High 4E-BP1 expression associates with chromosome 8 gain and CDK4/6 sensitivity in Ewing sarcoma

Chromosome 8 (chr8) gains are common in cancer, but their contribution to tumor heterogeneity is largely unexplored. Ewing sarcoma (EwS) is defined by FET::ETS fusions with few other recurrent mutations to explain clinical diversity. In EwS, chr8 gains are the second most frequent alteration, making it an ideal model to study the relevance of chr8 gains in an otherwise silent genomic context. We report that chr8 gain-driven expression patterns correlate with poor overall survival of patients with EwS. This effect is mainly mediated by increased expression of the translation initiation factor binding protein 4E-BP1, encoded by EIF4EBP1 on chr8. Among all chr8-encoded genes, EIF4EBP1 expression showed the strongest association with poor survival and correlated with chr8 gains in EwS tumors. Similar findings emerged across multiple cancer entities in The Cancer Genome Atlas. Multiomics profiling revealed that 4E-BP1 orchestrates a pro-proliferative proteomic network. Silencing 4E-BP1 reduced proliferation, clonogenicity, spheroidal growth in vitro, and tumor growth in vivo. Drug screens demonstrated that high 4E-BP1 expression sensitizes EwS to pharmacological CDK4/6-inhibition. Chr8 gains and elevated 4E-BP1 emerge as prognostic biomarkers in EwS, with poor outcomes driven by 4E-BP1-mediated pro-proliferative networks that sensitize tumors to CDK4/6 inhibitors. Testing for chr8 gains may enhance risk stratification and therapy in EwS and other cancers.