
<ArticleTitle>Down-regulation of <prot>prostasin</prot> serine protease: a potential invasion suppressor in prostate cancer.</ArticleTitle>
<AbstractText>BACKGROUND: <prot>Prostasin</prot> is a serine protease predominantly expressed in normal prostate epithelial cells. The biological function of <prot>prostasin</prot> has not been determined. METHODS: Western blot and RT-PCR analyses were used to examine the expression of <prot>prostasin</prot> in prostate cancer cell lines. Immunohistochemistry was used to evaluate <prot>prostasin</prot> protein expression in human prostate cancer. An in vitro Matrigel invasion assay was used to test the invasiveness of prostate cancer cell lines forced to express recombinant <prot>prostasin</prot>. RESULTS: Both <prot>prostasin</prot> protein and mRNA were found to be expressed in normal human prostate epithelial cells and a non-invasive human prostate cancer cell line, the LNCaP, but neither was found in invasive human prostate cancer cell lines DU-145 and PC-3. <prot>Prostasin</prot> mRNA expression was absent in invasive prostate cancer cell lines of a transgenic mouse model. Immunohistochemistry analysis showed that <prot>prostasin</prot> protein expression is down-regulated in high-grade prostate cancer. Transfection of DU-145 and PC-3 cells with a full-length human <prot>prostasin</prot> cDNA restored <prot>prostasin</prot> expression and reduced the in vitro invasiveness by 68 and 42%, respectively. CONCLUSIONS: Our data indicate that <prot>prostasin</prot> may be implicated in normal prostate biology and is able to suppress prostate cancer invasion in vitro.</AbstractText>
