Rad51 focus formation in BRCA2 -mutated cell lines. a. Cells were treated for 8 hours with MMC (2.4 μg/mL) and immunolabeled for RAD51 (green) and DAPI (blue). MIP101 and RKO are colorectal MSI cancer cells harboring BRCA2 frameshift mutations (see text). BRCA2-/- cells (EUFA423/FA-D1) are derived from a Fanconi anemia patient with complementation group D1/BRCA2 b. Cells were treated with MMC (2.4 μg/mL) or ionizing radiation (12 Gy); after recovery for 8 or 24 hours, cells were stained for RAD51. RAD51 foci were counted and the percentage of cells with > 5 foci was determined. FN1 and VH10 are nonneoplastic BRCA2- wildtype cells.