CircERC1 facilitates chemoresistance through inhibiting pyroptosis and remodeling extracellular matrix in pancreatic cancer.

BACKGROUND: Pancreatic ductal adenocarcinoma (PDAC) resists to neoadjuvant treatment even though overall survival (OS) is transiently prolonged while the underlying mechanism of this drug resistance remains elusive. METHODS: Gemcitabine combined with Nab-paclitaxel (GEM-NabP) treated PDAC tissues-derived EVs were isolated and underwent circRNA sequencing. CircERC1 was identified as an EVs-packaged circRNA that regulates PDAC progression and tumor microenvironment (TME) in vitro and in vivo with the help of EdU, colony formation, SRB viability assays, transwell assays and PET-CT analysis. The underlying mechanism was substantiated by qRT-PCR, Western blot, RNA pull-down, mass spectrometry, RNA immunoprecipitation and Co-immunoprecipitation. In addition, single-cell RNA sequencing was adopted to analyze the TME and immunohistochemistry, dual luciferase reporter assay were performed to validate the results. RESULTS: CircERC1 biogenesis is activated by QKI after GEM-NabP treatment. It interacts with hnRNPA1 and promotes its ubiquitination degradation by blocking its SUMOylation at K183. The degraded hnRNPA1 fails to upregulate PKM2, a crucial activator of NLRP3 inflammasome, thereby inhibiting Caspase1-GSDMD mediated pyroptosis. Furthermore, EVs-packaged circERC1 enhances extracellular matrix (ECM) deposition and hindering drug and immune cells infiltration in cancer associated fibroblasts (CAFs) in PDAC microenvironment. CONCLUSIONS: Our findings reveal a novel circERC1 as a key regulator in PDAC-secreted EVs following paclitaxel (PTX) treatment, thereby inhibiting gemcitabine/Nab-paclitaxel (GEM-NabP) induced pyroptosis. Our results highlight a potential therapeutic target for overcoming chemoresistance and remodeling pancreatic TME.