Targeting BARD1 suppresses a Myc-dependent transcriptional program and tumor growth in pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) remains one of the deadliest cancers demanding better and more effective therapies. BARD1 or BRCA1-Associated -Ring Domain-1 plays a pivotal role in homologous recombination repair (HRR). However, its function and the underlying molecular mechanisms in PDAC are still not fully elucidated. Here, we demonstrate that BARD1 is overexpressed in PDAC and its genetic inhibition suppresses c-Myc and disrupts c-Myc dependent transcriptional program. Mechanistically, BARD1 stabilizes c-Myc through ubiquitin-proteasome system by regulating FBXW7. Importantly, targeting BARD1 using either siRNAs or CRISPR/Cas9 deletion blocks PDAC growth in vitro and in vivo, without any signs of toxicity to mice. Using a focused drug library of 477 DNA damage response compounds, we also found that BARD1 inhibition enhances therapeutic efficacy of several clinically relevant agents (fold changes ≥4), including PARPi, in HRR proficient PDAC cells. These data uncover BARD1 as an attractive therapeutic target for HRR proficient PDAC.