Pancreatic cancer has a five-year survival rate of 10% due to low rates of early detection. Oncogenic KRAS mutations are the prevalent driver mutation in pancreatic adenocarcinoma (PDA). In addition, repeated injury to the pancreas (i.e., chronic pancreatitis) contributes to the formation of PDA. During injury to the pancreas, compromised acinar cells reversibly transdifferentiate into ductlike cells via acinar to ductal metaplasia (ADM). In the presence of an oncogenic KRAS mutation, however, ADMs persist and progress into precursor neoplastic lesions and PDA. Previous studies in the lab showed that in the absence of the epigenetic regulator, B lymphoma Mo-MLV insertion region 1 homolog (BMI1), the murine pancreas fully recovers from injury despite oncogenic KRAS expression. To elucidate the role of BMI1 in the transdifferentiation of acinar cells and how it facilitates PDA initiation and progression, we are using an ex-vivo pancreatic cancer acinar culture system to compare the transformation of wildtype acinar clusters to BMI1 knockout (BMI1KO) acinar clusters grown in 3D cell culture. Acinar clusters isolated from the pancreas of wildtype and BMI1KO mice with a tdTomato reporter will be cultured with or without growth factors in a 3D extracellular matrix. The differentiation of the acinar clusters into the duct-like structures in culture will be documented with micrographs in bright field and epifluorescence. Some clusters and cysts will be embedded in paraffin and stained immunohistochemically for different acinar and ductal markers to ascertain the differences in the process of ADM in the presence and absence of BMI1. We expect to see increased duct and cyst formation when BMI1 is expressed compared to its absence and a delay in duct growth and development in the BMI1KO cells. A better understanding of BMI1’s role in PDA initiation and progression will help develop drugs that target BMI1 as a co-therapy for PDA.