PARP1 and neoplasm: In the clinic, the use of poly(adenosine diphosphate [ADP]-ribose) polymerase (PARP) inhibitors to successfully treat tumours carrying mutations in the breast cancer susceptibility genes, BRCA1/BRCA2 (Lord and Ashworth, 2017), has validated the approach and driven the search for other clinically relevant gene pairings, including those that confer synthetic lethality in cancer cells expressing oncogenic mutations in KRAS (Luo et al., 2009; Wang et al., 2017).