Abstract 6974: Spatial exosome analysis reveals the location heterogeneity of exosomal miRNAs in ovarian cancer patients

Abstract Extracellular vesicles (EVs), including exosomes, are recognized as promising functional tools involved in cancer progression. Although evidence of the functions of EV in cancer biology has been accumulating, optimizing EV isolation is still a major challenge. In ovarian cancer, peritoneal dissemination is a crucial prognostic factor due to the lack of effective treatment, and EVs in malignant ascites play a key role for progression. In this study, we invented cellulose nanofiber (CNF) sheets which enable to capture EVs from approximately 10 μL of biofluids and enabled the analysis of the bioactive molecules included in the EVs (Nature Communications 2023). By attaching CNF sheets to moistened organs, the EVs in trace amounts of ascites were collected, which was sufficient to perform small RNA sequence analyses. In the ovarian cancer mouse model, CNF sheets enabled the detection of cancer-associated miRNAs from the very early phase when the mice did not have apparent ascites, and the EVs from different locations, such as pelvic walls or liver surfaces, had unique miRNA profiles. To confirm the utility of the CNF sheets in cancer patients, we directly collected the EVs on the organ surfaces by the EV attachment method during surgery under appropriate ethical institutional approval with individual consent. EVs were collected from the pelvic peritoneum, omentum, liver surface, or tumor surface, and the miRNA profiling demonstrated each location formed unique clusters. Notably, several tumor-suppressive miRNAs have been identified in liver surface EVs, such as miR-122-3p, and this is consistent with actual ovarian cancer cell progression, which tends to metastasize to the diaphragm rather than to the liver surface. In addition, the trajectory analysis revealed that the pattern of connection in each site was different between patients with localized and advanced disease. We identified ten miRNAs were high in tumors and in EVs from tumor rupture sites, and the level of each miRNA decreased with distance from the primary tumors. Among ten miRNAs, hsa-miR-200b-3p and hsa-miR-429 were confirmed as highly expressed in tumor tissues compared to adjacent normal tissues or benign tumors, and three miRNAs in serum, urine and saliva decreased post-surgery. In summary, spatial CNF sheet analyses in patient bodies identified location-based heterogeneity in EV-miRNA profiles, and the profiles reflected disease conditions. This new method could provide unveiled biological aspects of EVs, and suggest a clinical strategy contributing to cancer diagnosis, staging evaluation, and therapy planning. Citation Format: Akira Yokoi, Kosuke Yoshida, Yusuke Yamamoto, Takao Yasui, Hiroaki Kajiyama. Spatial exosome analysis reveals the location heterogeneity of exosomal miRNAs in ovarian cancer patients abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (6Suppl): Abstract nr 6974.