The immunofluorescence image depicts DNA double strand breaks (DSBs) occurring in S phase, a critical genetic event where
BRCA2 plays a crucial role in homologous recombination. The colon cancer cell line HT-29 was exposed to SN-38, a topoisomerase-1
inhibitor and treated with bromodeoxyuridine (BrdU). Two-color immunofluorescence staining using anti-BrdU and anti-53BP1
antibodies showed S-phase cell nuclei and the cytoplasm stained in red, together with the DSB nuclear foci detected by anti-53BP1
staining. Credit: M Tahara & K Sugano, Tochigi Cancer Center Research Institute, Tochigi, Japan