Concordantly, further IHC analysis of tumor tissues showed significantly reduced expression of HR repair protein Rad51 and c-NHEJ factor Ku80 in the combination group compared with single-agent alone (Fig. 6c), indicating accumulation of DNA double-strand breaks due to the attenuated DSB repair activity upon a CUDC-907 and olaparib combination. Here, XRCC5 is linked to neoplasm.