Whole genome and transcriptome analysis of pancreatic acinar cell carcinoma elucidates mechanisms of homologous recombination deficiency and unravels novel relevant fusion events.

Pancreatic acinar cell carcinoma (PACC) is a rare pancreatic tumor with a heterogeneous clinical course and, except for radical surgery, limited treatment options. We present a comprehensive study encompassing whole-genome and RNA sequencing of 7 tumor samples from 3 metastatic PACC patients to further delineate its genomic landscape and potential therapeutic implications. Our findings reveal distinct signatures of homologous recombination deficiency (HRD) in patients harboring pathogenic germline BRCA1/2 and FANCL mutations, demonstrating favorable responses to poly (ADP-ribose) polymerase 1 (PARP) inhibitors with prolonged disease-free intervals. Additionally, we first describe structural variants in PACC, including BRCA1::TRIM47 fusion and another variant impacting FANCC, both events related to HRD, and we also identify alterations in the mitogen-activated protein kinase (MAPK) pathway, including RAF1 duplication as well as novel BRAF::SORBS2 and MAP7D2::SND1 gene fusions, offering potential targets for therapy. Our study underscores the importance of genome and transcriptome-wide profiling of PACC, to help guide personalized treatment strategies to improve patient outcomes.