Among various types of breast cancers, TNBC is unique, not only in its hormone receptor status but also in its association with high levels of endogenous DNA damage manifested by a gene expression profile enriched with DNA damage response genes6 and by histological observation in clinical samples.30 We showed here that in all TNBC cell lines examined there were increased levels of γH2AX. This evidence concerns the gene NR4A1 and breast cancer.