Abstract B097: Cancer-associated fibroblasts in pancreatic ductal adenocarcinoma patients defined by a core inflammatory gene network exhibited inflammatory characteristics with high CCN2 expression

Introduction: Pancreatic ductal adenocarcinoma (PDAC) is a lethal cancer with a prominent extracellular matrix (ECM) deposition and poor prognosis. Cancer-associated fibroblasts (CAFs) actively remodel the ECM and can mediate immune suppression within the PDAC tumor microenvironment (TME). However, CAFs are highly heterogeneous and plastic components of the tumor ECM in PDAC. Previously, we discovered that a core inflammatory gene network (CIGN) associated with poor prognosis serves chemokine production in CAFs in PDAC. The CIGN is defined by two markers (DCBLD2 and PLAU). Subsequently, we focus on ascertaining whether CAFs under CIGN are associated with the current typical classification of CAFs, such as myofibroblastic CAFs and inflammatory CAFs. Method: Before this, we employed bulk RNA seq data of 183 PDAC patients from the Cancer Genome Altas based on 104 inflammatory gene sets from the Molecular Signatures Database to define the CIGN with poor prognosis. We also utilized three scRNA-seq series of PDAC patient tissues to analyze the impact of our CIGN on PDAC TME. Now, to better characterize CAFs in PDAC, CAFs were re-clustered into subclusters by performing the FindClusters function. We identified each cell cluster by comparing the cluster-specific genes to current typical CAF population signatures. Distinct patterns of CAF subclusters were discovered for CIGN positive and negative groups by t-distributed stochastic neighbor embedding. Furthermore, differentially expressed genes were acquired from CAFs under CIGN using differential expression analysis and Gene Ontology enrichment analysis Results: We discovered two CIGN marker genes (DCBLD2 and PLAU) were both found primarily expressed in CAFs, and significantly higher in CAFs of PDAC patients defined by the CIGN (CIGN CAFs) previously. In this study, we found CIGN CAFs tended to be more inflammatory, while non-CIGN CAFs were consisted of a large number of myofibroblastic subtype. The 289 up-regulated Differential Expression Genes (DEGs) from CIGN CAFs were enriched in processes related to connective tissue development, positive regulation of ERK1 and ERK2 cascade, positive regulation of MAPK cascade, positive regulation of JNK cascade, reactive oxygen species metabolic process, collagen-containing extracellular matrix, growth factor binding. CCN2 was the only one among 289 up-regulated DEGs involved in multiple functions of CIGN CAFs, such as biological process, cell component, and molecular function, including but not limited to those listed above. CCN2 (CTGF, connective tissue growth factor) is a matricellular protein of the CCN family of extracellular matrix-associated heparin-binding proteins. Conclusion: CAFs in PDAC patients defined by the CIGN exhibited inflammatory characteristics with high CCN2 expression. As abundant tumour-promoting cells in the ECM, CAFs are promising targets for novel anti-tumour interventions. Fundings: Hong Kong Theme-based Scheme (T12-201/20-R).