Loss of Rnf43 to accelerate KRAS-mediated neoplasia in a clinically relevant genetically engineered mouse model of pancreatic adenocarcinoma.

Abstract

733 Background: The genetic heterogeneity of pancreatic ductal adenocarcinoma (PDAC) demands a personalized molecular-targeted treatment approach. While activating KRAS mutations are a near ubiquitous event in PDAC pathogenesis, 5-10% of cases display deleterious driver mutations in the Wnt-signaling negative regulator, ring finger 43 (RNF43). Despite this characterization there are no personalized treatment options for this subset of patients. Methods: We have developed a genetically engineered mouse model (GEMM) of PDAC, driven by an activating mutation in Kras and deletion of Rnf43 under control of a pancreas specific promoter (KRC). Mice were followed for survival outcomes and histological changes which were compared to a Kras driven PDAC GEMM (KC). Mice underwent serial magnetic resonance imaging (MRI), with and without dynamic contrast enhanced (DCE) imaging, to evaluate cystic tumor morphology and contrast enhancement during tumor progression. Single cell RNA sequencing (scRNAseq) was also performed to assess changes in single cell populations during tumor progression. Lastly, we established ex vivo cultures from KRC and KC tumors and performed bulk RNA-sequencing (RNAseq) and in vitro pharmacology studies. Results: KRC mice displayed a decrease in overall survival and higher incidence of both high grade pre-neoplastic lesions and invasive PDAC compared to KC mice. Serial MRI revealed increased cystic morphology of KRC mice during tumor progression with increasing DCE intensity. scRNAseq of KRC tumors from moribund mice displayed two distinct populations of both macrophages and fibroblasts, similar to our previous report of Kras/Tp53 and Kras/Ink4a driven GEMMs. Lastly, primary cultures from KRC tumors demonstrated increased expression of Wnt-related genes by RNAseq and increased sensitivity to small molecule porcupine inhibition relative to KC cell lines, demonstrating functional Wnt dependence of the KRC system. Conclusions: Rnf43 is a bona fide tumor suppressor gene in PDAC. This GEMM is a novel platform for drug discovery in RNF43-mutated PDAC with the eventual goal of implementing a precision oncology approach in these patients.