Expression of prostasin and its inhibitors during colorectal cancer carcinogenesis

<p>Abstract</p> <p>Background</p> <p>Clinical trials where cancer patients were treated with protease inhibitors have suggested that the serine protease, prostasin, may act as a tumour suppressor. Prostasin is proteolytically activated by the serine protease, matriptase, which has a very high oncogenic potential. Prostasin is inhibited by protease nexin-1 (PN-1) and the two isoforms encoded by the mRNA splice variants of <it>hepatocyte growth factor activator inhibitor-1 </it>(<it>HAI-1</it>), <it>HAI-1A</it>, and <it>HAI-1B</it>.</p> <p>Methods</p> <p>Using quantitative RT-PCR, we have determined the mRNA levels for <it>prostasin </it>and <it>PN-1 </it>in colorectal cancer tissue (n = 116), severe dysplasia (n = 13), mild/moderate dysplasia (n = 93), and in normal tissue from the same individuals. In addition, corresponding tissues were examined from healthy volunteers (n = 23). A part of the cohort was further analysed for the mRNA levels of the two variants of HAI-1, here denoted <it>HAI-1A </it>and <it>HAI-1B</it>. mRNA levels were normalised to <it>β-actin</it>. Immunohistochemical analysis of prostasin and HAI-1 was performed on normal and cancer tissue.</p> <p>Results</p> <p>The mRNA level of prostasin was slightly but significantly decreased in both mild/moderate dysplasia (p < 0.001) and severe dysplasia (p < 0.01) and in carcinomas (p < 0.05) compared to normal tissue from the same individual. The mRNA level of <it>PN-1 </it>was more that two-fold elevated in colorectal cancer tissue as compared to healthy individuals (p < 0.001) and elevated in both mild/moderate dysplasia (p < 0.01), severe dysplasia (p < 0.05) and in colorectal cancer tissue (p < 0.001) as compared to normal tissue from the same individual. The mRNA levels of <it>HAI-1A </it>and <it>HAI-1B </it>mRNAs showed the same patterns of expression. Immunohistochemistry showed that prostasin is located mainly on the apical plasma membrane in normal colorectal tissue. A large variation was found in the degree of polarization of prostasin in colorectal cancer tissue.</p> <p>Conclusion</p> <p>These results show that the mRNA level of <it>PN-1 </it>is significantly elevated in colorectal cancer tissue. Future studies are required to clarify whether down-regulation of prostasin activity via up regulation of PN-1 is causing the malignant progression or if it is a consequence of it.</p

Hepatocyte growth factor activator inhibitor-1 has a complex subcellular itinerary.

International audienceHepatocyte growth factor activator inhibitor-1 (HAI-1) is a Kunitz-type transmembrane serine protease inhibitor that forms inhibitor complexes with the trypsin-like serine protease, matriptase. HAI-1 is essential for mouse placental development and embryo survival and together with matriptase it is a key regulator of carcinogenesis. HAI-1 is expressed in polarized epithelial cells, which have the plasma membrane divided by tight junctions into an apical and a basolateral domain. Here we show that HAI-1 at steady state is mainly located on the basolateral membrane of both Madin-Darby Canine Kidney cells and mammary gland epithelial cells. After biosynthesis HAI-1 is exocytosed mainly to the basolateral plasma membrane from where 15% of the HAI-1 molecules are proteolytically cleaved and released into the basolateral medium. The remaining membrane-associated HAI-1 is endocytosed and then recycles between the basolateral plasma membrane and endosomes for hours until it is trancytosed to the apical plasma membrane. Minor amounts of HAI-1 present at the apical plasma membrane are proteolytically cleaved and released into the apical medium. Full-length membrane-bound HAI-1 has a half life of 1.5 h and is eventually degraded in the lysosomes, whereas proteolytically released HAI-1 is more stable. HAI-1 is co-localized with its cognate protease, matriptase, at the basolateral plasma membrane. We suggest that HAI-1, in addition to its protease inhibitory function, play a role in transportingmatriptase from the basolateral plama membrane to the apical plasma membrane, as matriptase is known to interact with prostasin, located at the apical plasma membrane