Biphasic calcium response of platelet-derived growth factor stimulated glioblastoma cells is a function of cell confluence

Authors

  • György Vereb,

    Corresponding author
    1. Department of Biophysics and Cell Biology, Research Center for Molecular Medicine, University of Debrecen, Debrecen, Hungary
    • Department of Biophysics and Cell Biology, Medical and Health Science Center, University of Debrecen, Nagyerdei krt. 98, H-4012 Debrecen, Hungary
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  • Burt G. Feuerstein,

    1. Departments of Lab Medicine and Neurosurgery, and Brain Tumor Research Center, University of California, San Francisco, California
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  • William C. Hyun,

    1. Laboratory for Cell Analysis, Department of Laboratory Medicine, University of California, San Francisco, California
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  • Mack J. Fulwyler,

    1. Laboratory for Cell Analysis, Department of Laboratory Medicine, University of California, San Francisco, California
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  • Margit Balázs,

    1. Department of Preventive Medicine, Medical and Health Science Center, University of Debrecen, Debrecen, Hungary
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  • János Szöllősi

    1. Department of Biophysics and Cell Biology, Research Center for Molecular Medicine, University of Debrecen, Debrecen, Hungary
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Abstract

Background

Previous reports have linked the spiking or two-phased character of calcium transients evoked by platelet-derived growth factor (PDGF) to the position of cells in the cell cycle without regard to cell–cell contact and communication. Because cell confluence can regulate growth factor receptor expression and dephosphorylation, we investigated the effect of cell culture confluence and cell cycle on calcium responses of PDGF-BB–stimulated A172 glioblastoma cells.

Methods

Digital imaging cytometry was used to correlate the peak and duration of calcium response with bromodeoxyuridine positivity and DNA content and with culture confluence on a cell-by-cell basis.

Results

In serum-starved cultures, complete two-phase calcium signals and shorter, lower spikes occurred independent of cell cycle phase. However, the confluence of cell culture seemed essential for inducing a complete response because cells in sparse cultures exhibited mostly short spikes with lower peaks or no transients at all.

Conclusion

Because cell confluence, by virtue of cell–cell contacts, is assumed to be an important regulator of proliferation, one is tempted to speculate that in transformed cells the ability to produce stronger growth signals upon reaching confluence and facing contact inhibition could provide a proliferative advantage. © 2005 International Society for Analytical Cytology

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