Analysis of the DSB marker 53BP1 revealed the presence of a higher number of 53BP1 foci in HCT116 cells treated with EM127 (Fig. 5E, Supplementary Fig. 2D, 0 h time point), suggesting that this novel SMYD3 covalent inhibitor increases the amount of unrepaired endogenous DSB lesions, as previously reported with the reversible inhibitor BCI-121 in BC cells [20]. Here, TP53BP1 is linked to breast cancer.