To investigate the expression pattern of SPP1 in pancreatic cancer and its role in the tumor immune microenvironment, with functional validation by in vivo and in vitro experiments.

Bioinformatics analyses were performed using TCGA and CCLE databases to assess SPP1 expression, prognostic value, and immune correlations in pan-cancer and pancreatic cancer. Single-cell transcriptomic and CellChat analyses were used to explore cell communication and immune microenvironment characteristics. An orthotopic pancreatic cancer mouse model was established, and in vivo and in vitro experiments including flow cytometry, Western blot, co-immunoprecipitation (Co-IP), and in vivo ubiquitination assays were conducted to validate the immunoregulatory role of tumor-derived SPP1.

SPP1 was highly expressed in pancreatic cancer and associated with poor prognosis, elevated immunosuppressive microenvironment scores, and increased M2 macrophage infiltration. Single-cell and cell communication analyses indicated that SPP1 was mainly derived from macrophages and ductal epithelial cells, contributing to immune-regulatory signaling. Functional experiments confirmed that SPP1 promoted M2 macrophage polarization, enhanced immunosuppressive cytokine expression, and facilitated tumor progression through immune microenvironment remodeling.

SPP1 plays a critical role in regulating macrophage polarization and shaping an immunosuppressive tumor microenvironment in pancreatic cancer, suggesting its potential as a therapeutic target.