title: Plasmin: its role in the extracellular processing of progalanin in tumor tissue.
abstract: Galanin is a neuropeptide that is widely distributed in the central and peripheral nervous systems. In a previous study, we showed that a small cell lung carcinoma (SCLC) cell line, SBC-3A, released progalanin but not galanin, and that progalanin was then converted to galanin(1-20), the active form. Because the galanin(1-20) had undergone hydrolysis at Arg and Lys residues, the protease concerned was surmised to have a trypsin-like activity. The present study was performed to identify the trypsin-like protease which had previously been found to activate progalanin in this tumor tissue. The protease was isolated using chromatography and electrophoresis, and identified in tumor extracts from SBC-3A tumor-bearing mice; the major protease was found to be plasmin. We next confirmed that extracellular processing of progalanin occurs in SCLC tumor tissue (tumors produced by the implantation of SBC-3A cells into mice), and in two types of breast tumor tissue (obtained by implantation into mice of BT-549 and MDA-MB-436 cells). In cell culture, processed forms of progalanin were undetectable in SBC-3A, BT-549 or MDA-MB-436 cells. Conversely, gel filtration chromatography analysis of tumor extracts from SBC-3A, BT-549 and MDA-MB-436-bearing mice, revealed that galanin-like immunoreactivity (galanin-LI) in these tumor extracts was due to the presence of progalanin (14 kDa) and galanin(1-20) (2 kDa). Moreover, trypsin-like protease activity was elevated, and plasmin was expressed abundantly in SBC-3A, BT-549 and MDA-MB-436 tumors in mice. In addition, tranexamic acid, a plasmin inhibitor, inhibited progalanin conversion to galanin(1-20). The present study revealed that plasmin was present in tumor tissue, and that it was responsible for processing progalanin to galanin(1-20) in the extracellular environment.
authors.affiliation: Laboratory of Bioorganic Chemistry, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Shizuoka 422-8526, Japan. yamahiro@u-shizuoka-ken.ac.jp
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Yamamoto
authors.forename: Shinta
authors.initials: S
authors.lastname: Ben
authors.forename: Shun
authors.initials: S
authors.lastname: Saitoh
authors.forename: Kengo
authors.initials: K
authors.lastname: Kamata
authors.forename: Kazuaki
authors.initials: K
authors.lastname: Iguchi
authors.forename: Minoru
authors.initials: M
authors.lastname: Hoshino
mesh_terms: D000818:Animals; D015153:Blotting, Western; D045744:Cell Line, Tumor; D015180:Electrophoresis, Gel, Two-Dimensional; D005341:Fibrinolysin / Q000235:genetics / Q000378:metabolism*; D019004:Galanin / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008175:Lung Neoplasms / Q000235:genetics / Q000378:metabolism; D051379:Mice; D011863:Radioimmunoassay; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012697:Serine Endopeptidases / Q000235:genetics / Q000378:metabolism; D055752:Small Cell Lung Carcinoma / Q000235:genetics / Q000378:metabolism
chemical_list: C114880:trypsin-like serine protease; D019004:Galanin; D012697:Serine Endopeptidases; D005341:Fibrinolysin