Isogenic pairs of cell lines allow gene mutations to be studied without the potentially confounding influence of othergenetic factors and offers an attractive method for performing synthetic lethality screens. The permanent and specific nature of the gene targeting technology overcomes limitations of RNA interference strategies such as transient gene disruption and off-target effects. In addition, the isogenic system can be used throughout the drug discovery process, to identify and validate novel targets both in vitro and in vivo.
A classic example of sythetic lethality is the observation that cancers containing mutations in BRCA1/2 are exquistitely sensitive to poly (ADP ribose) polymerase (PARP) inhibitors, which abrogate the repair of DNA single-strand breaks.
The Horizon Discovery catalogue of cell lines includes a pair of DLD-1 cell lines, which are genetically identical except for their BRCA2 status. Targeted disruption of BRCA2 exon 11 was performed using rAAV gene editing technology to generate DLD-1 BRCA2 (-/-) cells3. Historically, cell lines such as Capan-1 have been used to model BRCA2 deficiency1. However, these cell lines are often compared to cell lines that differ not only in BRCA2 status but also differ with respect to other gene mutations.
Comparison of wildtype and BRCA2 mutant cells found that mutants clearly demonstrate sensitivty to PARP inhibitors, exemplifying the concept of synthetic lethality (Figure 1).