Serpin B3, also known as squamous cell carcinoma antigen-1 (SCCA-1), is a member of the serpin superfamily of serine protease inhibitors. Serpin B3 belongs to the subgroup ovalbumin-related serpins which are involved in the regulation of apoptosis, inflammation, angiogenesis and embryogenesis. It may act as a papain-like cysteine protease inhibitor to modulate the host immune response against tumor cells. It also functions as an inhibitor of UV-induced apoptosis via suppression of the activity of c-Jun NH(2)-terminal kinase (JNK1).