Fig. 4

Niraparib increases double strand breaks and Rad51 recruitment induced by irinotecan. Two non-synergistic (a) and two synergistic (b) cell lines were immunostained for γH2Ax and Rad51 after 24 h incubation with low concentrations of the indicated agents (niraparib 100 nM, SN38 1 nM, or their combination). SN38 and combination treatment are able to induce DSBs marked by γH2Ax foci in all cell lines, while Rad51 foci are increased in synergistic cell lines (HCT116 and SW480) and in WIDR but are not increased in LS1034. c: co-localization of γH2Ax and Rad51 foci is increased in synergistic cell lines. d: γH2Ax and Rad51 colocalization foci are significantly increased with combination treatment compared to SN38 single agent in synergistic HCT116 and SW480 cell lines. *: p < 0.05, ****: p < 0.0001