It is likely noteworthy that LuCaP 96 expressed WT TP53, and previous analyses of BRCA1/2–deficient breast cancer PDXs have suggested that approximately 25% are nonresponsive to PBD, a phenotype that may be associated with a less compromised HRD resulting from minimal mutations to additional DNA repair proteins, including TP53 (31, 32). Here, XRCC6P5 is linked to breast cancer.