Identification of a transforming growth factor beta-1 activator derived from a human gastric cancer cell line.
It has been shown that some types of tumour cells produce activated transforming growth factor beta-1 (TGF-beta 1). However, the mechanism for the activation of TGF-beta 1 derived from tumour cells has not been fully elucidated. The present study was undertaken to characterise an activator of latent TGF-beta 1 secreted from a human gastric cancer cell line, KATO-III. Western blot analyses using antibodies for TGF-beta 1, latency associated peptide (LAP) and latent TGF-beta 1-binding protein (LTBP) revealed that, in the cell lysate of KATO-III, TGF-beta 1 protein was expressed as a small latent complex of TGF-beta 1 and LAP. This was also confirmed by a gel chromatographic analysis of the cell lysate obtained from KATO-III. A 2.5 kb transcript of TGF-beta 1 mRNA was detected in KATO-III cells by Northern blot analysis. A gel chromatographic analysis of the conditioned medium from KATO-III cells revealed, in addition to the active form of TGF-beta 1, a factor which activated latent TGF-beta 1 from NRK-49F cells at fractions near a molecular size of 65,000. This factor was inactivated by heat (100 degrees C), acidification, trypsin and serine protease inhibitors. TGF-beta 1 activity in KATO-III cell lysate was not detected in the untreated state, but potent TGF-beta 1 activity was detected after acid treatment. These results suggest that KATO-III releases not only a latent TGF-beta 1 complex but also a type of serine protease, different from plasmin, plasminogen activator, cathepsin D, endoglycosidase F or sialidase, which activates the latent TGF-beta 1 complex as effectively as acid treatment.
Horimoto
M
M
Fourth Department of Internal Medicine, Sapporo Medical University School of Medicine, Japan.
Kato
J
J
Takimoto
R
R
Terui
T
T
Mogi
Y
Y
Niitsu
Y
Y
D015152:Blotting, Northern; D015153:Blotting, Western; D002352:Carrier Proteins / Q000032:analysis; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D002845:Chromatography; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D053779:Latent TGF-beta Binding Proteins; D010446:Peptide Fragments; D011498:Protein Precursors; D011506:Proteins / Q000032:analysis; D012697:Serine Endopeptidases / Q000032:analysis* / Q000378:metabolism; D015842:Serine Proteinase Inhibitors / Q000494:pharmacology; D013274:Stomach Neoplasms / Q000737:chemistry* / Q000201:enzymology / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000032:analysis / Q000378:metabolism*; D053773:Transforming Growth Factor beta1; D014407:Tumor Cells, Cultured
D002352:Carrier Proteins; D047908:Intracellular Signaling Peptides and Proteins; D053779:Latent TGF-beta Binding Proteins; D010446:Peptide Fragments; D011498:Protein Precursors; D011506:Proteins; D015842:Serine Proteinase Inhibitors; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; D012697:Serine Endopeptidases