Serpin family B member 4 (SERPINB4)

Serpin family B member 4 (SERPINB4) is an intracellular serine/cysteine protease inhibitor, classified within the clade B (ovalbumin-like) serpin family. It functions primarily to inhibit chymotrypsin-like serine proteases such as chymase and cathepsin G by a suicide inactivation mechanism, forming irreversible covalent complexes with its targets. SERPINB4 is frequently upregulated in tumors (notably squamous cell carcinoma), modulating processes related to cell survival, immune evasion, epithelial-mesenchymal transition, and therapy resistance. In addition to its role as a biomarker for epithelial cancers, aberrant expression of SERPINB4 associates with chronic inflammatory states and autoimmunity, making it both a subject of therapeutic interest and a potential challenge due to its pro-tumorigenic and immunoregulatory functions[1][2][3].

Other names

Serpin B4PI11SCCA2SCCA-2LeupinPeptidase inhibitor 11Squamous cell carcinoma antigen 2SCCA1 (sometimes co-referenced due to similarity)serpin peptidase inhibitor clade B member 4LEUPIN

Irreversibly inhibits target proteases by forming covalent complexes (suicide inhibition mechanism), blocking enzymatic activity and modulating downstream cellular responses. It also contributes to immune evasion by inhibiting immune cell proteases such as granzyme M, thereby suppressing immune-mediated clearance of tumor cells.