Abstract B031: Isolation and characterization of extracellular vesicles and nanoparticles from osteosarcoma cell lines: Unveiling supermeres and exomeres for therapeutic insights

Abstract Objective: Osteosarcoma, a malignant bone tumor derived from osteoblasts, the cells responsible for bone formation, commonly affects adolescents but can also arise in older individuals. Treatment typically involves a combination of surgical procedures and chemotherapy which doesn’t have favorable outcomes. However, Extracellular vesicles (EVs), involved in cell-to-cell communication, are emerging as biomarkers for diagnosis and therapy. Recent studies on nanoparticles have unveiled novel types such as "Exomeres and supermeres," demonstrating specific functionalities abundant with potential circulating biomarkers and therapeutic targets across various human diseases. These discoveries pave the way for innovative approaches to diagnosis and treatment, distinct from traditional methods. Methods: High-grade KHOS, MG63, and MG63.3 (Isogenic cell lines) osteosarcoma cell lines, along with human fetal osteoblasts (hFOB1.19), were cultured in serum-free conditioned media for 48 hours. Following this, EVs and nanoparticles were isolated from both osteosarcoma and osteoblast cell lines using a multi-step ultracentrifugation method. Nanoparticle tracking analysis (NTA) was employed to assess particle sizes; however, its ability to detect nanoparticles smaller than 30nm, such as exomeres and supermeres, is limited. Transmission electron microscopy (TEM) was utilized to validate particle sizes, providing visualization and characterization of EVs and nanoparticles based on their diameters. To obtain the proteomic profile of each particle type, we employed an untargeted mass spectrometry approach. Results: Osteosarcoma cell lines, as well as normal osteoblasts, were found to produce EVs and nanoparticles within the expected size range. Transmission electron microscopy (TEM) analysis confirmed the presence of both large and small EVs in their respective fractions. Notably, TEM images of exomeres and supermeres fractions provided novel evidence of particle production by both osteoblasts and osteosarcoma cells. The mass spectrometry findings revealed proteins that could serve as promising targets for extracellular nanoparticles. Additionally, certain proteins exhibited a higher specificity within the superemes. Conclusion: This study shows the isolation and characterization of distinctive extracellular nanoparticles named exomeres and supermeres. These nanoparticles exhibit clear variations in size, morphology, and composition, suggesting their potential as biomarkers for osteosarcoma and their involvement in the tumor microenvironment and metastasis. Citation Format: Marjan Khatami, Geoffroy Danieau, Lata Adnani, Laura Montermini, Nadim Tawil, Brian Meehan, Janusz Rak, Livia Garzia. Isolation and characterization of extracellular vesicles and nanoparticles from osteosarcoma cell lines: Unveiling supermeres and exomeres for therapeutic insights [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Pediatric Cancer Research; 2024 Sep 5-8; Toronto, Ontario, Canada. Philadelphia (PA): AACR; Cancer Res 2024;84(17 Suppl):Abstract nr B031.