ST14 and squamous cell carcinoma: Humans express 17 TTSPs, which are divided into four different subfamilies: the (i) matriptase, (ii) hepsin/transmembrane protease, serine (TMPRSS), (iii) human airway trypsin-like (HAT)/differentially expressed in squamous cell carcinoma (DESC), and (iv) corin subfamilies28.