Abstract 4468: Tumor-derived extracellular vesicles transmit retroelement and pericentromeric RNAs to drive proinflammatory and DNA damage responses in stromal fibroblasts and immune cells

Abstract

Abstract Chronic cancer-associated inflammation and immunosuppression are common features in most patients with solid malignancies. The causes of this chronic inflammatory-immunosuppressive state are still largely undefined. We hypothesized that selective RNAs can be secreted by cancer cells in extracellular vesicles (EVs) and may trigger proinflammatory responses in target cells, leading to chronic inflammation linked to immune cell dysfunction and immunosuppression. We found that tumor cell lines from pancreatic ductal adenocarcinoma (PDAC), prostate cancer (PCa) and from pediatric cancer such as Ewing sarcoma (EwS) continuously secrete large numbers of small (40-200 nm) EVs. In contrast to non-transformed fibroblasts, cancer cell-derived EVs are enriched with large subsets of retroelement and pericentromeric transcripts, including LINE, SINE and HERV retroelements, and human satellite 2 and 3 (HSAT2,3) RNAs. These virus-like RNAs were highly elevated in plasma EVs from EwS patients but not in healthy donors. Some of them, including HERV-K and HSAT2, were detected in peripheral blood myeloid cells with CD33+HLA-DR− immunosuppressive phenotypes, and these cell populations were expanded in EwS patients compared to healthy donors. Using mouse xenografts and in vitro models, we also found that at least some of these RNAs, such as HSAT2, are transmitted to stromal fibroblasts and immune cells in the tumor microenvironment. They also accumulated in fibroblasts after treatment with EwS EVs, coincident with the induction of proinflammatory and DNA damage responses. Prolonged exposure of fibroblasts to EwS EVs also led to mitotic defects and senescence. Expression and dissemination of these highly immunogenic virus-like RNAs in EVs may thus be a common feature of multiple human malignancies, potentially affecting host cells in the local and systemic tumor environment. This, in turn, may induce chronic inflammation contributing to an overall immunosuppressed state in patients. Citation Format: Valentina Evdokimova, Peter Ruzanov, Hendrik Gassmann, Lincoln D. Stein, Poul H. Sorensen, Stefan Burdach, Laszlo Radvanyi. Tumor-derived extracellular vesicles transmit retroelement and pericentromeric RNAs to drive proinflammatory and DNA damage responses in stromal fibroblasts and immune cells. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4468.