E2F1 and ovarian cancer: In particular, Vorinostat [72] and Panobinostat [73], two histone deacetylase inhibitors (HDACis), were shown to downregulate genes implicated in HR DNA repair, such as cyclin E, E2F1, and BRCA1, in HR-proficient ovarian cancer cells, leading to synergistic enhancement of cytotoxicity when these compounds were combined with the PARPi Olaparib.