Genome stability is maintained by multiple, partially compensatory pathways of DNA repair, including homologous recombination (HR). Loss of genome stability is a hallmark of cancer and many malignant tumours have defects in HR. In particular, at least 14% of triple-negative breast cancers lack effective HR because of genetic or epigenetic loss of key HR proteins e.g. BRCA1 or BRCA2. In such tumours, the loss of BRCA1/2-dependent HR means that other compensatory DNA repair pathways become essential for tumour viability. Targeting these compensatory pathways is an opportunity for tumour-specific cell killing; a concept known as "synthetic lethality". For example, the inhibition of poly(ADP-ribose) polymerase I (PARP), required for the repair of DNA single-strand nicks, has had significant success in treatment of cancers with HR-deficiency e.g. BRCA1/2-mutants. But several modes of resistance to PARP inhibition have been uncovered. Recent discoveries suggest that a second route to "synthetic lethality" exists for BRCA1/2 deficient cancers: targeting of the Fanconi Anaemia (FA) DNA repair pathway. We hypothesise that chemical inhibition of the "FA core complex", an E3 ligase complex critical in the FA pathway, will selectively kill BRCA1/2 deficient cancers.
The over-arching aim of the laboratory is to understand mechanistically the synthetic lethal relationship between the FA pathway and BRCA1/2-dependent DNA repair in TNBC cells. We have developed unique tools for the genetic and biochemical investigation of the FA and BRCA1/2 pathways, which enables the project using two complementary strategies: 1) Development of proof-of-principle inhibition of the E3 activity of the FA core complex and 2) genetic analysis of the synthetic lethal relationship between BRCA1/2 and the FA pathway.
We are identifying new synthetic lethal relationships with BRCA1/2-deficient cells and creating the pharmaceutical tools to exploit them.