Project Summary Pancreatic ductal adenocarcinoma (PDAC) is the fourth most lethal neoplasm in the US with 5- year-survival rate of 8.5%. Currently, gemcitabine single agent or combination chemotherapies remain the most commonly used frontline treatment for locally invasive and metastatic PDAC. However, most PDAC tumors are intrinsically resistant or quickly acquire resistance to gemcitabine. Epigenetic reprogramming through changes in global DNA methylation or histone modification have been implicated in chemoresistance. Here, I established a model for gemcitabine resistance progression in PDAC and identified a cytostatic transition phase prior to regrowth under gemcitabine treatment. Through a small-molecule epigenetic inhibitor screen, I identified PRMT1 (H4R3 arginine methyltransferase) and KMT2A/B (H3K4 lysine methyltransferase) as positive and negative regulators of transition into gemcitabine resistance, respectively. Based on these findings, I hypothesize that PDAC cells transition into gemcitabine resistance through epigenetic reprogramming that is in part mediated by PRMT1 and KMT2A/B. In Aim 1, I will functionally validate PRMT1 and KMT2A/B in modulating PC gemcitabine resistance in vitro and in vivo. In Aim 2, I will investigate the mechanisms by which PRMT1 and KMT2A/B modulate gemcitabine resistance through integrated genomic analysis. Collectively, I expect my study will shed important new insight into the mechanisms of gemcitabine resistance in PDAC, which could lead to novel combination therapies to enhance the efficacies and durability of gemcitabine in PDAC.