In this study, using a panel of endometrial cell lines, we focused on (i) the anti-tumor effect of olaparib and its relationship with PTEN status, (ii) the association between PTEN and HR-related proteins (RAD51 and γ-H2AX), and (iii) the relationship between PTEN status and the response to IR exposure (another DNA damaging therapy). This evidence concerns the gene RAD51 and neoplasm.