OVCAR8 cells transfected with nontargeting siRNA (siRNA control) or siRNA targeting 53BP1 (si53BP1) were subjected to immunoblotting (A) or formalin fixed, embedded in paraffin, and stained to confirm specificity of the anti-53BP1 antibody (B, C). D, cores from the same ovarian cancer included on two different TMAs were independently stained with anti-53BP1 and scored. E, 53BP1 staining of four ovarian cancers to illustrate range of expression in the present study.