Pancreatic cancer modeling in germline BRCA2 mutation carriers

Background: Germline, pathogenic mutations in BRCA2 ( BRCA2 mut ) are the strongest genetic risk factor for pancreatic cancer in men and women; pathogenic variants in this gene are implicated in about 5% of men and women with heritable risks of this cancer type. Moreover, BRCA2 mut are associated with increased risk of pancreatic cancer inHispanic/Latino populations specifically. Patient-specific induced pluripotent stem cell (iPSC) methods create opportunities to modelhuman diseases in vitro . iPSCs derived from patients with known genetic mutations carry thepatient's unique genetic background, to provide platforms for studying the functional effects ofspecific genes. Several inherited disease models created from iPSCs have successfully replicated high-risk cancers. This study aimed to utilize iPSC-based modeling to investigate thefunctional impact of pathogenic BRCA2 mut on early-stage pancreatic tissues (PT) and genomicalterations that contribute to pancreatic cancer (PC) progression. Methods: We generated iPSC from BRCA2 mut positive and BRCA widtype ( BRCA WT ) women and men. From these BRCA2 mut and BRCA WT iPSCs we generated organoid models of pancreatic ductal and acinar precursors. In addition, we used lentiviral targeting to mimic thefunctional effects of specific genes involved in early stage pancreatic cancer pathogenesis, specifically TP53 knockdown (using a TP53 siRNA), and TP53 and/or KRAS overexpression ( TP53 R175H and R273H; KRAS G12V) respectively. Results: Following differentiation into PT organoids heterozygous for BRCA2 mut pancreatic ductal cells show specific cellular abnormalities - neoplastic transformation, ductal formation, expression of cancer-specific biomarkers - compared to BRCA WT controls suggesting that BRCA2 haploinsufficiency contributes to the observed phenotype. PC models from BRCA2 mut subjects exhibit abnormalities reminiscent of early-stage neoplastic development. Importantly, PC organoids with combinations of BRCA2 mut , TP53 and KRAS alterations exhibited a moreaggressive PC phenotypes compared to BRCA2 mut and BRCA WT organoids alone, and sharedgenomic signatures with primary PCs. Conclusion and Impact: iPSC-derived organoids can accurately replicate BRCA2 mut and BRCA WT pancreatic precursor tissues. This allows cancer to evolve in a dish, making it an ideal model for mechanistic studies and screening approaches to identify novel drug targets.