EWSR1 and Ewing sarcoma: Furthermore, there is also evidence that MMP1 is a direct target of EWS/ETS proteins, as a previous study has shown that EWS-ETV1 (ER81) and EWS-FLI1 fusion proteins can interact with the MMP1 promoter and collaborate with c-Jun and the cofactor p300 to activate MMP1 gene transcription in vitro [49]: But in our hands, EWS-FLI1 knock down suppressed MMP1 expression only in A673 cells but not in other ES lines.