Abstract PR07: Unravelling the epigenetic landscape of pancreatic cancer: The role of cancer-associated fibroblasts

Abstract

Abstract Pancreatic cancer is set to become the 3rd deadliest cancer by 2025. Pancreatic ductal adenocarcinoma (PDAC) represents the majority of cases and is the most aggressive subtype, with a 5-year survival rate of around 10% and patients often diagnosed at a metastatic stage. Current treatments offer dismal survival benefit for the patients, highlighting the need for innovative therapeutic strategies. PDAC is characterized by genetic and epigenetic modifications and an abundant tumor microenvironment (TME) largely composed of cancer-associated fibroblasts (CAFs). Multiple populations of CAFs have been described and implicated in PDAC progression, however, little is known regarding the molecular crosstalk between them and the cancer cells. This project aims to investigate how the epigenetic landscape of PDAC is affected by recently described CAF populations. We have optimized a co-culture model consisting of cancer cells and genetically-locked inflammatory CAFs (iCAFs) and myofibroblastic CAFs (myCAFs) to study the link between the TME and the gene regulatory machinery in PDAC through proteomic and genomic approaches. Firstly, a full proteome analysis revealed the two CAF populations drive expression of different subsets of proteins in PDAC cells, including transcription factors. We then interrogated chromatin accessibility via ATAC-seq, which showed that CAF subsets differentially affect chromatin dynamics in epithelial cells. Transcription factor interactomes were investigated using rapid immunoprecipitation of endogenous proteins (RIME), a method developed in our lab that allows the discovery of protein complexes in a robust manner. We leverage this technique to discover druggable transcription factor interactors. RIME data shows that upon co-culture with each CAF population, distinct interactors are recruited towards FOXA1, a pioneer factor that drives a transcriptional program associated with PDAC metastasis to the liver, and towards FOXA2, which has been shown to play distinct roles in different grades of PDAC. We are now assessing the potential of these interactors as drug candidates in each context. Chromatin immunoprecipitation assays have shown that the CAF populations also affect the binding profile of FOXA1 and FOXA2 to the chromatin. We are currently investigating how CAFs impact tumor progression in vivo using an orthotopic implantation model. Preliminary data suggests that CAF subsets affect the metastatic profile in PDAC, as tumors co-injected with iCAFs metastasize to different organs than those co-injected with myCAFs. Ongoing experiments aim to explore the differences between tumors and metastases at the epigenetic level. Subsequent studies will aim to employ distinct approaches that target tumor progression in each context. PDAC is a highly heterogeneous cancer with several layers of complexity; therefore, a more holistic approach is critical to tackle the disease. Understanding tumor-stroma interactions from an epigenetics standpoint may enable identification of druggable molecules much needed for PDAC patients. Citation Format: Catarina Pelicano, Igor Chernukhin, Lisa Young, Naomi Vranas, Yi Cheng, Joshua Kent, Kamal Kishore, Clive D'Santos, Alasdair Russell, Giulia Biffi, Shalivi V. Rao, Jason S. Carroll. Unravelling the epigenetic landscape of pancreatic cancer: The role of cancer-associated fibroblasts [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Pancreatic Cancer; 2023 Sep 27-30; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84(2 Suppl):Abstract nr PR07.