PRMT1 Promotes Epigenetic Reprogramming Associated with Acquired Chemoresistance in Pancreatic Cancer

Pancreatic Ductal Adenocarcinoma (PDAC) is associated with extremely poor prognosis due to late diagnosis and therapeutic resistance. Here we show that PDAC cells undergo progressive reprogramming of the global epigenetic landscape during the process of acquiring chemoresistance. Through an epigenetic inhibitor screen, we identified Protein Arginine methyltransferase 1 (PRMT1) as a central driver of chemoresistance in PDAC. Genetic or pharmacological inhibition of PRMT1 impaired adaptive epigenetic reprogramming, sensitized PDAC cells to Gemcitabine and other commonly used chemo drugs, and delayed the development of acquired resistance both in vitro and in vivo. Mechanistically, we find that PRMT1, through its enzymatic activity, limits the accumulation of small bZIP transcription factor MAFF in the nucleus, and the assembly of chromatin-bound MAFF/BACH1 hetero-oligomeric complexes following Gemcitabine treatment. Genetic silencing of MAFF heightened the resistance of PDAC cells to Gemcitabine, and to combination of Gemcitabine and PRMT1 inhibitors. Cut&Tag chromatin profiling of H3K27Ac, MAFF and BACH1 suggests a pivotal role for MAFF/BACH1 in orchestrating global epigenetic reprogramming during the course of acquiring Gemcitabine resistance. Supporting the clinical relevance of our findings, predicted PRMT1 and MAFF/BACH1 genes signatures based on our Cut&Tag analysis were able to distinguish Gemcitabine-resistant from Gemcitabine-sensitive PDAC patient-derived xenografts according to expression changes induced by Gemcitabine. Together, our study reveals a novel epigenetic regulatory axis involving PRMT1 and MAFF/BACH1 that modulates Gemcitabine response, which could be potentially exploited for improving therapeutic response in advanced PDAC.