In this study we ask whether SETD1A-induced PARPi resistance is specific to BRCA1-deficiency or whether it could be broadly applicable to other HR deficient cancers, focusing on those deficient in ATM or BRCA2. To do so, we assessed cellular survival and DNA repair kinetics in response to Olaparib in a range of HR-deficient cell lines in the presence/absence of SETD1A. Here, BRCA1 is linked to cancer.