MRC1 and Ewing sarcoma: In this MMR-proficient cancer cell line, the level of 53BP1 foci was high, similarly to MMR-deficient or TL+ Ewing sarcoma cell lines, whereas RAD51 foci were obviously less frequent, which implies that DSBs caused in SW620 cells are at a level similar to those in the other cell lines, and that the HR-processed fraction is however relatively limited.