Probes for YAP

Background: Pancreatic ductal adenocarcinoma (PDAC) is the fourth leading cause of cancer deaths with a 5-year survival rate of approximately 7%. PDAC may originate from acinar cell trans-differentiation into ductal-like cells, termed acinar-to-ductal metaplasia (ADM), triggered by chronic pancreatitis and/or mutations in K-Ras. The progression to PDAC is associated with a dense fibrotic stroma, including cancer-associated fibroblasts (CAFs). YAP is a tension-stimulated CAF activator that promotes ECM stiffening, creating a permissive microenvironment for cancer progression. We hypothesize that the Hippo pathway may coordinate fibroinflammatory signals emanating from the stromal compartment during regenerative responses to acinar cell injury and progression towards PDAC. Methods: To resolve the transcriptional changes occurring during the transition to ADM and PDAC, we mapped the in situ expression of over 1800 RNA targets in patient-derived tissues using NanoString Technologies’ Digital Spatial Profiling (DSP) technology. We also performed immune-profiling and evaluated Yap expression in human ADM by immunohistochemistry. To study the in vivo role of Hippo signaling in stromal cells, we conditionally deleted Yap/Taz in Collagen1a2-producing cells in a murine model of caerulein-induced pancreatitis, which recapitulates many of the features associated with human ADM. I will analyze the resulting phenotype by immunostaining for metaplastic, proliferative, immune and stromal markers. Results: DSP analysis revealed genes implicated in fibroblast activation, epithelial-to-mesenchymal transition (EMT), neutrophil activation and IFNγ signaling as potential key drivers of ADM. I will further evaluate the expression of candidate genes and survey Yap expression at the single cell level in human ADM tissue by multiplexed RNAscope in situ hybridization. We found up-regulation of CD4+ and CD8+ T cells in ADM, and an increasing trend of neutrophil and macrophage accumulation in the progression from normal parenchyma to ADM to PDAC. Conclusions: This work will provide an in-depth understanding of epithelial-stroma crosstalk in ADM and a foundation for the development of new therapeutic strategies for treating non-invasive precursor lesions like ADM, thereby preventing pancreatic cancer progression. Source of Funding: This research is supported by the Fonds de Recherce du Quebec - Santé (FRQS), Canadian Institutes of Health Research (CIHR) and the Research Institute of the McGill University Health Centre (RI-MUHC).