FOS and Ewing sarcoma: However, transcriptome and gene set enrichment analysis (GSEA) also identified that a decrease in RNR activity in Ewing sarcoma cells results in the upregulation of c-Jun and c-Fos, which are members of the activator protein-1 (AP-1) transcription factor family, and the downregulation of the c-Myc oncogene (23, 24).