Activation of hepatocyte growth factor/scatter factor in colorectal carcinoma.
Activation of hepatocyte growth factor/scatter factor (HGF/SF) in the extracellular milieu is a critical limiting step in the HGF/SF-induced signaling pathway mediated by Met receptor tyrosine kinase, which has potentially important roles in tumor biology and progression. However, little is known concerning the regulation of HGF/SF activation in tumors. Immunoblot analysis revealed that the activation of HGF/SF was enhanced significantly in colorectal carcinoma tissues compared with the corresponding normal mucosa. Serum-free conditioned media of cultured human colorectal carcinoma cell lines contained HGF/SF-activating activity, and the addition of a single-chain precursor form of HGF/SF to the serum-free culture of these cells resulted in HGF/SF-dependent modulation of cellular phenotypes, such as increased scattering and enhanced secretion of vascular endothelial growth factor. This processing activity was enhanced by thrombin treatment but was inhibited significantly by a neutralizing antibody against HGF activator (HGFA), a factor XIIa-like serine proteinase believed to be expressed mainly in the liver. The activity was also inhibited by recombinant HGFA inhibitor type 1 (HAI-1). The presence of HGFA mRNA and secretion of HGFA protein were confirmed in the cell lines. Therefore, extrahepatic expression of HGFA in the colorectal carcinoma cells could be responsible for the single-chain HGF/SF-processing activity of the cells. We examined the expression of HGFA and HAI-1 in human colorectal mucosa and adenoma-carcinoma sequence. Immunohistochemically, HGFA was stained weakly in the normal enterocytes, and immunoreactivity was increased modestly in the neoplastic differentiation. The subcellular localization of HGFA immunoreactivity was altered in carcinoma cells showing basal or cell-stroma interface staining patterns, compared with normal and adenoma cells with a supranuclear or apical staining pattern. In contrast to HGFA, the expression of HAI-1 decreased significantly in carcinoma cells relative to the adjacent normal or adenoma cells, indicating that the net balance between HGFA and HAI-1 shifts in favor of HGFA in carcinomas. In fact, pro-HGFA and the active form of HGFA proteins increased in carcinoma tissue compared with the corresponding normal mucosa. It was concluded that HGFA is expressed in colorectal mucosa and tumors and could be involved in the activation of HGF/SF in colorectal carcinomas. Therefore, the balance between HGFA and HAI-1 could play an important role in the regulation of HGF/SF activity in colorectal carcinomas.
Kataoka
H
H
The Second Department of Pathology, Miyazaki Medical College, Kiyotake, Japan. mejina@post.miyazaki-med.ac.jp
Hamasuna
R
R
Itoh
H
H
Kitamura
N
N
Koono
M
M
D000230:Adenocarcinoma / Q000378:metabolism / Q000473:pathology; D000236:Adenoma / Q000378:metabolism / Q000473:pathology; D000818:Animals; D003106:Colon / Q000378:metabolism; D015179:Colorectal Neoplasms / Q000378:metabolism* / Q000473:pathology; D016895:Culture Media, Serum-Free; D018450:Disease Progression; D016228:Endothelial Growth Factors / Q000378:metabolism; D017228:Hepatocyte Growth Factor / Q000096:biosynthesis / Q000502:physiology*; D006801:Humans; D007150:Immunohistochemistry; D007413:Intestinal Mucosa / Q000378:metabolism; D008222:Lymphokines / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000096:biosynthesis / Q000235:genetics; D051379:Mice; D008807:Mice, Inbred BALB C; D053491:Proteinase Inhibitory Proteins, Secretory; D019859:Proto-Oncogene Proteins c-met / Q000096:biosynthesis / Q000235:genetics; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D012697:Serine Endopeptidases / Q000096:biosynthesis / Q000235:genetics; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors
D016895:Culture Media, Serum-Free; D016228:Endothelial Growth Factors; D008222:Lymphokines; D008562:Membrane Glycoproteins; D053491:Proteinase Inhibitory Proteins, Secretory; D012333:RNA, Messenger; C109149:SPINT1 protein, human; C504591:Spint1 protein, mouse; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors; D017228:Hepatocyte Growth Factor; D019859:Proto-Oncogene Proteins c-met; C081092:HGF activator; D012697:Serine Endopeptidases