ATF1 and sarcoma: Among these were epithelial carcinoma cell lines (UMRC2 and 786-O), a clear cell sarcoma cell line with the oncogenic EWS::ATF1 rearrangement (SU-CCS-1), and two primary cell lines that either express FLI1 (HUVEC) or do not express FLI1 (RPTEC) (Figure 3B).