Secretion of Protease Nexin-II/Amyloid β Protein Precursor by Human Colorectal Carcinoma Cells and Its Modulation by Cytokines/Growth Factors and Proteinase Inhibitors

Abstract

Trypsin inhibitors secreted by human colorectal adenocarcinoma cell lines were analyzed by reverse zymography. Among eleven cell lines analyzed, the major inhibitor secreted was protease nexin-II (PN-II), a secreted form of amyloid beta protein precursor (APP) containing a Kunitz-type serine proteinase inhibitor domain. Expression of the APP gene was also confirmed in the cell lines and the main APP mRNA species were PN-II types. The APP gene expression was constant during cell growth in vitro. On the other hand, the rate of extracellular PN-II accumulation markedly increased after long-term serum-free maintenance of the confluent culture. The extracellular accumulation of PN-II was also strongly stimulated either by interleukin-1beta (IL-1beta) treatment or to a lesser extent by basic fibroblast growth factor, tumor necrosis factor-alpha, hepatocyte growth factor or epidermal growth factor. Neither serum depletion- nor IL-1beta-induced stimulation of extracellular PN-II accumulation were accompanied by obvious alteration of the levels of APP mRNA and cellular APP holoprotein, suggesting that the enhanced extracellular accumulation of PN-II might result from up-regulation of the secretory pathway of APP. The IL-1beta-induced PN-II secretion was significantly inhibited by relatively high concentrations (50-200 microg/ml) of aprotinin, a serine proteinase inhibitor, in a dose-dependent manner without obvious cell-toxic effects.

Hepatocyte Growth Factor Activator Inhibitor Type 1 Is a Specific Cell Surface Binding Protein of Hepatocyte Growth Factor Activator (HGFA) and Regulates HGFA Activity in the Pericellular Microenvironment

“…Like APP (39,40), the shedding of membrane-form HAI-1 and the HGFA⅐HAI-1 complex were also significantly enhanced by an inflammatory cytokine, IL-1␤. This finding may have an important implication for the understanding of HAI-1's role in FIG.…”

Amyloid β protein precursor is involved in the growth of human colon carcinoma cellin vitro andin vivo

“…The cells were plated in 96-well plates as above, and the level of DNA synthesis was measured by [ 3 H]-thymidine incorporation assay 15 min after the EGF treatment. [3][4][5] Here, we demonstrated that down-regulation of APP in SW837 human colon carcinoma cells resulted in markedly reduced cellular growth in vitro, and more importantly, also in vivo. *p Ͻ 0.05 compared with mock clones.…”

“…5 Since the original SW837 cell line may consist of heterogenous subpopulations, a cloned subline of SW837 was obtained as a parent cell for the following transfection study in order to minimize cloning artifacts. 5 Since the original SW837 cell line may consist of heterogenous subpopulations, a cloned subline of SW837 was obtained as a parent cell for the following transfection study in order to minimize cloning artifacts.…”

“…1 However, its biological functions are largely unknown, particularly in non-neural tissues. 5 This evidence suggests that APP and/or sAPP may have important, though undefined, biological functions in tumor cells, including colon carcinoma cells. 3,4 Indeed, sAPP represented the major trypsin inhibitor produced by a panel of colon carcinoma cell lines.…”

“…Since all tumor cell lines so far examined express APP mRNA 4 and most colon carcinoma cell lines secrete sAPP with Kunitz-type serine proteinase inhibitor domain as their main cellular serine proteinase inhibitor, 5 it can be hypothesized that APP and/or sAPP may also have a fundamental important function(s) in tumor cells, perhaps being involved in cellular growth, differentiation and tumorigenesis. In an attempt to test this hypothesis, we used the antisense RNA strategy to impair the expression of APP in human colon carcinoma cell line SW837.…”