Abstract 4060: The role of paraspeckles in EWS activated cancers

Abstract The ETS family of transcription factors become aberrantly activated in multiple cancers. This activation is dependent on the co-activator EWS in both prostate cancer and Ewing sarcoma, an adolescent bone cancer. In prostate cancer, EWS is a binding partner necessary for oncogenic ETS, primarily ERG, activation. In Ewing sarcoma, the intrinsically disorder region (IDR) of EWS is fused to ETS members, primarily FLI1, and promotes aberrant expression and activation. The IDR of EWS promotes liquid-liquid phase separation (LLPS) and acts as a transcriptional activation domain. Current studies link LLPS with oncogenesis, making the LLPS ability of EWS a potential mechanism for oncogenic co-activation. In cells, EWS is found in phase separated bodies such as paraspeckles. Paraspeckles are nuclear bodies that have a role in transcriptional regulation, but their role in cancers is not well understood. I have shown that ERG and EWS/FLI1 colocalize with EWS granules in a purified protein droplet assay. This suggests that oncogenic ETS can participate in EWS LLPS. NEAT1, the essential RNA scaffolding of the paraspeckle, has a role in tumor progression in prostate cancer and I have shown that both ERG and EWS/FLI1 interact with NEAT1 through RIP. However, the potential role of paraspeckles in Ewing sarcoma or prostate cancer has not been further investigated. ETS positive prostate cancer and Ewing sarcoma lines showed paraspeckle presence through NEAT1 RNA-FISH. Knock down (KD) of two necessary paraspeckle components, NEAT1 or FUS, in Ewing sarcoma cells reduce paraspeckle presence, colony growth, and EWS/FLI1 activity at the transcriptional level. KD of FUS and NEAT1 also increased migration, which is consistent with EWS/FLI1 loss. Taken together, these data suggest that the paraspeckle has a role in EWS/FLI1 activity in Ewing Sarcoma and that components of the paraspeckle interact with ERG. Because ERG and FLI1 are homologous, there is potential that the paraspeckle acts as a mechanism of oncogenic transcription in prostate cancer as well as Ewing sarcoma. Citation Format: Renee A. Kinne, Peter C. Hollenhorst. The role of paraspeckles in EWS activated cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 4060.