BRCA1 and ovarian cancer: Similarly, downregulation of TOPBP1 was also demonstrated in BRCA1-proficient OVCAR3 ovarian cancer cells, however, unlike Zhang et al.71 and our model, in that study, JQ1 alone did not elicit DNA damage nor PARP cleavage products in OVCAR3 cells, but synergized with the PARP inhibitor Olaparib to increase DNA damage and tumor cell killing in vivo72.