Abstract 174: Organoids developed from synovial sarcoma patient-derived xenografts
Authors: De Cock Lore , Wozniak Agnieszka , Verbeeck Kimberly , Schöffski Patrick 
Published: April 2023

Abstract
Background: Soft tissue sarcoma (STS) is a heterogeneous family of rare malignancies. Despite this heterogeneity, systemic treatment options for patients with advanced STS are rather uniform and have very limited efficacy. There is an unmet medical need to develop more active, subtype-specific treatment options. Three-dimensional (3D) cell culture models (organoids) have been successfully used for drug testing in carcinoma research. However, the development of STS organoids is lagging behind. We attempted to identify the best growth conditions for organoids derived from synovial sarcoma (SySa), which is one of the more common translocation-related subtypes of STS.
Methods: Human synovial sarcoma tissue was implanted subcutaneously into immunodeficient mice and grown to create a patient-derived xenograft (PDX). Fresh tumor tissue from the PDX model was collected and enzymatically and mechanically dissociated into small cell clusters. The cells were seeded into a 3D scaffold with advanced Dulbecco's modified Eagle’s medium (DMEM)/F12 and different growth factors were added. In order to obtain optimal results, different scaffolds and growth factors were compared. The growth of the 3D cultures was evaluated by bright-field microscopy and a cell viability assay using PrestoBlue. The organoids were characterized by histopathological stainings and the presence of the SSX-SS18 translocation was molecularly confirmed. Finally, we attempted to create organoids from PDX-derived material stored in liquid nitrogen.
Results: A scaffold consisting of 50% collagen type 1, 30% Matrigel, 20% DMEM 10x and sodium hydroxide was superior to Matrigel alone. The addition of human recombinant epidermal growth factor (EGF, 10 ng/ml), human insulin-like growth factor 1 (IGF-1, 20 ng/ml), human recombinant fibroblast growth factor 2 (FGF-2, 10 ng/ml), and N-acetylcysteine (NAC, 500 mmol) to advanced DMEM/F12 stimulated the growth of SySa organoids the best. The Rho-kinase inhibitor Y-27632 was added to prevent apoptosis during early passages. So far, attempts to create organoids from frozen material have been unsuccessful.
Conclusions: At present, the success rate of establishing organoids from synovial sarcoma cells is limited if the culture conditions are not adapted to their needs. We identified that growth factors such as EGF, FGF-2, IGF-1, and NAC are beneficial for growth. The availability of fresh samples plays an important role in the development of these 3D models. Despite these limitations, organoids can be an interesting tool for studying this rare disease and aid in the development of new drugs.
Citation Format: Lore De Cock, Agnieszka Wozniak, Kimberly Verbeeck, Patrick Schöffski. Organoids developed from synovial sarcoma patient-derived xenografts [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 174.