Padi1, short for peptidylarginine deiminase 1, catalyzes protein citrullination, which involves the conversion of protein-bound arginine residues into citrulline residues in a calcium-dependent manner [7]. This process has been linked to various biological functions, including immune response regulation, and is involved in pathways such as ERK1/2-p38, MAPK, and those related to glycolysis [1,3,5]. It is important in processes like early embryo development, keratinocyte differentiation, and maintaining the integrity of the environment-tissue barrier interface [6,7,8].

In pancreatic ductal adenocarcinoma (PAAD), knockdown of Padi1 in cell lines suppressed cell migration and invasion, suggesting it may act as an oncogene regulating metastasis in vitro by activating the ERK1/2-p38 signaling pathway [1]. In colorectal cancer, Padi1 was highly expressed, and a risk-prognosis score based on its co-expressed genes could predict prognosis and immunotherapy efficacy [2]. In nasopharyngeal carcinoma, lncRNA TINCR regulated the Padi1-MAPK-MMP2/9 pathway, promoting tumor progression and chemoresistance [3]. Also, Padi1 expression in oncolytic adenoviruses exhibited anti-tumor activity against melanoma in mouse models [4].

In summary, Padi1 plays crucial roles in multiple biological processes and disease conditions. Its study through functional knockdown in cell lines and in vivo mouse models has revealed its significance in cancer metastasis, prognosis prediction, and immunotherapy in various cancers, highlighting its potential as a therapeutic target in these disease areas.