Suppression of tumorigenicity 14 (ST14) is a human gene that codes for a protein, commonly called matriptase. Matriptase expression has been associated with several types of tumors and cancers, such as those of the breast, prostate, ovaries, and colon. Thus, this gene has been proposed to play a role in cancer invasion and metastasis. Matriptase also plays an important role in the terminal differentiation of the oral epithelium and epidermis, as well as hair follicular growth. This function is carried out by the protein's role in activation of profilaggrin and corneocyte maturation. Mutations in ST14 are, thus, also known to cause skin disorders. Autosomal recessive ichthyosis with hypotrichosis (ARIH) is a rare genetic disease known to be caused by mutations in the ST14 gene. Patients affected with this condition show abnormal degradation of corneodesmosmes in the upper layers of the stratum corneum, suggesting a role of matriptase in epidermal desquamation, possibly via impaired proteolytic degradation of corneodesmosomal proteins. Similarly, congenital ichthyosis, follicular atrophoderma, hypotrichosis, and hypohidrosis (IFAH) is another rare autosomal recessive disorder caused by mutations in the ST14 gene.

ST14 is located on the long arm of chromosome 11, where it spans a length of about 50 kb. The matriptase protein that this gene codes for is a type II transmembrane serine protease made up of 855 amino acids and weighs about 95 kDa. The protein is expressed specifically in terminally differentiating keratinocytes, and in matrix, precortex, and cortex cells, and shaft of the anagen hair, where it exists as a cell surface glycoprotein. Activation of the enzyme is a complex process, and requires at least two cleavage processes, as well as a temporary association with hepatocyte growth factor activator inhibitor (HAI)-1.

Matriptase has been shown to exhibit trypsin-like activity as defined by cleavage of synthetic substrates with Arg or Lys as the P1 site. One of the functions of matriptase, however, is the activation of hepatocyte growth factor, and urokinase plasminogen activator, thus acting as an activator for epithelial growth factors. This pathway could explain the role of ST14 over-expression in cancer and metastasis.