Abstract 154: Establishment and characterization of a novel clear cell sarcoma organoid model derived from a human biopsy
Authors: Campbell Petreena S. , Harris Erik D. , Moore Nancy , Parchment Ralph E. , Coussens Nathan P. , Teicher Beverly A. , Chen Alice , Doroshow James H. , Rapisarda Annamaria 
Published: June 2023

Abstract
Clear Cell Sarcoma (CCS) is an extremely aggressive, rare soft tissue cancer accounting for approximately 1% of all sarcomas. Often diagnosed in young adults with a median age of 25 years, CCS has a strong propensity for local recurrence and metastasis with an overall high mortality rate. Current treatment recommendations include radical surgical extirpation, followed by radiation or chemotherapy. Nonetheless, there is a need for extensive postoperative follow-up as the efficiency of adjuvant therapy in managing this disease remains poor. Consequently, it is imperative to identify clinically relevant models to advance our understanding of CCS tumor biology and facilitate the development of novel therapies. Compared to conventional preclinical tumor models, patient-derived organoids (PDOrgs) better recapitulate the patient tumor biology, genetic heterogeneity, and therapeutic responses. Here, we describe the development and validation of a human biopsy-derived CCS organoid model 1010561-T. 1010561-T was established from a male patient's metastatic paraspinal mass. This PDOrg demonstrates a moderate growth rate (doubling time of ~20 days) and pleomorphic traits, consisting mainly of solid, grape-like clusters, as well as elongated cells of mixed morphology. Furthermore, this model was successfully maintained over 7 months in culture and remained stable more than one year after cryopreservation. 1010561-T exhibits the cytogenetic hallmark of CCS which is the presence of a recurrent t(12;22)(q13;q12) chromosomal translocation, resulting in a fusion between the Ewing sarcoma gene and activating transcription factor 1 (EWS/ATF1 fusion). Reverse-transcription polymerase chain reaction (RT-PCR) confirmed that 1010561-T harbors a dual EWS/ATF1 fusion, namely EWS exon 8 to ATF1 codon 65 fusion (type 1) and EWS exon 7 to ATF1 codon 110 fusion (type 3). Quantitative RT-PCR and immunocytochemistry revealed strong expression of melanocytic differentiation markers typical of CCS including melanocyte inducing transcription factor (MITF), melan-A (MLANA), premelanosome protein (PMEL), and S100 calcium binding protein A11 (S100A11). Additionally, the gene expression profile of 1010561-T is in concordance with a well-established CCS cell line, SU-CCS-1. To our knowledge, 1010561-T is the first human CCS organoid model. It is, therefore, a valuable resource for advancing our understanding of the biology of this very rare disease, in addition to being a useful tool for validating new preclinical therapies that are undoubtedly needed to achieve better clinical outcomes for patients. To this end, 1010561-T will be transferred to the National Cancer Institute’s Patient-Derived Models Repository (https://pdmr.cancer.gov) where it will be made available to the scientific community. This project was funded in part with federal funds from the NCI, NIH, under contract no. HHSN261201800001I.
Citation Format: Petreena S. Campbell, Erik D. Harris, Nancy Moore, Ralph E. Parchment, Nathan P. Coussens, Beverly A. Teicher, Alice Chen, James H. Doroshow, Annamaria Rapisarda. Establishment and characterization of a novel clear cell sarcoma organoid model derived from a human biopsy [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 154.