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Autocrine growth stimulation of human meningioma cells by platelet-derived growth factor
T Todo1, E F Adams, R Fahlbusch
1Department of Neurosurgery, University of Tokyo, Japan.
Abstract:
The authors have previously shown that meningioma-derived conditioned medium profoundly stimulates the in vitro proliferation of meningioma cells. In this paper, self mitogenic agents found in the conditioned medium-autocrine growth-stimulatory factors actually secreted by human meningioma cells-are characterized as proteins related to the B chain of platelet-derived growth factor (PDGF) and possibly to the A chain of PDGF as well. The addition to conditioned medium of a neutralizing antibody against PDGF-BB caused a significant inhibition of the conditioned medium-stimulated DNA synthesis in all three meningioma cultures studied. A similar neutralizing effect was observed with an anti-PDGF-AA antibody in one meningioma culture studied. Gel filtration chromatography of concentrated conditioned medium from two different meningiomas using a Sephadex G-100 column revealed similar profiles from both conditioned media with a major peak of mitogenic activity against meningioma cells at a molecular weight (M(r)) of approximately 32 to 36 kD, accompanied by a minor peak at approximately 22 kD. The major peak mitogenic activity was significantly reduced by addition of an anti-PDGF-BB antibody. Western blot analysis of protein extracts from five meningioma specimens was performed using a monoclonal antibody against the B chain of PGDF, and a major band of PDGF-B immunoreactivity was detected at an M(r) of approximately 19 kD in all five meningiomas under both reducing and nonreducing conditions. Exogenous human and porcine PDGFs both exhibited a significant dose-dependent stimulation of DNA synthesis in two of three and three of five meningioma cultures examined, respectively. Although not all meningiomas investigated proved to share the biological activity associated with PDGF and these results may be preliminary, it seems that the autocrine growth-stimulatory loop established by PDGF-B-related molecules plays an important functional role in meningioma cell proliferation.
Insights
Human meningioma cells secrete platelet-derived growth factor (PDGF)-related proteins that stimulate their own growth. Neutralizing PDGF-BB inhibited DNA synthesis, suggesting an autocrine growth loop in meningiomas.
Area of Science:
- Oncology
- Cell Biology
- Molecular Biology
Background:
- Meningioma cells exhibit increased proliferation stimulated by conditioned medium.
- Autocrine growth factors secreted by tumor cells can drive tumor progression.
Purpose of the Study:
- To characterize the autocrine growth-stimulatory factors secreted by human meningioma cells.
- To investigate the role of platelet-derived growth factor (PDGF) in meningioma cell proliferation.
Main Methods:
- Conditioned medium from meningioma cultures was analyzed for mitogenic activity.
- Neutralizing antibodies against PDGF-BB and PDGF-AA were used to inhibit DNA synthesis.
- Gel filtration chromatography and Western blot analysis were performed to identify PDGF-related proteins.
- Exogenous PDGFs were added to meningioma cultures to assess their effect on DNA synthesis.
Main Results:
- Conditioned medium contained proteins related to PDGF B-chain and possibly A-chain.
- Neutralizing antibodies against PDGF-BB significantly inhibited DNA synthesis in meningioma cells.
- Gel filtration revealed major mitogenic activity at 32-36 kD, reduced by anti-PDGF-BB.
- Western blot detected PDGF-B immunoreactivity in all five meningioma specimens.
- Exogenous PDGFs dose-dependently stimulated DNA synthesis in some meningioma cultures.
Conclusions:
- PDGF-B-related molecules are secreted by meningioma cells and contribute to an autocrine growth-stimulatory loop.
- This autocrine loop plays a significant role in meningioma cell proliferation.
- Targeting PDGF signaling may offer a therapeutic strategy for meningiomas.