Squamous cell carcinoma antigen (SCCA)

**Squamous cell carcinoma antigen (SCCA)** is a cytoplasmic serine protease inhibitor first isolated from squamous cell carcinoma of the uterine cervix[3][1][4]. The term encompasses two closely related molecules, SCCA1 (SERPINB3) and SCCA2 (SERPINB4), which are coded by two adjacent genes on chromosome 18q21.3[3][1]. SCCA1 primarily inhibits cysteine proteases, while SCCA2 inhibits serine proteases[3][2]. SCCA suppresses apoptosis, promotes cell migration and invasion by influencing E-cadherin and β-catenin pathways, and modulates both tumor cell behavior and the immune microenvironment[3][1][2]. Serum SCCA is widely used as a tumor marker for squamous cell cancers for diagnostic and prognostic purposes; however, it is not directly targeted by any approved therapeutic drugs[3][1]. The molecule "Squamous cell carcinoma antigen" refers to two highly homologous serpin proteins—SCCA1 (SERPINB3) and SCCA2 (SERPINB4)—and "SCCA" is accepted as the canonical abbreviation[3][2][1]. SART3 ("Squamous cell carcinoma antigen recognized by T-cells 3") is a different gene/protein and should not be confused with SCCA[5]. SCCA is *not* a receptor, enzyme, transporter, or conventional "druggable" target but is an intracellular serpin used as a tumor biomarker and, to a lesser degree, a participant in tumor pathobiology rather than being directly modulated therapeutically.

Other names

SCCA1SCCA2Serpin B3Serpin B4SERPINB3SERPINB4

Not directly targeted pharmacologically; mechanisms involve serpin-mediated inhibition of proteases and modulation of apoptosis and EMT pathways