Cathepsin W (CtsW), a cysteine protease, is involved in multiple biological processes. It is crucial for the escape of Influenza A Virus (IAV) from late endosomes, with its proteolytic activity required for the fusion of viral and endosomal membranes. Intracellular CtsW promotes viral entry [3,4]. It may also play a role in the regulation of inflammation, metabolism, autophagy, and apoptosis pathways, as indicated by studies on lumbar disc herniation [7]. Additionally, CtsW expression is associated with immune response and inflammation, with its expression increasing during aging in whole blood [8].

In pancreatic cancer, down-regulation of CtsW is associated with poor prognosis, suggesting its potential as a prognostic and diagnostic marker [1]. In papillary thyroid cancer, circular RNA_14580 interacts with CtsW, and this interaction is involved in tumorigenic processes, highlighting the role of CtsW in modulating the tumor microenvironment [2]. In cutaneous T-cell lymphomas, TCR-γδ+ MF and Berti lymphoma clones show increased expression of CtsW along with other cytotoxic markers [5]. In multiple myeloma, cytotoxic T cell clusters in patients have higher expression of CtsW as a senescence marker [6].

In conclusion, CtsW plays diverse and important roles in various biological processes and disease conditions. Its functions in viral entry, cancer prognosis, and immune-related responses are significant. Studies on CtsW using different models have enhanced our understanding of these roles, providing potential targets for antiviral and cancer therapies, as well as insights into immune-related diseases.