Given that XRCC3 deficiency causes a high level of sensitivity to olaparib in the DU145 prostate cancer cell line, and that RAD51C loss phenocopies PARPi sensitivity caused by BRCA2 loss in the ovarian cell line SKOV3, while the same is not true for the other BCDX2 complex component RAD51B, it is tempting to speculate that there is a more important function of the CX3 RAD51 paralog complex in mediating PARPi responses. The gene discussed is RAD51B; the disease is Familial prostate cancer.