PAD2-Mediated Histone Citrullination Drives Tumor Progression by Enhancing Cell Proliferation and Modifying the Microenvironment in Pancreatic Cancer

Histone citrullination is catalyzed by peptidyl arginine deiminases (PAD) that play a role in gene regulation. However, the clinical significance and molecular mechanisms of histone citrullination and PADs in pancreatic ductal adenocarcinoma (PDAC) remain unclear. This study aimed to investigate the role and potential molecular mechanisms of PADs in PDAC. Histone citrullination was upregulated and strongly associated with PAD2 nuclear expression in human PDAC samples. PAD2 nuclear expression correlated with aggressive tumor characteristics and poor prognosis. PAD2 overexpression increased PDAC cell proliferation, whereas its knockdown had the opposite effect in vitro. PAD2 bound to the promoter regions of PRUNE1 and E2F1, resulting in the activation of their mRNA expression via upregulation of histone citrullination and chromatin accessibility at their promoter regions. PAD2 overexpression enhanced tumorigenicity, and increased PRUNE1 expression and M2 tumor-associated macrophage (M2 TAM) infiltration in subcutaneous and orthotopic PDAC models. In vitro assay showed that macrophages cultured in a conditioned medium from PAD2-expressing PDAC cells exhibited an increase of M2 TAM-related markers in a PRUNE1-dependent manner. Treatment with the PAD2 inhibitors Cl-amidine and AFM-30a selectively impaired the growth and tumorigenicity of PAD2-expressing PDAC cells in vitro and in vivo. Furthermore, the triple-high expression of nuclear PAD2, PRUNE1, and the M2 TAM marker CD206 may serve as independent adverse prognostic factors for human PDAC. Conclusively, PAD2-mediated histone citrullination drives PDAC progression by epigenetically regulating downstream target genes and influencing the tumor microenvironment. The PAD2-PRUNE1-M2 TAM axis may be a promising therapeutic target and prognostic indicator for PDAC.