Abstract LB235: Prrx1 regulates acinar cell plasticity via TGFβsignaling in pancreatic acinar-to-ductal metaplasia

Abstract Introduction: Acinar cells undergo de-differentiation after injury to a progenitor-like cell type with ductal characteristics termed acinar-to-ductal metaplasia (ADM). In the absence of oncogenic mutation, the ADM lesions resolve and reform the acinar compartment (we terms this as adaptive ADM). However, in the presence of oncogenic Kras mutations (we terms this as oncogenic ADM), acinar cells undergo neoplastic transformation after ADM and evolve to pancreatic intraepithelial neoplasia (PanIN), a well-known precursor of pancreatic ductal adenocarcinoma (PDAC). Herein, we explore the role of the Paired-Related Homeobox1 transcriptional factor (Prrx1) in adaptive ADM and the relationship between Prrx1 and mutant Kras in oncogenic ADM. Methods: We generated tamoxifen-inducible Ptf1aCreERT;Rosa26YFP/YFP (abbreviated as Prrx1cWT) mice and bred in the Prrx1fl/fl allele to make (abbreviated Prrx1cKO) mice and subjected them to caerulin (CCK analog) induced acute pancreatitis, a well-estabished model. We created a time course for both mouse genotypes subjected to acute pancreatitis for histological analysis. Quantification of ADM was performed through automated cell-counting of immunofluorescence (IF) staining. Then, we performed 3D ex vivo acinar cultures of Prrx1cWT and Prrx1cKO mice. We used an exogenous adenoviral vector to induce Cre expression and knock out Prrx1, using an empty vector as a control. Dissociated acinar cell cultures in collagen were utilized for the evaluation of TGFβ signaling by western blotting (WB). Additionally, we generated novel Pdx1-Cre;LSLKrasG12D/+;Prrx1fl/fl;Rosa26YFP/YFP (KCY Prrx1 KO) mice, in which mutant Kras is efficiently expressed and Prrx1 is deleted in a pancreas-specific manner. KCY Prrx1 WT and KO mice were sacrificed at 3 months and 5 months for histological analysis. Results: IF staining revealed that Prrx1cKO mice had fewer ADM lesions compared to Prrx1cWT mice at Day 3 post-caerulein. Ex vivo cultures demonstrated a substantial increase of cystic structures, which are representative of ADM in Prrx1cWT cultures compared to Prrx1cKO cultures. Additionally, using a novel nucleofection protocol, we demonstrated that overexpression of the Prrx1b isoform (associated with a progenitor cell state) leads to a notable increase in ADM. WB of acinar protein lysates from either Prrx1cWT or Prrx1cKO mice showed significant differences in TGFβ levels, and a 2-fold higher expression of phosphorylated SMAD2 in Prrx1cWT mice. IF staining also showed that KCY Prrx1 KO mice had fewer ADM lesions compared to Prrx1 WT mice at at the 5 months time point. Conclusions: Prrx1 can influence adaptive ADM formation. Moreover, Prrx1 can influence ADM formation in the presence of oncogenic KRAS. Our data suggest that Prrx1 facilitates PDAC progression through ADM formation. Citation Format: Noriyuki Nishiwaki, Kensuke Sugiura, Alina Li, Kensuke Suzuki, Jason R. Pitarresi, Rohit Chandwani, Anil K. Rustgi. Prrx1 regulates acinar cell plasticity via TGFβsignaling in pancreatic acinar-to-ductal metaplasia abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (7Suppl): Abstract nr LB235.