Objective Methods ·The Cancer Genome Atlas (TCGA) and Genotype-Tissue Expression (GTEx) database and the GSE15471 dataset in Gene Expression Omnibus (GEO) database were used to analyze the SNX1 mRNA expression in PDAC and normal pancreas tissues. Immunohistochemistry staining (IHC) was used to detect the SNX1 expression in PDAC and para-carcinoma tissues. The mRNA and protein levels of SNX1 in hTERT-HPNE cells and PDAC cells were detected by quantitative real-time PCR (qPCR) and Western blotting. CCK8 method, plate clonal formation experiment, cell scratch assays and flow cytometry (FCM) were used to detect changes of the proliferation, migration and apoptosis levels in AsPC-1 and Capan-1 cells caused by transfection siRNAs. Capan-1 cell line with stable knockdown of SNX1 was constructed, and the subcutaneous tumorigenesis experiment in nude mice was performed to detect the effect of SNX1 knockdown on the proliferation capacity of cells in nude mice. Immunofluorescence (IF) was used to determine the distribution of SNX1 in PDAC cells, and TMR-dextran was used to detect the changes of macropinocytosis levels of AsPC-1 and Capan-1 cells induced bytransfection siRNAs. Gene Set Enrichment Analysis (GSEA) was performed to predict SNX1 related signaling pathways. The transforming growth factor-β (TGF-β) signaling pathway was selected for subsequent analysis and experimental verification. Capan-1 and AsPC-1 cell lines with stable overexpression of SNX1 were constructed and treated with TGF-β signaling pathway inhibitor Oxymatrine (Oxy). CCK8 method, plate clonal formation experiment, cell scratch assays, FCM and TMR-dextran were used to detect the effects of Oxy treatment on the changes of the proliferation, migration, apoptosis and macropinocytosis levels of the cells caused by SNX1 overexpression. Results ·The results of combined analysis of TCGA and GTEx databases showed that the expression of SNX1 mRNA in PDAC tissues was higher than that in normal pancreas tissues, and the results of GSE15471 dataset analysis showed that the expression of SNX1 mRNA in PDAC tissues was higher than that in para-carcinoma tissues (both P=0.000). IHC results showed that the expression of SNX1 in cancer tissues of PDAC patients was also higher than that in para-carcinoma tissues. qPCR and Western blotting results showed that compared with hTERT-HPNE cells, the mRNA and protein levels of SNX1 in PDAC cells were up-regulated (all P<0.05). SNX1 knockdown could inhibit the proliferation and migration capacity of PDAC cells, down-regulate the macropinocytosis levels of PDAC cells, and promote their apoptosis. On the contrary, SNX1 overexpression led to opposite phenotype. Meanwhile, SNX1 knockdown could inhibit the proliferation capacity of Capan-1 cells in nude mice. IF results showed that SNX1 was colocalized with lysosomes in PDAC cells. GSEA analysis demonstrated that SNX1 expression was correlated with apoptosis, tricarboxylic acid cycle, TGF-β and phosphoinositide 3-kinase-serine/threonine-protein kinase-mammalian target of rapamycin signaling pathway. SNX1 knockdown in PDAC cells could inhibit the activation of TGF-β signaling pathway, SNX1 overexpression could promote this pathway, and TGF-β signaling pathway inhibitor Oxy could inhibit the phenotypic changes caused by SNX1 overexpression. Conclusion SNX1 is highly expressed in PDAC cells and tissues. SNX1 promotes the proliferation, migration capacity and macropinocytosis levels, and inhibits cell apoptosis by activating the TGF-β signaling pathway in PDAC cells. · ·To explore the expression changes of sorting nexin 1 (SNX1) in the occurrence and development of pancreatic ductal adenocarcinoma (PDAC) and its effect on the proliferation, migration, apoptosis and micropinocytosis of PDAC cells, and analyze its molecular mechanism to promote the progression of PDAC.