Chimeric protein EWS::FLI1 drives cell proliferation in Ewing Sarcoma viaaberrant expression of KCNN1/SK1 and dysregulation of calcium signaling

Ewing sarcoma (ES) is characterized by EWS::FLI1 or EWS::ERG fusion proteins. Knowing that ion channels are involved in tumorigenesis, this work aimed to study the involvement of the KCNN1gene, which encodes the SK1 potassium channel, in ES development. Bioinformatics analyses from databases were used to study KCNN1expression in patients and cell lines. Molecular approaches and in vitro assays were used to study the transcriptional regulation of KCNN1and its involvement in the regulation of ES cell proliferation. KCNN1is overexpressed in ES patient biopsies, and its expression is inversely correlated with patient survival. EWS::FLI1, like EWS::ERG, promotes KCNN1and SK1 expression, binding to GGAA microsatellites near the promoter of KCNN1isoforms. KCNN1is involved in the regulation of ES cell proliferation, with its silencing being associated with a slowing of the cell cycle, and its expression modulates membrane potential and therefore calcium flux. These results highlight that KCNN1is a direct target of EWS::FLI1 and EWS::ERG and demonstrate that KCNN1is involved in the regulation of intracellular calcium activity and ES cell proliferation, making it a promising therapeutic target in ES.