Protein S100-A4 (S100A4) (S100A4)

Protein S100-A4, also known as metastasin (Mts1) or fibroblast-specific protein 1 (FSP1), is a member of the S100 calcium-binding protein family characterized by its EF-hand motifs [2, 3]. It serves as a critical regulator of cell motility, invasion, and the epithelial-mesenchymal transition (EMT) by interacting with cytoskeletal components like non-muscle myosin IIA and tropomyosin [1, 6, 12]. Beyond its intracellular roles, secreted S100A4 acts as a cytokine-like signaling molecule, activating receptors such as TLR4 and RAGE to promote an inflammatory and pro-metastatic tumor microenvironment [5, 11]. Consequently, S100A4 is strongly associated with poor prognosis and metastatic progression in numerous cancers, including breast, colorectal, and pancreatic carcinomas [3, 13, 14]. It also plays a significant role in chronic fibrotic diseases of the liver, lung, and kidney by driving fibroblast activation and tissue remodeling [4, 5]. Therapeutic strategies currently under investigation include small molecule inhibitors like niclosamide that suppress its transcription, phenothiazines that induce its sequestration through oligomerization, and neutralizing monoclonal antibodies designed to block its extracellular activities [6, 10, 15].

Other names

MetastasinMts1Fibroblast-specific protein 1FSP1Calcium-binding protein A4CAPLPEL9818A242Ap9KaCalvasculin

Drugs targeting S100A4 function through several mechanisms: transcriptional inhibition of the S100A4 gene (e.g., niclosamide), induction of protein oligomerization to sequester the active form (e.g., phenothiazines), covalent modification of cysteine residues to disrupt protein-protein interactions with non-muscle myosin IIA or p53, and neutralization of extracellular S100A4 using monoclonal antibodies to block signaling through RAGE or TLR4 receptors [6, 7, 8, 10, 11].