The presence of cell surface active matriptase was also reported in several matriptase-expressing human epithelial and carcinoma cells based on the detection of tryptic activity, followed by its inhibition using a matriptase single-chain antibody E2 for verification [24] and the direct detection of active matriptase on cell surfaces using the single-chain matriptase antibody A11 [25]. Here, ST14 is linked to carcinoma.