Extracellular vesicle enclosed circular RNA and interferon responses in tumor host interactions.

PROJECT ABSTRACT This R21 features two principal investigators with complementary expertise on extracellular vesicles (EVs) and circular RNA (circRNA), respectively. The focus in on prostate cancer (PC), which is a leading cause of death in the United States, with particular emphasis on a novel mechanisms underlying the immune- suppressive functions of the tumor-associated macrophages (TAMs). The study will elucidate the role of EV-enclosed circRNAs in modulating the immune response to the cancer. Understanding the mechanisms by which tumor cells shape pro-tumorigenic TAMs, and targeting these mechanisms, holds potential for novel immunotherapies that could be combined with standard treatments. We hypothesize that PC-derived anti- inflammatory circRNAs can be exchanged between PC cells and neighboring TAMs via exosomes (Exo), triggering non-cell-autonomous anti-inflammatory signals within the recipient cells. The study is structured in two Aims: Aim 1 will investigate the transfer of EVs from PC cells to macrophages, quantifying EV uptake by these target cells in real time using an innovative strategy recently refined in the Di Vizio laboratory. Aim 2 will focus on the mechanisms by which circRNAs enclosed in PC-derived EVs modulate macrophage activation and function. The expression of specific anti-inflammatory circRNAs in the donor PC cells and the activation state of tumor-infiltrating macrophages will be investigated using single-cell RNA sequencing (scRNAseq). Functional experiments, both in vitro and in vivo, will employ new technologies already developed in the Guarnerio lab, and will be conducted to support the sequencing data. The impact is high because the study will elucidate novel mechanisms regulating the response of the immune cells to the tumor, which might explain, at least in part, why current immunetherapy strategies fail. In the long term, this study has the potential to outline new clinical targets, based on a better understanding on how tumor cells adjust to and change the surrounding microenvironment.