Characterizing the NF-κB signaling pathway in Arid1a-deficient PDAC subtypes

Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive, fast proliferating disease with an overall 5-year survival rate of less than 8%. Although therapeutic options have increased within the last years, the extreme molecular heterogeneity remains a major problem. In order to target the genetic background of the different tumor subtypes, patient individualized and subtype-specific therapies are an important opportunity. The tumor suppressor gene ARID1A, a member of the SWI/SNF chromatin remodeling complex, is often mutated in different tumor entities. Its loss of function correlates with inflammatory phenotypes. In 20% of PDAC specimen a mutation along with a loss of function of ARID1A could be shown. Therefore, targeting inflammatory pathways such as the NFκB-signaling or the JAK-STAT pathway may be a potential therapeutic strategy in ARID1A-deficient tumor subtypes. To investigate the role of ARID1A loss in controlling the inflammatory environment, IHC staining was performed comparing PDACs in mice with or without conditional ARID1A mutation. Different TFs in ARID1A wildtype and knockout (CRISPR/CAS9) cells were analyzed using Western blot and immunofluorescence. QRT-PCR and cytokine ELISA demonstrated the upregulated expression of inflammatory cytokines. Luciferase assays were used to analyze the transactivation of a NFκB-responsive Promoter. The functional effects of blocking inflammatory signaling pathways were investigated by Annexin/PI- and BrdU-based flow cytometry. Cytokine expression and secretion were upregulated in the context of ARID1A loss. The analysis of the JAK-STAT and the NFκB-signaling pathways showed an increased activation in different signaling specific subunits and an enhanced transcription of target genes. Additionally, Annexin/PI staining revealed an ARID1A-dependent induction of apoptosis. Loss of ARID1A expression leads to an upregulation of inflammation, a trigger of carcinogenesis. A change in the transcription of cytokines resulted in increased secretion of inflammatory cytokines in the context of ARID1A-deficiency. Therefore, targeting inflammatory signaling pathways such as the NFκB or the JAK-STAT pathway could be a promising therapeutic option in ARID1A-deficient PDAC.2021-08-2