Modulation of tissue-type plasminogen activator expression by platelet activating factor in human glioma cells.
OBJECTIVE
For tumor growth, proteolytic remodeling of the extracellular matrix (ECM) is a key factor. To determine proteolytic activity in human glioma cells, fibrinolytic activity, mRNA expression of fibrinolytic factors, and fibrinolytic inhibitors were studied in human glioma cell lines. The effect of platelet activating factor (PAF), a potent mediator of inflammatory and immune responses, on this fibrinolytic activity was also examined.


METHODS
The fibrinolytic activities of conditioned medium and cell lysates from human glioma cell lines, A172, T98G, U87 and TM1 were studied by fibrin plate zymography. mRNA expression of tissue plasminogen activator (tPA), urokinase-type plasminogen activator (uPA) and plasminogen activator inhibitors (PAI-1, PAI-2) was measured by Northern blot analysis. PAF was added to the medium, and its effects on cell proliferation, fibrinolytic activity, mRNA expression of plasminogens and inhibitors were studied.


RESULTS
mRNA expression of plasminogens and inhibitors differed between individual cell lines. Only the medium and cell lysates from A172 cells revealed fibrinolytic activity. A172 cells showed mRNA expression of tPA. PAF at low concentrations, such as 1 nM, stimulated A172 cell proliferation, and high concentrations of PAF inhibited proliferation. PAF stimulated tPA release into the conditioned medium. mRNA expression of tPA was stimulated by low concentrations of PAF and inhibited by high concentrations.


CONCLUSIONS
The variability of mRNA expression of plasminogen activators (PAs) between different glioma cell lines may indicate that plasminogens and their inhibitors do not directly correlate with brain tumor growth. PAF may be an important factor in the local control of fibrinolytic activity in glioma and its proliferation.
Akai
Takuya
T
Department of Neurosurgery, Faculty of Medicine, Toyama Medical and Pharmaceutical University, Japan. akai@kanazawa-med.ac.jp
Niiya
Kenji
K
Sakuragawa
Nobuo
N
Iizuka
Hideaki
H
Endo
Shunro
S
D015152:Blotting, Northern; D001932:Brain Neoplasms / Q000188:drug therapy / Q000235:genetics* / Q000378:metabolism; D002455:Cell Division; D017077:Culture Media, Conditioned; D004797:Enzyme-Linked Immunosorbent Assay; D005337:Fibrin / Q000737:chemistry; D005342:Fibrinolysis; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D005910:Glioma / Q000188:drug therapy / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D017395:Plasminogen Activator Inhibitor 1 / Q000235:genetics; D017396:Plasminogen Activator Inhibitor 2 / Q000235:genetics; D010972:Platelet Activating Factor / Q000494:pharmacology*; D012333:RNA, Messenger / Q000378:metabolism*; D010959:Tissue Plasminogen Activator / Q000235:genetics*; D014407:Tumor Cells, Cultured; D014568:Urokinase-Type Plasminogen Activator / Q000235:genetics*
D017077:Culture Media, Conditioned; D017395:Plasminogen Activator Inhibitor 1; D017396:Plasminogen Activator Inhibitor 2; D010972:Platelet Activating Factor; D012333:RNA, Messenger; D005337:Fibrin; D010959:Tissue Plasminogen Activator; D014568:Urokinase-Type Plasminogen Activator