RAD51 and cancer: Cancers carrying defects in BRCA-1 are known to be more susceptible to the cytotoxic effect of PARP inhibitors [22], and therapeutic strategies able to reduce the expression of BRCA-1 as well as other HR molecules, such as RAD51 [23], or to exacerbate DNA damage [24] can be used to potentiate the cytotoxicity of PARP inhibitors.