Sin3B loss enhances the T-cell inflamed tumor microenvironment through the redistribution of H3K27Ac signals in pancreatic cancer [RNA-seq]
Pancreatic ductal adenocarcinoma (PDAC) displays a poor response to immunotherapy. This poor response is predominantly attributed to the highly immunosuppressive tumor microenvironment (TME), characterized by a scarcity and dysfunction of infiltrating CD8+ T cells. Epigenetic regulators have recently been implicated in immune escape and immunotherapy sensitivity, presenting an appealing approach for directly targeting epigenetic factors or combining epigenetic therapies with immunotherapy in PDAC. Our study is the first to delineate the regulatory function of the epigenetic factor Sin3B in the tumor immune microenvironment (TIME) of PDAC. Using murine PDAC models, we discovered that intrinsic Sin3B loss in tumor cells reshapes the TIME, manifested by increased CD8+ T cell infiltration into tumors through enhanced secretion of  CXCL9 and CXCL10. This was accompanied by an increase in the cytotoxicity of CD8+ T cells, as evidenced by elevated Granzyme B (GzmB) and IFN? production. Furthermore, Sin3B-deficient tumor cells exhibited heightened secretion of CXCL9/10 in response to IFN?, creating a positive feedback loop via the CXCL9/10-CXCR3 axis and thus intensifying immune response against PDAC. Additionally, loss of Sin3B increased PDAC susceptibility to anti-PD1 therapy in mice. Corroborating our findings in the mouse model, analysis of human PDAC samples demonstrated a significant inverse correlation between Sin3B levels and both CD8+ T cell presence and CXCL9/10 expression. Notably, PDAC patients with lower Sin3B expression exhibited a more favorable response to anti-PD1 therapy. Concerning the mechanism, we systematically uncovered the extensive epigenetic regulation employed by Sin3B loss via the modulation of H3K27Ac redistribution in PDAC cells. Sin3B deficiency resulted in an uptick of H3K27Ac peaks concentrated in the promoter and enhancer regions. Under the treatment of IFN?, Sin3B loss leads to the enrichment of H3K27Ac peaks in promoter regions of ISG-related genes such as CXCL9 and CXCL10, thereby boosting their expression. Collectively, our research outcomes propose a potential target for enhancing the accessibility of cytotoxic T cells to the tumor site and improving immunotherapy in the challenging landscape of PDAC. Overall design: To investigate the function of Sin3B regulating TIME of PDAC, wo conducted Sin3B KO and WT KPC1199 cells. Then, we performed RNA sequencing to analyse gene expression profile of Sin3B KO and WT cells.