Targeting GPX4 and FSP1 to exploit ferroptotic vulnerability in Ewing sarcoma.

Ewing sarcoma tumors are defined by chromosomal translocations fusing EWSR1 to ETS family genes, most commonly FLI1. The resulting EWS::FLI1 fusion oncoprotein drives tumorigenesis while simultaneously generating unique metabolic and molecular dependencies that may be exploited for Ewing sarcoma-specific therapies. Through analysis of the Cancer Dependency Map (DepMap, Broad Institute), we identified that Ewing sarcoma cell lines exhibit selective sensitivity to loss of genes regulating selenium metabolism compared to other cancer lineages. Ewing sarcoma cells are similarly sensitive to knockout of glutathione peroxidase 4 (GPX4), a selenoprotein that suppresses ferroptosis, a form of regulated, iron-dependent cell death characterized by the lethal accumulation of lipid peroxides. Using pharmacological inhibitors and targeted degraders of GPX4, as well as genetic knockout approaches, we demonstrate that Ewing sarcoma cells are selectively vulnerable to GPX4 loss or inhibition. We further identify ferroptosis suppressor protein 1 (FSP1) as a modulator of ferroptotic sensitivity in Ewing sarcoma, with FSP1 expression level serving as a determinant of the magnitude of ferroptotic response. Together, these findings establish ferroptosis as a targetable vulnerability in Ewing sarcoma, define GPX4 and FSP1 as key regulators of ferroptotic sensitivity in this disease, and provide a mechanistic rationale for therapeutic strategies targeting the ferroptosis defense axis in Ewing sarcoma tumors.