XRN2 and triple-negative breast carcinoma: Similarly, XRN2 deficient cells, fibroblast or MDA-MB-231 cells, a triple negative breast cancer cell line [38], were hypersensitive to various genomic insults as illustrated by decreased colony forming ability after exposure to IR, aphidicolin (APH) or hydrogen peroxide (H2O2) (Fig 3A, 3B, 3E and 3F).