ATF1 and clear cell sarcoma: Weak or non-specific PLA signals are detectable in cells lines of other cancer subtypes (including three sarcomas bearing different fusion oncoproteins): MCF7 (breast carcinoma), HeLa (cervical carcinoma), A673 (Ewing sarcoma, EWS-FLI1) (Figure 1A), 402-91 (myxoid liposarcoma, FUS-DDIT3), SU-CCS-1 (clear cell sarcoma, EWS-ATF1), as well as single antibody, no antibody, and non-specific antibody conditions (Supplementary Figure 1A).