Therapeutic Targeting of Fusion Positive Ewing Sarcoma with RNA Sensor

Document Type

Article

Publication Date

2026

JAX Location

JGM

Abstract

Ewing sarcoma (ES) is an aggressive pediatric bone or soft tissue cancer with five-year survival rates of less than 41% for metastatic cases, underscoring the need for targeted therapies. ES is driven by the EWSR1::FLI1 gene fusion, a transcription factor that drives metastasis and tumorigenesis. This fusion protein lacks enzymatic activity and small pockets for small molecules to bind, making direct drug targeting difficult. As an alternative therapeutic strategy, we look to target the RNA transcript of gene fusions with an RNA sensor that utilizes Adenosine Deaminase acting on RNA (ADAR) editing to target the EWSR1e7::FLI1e6 fusion transcript. Upon binding to the fusion transcript, ADAR edits two introduced stop codons removing the fusion junction and allowing translation and release a downstream payload. We tested two sensor parameters: the distances between the engineered stop codons (150, 90, 45 bp) and the length of the sensing region (501, 249, or 90 bp). Each design, paired with either an EGFP or dTKSR39 payload, was co-transfected into HEK293T with either a empty control vector or an EWSR1e7::FLI1e6-expressing plasmid. Sensor efficiency was determined via flow cytometry (EGFP) and CellTiter-Glo cellular viability assays following addition of prodrug ganciclovir (dTKSR39). Sensors with greater stop codons distances and longer sensing region lengths performed most strongly across both payloads, with the (150stop_501length) design consistently being most efficient. These results provide design parameters for the RNA sensor targeting of EWSR1e7::FLI1e6, the ultimate goal of providing a targeted therapy to ES patients.

Please contact the Joan Staats Library for information regarding this document.

COinS