Similarly, although HAI-2 has been identified as a relevant matriptase inhibitor in breast cancer cells, and prostasin inhibitor in human enterocytes and colon carcinoma cells, HAI-2 does not appear to be an important protease inhibitor for matriptase or prostasin in human skin, in which the tissue distribution and subcellular localization of HAI-2 suggests that HAI-2 has limited access to active matriptase or prostasin. Here, SPINT1 is linked to breast cancer.