this Program will make a major impact in the areas of CRC, tumor microenvironment, exRNA, EVs, and RNA biology.