Abstract PO-075: The elucidation of the role of Prrx1 for acinar to ductal metaplasia in response to acute injury of pancreas in the novel mouse models

Introduction: Pancreatic acinar cells can de-differentiate after acute injury (acute pancreatitis) to a progenitor-like cell type with ductal characteristics in a process termed acinar-to-ductal metaplasia (ADM). In the absence of oncogenic mutation, the ADM lesions resolve and reform the acinar compartment (adaptive ADM). However, in the presence of oncogenic Kras mutations (oncogenic ADM), ADM lesions can evolve to pancreatic intraepithelial neoplasia (PanIN) and pancreatic ductal adenocarcinoma (PDAC). Our comprehensive and unbiased approach previously identified the Paired-Related homebox1 (Prrx1) as the most up-regulated transcription factor during pancreatic development, regeneration and evolution of PanIN. We showed that Prrx1 expression is upregulated in both ADM and PanIN lesion. Here, we explore the role of Prrx1 in ADM and PanIN formation using novel mouse models, ex vivo acinar culture systems, and human pancreatitis tissue microarrays (TMA). Methods: We generated novel Ptf1acre-ERT;Prrx1fl/fl;Rosa26YFP/YFP (Prrx1 KO) mice, in which Prrx1 is deleted and YFP is expressed exclusively in adult pancreatic acinar cells upon tamoxifen induction of Cre recombinase activity. Intraperitoneal caerulein injection was administered to induce acute pancreatitis. Human pancreatitis TMAs were utilized for the comparison of Prrx1 expression between pancreatitis and normal human pancreas. We also generated Pdx1Cre;LSL-KrasG12D/+; Prrx1fl/fl;Rosa26YFP/YFP (KCYPrrx1KO) mice to evaluate the function of Prrx1 in oncogenic Kras mutation induced pancreatic PanIN. Quantification of ADM regions was performed through histological examination by a pathologist (blinded to the genetic basis of the tissues) and automated cell-counting of immunofluorescence staining (IF). Dissociated acinar cell culture in collagen was utilized for the evaluation of ADM under ex vivo conditions. We also established a novel method for the induction of Prrx1 overexpression in dissociated acinar cells via nucleofection. Results: IF staining revealed that Prrx1 expression is efficiently deleted in ADM cells of Prrx1 KO mice 3 days post-caerulein treatment, a timepoint at which we see peak ADM region formation. Additionally, areas of ADM lesions and amylase loss were significantly reduced in Prrx1 KO mice compared with Prrx1 WT mice at day 3. We also found that Prrx1 overexpression promotes ADM formation in ex vivo acinar cell cultures. In human TMAs, pancreatitis tissues had higher expression of Prrx1 than in normal pancreas. In the presence of oncogenic Kras mutation, loss of Prrx1 significantly attenuates ADM formation in ex vivo culture. Moreover, 5-month-old KCYPrrx1KO mice have very limited ADM/PanIN region compared to 5-month-old KCY mice, which have a pancreas that has predominantly replaced the ADM/PanIN. Conclusions: Prrx1 promotes ADM formation in both adaptive ADM and oncogenic ADM. Our preliminary data suggest that Prrx1 facilitates PDAC progression through PanIN formation. Citation Format: Kensuke Suzuki, Alina Li, Jason R. Pitarresi, Anna M. Chiarella, Gizem Efe, Kensuke Sugiura, Rohit Chandwani, Anil K. Rustgi. The elucidation of the role of Prrx1 for acinar to ductal metaplasia in response to acute injury of pancreas in the novel mouse models [abstract]. In: Proceedings of the AACR Virtual Special Conference on Pancreatic Cancer; 2021 Sep 29-30. Philadelphia (PA): AACR; Cancer Res 2021;81(22 Suppl):Abstract nr PO-075.