Expression of prostasin and its inhibitors during colorectal cancer carcinogenesis.
BACKGROUND
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 hepatocyte growth factor activator inhibitor-1 (HAI-1), HAI-1A, and HAI-1B.


METHODS
Using quantitative RT-PCR, we have determined the mRNA levels for prostasin and PN-1 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 HAI-1A and HAI-1B. mRNA levels were normalised to beta-actin. Immunohistochemical analysis of prostasin and HAI-1 was performed on normal and cancer tissue.


RESULTS
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 PN-1 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 HAI-1A and HAI-1B 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.


CONCLUSIONS
These results show that the mRNA level of PN-1 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.
Selzer-Plon
Joanna
J
Department of Cellular and Molecular Medicine, Faculty of Health Science, University of Copenhagen, Denmark. selzer@sund.ku.dk
Bornholdt
Jette
J
Friis
Stine
S
Bisgaard
Hanne C
HC
Lothe
Inger Mb
IM
Tveit
Kjell M
KM
Kure
Elin H
EH
Vogel
Ulla
U
Vogel
Lotte K
LK
D000368:Aged; D017398:Alternative Splicing; D016564:Amyloid beta-Protein Precursor / Q000096:biosynthesis; D002277:Carcinoma / Q000378:metabolism*; D015331:Cohort Studies; D015179:Colorectal Neoplasms / Q000378:metabolism*; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008297:Male; D008875:Middle Aged; D058255:Protease Nexins; D020033:Protein Isoforms; D053491:Proteinase Inhibitory Proteins, Secretory / Q000096:biosynthesis; D012333:RNA, Messenger / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000096:biosynthesis; D012697:Serine Endopeptidases / Q000096:biosynthesis*; D058258:Serpin E2; D000099271:Prostasin
D016564:Amyloid beta-Protein Precursor; D058255:Protease Nexins; D020033:Protein Isoforms; D053491:Proteinase Inhibitory Proteins, Secretory; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; D012697:Serine Endopeptidases; D058258:Serpin E2; D000099271:Prostasin; C545486:SERPINE2 protein, human; C109149:SPINT1 protein, human